Detector Calibration Research Articles

High-count-rate particle tracking in proton and carbon radiotherapy with Timepix2 operated in ultra-short acquisition time

This work investigates the operational acquisition time limits of Timepix3 and Timepix2 detectors operated in frame mode for high-count rate of high deposited energy transfer particles. Measurements were performed using alpha particles from a 241Am laboratory source and proton and carbon ion beams from a synchrotron accelerator. The particle count rate upper limit is determined by overlapping per-pixel particle signals, identifiable by the hits per pixel counter > 2, indicating the need to decrease acquisition time. On the other hand, the lower limit is the time required to collect the particle deposited charge while maintaining spectral properties. Different acquisition times were evaluated for an AdvaPIX Timepix3 detector (500 μm Silicon sensor) with standard per-pixelDigital to Analog Converter (DAC)settings and a Minipix Timepix2 detector (300 μm Silicon sensor) with standard and customized settings the pulse shaping parameter and threshold. For AdvaPIX Timepix3, spectra remained accurate down to 100 μs frame acquisition time; at 10 μs, loss of collected charge occurred, suggesting either avoiding this acquisition time or applying a correction. Timepix2 allowed acquisition times down to 100 ns for single particle track measurements even for high energy loss, enabled by a new Timepix2 feature delaying shutter closure until full particle charge collection. This work represents the first measurement utilizing Timepix-chips pixel detectors in an accelerator beam of clinical energy and intensity without the need to decrease the beam current. This is made possible by exploiting the short shutter feature in Timepix2 and a customized per-pixel energy calibration of the Timepix2 detector with a larger discharging signal value which allowed for shorterTime-over-Threshold (ToT)signal. These customized settings extend the operation of the pixel detectors to higher event rates up to 109 particles/cm2/s.

Calibration and characterization of the RED-100 detector at the Kalinin Nuclear Power Plant

RED-100 is a two-phase Xe detector designed and built for the study of coherent elastic neutrino-nucleus scattering (CEνNS) of reactor antineutrinos. A comprehensive calibration was performed in order to obtain important parameters of the detector during its operation at the Kalinin Nuclear Power Plant (Tver region, Russia). This paper outlines the analysis of calibration data, position and energy reconstruction procedures, and calculation of the efficiency of electron extraction from the liquid xenon to the gas phase.

Calibration of Cosmic Watch Desktop Muon Detector: Evaluating the Effects of Atmospheric Pressure and Material Interaction on Detection Accuracy

This study focuses on the analysis of data obtained from Cosmic Watch (CW) muon detectors. The objective is to establish a standardised procedures for the enhancement of accuracy of muon detection in varying environments. By applying correlation analysis, the linear regression line is used to addresses the impact of atmospheric pressure on muon detection rates, which is clarified in the dissertation. A significant aspect of the research involves the rectification of systematic errors, which includes inconsistencies in pressure and temporal discrepancies across groups of Cosmic Watch (CW) detectors. Furthermore, the study investigates the influence of diverse materials on muon penetration, with the detectors being covered with lead, iron, and no material, respectively. The corrected data provide more reliable detection of double- and triple-coincident events and insights into the interactions between certain material and muons. Although there are limitations, the developed calibration model provides a robust framework for future experiments involving muon detection, with potential applications in studying the properties of cosmic-ray muons, and angular distribution.

Room temperature dual-mode internal quantum deficiency measurement with propagated uncertainty to 0.03% (k = 2)

Abstract We present improvements in dual-mode calibration of predictable quantum efficient detectors and demonstrate the importance of calculating absolute uncertainties instead of relative uncertainties. We have implemented a new uncertainty component for the thermal fluctuations in the temperature signal which results in a propagated Type A uncertainty, matching the observed standard deviation. A new thermal drift correction method exploiting a monitor thermistor on the heat sink is relaxing the need for thermal stabilisation of the experimental set-up. With beam position uncertainty ±0.25 mm and background electrical power varying from 10 μW to 900 μW, the measured internal quantum deficiency (IQD) is in average 0.00% ± 0.03% (k = 2). The IQD exhibits clear systematic effects of beam position and background power, showing the need for improved design of dual-mode modules to further improve the uncertainty.

Simplified efficiency calibration methods for scintillation detectors used in nuclear remediation

Our study introduces innovative methods to address waste reduction and enhance resource efficiency in nuclear cleanup processes. We focus on sustainable nuclear technology, aligning with goals for cleaner production and environmental protection. We developed two novel methods, termed “oversimplified” and “simplified,” for easily determining the photopeak efficiency of NaI(Tl) scintillation detectors. These methods, along with a “general” solution method, were validated with calibrated radioactive sources such as 241Am, 57Co, 133Ba, 137Cs, and 60Co, and were used to commission a NaI(Tl) scintillation detector system at Chalk River Laboratories (CRL) for nuclear remediation. The system demonstrated high accuracy, making it suitable for screening unstable isotopes at contaminated sites. This screening tool significantly reduces the number of soil samples requiring detailed characterization, thereby lowering operational costs. The NaI(Tl) detector system was calibrated for near-contact geometry, which is commonly used at CRLs. Detection limits were established for this configuration. By improving the efficiency calibration of scintillation detectors, our study advances sustainable nuclear remediation practices, promoting environmental sustainability and cleaner production processes.

GENERAL RECOMMENDATIONS FOR THE SEARCH AND DETECTION OF EXPLOSIVE ORDNANCE IN THE CONDITIONS OF HIGH CONTAMINATION OF THE AREA WITH METAL FRAGMENTS

Currently, the enemy is using new mining tactics, when other sources of danger are additionally installed during mining, in particular with anti-personnel mines (APMs). This leads to accidents among sappers during operational demining. Therefore, there is an urgent problem of determining the procedure for searching for UXOs when the area is highly contaminated with metal fragments. An analysis of specialized literature has shown that the problem of searching, detecting and identifying UXOs both on land and in the water is the subject of close attention by both military specialists and researchers. Considerable attention has been paid to the testing and evaluation of metal detectors. However, the issue of searching for UXOs in highly contaminated areas with metal fragments, especially in areas of combat operations, has not been covered. The purpose of this article is to determine the procedure for organizing and conducting search and detection operations for UXOs in a highly contaminated area with nearby mines and metal fragments. At the same time, the risk of an emergency should be minimized. In this study, taking into account the fact of an increase in the number of accidents among deminers, it is proposed to adhere to the following recommendations when searching for and detecting UXOs in a highly contaminated area with metal fragments every working day before the start of the search for UXO, calibrate the metal detector to ensure confidence in the ability of the metal detector to distinguish between signals from the source of the hazard and nearby targets. Record the calibration of each metal detector in the calibration log; it is recommended to carry out work on the search for UXO using a metal detector within a 1-meter wide clearance strip using a base rail; it is recommended to mark the source of the hazardous signal along the edge of the search element of the metal detector, rather than determine the center of the signal; when searching for UXOs with high contamination of the area with metal fragments, it is recommended not to use probes, but to excavate the soil around the marked UXO using a shovel (scraper).

Reduction of speckle effect using galvanometer scanners in a laser-based uniform source for radiance responsivity measurement

Narrow linewidth lasers play an important role in high-spectral and high-precision radiometric calibration. In this paper, a standard uniform light source for radiometric calibration of imaging detectors and devices is designed and realized based on narrow linewidth laser and intergrating sphere. Because the speckle effect caused by laser has a great influence on the radiance transfer, galvanometer scanners were employed to reduce the speckle effect. CCD method was used to measure the nonuniformity of the middle row/column of the integrating sphere exit, and nonuniformity reduced from 2.6 % to 0.72 % when the galvanometer scanners were turned on. By superimposing 9 different regions of static speckle image, the non-uniformity is greatly reduced, which is consistent with the experimental results. The output radiance stability of the source is measured with an improvement from 8.4 × 10-5 to 2.7 × 10-5. Finally, the nonuniformity of the source is measured to be 0.15 % by a spot luminance meter.

Development of radon detectors calibration system in Cameroon

ObjectiveTo develop a radon detectors calibration system at the Research Centre for Nuclear Science and Technology (CRSTN) of the Institute of Geological and Mining Research (IRGM) in Cameroon. MethodsA transparent box named radon chamber, a certified radon source, and a reference device have been provided to Cameroon by the International Atomic Energy Agency (IAEA) within the framework of a technical cooperation project. Depending on what radon levels are expected, two different configurations (Hookup I and Hookup II) of the system are adopted. Hookup I is a closed loop, and Hookup II is an open loop that samples fresh air. ResultsThe operation of the system generates a radon concentration of up to ∼ 30,000 Bq/m3 when applied the Hookup I and of up to ∼1,000 Bq/m3 using the Hookup II configuration. For the calibration of the detectors for environmental radon monitoring, a stabilized concentration of ∼1,000 Bq/m3 is enough. Furthermore, temperature, relative humidity, and pressure, in the reference instrument ranged from 23 to 40°C, 32 to 72%, and 929 to 936 mBar, respectively. Inside the radon chamber, temperature, relative humidity, and pressure are similar to the laboratory’s condition. ConclusionThe present calibration system will be useful for the calibration of radon detectors. The system can also be used for various purposes such as research activities on radon, education on radon detection, radon measurement, radon mitigation, radon mapping, protection against radon, and research in the African region.

Measurements of Low Optical Power with Cryostat-Based Predictable Quantum Efficient Detector at Liquid Nitrogen Temperature

Abstract We have validated optical power measurements with a Predictable Quantum Efficient Detector (PQED) at liquid nitrogen temperature (77 K) at low optical power from 130 fW to 3.3 pW. Two laser wavelengths at 514 nm and 785 nm were used. The lowest measured optical power corresponds to a photon flux of 0.5·106 photons per second (785 nm). The PQED’s responsivity is linear within the relative measurement uncertainties of 8% at 0.5·106 ph/s and 1.4% at 10·106 ph/s (95% confidence level), which enables the calibration of other low photon flux detectors directly against a primary standard of optical power.

A new calibration method for radon detector in seismic systems

Radon observation is an important measurement item of seismic precursor network observation. The radon detector calibration is a key technical link for ensuring radon observation accuracy. At present, the radon detector calibration in seismic systems in China is faced with a series of bottleneck problems, such as aging and scrap, acquisition difficulties, high supervision costs, and transportation limitations of radon sources. As a result, a large number of radon detectors cannot be accurately calibrated regularly, seriously affecting the accuracy and reliability of radon observation data in China. To solve this problem, a new calibration method for radon detectors was established. The advantage of this method is that the dangerous radioactive substance, i.e., the radon source, can be avoided, but only “standard instruments” and water samples with certain dissolved radon concentrations can be used to realize radon detector calibration. This method avoids the risk of radioactive leakage and solves the current widespread difficulties and bottleneck of radon detector calibration in seismic systems in China. The comparison experiment with the traditional calibration method shows that the error of the calibration coefficient obtained by the new method is less than 5% compared with that by the traditional method, which meets the requirements of seismic observation systems, confirming the reliability of the new method. This new method can completely replace the traditional calibration method of using a radon source in seismic systems.

Efficient Fourth-Order PSTD Algorithm with Moving Window for Long-Distance EMP Propagation.

Satellite-borne electromagnetic pulse (EMP) detection technology plays an important role in military reconnaissance, space environment monitoring, and early warning of natural disasters. However, the complex ionosphere greatly distorts the waveform during propagation and poses a challenge to EMP detection. Therefore, it is necessary to conduct theoretical research on EMP propagation in the ionosphere. Conventional second-order pseudo-spectral time-domain (PSTD-2) algorithm has difficulties in keeping the stability and accuracy of waveforms in calculations over hundreds of kilometers of propagation. To overcome the difficulties, a fourth-order PSTD algorithm incorporating the moving window technique (MWPSTD-4) is proposed. In the numerical examples, the performance of MWPSTD-4 is compared with PSTD-4 and PSTD-2 in the long-distance propagation of EMP. The results show that the MWPSTD-4 improves efficiency while guaranteeing accuracy and is suitable for large-scale electromagnetic field simulation. The proposed method provides a basic algorithm to eliminate the numerical dispersion interference for calculating the long-distance propagation of EMP in complex spaces and is helpful for the design and calibration of satellite-borne EMP detectors.

Measuring the low divergent luminous flux emitted by LED torch lamps using a simple detector and a spectrometer as an alternative to an integrating sphere

The widespread use of light emitting diodes (LEDs) in various applications has necessitated accurate measurement of their photometric parameters, particularly luminous flux. While traditional methods employing integrating spheres offer precise measurements, simpler and often cheaper techniques utilizing radiometric detectors and spectrometers present viable alternatives, especially for directional emissions. This article presents a comprehensive methodology for measuring luminous flux using a simple detector and a spectrometer, discussing equipment calibration, uncertainty analysis, and validation of the described method. The study delves into the intricacies of detector and spectrometer calibration, offering insights for traceability to a known reference standard in lumen measurement practices. Additionally, the article addresses uncertainties associated with luminous flux calculations and validates the proposed method against measurements from an independent laboratory. Limitations such as spectral response variations and temperature effects on measurements are mentioned. Moreover the article encompasses formula derivations and calculations, empowering readers to create and validate their own computation tools.

Radioxenon beta-gamma coincidence efficiency for a SAUNA detector by Geant4 simulation

A simulation for SAUNA II detector was carried out using the GEANT4 platform. The results demonstrated the accuracy of the simulation, which was well consistent with the experimental results. The simulation was used to calculate the coincidence detection efficiency of each radioxenon isotope, as well as to calculate the resolution for conversion electron peaks. Furthermore, using a 137Cs point source, the simulation was also utilized to perform the beta detector calibration procedure in two scenarios: first, the 137Cs was placed close to the middle of the plastic scintillator, and second, the 137Cs was placed outside the NaI(Tl) detector. The results showed that the spectrum in the first case is better; the source is closer to the plastic detector, leading to maximum Compton scattering. In the second case, a line in the spectrum disappears, so a high-intensity source is needed. Several methods exist to determine the coincidence detection efficiency of the detector. The recommended approach is to determine the total detection efficiency for different regions of interest. The simulation was also used to investigate the effect of replacing helium with nitrogen as a xenon-carrier gas, with the nitrogen resulting in a slight improvement in coincidence detection efficiencies and conversion electron resolution.

Energy calibration of LaBr3 detectors using inherent radioactivity

In general, the energy calibration of gamma-ray detectors is carried out by using radioactive sources with well-known emission lines. The fact that the scintillator material LaBr3 includes natural radioactivity is often taken advantage of to perform an energy calibration without the need to handle an external radioactive source. For this purpose, the emission energy of photons to be detected in peaks has to be well known. Though the energies of the emission lines of the relevant isotope 138La and further information on radioactive contaminations are published with high precision, there are inconsistencies in the literature concerning the effective energies of observed photon peaks caused by inherent radioactivity. In this article, the actual peak positions are published as a result of high-precision measurements. The potential and limitations of an energy calibration of LaBr3 detectors based on the inherent radioactivity are discussed, as the emission lines of 138La are detected in clusters rather than single, clearly defined lines.

Systematic Evaluation of Uncertainty Calibration in Pretrained Object Detectors

AbstractIn the field of deep learning based computer vision, the development of deep object detection has led to unique paradigms (e.g., two-stage or set-based) and architectures (e.g., Faster-RCNN or DETR) which enable outstanding performance on challenging benchmark datasets. Despite this, the trained object detectors typically do not reliably assess uncertainty regarding their own knowledge, and the quality of their probabilistic predictions is usually poor. As these are often used to make subsequent decisions, such inaccurate probabilistic predictions must be avoided. In this work, we investigate the uncertainty calibration properties of different pretrained object detection architectures in a multi-class setting. We propose a framework to ensure a fair, unbiased, and repeatable evaluation and conduct detailed analyses assessing the calibration under distributional changes (e.g., distributional shift and application to out-of-distribution data). Furthermore, by investigating the influence of different detector paradigms, post-processing steps, and suitable choices of metrics, we deliver novel insights into why poor detector calibration emerges. Based on these insights, we are able to improve the calibration of a detector by simply finetuning its last layer.

IXPE Gas Pixel Detector characterization with the X-ray calibration facility

The X-ray Calibration Facility (XCF) is a table-top, open-design irradiation setup for research, available at the Physics Department of the University of Turin. It offers beams of photons at different energies and with various spatial and polarization configurations. These characteristics allow XCF to be a suitable facility for calibration and test of energy, position and polarization sensitive detectors.

Methodology of integrated measurements with radon diffusion chamber

Calibration of Solid-State Nuclear Track Detectors - SSNTD in the diffusion chamber in most cases assumes a constant radon concentration outside the diffusion chamber and a steady state. Although this has been proven to be a valid approximation in most cases, the fact is that the radon concentration outside the chamber is not constant. In this way, the detectors are calibrated to measure the mean radon concentration. For this reason, there is doubt if the time-dependent concentration in dwellings results in the same number of tracks on the detector as the time-averaged radon concentration for the same exposure period. To obtain an answer, time-dependent and steady-state diffusion equations for radon and its progeny were solved. Then the number of tracks on the detector was calculated for these two cases and compared. For that goal, software for solving the time-dependent diffusion equation for time-varying external radon concentration was developed. Results show that concentrations measured using a diffusion chamber are the real concentrations at the measuring site. However, it was also found that the validity of results is not a universal property, as shown in the current paper. In some cases, results can be wrong. For some extreme conditions when diffusion coefficients are disrupted calibration using stationary conditions model will lead to incorrect results of real measurements in experiments where ambiental concentration is time-varying.

LANTERN: A multichannel light calibration system for cryogenic detectors

Recent advancements in low-energy rare-event searches rely on the use of cryogenic calorimeters in order to reach extremely low energy thresholds. When attempting to accurately characterize their responses within the region of interest (ROI) these detectors face severe challenges due to the fact that traditional radioactive calibration sources produce signals above the ROI and cannot be used in low background environments.LANTERN, an optical calibration system, can instead be used to accurately study the ROI of cryogenic detectors. It utilizes LED pulses to generate photon signals to perform detector calibration. LANTERN’s current LED matrix allows for a fast characterization of up to 64 calorimeters independently, spanning energies from a few eV to hundreds of keV. Its minimal electronics and optics make it a cost-effective and customizable solution and it will be employed by the BULLKID, NUCLEUS and CRAB experiments.

Neural networks for the analysis of 2D radio-xenon beta gamma spectra

Atmospheric traces of radioactive xenon can be a strong indicator for underground nuclear fission reactions. 131mXe, 133Xe, 133mXe and 135Xe are the primary gaseous isotopes/isomers currently used to identify and classify nuclear events. During decay, each of these radioactive species produces a unique beta-gamma energy spectra, which can be measured using beta-gamma coincidence counting. Current operational Xe beta-gamma spectrum analysis software relies on Region of Interest (ROI) counting (Bowyer et al. in J Environ Radioact 59(2):139–151, 2002). This algorithm occasionally produces mismeasurements, especially when quantifying meta-stable isomers, due to overlapping ROIs and shifts in detector calibration in fielded systems over time (Ringbom and Axelsson in Appl Radiat Isot 156:108950, 2020). In an attempt to better de-convolve overlapping isotope spectra we have developed a technique that applies a supervised neural-network implemented in TensorFlow with Keras to classify and quantify the isotopes and mixtures of isomers based on their beta-gamma spectra—similar to image recognition. From this, we have improved upon the false-positive rate for classification and regression models, however challenges remain with dealing with differing detector energy calibrations and with estimating measurement uncertainty.

Characterization of Gamma Spectroscopy Setup, Efficiency Calibration of HPGe detector used for Radiological substances

Background: Contamination of radiological substances in environment is one of the most important factors and harmful for living beings if the activity is high enough with long half-life.‘Gamma Spectrometry Setup’ is comparatively better for detection and analysis of gamma radiations in any type of specimens. Initiating the data acquisition setup, it’s essential to calibrate the entire setup for accuracy measurement. Materials and Methods:The main purpose of the research work is to characterize the data acquisition setup using137Cs and 60Co point sources. 137Cs emits γ-rays of 661.66 keV and 60Coemits two different γ-rays; 1173.2 KeV & 1332.5 KeV. Setup standardization is an essential part of any research works. Results: The HPGe detector used with the setup is also good enough for γ-energy detection. Detector efficiency calibration is another major task needed for activity calculation, using gamma energy lines detected in a sample detector efficiency can be calculated. Conclusion: Initiating every research experiment, the setup calibration should be checked for accurate results