低能电子束设备与应用

低能电子束是一种先进的底层共性技术,美国、日本及欧洲发达国家从20世纪80年代开始就将该技术广泛应用于各种高科技产品的生产制造过程中。由于进口电子束设备及配套工艺和原材料的价格昂贵,严重制约了低能电子束技术在国内的推广。近年来,国内自主研发低能电子束设备技术的快速进步,降低了下游行业的进入门槛,有力推进了国内企业在新材料、新技术、新工艺上的研究,突破了行业发展瓶颈,使低能电子束及应用迎来快速发展。     

Carrier-free production of Tc at an electron accelerator

We report on the results of studies of the ⁹⁵Tc isotope production conditions in a poorly investigated ⁹⁶Ru(γ,N)⁹⁵Tc reaction at a relatively inexpensive electron accelerator. Based on the analytical model it is demonstrated the possibility for estimating the effective and peak cross-sections and the isotope yield for a given reaction in a thick production target without preliminary determination of its excitation function. For this purpose we compared specific activities of two small samples that were activated under the same conditions using the reference reaction ⁶⁸Zn(γ,p)⁶⁷Cu and the one under investigation. The experiment on simultaneous photo-activation of natural zinc and ruthenium targets was performed followed by the investigation of their isotope composition. The specific activity of the radionuclide was measured and cross-sections for the ⁹⁶Ru(γ,N)^95g,mTc reactions were determined. The yields of desired isomers and admixtures in the natural ruthenium targets of different size were estimated. It is shown, in particular, that the operating conditions of the NSC KIPT accelerator KUT-30 can provide ^95gTc yields up to 120 mCi/h.     

电子束辐照制备纳米银

在水溶液中,常温常压下不加入任何催化剂,用电子加速器辐照作为一种新的方法可以成功制备出纳米银。我们利用XRD、TEM、UV、DSC来分别表征材料的结构、形貌、大小、光学特性以及材料的熔点。TEM图像证明颗粒大小为30nm,这与XRD实验通过Scherer理论公式计算的结果相一致。     

电子束辐照制备纳米镍

在水溶液中,常温常压下不加入任何催化剂,用电子束加速器辐照作为一种新的方法可成功制备纳米镍。利用X射线衍射(XRD)、透射电子显微镜(TEM)、激光衍射粒度分布仪(LSPSDA)、紫外可见光分光光度计(UV)、样品振荡磁力计(VSM)和差热分析仪(DSC)来分别表征材料的结构、形貌、大小、粒径分布、光学特征、磁学性能以及材料的熔点。TEM图像和LSPSDA分布图证明颗粒大小为39nm,这与XRD实验通过Scherer理论公式计算的结果相一致。     

Axial ion–electron emission microscopy of IC radiation hardness

A new system for performing radiation effects microscopy (REM) has been developed at Sandia National Laboratory in Albuquerque. This system combines two entirely new concepts in accelerator physics and nuclear microscopy. A radio frequency quadrupole (RFQ) linac is used to boost the energy of ions accelerated by a conventional Tandem Van de Graaff–Pelletron to velocities of 1.9 MeV/amu. The electronic stopping power for heavy ions is near a maximum at this velocity, and their range is 20 μm in Si. These ions therefore represent the most ionizing form of radiation in nature, and are nearly ideal for performing single event effects testing of integrated circuits. Unfortunately, the energy definition of the RFQ-boosted ions is rather poor ( a few %), which makes problematic the focussing of such ions to the submicron spots required for REM. To circumvent this problem, we have invented ion electron emission microscopy (IEEM). One can perform REM with the IEEM system without focussing or scanning the ion beam. This is because the position on the sample where each ion strikes is determined by projecting ion-induced secondary electrons at high magnification onto a single electron position sensitive detector. This position signal is then correlated with each REM event. The IEEM system is now mounted along the beam line in an axial geometry so that the ions pass right through the electron detector (which is annular), and all of the electrostatic lenses used for projection. The beam then strikes the sample at normal incidence which results in maximum ion penetration and removes a parallax problem experienced in an earlier system. Details of both the RFQ-booster and the new axial IEEM system are given together with some of the initial results of performing REM on Sandia-manufactured radiation hardened integrated circuits.     

Concept of electron accelerator-driven system based on subcritical cascade reactor

A concept of accelerator-driven system consisting of electron accelerator, neutron-generating target and two-core subcritical blanket with fast and thermal neutron spectrum has been presented. Some general features of the cascade neutron multiplication in the two-core subcritical blanket are discussed. Calculation results are demonstrated for the processes of electron–photon–neutron interactions of electron beam with the target material. Neutronic and heat engineering characteristics of the facility are also described. It has been shown that with the system's subcritical level of 2% and electron beam power of 4 MW, the facility power is as high as 50 MW.     

国产工业用电子加速器及离子束表面处理装置的研发与应用案例

S波段无损检测用电子直线加速器主要用于压力容器、石化等行业部件的无损检测。由于现场检测需求,开发了X波段电子直线加速器,其特点是灵活、轻便。北京机械工业自动化研究所（北自所）提供辐照电子加速器系统整体解决方案,包括加速器、传送线、生产管理系统、立体库以及厂房。电子帘加速器是北自所新研发的设备,目前包括两种型号,加速电压分别为200 kV、150 kV。离子束表面加工包括离子注入表面改性技术、磁过滤多弧离子镀膜技术与离子束辅助沉积镀膜技术,可在零部件的表层形成耐腐蚀、耐摩擦、防结冰、减少摩擦膜层,主要应用于轴承、空速管等航空领域。     

电子束辐照对冷却猪肉杀菌保鲜效果的研究

利用电子束辐照技术对冷却猪肉的杀菌和保鲜效果进行了研究,为电子束辐照技术应用于肉类加工业提供应用依据。以束流能量（X1）和辐照吸收剂量（X2）为试验因子,以菌落总数（Y）为指标,通过响应面分析法（RSM）研究了电子束辐照杀菌的效果及对货架期的影响。电子束辐照对冷却猪肉杀菌效果的二次多项数学模型为：Y=3．78—0．24X1-0．13X2-0．16X1X2—0．18X1^2＋0．15X2^2（R^2=0．9755）。辐照吸收剂量与束流能量之间存在协同增效作用,试验因子的显著性顺序为：剂量〉交互作用〉束流能量。使冷却肉初始菌数下降2个对数单位的辐照参数范围为3．23-4．0kGy,2．3～3．8MeV。经电子束辐照的冷却猪肉样品在4℃条件下贮藏,货架期比对照样品延长12d左右;在7～10℃条件下保存,货架期比对照延长9d左右。研究结果表明,电子束辐照对冷却猪肉具有杀菌保鲜作用,该研究对电子束辐照技术应用于冷却猪肉的生产实践具有指导意义。     

辐射治疗能区内电子束在轻介质中的平均能量计算

从高能电子在多成分介质中输运的Boltzmann方程出发,采用Fokker-Planck近似导出电子束能量分布的高斯谱,对连续慢化近似（CSDA）进行修正从而引入修正的CSDA平均能量,并采用杨振宁的多次散射理论,最后给出一个计算高能电子束平均能量的递推-迭代算法。并给出了由该算法得出的部分计算结果,并与相应的Monte-Carlo模拟及实验测量作了比较,比较的结果表明该算法能够较为精确地计算高能电子束在轻介质中的平均能量变化。此外,还讨论了在辐射治疗剂量算法中最常见的电子束平均能量计算公式,即Harder公式和Brahme公式,并提出了一个较这两个公式更为精确的半经验公式。     

环氧树脂分子量对电子束辐射固化效果的影响

研究了分子量对于环氧树脂电子束辐射固化行为的影响规律。环氧树脂体系的辐射反应速率随分子量增加而下降,在低辐射剂量下,高分子量树脂的固化度和固化层厚度较小,提高辐射剂量,分子量的影响减弱。对于辐射固化程度较高的样品,其玻璃化温度(Tg)和贮能模量(E’)主要受固化度控制。电子束辐射固化的环氧树脂进行热处理后,样品的玻璃化温度和高温E’均有所提高,低分子量树脂的热处理效果更为明显。     

低能电子束循环辐射硫化天然橡胶乳液

应用250keV低能电子束循环辐射硫化二丙烯酸壬酯（1,9-nonanedilo diacrylate，NDDA）敏化的天然橡胶乳液，探讨了影响低能电子束循环辐射硫化天然橡胶乳液的因素。结果表明，提高电子束束流，可缩短辐射硫化时间；40％的天然橡胶乳液更适合低能电子束的辐射硫化；适当提高循环乳液的重量有利于辐射硫化乳液的质量控制。     

电子束在MOS结构中的能量沉积与辐照效应

根据电子输运“双群理论”计算出电子在Ｓｉ－ＳｉＯ２材料中的能量沉积。用与硅等２效的外推电离室测定了１．０ＭｅＶ和１．５ＭｅＶ的电子束在ＭＯＳ电容芯片中的吸收剂量。用Ｘ光电子谱、俄歇谱、深能级瞬态谱和Ｃ－Ｖ方法测量分析了ＭＯＳ电容Ｓｉ－ＳｉＯ２材料化学结构，界面态密度和Ｃ－Ｖ曲线在辐射前后的变化，根据理论和实验结果，从辐射剂量学的角度分析讨论了电子能量沉积，电离缺陷和辐射效应间的关系，并提出一个关于     

电子束辐照聚碳硅烷热解合成 SiC 陶瓷材料──I . 空气中辐照产物的热解特性研究

利用加速器产生的电子束（ＥＢ）在空气中辐照聚碳硅烷（ＰＣＳ），以使之形成交联结构，然后经高温热解转化成ＳｉＣ陶瓷。结果表明：在辐照产物中形成了ＳｉＣＳｉ以及ＳｉＯＳｉ等交联结构，热解温度以及热解陶瓷产率都随辐射吸收剂量增加而明显提高。通过ＴＧＩＲ联用分析技术，在热解产物中检测到了低分子量ＰＣＳ以及ＣＨ４等小分子化合物，在吸收剂量高于２．３ＭＧｙ时，ＰＣＳ主要通过析出ＣＨ４而热解成ＳｉＣ。     

氧化锡气体传感器的电子束辐照效应

There are many traditional ways to improve sensitivity and selectivity of semiconductor gas sensors, such as metal ions adulteration and surface modification. In this paper 1.75 MeV electron beam was used to modify surface structure of tin dioxide gas sensors, and the gas sensing characteristics were studied. Results showed that the sensitivity and selectivity of SnO2 sensors were improved after the electron beam irradiation.     

Two-stage EEHG for coherent hard X-ray generation based on a superconducting linac

A two-stage echo-enabled harmonic generation (EEHG) scheme is proposed for a superconducting linacdriven FEL to produce coherent hard X-rays.Electron beams of quite different bunch lengths are separately used in each stage of EEHG,and a monochromator is designed to purify the radiation from the first stage for seeding the second stage.Theoretical analysis and 3D simulations indicate that the proposed scheme can generate high-repetition-rate coherent hard X-ray pulses directly from a conventional UV seed laser.     

Energy-spread measurement of triple-pulse electron beams based on the magnetic dispersion principle

The method of energy dispersion in magnetic field is used to analyze the energy spread of the triple-pulse electron beam generated by the Dragon-II linear induction accelerator.A sector magnet is applied for energy analysis of the electron beam,with a bending radius of 300 mm and a deflection angle of 90°.For each pulse,the time-resolved and integral images of the electron position at the output port of beam-bending line are recorded by a streak camera and a CCD camera,respectively.Experimental results demonstrate an energy spread of less than ±2.0%for the electron pulses.The cavity voltage waveforms obtained by different detectors are also analyzed for comparison.     

EAST-NBI反向电子吸收板换热计算与分析

中性束注入是托卡马克主要的辅助加热手段。目前先进实验超导托卡马克中性束注入(Experimental Advanced Superconducting Tokamak-Neutral Beam Injection,EAST-NBI)装置采用的是正离子源,运行过程中离子源的部分部件有很大的热沉积,其中反向电子吸收板最为严重。经实验研究,当束功率为3.5 MW时,沉积在反向电子吸收板上的平均功率密度高达4.4 MW·m~(-2),有着较大的换热负担。为探究反向电子吸收板的极限运行时间,采用数值模拟的方法,对反向电子吸收板在不同束功率、冷却水水压等多种工况进行了计算。结果表明,电子吸收板随着束功率的增大,换热负担加重、换热效果变差,通过增压泵提高冷却水入口压力一定程度上可以提高换热能力,使其极限运行时间延长。对该课题的研究可以指导EAST-NBI的运行,以保证离子源安全、稳定工作,此外还为反向电子吸收板的进一步结构优化奠定理论基础,对发展长脉冲、高功率的离子源具有重要意义。