Detector Response Research Articles

Analysis of fluctuations in ex-core neutron detector signal in Krško NPP during an earthquake

During an earthquake on December 29th 2020, the Krško NPP automatically shutdown due to the trigger of the negative neutron flux rate signal on the power range nuclear instrumentation. From the time course of the detector signal, it can be concluded that the fluctuation in the detector signal may have been caused by the mechanical movement of the ex-core neutron detectors or the pressure vessel components rather than the actual change in reactor power. The objective of the analysis was to evaluate the sensitivity of the neutron flux at the ex-core detector position, if the detector is moved in the radial or axial direction. In addition, the effect of the core barrel movement and core inside the baffle movement in the radial direction were analysed. The analysis is complemented by the calculation of the thermal and total neutron flux gradient in radial, axial and azimuthal directions. The Monte Carlo particle transport code MCNP was used to study the changes in the response of the ex-core detector for the above-mentioned scenarios. Power and intermediate-range detectors were analysed separately, because they are designed differently, positioned at different locations, and have different response characteristics. It was found that the movement of the power range ex-core detector has a negligible effect on the value of the thermal neutron flux in the active part of the detector. However, the radial movement of the intermediate-range detector by 5 cm results in 7%–8% change in the thermal neutron flux in the active part of the intermediate-range detector. The analysis continued with an evaluation of the effects of moving the entire core barrel on the ex-core detector response. It was estimated that the 2 mm core barrel radial oscillation results in ∼4% deviation in the power and intermediate-range detector signal. The movement of the reactor core inside baffle can contribute ∼6% deviation in the ex-core neutron detector signal. The analysis showed that the mechanical movement of ex-core neutron detectors cannot explain the fluctuations in the ex-core detector signal. However, combined core barrel and reactor core inside baffle oscillations could be a probable reason for the observed fluctuations in the ex-core detector signal during an earthquake.

Generalizing to new geometries with Geometry-Aware Autoregressive Models (GAAMs) for fast calorimeter simulation

Generation of simulated detector response to collision products is crucial to data analysis in particle physics, but computationally very expensive. One subdetector, the calorimeter, dominates the computational time due to the high granularity of its cells and complexity of the interactions. Generative models can provide more rapid sample production, but currently require significant effort to optimize performance for specific detector geometries, often requiring many models to describe the varying cell sizes and arrangements, without the ability to generalize to other geometries. We develop a geometry-aware autoregressive model, which learns how the calorimeter response varies with geometry, and is capable of generating simulated responses to unseen geometries without additional training. The geometry-aware model outperforms a baseline unaware model by over 50% in several metrics such as the Wasserstein distance between the generated and the true distributions of key quantities which summarize the simulated response. A single geometry-aware model could replace the hundreds of generative models currently designed for calorimeter simulation by physicists analyzing data collected at the Large Hadron Collider. This proof-of-concept study motivates the design of a foundational model that will be a crucial tool for the study of future detectors, dramatically reducing the large upfront investment usually needed to develop generative calorimeter models.

Silicon Carbide Timepix3 detector for quantum-imaging detection and spectral tracking of charged particles in wide range of energy and field-of-view

The hybrid architecture of the Timepix (TPX) family of detectors enables the use of different semiconductor sensors, most commonly silicon (Si), as well as high-density materials such as Cadmium Telluride (CdTe) or Gallium Arsenide (GaAs). For this purpose, we explore the potential of a silicon carbide (SiC) sensor bump-bonded on a Timepix3 detector as a radiation imaging and particle tracking detector. SiC stands as a radiation-hard material also with the ability to operate at elevated temperatures up to several hundreds of degrees Celsius. As a result, this sensor material is more suitable for radiation harsh environments compared to conventional e.g., Si sensors. In this work, we evaluate the response for precise radiation spectrometry and high-resolution particle tracking of newly developed SiC Timepix3 detector which is built and operated as a compact radiation camera MiniPIX-Timepix3 with integrated readout electronics. Calibration measurements were conducted with mono-energetic proton beams with energies of 13, 22, and 31 MeV at the U-120M cyclotron at the Nuclear Physics Institute Czech Academy of Science (NPI CAS), Prague, as well as 100 and 226 MeV at the Proton Therapy Center Czech (PTC) in Prague. High-resolution pattern recognition analysis and single-particle spectral tracking are used for detailed inspection and understanding of the sensor response. Results include distributions of deposited energy and linear energy transfer (LET) spectra. The spatial uniformity of the pixelated detector response is examined in terms of homogeneously distributed deposited energy.

Electromagnetic Pulse Interference Generated by Pulsed X/Gamma Rays on Vacuum Compton Detector Response: A Preliminary Study

Electromagnetic Pulse Interference Generated by Pulsed X/Gamma Rays on Vacuum Compton Detector Response: A Preliminary Study

PARSIFAL: A toolkit for triple-GEM parametrized simulation

PARSIFAL (PARametrized SImulation) is a fast and reliable software tool that reproduces the complete response of a triple-GEM detector to the passage of a charged particle, taking into account the main physical effects. Starting from the detector configuration and the particle information, PARSIFAL reproduces ionization, spatial and temporal diffusion, effect of magnetic field, if present, and GEM amplification to provide the dependable triple-GEM detector response. In the design and optimization stages of this kind of detectors, simulations play an important role. Accurate and robust software programs, such as GARFIELD++, can simulate the transport of electrons and ions in a gas medium and their interaction with the electric field, but they are CPU-time consuming. The necessity to reduce the processing time while maintaining the precision of a full simulation is the main driver of this work. For a given set of geometrical and electrical settings, GARFIELD++ is run once-and-for-all to provide the input parameters for PARSIFAL. Once PARSIFAL is initialized and run, it produces the detector output, including the signal induction and the output of the electronics. The results of the analysis of the simulated data obtained with PARSIFAL are compared with the results of the experimental data collected during a testbeam: some tuning factors are applied to the simulation to improve the agreement. This paper describes the structure of the code and the methodology used to match the output to the experimental data. Program summaryProgram Title: PARSIFALCPC Library link to program files:https://doi.org/10.17632/rg85kzjwwj.1Developer's repository link:https://github.com/Hilldar/PARSIFAL (branch triplegem)Licensing provisions: GPLv3Programming language: C++Nature of problem: Monte Carlo (MC) simulations are widely used in design and development of detectors for high energy physics as well as during data taking to understand how the detector geometry, acceptance, efficiency affect the experimental observations and hence infer the systematic effects. For triple-GEM detectors (one of the most used Micro Pattern Gaseous Detectors), the simulation of their response to the passage of particles is usually performed with GARFIELD++ (CERN) which provides a microscopic description of the signal creation, from the interaction of the particle with the gas to the induction of the signal on the anode. This detailed simulation is heavy and CPU-time consuming, hence it requires long computing periods to gain high statistics.Solution method: PARSIFAL software provides the MC simulation of the response of a triple-GEM detector to the passage of a charged particle by splitting the simulation into four independent steps: ionization, electron drift in gas and magnetic field, avalanche formation in the multiplication stages, signal induction on the anode and response of the electronics (APV-25 chip). For each step, PARSIFAL samples the variables of interest from distributions, obtained by using a set of input parameters. These parameters are extracted from a simulation run only once with GARFIELD++. Since the sampling is much faster than a full GARFIELD++ simulation, this reduces the CPU-time to collect a sample with high statistics. The results extracted by the PARSIFAL simulation have been tuned with experimental data collected during a testbeam at CERN and show a satisfactory compatibility.

A Rule-Based Automated Chemical Recognition Algorithm for a Multi-Cell Multi-Detector Micro Gas Chromatograph

A chemical recognition algorithm is an integral part of any autonomous microscale gas chromatography (µGC) system for automated chemical analysis. For a multi-detector µGC system, the chemical analysis must account for the retention time of each chemical analyte as well as the relative response of each detector to each analyte, i.e., the detector response pattern (DRP). In contrast to the common approaches of heuristically using principal component analysis and machine learning, this paper reports a rule-based automated chemical recognition algorithm for a multi-cell, multi-detector µGC system, in which the DRP is related to theoretical principles; consequently, this algorithm only requires a small amount of calibration data but not extensive training data. For processing both the retention time and the raw DRP, the algorithm applies rules based on expert knowledge to compare the detected peaks; these rules are located in a customized software library. Additionally, the algorithm provides special handling for chromatogram peaks with a small signal-to-noise ratio. It also provides separate special handling for asymmetrical peaks that may result from surface adsorptive analytes. This work also describes an experimental evaluation in which the algorithm used the relative response of two complementary types of capacitive detectors as well as a photoionization detector that were incorporated into the µGC system of interest. In these tests, which were performed on chromatograms with 21–31 peaks for each detector, the true positive rate was 96.3%, the true negative rate was 94.1%, the false positive rate was 5.9%, and the false negative rate was 3.7%. The results demonstrated that the algorithm can support µGC systems for automated chemical screening and early warning applications.

Comparative investigation of detector responses and measurement uncertainties in fast-neutron coincidence counting for nuclear material accountancy

Fast-neutron measurement with organic scintillators has been considered one of the alternative techniques to thermal neutron measurement based on He-3 proportional counters, due to their economic and measurement-uncertainty potential for nuclear material accountancy. Nevertheless, highly suppressed neutron detection efficiencies and nuclide-dependent features indicated in the fast system as well as the utilization of pulse-shape discrimination which necessitates a significant energy threshold could lead to challenges in terms of characterizing nuclear material samples. This work confirmed a reasonable similarity of simulated results to experimental results concerning the non-linear light-output function of proton recoils. Consequently, nuclide-dependent detector responses and measurement uncertainty were investigated with varying diverse measurement parameters (the number of detectors, measurement time, and sample quantity). Also, comparative studies were conducted for the ACP Safeguards Neutron Counter, a developed thermal system, and the Fission Informative Neutron-based ACcounting, the proposed fast system currently under development by Korea Atomic Energy Research Institute, for passive non-destructive assay of special nuclear materials.

Subcritical neutron noise measurements for plutonium systems with varying geometry and mass

Recently, experiments were performed at the National Criticality Experiments Research Center (NCERC) with Zero Power Physics Reactor (ZPPR) plates in two very different geometries. The intent of this set of experiments was to provide the EUCLID (Experiments Underpinned by Computational Learning for Improvements in Nuclear Data) project team measured data of multiple radiation detector responses to be used in an adjustment of plutonium nuclear data. The work shown in this paper will focus on multiplicity results measured for subcritical arrangements of ZPPR plates in the two geometries. The Hage–Cifarelli formalism of the Feynman variance-to-mean method, a moments-based time-correlated neutron noise approach, was used. A validation of the methodology used to estimate uncertainties in the moments was performed and is presented. The effective neutron multiplication factor (keff) value were inferred from this analysis. The keffvalues were compared to simulated values using the radiation transport code Monte Carlo N-Particle® (MCNP). The results shown in this work provide evidence of larger bias in keffvalues as the geometric buckling of the system increases. This effect will be important for nuclear data validation and future adjustments of plutonium nuclear data.

Differentiating multi-MeV, multi-ion spectra with CR-39 solid-state nuclear track detectors

The development of high intensity petawatt lasers has created new possibilities for ion acceleration and nuclear fusion using solid targets. In such laser-matter interaction, multiple ion species are accelerated with broad spectra up to hundreds of MeV. To measure ion yields and for species identification, CR-39 solid-state nuclear track detectors are frequently used. However, these detectors are limited in their applicability for multi-ion spectra differentiation as standard image recognition algorithms can lead to a misinterpretation of data, there is no unique relation between track diameter and particle energy, and there are overlapping pit diameter relationships for multiple particle species. In this report, we address these issues by first developing an algorithm to overcome user bias during image processing. Second, we use calibration of the detector response for protons, carbon and helium ions (alpha particles) from 0.1 to above 10 MeV and measurements of statistical energy loss fluctuations in a forward-fitting procedure utilizing multiple, differently filtered CR-39, altogether enabling high-sensitivity, multi-species particle spectroscopy. To validate this capability, we show that inferred CR-39 spectra match Thomson parabola ion spectrometer data from the same experiment. Filtered CR-39 spectrometers were used to detect, within a background of ~ 2 × 1011 sr−1 J−1 protons and carbons, (1.3 ± 0.7) × 108 sr−1 J−1 alpha particles from laser-driven proton-boron fusion reactions.

Pre-Launch Spectral Calibration of the Absorbed Aerosol Sensor.

Spectral calibration consists of the calibration of wavelengths and the measurement of the instrument's spectral response function (SRF). Unlike conventional slits, the absorbed aerosol sensors (AAS) are used as a slit homogenizer, in which the SRF is not a conventional Gaussian curve. To be more precise, the SRF is the convolution of the slit function of the spectrometer, the line spread function of the optical system, and the detector response function. The SRF of the slit homogenizer is a flat-topped multi-Gaussian function. Considering the convenience of fitting, a super-Gaussian function, which has a distribution similar to the flat-topped multi-Gaussian function, is employed to fit the measured data in a spectral calibration. According to the results, the SRF's shapes resembling a Gaussian curve with a flat top could be derived, which contains a full width at half maximum (FWHM) of 1.78-1.82 nm for the AAS. The results show that the correlation is about 0.99, which indicates the usefulness of the fitting function that could better characterize the SRF of the instrument.

Determination of the linear behavior of FC detectors in Isfahan MNSR using ex-core offline and online experiments

The linear behavior of fission chamber (FC) neutron detectors in Isfahan miniature neutron source reactor (MNSR) was investigated experimentally. FC neutron detectors are installed near the reactor core to measure the produced neutron flux in the core. The linearity of the response of these detectors is important because the measured neutron flux by them is one of the important methods in determining and controlling the reactor power and therefore affects the safety of the reactor. For this purpose, the measured neutron fluxes by these detectors at different reactor powers were compared with the measured neutron flux at the output of the external beam tubes by different methods. In this study, two online and offline neutron flux detection methods were used to analysis the linear behavior of MNSR neutron detectors. The BF3 detector and solid-state nuclear track detector (SSNTD) were used to determine the neutron flux in the online and offline methods, respectively. The results of two diverse methods showed that the response of MNSR FC detectors for measuring the reactor power is linear with acceptable accuracy in the neutron flux range between 5×107 to 1012n.cm−2. s−1, which is equivalent to reactor power of 1.5 W to 30 kW.

Experimental and Monte Carlo study of energy response of BEO-based OSL detectors within photon energy range up to 15 MeV.

Response of personal dosemeters to high energy photon radiation is of great interest nowadays due to a spread of new radiation technologies and the expansion of occupational exposure domains. ICRU95 publication has expanded the range of relevant photon energies upwards, setting new horizons for individual monitoring. Beryllium oxide (BeO) material is increasingly popular due to its excellent optically stimulated luminescence (OSL) properties, simple readout and reasonable energy response in the low energy (below 100keV) range. The study considers energy dependence of OSL response at higher photon energies. Energy deposition of monoenergetic photons with energy up to 15MeV in the BeO chips of various thickness was modeled with Monte Carlo MCNP 6.2 code. Benchmark experiments were conducted at LINAC with high voltage of 6, 10 and 15 MV resulting in respective incident photon spectra. The findings of this study add knowledge regarding behavior of BeO personal dosemeters in the photon fields within the energy range above 3MeV.

A comprehensive Monte Carlo simulation of the neutron response of multi-element microdosimetric detectors based on THick Gas Electron Multiplier.

We present comprehensive Monte Carlo simulations for the neutron response of the multi-element microdosimetric detector based on THick Gas Electron Multiplier (THGEM). Simulations were carried out using the MCNP6.2 code to calculate the deposited energy spectrum in the gaseous sensitive volumes for three different configurations, 7 × 3, 19 × 5, 37 × 7 that occupy a cylindrical volume of 5-cm diameter by 5-cm length. The energy response was computed from 10keV to 2MeV. The response variation was investigated between sensitive volumes as well as between layers. The simulated energy response showed a good agreement against the evaluated fluence-to-kerma conversion coefficients in the energy region 10-100keV, whereas discrepancies were observed in the region above 250keV. The angular response simulations showed a variation of less than 10%.

Treating detector systematics via a likelihood free inference method

Estimating the impact of systematic uncertainties in particle physics experiments is challenging, especially since the detector response is unknown analytically in most situations and needs to be estimated through Monte Carlo (MC) simulations. Typically, detector property variations are parameterized in ways that implicitly assume a specific physics model, which can introduce biases on quantities measured by an analysis. In this paper, we present a method to recover a model-independent, event-wise estimation of the detector response variation by applying a likelihood-free inference method to a set of MC simulations representing discrete detector realizations. The method provides a re-weighting scheme for every event, which can be used to apply the effects of detector property variations fully decoupled from the assumed physics model. Using a toy MC example inspired by fixed-baseline neutrino oscillation experiments, we demonstrate the performance of our method. We show that it fully decouples the modeling of the detector response from the physics parameters to be measured in a MC forward-folding analysis.

Structural Design and Verification of an Effective-Area Measurement Device Detection System.

The effective-area method is a new way to measure aperture area. It defines aperture area by directly using the beam-limiting effect of the aperture in radiometric measurement. Due to the special structure of the measurement device, it is necessary to find a suitable method to design the detection system. In this paper, the measurement system model is constructed in the TracePro program. The real circumstances of light propagation for the measurement beam are simulated, and the responses of the detector are given. It is proved that the relative change in the detector response is the lowest when the detector is at the position of 132°. And this is the best structure design of the detection system. The experimental results are designed to verify the feasibility of the structure design of the detection system.

Electrophoretic Determination of L-Carnosine in Health Supplements Using an Integrated Lab-on-a-Chip Platform with Contactless Conductivity Detection.

The health supplement industry is one of the fastest growing industries in the world, but there is a lack of suitable analytical methods for the determination of active compounds in health supplements such as peptides. The present work describes an implementation of contactless conductivity detection on microchip technology as a new strategy for the electrophoretic determination of L-carnosine in complex health supplement formulations without pre-concentration and derivatization steps. The best results were obtained in the case of +1.00 kV applied for 20 s for injection and +2.75 kV applied for 260 s for the separation step. Under the selected conditions, a linear detector response of 5 × 10-6 to 5 × 10-5 M was achieved. L-carnosine retention time was 61 s. The excellent reproducibility of both migration time and detector response confirmed the high precision of the method. The applicability of the method was demonstrated by the determination of L-carnosine in three different samples of health supplements. The recoveries ranged from 91 to 105%. Subsequent analysis of the samples by CE-UV-VIS and HPLC-DAD confirmed the accuracy of the obtained results.

Reconstruction of point events in liquid-scintillator detectors subjected to total internal reflection

The outer water buffer is an economic option to shield the external radiative backgrounds for liquid-scintillator neutrino detectors. Since the refractive index of the liquid scintillator is larger than that of water, the consequential total internal reflection of scintillation light at the media boundary introduces extra complexity to the detector optics. This paper develops a precise detector-response model by investigating how total internal reflection complicates photon propagation and degrades reconstruction. We first parameterize the detector response by regression, providing an unbiased energy and vertex reconstruction in the total internal reflection region while keeping the number of parameters under control. From the experience of event degeneracy at the Jinping prototype, we identify the root cause as the multimodality in the reconstruction likelihood function, determined by the refractive index of the buffer, detector scale and PMT coverage. To avoid multimodality, we propose a straightforward criterion based on the expected photo-electron-count ratios between neighboring PMTs. The criterion will be valuable for the success in future liquid-scintillator detectors by guaranteeing the effectiveness of event reconstruction.

Dispersion-corrected extracorporeal arterial input functions in PET studies of mice: a comparison to intracorporeal microprobe measurements

BackgroundKinetic modelling of dynamic PET typically requires knowledge of the arterial radiotracer concentration (arterial input function, AIF). Its accurate determination is very difficult in mice. AIF measurements in an extracorporeal shunt can be performed; however, this introduces catheter dispersion. We propose a framework for extracorporeal dispersion correction and validated it by comparison to invasively determined intracorporeal AIFs using implanted microprobes.ResultsThe response of an extracorporeal radiation detector to radioactivity boxcar functions, characterised by a convolution-based dispersion model, gave best fits using double-gamma variate and single-gamma variate kernels compared to mono-exponential kernels for the investigated range of flow rates. Parametric deconvolution with the optimal kernels was performed on 9 mice that were injected with a bolus of 39 ± 25 MBq [18F]F-PSMA-1007 after application of an extracorporeal circulation for three different flow rates in order to correct for dispersion. Comparison with synchronous implantation of microprobes for invasive aortic AIF recordings showed favourable correspondence, with no significant difference in terms of area-under-curve after 300 s and 5000 s. One-tissue and two-tissue compartment model simulations were performed to investigate differences in kinetic parameters between intra- and extracorporeally measured AIFs. Results of the modelling study revealed kinetic parameters close to the chosen simulated values in all compartment models.ConclusionThe high correspondence of simultaneously intra- and extracorporeally determined AIFs and resulting model parameters establishes a feasible framework for extracorporeal dispersion correction. This should allow more precise and accurate kinetic modelling in small animal experiments.

Increasing Flame Ionization Detector Response by Silylation: The Effective Carbon Number of Carboxylic Acids

Detector response of carboxylic acids (C2–C12, straight and branched chain) were investigated using a flame ionization detector (FID) in a capillary gas chromatographic system. The response of the FID for hydrocarbons is almost directly proportional to the carbon quantity introduced into the flame. Heteroatoms in the molecule reduce signal magnitude, depending on their quality and on the bond they are involved in. We expressed this reduced response with the effective carbon number (ECN). We determined the ECN contribution (ΔECN) of the carboxyl group on the alkyl skeleton. We examined how the responses of carboxylic acids change if trimethylsilyl derivatives are evaluated and we compared the ECN of the neat and derivatized form.

Universal response method for accurate quantitative analysis of the impurities in quinolone antibiotics using liquid chromatography coupled with diode array detector and charged aerosol detector

HPLC method is the standard method for the separation and quantification of impurities from quinolone antibiotics. However, due to the large differences in the UV absorption of the impurities in quinolone antibiotics, quantitative analysis without the availability of corresponding reference substances currently poses a challenge. A sensitive and direct method using high performance liquid chromatography coupled with diode array detector and charged aerosol detector (HPLC-DAD-CAD) was developed for the analysis of impurities in quinolone antibiotics. The chromatographic conditions were optimized for good separation and output signal of CAD detector by response surface method (RSM). The systematic variation of CAD parameter settings, such as nebulization temperature, filter constant and power function value (PFV), were used to study the effect of on the detector response of signal-to-noise ratios (S/N) and linearity for ofloxacin, ciprofloxacin and their impurities. In the method validation, good linearity of each component was obtained with coefficient of determination (r) greater than 0.999 in the range of 0.5–300 μg mL−1. The average recoveries of each component were 99.02–102.39 % by DAD, were 98.22–101.91 % by CAD, RSDs were less than 2.5 % for intra-day and inter-day precision by DAD-CAD, with good precision and accuracy. The correction factor experimental results showed that the developed method provided a uniform response to the impurities with differences chromophores and could unbiasedly and directly detect the impurities in quinolone antibiotics. The method is first reported application of HPLC-DAD-CAD method for the analysis of impurities in quinolone antibiotics and it can be used for quality control of quinolone antibiotics.