High Energy Physics Detectors Research Articles

Deterministic Light Yield, Fast Scintillation, and Microcolumn Structures in Lead Halide Perovskite Nanocrystals

Lead halide perovskite (LHP) nanocrystals (NCs) have recently attracted attention due to both their high quantum yield and their potential for X-ray imaging applications. In this paper, we investigated the scintillation properties of three different LHP NCs; CsPbBr3, FAPbBr3, and CsPbI3. The featured NCs exhibited high X-ray excited luminescence (XL) at cryogenic temperatures. While FAPbBr3 and CsPbI3 NCs display thermal quenching, CsPbBr3 NCs show negative thermal quenching and high XL at high temperatures, with a light yield of 24,000 ± 2,100 photons/MeV at 300 K. The LHP NCs exhibit a small afterglow and low trap density and exhibit a very fast XL decay time, under 20 ns, faster than those of some currently used commercial scintillators. Overall, CsPbBr3 NCs are the best performing materials investigated here, making them particularly attractive for fast-timing applications such as positron emission tomography or particle detectors in high-energy physics. In the end, we demonstrate the proof of concept for using a CsPbBr3 NC matrix for imaging applications and the flexibility of NCs for developing microstructure scintillators.

Cosmic ray flux and lockdown due to COVID-19 in Kolkata - Any correlation?

Cosmic ray muon flux is measured by the coincidence technique using plastic scintillation detectors in the High Energy Physics Detector Laboratory at Bose Institute, Kolkata. Due to the COVID-19 outbreak and nationwide complete lockdown, the laboratory was closed from the end of March 2020 till the end of May 2020. After lockdown, although the city is not in its normal state, we still were able to take data on some days. The lockdown imposed a strict restriction on the transport service other than the emergency ones and also most of the industries were shut down in and around the city. This lockdown has significant effect on the atmospheric conditions in terms of change in the concentration of air pollutants. We have measured the cosmic ray flux before and after the lockdown to observe the apparent change if any, due to change in the atmospheric conditions. In this article, we report the measured cosmic ray flux at Kolkata (22.58^{circ }N 88.42^{circ }E and 11 m above the Sea Level) along with the major air pollutants present in the atmosphere before and after the lockdown.

Characterization of Crystalline CsPbBr3 Perovksite Dosimeters for Clinical Radiotherapy

Lead halide perovskite CsPbBr3 is a wide-gap semiconductor material potentially very attractive for next generations of real-time monitors and particle detectors in high-energy physics. Here, we present the first characterization of crystalline CsPbBr3 point dosimeters with submillimeter size, under 6 MV X-photon beams used in clinical radiotherapy. Current response of the devices proved to be promising in terms of fast rise and decay times, of the same order of the X-ray beam onset and offset ones; absence of polarization effects; reproducibility to repeated irradiations; and linearity of the collected charge as a function of the absorbed dose. Comparing the measured sensitivity with the theoretical one, a charge collection distance of about 100 μm has been evaluated, of the same order of the linear dimensions of crystallites within the samples, suggesting that recombination centers are mainly placed at grain boundaries. A much higher sensitivity per unit area measured with crystalline CsPbBr3 as compared with drop-casted ones can be explained in terms of a less disordered crystalline structure. This work opens the way to CsPbBr3 point dosimeters, with linear dimensions meeting the strict spatial resolution constraints for bidimensional dose mapping required in clinical radiotherapy.

Wafer Level Packaging Technology Applied to Pixel Detectors

Pixel technology is commonly used in the tracking systems of High Energy Physics detectors with physical areas that have largely increased in the last decades. To ease the production of several square meters of sensitive area, the possibility of using the industrial Wafer Level Packaging to reassemble good single sensor tiles from multiple wafers into a reconstructed full wafer is investigated. This process reconstructs wafers by compression molding using silicon charged epoxy resin. We tested high glass transition temperature low-stress epoxy resins filled with silica particles to best match the thermal expansion of the silicon die. These resins are developed and characterized for industrial processes, designed specifically for fan-out wafer-level package and panel-level packaging. In order to be compatible with wafer processing during the hybridization of the pixel detectors, such as the bump-bonding, the reconstructed wafer must respect challenging technical requirements. Wafer planarity, tile positioning accuracy, and overall thickness are amongst the main ones. In this paper the description of the process is given and preliminary results on a few reconstructed wafers using dummy tiles are reported. Strategies for Wafer Level Packaging improvements are discussed together with future applications to 3D sensors or CMOS pixel detectors.

High Energy Physics Calorimeter Detector Simulation Using Generative Adversarial Networks With Domain Related Constraints

Generative Adversarial Networks (GANs) have gained notoriety by generating highly realistic images. The present work explores GAN for simulating High Energy Physics detectors, interpreting detector output as three-dimensional images. The demands and requirements of a scientific simulation are quite stringent, as compared to the domain of visual images. Image characteristics such as pixel intensity and sparsity, for example, have very different distributions. Moreover, detector simulation requires conditioning on physics inputs, and domain knowledge becomes essential. We, therefore, adjust the pre-processing and incorporate physics-based constraints in the loss function. We also introduce a multi-step training process based on transfer learning by breaking up the task complexity. Validation of the results primarily consists of a detailed comparison to full Monte Carlo in terms of several physics quantities where a high level of agreement is found (ranging from a few percent up to 10% across a large particle energy range). In addition, we assess the performance by physics unrelated metrics, thereby proving further the variability and pertinence through diverse standpoints. We have demonstrated that an image generation technique from vision can successfully simulate highly complex physics processes while achieving a speedup of more than three orders of magnitude in comparison to the standard Monte Carlo.

Novel features and GPU performance analysis for EM particle transport in the Celeritas code

Celeritas is a new computational transport code designed for high-performance simulation of high-energy physics detectors. This work describes some of its current capabilities and the design choices that enable the rapid development of efficient on-device physics. The abstractions that underpin the code design facilitate low-level performance tweaks that require no changes to the higher-level physics code. We evaluate a set of independent changes that together yield an almost 40% speedup over the original GPU code for a net performance increase of 220× for a single GPU over a single CPU running 8.4M tracks on a small demonstration physics app.

Humidity Sensors for High Energy Physics Applications: A Review

Modern silicon-based detectors for high-energy physics operate in an experimental environment with sub-zero temperatures. At those temperatures, even low traces of humidity will produce vapor condensation with damages to the detectors. Monitoring relative humidity is then a requirement for efficient detector operation. However, the performance of any relative humidity sensor operating in high-energy physics detectors is highly degraded in time due to high radiation doses. Therefore, this paper provides a comprehensive review of all the humidity sensors that have been tested so far for use in high-energy physics applications. Different working-principles of the tested humidity sensors are introduced as well as the description of the radiation effects on the sensing materials. Actually, there are only few publications in literature about humidity sensors as related to this novel and challenging application, while it becomes increasingly important to keep under control the performance-degradation of any silicon-based detector in most advanced high-energy physics.

Object condensation: one-stage grid-free multi-object reconstruction in physics detectors, graph, and image data

High-energy physics detectors, images, and point clouds share many similarities in terms of object detection. However, while detecting an unknown number of objects in an image is well established in computer vision, even machine learning assisted object reconstruction algorithms in particle physics almost exclusively predict properties on an object-by-object basis. Traditional approaches from computer vision either impose implicit constraints on the object size or density and are not well suited for sparse detector data or rely on objects being dense and solid. The object condensation method proposed here is independent of assumptions on object size, sorting or object density, and further generalises to non-image-like data structures, such as graphs and point clouds, which are more suitable to represent detector signals. The pixels or vertices themselves serve as representations of the entire object, and a combination of learnable local clustering in a latent space and confidence assignment allows one to collect condensates of the predicted object properties with a simple algorithm. As proof of concept, the object condensation method is applied to a simple object classification problem in images and used to reconstruct multiple particles from detector signals. The latter results are also compared to a classic particle flow approach.

PulseDL: A reconfigurable deep learning array processor dedicated to pulse characterization for high energy physics detectors

Neural network models show promising speed and accuracy for online and on-site data analysis in high energy physics. In this report, we discuss a multi-functional neural computing chip called PulseDL for measurement of pulse characteristics. We adopted a structure with outside RISC CPU and processing engines in PulseDL for balanced power and performance. Digital logic at register transfer level was specially designed with emphasis on thread level parallelism. Based on the hardware scheme, we co-designed the network architecture to best utilize the on-chip resources. Convolution, deconvolution and fully-connected matrix multiplication of the network were fitted into the hardware with reconfiguration during runtime. The chip has been taped out under the GSMCR013 130 nm process, with 4.9 mm × 4.9 mm area, at least 25 MHz working frequency and 1.2 V core voltage. Measured by post-layout simulations, the peak power efficiency of the chip was estimated to be about 12 giga operations per second per watt.

Geometry optimization of a muon-electron scattering detector

A high-statistics determination of the differential cross section of elastic muon-electron scattering as a function of the transferred four-momentum squared, dσel(μe→μe)/dq2, has been argued to provide an effective constraint to the hadronic contribution to the running of the fine-structure constant, Δαhad, a crucial input for precise theoretical predictions of the anomalous magnetic moment of the muon. An experiment called ‘‘MUonE’’ is being planned at the north area of CERN for that purpose. We consider the geometry of the detector proposed by the MUonE collaboration and offer a few suggestions on the layout of the passive target material and on the placement of silicon strip sensors, based on a fast simulation of elastic muon-electron scattering events and the investigation of a number of possible solutions for the detector geometry. The employed methodology for detector optimization is of general interest as it may be applied to the design of task-specific detectors for high-energy physics, nuclear physics, and astro-particle physics applications.

A Photomultiplier With an AlGaN Photocathode and Microchannel Plates for BaF2 Scintillator Detectors in Particle Physics

Barium fluoride (BaF2) crystals are considered as a candidate scintillator for scintillation detectors in high-energy physics because of high radiation hardness and short decay time (< 1 ns) of the fast emission component. However, the high level of the slow emission component can deteriorate the detector time resolution. Special approaches are required to decrease this slow component. Using solar-blind photodetectors is one of the possible solutions. In this article, we describe a solar-blind photomultiplier with microchannel plates (MCP) that uses an aluminum gallium nitride (AlGaN) photocathode and a complete scintillation detector channel with a BaF2 crystal and the photomultiplier. The results of the cosmic-ray tests are presented that show the efficiency of detection of the BaF2 fast emission component and suppression of the slow one in the proposed scintillation detector.

Dual-threshold Time-over-Threshold nonlinearity correction for PET detectors

The Time-over-Threshold (ToT) analog-to-digital signal processing approach provides a power-efficient and cost-effective technique to extract all relevant information from detectors in high-energy physics and Positron Emission Tomography (PET) imaging. In this work, three calibration methods were investigated to correct the inherent nonlinear response of the ToT data using 1) γ-ray sources of various energies, 2) internal electronic gain variation in the LabPET II ASIC in combination with a single energy γ-ray source, and 3) internal gain variation along with an embedded pulse charge generator in replacement of a γ-ray source. The electronic gain calibration technique was shown to achieve equivalent correction accuracy as the γ-ray sources calibration. Furthermore, this method has the advantage of allowing a faster calibration requiring only one single γ-ray source (e.g., 511 keV) and a quick automated routine to sweep the internal gain. The last technique would be the most convenient method, provided that the signal pulse shape would be similar to the detector signal responding to a typical γ-ray event. Whereas the concept was demonstrated with a step pulse, extensive processing would be required to recover the nonlinearity correction factors for the detector pulse shape. After calibration, the 511-keV energy resolution of typical LabPET II detectors was only slightly degraded, by less than 12% and 8% for methods 1) and 2), respectively, relative to a conventional ADC-based data acquisition system. The feasibility of fast and accurate calibration for the nonlinearity correction of ToT data in PET imaging was demonstrated, making a daily quality control within reach.

Evolution of the design of ultra fast silicon detector to cope with high irradiation fluences and fine segmentation

The recent development in the design of Ultra Fast Silicon Detector (UFSD), aimed at combining radiation resistance up to fluences of 1015 neq/cm2 and fine read-out segmentation, makes these sensors suitable for high energy physics applications. UFSD is an evolution of standard silicon sensor, optimized to achieve excellent timing resolution (∼30 ps), thanks to an internal low gain (∼20). UFSD sensors are n in p Low Gain Avalanche Diode (LGAD) with an active thickness of ∼5 μm. The internal gain in LGAD is obtained by implanting an appropriate density of acceptors (of the order of ∼ 1016/cm3) close to the p-n junction, that, when depleted, locally generates an electric field high enough to activate the avalanche multiplication; this layer of acceptors is called gain layer. The two challenges in the development of UFSD for high energy physics detectors are the radiation hardness and the fine segmentation of large area sensors. Irradiation fluences of the order of 1015 neq/cm2 have a dramatic effect on the UFSD: neutrons and charged hadrons reduce the active acceptor density forming the gain layer; this mechanism, called initial acceptor removal, causes the complete disappearance of the internal gain above fluence of 1015 neq/ cm2. For the segmentation of UFSDs, the crucial point is the electrical insulation of pads and the extension of the inactive area between pads. In this paper we present the latest results on radiation resistance of LGADs with different gain layer designs, irradiated up to 3⋅1015 neq/ cm2. Three different segmentation technologies, developed by Fondazione Bruno Kessler in Trento, will also be discussed in detail in the second part of the paper.

New CAEN R&D for power supplies and data acquisition systems

Since over 40 years, delivering state of art Power Supplies and Acquisition Systems for Nuclear, Cosmic and High Energy Physics detectors has been the constant mission of the CAEN R&D groups, working closely with the relevant scientists of major research labs worldwide. This paper will focus on some of these R&Ds concerning new power supplies specifically designed for the HL-LHC and new solutions for data acquisition in large experiments thanks to a modular approach or faster digitizers with open FPGA. The new power supply system, EASY6000, is introduced along its main new features like higher radiation tolerance to safely operate thru the whole LHC life span. Furthermore, the new system power density and efficiency in hostile environment are also analyzed, to better understand how much power can be directly delivered to the front-end of new detectors, moreover the communication link between the experiments and the control rooms is also reviewed. Among the data acquisition solutions a new family of digitizers is introduced featuring open FPGA and faster performance. Alongside, the Front End and Readout System (FERS) is presented: this new architecture provides a scalable and easy customizable data acquisition system, the concept is therefore introduced and the first prototypes are described, with their main characteristics.

Novel low resistivity glass: MRPC detectors for ultra high rate applications

Multigap Resistive Plate Chambers (MRPCs) are often used as time-of-flight (TOF) detectors for high-energy physics and nuclear experiments thanks to their excellent time accuracy. For the Compressed Baryonic Matter (CBM) TOF system, MRPCs are required to work at particle fluxes on the order of 1–10kHz/cm2 for the outer region and 10–25kHz/cm2 for the central region. Better time resolution will allow particle identification with TOF techniques to be performed at higher momenta. From our previous studies, a time resolution of 25ps has been obtained with a 20-gap MRPC of 140μm gap size with enhanced rate capability. By using a new type of commercially available thin low-resistivity glass, further improvement MRPC rate capability is possible. In order to study the rate capability of the 10-gap MRPC built with this new low-resistivity glass, we have performed tests using the continuous electron beam at ELBE. This 10-gap MRPC, with 160μm gaps, reaches 97% efficiency at 19.2kV and a time resolution of 36ps at particle fluxes near 2kHz/cm2. At a flux of 100kHz/cm2, the efficiency is still above 95% and a time resolution of 50ps is obtained, which would fulfil the requirement of CBM TOF system.

CMS Experience with Adoption of the Community supported DD4hep Toolkit

DD4hep is an open-source software toolkit that provides comprehensive and complete generic detector descriptions for high energy physics (HEP) detectors. The Compact Muon Solenoid collaboration (CMS) has recently evaluated and adopted DD4hep to replace its custom detector description software. CMS has demanding software requirements as a very large, longrunning experiment that must support legacy geometries and study many possible upgraded detector designs of a constantly evolving detector that will be taking data for many years to come. CMS has chosen DD4hep since it is a high-quality, community-supported solution that will benefit from continuing modernization and maintenance. This presentation will discuss the issues of DD4hep adoption, the advantages and disadvantages of the various design choices, performance results, and the integration of the plugin systems from CMS and Gaudi, another open-source software framework. Recommendations about DD4hep based upon the CMS use cases will also be presented.

EUDAQ—a data acquisition software framework for common beam telescopes

EUDAQ is a generic data acquisition software developed for use in conjunction with common beam telescopes at charged particle beam lines. Providing high-precision reference tracks for performance studies of new sensors, beam telescopes are essential for the research and development towards future detectors for high-energy physics. As beam time is a highly limited resource, EUDAQ has been designed with reliability and ease-of-use in mind. It enables flexible integration of different independent devices under test via their specific data acquisition systems into a top-level framework. EUDAQ controls all components globally, handles the data flow centrally and synchronises and records the data streams. Over the past decade, EUDAQ has been deployed as part of a wide range of successful test beam campaigns and detector development applications.

Radiation Tolerance of Capacitive Humidity Sensor for High-Energy Physics Applications

This letter proposes a sensor candidate for measurements of relative humidity in environments under high-radiation doses, such as high-energy physics detector’ chambers. The sensor performance has been tested at CERN facility under high radiation doses by emulating the situations that will be present in an operating silicon-based detector. At irradiation facility, several humidity sensors were exposed to direct proton beam. The results of the tests show good radiation tolerance and ability of these sensors to operate in radiation exposed conditions.

Status of the Horizon 2020 EuPRAXIA conceptual design study*This work was supported by the European Union’s Horizon 2020 Research and Innovation programme under grant agreement No. 653782.

The Horizon 2020 project EuPRAXIA (European Plasma Research Accelerator with eXcellence In Applications) is producing a conceptual design report for a highly compact and cost-effective European facility with multi-GeV electron beams accelerated using plasmas. EuPRAXIA will be set up as a distributed Open Innovation platform with two construction sites, one with a focus on beam-driven plasma acceleration (PWFA) and another site with a focus on laser-driven plasma acceleration (LWFA). User areas at both sites will provide access to free-electron laser pilot experiments, positron generation and acceleration, compact radiation sources, and test beams for high-energy physics detector development. Support centres in four different countries will complement the pan-European implementation of this infrastructure.

Custom Scrubbing for Robust Configuration Hardening in Xilinx FPGAs

The usage of SRAM-based Field Programmable Gate Arrays on High Energy Physics detectors is mostly limited by the sensitivity of these devices to radiation-induced upsets in their configuration. These effects may alter the functionality until the next reconfiguration of the device. In this work, we present the radiation testing of a high-speed serial link hardened by a new, custom scrubber designed for Xilinx FPGAs. We compared the performance of our scrubber to the Xilinx Single Event Mitigation (SEM) controller and we measured the impact of the scrubbers on the reliability of the link. Our results show that our scrubber may improve reliability up to 23 times over the SEM.