High Energy Physics Detectors Research Articles

Redundant-Configuration Scrubbing of SRAM-Based FPGAs

Static RAM-based field programmable gate arrays (SRAM-based FPGAs) are widely adopted in trigger and data acquisition systems of high-energy physics detectors for implementing fast logic due to their reconfigurability, large real-time processing capabilities and embedded high-speed serial IOs. These devices are sensitive to radiation-induced upsets, which may alter the functionality of the implemented circuit. Presently, their usage on-detector is limited and there is a strong interest in finding solutions for improving their tolerance to radiation-induced upsets. In this paper, we show a novel configuration-redundancy generation and scrubbing technique for SRAM-based FPGAs. It leads to a power saving with respect to other solutions in the literature. Moreover, our technique is compatible with several Xilinx FPGA families. Our solution does not require neither the usage of external memories nor third-party layout tools. We describe an example of our solution applied to a benchmark design implemented in a Xilinx Kintex-7 FPGA. In order to prove the effectiveness of the solution, we present results from a proton irradiation test.

Horizon 2020 EuPRAXIA design study

The Horizon 2020 Project EuPRAXIA (“European Plasma Research Accelerator with eXcellence In Applications”) is preparing a conceptual design report of a highly compact and cost-effective European facility with multi-GeV electron beams using plasma as the acceleration medium. The accelerator facility will be based on a laser and/or a beam driven plasma acceleration approach and will be used for photon science, high-energy physics (HEP) detector tests, and other applications such as compact X-ray sources for medical imaging or material processing. EuPRAXIA started in November 2015 and will deliver the design report in October 2019. EuPRAXIA aims to be included on the ESFRI roadmap in 2020.

Intelligent FPGA Data Acquisition Framework

In this paper, we present the field programmable gate arrays (FPGA)-based framework intelligent FPGA data acquisition (IFDAQ), which is used for the development of DAQ systems for detectors in high-energy physics. The framework supports Xilinx FPGA and provides a collection of IP cores written in very high speed integrated circuit hardware description language, which use the common interconnect interface. The IP core library offers functionality required for the development of the full DAQ chain. The library consists of Serializer/Deserializer (SERDES)-based time-to-digital conversion channels, an interface to a multichannel 80-MS/s 10-b analog-digital conversion, data transmission, and synchronization protocol between FPGAs, event builder, and slow control. The functionality is distributed among FPGA modules built in the AMC form factor: front end and data concentrator. This modular design also helps to scale and adapt the DAQ system to the needs of the particular experiment. The first application of the IFDAQ framework is the upgrade of the read-out electronics for the drift chambers and the electromagnetic calorimeters (ECALs) of the COMPASS experiment at CERN. The framework will be presented and discussed in the context of this paper.

An integrated model of scintillator-reflector properties for advanced simulations of optical transport

Accurately modeling the light transport in scintillation detectors is essential to design new detectors for nuclear medicine or high energy physics. Optical models implemented in software such as Geant4 and GATE suffer from important limitations that we addressed by implementing a new approach in which the crystal reflectance was computed from 3D surface measurements. The reflectance was saved in a look-up-table (LUT) then used in Monte Carlo simulation to determine the fate of optical photons. Our previous work using this approach demonstrated excellent agreement with experimental characterization of crystal light output in a limited configuration, i.e. when using no reflector.As scintillators are generally encapsulated in a reflector, it is essential to include the crystal-reflector interface in the LUT. Here we develop a new LUT computation and apply it to several reflector types. A second LUT that contains transmittance data is also saved to enable modeling of optical crosstalk.LUTs have been computed for rough and polished crystals coupled to a Lambertian (e.g. Teflon tape) or a specular reflector (e.g. ESR) using air or optical grease, and the light output was computed using a custom Monte Carlo code. 3 × 3 × 20 mm3 lutetium oxyorthosilicate crystals were prepared using these combinations, and the light output was measured experimentally at different irradiation depths. For all reflector and surface finish combinations, the measured and simulated light output showed very good agreement.The behavior of optical photons at the interface crystal-reflector was studied using these simulations, and results highlighted the large difference in optical properties between rough and polished crystals, and Lambertian and specular reflectors. These simulations also showed how the travel path of individual scintillation photons was affected by the reflector and surface finish.The ultimate goal of this work is to implement this model in Geant4 and GATE, and provide a database of scintillators combined with a variety of reflectors.

The role of pixel detectors in high energy physics

A number of new types of pixel detector systems have been pioneered in the last decade. These include new types of sensors as well as new electronics to allow much higher performance. At the same time new experiments are being planned or nearing completion covering a broad range of physics topics in flavour physics as well as large major upgrades at the LHC. These are planning to make use of the advances in pixel detectors in important ways. In this review both the pixel advances and how they enable the physics will be presented.

Characterization of GaAs:Cr-based Timepix detector using synchrotron radiation and charged particles

The interest in the use of high resistivity gallium arsenide compensated by chromium (GaAs:Cr) for photon detection has been growing steadily due to its numerous advantages over silicon. At the same time, the prospects of this material as a sensor for pixel detectors in nuclear and high energy physics are much less studied. In this paper we report the results of characterization of the Timepix detectors hybridized with GaAs:Cr sensors of various thickness using synchrotron radiation and various charged particles, including alphas and heavy ions. The energy and spatial resolution have been determined. Interesting features of GaAs:Cr specific to the detector response to an extremely dense energy deposit by heavy ions have been observed for the first time. The long-term stability of the detector has been evaluated based on the measurements performed over one year. Possible limitation of GaAs:Cr as a sensor for high flux X-ray imaging is discussed.

PMT overshoot study for the JUNO prototype detector**Supported by Strategic Priority Research Program A-JUNO, High Energy Physics Experiment and Detector R&D and National Natural Science Foundation of China

The quality of PMT signals is crucial for large-size and high-precision neutrino experiments, but most of these experiments are affected by the overshoot of PMT signals from the positive HV-single cable scheme. Overshoot affects the trigger, dead time and charge measurement from a detector. For the JUNO prototype detector, we have performed a detailed study and calculation on PMT signal overshoot to control the ratio of overshoot to signal amplitude to ∼1%, with no effect on other PMT parameters.

Detection of high energy muons with sub-20 ps timing resolution using L(Y)SO crystals and SiPM readout

Precise timing capability will be a key aspect of particle detectors at future high energy colliders, as the time information can help in the reconstruction of physics events at the high collision rate expected there. Other than being used in detectors for PET, fast scintillating crystals coupled to compact Silicon Photomultipliers (SiPMs) constitute a versatile system that can be exploited to realize an ad-hoc timing device to be hosted in a larger high energy physics detector. In this paper, we present the timing performance of LYSO:Ce and LSO:Ce codoped 0.4% Ca crystals coupled to SiPMs, as measured with 150GeV muons at the CERN SPS H2 extraction line. Small crystals, with lengths ranging from 5mm up to 30mm and transverse size of 2×2mm2 or 3×3mm2, were exposed to a 150GeV muon beam. SiPMs from two different companies (Hamamatsu and FBK) were used to detect the light produced in the crystals. The best coincidence time resolution value of (14.5±0.5)ps, corresponding to a single-detector time resolution of about 10ps, is demonstrated for 5mm long LSO:Ce,Ca crystals coupled to FBK SiPMs, when time walk corrections are applied.

Comparison of test beam data from imaging calorimeters with Geant4 simulations

The highly granular calorimeter prototypes of the CALICE collaboration have provided large data samples with precise three-dimensional information on hadronic showers with steel and tungsten absorbers and silicon, scintillator and gas detector readout. From these data sets, detailed measurements of the spatial structure, including longitudinal and radial shower profiles and of the shower substructure are extracted. Dedicated experiments with scintillator and RPC active elements extend these measurements to include information on the time structure of hadronic showers. These results are confronted with Geant4 simulations with different hadronic physics models, presenting new challenges to the simulation codes and providing the possibility to validate and improve the simulation of hadronic interactions in high-energy physics detectors.

Light yield measurements of “finger” structured and unstructured scintillators after gamma and neutron irradiation

Plastic scintillators are often used as detectors in High Energy Physics (HEP), but have insufficient radiation hardness. Organization of better light collection inside a single detector may prolong operation life of scintillators. A finger-strip plastic scintillator option has many advantages to keep the excellent detector performance at high luminosity. Measurements assigned to show an advantage of a stripped detector vs. the un-stripped one in the range of increased absorbed doses and the smallest dose rates have been performed. This method has proved to be a good upgrade strategy.

Effect of Mg2+ ions co-doping on timing performance and radiation tolerance of Cerium doped Gd3Al2Ga3O12 crystals

Inorganic scintillators with high density and high light yield are of major interest for applications in medical imaging and high energy physics detectors. In this work, the optical and scintillation properties of Mg co-doped Ce:Gd3Al2Ga3O12 crystals, grown using Czochralski technique, have been investigated and compared with Ce:Gd3Al2Ga3O12 ones prepared with identical technology. Improvements in the timing performance of the Mg co-doped samples with respect to Ce:Gd3Al2Ga3O12 ones have been measured, namely a substantial shortening of the rise time and scintillation decay components and lower afterglow were achieved. In particular, a significantly better coincidence time resolution of 233ps FWHM, being a fundamental parameter for TOF-PET devices, has been observed in Mg co-doped crystals. The samples have also shown a good radiation tolerance under high doses of γ-rays, making them suitable candidates for applications in harsh radiation environments, such as detectors at future collider experiments.

Optical Wireless Communication system for particle detectors in high energy physics

Optical Wireless Communication (OWC) system for particles detector can be a viable solution for reducing the complexity of the optical fibre network used to extract the data from the detector. In this work we present the initial study of the tolerance to misalignment for the OWC system under investigation. We observed that using collimators of beam waist from 0.35mm to 3.5mm we can obtain tolerance in range from ±0.25mm to ±0.8mm. We also observed using ray trace simulation that both transmitting power and tolerance can be improved by using optimized lens at the receiver having VCSEL as transmitting source.

Laser Micromachining and Characterization of Metal-on-Glass High Density Pitch Adapters

Pitch adapters (PAs) are passive electronic components widely used to adapt different pitches between silicon strip detectors and readout electronics. This paper presents an optimized process to fabricate high-density PAs using laser ablation of metal-on-glass layers. Minimum pitch sizes of 40 $\mu \text{m}$ for the pads and 25 $\mu \text{m}$ for the conductive traces were achieved. The resolution of the method allowed the cutting of traces as narrow as 15 $\mu \text{m}$ . Different prototypes and small production series have been successfully manufactured and tested for electrical parameters, bondability, and metrology. Ageing tests were also performed to ensure long-term reliability. The production yield reached 80%. Fully functional particle detectors for high-energy physics have been assembled using these PAs, characterized and tested with lasers and radioactive sources. [2014-0371]

A spreading resistance based method of mapping the resistivity and potential of a depleted diode

The characterization of the depletion states of reverse operated p-n junctions is an important task within the scope of high energy physics detector development. The configuration of the sensitive volume inside these structures determines the particle detection process. Therefore a spreading resistance profiling based method has been developed to map the local resistivity and potential along the prepared edge of a depleted diode. This ``edge-SRP" method is capable of detecting the boarder of the space charge region and its transition to the electrical neutral bulk. In order to characterize the depleted space charge region, the surface potential along the edge could be measured by slightly modifying the setup. These surface potential results complement the spreading resistance one. In this paper the functionality of the developed method is verified by performing measurements on a prepared diode, which has been biased with different voltages.

Track reconstruction by GPU in 3D particle tracking detectors

3D detectors for high-energy physics have always needed large computing power. Its availability has sometimes determined the statistics and performance of experiments. The increasing specific computing power of GPUs in recent years offers new opportunities for this field of application that should not be missed. The paper shows a novel algorithm that supports, as a by-product of speed, wider angular acceptance with respect to established techniques based on CPUs. While the algorithm has been developed in the environment of nuclear emulsions, it has been conceived from the very beginning as a tool for general tracking in 3D detectors. The overall logic can apply to many operational contexts in which tracking occurs in high combinatorial background. The performances of the algorithm are evaluated from different points of view, describing the details of the computing technique that are common to tracking problems and discussing measurements and data from a test-beam exposure. Computing speed has been evaluated on a broad variety of hardware, investigating an approximated scaling formula.

Silicon micro-fluidic cooling for NA62 GTK pixel detectors

Silicon micro-channel cooling is being studied for efficient thermal management in application fields such as high power computing and 3D electronic integration. This concept has been introduced in 2010 for the thermal management of silicon pixel detectors in high energy physics experiments.Combining the versatility of standard micro-fabrication processes with the high thermal efficiency typical of micro-fluidics, it is possible to produce effective thermal management devices that are well adapted to different detector configurations. The production of very thin cooling devices in silicon enables a minimization of material of the tracking sensors and eliminates mechanical stresses due to the mismatch of the coefficient of thermal expansion between detectors and cooling systems.The NA62 experiment at CERN will be the first high particle physics experiment that will install a micro-cooling system to perform the thermal management of the three detection planes of its Gigatracker pixel detector.

Similarities and differences of recent hybrid pixel detectors for X-ray and high energy physics developed at the Paul Scherrer Institut

Hybrid pixel detectors are being developed for both photon science and high energy physics. The article will cover similarities and differences in pixel detectors for both applications using two of the pixel detectors developed at the Paul Scherrer Institute (Switzerland) as examples: the EIGER photon counting detector and the psi46dig chip, which has been developed for the Compact Muon Solenoid (CMS) tracking pixel detector upgrade.EIGER is a single photon counting hybrid pixel detector for applications at synchrotron light sources in the energy range from a few to 25 keV. It is characterized by a small pixel size (75 × 75 μm2), high count rate capability (106 counts/pixel/s) and very high data rate, which reaches 6 Gb/s for a 256 × 256 pixel chip. The CMS pixel detector is designed to provide charge information from the pixels in the harsh radiation environment at the Large Hadron Collider. The short time between bunches of 25 ns and the high event rate at luminosity up to 2 × 1034cm−2s−1 require a detector with high hit efficiency, with good timing resolution and the ability to retain timestamp information for the hits. The readout architecture is based on the transfer of hits from the pixels to the periphery, where the trigger validation is performed before data transfer. The data rates of the digitized output reach 160 Mb/s for a 52×80 pixel chip.The specific timing and rate requirements for the detectors, the analog performances (minimum threshold and noise), the power consumption and the radiation hardness will be compared. An overview on future developments based on mutual learning and common solutions will be discussed.

MICROMEGAS Signal: Numerical Simulation Based on Neon-Isobutane and Neon-DME

Recent years, we have seen the development of many fields of gas detectors. The MICROMEGAS (Micro-Mesh Gas Structure) appeared as the very promising detector. It is a major family of position detectors in High Energy Physics. This work is done in normal (NTP) based gas mixtures: neon are noble gas and isobutane and DME (dimethyl-ether) as moderators gas (quenchers), using 55Fe as a radiation source (X-ray 5.9 keV). To address the modeling of MICROMEGAS detector, a descriptive model of different physical and geometrical phenomena MICROMEGAS was established by developing a simulation program to spreading the detector response. After, an analytical calculation of the potential and the electric field distributions has been presented briefly, to better estimate electrical and geometric configuration. Finally, simulation results of electrical signals based on gas mixtures (Neon-isobutane, Neon-DME) produced by MICROMEGAS were presented and analyzed in order to improve the MICROMEGAS performance (spatial (12 μm) and temporal (0.7 ns) resolutions).

A high speed, low power consumption LVDS interface for CMOS pixel sensors

The use of CMOS Pixel Sensors (CPSs) offers a promising approach to the design of vertex detectors in High Energy Physics (HEP) experiments. As the CPS equipping the upgraded Solenoidal Tracker at RHIC (STAR) pixel detector, ULTIMATE perfectly illustrates the potential of CPSs for HEP applications. However, further development of CPSs with respect to readout speed is required to fulfill the readout time requirement of the next generation HEP detectors, such as the upgrade of A Large Ion Collider Experiment (ALICE) Inner Tracking System (ITS), the International Linear Collider (ILC), and the Compressed Baryonic Matter (CBM) vertex detectors. One actual limitation of CPSs is related to the speed of the Low-Voltage Differential Signaling (LVDS) circuitry implementing the interface between the sensor and the Data Acquisition (DAQ) system. To improve the transmission rate while keeping the power consumption at a low level, a source termination technique and a special current comparator were adopted for the LVDS driver and receiver, respectively. Moreover, hardening techniques are used. The circuitry was designed and submitted for fabrication in a 0.18-µm CMOS Image Sensor (CIS) process at the end of 2011. The test results indicated that the LVDS driver and receiver can operate properly at the data rate of 1.2Gb/s with power consumption of 19.6mW.

High energy electromagnetic particle transportation on the GPU

We present massively parallel high energy electromagnetic particle transportation through a finely segmented detector on a Graphics Processing Unit (GPU). Simulating events of energetic particle decay in a general-purpose high energy physics (HEP) detector requires intensive computing resources, due to the complexity of the geometry as well as physics processes applied to particles copiously produced by primary collisions and secondary interactions. The recent advent of hardware architectures of many-core or accelerated processors provides the variety of concurrent programming models applicable not only for the high performance parallel computing, but also for the conventional computing intensive application such as the HEP detector simulation. The components of our prototype are a transportation process under a non-uniform magnetic field, geometry navigation with a set of solid shapes and materials, electromagnetic physics processes for electrons and photons, and an interface to a framework that dispatches bundles of tracks in a highly vectorized manner optimizing for spatial locality and throughput. Core algorithms and methods are excerpted from the Geant4 toolkit, and are modified and optimized for the GPU application. Program kernels written in C/C++ are designed to be compatible with CUDA and OpenCL and with the aim to be generic enough for easy porting to future programming models and hardware architectures. To improve throughput by overlapping data transfers with kernel execution, multiple CUDA streams are used. Issues with floating point accuracy, random numbers generation, data structure, kernel divergences and register spills are also considered. Performance evaluation for the relative speedup compared to the corresponding sequential execution on CPU is presented as well.