Optimized online filter stack spectrometer for ultrashort X-ray pulses

Currently,with the advent of high-repetition-rate laser-plasma experiments,the demand for online diagnosis for the X-ray spectrum is increasing because the laser-plasma-generated X-ray spectrum is very important for characterizing electron dynamics and applications.In this study,scintillators and silicon PIN(P-type–intrinsic-N-type semiconductor)diodes were used to construct a wideband online filter stack spectrometer.The X-ray sensor and filter arrangement was optimized using a genetic algorithm to minimize the condition number of the response matrix.Consequently,the unfolding error was significantly reduced based on numerical experiments.The detector responses were quantitatively calibrated by irradiating the scintillator and PIN diode with various nuclides and comparing the measuredγ-ray peaks.A prototype 15-channel spectrometer was developed by integrating an X-ray detector with front-and back-end electronics.The prototype spectrometer could record X-ray pulse signals at a repetition rate of 1 kHz.Furthermore,an optimized spectrometer was employed to record the real-time spectra of laser-driven bremsstrahlung sources.This optimized spectrometer offers a compact solution for spectrum diagnostics of ultrashort X-ray pulses,exhibiting improved accuracy in terms of spectrum measurements and repetition rates,and could be widely used in next-generation high-repetition-rate high-power laser facilities.

Design of hadronic calorimeter for DarkSHINE experiment

The sensitivity of the dark photon search through invisible decay final states in low-background experiments relies sig-nificantly on the neutron and muon veto efficiencies,which depend on the amount of material used and the design of the detector geometry.This paper presents the optimized design of the hadronic calorimeter(HCAL)used in the DarkSHINE experiment,which is studied using a GEANT4-based simulation framework.The geometry is optimized by comparing a traditional design with uniform absorbers to one that uses different thicknesses at different locations on the detector,which enhances the efficiency of vetoing low-energy neutrons at the sub-GeV level.The overall size and total amount of material used in the HCAL are optimized to be lower,owing to the load and budget requirements,whereas the overall performance is studied to satisfy the physical objectives.

Development of a scintillating-fiber-based beam monitor for the coherent muon-to-electron transition experiment

The coherent muon-to-electron transition(COMET)experiment is a leading experiment for the coherent conversion of μ^(-)N→e^(-)N using a high-intensity pulsed muon beamline,produced using innovative slow-extraction techniques.Therefore,it is critical to measure the muon beam characteristics.We set up a muon beam monitor(MBM),where scintillating fibers woven in a cross shape were coupled to silicon photomultipliers to measure the spatial profile and timing structure of the extracted muon beam for the COMET.The MBM detector was tested successfully with a proton beamline at the China Spallation Neutron Source and took data with good performance in the commissioning run.The development of the MBM,including its mechanical structure,electronic readout,and beam measurement results,are discussed.

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.

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.

FPGA implementation of 500-MHz high-count-rate high-time-resolution real-time digital neutron-gamma discrimination for fast liquid detectors

Fast neutron flux measurements with high count rates and high time resolution have important applications in equipment such as tokamaks.In this study,real-time neutron and gamma discrimination was implemented on a self-developed 500-Msps,12-bit digitizer,and the neutron and gamma spectra were calculated directly on an FPGA.A fast neutron flux measurement system with BC-501A and EJ-309 liquid scintillator detectors was developed and a fast neutron measurement experiment was successfully performed on the HL-2 M tokamak at the Southwestern Institute of Physics,China.The experimental results demonstrated that the system obtained the neutron and gamma spectra with a time accuracy of 1 ms.At count rates of up to 1 Mcps,the figure of merit was greater than 1.05 for energies between 50 keV and 2.8 MeV.

Production and test of sPHENIX W/SciFiber electromagnetic calorimeter blocks in China

The sPHENIX experiment is a new generation of large acceptance detectors at the relativistic heavy ion collider at Brookhaven National Laboratory,with scientific goals focusing on probing the strongly interacting Quark–Gluon plasma with hard probes of jets,open heavy flavor particles,andγproduction.The EMCal detector,which covers the pseudo-rapidity region of|η|≤1.1,is an essential subsystem of sPHENIX.In this study,we focused on producing and testing EMCal blocks covering a pseudo-rapidity of|η|∈[0.8,1.1].These,in conjunction with the central pseudo-rapidity EMCal blocks,significantly enhance the sPHENIX physics capability of the jet andγparticle measurements.In this paper,the detector module production and testing of sPHENIX W-powder/scintillating fiber(W/ScFi)electromagnetic calorimeter blocks are presented.The selection of the tungsten powder,mold fabrication,QA procedures,and cosmic ray test results are discussed.

In-beam gamma rays of CSNS Back-n characterized by black resonance filter

The back-streaming white-neutron beamline(Back-n)of the China Spallation Neutron Source is an essential neutronresearch platform built for the study of nuclear data,neutron physics,and neutron applications.Many types of cross-sectional neutron-reaction measurements have been performed at Back-n since early 2018.These measurements have shown that a significant number of gamma rays can be transmitted to the experimental stations of Back-n along with the neutron beam.These gamma rays,commonly referred to as in-beam gamma rays,can induce a non-negligible experimental background in neutron-reaction measurements.Studying the characteristics of in-beam gamma rays is important for understanding the experimental background.However,measuring in-beam gamma rays is challenging because most gamma-ray detectors are sensitive to neutrons;thus,discriminating between neutron-induced signals and those from in-beam gamma rays is difficult.In this study,we propose the use of the black resonance filter method and a CeBr_(3) scintillation detector to measure the characteristics of the in-beam gamma rays of Back-n.Four types of black resonance filters,^(181)Ta,^(59)Co,^(nat)Ag,and^(nat)Cd,were used in this measurement.The time-of-flight(TOF)technique was used to select the detector signals remaining in the absorption region of the TOF spectra,which were mainly induced by in-beam gamma rays.The energy distribution and flux of the in-beam gamma rays of Back-n were determined by analyzing the deposited energy spectra of the CeBr_(3) scintillation detector and using Monte Carlo simulations.Based on the results of this study,the background contributions from in-beam gamma rays in neutron-reaction measurements at Back-n can be reasonably evaluated,which is beneficial for enhancing both the experimental methodology and data analysis.

Performance of compact plastic scintillator strips with wavelength shifting fibers using a photomultiplier tube or silicon photomultiplier readout

This study presents the design and performance results for compact plastic scintillator strips using a wavelength shifting fiber(WLS-fiber)readout with dimensions of 0.1 m×0.02 m×2 m.This approach was evaluated as a candidate for a cosmic-ray muon detector for the Taishan Antineutrino Observatory(JUNO-TAO).The strips coupled with 3-inch photomultiplier tubes(PMTs)were measured and compared between the single-end and double-end readout options.Additionally,a strip using the double-end option coupling with a silicon photomultiplier(SiPM)was further evaluated and compared with the results obtained using PMTs.The performance of the strips was determined by a detailed survey along their length with a cosmicray muon after detailed characterization of the 3-inch PMTs and SiPMs.The proposed design employing a compact plastic scintillator strip with WLS-fiber coupling to a SiPM provides a good choice for cosmic-ray muon veto detectors,particularly when detector dimensions must be limited.

Conceptual design of a Cs2LiLaBr6 scintillator‑based neutron total cross section spectrometer on the back‑n beam line at CSNS

To reduce the experimental uncertainty in the 235 U resonance energy region and improve the detection efficiency for neutron total cross section measurements compared with those obtained with the neutron total cross section spectrometer(NTOX), a dedicated lithium-containing scintillation detector has been developed on the Back-n beam line at the China Spallation Neutron Source. The Fast Scintillator-based Neutron Total Cross Section(FAST) spectrometer has been designed based on a Cs2Li La Br6(CLLB) scintillator considering the γ-ray flash and neutron environment on the Back-n beam line. The response of the CLLB scintillator to neutrons and γ-rays was evaluated with different 6Li/7 Li abundance ratios using Geant4. The neutron-γdiscrimination performance of the CLLB has been simulated considering different scintillation parameters, physical designs,and light readout modes. A cubic 6Li-enriched( > 90%) CLLB scintillator, which has a thickness of 4-9 mm and side length of no less than 50 mm to cover the Φ 50 mm neutron beam at the spectrometer position, has been proposed coupling to a side readout SiPM array to construct the FAST spectrometer. The developed simulation techniques for neutron-γ discrimination performance could provide technical support for other neutron-induced reaction measurements on the Back-n beam line.

Advances in nuclear detection and readout techniques

“A Craftsman Must Sharpen His Tools to Do His Job,”said Confucius.Nuclear detection and readout techniques are the foundation of particle physics,nuclear physics,and particle astrophysics to reveal the nature of the universe.Also,they are being increasingly used in other disciplines like nuclear power generation,life sciences,environmental sciences,medical sciences,etc.The article reviews the short history,recent development,and trend of nuclear detection and readout techniques,covering Semiconductor Detector,Gaseous Detector,Scintillation Detector,Cherenkov Detector,Transition Radiation Detector,and Readout Techniques.By explaining the principle and using examples,we hope to help the interested reader underst and this research field and bring exciting information to the community.

Design optimization of plastic scintillators with wavelength-shifting fibers and silicon photomultiplier readouts in the top veto tracker of the JUNO-TAO experiment

Plastic scintillators(PSs)embedded with wavelength-shifting fibers are widely used in high-energy particle physics,such as in muon taggers,as well as in medical physics and other applications.In this study,a simulation package was built to evaluate the effects of the diameter and layout of optical fibers on the light yield with different configurations.The optimal optical configuration was designed based on simulations and validated using two PS prototypes under certain experimental condi-tions.A top veto tracker(TVT)for the JUNO-TAO experiment,comprising four layers of 160 strips of PS,was designed and evaluated.The threshold was evaluated when the muon tagging efficiency of a PS strip was>99%.The efficiency of three layer out of four layer of TVT is>99%,even with a tagging efficiency of a single strip as low as 97%,using a threshold of 10 photoelectrons and assuming a 40%silicon PM photon detection efficiency.

Data-driven simultaneous vertex and energy reconstruction for large liquid scintillator detectors

High-precision vertex and energy reconstruction are crucial for large liquid scintillator detectors such as that at the Jiangmen Underground Neutrino Observatory(JUNO),especially for the determination of neutrino mass ordering by analyzing the energy spectrum of reactor neutrinos.This paper presents a data-driven method to obtain a more realistic and accurate expected PMT response of positron events in JUNO and develops a simultaneous vertex and energy reconstruction method that combines the charge and time information of PMTs.For the JUNO detector,the impact of the vertex inaccuracy on the energy resolution is approximately 0.6%.

Suppression of Plasma Bubbles over South America under Weak Geomagnetic Perturbations

During a long-term Equatorial Plasma Bubbles(EPBs)occurrence between October 2020 and March 2021,a significant EPB suppression event was identified on November 22 and the observations from multi-instrument have been utilized to investigate this event.Global-scale Observations of the Limb and Disk(GOLD)satellite observed prominent EPBs between 23:40 UT and 23:55 UT during the long-term occurrence days.However,no dark stripes representing EPBs were observed on November 22,and the Equatorial Ionization Anomaly(EIA)structure remained intact.The Total Electron Content(TEC)maps show that these EPBs appeared in the region between 35°W and 65°W longitudes and the magnitudes of the TEC loss in EPBs regions were about 20 TECU.Except for 22 November,the S4 index was consistently greater than 0.6 throughout November,indicating significant ionospheric scintillation.The Rate Of TEC Index(ROTI)maps revealed that the spatial extent and intensity of EPBs increased after their suppression,and the EPBs were locally generated.The swarm electron density measurements indicated that the variation amplitudes of EPBs at 510 km altitude were approximately 3 to 5 times larger than that at 460 km altitude.The impact region of EPBs at 510 km was between 15°S and 20°N latitudes,while at 460 km,it was between 0°and 17°N latitudes.During the period of EPB suppression,the average h’f at three ionosonde stations decreased by about 50 km,and the vertical drift velocity(V z)approached~0 m/s while it was more than 20 m/s during the long-term occurrence.

Relationships between ionospheric parameters derived from ionosonde observations and characteristics of post-sunset GHz scintillation during high solar activities(2012−2013)at Sanya(18.3°N,109.6°E),China

In this study,we present characteristics of post-sunset GHz scintillation occurrence and their correlations with ionospheric parameters derived from ionosonde observations in high solar activity years(2012−2013)of solar cycle 24 at Sanya(18.3°N,109.6°E;dip lat.:12.8°N),China.The analyzed data include the F_(2)-layer’s critical frequency(foF_(2)),peak height(h_(m)F_(2)),and minimum virtual height(h’F),as well as the scale height around the F_(2)-layer peak(H_(m)),and virtual height(h’F_(5))and true height(hF_(5))measured at 5 MHz.We have investigated relationships between the equinoctial asymmetry of these scintillations and these ionospheric parameters.In addition,we calculate the growth rates of Rayleigh−Taylor instability on the basis of the ionosonde measurements and theoretical models,respectively.We find that the equinoctial asymmetry of scintillation onset time is associated with the scale length of the vertical electron density gradient(L),which has been shown to affect the growth of Rayleigh−Taylor instability at the bottom of the F-layer.The seasonal variations of foF_(2),H_(m)and scale length of vertical electron density gradient appear to cause the seasonal variations of scintillation occurrence;the equinoctial asymmetry of scintillation occurrence rate over low latitudes appears to be related to background electron density and vertical drifts in the F-layer around time of sunset.Further study is required to explain the observed correlational weakness in low latitudes between scintillation strength,represented by the daily maximum S4,and daily maximum values of foF_(2),h_(m)F_(2),h’F,H_(m),and also the drifts.

Discrimination of pp solar neutrinos and^(14)C double pile-up events in a large-scale LS detector

As a unique probe,the precision measurement of pp solar neutrinos is important for studying the sun’s energy mechanism as it enables monitoring the thermodynamic equilibrium and studying neutrino oscillations in the vacuum-dominated region.For a large-scale liquid scintillator detector,a bottleneck for pp solar neutrino detection is the pile-up events of intrinsic14C decay.This paper presents a few approaches to discriminating between pp solar neutrinos and ^(14)C pile-up events by considering the differences in their time and spatial distributions.In this study,a Geant4-based Monte Carlo simulation is conducted.Multivariate analysis and deep learning technology are adopted to investigate the capability of ^(14)C pile-up reduction.The BDTG (boosted decision trees with gradient boosting) model and VGG network demonstrate good performance in discriminating pp solar neutrinos and ^(14)C double pile-up events.Under the ^(14)C concentration assumption of 5×10-18g/g,the signal significance can achieve 10.3 and 15.6 using the statistics of only one day.In this case,the signal efficiency for discrimination using the BDTG model while rejecting 99.18% ^(14)C double pile-up events is 51.1%,and that for the case where the VGG network is used while rejecting 99.81%of the ^(14)C double pile-up events is 42.7%.

Performance optimization of scintillator neutron detectors for EMD in CSNS

Chinese Spallation Neutron Source(CSNS) has successfully produced its first neutron beam in 28th August 2017. It has been running steadily from March, 2018. According to the construction plan, the engineering materials diffractometer(EMD) will be installed between 2019–2023. This instrument requires the neutron detectors with the cover area near3 m2in two 90° neutron diffraction angle positions, the neutron detecting efficiency is better than 40%@1A, and the spatial resolution is better than 4 mm×200 mm in horizontal and vertical directions respectively. We have developed a onedimensional position-sensitive neutron detector based on the oblique6Li F/Zn S(Ag) scintillators, wavelength shifting fibers,and Si PMs(silicon photomultipliers) readout. The inhomogeneity of the neutron detection efficiency between each pixel and each detector module, which caused by the inconsistency of the wave-length shifting fibers in collecting scintillation photons, needs to be mitigated before the installation. A performance optimization experiment of the detector modules was carried out on the BL20(beam line 20) of CSNS. Using water sample, the neutron beam with Φ5 mm exit hole was dispersed related evenly into the forward space. According to the neutron counts of each pixel of the detector module, the readout electronics threshold of each pixel is adjusted. Compared with the unadjusted detector module, the inhomogeneity of the detection efficiency for the adjusted one has been improved from 69% to 90%. The test result of the diffraction peak of the standard sample Si showed that the adjusted detector module works well.

Determination of Plutonium Isotopes in Radioactive Waste Contaminated with Uranium and Thorium

Nucleco is the Sogin Group’s Italian leading company in the sector of radiological services,radioactive waste management,decontamination and reclamation of industrial sites and nuclear power plants.Nucleco is 60%owned by Sogin and 40%by ENEA-National Agency for New Technologies.The waste characterization carried out by Nucleco SpA includes a large variety of radionuclides belonging to the gamma,beta and alpha emitter families.The determination of Uranium and Plutonium isotopes plays a key role in the waste characterization.Nucleco SpA has distinguished itself in characterizations of radioactive waste in complex and nuclear plant matrices.These matrices have large amounts of alpha emitters,in particular isotopes of Uranium,Thorium and Plutonium.A significant presence of U238 results in such a large amount of Th234(and daughters)that interferes with the determination of Pu241.Hence,there is the need of finding a pre-treatment,extraction and subsequent purification technique that would allow Th234 to be detached and thus Pu241 to be determined in complex high-activity matrices.The above elements are extracted using chromatography columns.An isotope of the element to be analyzed,with known activity,is added at the beginning of the process to determine the extraction yield.Before being eluted into the column,the sample undergoes a series of treatments in order to be purified of any interferents.The method developed by Nucleco involves the oxidation of Pu at valence+6 and the subsequent precipitation,in fluorides form,of the elements with valence+4 and+3(i.e.Th234).Pu241 is then measured by LSC(Liquid Scintillation Counting),while the other isotopes are measured by alpha spectrometry after electrodeposition on a metal plate.

中子闪烁探测器前端电子学的抗饱和改进

ICF实验会产生大量X射线和γ射线,其在光电倍增管(PMT)中产生的脉冲信号过大,导致前端电子学电路饱和,严重影响电路的正常工作和中子飞行时间的测量。结合前端电子学系统的结构,对电路饱和的原因进行了深入分析,提出了非线性抗饱和电路改进方案,并进行了仿真和实验研究。仿真结果表明,该设计方案能够大幅衰减大信号而确保小信号的通过,信号通过后电路基线能在35 ns内恢复;电路的实测结果与仿真结果基本相同。这表明:采取的方案简洁有效,能够确保输入高达数十V脉冲的情况下电路的正常工作。目前这一电路已经得到应用,并将安装在某大型激光原型的大阵列中子探测器上。

Analysis of GPS ionospheric scintillation signal amplitude fading characteristics at low latitude

The received satellite signal amplitude is attenuated greatly due to the strong ionospheric scintillation for lowlatitude regions, which causes the GPS tracking loop＇s loss of lock, the positioning errors to increase, and navigation to be interrupted. To solve the above problems, a novel signal processing algorithm is proposed based on the GPS L1 software receiver during strong ionospheric scintillation using the multi-channel intermediate frequency（IF） data sampling system. Tens of thousands of fading events are obtained based on the signal intensity measurement. The amplitude fading characteristics in the lowlatitude region are analyzed,including fading duration, time separation between fades and the numbers of signal intensity fading events. The fading thresholds are set to be 15 and 10 dB, respectively. The main fading time is very short in- 15 dB fading threshold, which generally is less than 20 ms. The main time separation between fades is less than 2 s in a single one-hour period from the time 23： 00 to 24： 00. Therefore, it has the characteristic of a short reacquisition time for the receiver designed to reduce the probability of simultaneous loss of lock for some satellites.Subsequently, the acquisition, tracking and PVT（position,velocity and time） calculations are completed by the customdesigned software receiver. The results show that the impact analysis of ionospheric scintillation on GPS amplitude attenuation in the lowlatitude region is helpful for designing the advanced tracking algorithm and to improve the robustness and accuracy of the GPS receiver.