Detector Geometry Research Articles

Laser-induced fluorescence spectroscopic investigation of Echium amoenum decoction

Herbs containing medicinal ingredients with nutritional value have recently gained attention as an alternative to synthetic drugs. Aside from their pharmaceutical worthiness, a variety of naturally occurring chromophores with specific optical properties have made them valuable sources of natural pigments for many biophotonic applications. Echium Amoenum (EA) is one of the colorful flowers that has been used in traditional medicine for a long time. To our knowledge, although several studies have been carried out on the characterization of EA ingredients and their chemical activities, information on EA fluorescence is still lacking. Here, laser induced fluorescence (LIF) features of the decoction of EA petals were evaluated and found to be highly dependent on the excitation wavelength, EA concentration, and detection geometry. The abundance of pigments, the boundaries of their absorption/emission spectral regions, and the corresponding energy transfer ascertain the contribution of certain chromophores to the cumulative fluorescence activity. Upon deconvolution of the LIF spectra, it was revealed that the different emission bands of rosmarinic acid (corresponding to its dissociated forms) and the luminescent activity of luteolin and β-carotene mainly determine the quantum distribution of the fluorescence of EA. Angular measurement of LIF in a symmetric cylindrical arrangement revealed the presence of the inner filters mainly due to the reabsorption of LIF photons by anthocyanins (flavone, pelargonidin, delphinidin and cyanidin) and carotenoids. We hope that the obtained results will be useful in various fields of photochemistry and biophotonics.

Performance measurements of Total Body PET scanner simulations using the Geant4 toolkit

Total-Body PET (TB PET) is a novel imaging modality that can image the whole body in a single scan. It has increased sensitivity, improved spatial resolution, reduced imaging times compared to conventional clinical PET scanners, and has the potential to detect smaller lesions and multiorgan diseases. Commercially available TB PET scanners include the Siemens Biograph Vision Quadra [1] and the United Imaging uEXPLORER [2]. This study uses the Geant4 toolkit [3] to create a simulation model of two different TB PET detector geometries; Siemens Biograph Vision Quadra and uEXPLORER. Analysis of simulated data and performance measurements were carried out in Python. The study follows the NEMA NU-2 2018 standard [4]. The simulation was used to explore the effect of different scintillator crystals and evaluates the count rate performance and the sensitivity of the scanner. The simulated data was compared to published experimental data from Siemens and Explorer. Good agreement between the count rates of simulated and experimental data was observed for both geometries. The simulated Siemens Quadra measured a system sensitivity value of 178.6 cps/kBq showing a 2% difference compared to the experimental data of 175.3 cps/kBq for LSO crystals. Axial sensitivity profiles plotted also match well. The comparison of different scintillators showed that BGO performs best as it has the highest peak NECR, thus good signal-to-noise ratio. LSO and LYSO also perform well and their physical properties are similar. NaI and CsI exhibit the worst performance; with low true count rates and the random count rates increased almost linearly with activity concentration. Our simulations compared well against experimental data, allowing us to test further scintillator materials and radioisotopes. After implementing image reconstruction and relevant corrections, this simulation can be used for validation of various research ideas in the future. Please click on the 'PDF' for the full abstract!

Spatial resolution studies using point spread function extraction in optically read out Micromegas and GEM detectors

Optically read out gaseous detectors are used in track reconstruction and imaging applications requiring high granularity images. Among resolution-determining factors, the amplification stage plays a crucial role and optimizations of detector geometry are pursued to maximize spatial resolution. To compare Micro Pattern Gaseous Detector (MPGD) technologies, focused low-energy X-ray beams at the SOLEIL synchrotron facility were used to record and extract point spread function widths with MICRO-Mesh Gaseous Structure (icromegas) and Gas Electron Multiplier (GEM) detectors. Point spread function width of ≈108µm for Micromegas and ≈127µm for GEM foils were extracted. The scanning of the beam with different intensities, energies and across the detector active region can be used to quantify resolution-limiting factors and improve imaging detectors using MPGD amplification stages.

Simulation of a capillary tube, fibre dual-readout calorimeter in DD4hep

Over the past years the dual-readout method for calorimetry, which exploits complementary information from Scintillation and Cherenkov channels, has emerged as candidate to fulfil the requirements for precision physics at future circular lepton colliders. While the dual-readout approach has been tested experimentally quite extensively, this type of calorimeter has never been used in an experiment at a collider. In recent years dedicated studies in simulation have investigated various detector geometries based on a fibre dual-readout calorimeter. One variation of the geometry, relying on capillary tubes, promises easy assembly with excellent geometrical accuracy at a moderate cost. In these proceedings, we present the status and latest results from a full 4π detector geometry simulation in DD4hep. The simulation is used to estimate the performance of a dual-readout calorimeter for single electromagnetic and hadronic particles. The results for the dual-readout technique show an improvement in energy resolution for both electromagnetic and hadronic showers, with respect to single channel measurements.

Validation of a Virtual Ray Tracing Instrument for Dimensional X-Ray CT Measurements

A new Forward Ray Tracing Instrument (FRTI) for simulating X-ray CT scanners is presented. The FRTI enables the modelling of various detector geometries to optimise instrument designs. The FRTI is demonstrated by comparing experimentally measured sphere centre-to-centre distances from two material measures with digital clones. The measured length deviations were smaller than the reconstructed grid spacing for both the experimental and simulated acquisitions. As expected the experimentally measured length deviations were larger than the simulated measurements. The results demonstrate the FRII’s capability of simulating an X-ray CT scanner and performing length measurements.

Interplay of Circularly Polarized Light with Molecular and Structural Chirality: Chiral Lanthanide Complexes and Cellulose Nanocrystals

AbstractThe interaction of circularly polarized (CP) light with chiral matter at different scales opens several possibilities of light manipulation in photonic and electronic devices. Here it is shown that in a multilayer architecture, it is possible to take advantage of the polarization‐selective reflection of the nematic arrangement of cellulose nanocrystals and the strong intrinsic CP luminescence (CPL) of the various bands of chiral Eu complexes. In this way, both the intrinsic CPL and total emission of the complex are modified depending on the enantiomer applied and on the detection geometry. This concept may apply for polarization control in electronic and photonic devices and polarized optical cavities.

New CAD modeling approach in Geant4 with half-space CSG

Geant4 offers constructive solid geometry (CSG) for modeling detector geometries, but representing intricate computer-aided design (CAD) structures can be cumbersome. This article presents a novel approach that overcomes this limitation. A new CSG solid type called “half-space solid” enables the equivalent representation of complex CAD solids within Geant4. An automatic program utilizes optimized decomposition algorithms to convert CAD solids into half-space solids. The geometry description markup language (GDML) has been extended to accommodate the half-space solid type alongside the development of interfaces for exporting converted geometries and their subsequent import into Geant4. These advancements establish a fully automated workflow for converting CAD geometries into CSG-based representations suitable for Geant4 simulations. The reliability of the half-space solid-based modeling approach has been verified through comparisons with established Geant4 solids for both simple shapes and a complex fusion reactor model. The excellent agreement obtained from these comparisons demonstrates the efficiency of this new approach.

β + surgical radio-guidance using a small Compton-angles collimation probe

The fields of radio-guided surgery and interventional nuclear medicine benefit from a growing array of technologies that aid novel healthcare interventions. Among them, surgery probes able to efficiently detect β + emitters are essential to localize tumors previously detected in PET images. Different methods have been proposed for 18F radio-guidance within the body such as detection of 511 keV annihilation photons using electronically or mechanically collimated probes. The main limitations to the widespread use of these techniques are the lack of precise directional capabilities and inadequate sensitivity. We first used the Monte Carlo simulation platform GATE to determine the optimal signal to noise ratio that can be achieved with an ideal probe. Then, we focused on investigating a small Compton-angles collimation prototype probe followed by the construction of an initial proof of concept demonstrator. The performance of the small Compton-angles collimation probe was compared with a commercial probe based on mechanical collimation in terms of sensitivity and directionality. Monte Carlo simulations showed that in case of an ideal probe, with a tumor of 1 cm diameter positioned 5 mm under the skin and with a SUV of 2, the measured signal to background ratio would be of the order of 25%. The small Compton-angles collimated probe prototype showed significantly improved directionality compared to the commercial probe with mechanical collimation, despite having a sensitivity lower than the commercial probe. Monte Carlo simulations provide insights into the substantial impact of the background on the measured signal. Furthermore, the application of small Compton-angles collimation yields promising outcomes, particularly in terms of improving the directionality, with the objective of enhancing the detection of tumors. In addition, the studied prototype probe sensitivity can possibly be improved by upgrading the detector crystal material and geometry.

Geometry import into virtual reality visualization engine for HEP experiments at BM@N

Modern visualization and multimedia platforms, such as Unity, provide immersive interaction for HEP experiment data analysis. In this work, we present the method for importing the detector geometry, solids hierarchy, and materials from GDML format directly to Unity. This method is based on parsing files in GDML format and generating the geometry using mesh generation algorithms and Constructive Solid Geometry methods. The provided method is applied to the BM@N experiment at NICA accelerator complex in Joint Institute of Nuclear Research and can be used in virtual reality and augmented reality applications for data analysis and outreach events in high energy physics experiments.

Simultaneous mapping of cathodoluminescence spectra and backscatter diffraction patterns in a scanning electron microscope

Electron backscatter diffraction and cathodoluminescence are complementary scanning electron microscopy modes widely used in the characterisation of semiconductor films, respectively revealing the strain state of a crystalline material and the effect of this strain on the light emission from the sample. Conflicting beam, sample and detector geometries have meant it is not generally possible to acquire the two signals together during the same scan. Here, we present a method of achieving this simultaneous acquisition, by collecting the light emission through a transparent sample substrate. We apply this combination of techniques to investigate the strain field and resultant emission wavelength variation in a deep-ultraviolet micro-LED. For such compatible samples, this approach has the benefits of avoiding image alignment issues and minimising beam damage effects.

A Dataset for Kinship Estimation from Image of Hand Using Machine Learning

Kinship (Familial relationships) detection is crucial in many fields and has applications in biometric security, adoption, forensic investigations, and more. It is also essential during wars and natural disasters like earthquakes since it may aid in reunion, missing person searches, establishing emergency contacts, and providing psychological support. The most common method of determining kinship is DNA analysis which is highly accurate. Another approach, which is noninvasive, uses facial photos with computer vision and machine learning algorithms for kinship estimation. Each part of the Human -body has its own embedded information that can be extracted and adopted for identification, verification, or classification of that person. Kinship recognition is based on finding traits that are shared by every family. We investigate the use of hand geometry for kinship detection, which is a new approach. Because of the available hand image Datasets do not contain kinship ground truth; therefore, we created our own dataset. This paper describes the tools, methodology, and details of the collected MKH, which stands for the Mosul Kinship Hand, images dataset. The images of MKH dataset were collected using a mobile phone camera with a suitable setup and consisted of 648 images for 81 individuals from 14 families (8 hand situations per person). This paper also presents the use of this dataset in kinship prediction using machine learning. Google MdiaPipe was used for hand detection, segmentation, and geometrical key points finding. Handcraft feature extraction was used to extract 43 distinctive geometrical features from each image. A neural network classifier was designed and trained to predict kinship, yielding about 93% prediction accuracy. The results of this novel approach demonstrated that the hand possesses biometric characteristics that may be used to establish kinship, and that the suggested method is a promising way as a kinship indicator.

High‐performance photonic crystal fibre biosensor for identifying Jurkat cells by refractive index analysis

AbstractJurkat cells are immortalised lines of human T lymphocyte cells widely used in research to study leukaemia, signalling of T cells, and immune responses. These cells can be used as models to define the mechanisms of leukaemia and to develop mechanism‐based therapies. Jurkat cells can be detected with remarkable accuracy using the recently created Photonic Crystal Fibre (PCF). The suggested design has a hybrid arrangement on its clad surface and a rectangular core. The recently released PCF analyser displays a maximum Relative Sensitivity are 95.81% for Jurkat (type I) and 94.93% for Jurkat (type II), respectively. The Effective Material Loss of 0.0070 cm−1, 0.0080 cm−1, and the Confinement Loss of 9.11 × 10−9 dB/m, 9.15 × 10−8 dB/m were also examined for the previously described units. Jurkat cells represent a model of leukaemia that is very malignant and proliferative, representative of aggressive T‐cell acute lymphoblastic leukaemia with the ability to progress rapidly and hence poor prognosis for patients. The benefit of applying a suggested PCF sensor to Jurkat cell detection lies in the high sensitivity to refractive index changes, allowing label‐free and real‐time monitoring of cell interaction. This PCF sensor can offer high light‐matter interaction, custom geometry, and biocompatibility for specific and reliable detection of deadly Jurkat cells in biomedical research and clinical diagnostics.

A Steering-Vector-Based Matrix Information Geometry Method for Space–Time Adaptive Detection in Heterogeneous Environments

Plagued by heterogeneous clutter, it is a serious challenge for airborne radars to detect low-altitude, weak targets. To overcome this problem, a novel matrix information geometry detector for airborne multi-channel radar is proposed in this paper. The proposed detector applies the given steering vector and array structure information to the matrix information geometry detection method so that it can be used for space–time adaptive detection. While improving the detection performance, the matrix information geometry detector’s original anti-clutter advantage is enhanced as well. The simulation experiment results indicate that the proposed detector has advantages in several of the properties related to space–time adaptive detection, while its computational complexity does not increase significantly. Moreover, experiment results based on the measured data verify the superior performance of the proposed method. Sea-detecting data-sharing-program data, mountaintop data, and phased-array radar data are employed to verify the performance advantage of the proposed method in heterogeneous clutter and the ability for weak target detection.

Positronium lifetime measurement using a clinical PET system for tumor hypoxia identification

Positronium (Ps) imaging has been recently spotlighted for its potential applications in nuclear medicine. Among them, we expect that the Ps lifetime can be a sensor for tumor hypoxia; hence, we are aiming to achieve Ps lifetime imaging, Quantum PET (Q-PET), based on whole gamma imaging (WGI). A linear correlation was previously shown between the Ps lifetime and the oxygen partial pressure (pO2) in water by using a bench-top detector system. However, nobody has ever measured the Ps lifetimes for pO2 values of 10 mmHg and 40 mmHg, corresponding to hypoxic cancer cells and healthy tissue cells, respectively. Therefore, this study aimed at measuring the Ps lifetime of 22Na solutions each having such tiny differences in the pO2 value. For possible extension toward imaging, we used VRAIN, a clinical brain-dedicated time-of-flight (TOF) PET system. The pO2 values of the 22Na solutions were adjusted to 0, 10, 40, and 160 (air) mmHg by adjusting the inflow of nitrogen gas. Each 22Na solution was placed near the center of the detector geometry and measured. Three different energy windows (EWs) for 1275 keV gamma detection were compared (1100–1500 keV, 900–1500 keV and 700–1500 keV). Due to the increased number of events, the error values (σ: standard deviation) of the calculated Ps lifetimes decreased as the EW widened. The optimized EW was determined to be 700–1500 keV, which showed the lowest error value. The Ps lifetime values gradually became shorter as the pO2 values increased. The Ps lifetime values at 0 mmHg and 160 mmHg were 1.9389 ± 0.0025 ns and 1.9104 ± 0.0024 ns at the EW of 700–1500 keV. The difference between the lifetime values was more than three times the errors (±3σ), and we considered it was a statistically significant difference. The Ps lifetime values of 10 mmHg and 40 mmHg were 1.9360 ± 0.0026 ns and 1.9291 ± 0.0024 ns at the same condition, and the difference could be distinguished with an error value of more than ± 1σ.

NeuSIM4: A comprehensive GEANT4 based neutron simulation code

A new neutron SIMulation program based on the versatile GEANT4 toolkit, neuSIM4, has been developed to describe interactions of neutrons in the NE213 liquid scintillator from 0.1 to 3000 MeV. neuSIM4 is designed to accommodate complicated modern detector geometry setups with multiple scintillator detectors, each of which can be outfitted with more than one photo-multiplier. To address a broad spectrum of neutron energies, two new neutron interaction physics models, KSCIN and NxQMD, have been implemented in GEANT4. For neutrons with energy below 110 MeV, we incorporate a total of eleven neutron induced reaction channels on hydrogen and carbon nuclei, including nine carbon inelastic reaction channels, into KSCIN. Beyond 110 MeV, we implement a neutron induced reaction model, NxQMD, in GEANT4. We use its results as reference to evaluate other neutron-interaction physics models in GEANT4. We find that results from an existing cascade physics model (INCL) in GEANT4 agree very well with the results from NxQMD, and results from both codes agree with new and existing light response data. To connect KSCIN to NxQMD or INCL, we introduce a transition region where the contribution of neuSIM4 linearly decreases with corresponding increased contributions from NxQMD or INCL. To demonstrate the application of the new code, we simulate the light response and performance of a 2 × 2 m2 neutron detector wall array consisting of 25 2m-long scintillation bars. We are able to compare the predicted light response functions to the shape of the experimental response functions and calculate the efficiency of the neutron detector array for neutron energies up to 200 MeV. These simulation results will be pivotal for understanding the performance of modern neutron arrays with intricate geometries, especially in the measurements of neutron energy spectra in heavy-ion reactions.

Toward a multi-layer micro-structured detector for high-energy electron radiotherapy.

The use of electron beams has been rekindled by the advent of ultra-high-dose rate radiotherapy (FLASH) and very high energy electrons (VHEE). The need for development of novel technology for beam monitoring and dosimetry of such beams is of paramount importance prior to their clinical translation. In this work we explore the potential of a multi-layer nanoporous aerogel High-Energy-Current (HEC) detector as a dosimeter for electron beam. The detector does not suffer from radiation damage or signal saturation, making it suitable for very-high-dose-rate applications. Standard dose rates and energies are used to establish reference for FLASH and VHEE. We explore detector response to electron energy and residual range both experimentally and computationally. Multilayer HEC detectors were constructed using 1×-10× basic modules of Aluminum(Al)_aerogel(A)_Tantalum(Ta) with 10-70 µm layer thicknesses. Signals are collected from all electrodes (3-21, depending on module multiplicity) with zero external voltage bias. Measurements are acquired as a function of depth(z) in water equivalent plastic using Varian TrueBeam for energies E=6,9,12,15 MeV (SAD=105cm, 6×6 cone, 1000 MU/min). Computational simulations of identical detector geometries are performed using the 1D deterministic code CEPXS/ONEDANT. Additionally, percent-depth-doses PDD(z), measured with diode in water, are used to explore the response of HEC for various energies and residual ranges. The current measured from Ta electrodes resembles the shape of deposited charges in water and it is proportional to the derivative of the clinical PDD corrected for contribution from photon contamination. The signal is positive on the surface, and it decreases with depth reaching a negative local minimum at z=R50, before increasing again, reaching zero at about the practical range z=Rp. In contrast, the signal from Al electrodes is shaped like the electron PDD(z) shape but with lower signal at the surface and higher bremsstrahlung tail. By subtracting the signal from Ta and Al electrodes we obtained a curve resembling PDD(z,E) after Bremsstrahlung contamination correction. Multi-layer HEC sensors exhibit characteristic responses to electron beams that are unlike responses of ion chambers or diodes. Since the sensor structures are sensitive to electronic disequilibrium, high-Z electrodes give a signal proportional to the charge deposition pattern and can be modeled using the derivative of PDD(z).

The LHCb VELO Upgrade II: design and development of the readout electronics

The LHCb collaboration proposes a Phase-II Upgrade of the detector, to be installed during the LHC Long Shutdown 4 (2032–2034). Operating in the HL-LHC environment poses significant challenges to the design of the upgraded detector, and in particular to its tracking system. The primary and secondary vertices reconstruction will become more difficult due to the increase, by a factor of 7.5, of the average number of interactions per bunch crossing. The performance of the VErtex LOcator (VELO), which is the tracking detector surrounding the interaction region, is essential to the success of this Phase-II Upgrade. Data rates are especially critical for the LHCb full software trigger, and with the expected higher particle flux, the VELO Upgrade-II detector will have to tolerate a dramatically increased data rate: assuming the same hybrid pixel design and detector geometry, the front-end electronics (ASICs) of the VELO Upgrade-II will have to cope with rates as high as 8 Ghits/s, with the hottest pixels reaching up to 500 khits/s. With this input rate, the data output from the VELO will exceed 30 Tbit/s, with potentially a further increase if more information is added to the read-out. This paper outlines the challenges being addressed and the solutions under investigation for reading out the VELO sub-detector.

A new track finding algorithm based on a multi-dimensional extension of the Hough Transform

We introduce a new pattern recognition algorithm for track finding in High Energy Physics Experiments based on an extension of the Hough Transform to multiple dimensions. A remarkable property of this algorithm is that the execution time is simply proportional to the total number of the hits to be processed, making it particularly attractive for high occupancy situations. The algorithm needs to be trained using a sufficiently large set of simulated tracks. The same track finding algorithm can be used for very different detector geometries and only the set of simulated tracks used for training needs to be changed. The particular structure of the algorithm also lends itself naturally to parallel hardware implementations which, combined with its intrinsic flexibility, should provide a most powerful tool for triggering at future colliders.

Salinity and flow pattern independent flow rate measurement in a gas-liquid flow with optimum feature selection and novel detection geometry using ANNs

This paper presents a study on the salinity determination and flow rate estimation in a two-phase air-water system. For this purpose, an automated air-water test loop capable of generating different flow patterns in a horizontal pathway was utilized to do numerous experiments at varying flow rates. A nuclear measuring setup, comprising Cs-137 and Am-241 as radiation sources, one NaI (Tl) scintillation detector to register transmission counts of Cs and three scintillator detectors for registering transmission and scattering counts from Am, was prepared. A pressure drop pipe was also employed for flow rate measurement, with MLPs were selected as the processing element. Notable innovations of this paper can be considered from two perspectives. Firstly, a novel paradigm in nuclear measurement geometry. This novelty uses the benefits of three scintillator detectors to extract features with the maximum potential for classifying and determining salinity. Secondly, there is a new method in data processing and utilizing optimum features to achieve the best performance in predicting flow rates. Results in flow rate prediction independent of salinity and flow regime indicate that the proposed paradigm and method are reliable for using in industrial fields related to multi-phase metering.

More accurate suppression of compton continuum based on list mode data acquisition technique

Compton suppression is a beneficial technique employed in gamma-spectroscopy to decrease the Compton continuum and enhance the detection efficiency for various radionuclide identification/measurement applications. However, for cascade gamma-emitters radionuclides the conventional approach of Compton suppression (i.e., surrounding HPGe with NaI(Tl)/plastic detectors) removes all coincident events and reduces the detection efficiency. In this study, to address this challenge, a new approach is proposed that uses serial geometry (i.e., NaI(Tl) detector + sample + HPGe detector), more accurate coincidence time window, and the recorded gamma-ray energy in the detectors. The approach is experimentally tested and compared with the conventional approach. The results showed that by the proposed approach for 60Co, a cascade gamma-emitter nuclide, the suppression factor (SF) is improved and only 8% of photo-peak events, compared to 25% in the conventional approach, are lost by the suppression procedure. This decrease in loss of the photo-peak events in the proposed Compton suppression approach improves the accuracy of the activity measurement of the cascade-emitter radionuclides.