Position Reconstruction Method Research Articles

FPGA-based position reconstruction method for neutron beam flux spatial distribution measurement in BNCT

FPGA-based position reconstruction method for neutron beam flux spatial distribution measurement in BNCT

Simulation study of the light collection efficiency and the dependency on position resolution in plastic scintillator-based muography detectors

Cosmic-ray muon imaging (muography) has been applied in various fields in recent years, in which plastic scintillators are one of the frequently selected detectors internationally. Therefore, a triangular scintillator strip based muography detection system has been proposed in the development of the μ Scattering and Transmission imaging faCility (μSTC). Before the mass production of detector units, this work studied the impacts of multiple factors on the light collection efficiency (LCE) and the position resolution (σ) of plastic scintillators. These factors include configurations of wavelength shifting (WLS) fibers, fiber grooves on scintillators, coupling optical glues and silicon photomultiplier (SiPM) readout mode. According to the simulated results, an empirical formula was proposed to quantitatively describe the relation between the LCE and σ, which has seldom been studied before. In this formula, σ reduces as a power-law function of the LCE. The SiPM readout mode (single-end or double-end output) and fiber groove treatments show no significant influence on the σ-LCE relation. LCE variations due to different factors lead to a difference in σ of less than 0.2 mm in the whole range of LCE. Accordingly, these factors are nearly equivalent in the improvement of detector position resolution. In comparison, the muon hit position reconstruction method nearly halves the σ after using angular and gap corrections. Thus, a better reconstruction method shows greater importance than the efforts made to increase LCEs. The simulation study in this work will provide good references for the construction of plastic scintillators of the μSTC platform in the near future.

An improved position reconstruction method for radioactive particle tracking

This work introduces a novel reconstruction method exploiting the inverse of Finite Element Method (FEM) to reconstruct positions from ray tracing experimental measurement such as those obtained by radioactive particle tracking. FEM based Position Reconstruction (FEM-PR) relies on shape function evaluation within simplex elements (i.a tetrahedron) for position reconstruction using a mean-square problem, which has proven to be robust, accurate, and fast. Tracer positions are reconstructed under the condition that least-squares compatibility is maintained between experimental counts and interpolated values within inverse elements. This approach is implemented in a module within the open-source software, Lethe-RPT, enabling user to carry out radioactive particle tracking (RPT) experiments from calibration to tracer position reconstruction. The test benchmark and experimental setup are described. For the same test cases, the reconstruction error is investigated using an increasing number of inverse elements and Monte Carlo (MC) iterations. The accuracy and robustness of FEM-PR concerning the inevitable measurement errors due to calibration, measurement systems, and the quantized nature of γ-rays is demonstrated. This approach provides a new view for immediate and precise position reconstruction. FEM-PR reconstructs the tracer position with an accuracy of 0.08mm. Approximately 3.37ms is required to reconstruct one position on a desktop computer, which is less than the sampling time for experimental data collection.

GIPPE-RPT: Geant4 interface for particle physics experiments applied to Radioactive Particle Tracking

Radioactive Particle Tracking (RPT) is a non-invasive experimental technique that tracks the motion of a gamma-emitting radionuclide. Despite the RPT’s high versatility, the lack of dedicated software represents a significant barrier to its wider adoption. This article introduces a new software, GIPPE-RPT, designed to bring the technique closer to a wider group of users. GIPPE-RPT is a user-friendly software that enables the creation, execution, and post-processing of high-energy physics simulations in Geant4 employing a graphical user interface. Under the platform, the user can specify all critical RPT parameters, such as reactor geometry, materials, detector number and type, and tracer type and activity. Multiple configurations can be designed and compared for optimization. GIPPE-RPT also integrates the OpenFOAM solver, which enables the setup and execution of Computational Fluid Dynamics simulations. The simulation results can be imported in Geant4 allowing an accurate description of density profiles inside the reactor. The main software modules, functions, and workflow are demonstrated using a virtual NETL SSCP-I fluidized bed reactor as a test case. The main steps in setting up an RPT experiment in GIPPE-RPT, including domain design, tracer selection, detector placement, and calibration strategy are presented in detail. The performance of six position reconstruction methods implemented in GIPPE-RPT is compared for several RPT scenarios highlighting the strengths and weaknesses of each method. Finally, the benefits of capturing heterogeneous density profiles using simulations are demonstrated by comparing reconstruction errors for test cases with heterogeneous and homogeneous media.

Statistical position reconstruction for RPC-based thermal neutron detectors

Multilayer position-sensitive 10B-RPC thermal neutron detectors offer an attractive combination of sub-millimeter spatial resolution and high (>50%) detection efficiency. Here we describe a new position reconstruction method based on a statistical approach. Using experimental data, we compare the performance of this method with that of the centroid reconstruction. Both methods result in a similar image linearity/uniformity and spatial resolution. However, the statistical method allows to improve the image quality at the detector periphery, offers more flexible event filtering and allows to develop automatic quality monitoring procedures for early detection of situations when a change in the detector operation conditions starts to affect reconstruction quality.

High spatial resolution monolithic pixel detector in SOI technology

This paper presents test-beam results of monolithic pixel detector prototypes fabricated in 200 nm Silicon-On-Insulator (SOI) CMOS technology studied in the context of high spatial resolution performance. The tested detectors were fabricated on a 500 μm thick high-resistivity Floating Zone type n (FZ-n) wafer and on a 300 μm Double SOI Czochralski type p (DSOI Cz-p) wafer. The pixel size is 30 μm×30 μm and two different front-end electronics architectures were tested, a source follower and a charge-sensitive preamplifier. The test-beam data analyses were focused mainly on determination of the spatial resolution and the hit detection efficiency. In this work different cluster formation and position reconstruction methods are studied. In particular, a generalization of the standard η-correction adapted for arbitrary cluster sizes, is introduced. The obtained results give in the best case a spatial resolution of about 1.5 μm for the FZ-n wafer and about 3.0 μm for the DSOI Cz-p wafer, both detectors showing detection efficiency above 99.5%.

Optical Properties of Continuous and Pixelated Scintillation Crystals

The optical photon distribution produced inside continuous and pixelated scintillation crystals by the absorption of a γ-ray have been studied with the photon transport program DETECT 2000. With this program the charge signals recorded by a multi-wired anode system, like the Position Sensitive PhotoMultiplier Tube (PSPMT) of a γ-Camera, are simulated. Based on the analytical parametrization which is fitted to experimental data, a new position reconstruction method for PSPMTs is proposed in this work. Planar images have been reconstructed with the new method and compared to the traditional charge center of gravity technique. Data are obtained from a small field, high resolution γ-Camera system with a multi- wired crossed anode using the R2486 (HAMAMATSU) PSPMT. Systematic studies for continuous and pixelated inorganic scintillation crystals of CsI(Tl) have been performed for different phantom geometries using small capillaries of 99mTc. The developed method seems to drastically improve the resolution of the reconstructed planar information, even when homogeneous crystals are used.

Performance studies of resistive-strip bulk micromegas detectors in view of the ATLAS New Small Wheel upgrade

Abstract The ATLAS collaboration at the Large Hadron Collider at CERN has endorsed the resistive-strip micromegas technology for the high luminosity upgrade of the first muon station in the high-rapidity region, the so called “New Small Wheel” project. It requires detectors with a spatial resolution of ∼ 100 μ m , fully efficient up to a particle rate of ∼ 20 kHz/cm 2 . In order to demonstrate that the resistive-strip micromegas technology fulfils these requirements, small resistive bulk micromegas have been studied with radioactive sources and with high energy beams. The micromegas chambers were operated with an Ar+7%CO 2 gas mixture and read out using the APV25 chip. Results on the detection efficiency and the position resolution are presented for track impact angles from 0° to 40°. A position reconstruction method has been developed for inclined tracks, called the “micro-TPC method”. A description of the method along with performance studies is presented. In addition, the impact of the unavoidable presence of pillars and the relative alignment of readout and resistive strips on the micromegas performance has been quantified. In view of the fact that the micromegas detectors will also contribute to the trigger in ATLAS their time response has been studied.

Position reconstruction in LUX

The (x, y) position reconstruction method used in the analysis of the complete exposure of the Large Underground Xenon (LUX) experiment is presented. The algorithm is based on a statistical test that makes use of an iterative method to recover the photomultiplier tube (PMT) light response directly from the calibration data. The light response functions make use of a two dimensional functional form to account for the photons reflected on the inner walls of the detector. To increase the resolution for small pulses, a photon counting technique was employed to describe the response of the PMTs. The reconstruction was assessed with calibration data including 83mKr (releasing a total energy of 41.5 keV) and 3H (β− with Q = 18.6 keV) decays, and a deuterium-deuterium (D-D) neutron beam (2.45 MeV) . Within the detector's fiducial volume, the reconstruction has achieved an (x, y) position uncertainty of σ = 0.82 cm and σ = 0.17 cm for events of only 200 and 4,000 detected electroluminescence photons respectively. Such signals are associated with electron recoils of energies ∼0.25 keV and ∼10 keV, respectively. The reconstructed position of the smallest events with a single electron emitted from the liquid surface (22 detected photons) has a horizontal (x, y) uncertainty of 2.13 cm.

The spatial resolution of the silicon tracker of the Alpha Magnetic Spectrometer

The Alpha Magnetic Spectrometer (AMS) is a high energy physics experiment operating aboard the International Space Station (ISS) since May 2011. So far more than 100 billion of charged cosmic ray events have been collected by AMS. The AMS silicon tracker, together with the magnet, measures the rigidity (momentum/charge) of cosmic rays in the range from ∼0.5 GV to several TV. To accurately determine the trajectory of charged particles, a novel tracker position reconstruction method has been developed. In the paper, the details of the method and the obtained tracker spatial resolution for nuclei with charge 2≤Z≤26 are presented.

Characterization of LaBr3:Ce and CeBr3 calorimeter modules for 3D imaging in gamma-ray astronomy

For the purpose of future space instrumentation for γ-ray astronomy, we developed a small prototype of a Compton telescope and studied novel detector modules aimed for Compton imaging. We assembled and tested 2 modules, one with a cerium-doped lanthanum(III) bromide (LaBr3:Ce) crystal and the other with cerium(III) bromide (CeBr3). Both crystals measure 5×5cm2 in area and are 1cm thick. They are coupled to and read out by 64-channel multi-anode PMTs. Our goals are to obtain the best possible energy resolution and position resolution in 3D on the first impact of an incident γ-ray within the detector. Both information are vital for successful reconstruction of a Compton image with the telescope prototype. We developed a test bench to experimentally study both modules and have utilized a customized readout electronics and data acquisition system. Furthermore, we have written a detailed Geant4 simulation of the experiment, and utilize simulated data to train an Artificial Neural Network (ANN) algorithm to create a simplified 3D impact position reconstruction method. We give experimental test results obtained by both modules and present detailed parametrization and results from the Geant4 simulation and from the ANN. We compare and discuss the performance of the modules and conclude by giving a brief overview of the future prospects for using such modules in γ-ray astronomy.

ANTS2 package: simulation and experimental data processing for Anger camera type detectors

ANTS2 is a simulation and data processing package developed for position sensitive detectors with Anger camera type readout. The simulation module of ANTS2 is based on ROOT package from CERN, which is used to store the detector geometry and to perform 3D navigation. The module is capable of simulating particle sources, performing particle tracking, generating photons of primary and secondary scintillation, tracing optical photons and generating photosensor signals. The reconstruction module features several position reconstruction methods based on the statistical reconstruction algorithms (including GPU-based implementations), artificial neural networks and k-NN searches. The module can process simulated as well as imported experimental data containing photosensor signals. A custom library for B-spline parameterization of spatial response of photosensors is implemented which can be used to calculate and parameterize the spatial response of a detector. The package includes a graphical user interface with an extensive set of configuration, visualization and analysis tools. ANTS2 is being developed with the focus on the iterative (adaptive) reconstruction of the detector response using flood field irradiation data. The package is implemented in C++ programming language and it is a multiplatform, open source project.

129 - Front-end electronics and hit position reconstruction methods for the J-PET scanner

129 - Front-end electronics and hit position reconstruction methods for the J-PET scanner

Spatial resolution of a [formula omitted] neutron imaging detector

We present a detailed study of the spatial resolution of our time-resolved neutron imaging detector utilizing a new neutron position reconstruction method that improves both spatial resolution and event reconstruction efficiency. Our prototype detector system, employing a micro-pattern gaseous detector known as the micro-pixel chamber (μPIC) coupled with a field-programmable-gate-array-based data acquisition system, combines 100μm-level spatial and sub-μs time resolutions with excellent gamma rejection and high data rates, making it well suited for applications in neutron radiography at high-intensity, pulsed neutron sources. From data taken at the Materials and Life Science Experimental Facility within the Japan Proton Accelerator Research Complex (J-PARC), the spatial resolution was found to be approximately Gaussian with a sigma of 103.48±0.77μm (after correcting for beam divergence). This is a significant improvement over that achievable with our previous reconstruction method (334±13μm), and compares well with conventional neutron imaging detectors and with other high-rate detectors currently under development. Further, a detector simulation indicates that a spatial resolution of less than 60μm may be possible with optimization of the gas characteristics and μPIC structure. We also present an example of imaging combined with neutron resonance absorption spectroscopy.

Proximity Electrode Signal Readout of High-Purity Ge Detectors

Proximity electrode signal readout of semiconductor- based radiation detectors is accomplished by measuring the charge induced on electrodes positioned close, but not electrically connected, to the detector material. This technology can be applied to high-purity Ge (HPGe) to create a position sensitive gamma-ray detector. The proximity readout technique offers the advantages of simplified detector fabrication, expanded electrode geometry options, and greatly improved position resolution through simple signal interpolation. We have produced small, HPGe prototype detectors that utilize strip proximity electrodes for gamma-ray interaction energy and position measurement. With these detectors we have collected event data sets under a variety of detector and source conditions. With this data we have explored energy and position reconstruction methods and have demonstrated sub-strip-pitch position determination. In this paper, we summarize the results of our investigation.

Monte Carlo simulation studies on scintillation detectors and image reconstruction of brain-phantom tumors in TOFPET

This study presents Monte Carlo Simulation (MCS) results of detection efficiencies, spatial resolutions and resolving powers of a time-of-flight (TOF) PET detector systems. Cerium activated Lutetium Oxyorthosilicate (Lu2SiO5: Ce in short LSO), Barium Fluoride (BaF2) and BriLanCe 380 (Cerium doped Lanthanum tri-Bromide, in short LaBr3) scintillation crystals are studied in view of their good time and energy resolutions and shorter decay times. The results of MCS based on GEANT show that spatial resolution, detection efficiency and resolving power of LSO are better than those of BaF2 and LaBr3, although it possesses inferior time and energy resolutions. Instead of the conventional position reconstruction method, newly established image reconstruction (talked about in the previous work) method is applied to produce high-tech images. Validation is a momentous step to ensure that this imaging method fulfills all purposes of motivation discussed by reconstructing images of two tumors in a brain phantom.

Preliminary results on position reconstruction for ZEPLIN III

ZEPLIN III is a two-phase xenon detector for direct dark matter search that will look for rare nuclear recoils from elastic scattering of Weakly Interacting Massive Particles off xenon atoms. ZEPLIN III measures both the scintillation and ionisation signals produced in the liquid by the interacting particle. The prompt scintillation is detected by an array of 31 photomultipliers (PM) immersed in the liquid, and a strong electric field extracts the ionisation electrons to the vapour phase. Electroluminescence photons are produced in the gas and detected by the same PM array. In this paper we describe position reconstruction methods that use both these signals to achieve a position accuracy of a few millimetres in the horizontal plane and sub-millimetre in the vertical coordinate.

On image reconstruction with the two-dimensional interpolating resistive readout structure of the Virtual-Pixel detector

The two-dimensional interpolating readout concept of the Virtual-Pixel detector (ViP detector) goes along with an enormous reduction of electronic channels compared to pure pixel devices. However, the special concept of the readout structure demands for adequate position reconstruction methods. Theoretical considerations reflecting the choice and the combination of linear algorithms with emphasis on correct position reconstruction and optimised spatial resolution are presented. A subsequent two-dimensional coordinate transformation further improves the image response of the system. Measured images show how far the theoretical predictions of the simulations can be verified and to what extent they can be used to improve the position reconstruction.