Design of CsI(TI) detector system to search for lost radioactive source

This report presents a design system based on the use of CsI(TI) detectors to search for lost radioactive sources that are dangerous and harmful to individuals, including searching persons. For this purpose, the GEANT4 simulation toolkit was utilized to develop a system based on three detectors. Various simulated analyses were performed on the dose rates of the three detectors using different source–detector distances and detector separation. There were good agreement between the simulated results and the experimentally measured data. A new method was discussed to detect and search for radioactive sources based only on the dose rates in detectors with source activity. Numerical analyses were performed based on the measured dose rates and the difference of distances to determine the actual location of the lost single or multiple γ-ray sources at a specific angle. The detection limit was calculated from the background radiation to establish the sensitivity and capability of the proposed detector system. This system can be applied in fields in which it is necessary to locate unknown radioactive sources.

Monte-Carlo Simulation of Response Functions for Natural Gamma-Rays in LaBr_3 Detector System with Complex Borehole Configurations

Usually, there are several methods, e.g. experiment, interpolation experiment-based, analytic function, and Monte-Carlo simulation, to calculate the response functions in LaBr3（Ce） detectors. In logging applications, the experiment-based methods cannot be adopted because of their limitations. Analytic function has the advantage of fast calculating speed, but it is very difficult to take into account many effects that occur in practical applications. On the contrary, Monte-Carlo simulation can deal with physical and geometric configurations very tactfully. It has a distinct advantage for calculating the functions with complex configurations in borehole. A new application of LaBr3（Ce） detector is in natural gamma-rays borehole spectrometer for uranium well logging. Calculation of response functions must consider a series of physical and geometric factors under complex logging conditions, including earth formations and its relevant parameters, different energies, material and thickness of the casings, the fluid between the two tubes, and relative position of the LaBr3（Ce） crystal to steel ingot at the front of logging tube. The present work establishes Monte-Carlo simulation models for the above-mentioned situations, and then performs calculations for main gamma-rays from natural radio-elements series. The response functions can offer experimental directions for the design of borehole detection system, and provide technique basis and basic data for spectral analysis of natural gamma-rays, and for sonrceless calibration in uranium quantitative interpretation.

Genuine tripartite entanglement and geometric quantum discord in entangled three-body Unruh-DeWitt detector system

We studied the quantum correlations of a three-body Unruh-DeWitt detector system using genuine tripartite entanglement(GTE)and geometric quantum discord(GQD).We considered two representative three-body initial entangled states,namely the GHZ state and the W state.We demonstrated that the quantum correlations of the tripartite system are completely destroyed at the limit of infinite acceleration.In particular,it is found that the GQD of the two initial states exhibits“sudden change”behavior with increasing acceleration.It is shown that the quantum correlations of the W state are more sensitive than those of the GHZ state under the effect of Unruh thermal noise.The GQD is a more robust quantum resource than the GTE,and we can achieve robustness in discord-type quantum correlations by selecting the smaller energy gap in the detector.These findings provide guidance for selecting appropriate quantum states and resources for quantum information processing tasks in a relativistic setting.

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.

Electronics system for the cosmic X-ray polarization detector

This study presents an electronics system for cosmic X-ray polarization detection(CXPD).The CXPD was designed as a high-sensitivity soft X-ray polarimeter with a measurement energy range of 2-10 keV carried by a CubeSat.A stable and functionally complete electronics system under power and space constraints is a key challenge.The complete CXPD electronics system(CXPDES)comprises hardware and firmware.CXPDES adopts a three-layer electronic board structure based on functionality and available space.Two gas pixel detectors(GPDs)were placed on the top layer board,and CXPDES provided the GPDs with voltages up to-4000 V.Each GPD signal was digitized,compressed,encoded,and stored before being transmitted to the ground.The CXPDES provided stable and high-speed communication based on a scheme that separated command and data transmission,and it supports the CXPDES in-orbit upgrade.In addition,environmental monitors,silicon photomultiplier(SiPM)triggers,power management,GPDs configuration,and mode switches were included in the overall operating logic of the CXPDES.The results obtained by testing the CXPDES showed that it satisfied all the requirements of CXPD.The CXPDES provides design experience and technological readiness for future large-area X-ray polarimetry missions.

PTW Detector7293种剂量验证方法在调强放射治疗中的对比研究

目的 :对比PTW Detector729 3种验证方法在调强放射治疗(intensity modulated radiation therapy,IMRT)剂量验证中的差异。方法:回顾性选取2022年1—12月于某院完成放射治疗的鼻咽癌、肺癌、乳腺癌、宫颈癌和全脑放射治疗患者共50例,使用PTW Detector729二维电离室矩阵配合PTW RW3固体水与PTW Ocavius 4D旋转模体对50例患者的IMRT计划分别进行归零机架角2D剂量验证、实际机架角2D剂量验证和实际机架角3D剂量验证。将剂量评估阈值设为10%,统计3种验证方法在3%/1 mm、2%/2 mm、3%/2 mm和3%/3 mm 4种评估标准下的γ通过率。采用SPSS 22.0统计学软件进行数据分析。结果:在10%剂量评估阈值标准下,归零机架角2D剂量验证的γ通过率最高,差异有统计学意义(P<0.05);实际机架角2D剂量验证的γ通过率高于实际机架角3D剂量验证,差异有统计学意义(P<0.05)。3种验证方法的γ通过率在3%/1 mm、2%/2 mm、3%/2 mm和3%/3 mm 4种标准下逐渐升高,且在3%/2 mm标准下均超过90%,结果满足临床放射治疗要求。结论:3种验证方法的验证结果均能达到IMRT剂量验证实践指南要求,根据IMRT开展情况选择合适的验证方法,对确保治疗方案安全、有效实施具有重要意义。

High-speed performance self-powered short wave ultraviolet radiation detectors based onκ(ε)-Ga_(2)O_(3)

High-speed solar-blind short wavelength ultraviolet radiation detectors based onκ(ε)-Ga_(2)O_(3)layers with Pt contacts were demonstrated and their properties were studied in detail.Theκ(ε)-Ga_(2)O_(3)layers were deposited by the halide vapor phase epitaxy on patterned GaN templates with sapphire substrates.The spectral dependencies of the photoelectric properties of struc-tures were analyzed in the wavelength interval 200-370 nm.The maximum photo to dark current ratio,responsivity,detectiv-ity and external quantum efficiency of structures were determined as:180.86 arb.un.,3.57 A/W,1.78×10^(12) Hz^(0.5)∙cm·W^(-1) and 2193.6%,respectively,at a wavelength of 200 nm and an applied voltage of 1 V.The enhancement of the photoresponse was caused by the decrease in the Schottky barrier at the Pt/κ(ε)-Ga_(2)O_(3)interface under ultraviolet exposure.The detectors demon-strated could functionalize in self-powered mode due to built-in electric field at the Pt/κ(ε)-Ga_(2)O_(3)interface.The responsivity and external quantum efficiency of the structures at a wavelength of 254 nm and zero applied voltage were 0.9 mA/W and 0.46%,respectively.The rise and decay times in self-powered mode did not exceed 100 ms.

A characterization study on perovskite X-ray detector performance based on a digital radiography system

X-ray imaging technologies such as digital radiography(DR),is an important aspect of modern non-destructive testing and medical diagnosis.Innovative flexible X-ray detector technologies have recently been proposed and are now receiving increasing attention owing to their superior material flexibility compared with traditional flat-panel detectors.This work aims to study these innovative flexible X-ray detectors in terms of their effectiveness in DR imaging,such as detection efficiency and spatial resolution.To achieve this goal,first,a Monte Carlo model was developed and calibrated to an in-lab 150 kV DR imaging system containing a flat-panel X-ray detector.Second,the validated model was updated with various types of flexible X-ray detectors to assess their performance in nearly realistic conditions.Key parameters such as the detection efficiency pertaining to the crystal material and thickness were studied and analyzed across a broader energy range up to 662 keV.Finally,the imaging performance of the different detectors was evaluated and compared to that of the flat-panel detector in the 150 kV DR imaging system.The results show that the flexible detectors such as the CsPbBr3crystal detector deliver promising performance in X-ray imaging and can be applied to a wider range of application scenarios,especially those requiring accurate detection at challenging angles.

Low-noise and low-power pixel sensor chip for gas pixel detectors

Topmetal-M2 is a large-area pixel sensor chip fabricated using the GSMC 130 nm CMOS process in 2021.The pixel array of Topmetal-M2 consists of pixels of 400 rows×512 columns with a pixel pitch of 45μm×45μm.The array is divided into 16 subarrays,with pixels of 400 rows×32 columns per subarray.Each pixel incorporates two charge sensors:a diode sensor and a Topmetal sensor.The in-pixel circuit primarily consists of a charge-sensitive amplifier for energy measurements,a discriminator with a peak-holding circuit,and a time-to-amplitude converter for time-of-arrival measurements.The pixel of Topmetal-M2 has a charge input range of~0-3 k e-,a voltage output range of~0-180 mV,and a charge-voltage conversion gain of~59.56μV∕e-.The average equivalent noise charge of Topmetal-M2,which includes the readout electronic system noise,is~43.45 e-.In the scanning mode,the time resolution of Topmetal-M2 is 1 LSB=1.25μs,and the precision is^()7.41μs.At an operating voltage of 1.5 V,Topmetal-M2 has a power consumption of~49 mW∕cm~2.In this article,we provide a comprehensive overview of the chip architecture,pixel working principles,and functional behavior of Topmetal-M2.Furthermore,we present the results of preliminary tests conducted on Topmetal-M2,namely,alpha-particle and soft X-ray tests.

Flexibility potential of Cs_(2)BX_(6)(B=Hf,Sn,Pt,Zr,Ti;X=I,Br,Cl)with application in photovoltaic devices and radiation detectors

As interest in double perovskites is growing,especially in applications like photovoltaic devices,understanding their mechanical properties is vital for device durability.Despite extensive exploration of structure and optical properties,research on mechanical aspects is limited.This article builds a vacancyordered double perovskite model,employing first-principles calculations to analyze mechanical,bonding,electronic,and optical properties.Results show Cs_(2)Hfl_(6),Cs_(2)SnBr_(6),Cs_(2)SnI_(6),and Cs_(2)PtBr_(6)have Young's moduli below 13 GPa,indicating flexibility.Geometric parameters explain flexibility variations with the changes of B and X site composition.Bonding characteristic exploration reveals the influence of B and X site electronegativity on mechanical strength.Cs_(2)SnBr_(6)and Cs_(2)PtBr_(6)are suitable for solar cells,while Cs_(2)HfI_(6)and Cs_(2)TiCl_(6)show potential for semi-transparent solar cells.Optical property calculations highlight the high light absorption coefficients of up to 3.5×10^(5) cm^(-1)for Cs_(2)HfI_(6)and Cs_(2)TiCl_(6).Solar cell simulation shows Cs_(2)PtBr_(6)achieves 22.4%of conversion effciency.Cs_(2)ZrCl_(6)holds promise for ionizing radiation detection with its 3.68 eV bandgap and high absorption coefficient.Vacancy-ordered double perovskites offer superior flexibility,providing valuable insights for designing stable and flexible devices.This understanding enhances the development of functional devices based on these perovskites,especially for applications requiring high stability and flexibility.

Method for detector description conversion from DD4hep to Filmbox

DD4hep serves as a generic detector description toolkit recommended for offline software development in next-generation high-energy physics(HEP)experiments.Conversely,Filmbox(FBX)stands out as a widely used 3D modeling file format within the 3D software industry.In this paper,we introduce a novel method that can automatically convert complex HEP detector geometries from DD4hep description into 3D models in the FBX format.The feasibility of this method was dem-onstrated by its application to the DD4hep description of the Compact Linear Collider detector and several sub-detectors of the super Tau-Charm facility and circular electron-positron collider experiments.The automatic DD4hep–FBX detector conversion interface provides convenience for further development of applications,such as detector design,simulation,visualization,data monitoring,and outreach,in HEP experiments.

CVTD: A Robust Car-Mounted Video Text Detector

Text perception is crucial for understanding the semantics of outdoor scenes,making it a key requirement for building intelligent systems for driver assistance or autonomous driving.Text information in car-mounted videos can assist drivers in making decisions.However,Car-mounted video text images pose challenges such as complex backgrounds,small fonts,and the need for real-time detection.We proposed a robust Car-mounted Video Text Detector(CVTD).It is a lightweight text detection model based on ResNet18 for feature extraction,capable of detecting text in arbitrary shapes.Our model efficiently extracted global text positions through the Coordinate Attention Threshold Activation(CATA)and enhanced the representation capability through stacking two Feature Pyramid Enhancement Fusion Modules(FPEFM),strengthening feature representation,and integrating text local features and global position information,reinforcing the representation capability of the CVTD model.The enhanced feature maps,when acted upon by Text Activation Maps(TAM),effectively distinguished text foreground from non-text regions.Additionally,we collected and annotated a dataset containing 2200 images of Car-mounted Video Text(CVT)under various road conditions for training and evaluating our model’s performance.We further tested our model on four other challenging public natural scene text detection benchmark datasets,demonstrating its strong generalization ability and real-time detection speed.This model holds potential for practical applications in real-world scenarios.

Design and performance evaluation of a large field-of-view dual-particle time-encoded imager based on a depth-of-interaction detector

Time-encoded imaging is useful for identifying potential special nuclear materials and other radioactive sources at a distance.In this study,a large field-of-view time-encoded imager was developed for gamma-ray and neutron source hotspot imaging based on a depth-of-interaction(DOI)detector.The imager primarily consists of a DOI detector system and a rotary dual-layer cylindrical coded mask.An EJ276 plastic scintillator coupled with two SiPMs was designed as the DOI detector to increase the field of view and improve the imager performance.The difference in signal time at both ends and the log of the signal amplitude ratio were used to calculate the interaction position resolution.The position resolution of the DOI detector was calibrated using a collimated Cs-137 source,and the full width at half maximum of the reconstruction position of the Gaussian fitting curve was approximately 4.4 cm.The DOI detector can be arbitrarily divided into several units to independently reconstruct the source distribution images.The unit length was optimized via Am-Be source-location experiments.A multidetector filtering method is proposed for image denoising.This method can effectively reduce image noise caused by poor DOI detector position resolution.The vertical field of view of the imager was(-55°,55°)when the detector was placed in the center of the coded mask.A DT neutron source at 20 m standoff could be located within 2400 s with an angular resolution of 3.5°.

Self-powered UVC detectors based on α-Ga_(2)O_(3) with enchanted speed performance

Detectors were developed for detecting irradiation in the short-wavelength ultraviolet(UVC)interval using high-quality single-crystallineα-Ga_(2)O_(3) films with Pt interdigital contacts.The films ofα-Ga_(2)O_(3) were grown on planar sapphire substrates with c-plane orientation using halide vapor phase epitaxy.The spectral dependencies of the photo to dark current ratio,responsivity,external quantum efficiency and detectivity of the structures were investigated in the wavelength interval of 200−370 nm.The maximum of photo to dark current ratio,responsivity,external quantum efficiency,and detectivity of the structures were 1.16×10^(4) arb.un.,30.6 A/W,1.65×10^(4)%,and 6.95×10^(15) Hz^(0.5)·cm/W at a wavelength of 230 nm and an applied voltage of 1 V.The high values of photoelectric properties were due to the internal enhancement of the photoresponse associated with strong hole trapping.Theα-Ga_(2)O_(3) film-based UVC detectors can function in self-powered operation mode due to the built-in electric field at the Pt/α-Ga_(2)O_(3) interfaces.At a wavelength of 254 nm and zero applied voltage,the structures exhibit a responsivity of 0.13 mA/W and an external quantum efficiency of 6.2×10^(−2)%.The UVC detectors based on theα-Ga_(2)O_(3) films demonstrate high-speed performance with a rise time of 18 ms in self-powered mode.

Structural design of mid-infrared waveguide detectors based on InAs/GaAsSb superlattice

In the realm of near-infrared spectroscopy,the detection of molecules has been achieved using on-chip waveguides and resonators.In the mid-infrared band,the integration and sensitivity of chemical sensing chips are often constrained by the reliance on off-chip light sources and detectors.In this study,we demonstrate an InAs/GaAsSb superlattice mid-infrared waveguide integrated detector.The GaAsSb waveguide layer and the InAs/GaAsSb superlattice absorbing layer are connected through evanescent coupling,facilitating efficient and highquality detection of mid-infrared light with minimal loss.We conducted a simulation to analyze the photoelectric characteristics of the device.Additionally,we investigated the factors that affect the integration of the InAs/GaAs⁃Sb superlattice photodetector and the GaAsSb waveguide.Optimal thicknesses and lengths for the absorption lay⁃er are determined.When the absorption layer has a thickness of 0.3μm and a length of 50μm,the noise equiva⁃lent power reaches its minimum value,and the quantum efficiency can achieve a value of 68.9%.The utilization of waveguide detectors constructed with Ⅲ-Ⅴ materials offers a more convenient means of integrating mid-infra⁃red light sources and achieving photoelectric detection chips.

Development of an enhanced online tritium monitoring system using plastic scintillation fiber array

Tritium,a radioactive nuclide discharged by nuclear power plants,poses challenges for removal.Continuous online monitoring of tritium in water is crucial for real-time radiation data,given its predominant existence in the environment as water.This paper presents the design,simulation,and development of a tritium monitoring device utilizing a plastic scintillation fiber(PSF)array.Experimental validation confirmed the device’s detection efficiency and minimum detectable activity.The recorded detection efficiency of the device is 1.6×10^(-3),which exceeds the theoretically simulated value of 4×10^(-4)by four times.Without shielding,the device can achieve a minimum detectable activity of 3165 Bq L^(-1)over a 1600-second measurement duration.According to simulation and experimental results,enhancing detection efficiency is possible by increasing the number and length of PSFs and implementing rigorous shielding measures.Additionally,reducing the diameter of PSFs can also improve detection efficiency.The minimum detectable activity of the device can be further reduced using the aforementioned methods.

Effect of multiple coulomb scattering on the beam tests of silicon pixel detectors

In the research and development of new silicon pixel detectors,a collimated monoenergetic charged-particle test beam equipped with a high-resolution pixel-beam telescope is crucial for prototype verification and performance evaluation.When the beam energy is low,the effect of multiple Coulomb scattering on the measured resolution of the Device Under Test(DUT)must be considered to accurately evaluate the performance of the pixel chips and detectors.This study aimed to investigate the effect of multiple Coulomb scattering on the measured resolution,particularly at low beam energies.Simulations were conducted using Allpix^(2) to study the effects of multiple Coulomb scattering under different beam energies,material budgets,and telescope layouts.The simulations also provided the minimum energy at which the effect of multiple Coulomb scattering could be ignored.Compared with the results of a five-layer detector system tested with an electron beam at DESY,the simulation results were consistent with the beam test results,confirming the reliability of the simulations.

Probability-Enhanced Anchor-Free Detector for Remote-Sensing Object Detection

Anchor-free object-detection methods achieve a significant advancement in field of computer vision,particularly in the realm of real-time inferences.However,in remote sensing object detection,anchor-free methods often lack of capability in separating the foreground and background.This paper proposes an anchor-free method named probability-enhanced anchor-free detector(ProEnDet)for remote sensing object detection.First,a weighted bidirectional feature pyramid is used for feature extraction.Second,we introduce probability enhancement to strengthen the classification of the object’s foreground and background.The detector uses the logarithm likelihood as the final score to improve the classification of the foreground and background of the object.ProEnDet is verified using the DIOR and NWPU-VHR-10 datasets.The experiment achieved mean average precisions of 61.4 and 69.0 on the DIOR dataset and NWPU-VHR-10 dataset,respectively.ProEnDet achieves a speed of 32.4 FPS on the DIOR dataset,which satisfies the real-time requirements for remote-sensing object detection.

Countermeasure against blinding attack for single-photon detectors in quantum key distribution

Quantum key distribution(QKD),rooted in quantum mechanics,offers information-theoretic security.However,practi-cal systems open security threats due to imperfections,notably bright-light blinding attacks targeting single-photon detectors.Here,we propose a concise,robust defense strategy for protecting single-photon detectors in QKD systems against blinding attacks.Our strategy uses a dual approach:detecting the bias current of the avalanche photodiode(APD)to defend against con-tinuous-wave blinding attacks,and monitoring the avalanche amplitude to protect against pulsed blinding attacks.By integrat-ing these two branches,the proposed solution effectively identifies and mitigates a wide range of bright light injection attempts,significantly enhancing the resilience of QKD systems against various bright-light blinding attacks.This method forti-fies the safeguards of quantum communications and offers a crucial contribution to the field of quantum information security.

Metal-Halide Perovskite Submicrometer-Thick Films for Ultra-Stable Self-Powered Direct X-Ray Detectors

Metal-halide perovskites are revolutionizing the world of X-ray detectors,due to the development of sensitive,fast,and cost-effective devices.Self-powered operation,ensuring portability and low power consumption,has also been recently demonstrated in both bulk materials and thin films.However,the signal stability and repeatability under continuous X-ray exposure has only been tested up to a few hours,often reporting degradation of the detection performance.Here it is shown that self-powered direct X-ray detectors,fabricated starting from a FAPbBr_(3)submicrometer-thick film deposition onto a mesoporous TiO_(2)scaffold,can withstand a 26-day uninterrupted X-ray exposure with negligible signal loss,demonstrating ultra-high operational stability and excellent repeatability.No structural modification is observed after irradiation with a total ionizing dose of almost 200 Gy,revealing an unexpectedly high radiation hardness for a metal-halide perovskite thin film.In addition,trap-assisted photoconductive gain enabled the device to achieve a record bulk sensitivity of 7.28 C Gy^(−1)cm^(−3)at 0 V,an unprecedented value in the field of thin-film-based photoconductors and photodiodes for“hard”X-rays.Finally,prototypal validation under the X-ray beam produced by a medical linear accelerator for cancer treatment is also introduced.