T. Rohe

Pixel detectors are a particularly important class of particle and radiation detection devices. They have an extremely broad spectrum of applications, ranging from high-energy physics to the photo cam

The Sensor.- The Front-End Electronics.- Integration and System Aspects.- Pixel Detector Applications.- Trends and New Developments for Pixel Detectors.

Prototype sensors for the ATLAS silicon pixel detector have been developed. The design of the sensors is guided by the need to operate them in the severe LHC radiation environment at up to several hundred volts while maintaining a good signal-to-noise ratio, small cell size, and minimal multiple scattering. The ability to be operated under full bias for electrical characterization prior to attachment of the readout integrated circuit electronics is also desired.

The hybrid pixel detectors used in the high-energy physics experiments currently under construction use a vertical connection technique, the so-called bump bonding. As the pitch below 100μm, required in these applications, cannot be fulfilled with standard industrial processes (e.g. the IBM C4 process), an in-house bump bond process using reflowed indium bumps was developed at PSI as part of the R&D for the CMS-pixel detector. The bump deposition on the sensor is performed in two subsequent lift-off steps. As the first photolithographic step a thin under bump metalization (UBM) is sputtered onto bump pads. It is wettable by indium and defines the diameter of the bump. The indium is evaporated via a second photolithographic step with larger openings and is reflowed afterwards. The height of the balls is defined by the volume of the indium. On the readout chip only one photolithographic step is carried out to deposit the UBM and a thin indium layer for better adhesion. After mating both parts a second reflow is performed for self-alignment and obtaining high mechanical strength. For the placement of the chips a manual and an automatic machine were constructed. The former is very flexible in handling different chip and module geometries but has a limited throughput while the latter features a much higher grade of automatization and is therefore much more suited for producing hundreds of modules with a well-defined geometry. The reliability of this process was proven by the successful construction of the PILATUS detector. The construction of PILATUS 6M (60 modules) and the CMS pixel barrel (roughly 800 modules) has started in early 2006.

In recent years, near infrared (NIR) spectroscopy has become an analytical tool frequently used in many chemical production processes. In particular, on-line measurements are of interest to increase process stability and to document constant product quality. Application to polymer processing e.g. polymer extrusion, could even increase product quality. Interesting parameters are composition of the processed polymer, moisture, or reaction status in reactive extrusion. For this issue a transmission sensor was developed for application of NIR spectroscopy to extrusion processes. This sensor includes fibre optic probes and a measuring cell to be adapted to various extruders for in-line measurements. In contrast to infrared sensors, it only uses optical quartz components. Extrusion processes at temperatures up to 300°C and pressures up to 37 MPa have been investigated. Application of multivariate data analysis (e.g. partial least squares, PLS) demonstrated the performance of the system with respect to process monitoring: in the case of polymer blending, deviations between predicted and actual polymer composition were quite low (in the range of ±0.25%). So the complete system is suitable for harsh industrial environments and could lead to improved polymer extrusion processes.

A specially designed heating system for temperature-programmed HPLC was developed based on experimental measurements of eluent temperature inside a stainless steel capillary using a very thin thermocouple. The heating system can be operated at temperatures up to 225 °C and consists of a preheating, a column heating and a cooling unit. Fast cycle times after a temperature gradient can be realized by an internal silicone oil bath which cools down the preheating and column heating unit. Long-term thermal stability of a polybutadiene-coated zirconium dioxide column has been evaluated using a tubular oven in which the column was placed. The packing material was stable after 50 h of operation at 185 °C. A mixture containing four steroids was separated at ambient conditions using a mobile phase of 25% acetonitrile:75% deionized water and a mobile phase of pure deionized water at 185 °C using the specially designed heating system and the PBD column. Analysis time could be drastically reduced from 17 min at ambient conditions and a flow rate of 1 mL/min to only 1.2 min at 185 °C and a flow rate of 5 mL/min. At these extreme conditions, no thermal mismatch was observed and peaks were not distorted, thus underlining the performance of the developed heating system. Temperature programming was performed by separating cytostatic and antibiotic drugs with a temperature gradient using only water as the mobile phase. In contrast to an isocratic elution of this mixture at room temperature, overall analysis time could be reduced two-fold from 20 to 10 min.

Prototype sensors for the ATLAS silicon pixel detector have been electrically characterized. The current and voltage characteristics, charge-collection efficiencies, and resolutions have been examined. Devices were fabricated on oxygenated and standard detector-grade silicon wafers. Results from prototypes which examine p-stop and standard and moderated p-spray isolation are presented for a variety of geometrical options. Some of the comparisons relate unirradiated sensors with those that have received fluences relevant to LHC operation.

The pixel detector is the innermost tracking device of the CMS experiment at the LHC. It is built from two independent subdevices, the pixel barrel and the end disks. The barrel consists of three concentric layers around the beam pipe with mean radii of 4.4, 7.3 and 10.2 cm. There are two end disks on each side of the interaction point at ±34.5 and ±46.5cm. This article gives an overview of the pixel barrel detector, its mechanical support structure, electronics components, services and its expected performance.

The CMS experiment at the (LHC) includes a hybrid silicon pixel detector for the reconstruction of charged tracks and of the interaction vertices. The barrel region consists of n-in-n sensors with 100×150μm2 cell size processed on diffusion oxygenated float zone silicon. A biasing grid is implemented and pixel isolation is achieved with the moderated p-spray technique. An extensive test program was carried out on the H2 beam line of the CERN-SPS. In this paper we describe the sensor layout, the beam test setup and the results obtained with both irradiated and non-irradiated prototype devices. Measurements of charge collection, hit detection efficiency, Lorentz angle and spatial resolution are presented.

Silicon pixel sensors developed by the ATLAS collaboration to meet LHC requirements and to withstand hadronic irradiation to fluences of up to 1015neq/cm2 have been evaluated using a test beam facility at CERN providing a magnetic field. The Lorentz angle was measured and found to alter from 9.0° before irradiation, when the detectors operated at 150V bias at B=1.48T, to 3.1° after irradiation and operating at 600V bias at 1.01T. In addition to the effect due to magnetic field variation, this change is explained by the variation of the electric field inside the detectors arising from the different bias conditions. The depletion depths of irradiated sensors at various bias voltages were also measured. At 600V bias 280μm thick sensors depleted to ≈200μm after irradiation at the design fluence of 1×10151MeVneq/cm2 and were almost fully depleted at a fluence of 0.5×10151MeVneq/cm2. The spatial resolution was measured for angles of incidence between 0° and 30°. The optimal value was found to be better than 5.3μm before irradiation and 7.4μm after irradiation.

While the majority of focus in quantum computing has so far been on monolithic quantum systems, quantum communication networks and the quantum internet in particular are increasingly receiving attention from researchers and industry alike. The quantum internet may allow a plethora of applications such as distributed or blind quantum computing, though research still is at an early stage, both for its physical implementation as well as algorithms; thus suitable applications are an open research question. We evaluate a potential application for the quantum internet, namely quantum federated learning. We run experiments under different settings in various scenarios (e.g. network constraints) using several datasets from different domains and show that (1) quantum federated learning is a valid alternative for regular training and (2) network topology and nature of training are crucial considerations as they may drastically influence the models performance. The results indicate that more comprehensive research is required to optimally deploy quantum federated learning on a potential quantum internet.

Inspired by the remarkable success of artificial neural networks across a broad spectrum of AI tasks, variational quantum circuits (VQCs) have recently seen an upsurge in quantum machine learning applications. The promising outcomes shown by VQCs, such as improved generalization and reduced parameter training requirements, are attributed to the robust algorithmic capabilities of quantum computing. However, the current gradient-based training approaches for VQCs do not adequately accommodate the fact that trainable parameters (or weights) are typically used as angles in rotational gates. To address this, we extend the concept of weight re-mapping for VQCs, as introduced by Kölle et al. [9]. This approach unambiguously maps the weights to an interval of length $$2\pi $$ , mirroring data rescaling techniques in conventional machine learning that have proven to be highly beneficial in numerous scenarios. In our study, we employ seven distinct weight re-mapping functions to assess their impact on eight classification datasets, using variational classifiers as a representative example. Our results indicate that weight re-mapping can enhance the convergence speed of the VQC. We assess the efficacy of various re-mapping functions across all datasets and measure their influence on the VQC's average performance. Our findings indicate that weight re-mapping not only consistently accelerates the convergence of VQCs, regardless of the specific re-mapping function employed, but also significantly increases accuracy in certain cases.

The inner detector of the ATLAS experiment will contain three layers of pixel detectors. The first prototype of the sensor part will be an n+n-device in order to allow partial depleted operation after bulk inversion and a guard-ring scheme keeping the entire detector surface close to the electronic chip on ground potential. Further, a bias structure is introduced providing testability of the sensors before mounting them to the electronics. The design of the single pixel cell is the result of a detailed device simulation study.

The CMS experiment will operate at the Large Hadron Collider (LHC). A hybrid pixel detector located close to the interaction region of the colliding beams will provide high resolution tracking and vertex identification which will be crucial for b quark identification. Because of the radiation environment of the LHC, the performance of the sensors must be carefully evaluated up to a fluence of 6×1014 neq cm−2. We expect that the sensors will be operated partially depleted during their operation at the LHC and we have implemented an n+ on n sensor design. We have irradiated prototype sensors to a dose of 1×1015 neq cm−2. We present the results of our testing before and after irradiation.

Charge collection measurements performed on heavily irradiated p-spray DOFZ pixel sensors with a grazing angle hadron beam provide a sensitive determination of the electric field within the detectors. The data are compared with a complete charge transport simulation of the sensor which includes free carrier trapping and charge induction effects. A linearly varying electric field based upon the standard picture of a constant type-inverted effective doping density is inconsistent with the data. A two-trap double junction model implemented in the ISE TCAD software can be tuned to produce a double peak electric field which describes the data reasonably well. The modeled field differs somewhat from previous determinations based upon the transient current technique. The model can also account for the level of charge trapping observed in the data.

One of the main applications of silicon detectors in future collider experiments is their use in the tracking area. In addition to the very intense hadron flux (both neutral and charged) causing bulk damage, a severe effect by ionizing radiation has also to be envisioned at small radii. In the present study results obtained after irradiation with low energetic electrons (20 keV) are presented. In this case bulk damage can be completely excluded. Effects on the oxide charge and density of interface states are characterized by C—V and I—V measurements. In addition the corresponding changes of the space charge region are observed with a scanning proton micro beam. The electric field distribution, the depletion depth and the lateral extension of the depletion region is thus investigated and the results are compared with detailed simulations using the ToSCA-program.

The tracking system of the CMS experiment, currently under construction at the Large Hadron Collider (LHC) at CERN (Geneva, Switzerland), will include a silicon pixel detector providing three spacial measurements in its final configuration for tracks produced in high-energy pp collisions. In this paper, we present the results of test beam measurements performed at CERN on irradiated silicon pixel sensors. Lorentz angle and charge collection efficiency were measured for two sensor designs and at various bias voltages.

We show that doubly peaked electric fields are necessary to describe grazing-angle charge collection measurements of irradiated silicon pixel sensors. A model of irradiated silicon based upon two defect levels with opposite charge states and the trapping of charge carriers can be tuned to produce a good description of the measured charge collection profiles in the fluence range from 0.5×1014 to 5.9×1014neq/cm2. The model correctly predicts the variation in the profiles as the temperature is changed from -10 to -25∘C. The measured charge collection profiles are inconsistent with the linearly varying electric fields predicted by the usual description based upon a uniform effective doping density. This observation calls into question the practice of using effective doping densities to characterize irradiated silicon.

In this paper we discuss the measurement of charge collection in irradiated silicon pixel sensors and the comparison with a detailed simulation. The simulation implements a model of radiation damage by including two defect levels with opposite charge states and trapping of charge carriers. The modeling proves that a doubly peaked electric field generated by the two defect levels is necessary to describe the data and excludes a description based on acceptor defects uniformly distributed across the sensor bulk. In addition, the dependence of trap concentrations upon fluence is established by comparing the measured and simulated profiles at several fluences and bias voltages.

The CMS experiment which is currently under construction at the Large Hadron Collider (LHC) at CERN (Geneva, Switzerland) will contain a pixel detector which provides in its final configuration three space points per track close to the interaction point of the colliding beams. Because of the harsh radiation environment of the LHC, the technical realization of the pixel detector is extremely challenging. The readout chip as the most damageable part of the system is believed to survive a particle fluence of 6×1014neq/cm2 (All fluences are normalized to 1MeV neutrons and therefore all components of the hybrid pixel detector have to perform well up to at least this fluence. As this requires a partially depleted operation of the silicon sensors after irradiation-induced type inversion of the substrate, an “n in n” concept has been chosen. In order to perform IV-tests on wafer level and to hold accidentally unconnected pixels close to ground potential, a resistive path between the pixels has been implemented by the openings in the p-stop implants surrounding every pixel cell. A prototype of such sensors has been produced by two different companies and especially the properties of these resistors have extensively been tested before and after irradiation.

The Pixel Luminosity Telescope is a silicon pixel detector dedicated to luminosity measurement at the CMS experiment at the LHC. It is located approximately 1.75 m from the interaction point and arranged into 16 "telescopes", with eight telescopes installed around the beam pipe at either end of the detector and each telescope composed of three individual silicon sensor planes. The per-bunch instantaneous luminosity is measured by counting events where all three planes in the telescope register a hit, using a special readout at the full LHC bunch-crossing rate of 40 MHz. The full pixel information is read out at a lower rate and can be used to determine calibrations, corrections, and systematic uncertainties for the online and offline measurements. This paper details the commissioning, operational history, and performance of the detector during Run 2 (2015-18) of the LHC, as well as preparations for Run 3, which will begin in 2022.

Abstract Single-sided p+n and double-sided detectors have been designed for surviving the drastic changes of material properties expected from their use in the harsh radiation environment at the LHC. Detectors optimized for capacitive charge division readout have been exposed to a fluence of 2×1014/cm2 24 GeV protons. Their principal design characteristics and properties after irradiation are described. An explanation for the hitherto not understood survival of single-sided p+n detectors is given. First results with single-sided p+n detectors optimized for binary readout are presented.

The barrel region of the CMS pixel detector will be equipped with “n-in-n” type silicon sensors. They are processed on diffusion oxygenated float zone (DOFZ) material, use the moderated p-spray technique for inter pixel isolation and feature a bias grid. The latter leads to a small fraction of the pixel area to be less sensitive to particles. In order to quantify this inefficiency prototype pixel sensors irradiated to particle fluences between 4.7×1013 and 2.6×1015neq/cm2 have been bump bonded to un-irradiated readout chips and tested using high energy pions at the H2 beam line of the CERN SPS. The readout chip allows a non-zero suppressed analog readout and is therefore well suited to measure the charge collection properties of the sensors. In this paper we discuss the fluence dependence of the collected signal and the particle detection efficiency. Further the position dependence of the efficiency is investigated.

Abstract A replacement of the present CMS pixel detector with a better performing light weight four-layer system is foreseen in 2016. In the lifetime of this new system the LHC will reach and exceed its nominal luminosity of 10 34  cm −2  s −1 . Therefore the radiation hardness of all parts of the pixel system has to be reviewed. For the construction of the much larger four-layer pixel system, the replacement of the present double sided sensors by much cheaper single sided ones is considered. However, the construction of pixel modules with such sensors is challenging due to the small geometrical distance of the sensor high voltage and the ground of the readout electronics. This small distance limits the sensor bias to about 500 V in the tested samples.

The ATLAS experiment (The ATLAS Collaboration, ATLAS TDR 11, CERN/LHCC 98–13) which is currently under construction at the Large Hardorn Collider (LHC) at CERN (Geneva, Switzerland) will contain a pixel detector which provides three space points per track close to the interaction point of the colliding beams. Because of the harsh radiation environment of the LHC the technical realisation of the pixel detector is extremely challenging. All components of the hybrid pixel detector have to be radiation hard up to a particle fluence2 of 1015 neq/cm2. This paper reports on the development of the sensor part of the system. A first prototype has been produced and successfully tested.

Strip detectors covering radiation hardness and large-scale production ability are developed and produced for the ATLAS experiment at the Large Hadron Collider (LHC) at CERN (Switzerland). Capacitively coupled p+n detectors (p-type strips on n-type substrate) were developed with implanted bias resistors in order to simplify the detector processing addressing the requirements of large-scale production. The detectors were irradiated with 24 GeV protons up to 3×1014cm−2 in order to simulate a 10 years operation scenario at LHC. The presented static and signal measurements demonstrate the function of the device concept before and after irradiation.

This paper reports on the sensor R&D activity for the CMS pixel detector. Devices featuring several design and technology options have been irradiated up to a proton fluence of 1/spl times/10/sup 15/ n/sub eq//cm/sup 2/ at the CERN PS. Afterward, they were bump bonded to unirradiated readout chips and tested using high energy pions in the H2 beam line of the CERN SPS. The readout chip allows a nonzero suppressed full analogue readout and therefore a good characterization of the sensors in terms of noise and charge collection properties. The position dependence of signal is presented and the differences between the two sensor options are discussed.

The CMS pixel barrel system will consist of three layers built of about 800 modules. One module contains 66 560 readout channels and the full pixel barrel system about 48 million channels. It is mandatory to test each channel for functionality, noise level, trimming mechanism, and bump bonding quality. Different methods to determine the bump bonding yield with electrical measurements have been developed. Measurements of several operational parameters are also included in the qualification procedure. Among them are pixel noise, gains and pedestals. Test and qualification procedures of the pixel barrel modules are described and some results are presented.

Abstract The pixel detector of the CMS experiment will need to be replaced after a couple of years of LHC running because of radiation damage. On the other hand, plans for a step wise luminosity upgrade of the accelerator beyond the present design value around 2014 are being prepared. While the replacement pixel detector must be designed to handle increased particle rates, it should maintain or improve the tracking performance of the present system and must be compatible with existing services.

Prototype n+ on n sensors with different guard rings and p-stop isolation designs were developed for the CMS Forward Pixel System. The prototype sensors were irradiated to a fluence equivalent to that expected after 6 years of operation at the LHC. I–V characteristics of these sensors after irradiation were measured.

For the barrel part of the CMS pixel tracker about 800 silicon pixel detector modules are required. The modules are bump bonded, assembled and tested at the Paul Scherrer Institute. This article describes the experience acquired during the assembly of the first ∼200 modules.

Pixel detectors are used in the innermost part of the multi purpose experiments at LHC and are therefore exposed to the highest fluences of ionising radiation, which in this part of the detectors consists mainly of charged pions. The radiation hardness of all detector components has thoroughly been tested up to the fluences expected at the LHC. In case of an LHC upgrade, the fluence will be much higher and it is not yet clear how long the present pixel modules will stay operative in such a harsh environment. The aim of this study was to establish such a limit as a benchmark for other possible detector concepts considered for the upgrade. As the sensors and the readout chip are the parts most sensitive to radiation damage, samples consisting of a small pixel sensor bump-bonded to a CMS-readout chip (PSI46V2.1) have been irradiated with positive 200 MeV pions at PSI up to 6E14 Neq and with 21 GeV protons at CERN up to 5E15 Neq. After irradiation the response of the system to beta particles from a Sr-90 source was measured to characterise the charge collection efficiency of the sensor. Radiation induced changes in the readout chip were also measured. The results show that the present pixel modules can be expected to be still operational after a fluence of 2.8E15 Neq. Samples irradiated up to 5E15 Neq still see the beta particles. However, further tests are needed to confirm whether a stable operation with high particle detection efficiency is possible after such a high fluence.

Abstract In the context of the development of the ATLAS-Pixel-Detector [1], a technology for building up the high density interconnects has been studied, the MCM-D (multi chip module deposited) technology. Results of building up first assemblies have been reported in [2]. MCM-D technology allows to build up assemblies with uniformly segmented sensors. Especially the use of 'equal-sized(-bricked)' sensor geometry has been studied.

Pixel detectors are used in the innermost part of multi purpose experiments at the Large Hadron Collider (LHC) and are therefore exposed to the highest fluences of ionising radiation, which in this part of the detectors consists mainly of charged pions. The radiation hardness of the detectors has thoroughly been tested up to the fluences expected at the LHC. In case of an LHC upgrade the fluence will be much higher and it is not yet clear up to which radii the present pixel technology can be used. In order to establish such a limit, pixel sensors of the size of one CMS pixel readout chip (PSI46V2.1) have been bump bonded and irradiated with positive pions up to 6E14 Neq/cm^2 at PSI and with protons up to 5E15 Neq/cm^2. The sensors were taken from production wafers of the CMS barrel pixel detector. They use n-type DOFZ material with a resistance of about 3.7kOhm cm and an n-side read out. As the performance of silicon sensors is limited by trapping, the response to a Sr-90 source was investigated. The highly energetic beta-particles represent a good approximation to minimum ionising particles. The bias dependence of the signal for a wide range of fluences will be presented.

A new method for the extraction of the electric field in the bulk of heavily irradiated silicon pixel sensors is presented. It is based on the measurement of the Lorentz deflection and mobility of electrons as a function of depth. The measurements were made at the CERN H2 beam line, with the beam at a shallow angle with respect to the pixel sensor surface. The extracted electric field is used to simulate the charge collection and the Lorentz deflection in the pixel sensor. The simulated charge collection and the Lorentz deflection is in good agreement with the measurements both for non-irradiated and irradiated up to 1E15 neq/cm2 sensors.

A study of 3D pixel sensors of cell size 50 {\mu}m x 50 {\mu}m fabricated at IMB-CNM using double-sided n-on-p 3D technology is presented. Sensors were bump-bonded to the ROC4SENS readout chip. For the first time in such a small-pitch hybrid assembly, the sensor response to ionizing radiation in a test beam of 5.6 GeV electrons was studied. Results for non-irradiated sensors are presented, including efficiency, charge sharing, signal-to-noise, and resolution for different incidence angles.

For the Phase I upgrade of the CMS pixel detector a new digital readout chip (ROC) has been developed. An important part of the design verification are irradiation studies to ensure sufficient radiation tolerance. The paper summarizes results of the irradiation studies on the final ROC design for the detector layers 2 – 4. Samples have been irradiated with 23 MeV protons to accumulate the expected lifetime dose of 0.5 MGy and up to 1.1 MGy to project the performance of the ROC for layer 1 of the detector. It could be shown that the design is sufficiently radiation tolerant and that all performance parameters stay within their specifications. Additionally, very high doses of up to 4.2 MGy have been tested to explore the limits of the current chip design on 250 nm CMOS technology. The study confirmed that samples irradiated up to the highest dose could be successfully operated with test pulses.

ATLAS prototype n–in–n and p–in–n silicon strip detectors from several manufacturers were irradiated with 24 GeV protons at the CERN PS to a total fluence of 3×1014p/cm2. This is equivalent to the maximum fluence expected in the strip detector part of the silicon tracker after 10 yr of operation. The ATLAS semiconductor tracker will be operated at −7°C. Yearly warm-up periods of 2 days at 20°C and 2 weeks at 17°C are foreseen for maintenance purposes (ATLAS Inner Detector Technical Design Rep., 1997). To study the long-term effects of radiation damage and warm-up the detectors underwent controlled thermal annealing. The Ziock parameterisation was used to simulate the warm-up effects of 10 yr on a shortened time scale (H.J. Ziock et al., Nucl. Instr. and Meth. A 342 (1994) 96). Using this parameterisation the same amount of anti-annealing gained during 10 yr of warm-ups can be reached by storing the detectors for 21 days at 25°C. During the annealing period current–voltage and capacitance–voltage measurements were carried out at regular intervals. The full depletion voltage was then determined from the capacitance measurements and showed a clear dependency on the measurement frequency and temperature. The evolution of the full depletion voltage as a function of annealing time is compared to the Ziock parameterisation.

Abstract In future high-luminosity collider experiments, fine segmented silicon strip and pixel detectors will be used for tracking very close to the interaction point. Therefore the surface effects due to irradiation are very important for the long term performance of these devices. A good understanding of these effects is the basis for the development of less radiation sensitive detectors. An important tool for this understanding is device simulation. In the comparison of device simulations with measurements of ionisation-induced surface effects it became obvious that the electric field distribution in the passivation during the irradiation cuases a position dependent increase of interface charges. In order to achieve more realistic simulations this was taken into account by varying the oxide charge density according to results obtained from MOS-structures.

The proposed high-luminosity upgrade of the Large Hadron Collider is expected to increase the instantaneous luminosity at the experiments' interaction points by a factor of ten. The vertex detector will be the subsystem most affected by the luminosity increase, raising substantially their occupancy and radiation-induced damage. To preserve the vertex physics performance under these new conditions, current pixel technologies have to be improved. Hybrid pixel sensors with double-sided double-type vertical electrodes (3D sensors) are becoming a mature technology for the detector layers closest to the interaction point due to their intrinsic radiation hardness. In addition, the double-sided implementation of the 3D pixel technology provides some additional technical advantages with respect to the single-sided implementation. For this study, 3D pixel sensors manufactured at the Centro Nacional de Microelectrónica of Barcelona (IMB-CNM) have been bonded to the PSI46 readout chip currently used by the Compact Muon Solenoid vertex detector. Detector performance before and after irradiation up to fluences of 5×1015neq/cm2 is presented.

MoTiC (Monolithic Timing Chip) is a prototype DMAPS Chip that builds on sensor technology developed in the ARCADIA project.The 50 by 50 µm 2 pixels contain a small charge collecting electrode with a very low capacitance surrounded by radiation-hard in-pixel electronics.The chip contains a matrix of 5120 pixels on an area of 3.2 by 4 mm 2 .Each pixel features a trimmable and maskable comparator with a sample and hold circuit for the analog pulse height.Groups of 4 pixels share a TDC situated also in the readout matrix.This work presents the chip design and preliminary results of the hit efficiencies and spatial resolution measured in a first test beam campaign with 4-5 GeV/c electrons conducted at DESY.

Variational Quantum Algorithms are one of the most promising candidates to yield the first industrially relevant quantum advantage. Being capable of arbitrary function approximation, they are often referred to as Quantum Neural Networks (QNNs) when being used in analog settings as classical Artificial Neural Networks (ANNs). Similar to the early stages of classical machine learning, known schemes for efficient architectures of these networks are scarce. Exploring beyond existing design patterns, we propose a reduced-width circuit ansatz design, which is motivated by recent results gained in the analysis of dropout regularization in QNNs. More precisely, this exploits the insight, that the gates of overparameterized QNNs can be pruned substantially until their expressibility decreases. The results of our case study show, that the proposed design pattern can significantly reduce training time while maintaining the same result quality as the standard "full-width" design in the presence of noise.

Inspired by the remarkable success of artificial neural networks across a broad spectrum of AI tasks, variational quantum circuits (VQCs) have recently seen an upsurge in quantum machine learning applications. The promising outcomes shown by VQCs, such as improved generalization and reduced parameter training requirements, are attributed to the robust algorithmic capabilities of quantum computing. However, the current gradient-based training approaches for VQCs do not adequately accommodate the fact that trainable parameters (or weights) are typically used as angles in rotational gates. To address this, we extend the concept of weight re-mapping for VQCs, as introduced by Kölle et al. (2023). This approach unambiguously maps the weights to an interval of length $2π$, mirroring data rescaling techniques in conventional machine learning that have proven to be highly beneficial in numerous scenarios. In our study, we employ seven distinct weight re-mapping functions to assess their impact on eight classification datasets, using variational classifiers as a representative example. Our results indicate that weight re-mapping can enhance the convergence speed of the VQC. We assess the efficacy of various re-mapping functions across all datasets and measure their influence on the VQC's average performance. Our findings indicate that weight re-mapping not only consistently accelerates the convergence of VQCs, regardless of the specific re-mapping function employed, but also significantly increases accuracy in certain cases.

Abstract Major challenges in building silicon strip detectors for future high luminosity experiments are the high radiation level and the huge number of sensors required for the construction of the precision layers of the complete tracking system. Single-sided p + n strip detectors for ATLAS SCT designed and fabricated at the MPI Semiconductor Laboratory have been exposed to 3×10 14 /cm 2 24 GeV protons. The major features of the design, including the biasing technique using implanted resistors, are discussed and results are presented. The technology was transferred to CiS, Germany, a company capable of the desired large-scale production. Results of this industrially fabricated sensors look very promising and show the expected radiation hardness.

Charge collection measurements performed on heavily irradiated p-spray dofz pixel sensors with a grazing angle hadron beam provide a sensitive determination of the electric field within the detectors. The data are compared with a complete charge transport simulation of the sensor which includes signal trapping and charge induction effects. A linearly varying electric field based upon the standard picture of a constant type-inverted effective doping density is inconsistent with the data. A two-trap double junction model implemented in ISE TCAD software can be tuned to produce a doubly-peaked electric field which describes the data reasonably well at two different fluences. The modeled field differs somewhat from previous determinations based upon the transient current technique. The model can also account for the level of signal trapping observed in the data.

The CMS experiment will include a pixel detector for pattern recognition and vertexing. It will consist of three barrel layers and two endcaps on each side, providing three space-points up to a pseudoraditity of 2.1. Taking into account the expected limitations of its performance in the LHC environment an 8-9 layer pixel detector for an upgraded LHC is discussed.

The inner detectors of LHC experiments will contain pixel detectors covering an area of several square meters. In addition they are facing the harsh radiation environment of the LHC. A first prototype sensor has been designed according to the requirements of the ATLAS experiment, produced and successfully tested with static measurements. Irradiation tests have also been performed with excellent results. The sensor is an n+ n-device in order to allow partial depleted operation after bulk inversion and a guard ring scheme keeping the entire detector surface close to the electronic chip on ground potential. Further, a bias structure is introduced providing testability of the sensors prior to bump bonding and flip chipping.

The CMS barrel pixel detector is the innermost tracking device, reconstructing the interaction vertices and charged particle trajectories. At the LHC design luminosity, 1034 cm−2 s−1, there will be 1000 charged particles per bunch crossing every 25 ns. In the innermost layer the pixel sensors will be exposed to a fluence of 3×1014neq/cm2/yr with consequent degradation of the silicon lattice structure and particle detection performances. Beam tests of irradiated pixel sensors were performed at CERN with the final front end electronics in a 3T magnetic field. We present the measurements of charge collection and radiation hardness, as well as spatial resolution.

Modules for the CMS pixel barrel detector have been operated in a high rate pion beam at PSI in order to verify under LHC-like conditions the final module design for the production. The test beam provided charged particle rates up to 108cm-2s-1 over the full module area. Bunch structure and randomized high trigger rates simulated realistic operation. A four layer telescope made of single pixel readout chip assemblies provided tracking needed for the determination of the modules hit reconstruction efficiency. The performance of the modules has been shown to be adequate for the CMS pixel barrel.

The Multi-Chip-Module-Deposited (MCM-D) technique has been used to build hybrid pixel detector assemblies. This paper summarises the results of an analysis of data obtained in a test beam campaign at CERN. Single-chip hybrids made of ATLAS pixel prototype read-out electronics and special sensor tiles were used. The sensors feature an optimized sensor geometry called “equal sized bricked”. In this document, the geometry of this type of hybrid is described and their performance in terms of spatial resolution and charge collection is shown.

This paper reports on a current R&D activity for the sensor part of the CMS pixel detector. Devices featuring several design and technology options have been irradiated up to a proton fluence of 1 /spl times/ 10/sup 15/ n/sup eq//cm/sup 2/ at the CERN PS. Afterwards they have been bump bonded to unirradiated readout chips. The chips allow a non zero suppressed full analogue readout and therefore a good characterization of the sensors in terms of noise and charge collection properties. The samples have been tested using high energy pions in the H2 beam line of the CERN SPS in June and September 2003. The results of this test beam are presented and the differences between the sensor options are discussed.

We show that doubly peaked electric fields are necessary to describe grazing-angle charge collection measurements of irradiated silicon pixel sensors. A model of irradiated silicon based upon two defect levels with opposite charge states and the trapping of charge carriers can be tuned to produce a good description of the measured charge collection profiles in the fluence range from 0.5×10 14 neq/cm 2 to 5.9×10 14 neq/cm 2 . The model correctly predicts the variation in the profiles as the temperature is changed from 10 ◦ C to 25 ◦ C. The measured charge collection profiles are inconsistent with the linearly-varying electric fields predicted by the usual description based upon a uniform effective doping density. This observation calls into question the practice of using effective doping densities to characterize irradiated silicon. The model is now being used to calibrate pixel hit reconstruction algorithms for CMS.

Charge collection measurements performed on heavily irradiated p-spray dofz pixel sensors with a grazing angle hadron beam provide a sensitive determination of the electric field within the detectors. The data are compared with a complete charge transport simulation of the sensor which includes signal trapping and charge induction effects. A linearly varying electric field based upon the standard picture of a constant type-inverted effective doping density is inconsistent with the data. A two-trap double junction model implemented in ISE TCAD software can be tuned to produce a doubly-peaked electric field which describes the data reasonably well at two different fluences. The modeled field differs somewhat from previous determinations based upon the transient current technique. The model can also account for the level of signal trapping observed in the data.

We show that doubly peaked electric fields are necessary to describe grazing-angle charge collection measurements of irradiated silicon pixel sensors. A model of irradiated silicon based upon two defect levels with opposite charge states and the trapping of charge carriers can be tuned to produce a good description of the measured charge collection profiles in the fluence range from 0.5x10^{14} Neq/cm^2 to 5.9x10^{14} Neq/cm^2. The model correctly predicts the variation in the profiles as the temperature is changed from -10C to -25C. The measured charge collection profiles are inconsistent with the linearly-varying electric fields predicted by the usual description based upon a uniform effective doping density. This observation calls into question the practice of using effective doping densities to characterize irradiated silicon. The model is now being used to calibrate pixel hit reconstruction algorithms for CMS.

A new method for the extraction of the electric field in the bulk of heavily irradiated silicon pixel sensors is presented. It is based on the measurement of the Lorentz deflection and mobility of electrons as a function of depth. The measurements were made at the CERN H2 beam line, with the beam at a shallow angle with respect to the pixel sensor surface. The extracted electric field is used to simulate the charge collection and the Lorentz deflection in the pixel sensor. The simulated charge collection and the Lorentz deflection is in good agreement with the measurements both for non-irradiated and irradiated up to 1E15 neq/cm2 sensors.