Simulation of the Recording of the Brightest Gamma-ray Burst GRB 221009A by a Segmented Scintillation Detector

The Atomic Spectroscopy and Collisions Using Slow Antiprotons experiment at the Antiproton Decelerator (AD) facility of CERN constructed segmented scintillators to detect and track the charged pions which emerge from antiproton annihilations in a future superconducting radiofrequency Paul trap for antiprotons. A system of 541 cast and extruded scintillator bars were arranged in 11 detector modules which provided a spatial resolution of 17 mm. Green wavelength-shifting fibers were embedded in the scintillators, and read out by silicon photomultipliers which had a sensitive area of 1 × 1 mm(2). The photoelectron yields of various scintillator configurations were measured using a negative pion beam of momentum p ≈ 1 GeV/c. Various fibers and silicon photomultipliers, fiber end terminations, and couplings between the fibers and scintillators were compared. The detectors were also tested using the antiproton beam of the AD. Nonlinear effects due to the saturation of the silicon photomultiplier were seen at high annihilation rates of the antiprotons.

Purpose: To study the imaging characteristics of thick, segmented, 2‐D CdWO4 crystal‐photodiode detectors as a function of crystal height, septa material and optical reflectivity, x‐ray beam spectrum and beam divergence using a two‐step Monte Carlo approach involving both x‐ray photon transport at megavoltage (MV) energies and the optical photon transport in scintillator and photodiodes. Method and Materials: We have studied the spatial frequency dependent detective quantum efficiency (DQE) of thick, segmented, 2‐D CdWO4 crystals in contact with silicon photodiode arrays. The energy deposited into the 3‐D voxels (1 × 1 × 1 mm3, septa thickness = 0.15 mm, fill factor = 72%) of the detector for each of the 6 and 3.5 MV x‐ray photons in a normally incident pencil beam was calculated using the DOSXYZnrc user code of the EGSnrc Monte Carol system. The isotropically emitted optical photons in each voxel were calculated using the average CdWO4 optical yield and transported to the photodiode array using DETECT2000 optical Monte Carlo code. A 10° beam divergence angle was also simulated. The detector DQE was calculated using the spatial distribution of optical photons. Results: The DQE increases with the crystal height only if the reflectivity of the septa material is high (0.975). For poor reflectivity (0.65 and 0.8), the increase in the DQE of the taller crystals to MV photons is seriously offset (from 42% to less than 20% for 3 cm tall crystals) by the decreased probability of detecting optical photons. Similarly, the increase in DQE due to the lower energy photons is obtained if the high reflectivity of septa material is maintained for the detector. Beam divergence in thick crystals also reduces the DQE. Conclusion: High reflectivity of the septa in thick, segmented scintillation detectors is very important to achieve high DQE.

NuSD: A Geant4 based simulation framework for segmented anti-neutrino detectors

The penumbral imaging technique has proven to be ideally suited for neutron imaging. The French CEA has successfully installed a neutron imaging system at the LLE (Rochester-New York) in June 2000. Images of the 14MeV fusion neutrons produced in the target have been recorded in the range 1012 to 1014 with a two-point resolution of 45 micrometers. The detector used was a 15cm diameter circular array composed of plastic scintillator elements. For several of the CEA experiments, bubble detectors developed for General Atomics simultaneously recorded neutron images. The SIRINC (Simulation and Reconstruction Imaging Neutron Code) code has been used to unfold neutron images obtained both with the segmented scintillator detector and with the bubble detector. We first describe the experimental setup and detector designs, then compare the sensitivity, quantity of information, and signal to noise ratio for those two detectors. Then raw and unfolded images are presented. The spatial resolution obtained for the unfolded images are estimated and compared for the two detectors types.© (2001) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Arrays of thick segmented crystalline scintillators are useful x-ray converters for image-guided radiation therapy using electronic portal imaging (EPI) and megavoltage cone-beam computed tomography (MV-CBCT). Ionizing-radiation-only simulations previously showed relatively low modulation transfer function (MTF) in parallel-element arrays because of beam divergence. Hence, a focused-element geometry (matchingthebeamdivergence)has been proposed. The "full" (ionizing and optical) MTF performance of such a focused geometry compared to its radiation-only MTF has, however, not been fully investigated. To study the full MTF performance of such arrays in a more realistic situation in which optical characteristics are also included using an in-house detector model that supports light transport, and quantify the errors in MTF estimation when the optical stage is ignored. First, radiation (x-ray and electron) transport was simulated. Then, transport of the generated optical photons was modeled using ScintSim2, an optical Monte Carlo (MC) code developed in MATLAB for simulation of two-dimensional (2D) parallel- and focused-element scintillator arrays. The full-MTF responses of focused- and parallel-element geometries, for a large array of 3 × 3 mm2 CsI:Tl detector elements of 10, 40, and 60 mm thicknesses, were examined. For each configuration, a composite line spread function (LSF) was calculated to obtain the MTF. At the Nyquist frequency, for 10 mm-thick central elements and 60 mm-thick peripheral parallel elements, full-MTF exhibited a drop of up to 15 and 79 times, respectively, compared with radiation-only MTF. This was found to be partly attributable to the angular distribution of the light emerging from the detector-element exit face and the dependence on its aspect ratio, since the light exiting thicker scintillators exhibited a more forward-directed distribution. Focused elements provided an increase of up to nine times in peripheral-area full MTF values. Full MTF was up to 79 times lower than radiation-only MTF. Focused arrays preserved full MTF by up to nine times compared to parallel elements. The differences in the results obtained with and without inclusion of optical photons emphasize the need to include light transport when optimizing thick segmented scintillation detectors. Besides their application in detector optimization for radiotherapy megavoltage photon imaging, these findings can also be useful for other segmented-scintillator-based imaging systems, for example, in nuclear medicine, or in 2D detection systems for quality assurance of MR-linacs.

We are developing a novel high-brightness atomic beam, comprised of a two-body exotic atom called muonium (M = μ + + e -), for next-generation atomic physics and gravitational interaction measurements. This M source originates from a thin sheet of superfluid helium (SFHe), hence diagnostics and later measurements require a detection system which is operational in a dilution cryostat at temperatures below 1 K. In this paper, we describe the operation and characterization of silicon photomultipliers (SiPMs) at ultra-low temperatures in SFHe targets. We show the temperature dependence of the signal shape, breakdown voltage, and single photon detection efficiency, concluding that single photon detection with SiPMs below 0.85 K is feasible. Furthermore, we show the development of segmented scintillation detectors, where 16 channels at 1.7 K and one channel at 170 mK were commissioned using a muon beam.

Reconstruction of fast neutron direction in segmented organic detectors using deep learning

Electronic portal imaging devices (EPIDs) based on indirect detection, active matrix flat panel imagers (AMFPIs) have become the technology of choice for geometric verification of patient localization and dose delivery in external beam radiotherapy. However, current AMFPI EPIDs, which are based on powdered-phosphor screens, make use of only approximately 2% of the incident radiation, thus severely limiting their imaging performance as quantified by the detective quantum efficiency (DQE) (approximately 1%, compared to approximately 75% for kilovoltage AMFPIs). With the rapidly increasing adoption of image-guided techniques in virtually every aspect of radiotherapy, there exist strong incentives to develop high-DQE megavoltage x-ray imagers, capable of providing soft-tissue contrast at very low doses in megavoltage tomographic and, potentially, projection imaging. In this work we present a systematic theoretical and preliminary empirical evaluation of a promising, high-quantum-efficiency, megavoltage x-ray detector design based on a two-dimensional matrix of thick, optically isolated, crystalline scintillator elements. The detector is coupled with an indirect detection-based active matrix array, with the center-to-center spacing of the crystalline elements chosen to match the pitch of the underlying array pixels. Such a design enables the utilization of a significantly larger fraction of the incident radiation (up to 80% for a 6 MV beam), through increases in the thickness of the crystalline elements, without loss of spatial resolution due to the spread of optical photons. Radiation damage studies were performed on test samples of two candidate scintillator materials, CsI(Tl) and BGO, under conditions relevant to radiotherapy imaging. A detailed Monte Carlo-based study was performed in order to examine the signal, spatial spreading, and noise properties of the absorbed energy for several segmented detector configurations. Parameters studied included scintillator material, septal wall material, detector thickness, and the thickness of the septal walls. The results of the Monte Carlo simulations were used to estimate the upper limits of the modulation transfer function, noise power spectrum and the DQE for a select number of configurations. An exploratory, small-area prototype segmented detector was fabricated by infusing crystalline CsI(Tl) in a 2 mm thick tungsten matrix, and the signal response was measured under radiotherapy imaging conditions. Results from the radiation damage studies showed that both CsI(Tl) and BGO exhibited less than approximately 15% reduction in light output after 2500 cGy equivalent dose. The prototype CsI(Tl) segmented detector exhibited high uniformity, but a lower-than-expected magnitude of signal response. Finally, results from Monte Carlo studies strongly indicate that high scintillator-fill-factor configurations, incorporating high-density scintillator and septal wall materials, could achieve up to 50 times higher DQE compared to current AMFPI EPIDs.

\(\beta\)-decay properties of very neutron-rich nuclei, such as the half-life and the \(\beta\)-delayed neutron emission probabilities, play an essential role in the astrophysical rapid neutron capture process (r-process), where elements heavier than iron may be synthesized. Investigating those crucial properties has been one of the main objectives of the experimental programs at the RIKEN RI Beam Factory (RIBF). Recently, the development of a fast-timing detector system comprising a highly segmented plastic scintillation detector GARi (Gas-cell Active detector for Radioisotope decay), a neutron time-of-flight detector array, and a LaBr\textsubscript{3} detector array is being conducted for the measurement of \(\beta\)-delayed neutron emission and other related \(\beta\)-decay properties of neutron-rich nuclei at the F11 decay station of RIBF. The GARi detector has been constructed from a fast, segmented plastic scintillator coupled with nine multi-anode photomultiplier tubes (PMTs), resulting in enhanced position sensitivity. Therefore, this detector can be employed as an implantation detector and can also serve as a trigger signal in neutron time-of-flight experiments. This work details the development of the GARi detector and the results tested with the radioactive sources.

Estimate of the chemical composition of cosmic rays from a multifractal moments analysis of the lateral particle distributions in the core of high-energy EAS

The T2K neutrino oscillation experiment established the $\nu_{\mu}\rightarrow \nu_{e}$ appearance with 10% of the original beam request of 7.8$\times$10$^{21}$ 30 GeV protons on target (POT). In view of the J-PARC program of upgrades of the beam intensity, the T2K-II proposal extends the run up to 20$\times$10$^{21}$ POT to establish the charge-parity (CP) violation at 3$\sigma$ level for a significant fraction of the possible $\delta_{CP}$ values. To achieve this goal, it is important to accomplish near detector upgrades to reduce the overall statistical and systematic uncertainties from approximately 6\% to the level of 4%. The T2K near detector ND280 upgrade project was launched in January 2017, and the proposal was submitted to the CERN SPSC and to the JPARC PAC in January 2018. ND280 Upgrade implements two horizontal high-angle time projection chambers (HA-TPCs), a highly segmented scintillator detector Super-FGD, and time-of-flight (TOF) detectors to the upstream of the current near detector. HA-TPCs are built to achieve the wide angle acceptance with the light field cages and resistive Micromegas detectors for the charge readout. SuperFGD consists of $1\times1\times1$ cm$^3$ plastic scintillator cubes readout by three WLS fibers directed to multi-pixel photon counters (MPPCs), providing detailed tracking and particle identification (PID) information. TOF complements the HA-TPCs and Super-FGD PID by determining track direction and time information. Combination of these detectors is planned to be installed to obtain a 4$\pi$ acceptance for neutrino charged current interactions with improved tracking performance for low energy charged particles.

16-bit microcontroller is first herald of TRON

The Palo Verde reactor neutrino oscillation experiment

Index to volume 7, number 1–10, pages 1–504 (1983)

Nowadays, the current threat of international terrorism is set to a severe level, demanding worldwide enhanced security. Radioactive materials that could be fashioned into a radiation dispersal device typically emit gamma rays, while fissile materials such as uranium and plutonium emit both neutrons and gamma rays via spontaneous or induced fission. Therefore, the detection and identification of hazardous materials has become increasingly important. We present the results of GEANT4 Monte Carlo simulation of an active neutron interrogation system based on highly segmented neutron/gamma-ray detector and pulsed neutron generator. This system is capable of detecting and imaging radioactive and special nuclear materials, explosives and drugs. The segmented scintillation detector works as a scatter camera, allowing selection of a gamma ray events that undergo multiple interaction in detector blocks for radioactive source localization. The detector consist of blocks made of plastic scintillator which provide scattering and blocks of CsI, used as an absorber, used as an absorber, which has to be efficient to detect the characteristic gamma radiation for the identification. Because of this imaging capability background events can be significantly rejected, decreasing the number of events required for high confidence detection and thereby greatly improving its sensitivity. A scatter imager for the detection of shielded radioactive materials has been conceptualized, simulated, and refined to maximize sensitivity while minimizing cost.