W. Lustermann

The First G-APD Cherenkov Telescope (FACT) is designed to detect cosmic gamma-rays with energies from several hundred GeV up to about 10 TeV using the Imaging Atmospheric Cherenkov Technique. In contrast to former or existing telescopes, the camera of the FACT telescope is comprised of solid-state Geiger-mode Avalanche Photodiodes (G-APD) instead of photomultiplier tubes for photo detection. It is the first full-scale device of its kind employing this new technology. The telescope is operated at the Observatorio del Roque de los Muchachos (La Palma, Canary Islands, Spain) since fall 2011. This paper describes in detail the design, construction and operation of the system, including hardware and software aspects. Technical experiences gained after one year of operation are discussed and conclusions with regard to future projects are drawn.

The First G-APD Cherenkov Telescope (FACT) is the first in-operation test of the performance of silicon photo detectors in Cherenkov Astronomy. For more than two years it is operated on La Palma, Canary Islands (Spain), for the purpose of long-term monitoring of astrophysical sources. For this, the performance of the photo detectors is crucial and therefore has been studied in great detail. Special care has been taken for their temperature and voltage dependence implementing a correction method to keep their properties stable. Several measurements have been carried out to monitor the performance. The measurements and their results are shown, demonstrating the stability of the gain below the percent level. The resulting stability of the whole system is discussed, nicely demonstrating that silicon photo detectors are perfectly suited for the usage in Cherenkov telescopes, especially for long-term monitoring purpose.

The forward-backward muon detector of the L3 experiment is presented. Intended to be used for LEP 200 physics, it consists of 96 self-calibrating drift chambers of a new design enclosing the magnet pole pieces of the L3 solenoid. The pole pieces are toroidally magnetized to form two independent analyzing spectrometers. A novel trigger is provided by resistive plate counters attached to the drift chambers. Details about the design, construction and performance of the whole system are given together with results obtained during the 1995 running at LEP.

Axial PET is a novel geometrical concept for Positron Emission Tomography (PET), based on layers of long scintillating crystals axially aligned with the bore axis. The axial coordinate is obtained from arrays of wavelength shifting (WLS) plastic strips placed orthogonally to the crystals. This article describes the design, construction and performance evaluation of a demonstrator set-up which consists of two identical detector modules, used in coincidence. Each module comprises 48 LYSO crystals of 100 mm length and 156 WLS strips. Crystals and strips are readout by Geiger-mode Avalanche Photo Diodes (G-APDs). The signals from the two modules are processed by fully analog front-end electronics and recorded in coincidence by a VME-based data acquisition system. Measurements with point-like 22Na sources, with the modules used both individually and in coincidence mode, allowed for a complete performance evaluation up to the focal plane reconstruction of point sources. The results obtained are in good agreement with expectations and proved the set-up to be ready for the next evaluation phase with PET phantoms filled with radiotracers.

The construction and performance of two large coaxial cylindrical multiwire proportional chambers with cathode readout, denoted as Z-detector, forming the outer part of the L3 central tracking detector, are described. Three self-supporting cylinders of about 1 m length and 1 m diameter, constructed as a sandwich of Kapton foil and foam, form the mechanical frame. In each chamber one cathode layer is subdivided into helical strips and the other one in rings. The readout of the charges induced on the cathode strips provides the avalanche position along the beam (z) direction. The detector has been running in the L3 experiment at LEP for nearly two years. The resolution of the z-measurement is 320 μm, the double track resolution is 10 mm. The efficiency of each chamber is 96%.

The measurements presented in this paper are related to the development of a PET camera based on a 3-D axial geometry with excellent 3-D spatial, timing and energy resolution. The detector modules consist of matrices of long axially oriented scintillation crystal bars, which are individually coupled to photodetectors. The axial coordinate is derived from wavelength shifting (WLS) plastic strips orthogonally interleaved between the crystal bars and readout by G-APD arrays. We report on results from measurements with two LYSO crystal bars, read with PMTs, and two WLS strips readout with G-APD devices from Hamamatsu (called MPPC). The WLS strips are positioned orthogonally underneath the LYSO bars. Yields of about 80 photoelectrons from the WLS strips for an energy deposition in the LYSO crystals equivalent to the absorption of 511 keV photons are observed. The axial coordinate in the LYSO bars is reconstructed with a precision of about 1.9 mm (FWHM) using a digital reconstruction method. The resolution of an analog coordinate reconstruction method, which uses the pulse height measurement from the WLS strips is 2.8 mm (FWHM). This resolution is still compromised by the availability of only two WLS strips and will improve with a full stack of LYSO crystals interleaved with WLS strip arrays, which is presently under development for a PET demonstrator set-up.

Geiger-mode Avalanche Photodiodes (G-APD) bear the potential to significantly improve the sensitivity of Imaging Air Cherenkov Telescopes (IACT). We are currently building the First G-APD Cherenkov Telescope (FACT) by refurbishing an old IACT with a mirror area of 9.5 square meters and are constructing a new, fine-pixelized camera using novel G-APDs. The main goal is to evaluate the performance of a complete system by observing very high energy gamma-rays from the Crab Nebula. This is an important field test to check the feasibility of G-APD-based cameras to replace at some time the PMT-based cameras of planned future IACTs like AGIS and CTA. In this article, we present the basic design of such a camera as well as some important details.

Software for Tomographic Image Reconstruction (STIR) is an open-source library for PET and SPECT image reconstruction, implementing iterative reconstruction as well as 2D- and 3D-filtered back projection. Quantitative reconstruction of PET data requires the knowledge of the scanner geometry. Typical scanners, clinical as well as pre-clinical ones, use a block-type geometry. Several rectangular blocks of crystals are arranged into regular polygons. Multiple of such polygons are arranged along the scanner axis. However, the geometrical representation of a scanner provided by STIR is a cylinder made of rings of individual crystals equally distributed in axial and transaxial directions. The data of realistic scanners are projected onto such virtual scanners prior to image reconstruction. This results in reduced quality of the reconstructed image. In this study, we implemented the above-described block geometry into the STIR library, permitting the image reconstruction without the interpolation step. In order to evaluate the difference in image quality, we performed Monte Carlo simulation studies of three different scanner designs: two scanners with multiple crystals per block and one with a single crystal per block. Simulated data were reconstructed using the standard STIR method and the newly implemented block geometry.Visual comparison between the images reconstructed by the two models for the block-type scanners shows that the new implementation enhances the image quality to the extent that the results before normalization correction are comparable with those after normalization correction. The simulation result of a uniform cylinder shows that the coefficient of variation decreases from 25.8% to 20.9% by using the new implementation in STIR. Spatial resolution is enhanced resulting in a lower partial loss of intensity in sources of small size, e.g., the spill-over ratio for spherical sources of 1.8 mm diameter is 0.19 in the block and 0.34 in the cylindrical model.Results indicate a significant improvement for the new model in comparison with the old one which mapped the polygonal geometry into a cylinder. The new implementation was tested and is available for use via the library of Swiss Federal Institute of Technology in Zurich (ETH).

Abstract The barrel section of the novel MIP Timing Detector (MTD) will be constructed as part of the upgrade of the CMS experiment to provide a time resolution for single charged tracks in the range of 30–60 ps using LYSO:Ce crystal arrays read out with Silicon Photomultipliers (SiPMs). A major challenge for the operation of such a detector is the extremely high radiation level, of about 2 × 10 14 1 MeV(Si) Eqv. n/cm 2 , that will be integrated over a decade of operation of the High Luminosity Large Hadron Collider (HL-LHC). Silicon Photomultipliers exposed to this level of radiation have shown a strong increase in dark count rate and radiation damage effects that also impact their gain and photon detection efficiency. For this reason during operations the whole detector is cooled down to about -35°C. In this paper we illustrate an innovative and cost-effective solution to mitigate the impact of radiation damage on the timing performance of the detector, by integrating small thermo-electric coolers (TECs) on the back of the SiPM package. This additional feature, fully integrated as part of the SiPM array, enables a further decrease in operating temperature down to about -45°C. This leads to a reduction by a factor of about two in the dark count rate without requiring additional power budget, since the power required by the TEC is almost entirely offset by a decrease in the power required for the SiPM operation due to leakage current. In addition, the operation of the TECs with reversed polarity during technical stops of the accelerator can raise the temperature of the SiPMs up to 60°C (about 50°C higher than the rest of the detector), thus accelerating the annealing of radiation damage effects and partly recovering the SiPM performance.

Abstract The ECAL Barrel and MTD Barrel Timing Layer subdetectors of CMS are approaching series production of electronic boards, including voltage conditioning PCBs: LVRs and PCCs respectively. 2448 LVRs and 864 PCCs will be installed during LS3 of the LHC. These boards are hosting radiation-tolerant bPOL12V ASICs which convert a broad input voltage range into required voltage levels for microelectronics between 1.2–2.5 V. Each card must be tested multiple times at various production stages to ensure its conformity. This contribution describes a methodology of testing bPOL12V conversion quality including the detection of instability regions at certain load levels.

The observation of Higgs boson production in association with a top quark-antiquark pair is reported, based on a combined analysis of proton-proton collision data at center-of-mass energies of √s = 7, 8, and 13 TeV, corresponding to integrated luminosities of up to 5.1, 19.7, and 35.9  fb^(-1), respectively. The data were collected with the CMS detector at the CERN LHC. The results of statistically independent searches for Higgs bosons produced in conjunction with a top quark-antiquark pair and decaying to pairs of W bosons, Z bosons, photons, τ leptons, or bottom quark jets are combined to maximize sensitivity. An excess of events is observed, with a significance of 5.2 standard deviations, over the expectation from the background-only hypothesis. The corresponding expected significance from the standard model for a Higgs boson mass of 125.09 GeV is 4.2 standard deviations. The combined best fit signal strength normalized to the standard model prediction is 1.26^(+0.31)_(−0.26).

We describe a novel method to extract the axial coordinate from a matrix of long axially oriented crystals, which is based on wavelength shifting (WLS) plastic strips. The method allows building compact 3-D axial gamma detector modules for PET scanners with excellent 3-D spatial, timing and energy resolution while keeping the number of readout channels reasonably low. A voxel resolution of about 10 mm3 is expected. We assess the performance of the method in two independent ways, using classical PMTs and G-APDs to read out the LYSO (LSO) scintillation crystals and the WLS strips. We observe yields in excess of 35 photoelectrons from the strips for a 511 keV gamma and reconstruct the axial coordinate with a precision of about 2.5 mm (FWHM).

Geiger-mode avalanche photodiodes (G-APD) are promising new sensors for light detection in atmospheric Cherenkov telescopes. In this paper, the design and commissioning of a 36-pixel G-APD prototype camera is presented. The data acquisition is based on the Domino Ring Sampling (DRS2) chip. A sub-nanosecond time resolution has been achieved. Cosmic-ray induced air showers have been recorded using an imaging mirror setup, in a self-triggered mode. This is the first time that such measurements have been carried out with a complete G-APD camera.

The SAFIR development represents a novel Positron Emission Tomography (PET) detector, conceived for preclinical fast acquisitions inside the bore of a Magnetic Resonance Imaging (MRI) scanner. The goal is hybrid and simultaneous PET/MRI dynamic studies at unprecedented temporal resolutions of a few seconds. The detector relies on matrices of scintillating LSO-based crystals coupled one-to-one with SiPM arrays and readout by fast ASICs with excellent timing resolution and high rate capabilities. The paper describes the detector concept and the initial results in terms of simulations and characterisation measurements.

The small animal fast insert for mRi (SAFIR) positron emission tomography insert was proposed for quantitative dynamic acquisition inside a preclinical 7T magnetic resonance imaging scanner to study kinetics of short-lived tracers. For this purpose, the SAFIR readout should be capable of handling high count rates and achieving excellent timing performance. We evaluated one of the available application specific integrated circuits (ASICs) for SiPM readout, namely SiPM timing chip (STiC) version 3.1. In this paper, we show the performances of the SAFIR PET detector with the STiC ASIC readout. The SAFIR PET detector consists of an 8 x 8 array of lutetium yttrium oxyorthosilicate 2.1 mm x 2.1 mm x 12 mm crystals coupled, with optical grease, to an 8 x 8 array of SiPMs with a 2.0 mm x 2.0 mm photo-sensitive area. Signals from the individual SiPM channels were digitized by the STiC ASIC. Hit's arrival time and time-over-threshold (TOT) were recorded into time stamps with 50.2-ps least significant bit. We obtained an average energy resolution of 18.5% full width at half maximum (FWHM) at 511-keV photopeak after TOT nonlinearity correction and an average coincidence resolving time resolution of 244-ps FWHM with time walk correction that satisfy our requirements specification on the detector performance.

The SAFIR prototype insert is a preclinical Positron Emission Tomography (PET) scanner built to acquire dynamic images simultaneously with a 7 T Bruker Magnetic Resonance Imaging (MRI) scanner. The insert is designed to perform with an excellent coincidence resolving time of 194 ps Full Width Half Maximum (FWHM) and an energy resolution of 13.8% FWHM. These properties enable it to acquire precise quantitative images at activities as high as 500 MBq suitable for studying fast biological processes within short time frames (< 5 s). In this study, the performance of the SAFIR prototype insert is evaluated according to the NEMA NU 4-2008 standard while the insert is inside the MRI without acquiring MRI data.Applying an energy window of 391-601 keV and a coincidence time window of 500 ps the following results are achieved. The average spatial resolution at 5 mm radial offset is 2.6 mm FWHM when using the Filtered Backprojection 3D Reprojection (FBP3DRP) reconstruction method, improving to 1.2 mm when using the Maximum Likelihood Expectation Maximization (MLEM) method. The peak sensitivity at the center of the scanner is 1.06%. The Noise Equivalent count Rate (NECR) is 799 kcps at the highest measured activity of 537 MBq for the mouse phantom and 121 kcps at the highest measured activity of 624 MBq for the rat phantom. The NECR peak is not yet reached for any of the measurements. The scatter fractions are 10.9% and 17.8% for the mouse and rat phantoms, respectively. The uniform region of the image quality phantom has a 3.0% STD, with a 4.6% deviation from the expected number of counts per voxel. The spill-over ratios for the water and air chambers are 0.18 and 0.17, respectively.The results satisfy all the requirements initially considered for the insert, proving that the SAFIR prototype insert can obtain dynamic images of small rodents at high activities ([Formula: see text] 500 MBq) with a high sensitivity and an excellent count-rate performance.

Interstrip and backplane capacitances on silicon microstrip detectors with p+ strip on n substrate of 320μm thickness were measured for pitches between 60 and 240μm and width over pitch ratios between 0.13 and 0.5. Parametrisations of capacitance w.r.t. pitch and width were compared with data. The detectors were measured before and after being irradiated to a fluence of 4×1014protons/cm2 of 24GeV/c momentum. The effect of the crystal orientation of the silicon has been found to have a relevant influence on the surface radiation damage, favouring the choice of a 〈100〉 substrate. Working at high bias (up to 500 V in CMS) might be critical for the stability of detector, for a small width over pitch ratio. The influence of having a metal strip larger than the p+ implant has been studied and found to enhance the stability.

A Higgs particle produced in association with a Z boson and decaying into two photons is searched for in the data collected by the L3 experiment at LEP. All possible decay modes of the Z boson are investigated. No signal is observed in 447.5 pb^-1 of data recorded at centre-of-mass energies up to 209 GeV. Limits on the branching fraction of the Higgs boson decay into two photons as a function of the Higgs mass are derived. A lower limit on the mass of a fermiophobic Higgs boson is set at 105.4 GeV at 95% confidence level.

We describe the concept and first experimental tests of a novel 3D axial Positron Emission Tomography (PET) geometry. It allows for a new way of measuring the interaction point in the detector with very high precision. It is based on a matrix of long Lutetium-Yttrium OxyorthoSilicate (LYSO) crystals oriented in the axial direction, each coupled to one Geiger Mode Avalanche Photodiode (G-APD) array. To derive the axial coordinate, Wave Length Shifter (WLS) strips are mounted orthogonally and interleaved between the crystals. The light from the WLS strips is read by custom-made G-APDs. The weighted mean of the signals in the WLS strips has proven to give very precise axial resolution. The achievable resolution along the three axes is mainly driven by the dimensions of the LYSO crystals and WLS strips. This concept is inherently free of parallax errors. Furthermore, it will allow identification of Compton interactions in the detector and for reconstruction of a fraction of them, which is expected to enhance image quality and sensitivity. We present the results of proof-of-principle tests and qualification measurements of the various components prepared to build a larger scale demonstrator consisting of two matrices of 8×6 LYSO crystals and 312 WLS strips.

Imaging Atmospheric Cherenkov Telescopes (IACT) for Gamma-ray astronomy are presently using photomultiplier tubes as photo sensors. Geiger-mode avalanche photodiodes (G-APD) promise an improvement in sensitivity and, important for this application, ease of construction, operation and ruggedness. G-APDs have proven many of their features in the laboratory, but a qualified assessment of their performance in an IACT camera is best undertaken with a prototype. This paper describes the design and construction of a full-scale camera based on G-APDs realized within the FACT project (First G-APD Cherenkov Telescope). (C) 2010 Elsevier B.V. All rights reserved.

Imaging Atmospheric Cherenkov Telescopes (IACTs) need imaging optics with large apertures and high image intensities to map the faint Cherenkov light emitted from cosmic ray air showers onto their image sensors. Segmented reflectors fulfill these needs, and composed from mass production mirror facets they are inexpensive and lightweight. However, as the overall image is a superposition of the individual facet images, alignment remains a challenge. Here we present a simple, yet extendable method, to align a segmented reflector using its Bokeh. Bokeh alig nment does not need a star or good weather nights but can be done even during daytime. Bokeh alignment optimizes the facet orientations by comparing the segmented reflectors Bokeh to a predefined template. The optimal Bokeh template is highly constricted by the reflector's aperture and is easy accessible. The Bokeh is observed using the out of focus image of a near by point like light source in a distance of about 10 focal lengths. We introduce Bokeh alignment on segmented reflectors and demonstrate it on the First Geiger-mode Avalanche Cherenkov Telescope (FACT) on La Palma, Spain.

The SAFIR collaboration is currently developing a high-rate positron emission tomography (PET) insert to study fast kinetic processes in small animals. Our insert is designed for simultaneous image acquisition with a preclinical 7 T magnetic resonance (MR) imaging device. In contrast to existing preclinical PET scanners and inserts, our hardware is optimized for high-rate measurements with source activities up to 500 MBq. As a first step, the SAFIR Prototype insert was constructed. This already incorporates the final components, but has a reduced axial field-of-view (35.6 mm). We use lutetiumyttrium oxyorthosilicate crystals (2.12 mm × 2.12 mm × 13 mm) one-to-one coupled to silicon photomultipliers. All analog signals are digitized within the insert. We use 49 MR-compatible dc- dc converters in the insert to provide the power to all readout electronics. After shimming, no degradation of the homogeneity of the static B0 field in the MR scanner was observed. During full operation, we saw a minor reduction in the signal-to-noise ratio of the MR data of 4.9%. With a low activity point source (22Na 0.65 MBq) we obtained a coincidence energy resolution of 13.8% full width at half maximum (FWhM) and a coincidence timing resolution of 194 ps (FWhM). First PET/MR rat brain and high-rate mouse cardiac images (84.9 MBq) are shown in this article.

A novel geometry for a sampling calorimeter employing inorganic scintillators as an active medium is presented. To overcome the mechanical challenges of construction, an innovative light collection geometry has been pioneered, that minimises the complexity of construction. First test results are presented, demonstrating a successful signal extraction. The geometry consists of a sampling calorimeter with passive absorber layers interleaved with layers of an active medium made of inorganic scintillating crystals. Wavelength-shifting (WLS) fibres run along the four long, chamfered edges of the stack, transporting the light to photodetectors at the rear. To maximise the amount of scintillation light reaching the WLS fibres, the scintillator chamfers are depolished. It is shown herein that this concept is working for cerium fluoride (CeF3) as a scintillator. Coupled to it, several different types of materials have been tested as WLS medium. In particular, materials that might be sufficiently resistant to the High- Luminosity Large Hadron Collider radiation environment, such as cerium-doped Lutetium- Yttrium Orthosilicate (LYSO) and cerium-doped quartz, are compared to conventional plastic WLS fibres. Finally, an outlook is presented on the possible optimisation of the different components, and the construction and commissioning of a full calorimeter cell prototype is presented.

The proposed SAFIR PET detector will measure positron electron annihilations at injected activities up to 500 MBq in a mouse or rat. The system is required to have the best possible timing resolution in order to remove accidental coincidences (randoms) and maximise the image quality for short time frames allowing the possibility of 4-D kinetic modelling of simultaneous PET and MRI for the first time. Two different ASICs, TOFPET and STiC, have been investigated with LYSO crystal scintillators coupled to SiPM detectors and using 18F sources up to 480 MBq. Timing responses are very encouraging with a coincidence time resolution of ∼100 ps measured at low activities, degrading to 130 ps at the foreseen scanner maximum event rate. Sensitivities for single event rates and coincidences are measured and compared with Geant4 Monte Carlo simulations.

Abstract The Minimum Ionizing Particle Timing Detector (MTD) will be introduced in the Compact Muon Solenoid (CMS) experiment to measure the production time of Minimum Ionizing Particles (MIPs). Power Conversion Cards (PCCs) regulates and supplies low voltage to front end electronics of the MTD barrel, the Barrel Timing Layer (BTL). The PCCs host three radiation and magnetic field tolerant DC-DC converters. The physical height of the PCC is limited to 7 mm, having necessitated development of custom inductors and shields. Additionally, the CMS Electromagnetic Calorimeter will be upgraded. On-detector Low Voltage Regulator (LVR) cards host four DC-DC converters and one linear regulator. In these proceedings we will present both cards’ designs evolution, stack-up and layout optimization, noise filtering choices and a performance evaluation.

The Alpha Magnetic Spectrometer (AMS) is designed as an independent module for installation on the International Space Station (ISS) in the year 2003 for an operational period of three years. The principal scientific objectives include the searches for antimatter and dark matter in cosmic rays. The AMS tracker uses silicon microstrip sensors to reconstruct charged-particle trajectories. A first version of the AMS, equipped with 2.1 m2 of silicon sensors and a permanent magnet, was flown on the NASA space shuttle Discovery duringJune 2–12, 1998. In this contribution, we describe the detector and present results of the tracker performance duringthe flight.

We present a project for a novel camera using Geiger-mode Avalanche Photodiodes (G-APDs), to be installed in a small telescope (former HEGRA CT3) on the MAGIC site in La Palma (Canary Island, Spain). This novel type of semiconductor photon detector provides several superior features compared to conventional photomultiplier tubes (PMTs). The most promising one is a much higher Photon Detection Efficiency.

The maximization of the photon detection efficiency (PDE) is a key issue in the development of cameras for Imaging Atmospheric Cherenkov Telescopes. Geiger-mode Avalanche Photodiodes (G-APD) are a promising candidate to replace the commonly used photomultiplier tubes by offering a larger PDE and in addition a facilitated handling. The FACT (First G-APD Cherenkov Telescope) project evaluates the feasibility of this change by building a camera based on 1440 G-APDs for an existing small telescope. As a first step towards a full camera, a prototype module using 144 G-APDs was successfully built and tested. The strong temperature dependence of G-APDs is compensated using a feedback system, which allows to keep the gain of the G-APDs constant to 0.5%.

Views Icon Views Article contents Figures & tables Video Audio Supplementary Data Peer Review Share Icon Share Twitter Facebook Reddit LinkedIn Tools Icon Tools Reprints and Permissions Cite Icon Cite Search Site Citation T. Bretz, D. Dorner, M. Backes, A. Biland, J. Buß, V. Commichau, L. Djambazov, D. Eisenacher, O. Grimm, H. von Gunten, D. Hildebrand, T. Krähenbühl, W. Lustermann, E. Lyard, K. Mannheim, D. Neise, A.-K. Overkemping, A. Paravac, F. Pauss, W. Rhode, M. Ribordy, U. Röser, J.-P. Stucki, F. Temme, J. Thaele, S. Tobler, P. Vogler, R. Walter, Q. Weitzel, M. Zänglein; FACT - The first G-APD Cherenkov telescope (first results). AIP Conf. Proc. 5 December 2012; 1505 (1): 773–776. https://doi.org/10.1063/1.4772374 Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentAIP Publishing PortfolioAIP Conference Proceedings Search Advanced Search |Citation Search

We present the prototype of a dedicated brain Positron Emission Tomography system BPET and the results of a first NEMA (NU2-2018 & NU4-2008) performance evaluation. BPET is a modular system, based on the PETA6SE application specific integrated circuit and LYSO crystals coupled in light sharing mode to silicon photomultipliers. All electronics are integrated into the detector head, which makes the system ultra-compact. The NU2-2018 spatial resolution in the axial center in [radial/tangential/axial] direction at r=10 mm is [4.0 / 3.9 / 3.5] mm full width at half maximum. The NU2-2018 system sensitivity is 2.9 cps/kBq for the smallest energy window at the radial center. It is 8.4 cps/kBq for the largest energy window considered at r=10 cm. We further show results of a noise equivalent count rate evaluation and BPET reconstructed images from a brain image quality phantom and a 3D Hoffman brain phantom. The performance characteristics of the BPET prototype are comparable to current clinical systems. BPET is the basis for the development of a clinical low-cost ultra-compact, fully integrated brain Positron Emission Tomography system.

SAFIR (Small Animal Fast Insert for mRi) is an innovative, high rate, PET detector insert for MRI, to be used for quantitative dynamic pre-clinical imaging, with very high activities injected in the animals, up to 500 MBq. The PET detector will be designed to allow for ultra short acquisition periods (of the order of a few seconds) simultaneously with the MRI, permitting unprecedented temporal resolutions in preclinical dynamic multimodal imaging. High sensitivity (~ 6%), high spatial resolution (~1.5 mm FWHM), excellent coincidence timing resolution (CTR ~ 300 ps FWHM) and a fast DAQ system able to cope with the huge data throughput are required. Parallel with the hardware efforts, dedicated 4D algorithms for image reconstruction must be developed. The overall state of the project will be presented, including ongoing activities towards the choice and characterization of the detector components (crystals, SiPMs and readout chips), MonteCarlo simulations, and first reconstruction of various simulated sources. Special emphasis will be given to the results of a recent high rate test, where the TOFPET ASIC has been tested with Hamamatsu S12642-0404PB-50 SiPM arrays coupled to matrices of LYSO:Ce crystals (3.1x3.1x12 mm3 each), exposed to a 500 MBq activity of FDG radiotracer in a volume of about 0.5 cm3.

Imaging Atmospheric Cherenkov Telescopes (IACTs) need imaging optics with large apertures and high image intensities to map the faint Cherenkov light emitted from cosmic ray air showers onto their image sensors. Segmented reflectors fulfill these needs, and as they are composed from mass production mirror facets they are inexpensive and lightweight. However, as the overall image is a superposition of the individual facet images, alignment is a challenge. Here we present a computer vision based star tracking alignment method, which also works for limited or changing star light visibility. Our method normalizes the mirror facet reflection intensities to become independent of the reference star's intensity or the cloud coverage. Using two CCD cameras, our method records the mirror facet orientations asynchronously of the telescope drive system, and thus makes the method easy to integrate into existing telescopes. It can be combined with remote facet actuation, but does not require one to work. Furthermore, it can reconstruct all individual mirror facet point spread functions without moving any mirror. We present alignment results on the 4 meter First Geiger-mode Avalanche Cherenkov Telescope (FACT).

The L3 central tracking detector has been in operation since the start-up of LEP (Large Electron Positron collider) in 1989. This detector consists of a Time Expansion Chamber (TEC), a layer of Plastic Scintillating Fibers and a Z-chamber. The TEC gives a high spatial resolution and an excellent multi-track reconstruction capability. The fibers are designed to calibrate the drift velocity with high precision. The Z-Chamber provides TEC with accurate information about the z-coordinates of the tracks. A description of the design and the infrastructure of these three detectors, including the readout and data acquisition system, is given. The performance of the detectors during the 1990 and 1991 LEP running periods is presented.

Views Icon Views Article contents Figures & tables Video Audio Supplementary Data Peer Review Share Icon Share Twitter Facebook Reddit LinkedIn Tools Icon Tools Reprints and Permissions Cite Icon Cite Search Site Citation T. Bretz, M. Backes, I. Braun, D. Neise, W. Rhode, K. Mannheim, F. Pauss, J. K. Becker, A. Biland, I. Britvich, S. C. Commichau, D. Dorner, D. Hadasch, D. Hildebrand, U. Horisberger, D. Kranich, E. Lorenz, W. Lustermann, M. Pohl, M. Ribordy, D. Renker, M. Rissi, U. Röser, U. Straumann, G. Viertel, H. von Gunten; Long‐term monitoring of bright blazars with a dedicated Cherenkov telescope. AIP Conf. Proc. 24 December 2008; 1085 (1): 850–853. https://doi.org/10.1063/1.3076809 Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentAIP Publishing PortfolioAIP Conference Proceedings Search Advanced Search |Citation Search

The design and construction of a PET camera module with high sensitivity, full 3-D spatial reconstruction and very good energy resolution is presented. The basic principle consists of an axial arrangement of long scintillation crystals around the Field Of View (FOV), providing a measurement of the transverse coordinates of the interacting 511 keV gamma ray. On top of each layer of crystals, an array of Wave-Length Shifter (WLS) strips, which collect the light leaving the crystals sideways, is positioned orthogonal to the crystal direction. The signals in the WLS strips allow a precise measurement of the z (axial) co-ordinate of the 511 keV γ-ray gamma impact. The construction of two modules used for demonstration of the concept is described. First preliminary results on spatial and energy resolution from one full module will be shown.

Abstract Standard Positron Emission Tomography (PET) cameras need to reach a compromise between spatial resolution and sensitivity. To overcome this limitation we developed a novel concept of PET. Our AX-PET demonstrator is made of LYSO crystals aligned along the z coordinate (patient's axis) and WLS strips orthogonally placed with respect to the crystals. This concept offers full 3D localization of the photon interaction inside the camera. Thus the spatial resolution and the sensitivity can be simultaneously improved and the reconstruction of Compton interactions inside the detector is also possible. Moreover, by means of G-APDs for reading out the photons, both from LYSO and WLS, the detector is insensitive to magnetic fields and it is then suitable to be used in a combined PET/MRI apparatus. A complete Monte Carlo simulation and dedicated reconstruction software have been developed. The two final modules, each composed of 48 crystals and 156 WLS strips, have been built and fully characterized in a dedicated test set-up. The results, obtained with a 22 Na point source (0.25 mm diameter), of the single module performances and a first estimation of the performances with the two module system are reported.

The First G-APD Cherenkov Telescope (FACT) was built on the Canary Island of La Palma in October 2011 as a proof of principle for silicon based photosensors in Cherenkov Astronomy. The scientific goal of the project is to study the variability of active galatic nuclei (AGN) at TeV energies. Observing a small sample of TeV blazars whenever possible, an unbiased data sample is collected. This allows to study the variability of the selected objects on timescales from hours to years. Results from the first three years of monitoring will be presented. To provide quick flare alerts to the community and trigger multi-wavelength observations, a quick look analysis has been installed on-site providing results publicly online within the same night. In summer 2014, several flare alerts were issued. Results of the quick look analysis are summarized.

We have measured the probability, n(g->cc~), of a gluon splitting into a charm-quark pair using 1.7 million hadronic Z decays collected by the L3 detector. Two independent methods have been applied to events with a three-jet topology. One method relies on tagging charmed hadrons by identifying a lepton in the lowest energy jet. The other method uses a neural network based on global event shape parameters. Combining both methods, we measure n(g->cc~)= [2.45 +/- 0.29 +/- 0.53]%.

The First G-APD Cherenkov Telescope (FACT) is the first Cherenkov telescope equipped with a camera made of silicon photon detectors (G-APD aka. SiPM). Since October 2011, it is regularly taking data on the Canary Island of La Palma. G-APDs are ideal detectors for Cherenkov telescopes as they are robust and stable. Furthermore, the insensitivity of G-APDs towards strong ambient light allows to conduct observations during bright Moon and twilight. This gain in observation time is essential for the long-term monitoring of bright TeV blazars. During the commissioning phase, hundreds of hours of data (including data from the the Crab Nebula) were taken in order to understand the performance and sensitivity of the instrument. The data cover a wide range of observation conditions including different weather conditions, different zenith angles and different light conditions (ranging from dark night to direct full Moon). We use a new parmetrisation of the Moon light background to enhance our scheduling and to monitor the atmosphere. With the data from 1.5 years, the long-term stability and the performance of the camera during Moon light is studied and compared to that achieved with photomultiplier tubes so far.

The First G-APD Cherenkov telescope (FACT) is the first telescope using silicon photon detectors (G-APD aka. SiPM). It is built on the mount of the HEGRA CT3 telescope, still located at the Observatorio del Roque de los Muchachos, and it is successfully in operation since Oct. 2011. The use of Silicon devices promises a higher photon detection efficiency, more robustness and higher precision than photo-multiplier tubes. The FACT collaboration is investigating with which precision these devices can be operated on the long-term. Currently, the telescope is successfully operated from remote and robotic operation is under development. During the past months of operation, the foreseen monitoring program of the brightest known TeV blazars has been carried out, and first physics results have been obtained including a strong flare of Mrk501. An instantaneous flare alert system is already in a testing phase. This presentation will give an overview of the project and summarize its goals, status and first results.

A sampling calorimeter using cerium fluoride scintillating crystals as active material, interleaved with heavy absorber plates, and read out by wavelength-shifting (WLS) fibers is being studied as a calorimeter option for detectors at the upgraded High-Luminosity LHC (HL-LHC) collider at CERN. A prototype has been exposed to electron beams of different energies at the INFN Frascati (Italy) Beam Test Facility. This paper presents results from the studies performed on the prototype, such as signal amplitudes, light yield and energy resolution.

The Small Animal Fast Insert for mRi (SAFIR) will be a PET insert for the Bruker BioSpin 70/30. It aims at applications where fast processes such as blood perfusion in the rodent brain are to be monitored comprehensively and non-invasively. Employing electronics originally designed for time-of-flight applications, coincidence resolving times of less than a nanosecond can be achieved allowing for short coincidence time windows. Consequently, random contributions to the coincidence events are suppressed, making short acquisition frames with very high tracer concentrations possible. This will allow collecting sufficient count statistics in a few seconds. Geant4-based Monte Carlo simulations were used to characterize the performance of the reference design consisting of polished LSO-like crystals, one-to-one coupled to Silicon Photomultipliers. The crystals are grouped into 8×8 matrices, which are arranged into 24 modules and 10 rings. Similar methods as described in the NEMA NU 4-2008 standard were employed. The simulation results on NECR, sensitivity, and spatial resolution will be presented. Most notably, the NECR at 500 MBq is almost nine times higher than at 50 MBq for the given scanner. Combined with a very high sensitivity, this allows for short acquisition times using these very high injected doses. In addition, essentially random-free measurements at standard activities below 50 MBq are possible.

Since two years, the FACT telescope is operating on the Canary Island of La Palma. Apart from its purpose to serve as a monitoring facility for the brightest TeV blazars, it was built as a major step to establish solid state photon counters as detectors in Cherenkov astronomy. The camera of the First G-APD Cherenkov Telesope comprises 1440 Geiger-mode avalanche photo diodes (G-APD), equipped with solid light guides to increase the effective light collection area of each sensor. Since no sense-line is available, a special challenge is to keep the applied voltage stable although the current drawn by the G-APD depends on the flux of night-sky background photons significantly varying with ambient light conditions. Methods have been developed to keep the temperature and voltage dependent response of the G-APDs stable during operation. As a cross-check, dark count spectra with high statistics have been taken under different environmental conditions. In this presentation, the project, the developed methods and the experience from two years of operation of the first G-APD based camera in Cherenkov astronomy under changing environmental conditions will be presented.

Studies have been done and continue on the design and construction of a Shashlik detector using Radiation hard quartz capillaries filled with wavelength shifting liquid to collect the scintillation light from LYSO crystals for use as a calorimeter in the Phase II CMS upgrade at CERN. The work presented here focuses on the studies of the capillaries and liquids that would best suit the purpose of the detector. Comparisons are made of various liquids, concentrations, and capillary construction techniques will be discussed.

The MIP Timing Detector will provide additional timing capabilities for detection of minimum ionizing particles (MIPs) at CMS during the High Luminosity LHC era, improving event reconstruction and pileup rejection. The central portion of the detector, the Barrel Timing Layer (BTL), will be instrumented with LYSO:Ce crystals and Silicon Photomultipliers (SiPMs) providing a time resolution of about 30 ps at the beginning of operation, and degrading to 50-60 ps at the end of the detector lifetime as a result of radiation damage. In this work, we present the results obtained using a 120 GeV proton beam at the Fermilab Test Beam Facility to measure the time resolution of unirradiated sensors. A proof-of-concept of the sensor layout proposed for the barrel region of the MTD, consisting of elongated crystal bars with dimensions of about 3 x 3 x 57 mm$^3$ and with double-ended SiPM readout, is demonstrated. This design provides a robust time measurement independent of the impact point of the MIP along the crystal bar. We tested LYSO:Ce bars of different thickness (2, 3, 4 mm) with a geometry close to the reference design and coupled to SiPMs manufactured by Hamamatsu and Fondazione Bruno Kessler. The various aspects influencing the timing performance such as the crystal thickness, properties of the SiPMs (e.g. photon detection efficiency), and impact angle of the MIP are studied. A time resolution of about 28 ps is measured for MIPs crossing a 3 mm thick crystal bar, corresponding to an MPV energy deposition of 2.6 MeV, and of 22 ps for the 4.2 MeV MPV energy deposition expected in the BTL, matching the detector performance target for unirradiated devices.

The Alpha Magnetic Spectrometer (AMS) is designed as an independent module for installation on the International Space Station (ISS) for an operational period of 3 years. The AMS is the first cosmic ray spectrometer equipped with a large area silicon tracker (>5m2). A preliminary version of the detector was flown on the NASA space shuttle Discovery during June 2–12, 1998. Results for the dimensional stability of the silicon tracker planes based on the flight data, and the metrology data recorded before and after the flight, are presented.

AX-PET is a novel PET detector based on axially oriented crystals and orthogonal wavelength shifter (WLS) strips, both individually read out by silicon photo-multipliers. Its design decouples sensitivity and spatial resolution, by reducing the parallax error due to the layered arrangement of the crystals. Additionally the granularity of AX-PET enhances the capability to track photons within the detector yielding a large fraction of inter-crystal scatter events. These events, if properly processed, can be included in the reconstruction stage further increasing the sensitivity. Its unique features require dedicated Monte-Carlo simulations, enabling the development of the device, interpreting data and allowing the development of reconstruction codes. At the same time the non-conventional design of AX-PET poses several challenges to the simulation and modeling tasks, mostly related to the light transport and distribution within the crystals and WLS strips, as well as the electronics readout. In this work we present a hybrid simulation tool based on an analytical model and a Monte-Carlo based description of the AX-PET demonstrator. It was extensively validated against experimental data, providing excellent agreement.

Abstract The AX-PET collaboration has developed a novel concept for high resolution PET imaging to overcome some of the performance limitations of classical PET cameras, in particular the compromise between spatial resolution and sensitivity introduced by the parallax error. The detector consists of an arrangement of long LYSO scintillating crystals axially oriented around the field of view together with arrays of wave length shifter strips orthogonal to the crystals. This matrix allows a precise 3D measurement of the photon interaction point. This is valid both for photoelectric absorption at 511 keV and for Compton scattering down to deposited energies of about 100 keV. Crystals and WLS strips are individually read out using Geiger-mode Avalanche Photo Diodes (G-APDs). The sensitivity of such a detector can be adjusted by changing the number of layers and the resolution is defined by the crystal and strip dimensions. Two AX-PET modules were built and fully characterized in dedicated test set-ups at CERN, with point-like 22 Na sources. Their performance in terms of energy ( R energy ≈ 11.8 % (FWMH) at 511 keV) and spatial resolution was assessed ( σ axial ≈ 0.65 mm ), both individually and for the two modules in coincidence. Test campaigns at ETH Zurich and at the company AAA allowed the tomographic reconstructions of more complex phantoms validating the 3D reconstruction algorithms. The concept of the AX-PET modules will be presented together with some characterization results. We describe a count rate model which allows to optimize the planing of the tomographic scans.

The Axial PET (AX-PET) concept proposes a novel detection geometry for PET, based on layers of long scintillating crystals axially aligned with the bore axis. Arrays of wavelength shifting (WLS) strips are placed orthogonally and underneath the crystal layers; both crystals and strips are individually readout by G-APDs. The axial coordinate is obtained from the WLS signals by means of a Center-of-Gravity method combined with a cluster algorithm. This design allows spatial resolution and sensitivity to be decoupled and thus simultaneously optimized. In this work we present the latest results obtained with the 2-module AX-PET scanner prototype, which consists of 6 radial layers of 8 LYSO crystals each (crystal size: 3 × 3 × 100 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> ). The WLS arrays comprise 26 strips (3-mm wide) per layer. The estimated energy resolution from point-like measurements is 11.8% (FWHM at 511 keV). The intrinsic spatial resolution was measured for the two modules in coincidence at two different configurations using point-like sources, showing very little degradation when the modules were placed oblique to each other. The axial spatial resolution was 1.5 mm (FWHM) in all the studied cases. Tomographic data of extended phantoms filled with fluorine-18 have been acquired. Imaging a larger transaxial Field-of-View (when compared to the previous measurement campaign) was possible thanks to implementing secondary motion of one of the modules. We have also developed various reconstruction approaches which take into account the particular nature of AX-PET data, as well as a count rate model which allowed us to develop an acquisition protocol able to compensate for count losses. The reconstructed phantom images confirm the imaging capabilities of AX-PET, and the recent advancements in the DAQ let us expect significant improvements for future campaigns.

In recent years graphical processing units (GPUs) have become a powerful tool in scientific computing. Their potential to speed up highly parallel applications brings the power of high performance computing to a wider range of users. However, programming these devices and integrating their use in existing applications is still a challenging task. In this paper we examined the potential of GPUs for two different applications. The first application, created at Paul Scherrer Institut (PSI), is used for parameter fitting during data analysis of μSR (muon spin rotation, relaxation and resonance) experiments. The second application, developed at ETH, is used for PET (Positron Emission Tomography) image reconstruction and analysis. Applications currently in use were examined to identify parts of the algorithms in need of optimization. Efficient GPU kernels were created in order to allow applications to use a GPU, to speed up the previously identified parts. Benchmarking tests were performed in order to measure the achieved speedup. During this work, we focused on single GPU systems to show that real time data analysis of these problems can be achieved without the need for large computing clusters. The results show that the currently used application for parameter fitting, which uses OpenMP to parallelize calculations over multiple CPU cores, can be accelerated around 40 times through the use of a GPU. The speedup may vary depending on the size and complexity of the problem. For PET image analysis, the obtained speedups of the GPU version were more than ×40 larger compared to a single core CPU implementation. The achieved results show that it is possible to improve the execution time by orders of magnitude.

A prototype for a sampling calorimeter made out of cerium fluoride crystals interleaved with tungsten plates, and read out by wavelength-shifting fibres, has been exposed to beams of electrons with energies between 20 and 150 GeV, produced by the CERN Super Proton Synchrotron accelerator complex. The performance of the prototype is presented and compared to that of a Geant4 simulation of the apparatus. Particular emphasis is given to the response uniformity across the channel front face, and to the prototype׳s energy resolution.

The First Geiger-mode Avalanche photodiode (G-APD) Cherenkov Telescope (FACT) has been operating on the Canary island of La Palma since October 2011. Operations were automated so that the system can be operated remotely. Manual interaction is required only when the observation schedule is modified due to weather conditions or in case of unexpected events such as a mechanical failure. Automatic operations enabled high data taking efficiency, which resulted in up to two terabytes of FITS files being recorded nightly and transferred from La Palma to the FACT archive at ISDC in Switzerland. Since long term storage of hundreds of terabytes of observations data is costly, data compression is mandatory. This paper discusses the design choices that were made to increase the compression ratio and speed of writing of the data with respect to existing compression algorithms. Following a more detailed motivation, the FACT compression algorithm along with the associated I/O layer is discussed. Eventually, the performances of the algorithm is compared to other approaches.

High-precision tracking and charge selection with silicon strip detectors for relativistic ions has been investigated using a 12C beam of 1.5GeV/u at GSI with prototype modules developed for the AMS tracker. The ionization energy loss is measured and compared to the Landau–Vavilov theory for ions of charge number up to Z=6. The linearity in Z2 is examined. The capability to distinguish different Z values based on the ionization energy loss is evaluated. The spatial resolution of the silicon strip detectors is investigated for carbon ions. The angular distribution of multiple Coulomb scattering is studied with lead absorbers. The results are compared to the Molière theory and the Gaussian approximation of GEANT calculations.

The vertex drift chamber of the L3 Experiment at LEP, based on the time expansion principle, was in operation from the start-up of LEP in 1989 until the shutdown of LEP in 2000. The gas mixture used was 80% CO2 and 20% i-C4H10 at a pressure of 1200mbar. We present the design of the chamber, the infrastructure and the performance during the 11 years of operation. The total radiation received on the anode wires was ∼10−4C/cm. No degradation of the anode pulse amplitude, wire efficiencies and resolution was observed for the whole running period.

An underwater neutrino experiment has been proposed which provides precise measurements of the neutrino mixing parameters θ23 and Δm232 and permits an increase of sensitivity for the small angle θ13 by more than one order of magnitude. A Cherenkov detector of about 1.5 Mt active mass, deployed in the Gulf of Taranto, utilizes the CNGS beam in off-axis configuration which represents an essentially mono-energetic source of muon neutrinos. A unique feature of the experiment is the possibility to move the detector and therefore exploit different baselines around 1200 km where the oscillation pattern is fully developed. The conceptual detector design consists of O(30,000) large area and acceptance photosensors arranged in a matrix of ∼300×300 m2 size. Hybrid photon detectors are considered as promising candidates as they provide clean signal characteristics and uniform collection efficiency. We discuss the design and expected performance of a large spherical HPD with 380 mm diameter, which is housed in a high-pressure glass container. A scaled prototype HPD of 208 mm diameter is currently under development using the existing CERN HPD facility.

Since October 2011, the First G-APD Cherenkov Telescope (FACT) is operated successfully on the Canary Island of La Palma. Apart from the proof of principle for the use of G-APDs in Cherenkov telescopes, the major goal of the project is the dedicated long-term monitoring of a small sample of bright TeV blazars. The unique properties of G-APDs permit stable observations also during strong moon light. Thus a superior sampling density is provided on time scales at which the blazar variability amplitudes are expected to be largest, as exemplified by the spectacular variations of Mrk 501 observed in June 2012. While still in commissioning, FACT monitored bright blazars like Mrk 421 and Mrk 501 during the past 1.5 years so far. Preliminary results including the Mrk 501 flare from June 2012 will be presented.

AX-PET stands for a new geometrical concept for a high resolution and high sensitivity PET scanner, based on an axial arrangement of long scintillating crystals in the tomograph, for a parallax free PET detector. Two identical AX-PET modules – consisting of matrices of LYSO crystals interleaved with WLS strips – have been built. They form the AX-PET Demonstrator, which has been extensively characterized and successfully used for the reconstruction of images of several phantoms. In this paper we report on the current status of the project, with emphasis on the most relevant results achieved both in terms of detector characterization and image reconstruction. We also discuss the recent preliminary results obtained with the digital SiPM from Philips (dSiPM), which are currently being tested as a possible alternative photodetector for AX-PET. With their very good intrinsic time resolution, dSiPM could add Time of Flight capability to the AX-PET concept.

This paper presents the current architecture of the control and safety systems designed and implemented for the Electromagnetic Calorimeter (ECAL) of the Compact Muon Solenoid (CMS) experiment at the Large Hadron Collider (LHC). An evaluation of system performance during all CMS physics data taking periods is reported, with emphasis on how software and hardware solutions are used to overcome limitations, whilst maintaining and improving reliability and robustness. The outcomes of the CMS ECAL Detector Control System (DCS) Software Analysis Project were a fundamental step towards the integration of all control system applications and the consequent piece-by-piece software improvements allowed a smooth transition to the latest revision of the system. The ongoing task of keeping the system in-line with new hardware technologies and software platforms specified by the CMS DCS Group is discussed. The structure of the comprehensive support service with detailed incident logging is presented in addition to a complete test setup for reproducing failures and for testing solutions prior to deployment into production. A correlation between the acquired experience, the development of new software tools and a reduction in the DCS support load is highlighted.

Geiger-mode avalanche photodiodes (G-APD, SiPM) are a much discussed alternative to photomultiplier tubes in Cherenkov astronomy. The First G-APD Cherenkov Telescope (FACT) collaboration builds a camera based on a hexagonal array of 1440 G-APDs and has now finalized its construction phase. A light-collecting solid PMMA cone is glued to each G-APD to eliminate dead space between the G-APDs by increasing the active area, and to restrict the light collection angle of the sensor to the reflector area in order to reduce the amount of background light. The processing of the signals is integrated in the camera and includes the digitization using the domino ring sampling chip DRS4.

We present results obtained with full-size wedge silicon microstrip detectors bonded to APV6 (Raymond et al., Proceedings of the 3rd Workshop on Electronics for LHC Experiments, CERN/LHCC/97-60) readout chips. We used two identical modules, each consisting of two crystals bonded together. One module was irradiated with 1.7×1014neutrons/cm2. The detectors have been characterized both in the laboratory and by exposing them to a beam of minimum ionizing particles. The results obtained are a good starting point for the evaluation of the performance of the “ensemble” detector plus readout chip in a version very similar to the final production one. We detected the signal from minimum ionizing particles with a signal-to-noise ratio ranging from 9.3 for the irradiated detector up to 20.5 for the non-irradiated detector, provided the parameters of the readout chips are carefully tuned.

Flaring activity of Active Galactic Nuclei (AGN) in VHE γ-ray astronomy is observed on timescales from minutes to years and can be explained either by the interaction of relativistic jets with the surrounding material or by imprints of the central engine, like temporal modulation caused by binary systems of supermassive black holes. The key to answer those questions lies in combining 24/7 monitoring with short high sensitivity exposures as provided by the third generation γ-ray astronomy instruments like MAGIC, VERITAS and H.E.S.S. The long-term observations can be provided by a global network of small robotic Cherenkov telescopes. 1 As a first step, we are currently setting up a dedicated Cherenkov telescope, which will carry out joint observations with the Whipple 10 m telescope for AGN monitoring. The new telescope will be designed for low costs but high performance by upgrading one of the former HEGRA telescopes, still located at the MAGIC site on the Canary Island of La Palma (Spain). The main novelties will be its robotic operation and a novel camera type, resulting in a greatly improved sensitivity and a lower energy threshold.

We describe a PET device based on a novel method to extract the coordinates of the interaction point of the 511keV γ rays from 100 mm long and thin LYSO (Lutetium Yttrium OxyorthoSilicate) scintillator bars, positioned axially in the tomograph. The coordinate along the hit crystal is measured by using a hodoscope of Wave Length Shifting (WLS) plastic strips mounted perpendicularly to each plane of scintillators. As photodetectors, new Geiger mode Avalanche PhotoDetectors (G-APDs) with integrated electronics are being used to detect both the hit crystal in a block (x and y coordinates) and the interaction point in the crystal (z coordinate) through the light escaping from the crystal and transmitted to the WLS strips. In this way, the γ interaction point can be determined with a spatial resolution of few cubic millimeters down to a minimum deposited energy of about 50 keV, resulting in a volumetric precision very close to the limits imposed by the physics of the positron annihilation. The method allows to increase the detection efficiency without affecting the spatial resolution by adding scintillator planes in the radial direction. A demonstrator scanner, based on two matrices of 8 × 6 LYS crystals and 312 WLS strips, slotted in between the crystals, is under construction. Preliminary results from the feasibility studies of the various components will be presented.

The AX-PET is a new geometrical concept for a high resolution 3D PET scanner, based on matrices of axially oriented LYSO crystals interleaved by stacks of WLS, both individually read out by G-APDs. A PET demonstrator, based on two detector modules used in coincidence, is currently under construction.

The variability of the very high en- ergy (VHE) emission from blazars seems to be connected with the feeding and propagation of rel- ativistic jets and with their origin in supermassive black hole binaries. The key to understanding their properties is measuring well-sampled gamma-ray lightcurves, revealing the typical source behavior unbiased by prior knowledge from other wavebands. Using ground-based gamma-ray observatories with exposures limited by dark-time, a global network of several telescopes is needed to carry out full- time measurements. Obviously, such observations are time-consuming and, therefore, cannot be carried out with the present state of the art instruments. The DWARF telescope on the Canary Island of La Palma is dedicated to monitoring observations. It is currently being set up, employing a cost- efficient and robotic design. Part of this project is the future construction of a distributed network of small telescopes. The physical motivation of VHE long-term monitoring will be outlined in detail and the perspective for a network for 24/7 observations will be presented.

(1) Background: Small Animal Fast Insert for MRI detector I (SAFIR-I) is a preclinical Positron Emission Tomography (PET) insert for the Bruker BioSpec 70/30 Ultra Shield Refrigerated (USR) preclinical 7T Magnetic Resonance Imaging (MRI) system. It is designed explicitly for high-rate kinetic studies in mice and rats with injected activities reaching 500MBq, enabling truly simultaneous quantitative PET and Magnetic Resonance (MR) imaging with time frames of a few seconds in length. (2) Methods: SAFIR-I has an axial field of view of 54.2mm and an inner diameter of 114mm. It employs Lutetium Yttrium OxyorthoSilicate (LYSO) crystals and Multi Pixel Photon Counter (MPPC) arrays. The Position-Energy-Timing Application Specific Integrated Circuit, version 6, Single Ended (PETA6SE) digitizes the MPPC signals and provides time stamps and energy information. (3) Results: SAFIR-I is MR-compatible. The system’s Coincidence Resolving Time (CRT) and energy resolution are between separate-uncertainty 209.0(3)ps and separate-uncertainty 12.41(02) Full Width at Half Maximum (FWHM) at low activity and separate-uncertainty 326.89(12)ps and separate-uncertainty 20.630(011) FWHM at 550MBq, respectively. The peak sensitivity is ∼1.6. The excellent performance facilitated the successful execution of first in vivo rat studies beyond 300MBq. Based on features visible in the acquired images, we estimate the spatial resolution to be ∼2mm in the center of the Field Of View (FOV). (4) Conclusion: The SAFIR-I PET insert provides excellent performance, permitting simultaneous in vivo small animal PET/MR image acquisitions with time frames of a few seconds in length at activities of up to 500MBq.

Light crosstalk between optically separated elements of an 8 ×8 lutetium-yttrium oxyorthosilicate (LYSO) scintillation crystal matrix has been studied. The investigation was motivated by a desire to optimize the performance of the Small Animal Fast Insert for MRI (SAFIR) collaboration’s forthcoming SAFIR-II Positron Emission Tomography (PET) system. Including the originally devised inter-crystal optical separation layer comprising bonded 3M Enhanced Specular Reflector (ESR) foils, a total of four different optical separation layers have been evaluated. The alternative options included additional aluminum separators sandwiched between ESR foils, barium sulfate powder coatings of the crystals paired with interjacent ESR foils, and non-bonded ESR foils. Any other differences in materials, manufacturing, assembly and readout electronics have, to the best of our knowledge, been precluded. To quantify light crosstalk for a 511keV photon, the number, distribution, and energy of all incidental hits registered in <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">18</sup> F measurements at activities <10MBq were recorded and analyzed. Additional crosstalk hits could be observed for all four options (0.41, 0.13, 1.28, and 0.38, respectively, on average per 511keV photon); in terms of energy, the average crosstalk was 4.9%, 2.3%, 7.5%, and 3.8%, respectively. Effects on detector performance could be studied by conducting coincidence measurements with the existing SAFIR-I PET/MR scanner. At an activity of 546MBq, coincidence resolving times of 290ps, 228ps, 280ps, and 332ps, respectively, could be achieved and energy resolutions of 18.86%, 14.25%, 17.28%, and 15.60%, respectively, were found. Hence, sandwiching aluminum separators between ESR foils is advisable for minimized crosstalk and optimal resolutions at activities surpassing 500MBq.

In PET imaging, improving sensitivity while maintaining very good spatial resolution is crucial. To achieve this goal, we propose a novel concept of PET scanner, with axially arranged crystals, providing a high sensitivity and a 3D reconstruction of the gamma interaction point. The trans-axial coordinate is given by the crystal hit, while the z coordinate is reconstructed by the weighted distribution of light escaping the crystal and entering into an array of Wave Length Shifting (WLS) strips interleaving the crystal layers. This novel configuration allows full identification of Compton interactions in the crystals that can be included in image reconstruction thus enhancing the sensitivity. We present preliminary results obtained by a small prototype consisting of 4×4 crystals with orthogonally interleaved WLS strips. Experimental data are compared to simulated data.

T. Bretz, M. Backes, D. Neise, W. Rhode, K. Mannheim, D. Dorner, D. Hadasch, J. K. Becker, A. Biland, I. Braun, I. Britvitch, S. C. Commichau, M. Rissi, H. von Gunten, D. Hildebrand, D. Kranich, E. Lorenz, W. Lustermann, F. Pauss, M. Pohl, D. Renker, U. Roser, U. Straumann f , G. Viertel Universitat Wurzburg, 97074 Wurzburg, Germany Technische Universitat Dortmund, 44221 Dortmund, Germany ETH Zurich, 8093 Zurich, Switzerland University of Geneva, CH-1211 Geneva, Switzerland Paul Scherrer Institut (PSI) Villingen, CH-5232 Villingen, Switzerland Universitat Zurich, CH-8057 Zurich, Switzerland

The barrel section of the novel MIP Timing Detector (MTD) will be constructed as part of the upgrade of the CMS experiment to provide a time resolution for single charged tracks in the range of $30-60$ ps using LYSO:Ce crystal arrays read out with Silicon Photomultipliers (SiPMs). A major challenge for the operation of such a detector is the extremely high radiation level, of about $2\times10^{14}$ 1 MeV(Si) Eqv. n/cm$^2$, that will be integrated over a decade of operation of the High Luminosity Large Hadron Collider (HL-LHC). Silicon Photomultipliers exposed to this level of radiation have shown a strong increase in dark count rate and radiation damage effects that also impact their gain and photon detection efficiency. For this reason during operations the whole detector is cooled down to about $-35^{\circ}$C. In this paper we illustrate an innovative and cost-effective solution to mitigate the impact of radiation damage on the timing performance of the detector, by integrating small thermo-electric coolers (TECs) on the back of the SiPM package. This additional feature, fully integrated as part of the SiPM array, enables a further decrease in operating temperature down to about $-45^{\circ}$C. This leads to a reduction by a factor of about two in the dark count rate without requiring additional power budget, since the power required by the TEC is almost entirely offset by a decrease in the power required for the SiPM operation due to leakage current. In addition, the operation of the TECs with reversed polarity during technical stops of the accelerator can raise the temperature of the SiPMs up to $60^{\circ}$C (about $50^{\circ}$C higher than the rest of the detector), thus accelerating the annealing of radiation damage effects and partly recovering the SiPM performance.

Maintaining the required performance of the CMS electromagnetic calorimeter (ECAL) barrel at the High-Luminosity Large Hadron Collider (HL-LHC) requires the replacement of the entire on-detector electronics. 12240 new very front end (VFE) cards will amplify and digitize the signals of 62100 lead-tungstate crystals instrumented with avalanche photodiodes. The VFE cards host five channels of CATIA pre-amplifier ASICs followed by LiTE-DTU ASICs, which digitize signals with 160MS/s and 12bit resolution. We present the strategy and infrastructure developed for achieving the required reliability of less than 0.5% failing channels over the expected lifetime of 20 years. This includes the choice of standards, design for reliability and manufacturing, as well as factory acceptance tests, reception testing, environmental stress screening and calibration of the VFE cards.

Small Animal Fast Insert for MRI detector I (SAFIR-I) is a novel Positron Emission Tomography insert for a [Formula: see text] Bruker BioSpec 70/30 Ultra Shield Refrigerated Magnetic Resonance Imaging (MRI) system. It facilitates truly simultaneous quantitative imaging in mice and rats at injected activities as high as [Formula: see text]. Exploitation of the resulting high count rates enables quick image formation at few seconds per frame. In this investigation, key performance parameters of SAFIR-I have been determined according to the evaluations outlined in the National Electrical Manufacturers Association (NEMA) Standards Publication NU 4-2008 (NEMA-NU4) protocol.Using an energy window of 391 to [Formula: see text] and a Coincidence Timing Window of [Formula: see text], the following performance was observed: The average spatial resolution at [Formula: see text] radial offset (Full Width at Half Maximum) is [Formula: see text] when using Filtered Backprojection, 3D Reprojection reconstruction. For the mouse- and rat-like phantoms, the maximal Noise-Equivalent Count Rates (NECRs) are [Formula: see text] at the highest tested average effective concentration of [Formula: see text], and [Formula: see text] at the highest tested average effective concentration of [Formula: see text], respectively. The NECR peak is not yet reached for either of these cases. The peak sensitivity is [Formula: see text]. The Image Quality phantom uniformity standard deviation is [Formula: see text]. The Recovery Coefficient for the [Formula: see text] rod is [Formula: see text]. The Spill-Over Ratios are [Formula: see text] and [Formula: see text], for the water- and air-filled cylinder, respectively. An accuracy of [Formula: see text] was achieved for the quantitative calibration of reconstructed voxel values.The measured performance parameters indicate that the various design goals have been achieved. SAFIR-I offers excellent performance, especially at the high activities it was designed for. This facilitates planned experiments with fast tracer kinetics in small animals. Ways to potentially improve performance can still be explored. Simultaneously, further performance gains can be expected for a forthcoming insert featuring 2.7 times longer axial coverage named Small Animal Fast Insert for MRI detector II (SAFIR-II).

SAFIR-I is a preclinical PET insert to a 7T Bruker BioSpec 70/30 MRI, facilitating truly simultaneous PET/MR imaging in mice and rats at injected activities reaching 500MBq. It features 54.2mm axial FOV, 128.1mm inner radius and a dodecagonal shape. The detector is optimized for high coincidence rates, at a spatial resolution of 2-3 mm. We present key performance parameters of this detector, determined by the NEMA NU 4-2008 standard, and under the application of an inter-crystal scatter recovery (ICSR) algorithm. Using a coincidence time window of 500ps, energy window of 391-601keV, the STIR FBP3DRP image reconstruction algorithm, and an ICSR with three hits per coincidence within a 5mm radius and a single hit E window of 100-601keV, the following results were achieved: The average spatial resolutions at radial offsets of 5mm, 10mm, 15mm, and 25mm from the axial center are 2.61mm, 2.84mm, 3.20mm, and 3.22mm, respectively. At identical transaxial offsets from a point at one quarter of the axial FOV they are 2.59mm, 3.04mm, 3.12mm, and 3.24mm, respectively. None of the count rate curves reaches a peak. The maximal values for the true, and noise-equivalent count rates are 1864.1kcps, and 1477.1, respectively, for the mouse-like phantom, and 754.6kcps, and 447.8kcps, respectively, for the rat-like phantom, all measured at the highest tested activity of 506.1MBq. The peak sensitivity is 2.30%; the average system sensitivity is 1.02%. We conclude that SAFIR-I delivers excellent count rate performance thanks to its high sensitivity compared to its short FOV and large inner diameter. The apparent lack in spatial resolution was expected for this reconstruction algorithm and detector geometry. The image quality under ICSR and MLEM reconstruction remains to be tested.

SAFIR-II is a high-performance Positron Emission Tomography (PET) insert designed for a Bruker BioSpin 70/30 magnetic resonance imaging (MRI) scanner. It was designed to acquire images for mice and rats within 5 s. This is achieved by minimizing dead-time effects and widening bandwidth limitations, enabling image acquisition at high source activities of up to 500 MBq. Following the "Dual Ring Prototype" and SAFIR-I, SAFIR-II presents the finalized detector design. It employs 11.520 Lutetium-Yttrium oxyorthosilicate (LYSO) crystals (2.0 × 2.0 × 13 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> ) coupled one-to-one to Hamamatsu MPPC S13361-2050 silicon photomultiplier arrays (crystal pitch: 2.0 × 2.0 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> ) to cover an axial field of view of 144.3 mm. The SiPM’s analog signals are digitized using PETA8 Application Specific Integrated Circuits (ASICs), and then read out and transmitted to a DAQ-Computer using an FPGA (Xilinx Kintex7) and an optical 10 GBit Ethernet Link. MR-compatible DC-DC converters and low dropout voltage regulators are used to condition all internal low-voltages. The total power consumption is 558 W.In this work, we present an initial performance evaluation of the PET insert using low and high activity measurements. A point-source measurement at 2.6 MBq yielded a coincidence timing resolution of 217 ps (full width at half maximum (FWHM)) and a coincidence energy resolution of 11.8 % (FWHM, from Gaussian fit). Measuring a line-source phantom at 500 MBq showed a coincidence timing resolution of 277 ps and a coincidence energy resolution of 12.3 %.

This paper describes the main achievements in the development of radiation resistant silicon detectors to be used in the CMS tracker. After a general description of the basic requirements for the operation of large semiconductor systems in the LHC environment, the issue of radiation resistance is discussed in detail. Advantages and disadvantages of the different technological options are presented for comparison. Laboratory measurements and test beam data are used to check the performance of several series of prototypes fabricated by different companies. The expected performance of the final detector modules are presented together with preliminary test beam results on system prototypes.

Abstract The Prototype Synchrotron Radiation Detector (PSRD) is a small-scale experiment designed to measure the rate of low-energy charged particles and photons in near the Earth's orbit. It is a precursor to the Synchrotron Radiation Detector (SRD), a proposed addition to the upgraded version of the Alpha Magnetic Spectrometer (AMS-02). The SRD will use the Earth's magnetic field to identify the charge sign of electrons and positrons with energies above 1 TeV by detecting the synchrotron radiation they emit in this field. The differential energy spectrum of these particles is astrophysically interesting and not well covered by the remaining components of AMS-02. Precise measurements of this spectrum offer the possibility to gain information on the acceleration mechanism and characteristics of all cosmic rays in our galactic neighbourhood. The SRD will discriminate against protons as they radiate only weakly. Both the number and energy of the synchrotron photons that the SRD needs to detect are small. The identification is complicated by the presence of a large particle and photon background. Existing measurements of these backgrounds are insufficient for the construction of the large-scale SRD, so a measurement in space was indispensable. The PSRD was designed to fly as a Space Shuttle secondary payload, within the Shuttle Small Payloads Project. The flight on board the Space Shuttle Endeavour took place from 5 to 17 December 2001. The scientific goal, hardware and the flight of the PSRD are described in this report.

We intend to set up an imaging air Cherenkov telescope with low cost, but high performance design for remote operation. The goal is to dedicate this gamma-ray telescope to long-term monitoring observations of nearby, bright blazars at very high energies (VHE). We will (i) search for orbital modulation of the blazar emission due to supermassive black hole binaries, (ii) study the statistics of flares and their physical origin, and (iii) correlate the data with observations of flares with higher sensitivity telescopes such as MAGIC, VERITAS, and H.E.S.S. Common observations with theWhipple 10m-monitoring telescope will be the first step towards a future 24 h-monitoring of selected sources. This idea was presented for the first time in [1]. The telescope design is based on a full technological upgrade of one of the former telescopes of the HEGRA collaboration, still located at the Observatorio del Roque de los Muchachos on the Canarian Island of La Palma (Spain). After this upgrade, the telescope will be operated robotic, its sensitivity will greatly be improved and a much lower energy threshold below 350GeV will be achieved.

The construction of the lead tungstate crystal calorimeter for the CMS experiment at the Large Hadron Collider (LHC) is close to completion. The barrel part of the calorimeter composed of 61200 crystals is installed and operated inside CMS. Only 102 readout channels are problematic including the 21 entirely dead, corresponding to 0.17 % and 0.034 %, respectively. All 14648 end-cap crystals are mounted. The electronics installation and commissioning of one end-cap has finished and the second will be finished in few weeks. The construction of the pre-shower detectors installed in front of the end-caps is well advanced.

A sampling calorimeter using cerium fluoride scintillating crystals as active material, interleaved with absorber plates made of tungsten, and read out by wavelength-shifting fibres has been tested with high-energy electron beams at the CERN SPS H4 beam line, as well as with lower-energy beams at the INFN Frascati Beam Test Facility in Italy. Energy resolution studies revealed a low stochastic term (<10%/E). This result, combined with high radiation hardness of the material used, marks this sampling calorimeter as a good candidate for the detectors׳ forward regions during the high luminosity phase of LHC.

The Detector Control System of the CMS Electromagnetic Calorimeter has undergone significant improvements during the first LHC Long Shutdown. Based on the experience acquired during the first period of physics data taking of the LHC, several hardware projects were carried out to improve data accuracy, to minimise the impact of failures and to extend remote control possibilities in order to accelerate recovery from problematic situations. This paper outlines the hardware of the detector control and safety systems and explains in detail the requirements, design and commissioning of the new hardware projects.

M. Nothe∗, a M. L. Ahnen b, M. Balbo c, M. Bergmann d , C. Bockermann e, A. Biland b, T. Bretz b, K. A. Brugge a, J. Buss a, D. Dorner d , S. Einecke a, J. Freiwald a, C. Hempfling d , D. Hildebrand b, G. Hughes b, W. Lustermann b, K. Mannheim d , K. Meier d , K. Morik e, S. Muller b, D. Neise b, A. Neronov c, A.-K. Overkemping a, A. Paravac d , F. Pauss b, W. Rhode a, F. Temme a, J. Thaele a, S. Toscano c, P. Vogler b, R. Walter c, and A. Wilbert d Email: maximilian.noethe@tu-dortmund.de

The First G-APD Cherenkov Telescope (FACT) is the first operational telescope of its kind, employing a camera equipped with silicon photon detectors (G-APD aka.SiPM).SiPMs have a high photon detection efficiency (PDE), while being more robust to bright light conditions than the commonly used photo-multiplier tubes.This technology has allowed us to increase the duty cycle beyond that of the current generation of imaging air Cherenkov telescopes.During the last four years, the operation of FACT has proven that SiPMs are a suitable photon detectors for an application in the field of ground-based gamma-ray astronomy.Nevertheless, it has been argued that crosstalk, after-pulses and dark counts are the main drawback of SiPMs, as these effects produce photon-like signals that would add up the signal background.Consequently, it is necessary to understand their impact on the analysis of data from FACT.In this contribution, we will show the current status of a study about the influence of different settings of crosstalk and dark counts on the performance of FACT.For that purpose, Monte Carlo simulations are used and compared to the actual data from the SiPM camera of FACT.

Imaging Air Cherenkov Telescopes, including the First G-APD Cherenkov Telescope (FACT), use segmented reflectors.These offer large and fast apertures for little resources.However, one challenge is the alignment of the mirrors to gain a sharp image.For Cherenkov telescopes, high spatial and temporal resolution is crucial to reconstruct air shower events.Therefore one has to align the individual mirror positions and orientations precisely.Alignment is difficult due to the large number of degrees of freedom and, because most techniques involve a star, has to be done during good weather nights which overlaps with observation time.We present the mirror alignment of FACT, done using two methods.Firstly, we show a new method which we call Bokeh alignment.This method is simple, cheap and can even be done during daytime.Secondly, we demonstrate an enhancement of the SCCAN method by F. Arqueros et al., and first implemented by the McGill VERITAS group.Using a second camera, our enhanced SCCAN is optimized for changing weather, changing zenith distance, and changing reference stars.Developed off site in the lab on a 1/10th scale model of FACT, both our methods resulted in a highly telescope independent procedure, e.g. both our methods run without communication to the telescope's drive.We compare alignment results by using the point spread function of star images, ray tracing simulations, and overall muon rates before and after the alignment.

The CMS electromagnetic calorimeter requires about 113 kW at 2.5 V to power the custom designed readout chips in 0.25 μm technology. The power is converted to low voltage DC at the periphery of the CMS magnet and distributed by copper buses over ∼ 25 m to the detector. Low voltage regulator cards using radiation hard low voltage regulators from CERN/ST microelectronics provide the power to the readout cards. The power is delivered floating and is grounded at the detector end. Several regulator cards were produced and tested.

The CMS experiment at the LHC will comprise a large silicon strip tracker. This article highlights some of the results obtained in the R&D studies for the optimization of its silicon sensors. Measurements of the capacitances and of the high voltage stability of the devices are presented before and after irradiation to the dose expected after the full lifetime of the tracker.

The Very-Front-End cards processing signal from photodetectors of the CMS electromagnetic calorimeter, have been put through extensive test program to guarantee their functionality and reliability.The characteristics of the VFE cards designed for the calorimeter barrel are presented.The results confirm the high quality of the cards production and show that the specifications are fully reached.

The usage of long, axially oriented scintillator crystals in a PET scanner has been shown by the AX-PET Demonstrator as a possible solution for a high resolution and high sensitivity PET detector. In the AX-PET implementation, arrays of wavelength shifting (WLS) strips, placed orthogonally behind every crystal layer, are used to define the axial coordinate. After extensive characterization measurements, the AX-PET Demonstrator has been successfully used for the reconstruction of several phantoms and a few rodents. Possible extensions of the AX-PET concept towards Time Of Flight capabilities have been investigated, using Philips digital SiPMs as alternative photodetector. Promising CRT values equal to 211 ps have been demonstrated, using long crystals with dual sided readout and mean timing method. Finally, we report about an alternative way to reconstruct the axial coordinate: exploiting the light sharing of 100 mm long crystals with special surface treatment resulted in axial resolutions of the order of 4 mm FWHM.

The First G-APD Cherenkov Telescope (FACT) became operational at La Palma in October 2011. Since summer 2012, due to very smooth and stable operation, it is the first telescope of its kind that is routinely operated from remote, without the need for a data-taking crew on site. In addition, many standard tasks of operation are executed automatically without the need for manual interaction. Based on the experience gained so far, some alterations to improve the safety of the system are under development to allow robotic operation in the future. We present the setup and precautions used to implement remote operations and the experience gained so far, as well as the work towards robotic operation.

This paper presents the Detector Control System (DCS) designed and implemented for the Electromagnetic Calorimeter (ECAL) of the Compact Muon Solenoid (CMS) experiment at CERN. The focus is on its distributed controls software architecture, the deployment of the application into production and its integration into the overall CMS DCS. The knowledge acquired from operational issues during the detector commissioning and the first phase of the Large Hadron Collider (LHC) physics runs is discussed and future improvements are presented.

The first long shutdown of the Large Hadron Collider (LS1, 2013-2015) provided an opportunity for significant upgrades of the detector control and safety systems of the CMS Electromagnetic Calorimeter. A thorough evaluation was undertaken, building upon experience acquired during several years of detector operations. Substantial improvements were made to the monitoring systems in order to extend readout ranges and provide improved monitoring precision and data reliability. Additional remotely controlled hardware devices and automatic software routines were implemented to optimize the detector recovery time in the case of failures. The safety system was prepared in order to guarantee full support for both commercial off-the-shelf and custom hardware components throughout the next accelerator running period. The software applications were modified to operate on redundant host servers, to fulfil new requirements of the experiment. User interface extensions were also added to provide a more complete overview of the control system. This paper summarises the motivation, design, implementation and validation of the major improvements made to the hardware and software components during LS1. Presented at ICALEPCS 2015 15th International Conference on Accelerator and Large Experimental Physics

The High-Luminosity phase of the Large Hadron Collider at CERN (HL-LHC) poses stringent requirements on calorimeter performance in terms of resolution, pileup resilience and radiation hardness. A tungsten-CeF <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> sampling calorimeter is a possible option for the upgrade of current detectors. A prototype, read out with different types of wavelength-shifting fibers, has been built and exposed to high energy electrons, representative for the particle energy spectrum at HL-LHC, at the CERN SPS H4 beam line. This paper shows the performance of the prototype, mainly focussing on energy resolution and uniformity. A detailed simulation has been also developed in order to compare with data and to extrapolate to different configurations to be tested in future beam tests. Additional studies on the calorimeter and the R&D projects ongoing on the various components of the experimental setup will be also discussed.

The First G-APD Cherenkov Telescope (FACT), located on the Canary Island of La Palma, has been taking data since October 2011. FACT has been optimized for longterm monitoring of bright TeV blazars, to study their variability time scales and flare probability. G-APD photo-sensors allow for observations even under strong moonlight conditions, and the telescope can be operated remotely. The monitoring strategy of FACT is discussed and preliminary results of the flare of Mrk501 in June 2012 are shown.

Within the FACT project, we construct a new type of camera based on Geiger-mode avalanche photodiodes (G-APDs). Compared to photomultipliers, G-APDs are more robust, need a lower operation voltage and have the potential of higher photon-detection efficiency and lower cost, but were never fully tested in the harsh environments of Cherenkov telescopes. The FACT camera consists of 1440 G-APD pixels and readout channels, based on the DRS4 (Domino Ring Sampler) analog pipeline chip and commercial Ethernet components. Preamplifiers, trigger system, digitization, slow control and power converters are integrated into the camera.

AX-PET is a novel PET concept based on long crystals axially arranged and orthogonal Wavelength shifter (WLS) strips, both individually readout by Geiger-mode Avalanche Photo Diodes (G-APD). Its design was conceived in order to reduce the parallax error and simultaneously improve spatial resolution and sensitivity. The assessment of the AX-PET concept and potential was carried out through a set of measurements comprising individual module characterizations and scans in coincidence mode of point-like and extended sources. The estimated energy and spatial resolutions from point-like measurements are R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">FWHM</sub> =11.6% (at 511 keV) and 1.7-1.9 mm (FWHM) respectively as measured with point-like sources placed in different positions of the FOV. First results from scans of extended phantoms confirmed our expectations.

Abstract A Synchrotron Radiation Detector measures synchrotron radiation emitted by high energetic particles in the earth magnetic field. This allows to identify cosmic ray electrons and positrons with energies in the TeV region. One possibility for such a detector outside the atmosphere uses YAP crystals to measure synchrotron photons with energies in the keV range. As such a detector can not distinguish between photons and electrons, the main problems are the diffuse cosmic ray gamma background and low energetic electrons in the vicinity of the earth. While the intensity of the diffuse gamma rays is known quite well, there exists limited knowledge about keV-electrons in low earth orbits. To measure these electrons a Prototype Synchrotron Radiation Detector (PSRD) was flown with Space Shuttle mission STS-108 (Dec.2001) and preliminary analysis of the data show very favorable results.

Detection of scintillation light from LSO (Lutetiumoxyorthosilicate) crystals used in positron emission tomography (PET) is traditionally based on photo-multipliers.The proposal is to develop a novel photo-sensor, which is based on vertically integrating an hydrogenated amorphous silicon (a-Si:H) film on a pixel readout chip.The a-Si:H film is deposited with a n-i-p diode structure.The ASIC (Application Specific Integrated Circuit) performs both signal amplification and readout processing.The advantage of such an approach is the extremely compact and low-cost design, together with ultra-low noise signal retrieval.In addition the a-Si:H offers the technological advantage of direct deposition on the wafer thanks to the low deposition temperature.The article presents the results of quantum efficiency measured on different types of a-Si:H photodiodes deposited on glass (DC measurement) and CMOS circuit (AC measurement).Quantum Efficiency (QE) up to 80% has been measured at the wavelength of interest for the optimized photodiodes.