Measurement of the high energyγ-rays from heavy ion reactions usingČerenkov detector

The energetic bremsstrahlung photons up to 100 MeV produced in heavy ion collisions can be used as a sensitive probe for short-range correlation in atomic nuclei. The energy of the γ-rays can be measured by collecting the Čerenkov light in the medium induced by the fast electrons generated in the Compton scattering or electromagnetic shower of the incident γray. Two types of detectors based on pure water and lead glass as sensitive materials were designed for this purpose. The γresponse and optical photon propagation in the detectors were simulated based on electromagnetic and optical processes in Geant4. The inherent energy resolutions of 0.022(4) + 0.51(2)∕E^(1/2)_(γ) for water and 0.0026(3) + 0.446(3)∕E^(1/2)_(γ) for lead glass were obtained. The geometry sizes of the lead glass and water were optimized to 30 cm × 30 cm × 30 cm and 60 cm × 60 cm ×120 cm, respectively, to detect high-energy γ-rays at 160 MeV. The Hough transform method was applied to reconstruct the direction of the incident γ-rays, providing the ability to experimentally distinguish the high-energy γ-rays produced in the reactions on the target from random background cosmic-ray muons.

Generation of medical isotopes ^(47)Sc,^(67)Cu through laser-induced(γ,p)reaction

Short-lived medical isotopes and their generators are typically produced in nuclear reactors and cyclotrons that require extensive facilities.However,considering the environmental concerns and economic costs of these traditional approaches,modern laser technology,which provides extremely strong electric fields within tabletop-sized areas,can serve as a potential supplementary method.Focusing specifically on the(γ,p)generation of the vital medical isotopes^(47)Sc and^(67)Cu,we used both experimental results and PIC-GEANT4 simulations to demonstrate that laser-induced photonuclear reaction is a promising method for isotope production.We developed a model capable of calculating isotope yields under various laser conditions and acceleration mechanisms.The findings revealed that a 200 TW laser can sufficiently produce diagnostic amounts of^(47)Sc and^(67)Cu,while simultaneously providing high specific activity,which is significant in medical applications for improving treatment efficacy,enhancing image resolution,and reducing side effects.

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.

Mutagenic Effect of ^(60)Co γ-rays Irradiation on Turf Characteristics of Buchloe dactyloides (Nutt.) Engelm.

[Objective] This study aimed to investigate the mutagenic effect of 60 Co γ-rays irradiation on turf characteristics of Buchloe dactyloides （Nutt.） Engelm. [Method] Buffalo grass were irradiated with 60 Co γ-rays at five different radiation intensities （1 200, 1 400, 1 600, 1 800, 2 000 Gy） to determine the related turf characteristics and analyze the mutagenic effect of 60 Co γ-rays at different radiation intensities on buffalo grass. [Result] Germination rates of buffalo grass irradiated by different radiation intensities of 60 Co γ-rays varied inconsistently, and the root length and bud length were shorter than the control; compared with the control, the height of irradiated seedlings was significantly reduced, and the number of tillers, plant height, leaf length and leaf blade width were smaller than the control; however, the stolon length, stolon diameter and number of stolon nods had no significant difference compared with the control. [Conclusion] This study laid foundation for determining the appropriate radiation intensity of 60 Co γ-rays and selecting useful mutants of buffalo grass.

Study on absorption coefficients of dual-energy γ-rays in determining phase fractions of multiphase flows

This paper discusses the principle and mathematical method to measure the phase fractions of multiphase flows by using a dual-energy gamma-ray system. The dual-energy gamma-ray device is composed of radioactive isotopes of 241Am and 137Cs with emission energies of 59.5 keV and 662 keV respectively. A rational method to calibrate the absorption coefficient was introduced in detail. The statistical error has been analyzed on the basis of the accurate absorption coefficient which enables determination phrase fractions almost independent of the flow regime. Improvement has been achieved on the measurement accuracy of phase fractions.

The Gradient of γ-Rays Irradiation’s Energy and Its Use in Treatment of Cancer Diseases

The Ionising irradiations used mostly in the treatment of tumoral diseasses are: X, γ, β and e irradiations. The discussion will be about γ irradiations, produced in linear accelerator with photon energy 6 MV and 15 MV. It is important to know the absorption performance before and after the electronic equilibrium. This is a reason that we’ve used the function of dose gradient for irradiations γ. It represents the velocity of dose change as a function of depth in tissue. From skin to maximum dose value, the increase of G-function is more accentuated for γ-rays than for β-particles while after that the G-function decreasing is less sharp for γ-rays. Finally, we’ll discuss about the advantages in terms of radiation protection of γ-rays used in radiotherapy.

A Study of Changes in the Element Composition and Structure of Surfaces under Irradiation of Dense Xenon Gas （270 bar） by y-Rays with a Maximum Energy of 10 MeV

A high-pressure chamber filled with natural xenon （XeHPC） under initial pressure 270 bar was irradiated during 43 hours by braking γ-rays with a maximum energy of 10 MeV at the MT-25 electron accelerator at an average beam intensity of 20-22 μA. After about 14 hours of irradiation, the pressure in the XeHPC dropped to 185 bar and did not change till the end of the irradiation cycle. Upon completion of exposure, part of the gas from XeHPC was bypassed into a separate reservoir to measure the xenon composition by mass-analyzer QMA-200. After the opening of the XeHPC, an inner assembly without xenon was fixed at the Ge-detector for measurement of γ-spectra of radionuclides produced in the XeHPC and the background during 15 hours. A visual inspection of the inner assembly indicated that the surfaces of its elements were covered with a siskin green layer. Using SEM （scanning electron microscopy） studies and MPRA （microprobe roentgen analysis） , the element compositions of the synthesized micro-objects and micro-particles were determined. In order to explain the observed anomalies in the formation of new elements in the micro-particles and micro-objects, nuclear fission and synthesis reactions should be used.

Dense positrons and γ-rays generation by lasers interacting with convex target

We use quantum electrodynamics particle-in-cell simulation to study the generation of dense electron–positron plasma and strongγ-ray bursts in counter-propagating laser beam interactions with two different solid targets,i.e.planar(type I)and convex(type II).We find that type II limits fast electron flow most effectively.while the photon density is increased by about an order of magnitude and energy by approx.10%–20%compared with those in type I target.γ-photon source with an ultrahigh peak brilliance of 2?×?1025 photons/s/mm2/mrad2/0.1%BW is generated by nonlinear Compton scattering process.Furthermore,use of type II target increases the positron density and energy by 3 times and 32%respectively,compared with those in type I target.In addition,the conversion efficiencies of total laser energy toγ-rays and positrons of type II are improved by 13.2%and 9.86%compared with type I.Such improvements in conversion efficiency and positron density are envisaged to have practical applications in experimental field.

X and γ-rays emission probabilities of ^(131)I and ^(133)Xe

Radioactive nuclides as 131I and 133Xe are increasingly used for both clinical diagnosis and therapeutic treatment of the patient. For example, 131I is used for the treatment of thyroid gland cancer. Otherwise, 133Xe is used in ventilation studies to assess and evaluate pulmonary function and to provide images of the lungs in both cardiac and pulmonary diseases, such as asthma, pulmonary emphysema, bronchiectasis, carcinoma of the lung, and pulmonary embolism [1,2]. Furthermore, cerebral blood flow is measured using 133Xe inhalation. In this study, the X and γ-rays emission probabilities in the decay of 131I and 133Xe were precisely measured with a calibrated Si(Li) detector. Results of this study were compared using available results in the literature. Good agreement was observed between our results and available results in the literature.

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.

Optimization method of Hadamard coding plate inγ‑ray computational ghost imaging

Owing to the constraints on the fabrication ofγ-ray coding plates with many pixels,few studies have been carried out onγ-ray computational ghost imaging.Thus,the development of coding plates with fewer pixels is essential to achieveγ-ray computational ghost imaging.Based on the regional similarity between Hadamard subcoding plates,this study presents an optimization method to reduce the number of pixels of Hadamard coding plates.First,a moving distance matrix was obtained to describe the regional similarity quantitatively.Second,based on the matrix,we used two ant colony optimization arrangement algorithms to maximize the reuse of pixels in the regional similarity area and obtain new compressed coding plates.With full sampling,these two algorithms improved the pixel utilization of the coding plate,and the compression ratio values were 54.2%and 58.9%,respectively.In addition,three undersampled sequences(the Harr,Russian dolls,and cake-cutting sequences)with different sampling rates were tested and discussed.With different sampling rates,our method reduced the number of pixels of all three sequences,especially for the Russian dolls and cake-cutting sequences.Therefore,our method can reduce the number of pixels,manufacturing cost,and difficulty of the coding plate,which is beneficial for the implementation and application ofγ-ray computational ghost imaging.

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.

测量输油管道石蜡模拟油垢厚度的标定实验初探

采用Na(Tl)闪烁谱仪用两种方法测量了平均能量为1.25MeV的60Co的γ射线在石蜡样品中发生康普顿散射的散射系数。在完全相同的实验条件下,利用此散射系数标定石蜡模拟油垢厚度,其结果最好一组平均相对误差在1.29%左右。

N^+束和γ射线对两种微生物生物膜辐射损伤效应的比较研究

以 N+ 束和 60 Coγ-ray为辐射源 ,以耐辐射异常微球菌 ( Deinococcusradiodurans)和 E.coli为试材 ,对两种辐射源作用于两种微生物膜所产生的辐射损伤效应作了比较研究。结果表明 ,两种辐射源作用于两种微生物所导致的生物膜脂过氧化程度、所生成的膜脂过氧化产物丙二醛 ( MDA)的含量及表示生物膜透性的电解质渗透率均随着辐照剂量的增大而提高 ;与 D.radiodurans相比 ,两种辐射源作用于 E.coli的膜脂过氧化程度和相对透性更强些。扫描电镜 ( SEM)观察发现 ,N+ 束可直接导致生物膜的损伤 ,而γ-ray辐照则看不出直接的损伤效应。

Study on γ-Ray Irradiation Mutation of Bacillus subtilis NCD-2

[Objective] To study the effect of 60Co γ-rays irradiation on Botrytis cinerea biocontrol strains—Bacillus subtilis NCD-2. [Method] NCD-2 cells were irradiated at different doses of γ-rays from 100 to 2 000 Gy. The strains were screened by plate confrontation method and Oxford cup diffusion. [Result] The curves of the relationship of irradiation dose and mutation and lethal rate were obtained. The results showed that lethal rate increased with the increasing of irradiation dose. The lethal rate of 1 000 Gy irradiation dose reached 99.50%. The mutation rate increased below 500 Gy and decreased above 500 Gy. The highest mutation rate occurred when the irradiation dose was between 400 and 700 Gy, and the average mutation rate was above 15%. The optimal irradiation dose was 500 Gy, when the average mutation rate was 26.51% and lethal rate was 77.71%. [Conclusion] This study provided references for γ-rays irradiation mutation of Bacillus subtilis.

γ射线辐照改性聚碳硅烷提高热解陶瓷产率

在N2气中用γ射线对聚碳硅烷(Polycarbosilane,PCS)进行辐照,利用傅里叶红外光谱分析、凝胶渗透色谱分析和热重分析等手段研究了不同吸收剂量下PCS的化学结构、分子量和热分解特性。结果显示,经γ射线辐照处理后的PCS轻微失重,分子量和软化点随着吸收剂量的增加而增加,说明PCS经辐照后发生了分子间的交联反应。红外分析表明,PCS的交联主要是通过Si-H键和C-H键的断裂产生新的Si-C-Si结构实现的。热重分析表明,PCS热解为碳化硅的陶瓷产率随吸收剂量的增加显著升高,剂量达到1.5 MGy后PCS样品的陶瓷产率基本提高到稳定值,此时,陶瓷产率从改性前的61.9%提高到80.0%。

SRAP Marker Analysis of Genomic Mutation Induced by ^(60)Coγ-Ray Irradiation in Potato (Solanum tuberosum)

[Objective] This study was to explore the mutagenic effect of 60Co γ-ray on Solanum tuberosum chromosomes.[Method] The 60Co γ-ray at different irradiation doses was applied to treat the minitubers of potato variety ＇Favorita＇,and the genomic mutations in VM1 and VM2 gene rations in treatments with different doses were analyzed by SRAP markers.[Resalt] Thirty pairs of SRAP primers out of 88 pairs exhibited polymorphism with a rate of 34.1％ in the bulked selection of VM1 generation.A total of 225 bands were obtained,of which 64 were polymorphic with a rate of 28.4％.The polymorphism was reflected in the forms of deleted bands and added bands.Based on the result of the bulked selection of VM1 generation,25 primers with polymorphism were selected to scan VM2 generation.Five primers performed poorly,and nine of the rest 20 pairs revealed polymorphism and obtained nine polymorphic bands,of which only four bands were detected in VM1 generation and the other five ones were newly deleted bands.Only 9.8％ of the bands detected in VM1 generation were obtained in VM2 generation.Eventually,nine stable and dear polymorphic bands were recovered and cloned,and DNA sequences of six bands of them were acquired by sequencing.According to the comparative analysis,five fragments sequences were similar to potato chromosome with a similarity rate of 77％-89％,three of them located at the resistance gene cluster; another one fragment had a similarity of 93％ with some regions of the No.5 chromosome in tomato.[Conclusion] 60Co γ-ray irradiation can cause mutation of genomic DNA in potato;there is no significant correlation between the number of polymorphic bands and the irradiation dose; potymorphic bands are characterized by a larger number of deleted bands than that of the added ones.

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。

Bi2O3和WO3纳米粒子协同增强NR/WO3/Bi2O3复合材料γ射线屏蔽性能

以相同质量分数(30%)而不同比例的WO_3和Bi_2O_3纳米粒子分别填充至天然橡胶(NR)并制备出各自的复合材料。结果表明,经双子季铵盐(GQA)改性球磨后的WO_3和Bi_2O_3粒子尺寸达到纳米级,并在其表面嫁接上有机活性官能团;与纯NR材料相比,复合材料的拉伸强度均提升2倍以上;当WO_3和Bi_2O_3纳米粒子质量比为15∶15时,复合材料的γ-ray的屏蔽率由各自单独填充时的8.3%和9.2%提高至12%。WO_3和Bi_2O_3纳米粒子量子效应、表面效应以及在NR基体中的均匀分散是协同增强复合材料对γ-ray防护性能及力学性能的关键。

^(60)Co-γRay射线诱变水稻突变体的分离和遗传学初步分析

为了研究水稻发育的分子机制,我们利用γ射线对粳稻品种9522进行诱变,共诱变了3 000 g种子,M1代单株收种,M2代移栽5 963个株系于上海农科院.在M2代中筛选突变体,并在M3代中复选,最终得到了叶、株型育性等各类形态突变体666份.对其中162株突变体进行了遗传分析,有53.61%的突变体出现3∶1的分离,这些突变体是隐性的单位点突变.同时,这些突变体的分离也为水稻功能基因分离和功能鉴定等研究打下了良好的基础,并为水稻发育的研究提供了宝贵的材料.