Z. Szillási

One of the fundamental advantages in the employment of the Fiber Bragg Grating (FBG) sensors lies in their capability to allow measurements in extreme environmental conditions with also very high immunity toward external electromagnetic interference factors. The behavior of a polymer-coated FBG sensor, tested in cryogenic conditions at the laboratories of the European Organization for the Nuclear Research (CERN) in Geneva, has been analyzed and will be discussed in this paper. Magnets used in the Large Hadron Collider (LHC) for the High Energy Physics Researches at CERN need in fact extreme cooling conditions to preserve the internal superconductivity highly crucial for their performances. The magnets, built with NbTi based superconductors, are cooled with liquid helium and they operate at 1.9 K. The aim of the present work is to estimate the thermal expansion coefficient of two polymers based on epoxy and methacrylate (PMMA) used as coating of FBGs, in the temperature range from 4 K to 300 K and to check their suitability for the use in temperature monitoring of the superconducting magnets. A standard numerical derivative method has been employed to estimate thermal expansion coefficients; moreover the correlated fluctuation analysis (CFA) based procedure is proposed, as a reliable alternative, to overcome numerical derivative drawbacks at very low temperatures within the range of 4–20 K. The calculated values of thermal expansion coefficient for both systems are in agreement with literature data on similar material.

This work investigates the performance and the radiation hardness capability of optical thermo-hygrometers based on Fibre Bragg Gratings (FBG) for humidity monitoring in the Compact Muon Solenoid (CMS), one of the four experiments running at CERN in Geneva. A thorough campaign of characterization was performed on 80 specially produced Polyimide-coated RH FBG sensors and 80 commercial temperature FBG sensors. Sensitivity, repeatability and accuracy were studied on the whole batch, putting in evidence the limits of the sensors, but also showing that they can be used in very dry conditions. In order to extract the humidity measurements from the sensor readings, commercial temperature FBG sensors were characterized in the range of interest. Irradiation campaigns with ionizing radiation (γ-rays from a Co60 source) at incremental absorbed doses (up to 210 kGy for the T sensors and up to 90 kGy for the RH sensors) were performed on sample of T and RH-Sensors. The results show that the sensitivity of the sensors is unchanged up to the level attained of the absorbed dose, while the natural wavelength peak of each sensor exhibits a radiation-induced shift (signal offset). The saturation properties of this shift are discussed.

Production of neutrinos is abundant at LHC. Flavour composition and energy reach of the neutrino flux from proton-proton collisions depend on the pseudorapidity $\eta$. At large $\eta$, energies can exceed the TeV, with a sizeable contribution of the $\tau$ flavour. A dedicated detector could intercept this intense neutrino flux in the forward direction, and measure the interaction cross section on nucleons in the unexplored energy range from a few hundred GeV to a few TeV. The high energies of neutrinos result in a larger $\nu$N interaction cross section, and the detector size can be relatively small. Machine backgrounds vary rapidly while moving along and away from the beam line. Four locations were considered as hosts for a neutrino detector: the CMS quadruplet region (~25 m from CMS Interaction Point (IP)), UJ53 and UJ57 (90 and 120 m from CMS IP), RR53 and RR57 (240 m from CMS IP), TI18 (480 m from ATLAS IP). The potential sites are studied on the basis of (a) expectations for neutrino interaction rates, flavour composition and energy spectrum, (b) predicted backgrounds and in-situ measurements, performed with a nuclear emulsion detector and radiation monitors. TI18 emerges as the most favourable location. A small detector in TI18 could measure, for the first time, the high-energy $\nu$N cross section, and separately for $\tau$ neutrinos, with good precision, already with 300 fb$^{-1}$ in the LHC Run3.

The i-pipe system is a peculiar structural health monitoring system, based on Fiber Bragg Grating technology, installed on the central beam pipe of the compact Muon solenoid (CMS) experiment at CERN. In this contribution, i-pipe temperature sensors, originally conceived as thermal compensator for the strain sensors, are employed to monitor central beam pipe thermal behavior in correlation with the parameters of the particle beam travelling inside, in order to directly measure possible Beam RF induced heating effect. The i-pipe system turned out to be capable of monitoring, directly and without interference, the parameters of the particle beam circulating in the LHC ring. Hence, the results presented in this work pave the way to the use of the i-pipe as monitoring system of an accelerated high energy particle beam.

In this contribution we present results concerning the very first application of fiber optic sensors (FOSs) for relative humidity (RH) monitoring in high radiations environments. After a few years of investigations at CERN in Geneva, since December 2013 our multidisciplinary research group has successfully installed 72 thermo-hygrometers based on Fiber Bragg Grating (FBG) technology, organized in multi-points arrays, in cold areas of the Tracker Bulkhead of the Compact Muon Solenoid (CMS) experiment, where hundreds of electrical connectors are housed and thousands of services, including many cold pipes, cross the volumes through them. In such a complicated environment, a constant hygrometric monitoring is vital, in order to avoid dangerous phenomena of condensation. The collected results in the last year of operation of the proposed sensors are effective and reliable, with temperature, relative humidity and dew point temperature measurements from the FBG-based devices in full agreement with the readings of conventional sensors, temporarily present in the detector. However, experience in operation has shown some limitations of this technology, which are fully detailed in the last section of the paper.

In this paper we describe the main characteristics and experimental results, recorded in more than four years of data acquisition, of a temperature and strain monitoring system, called i-pipe, based on Fiber Bragg Grating (FBG) sensors arrays applied for the first time to a sector of the Large Hadron Collider (LHC) at the European Organization for Nuclear Research (CERN): the central beam pipe (BP) of the Compact Muon Solenoid (CMS). The monitoring system, consisting of four arrays of 16 FBG sensors each, as better described in the text, is placed on four directives of the LHC section that passes inside the CMS experiment, namely the CMS central BP. The mechanical complexity of the central BP structure is described and the monitoring results of its thermal conditions and online unpredictable mechanical deformations are discussed in this paper. In spite of the harsh working conditions this monitoring system is operational since 2015 continuously (24/7) and the data collected are a confirmation of its reliability. This FBG sensors system represents the ideal solution to realize an accurate and robust sensing system to be used in harsh environments, like the CMS experimental facility and all the other High Energy Physics experimental infrastructures.

In this work, experimental tests of a full analog fiber optic monitoring system are reported. The proposed concept is conceived to satisfy the constrains imposed to be used for safety application, in terms of robustness and reliability, due to full passive optical devices and an analog-based circuitry. Moreover, it is compatible with the stringent requirements imposed by the Detector Safety System (DSS) of the Compact Muon Solenoid (CMS) experiment at CERN. From the optical side, the main device is the Arrayed Waveguide Grating (AWG), with the aim to filter and address the optical signal through a determined output channel, that is then transduced in electrical by means of a photodiode. From the electronic side, the designed board has the purpose to manipulate the signal in order to have an increasing monotone output current, in the range 4-20 mA, standard widely employed in safety system environment. In this way, the circuit gain can be set in order to match the value to the physical quantity under monitoring threshold. To give proof of its characteristics, the system is subjected to many test led at CERN, in which two Fiber Bragg Grating (FBG) sensors are under test into a custom climate box. Step temperature variation, as well as fast oscillating test and long term stability measurement are reported, confirming its key strength and field-validating it.

In the field of accelerator physics it is crucial to account for heating caused by the passage of high intensity beams into accelerator components. This phenomenon is known as Radio Frequency (RF) Beam Induced Heating (BIH) and requires, other than an accurate design stage, to constantly monitor temperature-related parameters during the accelerator operations. This enables to warn for critical malfunctions and to prevent possible damages. Monitoring needs to meet various requirements, such as multiplexing capabilities, distributed sensing possibilities, and robustness in harsh environments. Fiber Bragg Grating sensors (FBGs) have been proven to be an ideal solution that meets all these requirements. This study aims to validate the use of FBGs for direct measurement of RF BIH. A section of the beam pipe in the CERN Large Hadron Collider was modeled in terms of impedance, and the resulting RF BIH was computed based on the traveling beam. The results of the numerical simulation were compared with experimental data obtained by FBGs installed along the beam pipe. The analysis shows that FBGs can be a valuable beam diagnostic tool for monitoring accelerated high energy particle beams by measuring RF BIH and may provide useful insights for improving the design and operation of future accelerators. The study highlights the significant advancements of FBG technology in direct temperature measurement and assessment of RF BIH and serves as a promising solution for mitigating RF BIH in the demanding environment of particle accelerators.

Abstract We discuss an experiment to investigate neutrino physics at the LHC, with emphasis on tau flavour. As described in our previous paper Beni et al (2019 J. Phys. G: Nucl. Part. Phys. 46 115008), the detector can be installed in the decommissioned TI18 tunnel, ≈480 m downstream the ATLAS cavern, after the first bending dipoles of the LHC arc. The detector intercepts the intense neutrino flux, generated by the LHC beams colliding in IP1, at large pseudorapidity η , where neutrino energies can exceed a TeV. This paper focuses on exploring the neutrino pseudorapity versus energy phase space available in TI18 in order to optimize the detector location and acceptance for neutrinos originating at the pp interaction point, in contrast to neutrinos from pion and kaon decays. The studies are based on the comparison of simulated pp collisions at <?CDATA $\sqrt{s}=$?> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"> <mml:msqrt> <mml:mrow> <mml:mi>s</mml:mi> </mml:mrow> </mml:msqrt> <mml:mo>=</mml:mo> </mml:math> 13 TeV: PYTHIA events of heavy quark (c and b) production, compared to DPMJET minimum bias events (including charm) with produced particles traced through realistic LHC optics with FLUKA. Our studies favour a configuration where the detector is positioned off the beam axis, slightly above the ideal prolongation of the LHC beam from the straight section, covering 7.4 &lt; η &lt; 9.2. In this configuration, the flux at high energies (0.5–1.5 TeV and beyond) is found to be dominated by neutrinos originating directly from IP1, mostly from charm decays, of which ≈50% are electron neutrinos and ≈5% are tau neutrinos. The contribution of pion and kaon decays to the muon neutrino flux is found small at those high energies. With 150 fb −1 of delivered LHC luminosity in Run 3 the experiment can record a few thousand very high energy neutrino charged current (CC) interactions and over 50 tau neutrino CC events. These events provide useful information in view of a high statistics experiment at HL–LHC. The electron and muon neutrino samples can extend the knowledge of the charm PDF to a new region of x , which is dominated by theory uncertainties. The tau neutrino sample can provide first experience on reconstruction of tau neutrino events in a very boosted regime.

In this paper, the results of the long-term temperature monitoring of the compact muon solenoid experiment (CMS) at CERN are shown. The measurements were carried out by means of a system based on fiber Bragg grating (FBG) sensors in wavelength-division multiplexing (WDM). Due to the harsh working conditions at the CMS, the FBG sensor represents the ideal candidate to realize a reliable and accurate sensing system. The sensing principles of the FBG sensor and its temperature characteristics are introduced. A temperature monitoring system based on FBG for high-energy physics applications is designed and installed. The sensing system was used successfully last year in monitoring the temperature of CMS bulkhead. The reported results show good reliability and high accuracy of the FBG sensing system during the long-time working stage.

Results are presented on the activity carried out by our research group, in collaboration with the SME Optosmart s.r.l. (an Italian spin-off company), on the application of Fiber Optic Sensor (FOS) techniques to monitor high-energy physics (HEP) detectors. Assuming that Fiber Bragg Grating sensors (FBGs) radiation hardness has been deeply studied for other field of application, we have applied the FBG technology to the HEP research domain. We present here the experimental evidences of the solid possibility to use such a class of sensors also in HEP detector very complex environmental side conditions. In particular we present more than one year data results of FBG measurements in the Compact Muon Solenoid (CMS) experiment set up at the CERN, where we have monitored temperatures (within CMS core) and strains in different locations by using FBG sensors during the detector operation with the Large Hadron Collider (LHC) collisions and high magnetic field. FOS data and FOS readout system stability and reliability is demonstrated, with continuous 24/24 h 7/7d data taking under severe and complex side conditions.

This document describes results obtained from the Link alignment system data recorded during the Compact Muon Solenoid (CMS) Magnet Test. A brief description of the system is followed by a discussion of the detected relative displacements (from micrometres to centimetres) between detector elements and rotations of detector structures (from microradians to milliradians). Observed displacements are studied as functions of the magnetic field intensity. In addition, the reconstructed positions of active element sensors are compared to their positions as measured by photogrammetry and the reconstructed motions due to the magnetic field strength are described.

The results of structural and thermal monitoring of the Compact Muon Solenoid (CMS) experiment in the underground site at CERN will be reported. The measurements are carried out by means of Fiber Bragg Grating sensor arrays installed on the CMS detector, from the inner to the outer regions. This fiber optic monitoring system represents the ideal solution to secure a reliable and accurate sensing system to be used 24/7 in the harsh environment at CERN

After the Phase-2 high-luminosity upgrade to the Large Hadron Collider (LHC), the collision rate and therefore the background rate will significantly increase, particularly in the high $\eta$ region. To improve both the tracking and triggering of muons, the Compact Muon Solenoid (CMS) Collaboration plans to install triple-layer Gas Electron Multiplier (GEM) detectors in the CMS muon endcaps. Demonstrator GEM detectors were installed in CMS during 2017 to gain operational experience and perform a preliminary investigation of detector performance. We present the results of triple-GEM detector performance studies performed in situ during normal CMS and LHC operations in 2018. The distribution of cluster size and the efficiency to reconstruct high $p_T$ muons in proton--proton collisions are presented as well as the measurement of the environmental background rate to produce hits in the GEM detector.

XSEN (Cross Section of Energetic Neutrinos) is a small experiment designed to study, for the first time, neutrino-nucleon interactions (including the tau flavour) in the 0.5-1 TeV neutrino energy range. The detector will be installed in the decommissioned TI18 tunnel and uses nuclear emulsions. Its simplicity allows construction and installation before the LHC Run 3, 2021-2023; with 150/fb in Run3, the experiment can record up to two thousand neutrino interactions, and up to a hundred tau neutrino events. The XSEN detector intercepts the intense neutrino flux, generated by the LHC beams colliding in IP1, at large pseudo-rapidities, where neutrino energies can exceed the TeV. Since the neutrino-N interaction cross section grows almost linearly with energy, the detector can be light and still collect a considerable sample of neutrino interactions. In our proposal, the detector weighs less than 3 tons. It is lying slightly above the ideal prolongation of the LHC beam from the straight section; this configuration, off the beam axis, although very close to it, enhances the contribution of neutrinos from c and b decays, and consequently of tau neutrinos. The detector fits in the TI18 tunnel without modifications. We plan for a demonstrator experiment in 2021 with a small detector of about 0.5 tons; with 25/fb, nearly a hundred interactions of neutrinos of about 1 TeV can be recorded. The aim of this pilot run is a good in-situ characterisation of the machine-generated backgrounds, an experimental verification of the systematic uncertainties and efficiencies, and a tuning of the emulsion analysis infrastructure and efficiency. This Letter provides an overview of the experiment motivations, location, design constraints, technology choice, and operation.

Magnet Cycles and Stability Periods of the CMS Experiment are studied with the Alignment Link System data recorded along the 2008–2013 years of operation. The motions of the mechanical structures due to the magnetic field forces are studied and the mechanical stability of the detector during the physics data taking periods is verified.

A study of the time required for the CMS detector to reach structural equilibrium once the magnetic field is ramped to its operational value of 3.8 T is presented. In addition, the results from a stability monitoring at 3.8 T over an eight-month period are given.

This paper provides an extensive overview of more than a decade of continuous data collected by the Fiber Optic Sensing for CMS (FOS4CMS) network, featuring over 1000 Fiber Bragg Grating (FBG) sensors. These FBG sensors have been instrumental in monitoring temperature and strain within the Compact Muon Solenoid (CMS) experiment at the Large Hadron Collider (LHC). Their strategic placement allowed for observation of crucial components, including the central beam pipe, silicon tracker, RPC muon detectors, and the underground cavern. Operational since 2009, the monitoring system underwent expansions during LHC Long Shutdowns (LS1 and LS2) and upgrades for LHC Run3. Leveraging Wavelength Division Multiplexing, the FBG sensors demonstrated reliability, seamlessly integrating into the CMS Detector Control System. In summary, the presented data robustly affirm the resilience of FBG sensors in the challenging High Energy Physics environment, with the FOS4CMS system's uninterrupted 24/7 operation over a decade marking a significant milestone in the successful application of FBG technology within the CMS experiment at CERN.

Particle accelerators, such as the Large Hadron Collider (LHC) at CERN, are planning to increase the intensity of circulating particle beams. However, this upgrade faces challenges due to beam-induced heating that can lead to operational issues and component damage. To address this, suitable monitoring systems are required. Fiber Optic Sensing using Fiber Bragg Gratings (FBGs) has gained popularity in the High Energy Physics domain. This study focuses on iPipe, a monitoring system based on FBGs installed in the Compact Muon Solenoid experiment since 2015. FBG sensors offer advantages such as immunity to optoelectronic noise, intensity modulation, and radiation-induced losses. The iPipe system was recently upgraded and is currently acquiring data during LHC Run 3. The initial analysis of this data is presented in this paper.

A calibration method for fiber Bragg grating (FBG) cryogenic temperature sensors based on look-up-table was proposed and demonstrated experimentally. The operating principles of different kind of FBG cryogenic temperature sensors are introduced. A statistical characterization of the data was carried out to verify the quasi-static condition of the measurement system by checking the stability of the measurement. Once verified this condition, the sensitivity curves of the sensors were determined by correlating the wavelength shift of the FBGs with the reference sensor measurements. On the basis of the sensitivity curves, the look-up-table (LUT) have been determined. The experimental data shows that the LUT fitting approach provides good and reliable performance in terms of accuracy and processing time.

The central feature of the CMS Link alignment system is a network of Amorphous Silicon Position Detectors distributed throughout the muon spectrometer that are connected by multiple laser lines. The data collected during the years from 2008 to 2015 is presented confirming an outstanding performance of the photo sensors during more than seven years of operation. Details of the photo sensor readout of the laser signals are presented. The mechanical motions of the CMS detector are monitored using these photosensors and good agreement with distance sensors is obtained.

An estimate of environmental background hit rate on triple-GEM chambers is performed using Monte Carlo (MC) simulation and compared to data taken by test chambers installed in the CMS experiment (GE1/1) during Run-2 at the Large Hadron Collider (LHC). The hit rate is measured using data collected with proton-proton collisions at 13 TeV and a luminosity of 1.5$\times10^{34}$ cm$^{-2}$ s$^{-1}$. The simulation framework uses a combination of the FLUKA and Geant4 packages to obtain the hit rate. FLUKA provides the radiation environment around the GE1/1 chambers, which is comprised of the particle flux with momentum direction and energy spectra ranging from $10^{-11}$ to $10^{4}$ MeV for neutrons, $10^{-3}$ to $10^{4}$ MeV for $\gamma$'s, $10^{-2}$ to $10^{4}$ MeV for $e^{\pm}$, and $10^{-1}$ to $10^{4}$ MeV for charged hadrons. Geant4 provides an estimate of detector response (sensitivity) based on an accurate description of detector geometry, material composition and interaction of particles with the various detector layers. The MC simulated hit rate is estimated as a function of the perpendicular distance from the beam line and agrees with data within the assigned uncertainties of 10-14.5%. This simulation framework can be used to obtain a reliable estimate of background rates expected at the High Luminosity LHC.

The World Year of Physics offers an opportunity to amuse secondary school pupils by experiments that they can perform themselves. The experiment described in this article enables them to visualize the invisible world of nuclear particles. The applied detector is particularly suited for classroom experiments.

In recent years various educational activities have been pursued in Hungary with the aim to raise the interest of high school students in natural sciences, and especially in physics. This brief summary will present some of the key projects of broader interest for the scientific community.

Advances in information and communications technologies (ICTs) have given rise to innovative uses of web-based video tools for global communication, enhancing the impact of large research facilities,including their outreach and education programmes.As an example, the Virtual Visits programmes developed by the ATLAS and CMS collaborations at CERN, use videoconferencing to communicate with schools and remote events around the globe.The goal of these programmes is to enable the public, especially young people, to become engaged in and understand the field of particle physics through direct dialogue between ATLAS/CMS scientists and remote audiences.

The CMS Muon Barrel Alignment system uses cameras mounted on 36 rigid MAB structures to monitor DT positions. During the 2010 and 2011 data-taking periods, 4 such MABs became inoperative. This study shows that the resulting loss of information does not cause a significant degradation of the reconstructed DT positions.

The CMS Muon Barrel Alignment system uses cameras mounted on 36 rigid MAB structures to monitor DT positions. During the 2010 and 2011 data-taking periods, 4 such MABs became inoperative. This study shows that the resulting loss of information does not cause a significant degradation of the reconstructed DT positions.

During the past years our group has built, calibrated, and finally installed all the components of the Muon Barrel Alignment System for the CMS experiment. This paper covers the results of the hardware commissioning, the full system setup and the connection to the CMS Detector Control System (DCS). The step-by-step operation of the system is discussed: from collecting the analog video signals and preprocessing the observed LED images, through controlling the front-end PCs, to forming the measurement results for the CMS DCS. The first measurement results and the initial experiences of the communication with the DCS are also discussed.

In this study, a novel monitoring system based on fiber optic technology is investigated. It is based on a full analog electronic circuitry and full passive optical devices, allowing to increase its robustness and reliability, without losing in terms of measurement accuracy. Due to these peculiarities, the conceived system satisfies the constrains imposed by the detector safety systems, a dedicated section in charge to control and handle anything is related to the equipment protection of experimental apparatus like the Large Hadron Collider (LHC) experiment at CERN. Experimental tests of the proposed system have been conducted in laboratory environment and the results, in terms of temperature variation, are shown. Two Fiber Bragg Grating sensors under test are employed, monitoring a deviation of 20°C with 1°C step, simulating a possible scenario in which the system will be employed in the next months.

Az OTKA altal tamogatott kutatas ket teruletre bonthato. I. A BNL RHIC gyorsitojanak PHENIX kiserleteben a meresekben es a kiserleti adatok analiziseben valo reszvetel: Csoportunk a PHENIX kollaboracio tagjakent dolgozott, munkaja beepult a PHENIX kiserlet kozos eredmenyeibe. Nehany teruleten a csoport hozzajarulasa kulonosen jelentős volt. Igy kiemelendő a jet-elnyomas jelensegenek vizsgalata kulonboző energiaju nehezion utkozesekben illetve az elektreomagneses kalorimeterrel kapcsolatos szimulacios es kalibracios tevekenyseg. II. Reszvetel a CERN-i LHC CMS kiserletenek epiteseben, ezen belul a barrel muon kamrak helyzetmeghatarozo rendszerenek fejlesztese es letrehozasa: a palyazati időszak alatt megepitesre kerult a teljes rendszer, amely lehetőve teszi a CMS barrel muon spektrometeret alkoto 250 nagymeretű driftkamra helyzetenek meghatarozasat szubmillimeteres pontossaggal. | The research activity supported by the OTKA fund can be divided in two groups. I. Participation in the measurements and the physics analysis of the PHENIX experiment at the RHIC accelerator in BNL (USA): our group worked in close collaboration with other members of the experiment so its work was integrated in the common results of the whole collaboration. In some areas, however, the contribution was particularly significant. Two areas can be emphasized, the investigation of jet suppression in heavy ion collisions at different energies and the simulation and calibration of the electromagnetic calorimeter. II. Participation in the construction of the CMS experiment to be installed at the LHC accelerator (CERN, Switzerland), development and construction of the barrel muon position monitoring system: the full system has been completed during the period of the OTKA-support. It allowes us to determine the positions of 250 large-scale drift-chambers forming the barrel muon spectrometer with submillimeter accuracy.

In the last year as part of the first test of the CMS experiment at CERN [1] called Magnet Test and Cosmic Challenge (MTCC) about 25% of the barrel muon position monitoring system was built and operated. The configuration enabled us to test all the elements of the system and its function in real conditions. The correct operation of the system has been demonstrated. About 500 full measurement cycles have been recorded. In the paper the setup –including the read-out and control is described and the first preliminary results are presented.

In order to be able to match correctly the track elements produced by a muon in the Tracker and the Muon System of the CMS experiment [1] the mutual alignment precision between the Tracker and the Barrel Muon System must be no worse than 100-400 micrometers depending on the radial distance of the muon chambers from the Tracker. To fulfill this requirement an alignment system had to be designed. This system contains subsystems for determining the positions of the barrel and endcap chambers while a third one connects these two to the Tracker. Since the Barrel muon chambers are embedded into the magnet yoke of the experiment a nonconventional alignment method had to be developed. In this paper we restrict ourselves to the Barrel Alignment System and the calibration methods of its components. I. THE BARREL MUON ALIGNMENT SYSTEM The CMS Barrel Muon Alignment System (Fig. 1) is based on an optical network of LED light sources and videocameras. The full system contains very large number of cameras (approx. 600 pcs) and LEDs (approx. 10000 pcs). Overwhelming part of these LEDs are mounted on the 250 barrel muon chambers while the cameras observing these LEDs are mounted on rigid structures called MABs (Module for Alignment of the Barrel). The MABs (36 pieces altogether) are fixed on the iron yoke of the magnet. Furthermore, there are about 300 LEDs and 100 cameras making direct connections between the MABs (called diagonal connections). Finally there are 6 long carbon-fiber bars located inside the barrel muon system containing in total 144 LED light sources allowing direct measurement of the Z coordinates of 24 MABs (where Z direction in the experiment corresponds to the direction of the proton beam path). The results of individual measurements are the positions of the centroids of the images of the LEDs measured by the cameras. In order to be able to reconstruct the positions of the muon chambers additional data -in addition to the measured centroidsis required. These are the parameters of the cameras (magnification, and tilt angles of the sensor with respect to the optical axis of the camera, sensitivity and homogeneity of the video-sensors of the cameras) and the positions of the LEDs on their holders. Also, the positions of the cameras and the LED holders in their embedding objects (muon chambers, MABs, Z-bars) are also needed. These additional data are obtained by the calibration of the elements. Figure 1. CMS Barrel Muon Alignment scheme II. CALIBRATION OF THE COMPONENTS The main requirement on the muon chamber alignment precision is in the range of 100-400 microns. Since this value depends also on the calibration precision of the components, the calibration methods had to be established such that the resulted precision of the full system could meet the above mentioned requirements. The individual calibration steps of the light source-related objects are the LED holder calibration and the barrel muon chamber alignment calibration, while calibration steps of the camera related objects are the camera quality control, the camera calibration and the MAB calibration. A. Light source related objects As it is mentioned above the basic components of the Barrel Muon Alignment System are the LEDs and the cameras. Individual LEDs are grouped into mechanical structures called LED holders containing 10 (for DT chambers), 3 (diagonal LED holders) or 6 (Z-LED holders) LEDs according to the measurement type. During the calibration process positions of the LED centroids in the frame of the LED holder are determined. The optical network requires most of the LED holders to be observed from both sides. This can be solved by introducing an auxiliary frame of reference which can be seen from both sides. Technically, this is a calibration tool containing multimode optical fibers illuminated by noncoherent light sources and shining into both directions. Positions of these light sources are measured in a high precision metrology lab and produce light distributions similar to those of the LEDs to be measured. Since the light spots are observed by cameras there was a requirement to exclude geometrical distortions and the error on centroid calculation caused by the un-even gain on the sensor surface. This has been solved by mounting the calibration tool (and therefore the LED holders) on a precise two-dimensional moving table and by constructing a successive method for moving all the centroids to a predefined position on the sensor surfaces. Therefore LED positions correspond to the position readouts of the moving table. Figure 2. Calibration bench for the LED holders. As the amount of LED holders is very large (>1200 pieces) a highly automated measurement method had to be developed. Both the successive centroid measurements and the control of the moving table and the LED holders are computerized. The operator only has to change the LED holders, identify it and start the measurement. The successive status then can be monitored on the computer console. Also due to the large number of LED holders an effective way of data handling and storage had to be developed. For such a large number of data (five complete measurements of all the LED holders ~ 100 k lines of raw data + 20 k lines of analyzed data) the use of a commercially available database solution is inevitable. Our team decided to use MySQL because it supports all the programming languages used in this calibration process under all operating systems. This database server also had an advantage because its installation requires only a moderate disk space and it is also freely available for research purposes. For data security reasons measurements are recorded as ASCII files which are automatically uploaded as the measurement finishes. Therefore one can assure to have two identical copies of the raw data and in case of critical failure of the database server data can be recuperated by using the same method used for synchronizing the database to the ASCII files. However, storage of data in a relational database provides a very easy way to compare the individual measurements therefore pinpointing any measurement errors based on statistical methods. This statistical analysis and the data recuperation are done by web-based Perl scripts allowing the access to the data from virtually everywhere without the need for special data handling software. Calibration methods of the diagonal and Z-LED holders are very similar to that of those ones described above. Figure 3. Data flow during the LED holder calibration [5] The main goal of the alignment system is to locate the anode wires of the muon chambers with respect to the Tracker. Muon chambers have a construction which doesn’t allow the observation of their anode wires after construction. This construction doesn’t allow either to determine the LED holder’s position with respect to the wires during chamber building. To overcome this problem the following technology has been developed: 1. During construction position of every anode wire (approx. 400 per chamber) is measured during the construction with respect to mechanical reference objects known as corner blocks mounted on each corner of a muon chamber’s Super Layer [2] (4 pieces per Super Layer). Since a muon chamber consists of two or three Super Layers depending on its type, a muon chamber can have eight or twelve corner blocks in total. These corner blocks serve as position references. 2. Since the position measurement of the LED holders is based on a centroid measurement while positions of the corner blocks can be determined by standard survey techniques (photogrammetry) an additional calibration bench had to be built. Here the corner blocks can be located by photogrammetry and the LED holders mounted on the chambers can be measured by cameras with pre-calibrated (known) positions with respect to the calibration bench. For this pre-calibration a specially designed calibration plate containing both optical fiber light sources and target holes for the photogrammetry is used. Internal parameters of these plates could be determined by a metrology laboratory. During the precalibration of the chamber bench these plates are localized by photogrammetry while a simultaneous measurement of the optical fibers has been performed by the cameras. A geometrical reconstruction is able to recuperate both the camera positions and their internal parameters needed for a correct measurement of the LED holders. 3. Applying mathematical transformations the positions of the LED holders can be determined in the chamber’s frame. As a byproduct the localization of all the Super Layers in the chamber’s frame can also be performed. The number of muon chambers to be measured was 264, therefore this calibration step also requires a reliable data handling strategy. Since during LED holder calibration the LED Holder Calibration

This document presents an overview of the induced photocurrents in the Amorphous Silicon Position Detectors used in the network of diode lasers and photo sensors of the CMS Link alignment system recorded during its eleven years of operation. After a description of the sensors characteristics, the layout of the sensors network is discussed. The sensors are distributed throughout the muon spectrometer and connected by laser lines. The data used correspond to readout information obtained during some of the physics runs from 2008 to 2018.

XSEN (Cross Section of Energetic Neutrinos) is a small experiment designed to study, for the first time, neutrino-nucleon interactions (including the tau flavour) in the 0.5-1 TeV neutrino energy range. The detector will be installed in the decommissioned TI18 tunnel and uses nuclear emulsions. Its simplicity allows construction and installation before the LHC Run 3, 2021-2023; with 150/fb in Run3, the experiment can record up to two thousand neutrino interactions, and up to a hundred tau neutrino events. The XSEN detector intercepts the intense neutrino flux, generated by the LHC beams colliding in IP1, at large pseudo-rapidities, where neutrino energies can exceed the TeV. Since the neutrino-N interaction cross section grows almost linearly with energy, the detector can be light and still collect a considerable sample of neutrino interactions. In our proposal, the detector weighs less than 3 tons. It is lying slightly above the ideal prolongation of the LHC beam from the straight section; this configuration, off the beam axis, although very close to it, enhances the contribution of neutrinos from c and b decays, and consequently of tau neutrinos. The detector fits in the TI18 tunnel without modifications. We plan for a demonstrator experiment in 2021 with a small detector of about 0.5 tons; with 25/fb, nearly a hundred interactions of neutrinos of about 1 TeV can be recorded. The aim of this pilot run is a good in-situ characterisation of the machine-generated backgrounds, an experimental verification of the systematic uncertainties and efficiencies, and a tuning of the emulsion analysis infrastructure and efficiency. This Letter provides an overview of the experiment motivations, location, design constraints, technology choice, and operation.

The Muon Barrel Alignment system is based on the precise measurement of LED positions and signals of different sensors located in several predetermined places of the barrel. These data are collected by 36 PC/104 board computers. The board computers are organized in a network and controlled by a workstation, which communicates with the DCS system providing the precise status information of the barrel muon chambers. The aim of this paper is to describe the communication flow, the data hierarchy, the data structure, and the distribution of the tasks among the elements of the system. The first simulation and test results are also discussed.

For the precise measurement of the positions of the barrel muon chambers in the CMS detector, a Position Monitoring System has been developed. It comprises ~10000 LED lightsources, 600 active pixel sensor monochrome video cameras, 24 tilt and 72 temperature sensors, 36 PC/104 board computers and a master control workstation for controlling the system and collecting and analyzing the data received from the sensors and cameras.

Neutron and proton irradiation tests were performed to study the radiation induced alterations of COTS (Commercially available Off The Shelf) CMOS active pixel sensors at two facilities. The sensors will be used for the CMS Barrel Muon Alignment system. Results of the tests are presented in this paper.