Particle Hits Research Articles

Design of Nupix-A1, a Monolithic Active Pixel Sensor for heavy-ion physics

A Monolithic Active Pixel Sensor (MAPS) named Nupix-A1 has been designed in a 130 nm process for the heavy-ion experiments at HIRFL and HIAF. The Nupix-A1 can simultaneously measure particle hits’ energy, arrival time, and position. The Nupix-A1 consists of 128 × 64 pixels with the size of 30μm×30μm. A configurable DAC array, which consists of four 10-bit voltage DACs and seven 8-bit current DACs, tunes the bias of the in-pixel circuit. The analog signal from the pixels in four adjacent columns is converted into a digital signal by an 11-bit column-parallel ADC. The digitized data is encoded, serialized, and transmitted by the 5 Gbps data transmission link. This paper will discuss the design of the Nupix-A1.

A novel concept for a fully digital particle detector

Silicon sensors are the most diffuse position sensitive device in particle physics experiments and in countless applications in science and technology. They had a spectacular progress in performance over almost 40 years since their first introduction, but their evolution is now slowing down. The position resolution for single particle hits is larger than a few microns in the most advanced sensors. This value was reached already over 30 years ago [1]. The minimum ionising path length a sensor can detect is several tens of microns. There are fundamental reasons why these limits will not be substantially improved by further refinements of the current technology. This makes silicon sensors unsuitable to applications where the physics signature is the short path of a recoiling atom and constrains the layout of physics experiments where they represent by far the best option like high energy physics collider experiments. In perspective, the availability of sensors with sub-micron spatial resolution, in the order of a few tens of nanometres, would be a disruptive change for the sensor technology with a foreseeable huge impact on experiment layout and various applications of these devices. For providing such a leap in resolution, we propose a novel design based on a purely digital circuit. This disruptive concept potentially enables pixel sizes much smaller than 1 μm2 and a number of advantages in terms of power consumption, readout speed and reduced thickness (for low mass sensors).

The Use of ProteoTuner Technology to Study Nuclear Factor κB Activation by Heavy Ions.

Nuclear factor κB (NF-κB) activation might be central to heavy ion-induced detrimental processes such as cancer promotion and progression and sustained inflammatory responses. A sensitive detection system is crucial to better understand its involvement in these processes. Therefore, a DD-tdTomato fluorescent protein-based reporter system was previously constructed with human embryonic kidney (HEK) cells expressing DD-tdTomato as a reporter under the control of a promoter containing NF-κB binding sites (HEK-pNFκB-DD-tdTomato-C8). Using this reporter cell line, NF-κB activation after exposure to different energetic heavy ions (16O, 95 MeV/n, linear energy transfer—LET 51 keV/µm; 12C, 95 MeV/n, LET 73 keV/μm; 36Ar, 95 MeV/n, LET 272 keV/µm) was quantified considering the dose and number of heavy ions hits per cell nucleus that double NF-κB-dependent DD-tdTomato expression. Approximately 44 hits of 16O ions and ≈45 hits of 12C ions per cell nucleus were required to double the NF-κB-dependent DD-tdTomato expression, whereas only ≈3 hits of 36Ar ions were sufficient. In the presence of Shield-1, a synthetic molecule that stabilizes DD-tdTomato, even a single particle hit of 36Ar ions doubled NF-κB-dependent DD-tdTomato expression. In conclusion, stabilization of the reporter protein can increase the sensitivity for NF-κB activation detection by a factor of three, allowing the detection of single particle hits’ effects.

In-orbit performance of UVIT over the past 5 years

Over the last 5 years, UVIT has completed observations of more than 500 proposals with ~ 800 unique pointings. In addition, regular planned monitoring observations have been made and from their analysis various key parameters related to in orbit performance of UVIT have been quantified. The sensitivities of the UV channels have remained steady indicating no effect of potential molecular contamination confirming the adequacy of all the protocols implemented for avoiding contamination. The quality of the PSF through the years confirms adequacy of thermal control measures. The early calibrations obtained during the Performance Verification (PV) phase have been further revised for more subtle effects. These include flat fields and detector distortions with greater precision. The operations of UVIT have also evolved through in orbit experience, e.g. tweaking of operational sequencing, protocol for recovery from bright object detection (BOD) shutdowns, parameters for BOD thresholds, etc. Finally, some effects of charged particle hits on electronics led to opimised strategy for regular resetting. The Near-UV channel was lost in one of such operations. All the above in-orbit experiences are presented here.

Geant4 quartz fiber simulations as part of luminometer development for CMS

Measurements of luminosity are required to be exceedingly accurate for the new upcoming era of the LHC with higher energies and a more complex structure of the beam (HL-LHC). A new device is being developed for the CMS experiment to fulfill demands of being stand-alone and precise. The paper describes the design, main components and physics behind the new quartz fiber based luminometer (QFL). Via simulations of a single quartz fiber, we were able to calculate an average number of photons reaching the end of the fiber after a single particle hit.

Topmetal-M: A novel pixel sensor for compact tracking applications

The Topmetal-M is a large area pixel sensor (18 mm × 23 mm) prototype fabricated in a new 130 nm high-resistivity CMOS process in 2019. It contains 400 rows × 512 columns square pixels with the pitch of 40μm. In Topmetal-M, a novel charge collection method combining the Monolithic Active Pixel Sensor (MAPS) and the Topmetal sensor has been proposed for the first time. Both the ionized charge deposited by the particle in the sensor and along the track over the sensor can be collected. The in-pixel circuit mainly consists of a low-noise charge sensitive amplifier to establish the signal for the energy reconstruction, and a discriminator with a Time-to-Amplitude Converter (TAC) for the Time of Arrival (TOA) measurement. With this mechanism, the trajectory, particle hit position, energy, and arrival time of the particle can be measured. The analog signal from each pixel is accessible through time-shared multiplexing over the entire pixel array. This paper will discuss the design and preliminary test results of the Topmetal-M sensor.

Increase of the particle hit rate in a laser single-particle mass spectrometer by pulse delayed extraction technology

Abstract. A single-particle mass spectrometer (SPMS) can provide a wealth of valuable information on chemical and physical parameters of individual particles in real time. One of the main performance criteria of the instrument is efficiency of particle detection (hit rate). Most SPMS instruments use constant electrical field (DC) extraction, where stationary high voltage is applied to the extraction electrodes. As the aerosol particles initially carry a certain charge, those with a high amount to charge can be deflected by this electric field and lost, thus decreasing the hit rate. We realized that the delayed extraction technique can eliminate the stochastic dispersion of the particle beam caused by their deflection in the stationary electric field. As the result, the hit rate of the instrument can be significantly improved. Also, as the effect of the deflection in the electric field is mass dependent, it can cause distortion of the measured size distribution of the particles. Hence, the delayed extraction technique can bring the recorded distribution closer to the actual one. We found that the delayed extraction technique provides a mass resolution improvement as well as increases the hit rate. The gain in the hit rate depends on the type of particles. It can be 2 orders of magnitude for model particles and up to 2–4 times for ambient particles. In the present work we report experiments and results showing the effect of the delayed extraction on the beam divergence caused by particle charge, the hit rate improvement, and the effect of the delayed extraction on the measured particle size distribution.

A cell-based dosimetry model for radium-223 dichloride therapy using bone micro-CT images and GATE simulations

Dosimetry at the cellular level has outperformed macrodosimetry in terms of agreement with toxicity effects in clinical studies. This fact has encouraged dosimetry studies aiming to quantify the absorbed doses needed to reach radiotoxicity at the cellular level and to inform recommendations on the administration of radium-223. The aim of this work is to qualitatively and quantitatively evaluate the absorbed doses of radium-223 and the interactions of the doses at the cellular level. The analysis was performed by Monte Carlo simulations in GATE using micro-CT image of a mouse. Two physics lists available in the GATE code were tested. The influence of single and multiple scattering models on the absorbed dose distribution and number of particle hits was also studied. In addition, the fuzzy c-means clustering method was used for data segmentation. The segmentation method was suitable for these analyses, particularly given that it was unsupervised. There was no significant difference in the estimated absorbed dose between the two proposed physics lists. The absorbed dose values were not significantly influenced by scattering, although single scattering resulted in twice as many interactions as multiple scattering. The absorbed dose histogram at the voxel level shows heterogeneous absorbed dose values within each shell, but the observations from the graph of the medians were comparable to those in the literature. The interaction histogram indicates 104 events, although some voxels had no interactions with alpha particles. However, the voxels did not show absorbed doses capable of deterministic effects in the deepest part of the bone marrow. The absorbed dose distribution in images of mouse trabecular bone was compatible with simple geometric models, with absorbed doses capable of deterministic effects near the bone surface. The interaction distributions need to be correlated with in vivo studies for better interpretation.

Validating the ASCOT modelling of NBI fast ions in Wendelstein 7-X stellarator

The first fast ion experiments in Wendelstein 7-X were performed in 2018. They are one of the first steps in demonstrating the optimised fast ion confinement of the stellarator. The fast ions were produced with a neutral beam injection (NBI) system and detected with infrared cameras (IR), a fast ion loss detector (FILD), fast ion charge exchange spectroscopy (FIDA), and post-mortem analysis of plasma facing components. The fast ion distribution function in the plasma and at the wall is being modelled with the ASCOT suite of codes. They calculate the ionisation of the injected neutrals and the consecutive slowing down process of the fast ions. The primary output of the code is the multidimensional fast ion distribution function within the plasma and the distribution of particle hit locations and velocities on the wall. Synthetic measurements based on ASCOT output are compared to experimental results to assess the validity of the modelling. This contribution presents an overview of the various fast ion measurements in 2018 and the current modelling status. The validation and data-analysis is on-going, but the wall load IR modelling already yield results that match with the experiments.

Double hit reconstruction in large area multiplexed detectors.

A novel approach is presented to unfold particle hit positions in tracking detectors with multiplexed readout representing an underdetermined system of linear equations. The method does not use any prior information about the hit positions, and the only assumption in the procedure is that single strip charge values on consecutive detector strips follow a smooth distribution. Ambiguities introduced by charge sharing from multiplexing are reduced by using a regularization technique. We have tested this method on a multiplexed 50 × 50 cm2 Micromegas detector with 1037 strips and only 61 readout channels, using cosmic rays, and we have found that single and double clusters of hits can be reconstructed with high efficiency. In addition, simulations show that the algorithm is capable of reconstructing isolated hits in events with larger multiplicity.

Characterization of monolithic CMOS pixel sensor chip with ion beams for application in particle computed tomography

Particle computed tomography (pCT) is an emerging imaging modality that promises to reduce range uncertainty in particle therapy. The Bergen pCT collaboration aims to develop a novel pCT prototype based on the ALPIDE monolithic CMOS sensor. The planned prototype consist of two tracking planes forming a rear tracker and Digital Tracking Calorimeter (DTC). The DTC will be made of a 41 layer ALPIDE-aluminum sandwich structure. To enable data acquisition at clinical particle rates, a large multiplicity of particles will be measured using the highly-granular ALPIDE sensor. In this work, a first characterization of the ALPIDE sensor performance in ion beams is conducted. Particle hits in the ALPIDE sensor result in charge clusters whose size is related to the chip response and the particle energy deposit. Firstly, measurements in a 10 MeV 4He micro beam have been conducted at the SIRIUS microprobe facility of ANSTO to investigate the dependence of the cluster size on the beam position over the ALPIDE pixel. Here, a variation in cluster size depending on the impinging point of the beam was observed. Additional beam tests were conducted at the Heidelberg Ion-Beam Therapy Center (HIT) investigating the cluster size as a function of the deposited energy by protons and 4He ions in the sensitive volume of the ALPIDE. Results show the expected increase in cluster sizes with deposited energy and a clear difference in cluster sizes for protons and 4He ions. As a conclusion, the variation in cluster size with the impinging point of the beam has to be accounted for to enable accurate energy loss reconstruction with the ALPIDE. This does, however, not affect the tracking of particles through the final prototype, as for that only the center-of-mass of the cluster is relevant.

Design and Analysis of SEU Hardened Latch for Low Power and High Speed Applications

Due to the reduction in technology scaling, gate capacitance and charge storage in sensitive nodes are rapidly decreasing, making Complementary Metal Oxide Semiconductor (CMOS) circuits more sensitive to soft errors caused by radiation. In this paper, a low-power and high-speed single event upset radiation hardened latch is proposed. The proposed latch can withstand single event upsets completely when the high energy particle hit on any one of its intermediate nodes. The proposed latch structure comprises of four CMOS feedback schemes and a Muller C-element with clock gating technique. For the sake of comparison, the proposed and the existing latches in the literature are implemented in 45nm CMOS technology. From the post layout simulation results, it may be noted that the proposed latch achieves 8% low power consumption, 95% less delay, and a 94% reduction in power-delay-product compared to the existing single event upset resilient and single event tolerant latches. Monte Carlo simulations show that the proposed latch is less sensitive to process, voltage, and temperature variations in comparison with the existing hardened latches in the literature.

Radiation-Hardened Structure to Reduce Sensitive Range of a Stacked Structure for FDSOI

Flip-flops (FFs) with stacked transistors have high radiation tolerance in a fully depleted silicon on insulator (FDSOI) process. However, the FFs are weak against a radioactive particle hit with high linear energy transfer (LET) and from high incident angles. In this paper, we used heavy-ion irradiation tests to evaluate the soft-error tolerance of a stacked structure and a radiation-hardened structure in an attempt to reduce sensitive range (RSR). We propose a novel FF with the RSR structure. We fabricate a chip in a 65-nm FDSOI process with three latches, each with different distances between stacked transistors. Experimental results reveal that the stacked structures are weak against a heavy-ion hit that exceeds a LET of 60 MeV $\cdot $ cm2/mg even though the distance between stacked transistors was increased from 250 to 350 nm. We evaluated the RSR structure by TCAD simulations and measured the radiation hardness of the proposed FF by heavy-ion irradiation on the fabricated chips. Measurement by heavy ions with LET of 67.2 MeV $\cdot $ cm2/mg at all angles show no detectable errors in the proposed FF.

From Energy Deposition of Ionizing Radiation to Cell Damage Signaling: Benchmarking Simulations by Measured Yields of Initial DNA Damage after Ion Microbeam Irradiation.

Advances in accelerator technology, which have enabled conforming radiotherapy with charged hadronic species, have brought benefits as well as potential new risks to patients. To better understand the effects of ionizing radiation on tumor and surrounding tissue, it is important to investigate and quantify the relationship between energy deposition at the nanometric scale and the initial biological events. Monte Carlo track structure simulation codes provide a powerful tool for investigating this relationship; however, their success and reliability are dependent on their improvement and development accordingly to the dedicated biological data to which they are challenged. For this aim, a microbeam facility that allows for fluence control, down to one ion per cell nucleus, was used to evaluate relative frequencies of DNA damage after interaction between the incoming ion and DNA according to radiation quality. Primary human cells were exposed to alpha particles of three different energies with respective linear energy transfers (LETs) of approximately 36, 85 or 170 keV·µm-1 at the cells' center position, or to protons (19 keV·µm-1). Statistical evaluation of nuclear foci formation (53BP1/γ-H2AX), observed using immunofluorescence and related to a particle traversal, was undertaken in a large population of cell nuclei. The biological results were adjusted to consider the factors that drive the experimental uncertainties, then challenged with results using Geant4-DNA code modeling of the ionizing particle interactions on a virtual phantom of the cell nucleus with the same mean geometry and DNA density as the cells used in our experiments. Both results showed an increase of relative frequencies of foci (or simulated DNA damage) in cell nuclei as a function of increasing LET of the traversing particles, reaching a quasi-plateau when the LET exceeded 80-90 keV·µm-1. For the LET of an alpha particle ranging from 80-90 to 170 keV·µm-1, 10-30% of the particle hits did not lead to DNA damage inducing 53BP1 or γ-H2AX foci formation.

Use of a hybrid semiconductor pixel detector as a precision beam monitor at CERN accelerator facilities

We describe the performance of the Timepix silicon detector operation at the SPS and H8 extracted beam line at CERN. Some detector calibration results and tuning will be discussed and a new cluster analysis algorithm, to reconstruct the particle hits, is described as well. We investigated the optimal acquisition setup for the Timepix device in order to use its full capabilities. A setup of 4 planes of the Timepix hybrid silicon pixel detector is tested as a hodoscope in the H8 180 GeV/c extracted pion beam, and also with a special 3 ns channeled proton bunch sequence inside the SPS accelerator. Spatial and angular distributions are measured.

Development of the readout electronics for the HIRFL-CSR array detectors

This paper presents the readout electronics for the array detectors in the external target facility of the HIRFL-CSR. The readout system is divided into readout partitions, each of which includes four Front-end Cards (FECs) and one Readout Control Unit (RCU). The FEC measures the energy of the particle hit on the detectors and converts it into current signal. The RCU processes the triggers from the central trigger unit, digitizes the raw signal from the FECs, performs data processing algorithms and transmits the data to the data acquisition system in a specified format. The readout electronics has been characterized in the lab and installed in the detectors. The design, implementation and test of the readout electronics has been discussed.

The SpacePix-D radiation monitor technology demonstrator

We present the SpacePix-D, a battery-operated standalone pixel detector with built-in LCD for real-time visualization of particle hits and Bluetooth for wireless access. The SpacePix-D allows the possibility of local and remote operation and it serves as a demonstrator for the new 180 nm SoI monolithic 64 × 64 pixel detection ASICs with hit counting and deposited energy measurement capability. Currently, it operates with the X-chip03 detection ASIC which can be upgraded to a new class of SpacePix pixel detectors. The SpacePix ASIC has been submitted for manufacturing and it was designed for charged particle sensing in the space environment. It features a logarithmic front-end amplifier response to cover a large required dynamic range for heavy ion detection and SEU-hardened digital circuits.

A statistical approach to detect protein complexes at X-ray free\xa0electron laser facilities

The Flash X-ray Imaging (FXI) technique, under development at X-ray free electron lasers (XFEL), aims to achieve structure determination based on diffraction from individual macromolecular complexes. We report an FXI study on the first protein complex—RNA polymerase II—ever injected at an XFEL. A successful 3D reconstruction requires a high number of observations of the sample in various orientations. The measured diffraction signal for many shots can be comparable to background. Here we present a robust and highly sensitive hit-identification method based on automated modeling of beamline background through photon statistics. It can operate at controlled false positive hit-rate of 3 × 10−5. We demonstrate its power in determining particle hits and validate our findings against an independent hit-identification approach based on ion time-of-flight spectra. We also validate the advantages of our method over simpler hit-identification schemes via tests on other samples and using computer simulations, showing a doubled hit-identification power.

Angular Dependence Study of the Cosmic Ray Flux at 900 Meters Above Sea Level

In this study, the zenith angle distribution of the ground level cosmic ray flux have been measured at 900 meters above the sea level by using the developed prototype detector. The mea- surements have been done in Experimental Particle Physics Laboratory, Department of Physics, AIBU Bolu. The method used to carry out the experiment is by using simultaneous particle hits on two scintillator boxes that are arranged in tower mode then counts will accumulate in the scin- tillator counter boxes. This detector prototype provides a simpler, cheaper and suitable alternative to the common cosmic ray detectors for the detection of particles at ground level. The orientation of module is in the south-east direction. The fluxes and rates were measured for different zenith angles between 0o and 90o. The attenuation effect of the architectural components on the mea- sured cosmic ray flux was carried out by using GEANT4 simulation program and this effect was taken into account in the given results.

Combined TCAD and Geant4 simulations of diamond detectors for timing applications

In this work we propose a combined TCAD and Geant4 simulated based numerical model approach to study of the active electrical behavior of 3D diamond sensors with graphitic parallel columns/trenches contact scheme in those radiation detection applications ruled by stringent timing and radiation-tolerance requirements. Single particle hit effects can be realistically assessed in Geant4 simulations describing properly the energy deposition along its path. Such information represents the input to the TCAD tools for analyzing the detectors active response depending on bias, particle type, energy and impact direction. Different contact geometries and transport effects have been accounted for with the equivalent load effect of graphitic columns in mixed-mode simulations for the device performance optimization.