Particle Hits Research Articles

A Lightweight Algorithm to Model Radiation Damage Effects in Monte Carlo Events for High-Luminosity Large Hadron Collider Experiments.

Radiation damage significantly impacts the performance of silicon tracking detectors in Large Hadron Collider (LHC) experiments such as ATLAS and CMS, with signal reduction being the most critical effect; adjusting sensor bias voltage and detection thresholds can help mitigate these effects, generating simulated data that accurately mirror the performance evolution with the accumulation of luminosity, hence fluence, is crucial. The ATLAS and CMS collaborations have developed and implemented algorithms to correct simulated Monte Carlo (MC) events for radiation damage effects, achieving impressive agreement between collision data and simulated events. In preparation for the high-luminosity phase (HL-LHC), the demand for a faster ATLAS MC production algorithm becomes imperative due to escalating collision, events, tracks, and particle hit rates, imposing stringent constraints on available computing resources. This article outlines the philosophy behind the new algorithm, its implementation strategy, and the essential components involved. The results from closure tests indicate that the events simulated using the new algorithm agree with fully simulated events at the level of few %. The first tests on computing performance show that the new algorithm is as fast as it is when no radiation damage corrections are applied.

Deep learning-based spatiotemporal multi-event reconstruction for delay line detectors

Accurate observation of two or more particles within a very narrow time window has always been a challenge in modern physics. It creates the possibility of correlation experiments, such as the ground-breaking Hanbury Brown–Twiss experiment, leading to new physical insights. For low-energy electrons, one possibility is to use a Microchannel plate with subsequent delay lines for the readout of the incident particle hits, a setup called a Delay Line Detector. The spatial and temporal coordinates of more than one particle can be fully reconstructed outside a region called the dead radius. For interesting events, where two electrons are close in space and time, the determination of the individual positions of the electrons requires elaborate peak finding algorithms. While classical methods work well with single particle hits, they fail to identify and reconstruct events caused by multiple nearby particles. To address this challenge, we present a new spatiotemporal machine learning model to identify and reconstruct the position and time of such multi-hit particle signals. This model achieves a much better resolution for nearby particle hits compared to the classical approach, removing some of the artifacts and reducing the dead radius a factor of eight. We show that machine learning models can be effective in improving the spatiotemporal performance of delay line detectors.

MightyPix at the LHCb Mighty Tracker — verificationof an HV-CMOS pixel chip's digital readout

MightyPix is a high voltage complementary metal-oxide-semiconductor (HV-CMOS) active pixel sensor, currently being developed for the Mighty Tracker, an upgrade proposed for LHCb in anticipation of the High Luminosity LHC. To ensure that MightyPix will be able to handle the particle hit rates at the Mighty Tracker, which are expected to reach 17 MHz/cm2, simulations of the chip's digital readout mechanism were performed. Using simulated particle hits the chip's performance within the LHCb environment is characterised. For this, a behavioural model of the first prototype, MightyPix1, representing the analogue pixel matrix, together with the synthesised digital logic is used. Simulation results show the MightyPix1 readout mechanism having an efficiency over 99 % up to 20 MHz/cm2. The bottleneck was found to be the speed at which the hits are read out. This yielded new design ideas to improve the readout for MightyPix2, leading to an efficiency of over 99 % up to 30 MHz/cm2.

Prototype design of a Monolithic Active Pixel Sensor for the Electron-ion collider in China

The Nupix-R1 is a prototype Monolithic Active Pixel Sensor designed for the Electron-ion collider in China. It consists of 128 rows × 128 columns of square pixels with a pitch of 26.3 µm. Since it is implemented in a 130 nm commercial triple-well process, the in-pixel circuit contains only NMOS transistors. The Nupix-R1 can simultaneously measure the energy, arrival time and position of particle hits. In addition, it can also record only the hit positions with a novel zero-compression scheme to increase the readout speed and reduce the data volume. This paper will discuss the design of the Nupix-R1 sensor.

Enhanced RBE of Particle Radiation Depends on Beam Size in the Micrometer Range.

High-linear energy transfer (LET) radiation, such as heavy ions is associated with a higher relative biological effectiveness (RBE) than low-LET radiation, such as photons. Irradiation with low- and high-LET particles differ in the interaction with the cellular matter and therefore in the spatial dose distribution. When a single high-LET particle interacts with matter, it results in doses of up to thousands of gray (Gy) locally concentrated around the ion trajectory, whereas the mean dose averaged over the target, such as a cell nucleus is only in the range of a Gy. DNA damage therefore accumulates in this small volume. In contrast, up to hundreds of low-LET particle hits are required to achieve the same mean dose, resulting in a quasi-homogeneous damage distribution throughout the cell nucleus. In this study, we investigated the dependence of RBE from different spatial dose depositions using different focused beam spot sizes of proton radiation with respect to the induction of chromosome aberrations and clonogenic cell survival. Human-hamster hybrid (AL) as well as Chinese hamster ovary cells (CHO-K1) were irradiated with focused low LET protons of 20 MeV (LET = 2.6 keV/µm) beam energy with a mean dose of 1.7 Gy in a quadratic matrix pattern with point spacing of 5.4 × 5.4 µm2 and 117 protons per matrix point at the ion microbeam SNAKE using different beam spot sizes between 0.8 µm and 2.8 µm (full width at half maximum). The dose-response curves of X-ray reference radiation were used to determine the RBE after a 1.7 Gy dose of radiation. The RBE for the induction of dicentric chromosomes and cell inactivation was increased after irradiation with the smallest beam spot diameter (0.8 µm for chromosome aberration experiments and 1.0 µm for cell survival experiments) compared to homogeneous proton radiation but was still below the RBE of a corresponding high LET single ion hit. By increasing the spot size to 1.6-1.8 µm, the RBE decreased but was still higher than for homogeneously distributed protons. By further increasing the spot size to 2.7-2.8 µm, the RBE was no longer different from the homogeneous radiation. Our experiments demonstrate that varying spot size of low-LET radiation gradually modifies the RBE. This underlines that a substantial fraction of enhanced RBE originates from inhomogeneous energy concentrations on the µm scale (mean intertrack distances of low-LET particles below 0.1 µm) and quantifies the link between such energy concentration and RBE. The missing fraction of RBE enhancement when comparing with high-LET ions is attributed to the high inner track energy deposition on the nanometer scale. The results are compared with model results of PARTRAC and LEM for chromosomal aberration and cell survival, respectively, which suggest mechanistic interpretations of the observed radiation effects.

Variations of single event transient induced by line edge roughness (LER) and temperature in FinFET

The impacts of line edge roughness (LER) and temperature effect on single event transient (SET) in Silicon-On-Insulator (SOI) FinFET at 14 nm technology node are studied. Based on the calibrated model of the rectangle FinFET, all of possible fin structures induced by LER in the vertical direction are proposed by considering the correlation between the line edges. When an energetic particle hits, due to the corporate effects of the gate control capability from the equivalent gate width and the current density from the cross section, thin fin shape represents more immunity to SET with the relative decrement in current peak, collected charge, deposited charge, pulse width and bipolar amplification coefficient by 23.78 %, 31.61 %, 19.16 %, 23.77 % and 15.40 %, respectively. However, the SET responses of big bottom and fat fin structures indicate that they are more sensitive to SET. Because of the driven current increase induced by the inversion of the temperature effect in FinFET, as the environment temperature increases, the SET responses of all of fin shapes decrease and their relative decrements are close. When the temperature increases from 258K to 398K, the average relative decrements in current peak, and collected charge are 24.22 %, 20.90 %, respectively.

Design of Nupix-A2, a Monolithic Active Pixel Sensor for heavy-ion physics

The High Intensity heavy-ion Accelerator Facility (HIAF) is being constructed to generate intense beams of primary and radioactive ion for a wide range of research fields. Hence, a Monolithic Active Pixel Sensor (MAPS) named Nupix-A2 has been developed in a 130-nm High Resistivity CMOS process. The Nupix-A2 can simultaneously measure the particle hit' energy, arrival time, and position. It consists of a 128 × 128 pixel array, a digital-to-analog converter array, and a digital control module. The Nupix-A2 can measure energy deposition from 300 e- to over 50 ke- and time duration from 13 μs to 140 μs. This sensor also offers full readout mode and fast readout mode. In full-readout mode, all pixels measure arrival time and energy, suitable for real-time beam monitoring and image reconstruction. In fast-readout mode, only particle hit's positions are detected and read out. This paper presents the design of the Nupix-A2.

SEU protection design for the prototype readout electronics of MAPS-based STCF inner tracker

The Super Tau Charm Facility (STCF) is a high-luminosity electron-positron collider experiment operating at center-of-mass energy of 2–7 GeV. Its primary goal is to explore flavor physics, CP-violations, and investigate physics beyond the Standard Model. The inner tracker (ITK) is a crucial component of the STCF tracking system, which is responsible for detecting particle hits, especially those with low momentum below 100 MeV/c. Its primary objectives include providing high detection efficiency and spatial resolution for charged particle tracks. However, the electronics of ITK is susceptible to single-event upset (SEU) caused by beam-related background. To address this, this paper presents a prototype of FPGA (Field Programmable Gate Array)-based electronics that can detect and automatically repair SEU induced soft errors in its Configuration Random Access Memory (CRAM) and whose Block Random Access Memory (BRAM) has been also subjected to commonly used hardening techniques. Importantly, the prototype's corrective operations do not result in any dead time due to hot redundancy backup. In the laboratory environment, we measured the bit error rate of the data transmission to be lower than 10-12 with a confidence level of 99.99%. Through neutron beam experiments conducted at China Spallation Neutron Source (CSNS) back-n white neutron source. We demonstrated that the readout electronics can effectively restore correct functionality and promptly rectify soft errors.

Evaluating Generative Adversarial Networks for particle hit generation in a cylindrical drift chamber using Fréchet Inception Distance

We use Fréchet Inception Distance (FID) measured in the latent spaces of pre-trained, fine-tuned and custom-made inception networks to evaluate Generative Adversarial Networks (GANs) developed by the COherent Muon to Electron Transition (COMET) collaboration to generate sequences of background hits in a Cylindrical Drift Chamber (CDC). We validate the convergence of the GANs' training and show that the use of self-attention layers reduces FID. Our method enables the use of FID as an evaluation metric even when an application-specific inception network is not readily available, making it transferable to other GAN applications in High Energy Physics.

Design of an SHA-Less Pipeline ADC With Op-Amp Sharing Techniques for MAPS

As the leading research platform of heavy-ion science in China, the heavy-ion physics and applications at the Heavy Ion Research Facility in Lanzhou (HIRFL) and the High-Intensity heavy-ion Accelerator Facility (HIAF) drive the development of new detector technology. A monolithic active pixel sensor (MAPS) has been designed in a 130-nm CMOS process for HIRLF and HIAF. This MAPS can measure the energy deposition and position of the particle hit. As the critical component of this MAPS, a regional 12-bit 40-Msps pipeline ADC has been designed to convert the analog signals from the pixels into digital data. Due to the strict limitation on power and area, this ADC adopts the SHA-less architecture and stepwise capacitance reduction. Also, the op-amp sharing technology is used in the 1.5-bit stages. This ADC has a power consumption of 60 mW and occupies <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$874\times 550\,\,\mu \text{m}$ </tex-math></inline-formula> . Simulation results indicate that it achieves an ENOB of 11.77 bits and a SINAD of 72.57 dB at the tt corner with an input frequency of 3.291 MHz. The figure of merits (FOM) value is 507 fJ/step.

Design of the readout electronics system with high event rate based on the Micromegas Detector

This paper presents a multi-channel readout electronic system with a high event rate. Its primary purpose is to meet the increasing collision luminosity in large particle physics collision experiments in recent years, thus bringing about the requirement of high event rates for readout electronics systems. This system is designed for Micromegas detectors and consists of front-end readout boards (FEB) and a data acquisition board (DAQ). It realizes that at 128 channels simultaneous readout, each channel can work at the maximum 2.2 Mhits/s event rate. Each event data contains amplitude and time information, which is read out by FEB. The event data will be sent to DAQ by the GTX transceiver at 3.2 Gbps and then transferred to the data acquisition software. In the data acquisition software, each particle hit position and track will be analyzed and reconstructed. The specific characteristics and implementations of this readout electronic system are described in detail.

Эталонное моделирование как метод решения нелинейных задач

In this paper, the method of reference modeling is considered, designed for calculation, analysis and mathematical modeling of nonlinear physical phenomena and technological processes. The advantages of this method, the possibility of its application in the entire range of basic parameters of a nonlinear problem, the uniformity of the design scheme for all types of problems are formulated. The proposed method is used to create models of convective diffusion in an inhomogeneous medium, scattering of thermal electrons in a field with central symmetry, and the behavior of electrical conductivity depending on temperature and dielectric permittivity of wide-band semiconductors. The problem of calculating the transparency of a potential barrier that a particle hits, considered as a test, gave a good result (an error in the range of 0.8-1.2%). In this paper, the main features of using the reference modeling method for solving nonlinear differential equations are demonstrated. The obtained results of analysis and modeling allow us to confidently assess the reliability of the general ideas of the reference modeling method, its design scheme, as well as the convergence of its decompositions, the similarity criteria of the system under study and the selected model. The method proposed in this paper, taking into account its approbation in various conditions, can serve as a basis for application in the study of nonlinear problems of various nature, finding approximate solutions to nonlinear differential equations.

Test and characterisation of STS/MuCh-XYTER and integration with multiple detectors of CBM-MuCh detector systems

Compressed Baryonic Matter (CBM) is a fixed target experiment at the upcoming Facility for Anti-proton and Ion Research in Germany, having collision rates up to 10 MHz. Due to the proximity of the target and secondaries produced in absorbers, Muon Chambers (MuCh) of the CBM experiment will face a very high particle hit rate of up to 400 kHz/cm2 in its first two stations. To cope with these particle rates, a Gas Electron Multiplier (GEM) detector will be used for the first two stations while, due to relatively lower particle rates, the last two stations will use a low resistivity Bakelite Resistive Plate Chamber (RPC) detector. The electronics of these two MuCh detectors need different dynamic ranges.A Silicon Tracking Station (STS) system made of 300 μm thick silicon micro-strip sensors will be installed upstream of the MuCh detector system. The sensors will be read out through multi-line micro-cables with fast electronics. The micro-strip sensors will be double-sided with a stereo angle of 7.5°, a strip width of 58 μm, and strip lengths between 20 and 120 mm requiring high-density readout.To meet the high rate and high density requirements of MuCh and STS, respectively, a specialized 128-channel readout ASIC with a dual-gain feature is designed. This is a highly configurable ASIC with about 30,000 configurable register bits which control various bias and threshold settings of the ASIC. To integrate this ASIC with both the detector systems, detailed testing and characterization of the ASIC are required.Due to the high number of configurable registers and several operating conditions, characterizing this ASIC is very challenging. This paper describes the optimization procedures of several configurable bias parameters in detail and also explains how this ASIC is integrated with both GEM and RPC detectors of the MuCh system.

Application of deep learning neural networks for the analysis of fluid-particle dynamics in fibrous filters

A novel hybrid data-driven framework was introduced in this study for the prediction of fluid-particle dynamics of submicron particles under hydrodynamic and Brownian forces in fibrous filters. The distribution of flow parameters was predicted by a high-resolution flow surrogate model based on a deep convolutional neural network (CNN) coupled with a Lagrangian particle tracking method based on the discrete phase model (DPM). The CNN-DPM model was applied to a group of several nonuniformly distributed fibers to calculate filtration efficiency. For CNN training, ground-truth data were obtained using a two-dimensional computational fluid dynamics (CFD) model for laminar incompressible flow. A simulation speedup of three orders of magnitude was obtained by CNN for predicting the velocity components and static pressure distribution within an error range of ±10%. The generalizability of CNN model was also confirmed for overlapped irregular fiber shapes and porosities out of the range of the training dataset with deviations in a range of ±20% in comparison with CFD results. The collection efficiency by CNN-DPM for small particle diameters with dp≤0.3μm was overestimated by approximately 3 % while agreeing well with CFD-DPM for larger particles. The errors of flow velocity predictions by CNN near the fibers added more randomness to the particle motion which was combined with the random Brownian motion of particles, consequently increasing the probability of the small particle hit number and filtration efficiency. The overall acceptable accuracy of the CNN-DPM was confirmed, which is suitable for fibrous filter design and optimization purposes that require thousands of simulations.

Transistor-Level Radiation Hardening by Design Techniques in Complex Gates

Single Event Transients (SETs) have become a major reliability concern for integrated circuits used in critical applications. Research to improve the radiation robustness of digital circuits has been conducted, assessing all abstraction levels (from the device up to the system). This study evaluates transistor-level radiation-hardened techniques in combinational logic, such as transistor folding, sizing and reordering. In addition, the efficiency of using supergates, including series-parallel and non-series-parallel CMOS structures, to harden the combinational logic is discussed. The dependence of input signals probability on a logic cell susceptibility to SET is assessed. Moreover, a new concept of electrical masking is introduced. The robustness of the investigated logic cells was evaluated regarding their SET rate. The CREME96 tool was used to generate the SET rates, and an electrical model was used to perform particle hit simulations. Obtained results have indicated that modifying the structure of logic gates can substantially improve circuit robustness without necessarily worsening its performance. Besides, using supergates in combinational logic design has demonstrated to be a promising hardening strategy. The most robust supergate implementation of a five-input logic function provided up to [Formula: see text] SET rate reduction regarding an approach based on standard cells, along with lower critical delay ([Formula: see text]) and average power ([Formula: see text]).

Module development for the ATLAS Phase II Pixel Inner Tracker

The ATLAS experiment will undergo substantial upgrades to cope with the higher radiation environment and particle hit rates foreseen for HL-LHC. The phase II upgrade will include the replacement of the inner detector with a completely new silicon-based tracker. The ATLAS phase II Inner Tracker (ITk) will consist of hybrid pixel detectors and silicon strip detector layers. The innermost five-barrel layers and several endcap rings will be equipped with hybrid pixel detector modules. The modules are consisting of bare silicon modules connected to flexible printed circuits. Bare silicon modules are made of a silicon pixel sensor connected to either four FE chips to form a quad module or one FE chip to form a single chip module. The ITk phase II pixel community has conducted many developments geared towards meeting the necessary module production quality and throughput. These include establishing quality checking routines of bare module components, tooling developments for their assembly as well as electrical testing infrastructure to assess their operability to specification. A dedicated program to set in motion this effort and streamline these various stages was established using the RD53A front-end chip. Subsequent test and assembly work is being carried out using the ITkPix chips which are final size FE chips. This contribution will provide a detailed overview of these developments and their results in preparation for the ATLAS ITk pixel phase II upgrade module production.

On the effectiveness of proton boron fusion therapy (PBFT) at cellular level

The present work introduced a framework to investigate the effectiveness of proton boron fusion therapy (PBFT) at the cellular level. The framework consisted of a cell array generator program coupled with PHITS Monte Carlo package with a dedicated terminal-based code editor that was developed in this work. The framework enabled users to model large cell arrays with normal, all boron, and random boron filled cytoplasm, to investigate the underlying mechanism of PBFT. It was found that alpha particles and neutrons could be produced in absence of boron mainly because of nuclear reaction induced by proton interaction with 16O, 12C and 14N nuclei. The effectiveness of PBFT is highly dependent on the incident proton energy, source size, cell array size, buffer medium thickness layer, concentration and distribution of boron in the cell array. To quantitatively assess the effectiveness of PBFT, of the total energy deposition by alpha particle for different cases were determined. The number of alpha particle hits in cell cytoplasm and nucleus for normal and 100 ppm boron were determined. The obtained results and the developed tools would be useful for future development of PBFT to objectively determine the effectiveness of this treatment modality.

The CMS Inner Tracker electronics system development

A new Silicon Tracker will be built for the phase-2 upgrade of the CMS experiment. The innermost part, called the Inner Tracker, will be featuring high-granularity pixelated silicon sensors of 2500 µm2 and will need to cope with the unprecedented radiation levels of 1.9 Grad and 3.5 × 1016 neq/cm2 fluence and particle hit rates of 3.2 GHz/cm2. The pixel electronics system is based on innovative solutions such as a radiation hard pixel ASIC, the novel serial powering scheme used to power up to 12 detector modules in series and advanced technologies for the high bandwidth readout system based on electrical light-weight readout links of 1.28 Gbps, electrical to optical conversion as close as possible to the detector modules and back-end boards each one capable of receiving an aggregated data bandwidth of 190 Gbps. The recently optimised design of the CMS Inner Tracker electronics system will be presented in this contribution.

Small-scale dosimetry for alpha particle 241Am source cell irradiation and estimation of γ-H2AX foci distribution in prostate cancer cell line PC3

BackgroundThe development of new targeted alpha therapies motivates improving alpha particle dosimetry. For alpha particles, microscopic targets must be considered to estimate dosimetric quantities that can predict the biological response. As double-strand breaks (DSB) on DNA are the main cause of cell death by ionizing radiation, cell nuclei are relevant volumes necessary to consider as targets. Since a large variance is expected of alpha particle hits in individual cell nuclei irradiated by an uncollimated alpha-emitting source, the damage induced should have a similar distribution. The induction of DSB can be measured by immunofluorescent γ-H2AX staining. The cell γ-H2AX foci distribution and alpha particle hits distribution should be comparable and thereby verify the necessity to consider the relevant dosimetric volumes.MethodsA Monte Carlo simulation model of an 241Am source alpha particle irradiation setup was combined with two versions of realistic cell nuclei phantoms. These were generated from DAPI-stained PC3 cells imaged with fluorescent microscopy, one consisting of elliptical cylinders and the other of segmented mesh volumes. PC3 cells were irradiated with the 241Am source for 4, 8 and 12 min, and after 30 min fixated and stained with immunofluorescent γ-H2AX marker. The detected radiation-induced foci (RIF) were compared to simulated RIF.ResultsThe mesh volume phantom detected a higher mean of alpha particle hits and energy imparted (MeV) per cell nuclei than the elliptical cylinder phantom, but the mean specific energy (Gy) was very similar. The mesh volume phantom detected a slightly larger variance between individual cells, stemming from the more extreme and less continuous distribution of cell nuclei sizes represented in this phantom. The simulated RIF distribution from both phantoms was in good agreement with the detected RIF, although the detected distribution had a zero-inflated shape not seen in the simulated distributions. An estimate of undetected foci was used to correct the detected RIF distribution and improved the agreement with the simulations.ConclusionTwo methods to generate cell nuclei phantoms for Monte Carlo dosimetry simulations were tested and generated similar results. The simulated and detected RIF distributions from alpha particle-irradiated PC3 cells were in good agreement, proposing the necessity to consider microscopic targets in alpha particle dosimetry.

Study and characterisation of pad-based readout for RPC detector

The Resistive Plate Chamber (RPC) is a parallel plate avalanche type particle detector which uses a gas mixture as its active detection medium. While high resistivity materials like glass or bakelite plates are commonly used as the detector electrodes, plastic core-based and metal foil laminated pickup panels with segmented strips are used to readout the induced signals. Large area RPCs (of dimension 2 m× 2 m) of this design are chosen as the active detector elements for the India-based Neutrino Observatory's (INO) magnetised Iron Calorimeter (ICAL) detector. One of the main goals of the ICAL detector is a precision measurement of neutrino oscillation parameters. As part of the ongoing detector R&D, a pad-based — instead of strip-based readout — scheme is being developed to improve localization of particle hit positions, while retaining good charge profile and noise rate characteristics of the strip-based RPC based detectors.