Artificial neural network-based method for discriminating Compton scattering events in high-purity germaniumγ-ray spectrometer

To detect radioactive substances with low activity levels,an anticoincidence detector and a high-purity germanium(HPGe)detector are typically used simultaneously to suppress Compton scattering background,thereby resulting in an extremely low detection limit and improving the measurement accuracy.However,the complex and expensive hardware required does not facilitate the application or promotion of this method.Thus,a method is proposed in this study to discriminate the digital waveform of pulse signals output using an HPGe detector,whereby Compton scattering background is suppressed and a low minimum detectable activity(MDA)is achieved without using an expensive and complex anticoincidence detector and device.The electric-field-strength and energy-deposition distributions of the detector are simulated to determine the relationship between pulse shape and energy-deposition location,as well as the characteristics of energy-deposition distributions for fulland partial-energy deposition events.This relationship is used to develop a pulse-shape-discrimination algorithm based on an artificial neural network for pulse-feature identification.To accurately determine the relationship between the deposited energy of gamma(γ)rays in the detector and the deposition location,we extract four shape parameters from the pulse signals output by the detector.Machine learning is used to input the four shape parameters into the detector.Subsequently,the pulse signals are identified and classified to discriminate between partial-and full-energy deposition events.Some partial-energy deposition events are removed to suppress Compton scattering.The proposed method effectively decreases the MDA of an HPGeγ-energy dispersive spectrometer.Test results show that the Compton suppression factors for energy spectra obtained from measurements on ^(152)Eu,^(137)Cs,and ^(60)Co radioactive sources are 1.13(344 keV),1.11(662 keV),and 1.08(1332 keV),respectively,and that the corresponding MDAs are 1.4%,5.3%,and 21.6%lower,respectively.

Generalization ability of a CNNγ-ray localization model for radiation imaging

Inγ-ray imaging,localization of theγ-ray interaction in the scintillator is critical.Convolutional neural network(CNN)techniques are highly promising for improvingγ-ray localization.Our study evaluated the generalization capabilities of a CNN localization model with respect to theγ-ray energy and thickness of the crystal.The model maintained a high positional linearity(PL)and spatial resolution for ray energies between 59 and 1460 keV.The PL at the incident surface of the detector was 0.99,and the resolution of the central incident point source ranged between 0.52 and 1.19 mm.In modified uniform redundant array(MURA)imaging systems using a thick crystal,the CNNγ-ray localization model significantly improved the useful field-of-view(UFOV)from 60.32 to 93.44%compared to the classical centroid localization methods.Additionally,the signal-to-noise ratio of the reconstructed images increased from 0.95 to 5.63.

Study on Color Information Degradation Induced byγ-ray Radiation in CMOS Cameras

Theγ-rays are widely and abundantly present in strong nuclear radiation environments,and when they act on the camera equipment used to obtain environmental visual information on nuclear robots,radiation effects will occur,which will degrade the performance of the camera system,reduce the imaging quality,and even cause catastrophic consequences.Color reducibility is an important index for evaluating the imaging quality of color camera,but its degradation mechanism in a nuclear radiation environment is still unclear.In this paper,theγ-ray irradiation experiments of CMOS cameras were carried out to analyse the degradation law of the camera’s color reducibility with cumulative irradiation and reveal the degradation mechanism of the color information of the CMOS camera underγ-ray irradiation.The results show that the spectral response of CMOS image sensor(CIS)and the spectral transmittance of lens after irradiation affect the values of a^(*)and b^(*)in the LAB color model.While the full well capacity(FWC)of CIS and transmittance of lens affect the value of L^(*)in the LAB color model,thus increase color difference and reduce brightness,the combined effect of color difference and brightness degradation will reduce the color reducibility of CMOS cameras.Therefore,the degradation of the color information of the CMOS camera afterγ-ray irradiation mainly comes from the changes in the FWC and spectral response of CIS,and the spectral transmittance of lens.

费米耀变体的多波段γ-ray辐射

从Fermi/LAT第3期源表(3FGL)中选取了920个Blazar样本,包含414个平谱射电源(Flat Spectrum Radio Quasar,FSRQ)和506个蝎虎天体(BL Lac object,BL Lac),其中有226个HBL,140个IBL和140个LBL.研究了所有Blazar样本及其子类FSRQ,BL Lac,HBL和LBL样本的射电1.4 GHz光度分别与γ-ray在0.1,0.3,1,3及10 GeV处光度之间的相关性。结果表明:对总样本及所有子类样本,1.4 GHz光度与γ-ray各频率处的光度均存在强的正相关性,但对于不同的子类样本,这种相关性随γ-ray频率的变化趋势不同;BL Lac的相关性好于FSRQ,而HBL的相关性与LBL相似。总的来说,随着γ-ray辐射频率的增加,相关性有减弱的趋势。但是,对于不同的样本,相关性随γ-ray频率增加有不同的变化趋势。因此,同一频率下不同子类Blazar的γ-ray辐射机制存在差异,同一样本在不同频率下的γ-ray辐射机制也有差异.在γ-ray辐射中,BL Lac的辐射来自同步自康普顿(SSC)过程的成分比FSRQ的多,而HBL的与LBL的相似.FSRQ的γ-ray辐射机制比BL Lac更为复杂。

电子束和γ-ray对UHMWPE纤维的辐照效应对比研究

γ-ray和电子束是高能辐照源,高能射线不仅可以处理被加工物表面,同时可深入其内部,且工艺控制简单,可进行常温或者低温加工,具有节能、无环境污染等特点.分别采用γ-ray和电子束辐照超高相对分子质量聚乙烯(UHMWPE)纤维,采用电子自旋共振(ESR)、红外光谱(IR)、差示扫描量热法(DSC)、X射线衍射(XRD)、扫描电镜(SEM)、凝胶含量和拉伸实验等表征手段对不同的辐照效应进行研究,旨在改善纤维表面惰性,探索合理使用两种辐射源辐照改性材料的适用范畴,为更好地利用辐照技术对UHMWPE纤维表面改性提供理论依据.

γ-Ray Irradiation-Derived MnO/rGO Composites for High Performance Lithium Ion Batteries

We report a γ-ray irradiation reduction method to prepare MnO/reduced graphene oxide （rCO） nanocomposite for the anode of lithium ion batteries. γ-Ray irradiation provides a clean way to generate homogeneously dispersed MnO nanoparticles with finely tuned size on rGO surface without the use of surfactant. The MnO/rGO composite enables a fully charge/discharge in 2 min to gain a reversible specific capacity of 546 （mA-h）/g which is 45 higher than the theoretical value of commercial graphite anode.

Similar therapeutic effects of ^(125I) seed radiotherapy andγ-ray radiotherapy on lacrimal gland adenoid cystic carcinoma

AIM:To evaluate the survival outcomes of patients with lacrimal gland adenoid cystic carcinoma who underwent eye-sparing surgery combined with ^(125I)seed implantation radiotherapy or local externalγ-ray radiotherapy.METHODS:In this retrospective comparative case series,the clinical records of 27 primary and 8 recurrent patients were reviewed.Univariate and multivariate analyses were used to identify risk factors associated with distant metastasis(DM),and the overall survival(OS)after the initial surgery was analyzed.RESULTS:The median follow-up after radiotherapy was 36 mo(range 6-120 mo).At the last follow-up after radiotherapy,26(74.3%)patients had no evidence of disease,7(20%)patients had DM,2(5.9%)patients died of DM,and 1 patient with DM was lost to follow-up.Univariate analyses showed that duration of symptoms,bone destruction,T stage classification,and wide excision surgery were risk factors influencing DM(P<0.05).The 5-year and 10-year OS rates after the initial surgery were 95.8%and 79.9%,respectively.The 5-year DM-free survival and disease-free survival rates after radiotherapy were 66.4%and 52.7%,respectively.CONCLUSION:^(125I)seed radiotherapy and local externalγ-ray radiotherapy may have similar therapeutic effects in preventing DM.Patients with T1/T2 stage disease have a better prognosis than those with T3/T4 stage disease.

Methods for obtaining characteristic γ-ray net peak count from interlaced overlap peak in HPGe γ-ray spectrometer system

For a characteristic c-ray with interlaced overlap peak, and the case where its reliable and credible net count cannot be obtained using the current high-purity germanium(HPGe) multichannel γ-ray spectrum software, two new methods are proposed herein to obtain the γ-ray net peak count from the interlaced overlap peak in the HPGe cray spectrometer system, of which one is the symmetric conversion method based on Gaussian distribution and the other is where the energy average value of two close γ-rays is regarded as the γ-ray energy. The experimental results indicate that the two methods mentioned above are reliable and credible. This study is significant for the development of better γ-ray spectrum processing software for measuring complex γ-ray spectra concerning the nuclear reaction cross section, neutron activation analysis, and analysis of transuranium elements, using an HPGe detector.

Electrical,thermal and electrochemical properties of γ-ray-reduced graphene oxide

The properties of γ-ray-reduced graphene oxide samples(GRGOs)were compared with those of hydrazine hydrate-reduced graphene oxide(HRGO).Fourier transform infrared spectroscopy,X-ray diffractometry,Raman spectroscopy,Brunauer-Emmett-Teller surface area analysis,thermogravimetric analysis,electrometry,and cyclic voltammetry were carried out to verify the reduction process,structural changes,and defects of the samples,as well as to measure their thermal,electrical,and electrochemical properties.Irradiation with γ-rays distorted the structure of GRGOs and generated massive defects through the extensive formation of new smaller sp^(2)-hybridized domains compared with those of HRGO.The thermal stability of GRGOs was higher than that of HRGO,indicating the highly efficient removal of thermally-labile oxygen species by γ-rays.RRGO prepared at 80 kGy showed a pseudocapacitive behavior comparable with the electrical double-layer capacitance behavior of HRGO.Interestingly,the specific capacitance of GRGO was enhanced by nearly three times compared with that of HRGO.These results reflect the advantages of radiation reduction in energy storage applications.

Study on γ-ray source from the resonant reaction ^19F(p,αγ)^16O at Ep=340 keV

High energyγ-ray can be used in many fields,such as nuclear resonant fluorescence,nuclear medicine imaging.One of the methods to generate high-energyγ-ray is nuclear resonant reaction.The 19F(p,αγ)16O reaction was used to generate 6.13-MeVγ-ray in this work.The angular distribution of 6.13-MeVγ-ray was measured by six LaBr3 detectors.The thick-target yield curve of 6.13-MeVγ-ray had been measured.The maximum yield was determined to be(1.85±0.01)×10^-8γ/proton,which was measured by HPGe detector and LaBr3 detector.The absolute efficiency of all the detectors was calibrated using 60Co and 27Al(p,γ)^28Si reaction at Ep=992 keV.The cross section and total resonant width of the reaction were determined to be 95.1±1.0 mb(1 b=10^-24 cm^2)andΓCM=2.21±0.22 keV,respectively.

Photo-transmutation based on resonance γ-ray source

High intensity γ-ray source can be obtained through resonance reaction induced by protons. In this work, the possibility of using such high intensity MeV-range γ-ray source to transmute nuclear waste is investigated through Mont Carlo simulation.197 Au(γ, n)196Au experiment is performed to obtain the transmutation rate and compared with the simulation result. If the current of the proton beam is 10 mA at the resonance energy of 441 keV, with the γ photons emitted from7 Li(p, γ)8 Be, then the corresponding transmutation yield for129I in 2π direction can reach 9.4 × 109 per hour. The result is compared with that of LCS γ-ray source.

γ-Ray radiolysis of acetohydroxamic acid in HNO_3 and its radiolytic product

Acetohydroxamic acid(AHA) is a novel saltfree reagent used for the separation of Pu and Np from U in the advanced Purex process. This paper reports the c-ray damage of AHA in HNO_3 and its radiolytic product. For 0.2 mol L^(-1) AHA in 0.2–2.0 mol L^(-1) HNO_3 irradiated at a dose of 5–25 kGy, the radiolytic rate of AHA is6.63–77.5%, and it increases with the HNO_3 concentration and absorbed dose. The main radiolytic gases are N_2O and H_2, with volume fractions of(0.500–16.2) 9 10^(-2) and(1.30–11.8) 9 10^(-3), respectively, and they increase with the absorbed dose; the H_2 volume fraction decreases with increasing HNO_3 concentration. The main liquid radiolytic products are CH_3 COOH and HNO_2, and their concentrations are(3.40–19.7) 9 10^(-2) and(0.200–4.80) 9 10^(-3)-mol L^(-1), respectively, which increase with the HNO_3 concentration. Since a significant concentration of HNO_2 is present in the irradiated AHA-HNO_3 solution, a holding reductant must be used to destroy HNO_2 and stabilize Pu(Ⅲ) and Np(Ⅴ) when AHA is applied for the separation of Pu and Np from U.

Photoactivation experiment of 197Au（γ, n） performed with 9.17-MeV γ-ray from 13C（p, γ）14N

High energy γ-ray can be used for nuclear waste transmutation by using the giant dipole resonance(GDR). The photonuclear reaction 197Au(γ, n) is known as a standard for studies on photoactivation experiments. The previous experiments on 197Au(γ, n) have been performed with bremsstrahlung, positron annihilation in flight or laser Compton scattering γ-ray.In this work, a new mono-energetic γ-ray source based on 13C(p,γ)^14N reaction is used to measure the cross section of 197Au(γ, n) and the measured value is compared with the results obtained with other ways.

High density γ-ray emission and dense positron production via multi-laser driven circular target

A diamond-like carbon circular target is proposed to improve γ-ray emission and pair production with a laser intensity of 8×1022 W cm-2by using 2D particle-in-cell simulations with quantum electrodynamics.It is found that the circular target can enhance the density of γ-photons significantly more than a plane target, when two colliding circularly polarized lasers irradiate the target.By multi-laser irradiating the circular target, the optical trap of lasers can prevent the high energy electrons accelerated by laser radiation pressure from escaping.Hence, γ-photons with a high density of beyond 5000 ncare obtained through nonlinear Compton backscattering.Meanwhile, 2.7×1011 positrons with an average energy of 230 MeV are achieved via the multiphoton Breit-Wheeler process.Such an ultrabright γ-ray source and dense positron source can be useful in many applications.The optimal target radius and laser mismatching deviation parameters are also discussed in detail.

Ultrabright γ-ray emission from the interaction of an intense laser pulse with a near-critical-density plasma

An efficient scheme for generating ultrabright γ-rays from the interaction of an intense laser pulse with a near-criticaldensity plasma is studied by using the two-dimensional particle-in-cell simulation including quantum electrodynamic effects.We investigate the effects of target shape on γ-ray generation efficiency using three configurations of the solid foils attached behind the near-critical-density plasma:a flat foil without a channel(target 1),a flat foil with a channel(target 2),and a convex foil with a channel(target 3).When an intense laser propagates in a near-critical-density plasma,a large number of electrons are trapped and accelerated to GeV energy,and emit γ-rays via nonlinear betatron oscillation in the first stage.In the second stage,the accelerated electrons collide with the laser pulse reflected from the foil and emit high-energy,high-density γ-rays via nonlinear Compton scattering.The simulation results show that compared with the other two targets,target 3 affords better focusing of the laser field and electrons,which decreases the divergence angle of g-photons.Consequently,denser and brighter γ-rays are emitted when target 3 is used.Specifically,a dense γ-ray pulse with a peak brightness of 4.6×10^(26) photons/s/mm2/mrad2/0.1%BW(at 100 MeV)and 1.8×1023 photons/s/mm2/mrad2/0.1%BW(at 2 GeV)are obtained at a laser intensity of 8.5×10^(22) W/cm2 when the plasma density is equal to the critical plasma density nc.In addition,for target 3,the effects of plasma channel length,foil curvature radius,laser polarization,and laser intensity on the γ-ray emission are discussed,and optimal values based on a series of simulations are proposed.

Preparation of Thermal-responsive Chitosan-graft-N-isopropyl- acrylamide Membranes via γ-Ray Irradiation

A novel thermo-sensitive switching membrane has been prepared by radiation-induced simultaneous grafting N-isopropylacrylamide （NIPAAm） onto chitosan membrane. Fourier transform infrared spectroscopy （FTIR） was used to identify the structure of the grafted membranes. The surface morphology of the grafted membrane was observed from scanning electron microscopy （SEM）. Pure water flux measurements showed that water flux of the grafted membrane decreased with the increase of temperature, while that of chitosan membrane was constant. It was proved that grafted membrane was sensitive to temperature.

Novel Method of Preparation of Monolithic Columns for Fast Separation byγ-Ray Irradiation

A porous monolithic sol-gel column with the solution of methacryloxypropyltrimethoxysilane in toluene with an acid catalyst was prepared in the presence and absence of sodium dodecyl sulfate. In situ polymerization was carded out by γ-ray irradiation within the capillary. The γ-radiation-initiated synthesis could generate radicals directly on the monomer avoiding use of any initiator. The chromatographic behavior of the capillary monolithic columns were studied in the modes of CEC, p-CEC and low pressure-driven separation, all the tests exhibited reversed-phase character. It provided a viable alternative to either thermally initiated or photo polymerization method for the preparation of monolithic columns.

Brightγ-ray source with large orbital angular momentum from the laser near-criticalplasma interaction

We propose a new laser-plasma-based method to generate brightγ-rays carrying large orbital angular momentum by interacting a circularly polarized Laguerre–Gaussian laser pulse with a near-critical hydrogen plasma conflned in an over-dense solid tube.In the flrst stage of the interaction,it is found via fully relativistic three-dimensional particle-in-cell simulations that high-energy helical electron beams with large orbital angular momentum are generated.In the second stage,this electron beam interacts with the laser pulse reflected from the plasma disc behind the solid tube,and helicalγbeams are generated with the same topological structure as the electron beams.The results show that the electrons receive angular momentum from the drive laser,which can be further transferred to theγphotons during the interaction.Theγbeam orbital angular momentum is strongly dependent on the laser topological charge l and laser intensity a_(0),which scales as L_(γ)∝a_(0)~4.A short(duration of 5 fs)isolated helicalγbeam with an angular momentum of-3.3×10^(-14)kg m~2 s^(-1)is generated using the Laguerre–Gaussian laser pulse with l=2.The peak brightness of the helicalγbeam reaches 1.22×10^(24)photons s^(-1)mm^(-2)mrad^(-2)per 0.1%BW(at 10 Me V),and the laser-to-γ-ray angular momentum conversion rate is approximately 2.1%.

The effect ofγ-ray irradiation on the SOT magnetic films and Hall devices

Magnetoresistive random access memories(MRAMs)have drawn the attention of radiation researchers due to their potential high radiation tolerance.In particular,spin-orbit torque MRAM(SOT-MRAM)has the best performance on endurance and access speed,which is considered to be one of the candidates to replace SRAM for space application.However,little attention has been given to theγ-ray irradiation effect on the SOT-MRAM device yet.Here,we report the Co-60 irradiation results for both SOT(spin-orbit torque)magnetic films and SOT-Hall devices with the same stacks.The properties of magnetic films are not affected by radiation even with an accumulated dose up to 300 krad(Si)while the magnetoelectronic properties of SOTHall devices exhibit a reversible change behavior during the radiation.We propose a non-equilibrium anomalous Hall effect model to understand the phenomenon.Achieved results and proposed analysis in this work can be used for the material and structure design of memory cell in radiation-hardened SOT-MRAM.

Stabilization of Aqueous Graphene Oxide with Acetone under γ-Ray/UV

Graphene oxide(GO)is a kind of water soluble two-dimensional materials containing a large amount of oxygen-containing groups which infuse GO with water solubility,biocompatibility and functionality,etc.But GO can be easily reduced by losing oxygen-containing groups under some circumstances such as irradiation of-ray or ultraviolet(UV).In this work,we found that acetone can significantly slow down the reduction process of GO under the irradiation of either-ray or UV,which was supported by analysis results with UV-visible(UV-Vis)absorption spectra,X-ray photoelectron spectroscopy,etc.Acetone can capture and remove strongly reducible hydrated electrons generated under-irradiation.GO reduction by UV also involves electron transfer process which can be affected by the presence of acetone.Hence,acetone can be used to stabilize,adjust the radiation reduction process of GO.This would be interesting not only in radiation and radiation protection,but also in understanding the redox properties of GO.