脉冲γ射线对光纤的辐射效应

介绍了光纤的损耗机制和γ射线对光纤的辐射效应,设计了针对脉冲γ射线作用于光纤而产生辐射感生损耗的实验测量系统。利用平均光子能量为0.3 MeV、脉冲宽度25 ns、剂量率2.03×107Gy.s-1,和平均光子能量为1.0 MeV、脉冲宽度25 ns、剂量率5.32×109Gy.s-1的2种脉冲γ射线分别作用于多模和单模光纤,分别采用波长为405,660,850,1 310和1 550 nm的激光光纤传输系统对辐射感生损耗进行了测量。获得了光纤辐射感生损耗和辐射剂量的关系,并对实验结果进行分析。从实验结果可以看出:在近红外到可见光范围内,脉冲γ射线对光纤作用产生的辐射感生损耗随探测波长减小而增大;在0.1~3.5 Gy剂量范围内,多模光纤辐射感生损耗和辐射剂量呈线性关系。分析辐射对光纤的作用机制和实验结果后得出:光纤基质原子的电子能级对传输光子的共振吸收而造成吸收损耗增加;光纤折射率分布的改变从而导致波导损耗增加。     

稳态、瞬态X射线辐照引起的互补性金属-氧化物-半导体器件剂量增强效应研究

重点开展了稳态、瞬态X射线辐照引起的金属氧化物半导体(CMOS)器件剂量增强效应relative dose enhancement effect(RDEF)研究.通过实验给出辐照敏感参数随总剂量的变化关系,旨在建立CMOS器件相同累积剂量时Χ射线辐照和γ射线辐照的总剂量效应损伤等效关系.在脉冲X射线源dense plasma focus(DPF)装置上,采用双层膜结构开展瞬态翻转增强效应研究,获得了瞬态翻转剂量增强因子.这些方法为器件抗X射线辐照加固技术研究提供了实验技术手段. 关键词： X射线 剂量增强因子 总剂量效应 剂量率效应     

Evaluation of the 1077 keV γ-ray emission probability from 68Ga decay

⁶⁸Ga decays to the excited states of ⁶⁸Zn through the electron capture decay mode. New recommended values for the emission probability of 1077 keV γ-ray given by the ENSDF and DDEP databases all use data from absolute measurements. In 2011, JIANG Li-Yang deduced a new value for 1077 keV γ-ray emission probability by measuring the ⁶⁹Ga(n,2n) ⁶⁸Ga reaction cross section. The new value is about 20% lower than values obtained from previous absolute measurements and evaluations. In this paper, the discrepancies among the measurements and evaluations are analyzed carefully and the new values are re-recommended. Our recommended value for the emission probability of 1077 keV γ-ray is (2.72± 0.16)%.     

Level Scheme of High-Spin States in 145Tb

High-spin states of ¹⁴³Tb have been studied via the ¹¹⁸Sn(³²S,1p4n)¹⁴⁵Tb reaction by means of in-beam γ-ray spectroscopy. Measurements of γ-ray excitation functions and γ-γ-t coincidences were performed with 12 BGO(AC)HPGe detectors. A level scheme for ¹⁴⁵Tb including 41 γ-rays which come from the deexcitations of the 24 levels, has been established for the first time based on an analysis of the γ-ray excitation functions, γ-γ coincidence relationships, intensity balances and cross-over transitions. The spins for most of the levels in the scheme are assigned according to the results of the measured γ-ray anisotropies. Considering the structure similarity between ¹⁴³Eu and ¹⁴⁵Tb, the low-lying levels in 145Tb are interpreted by coupling a h_9/2 proton to the excited states in ¹⁴⁴Gd core.     

New Neutron-Rich Nuclide 185Hf

New neutron-rich nuclide ¹⁸⁵Hf has been identified for the first time.The ¹⁸⁵Hf was produced via the ¹⁸⁶W(n,2p)¹⁸⁵Hf reaction by 14MeV neutron irradiation of natural metallic tungsten powder and separated by radiochemical methods.The identification of ¹⁸⁵Hf was based on the observation of decay γ-ray of its daughter ¹⁸⁵Ta.A half-life of 3.5±0.6min was determined for ¹⁸⁵Hf by fitting the measured growth and decay curve of the 177.59keV γ-ray which is the strongest decay γ-ray of ¹⁸⁵Ta.In addition,a new γ-ray of 164.5±0.5keV was found and assigned to ¹⁸⁵Hf.     

High-Spin Level Scheme of Odd-Odd 140Pr Nucleus

High spin level structure of doubly odd nucleus ¹⁴⁰Pr has been investigated using in beam γ spectroscopy techniques by means of the ¹³⁰Te(¹⁴N,4n)¹⁴⁰Pr reaction at beam energy of 58MeV.γ-ray excitation functions,γ-ray singles and γ-γ-t coincidences were measured experimentally.The level scheme of ¹⁴⁰Pr,including 27 new levels and 42 new γ-rays,was established for the first time up to 4717.3keV in excitation energy.Based on the measured γ-ray anisotropies,spin values were suggested to the levels in ¹⁴⁰Pr.Several quasiparticle configurations are discussed on the basis of systematics in the neighboring odd odd nuclei,and interpreted qualitatively.     

用于脉冲γ强度测量的φ60,1000μm PIN探测器

采用电阻率为10000—20000 Ω·cm的高阻单晶硅材料，研制成功灵敏区尺寸为φ60 mm，耗尽层厚度～1000　μm的大面积厚PIN半导体探测器.设计了该类探测器厚度测量专用的反冲质子测量系统，对探测器的时间响应、γ灵敏度、漏电流、γ/n分辨等物理参数进行了测量和分析，结果表明，这类探测器可满足低强度裂变n/γ混合场中脉冲γ强度测量的需要. 关键词： 大面积 电流型 半导体探测器     

γ射线电离辐射对商用CMOS APS性能参数的影响

研究了γ射线电离辐射效应对商用CMOS有源像素传感器(APS)性能参数的影响,着重分析了量子效率、转换增益、暗电流、坏点和脉冲颗粒噪声等参数。研究结果表明:当受到1 000 Gy辐射后,APS失去工作能力,无信号输出或像素灰度值仅为0,110,255 DN。60Coγ射线的离位截面约为10-25cm2(0.1 b)。当剂量率低于58.3 Gy/h且辐照时间较短时,辐射对量子效率及转换增益无影响,坏点产生数为0,总剂量效应使3T-APS的本底噪声升高到4.62 DN但对4T PPD APS几乎无影响。脉冲颗粒噪声引起的各灰度值像素数量分布呈泊松分布,并与剂量率正相关。     

High-Spin Level Scheme of Odd-odd 142Pm

The level structure of doubly odd nucleus ¹⁴²Pm has been studied via the ¹²⁸Te(¹⁹F,5nγ)¹⁴²Pm reaction in the energy region from 75 to 95MeV. In-beam γ rays were measureed including the excited function, γ-ray singles and γ-γ coincidences in experiment. The level scheme of ¹⁴²Pm has been extended up to excitation energy of 7030.0keV including 25 new γ rays and 13 new levels. Based on the measured γ-ray anisotropies, the level spins in ¹⁴²Pm have been suggested.     

Identification of Excited States in 117Xe

Excited states of ¹¹⁷Xe were populated via the reaction ⁹²Mo(²⁸Si,2pn)at 115MeV.The emitted promt γ-rays were measured by using in beam γ-ray experimental techniques.Five bands in ¹¹⁷Xe have been identified,two of them are observed for the first time,and the three known bands are extended to higher spins.     

A New Heavy Neutron-rich Isotope 238Th

A new nuclide ²³⁸Th has been produced via multinucleon transfer reaction induced by 60MeV/u ¹⁸O ion irradiation of natural uranium. The thorium was radiochemically separated from the mixture of uranium and its reaction products. The activity of thorium was measured by using a HPGe detector and a planar HPGe detector. The ²³⁸Th has been identified for the first time by measuring the growth and decay of the γ-rays from its daughter ²³⁸Pa. The half-life of 238Th was determined to be (9.4±2.0)min. In addition,a new (89.0±0.3)keV γ-ray with T_1/2=(8.9±1.5)min was observed and assigned to ²³⁸Th decay based on the measurement of transition energy and half life.     

Depth Dose Distribution for 252Cf Source Using Solid State Detectors

LiF (600 and 700) and plastic detector were used for measuring fast and thermal neutrons and γ-ray doses from ²⁵²Cf source in tissue equivalent phantom. Conversion factors as well as related quality factors were used for absorbed and equivalent dose calculations. Two exposure positions were used: source at 30 cm and in contact with phatnom surface. The contribution of thermal and fast neutrons in both absorbed dose and equivalent dose reaches a maximum value at 3.5 cm while the maximum for γ-ray is at 8.5 cm. The build up and attenuation in tissue and the corresponding relaxation length were evaluated.     

Experimental Study of High-Spin Band Structures of 183Au

High-spin states in ¹⁸³Au have been studied experimentally using heavy-ion-induced fusion-evaporation reaction and standard in-beam γ-ray spectroscopic techniques. The level scheme of ¹⁸³Au was revised and extended. A rotational band proposed as the unfavored signature branch of the πi_13/2 band has been observed for the first time. Interaction properties between the two negative-signature bands of the πh_9/2-πf^7/2 system have been discussed for the light odd-A Au nuclei.     

BaF2 Scintillator Coupling with a Low-pressure Multistep Avalanche Chamber

We studied the properties of a UV light sensitive low-pressure multistep avalanche chamber containing pure TMAE vapour.The gain of two chambers with different constructure at various temperatures is measured.With pure TMAE vapour at 40°C the gain of one chamber was 4×10⁵,the time resolution was 4.1ns.Coupling the chamber with a 2×2×2.4cm³ BaF₂ scintillator we successfully observed the signal of ¹³⁷Cs γ-ray of 0.661MeV.     

Effect of Rotation on Transition Energies and M1 Transitions in Superdeformed Nuclei

Using triaxial-particle-rotor model, a strong perturbation effect of rotation on transition energies and M1 transitions is investigated. The γ-transition energies,B(M1) -values and n γ-ray intensity are given. The M1 tranSitions between signature partner bands in the ¹⁹⁵T1 nucleus may proceed mainly through internal conversion electrons.     

大规模集成电路中子和γ射线综合电离辐照效应研究

 研究了反应堆中子和γ射线综合辐照环境下CMOS工艺大规模集成电路的电离辐照效应。通过对80C196KC20和PSD501B1两种不同芯片在该环境下开展综合辐照试验,发现总的静态电流增长不明显。对试验结果综合分析得出：在反应堆的综合辐照环境下,中子电离效应较弱,并且由于中子位移效应引起载流子迁移率降低和载流子浓度降低,使得总的静态电流下降,从而抵消中子和γ射线综合电离导致的静态电流增长。     

Study of the Low Excited States of 72Ge

The radioactive decay of ⁷²Ga has been investigated by means of NaI-HpGe Compton-suppress spectrometer,and γ-γ coincidence measurements Performed with two HpGe detectors coupled to three-parameter(γ-γ-T) data acquisition system. 2.3×10⁷ coincidence events are collected. A new decay scheme of 72Ga including 26 levels,87 γ-rays is established. The extensive coincidence relationships are used to identify the γrays and levels of 72 Ge, such as new γ-rays of 225. 92, 826.97, 1349.71,1475. 32, 1667.91, 2105.28, 2247.39keV and new levels of 3248.01, 3396.27, 3806.10,3864.56keV. The unsure transitions of 112.59, 937.97, 2402.25, 2939.95keV and level of 2939.83keV are confirmed in thes work. No evidence has been observed for the existences of 113.5, 1155.7, 1192.4keV γ-rays and level of 3707.1keV. The transitiou of 317.72keV γ-ray is moved from 3757.26-3439. 51keV level to 3565.85-3248.01keV level.     

First In-beam γ Spectroscopic Experiment at HIRFL

The in-beam γ expedmental setup of HIRFL, which includes SFC(ECR ion source), direct-link-pipe(limit jaws) and in-beam γmeasurement system, was adjusted and tested with its first in-beam γ experiment. All performances, such as neutron and γ backgrounds of the setup have reached to an ideal level. With some special γ-ray spectroscopic techniques, the in=beam γ experiment, including γ single spectrtum. γ excitation funcdon, γ angular distdbudon and γ-γ-t coincidence measurements, was perfomned using reacdon ¹⁶O (¹⁹⁷Au, xn).     

THE INVESTIGATION OF THE HIGH DENSITY MULTIWIRE PROPORTIONAL CHAMBER AS A DETECTOR FOR NEUTRAL PARTICLES

This paper describes a position sensitive multiwire proportional chamber with effective area of 200×200mm². The chamber combining with multi-layer lead γ-ray converter form a high density multiwire proportional chamber γ-ray detector. The lead converter is made in auniformly arranged matrix of 0.9mm diameter holes on a 1.1mm pitch. For 511keV photons the detection efficiency is 5.6%, and the spatial resolution is 1mm. The detector has been used in the investigation of positron camera, it also offers possibility for X-ray detection.     

Study on Irradiation Damage of Bi-Doped PbWO4 Crystal

The luminescence and point defects of pure lead tungstate crystals (PbWO₄) and Bismuth (Bi) doping crystal (PbWO₄:Bi)grown by modified Bridgman method are studied. It is found that irradiation results in the great change of the transmission and X-ray excited emission after γ-ray irradiation about 4 Mrad dose. The defects in PbWO₄ crystal have been studied by means of positron annihilation lifetime and X-ray photoelectron spectra. The results show that Bi dopant suppresses the concentrations of positron capture centers and low-valent oxygen ions.After γ-ray irradiation,in the pure crystal the concentration of lead vacancy (V_Pb) is decreased and that of low-valent oxygen increased; on the contrary,in Bi dopant crystal the concentrations of positron capture centers increased and that of low-valent oxygen ions suppressed. It is tentatively proposed that Bi³⁺ dopants would mainly occupy the sites of lead vacancies resulted from Pb volatilization. And irradiation changes the chemical valence of Bi element,which is Bi³⁺→Bi⁵⁺.The Bi⁵⁺ will replace the lattice W⁶⁺ ions and it will cause some (WO₄)^2－ replaced by (BiO₃+V_O)^－.