共查询到19条相似文献,搜索用时 140 毫秒
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在温度场和应力场计算的基础上建立了强流脉冲电子束轰击作用下的扩散模型,并给出了数值方法及其数值解。该模型与方法同样适用于其它高能束流作用下的扩散过程。计算表明,浓度扩散流仍然是影响扩散的主要因素;而轰击超过一定次数后,扩散的作用将减弱;当边界条件为表面扩散时,扩散进行较快,这是表面涂覆加脉冲电子束后处理快速表面合金化工艺的理论基础。对实验结果和理论结果的对比分析表明,在脉冲轰击下,扩散激活能随空位浓度的增加而下降,从而加速扩散过程;在表面有熔化的情况下,则液态时的对流混合作用是主导因素。 相似文献
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强流脉冲电子束轰击对单晶Si表面形貌的影响 总被引:1,自引:0,他引:1
用强流脉冲电子束技术对两种取向的单晶Si片进行了表面轰击,对电子束诱发的表面形貌进行了分析.实验结果表明,当能量密度~3 J/cm2时,轰击表面开始形成大量的熔坑.能量密度~4 J/cm2时,表面开始出现微裂纹,微裂纹的形态与单晶Si的晶体取向密切相关;强流脉冲电子束轰击能够诱发表层强烈的塑性变形,[111]取向单晶Si表面出现剪切带结构,而[001]取向单晶Si表面变形结构则以微条带为主;此外,变形区域内还出现大量<100 nm的微孔洞形貌,这些微孔洞的形成为制备表面多孔材料提供了可能. 相似文献
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20MeV的强流脉冲电子束经加速聚焦后轰击韧致辐射转换靶,在产生脉冲X光的同时将大量能量沉积在靶内,导致靶材迅速膨胀飞散。在多个束脉冲作用下,后续脉冲由于靶材密度的降低可能无法产生足够的X光照射量。本文采用Monte-Carlo软件MCNP以及流体动力学软件ANSYSAUTODYN对靶材的动力学响应以及各脉冲所能产生的照射量进行了数值模拟,结果表明,在3个间隔500ns的20MeV、2kA、70ns、束斑1.5mm(FWHM)的电子束脉冲作用下,X光照射量无明显降低。 相似文献
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激光等离子体加速输出的电子束具有fs量级脉冲长度的优异品质。由于强激光场的存在,直接应用存在一定困难,更多应用场景需要把电子束传输到应用端。能散导致电子束在传输中产生能量啁啾,需要通过束流光学设计抑制脉冲长度的增长。通过对电子束在消色差束线中传输的研究,探索了消色差和非消色差传输中脉冲长度压缩的差异,以及消色差束线中偏转角度、偏转半径对不同能量电子束脉冲长度压缩的影响。针对消色差传输中仅有某个能量电子束得到最优压缩的局限,利用四极透镜磁场梯度的调节使电子束的传输适度偏离消色差,改变对能量啁啾的影响,实现在固定尺寸束线中不同能量电子束的压缩。 相似文献
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脉冲低能正电子束流主要利用慢正电子束流的单色性及能量连续可调等特点研究缺陷在材料表面或近表面不同深度的分布信息。脉冲低能正电子束流利用微束团化装置获得起始时间信号。微束团化系统由斩波器、预聚束器、聚束器构成,可将随时间连续分布的慢正电子束流转化为频率为37.4725MHz、脉冲宽度200-300ps的脉冲束流。聚束器为2/4N轴谐振器,谐振频率为149.89MHz, 相似文献
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《原子能科学技术》2019,(9)
利用15 TW激光脉冲,系统研究了基于电离化注入的激光尾波场加速。实验中,研究了等离子体密度、相互作用位置、激光脉宽以及激光能量对电子束的电荷量、发散角、指向性、能量以及产生概率的影响。将约400 mJ、25 fs的激光脉冲聚焦在喷嘴前沿,等离子体密度约9×10~(18) cm~(-3)时,电子的产生概率高达100%,获得了水平(竖直)发散角(6.5±0.5) mrad((5.3±0.3) mrad)、水平(竖直)指向稳定性±1.2 mrad(±0.7 mrad)、峰值能量(135±8) MeV和电荷量(13.5±2.0) pC(50 MeV)的稳定电子束,为其应用奠定了基础。 相似文献
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应用多极板放电室产生的纳秒级强脉冲电子束与Ar~+离子束辐照蕃茄、黄瓜、辣椒和小麦的种子,分别测定辐照种子中的自由基产额,统计胚根根尖细胞中的染色体畸变频率和种子的萌发能力,藉以比较两种不同脉冲处理的辐照效果。实验发现:辐照处理时间的长短与自由基产额、染色体畸变率以及种子的萌发能力密切相关。辐照处理时间长,自由基产额高,染色体畸变率高,萌发生长能力低。四种作物种子的重复实验证明,电子脉冲的辐射效应明显强于Ar~+离子脉冲。 相似文献
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为研究强流辐照过程中钛合金微观组织结构和化学成分的变化,利用束流成分70%H+和30%C+的混合强脉冲离子束对钛合金进行了表面轰击,对离子束诱发的显微组织形貌和化学成分在扫描电子显微镜(SEM)上进行分析。结果表明,钛合金内部组织由α和β两相构成,为α+β型两相钛合金。试样不同区域组织类型存在明显差异,大部分区域组织类型一致,局部区域属于典型的魏氏组织。强流辐照钛合金表层组织和微观结构发生一定的变化,边缘β相结构遭到一定程度的破坏。显微组织结构的变化是由于表层温度梯度引起的热应力及其在靶材体内的传播造成的。 相似文献
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Ijaz Shahid Jie Shen Xiao Yu Haowen Zhong Xiaojun Cui Guoying Liang Wanying Huang Shijian Zhang Sha Yan Xiaofu Zhang Xiaoyun Le 《Journal of Fusion Energy》2018,37(5):261-269
Due to the outstanding physical properties, Tungsten has been proposed for use in the divertor of future fusion devices. However, tungsten shall face strong particle bombardment from the plasma, which causes severe damage to the material. The purpose of this work is to build such an accurate analytical model which can predict the damages in target material like crack production and propagation after high intense pulsed ion beam irradiation. Hence, a two-dimensional finite element method is used to study the effect of high intense pulsed ion beam on tungsten surface numerically. To judge temperature and stress distribution in material, thermal conduction model is combined with non-linear fracture mechanics model and J-Integral parameter is used as a criterion to judge the crack propagation. Simulation results reveal that different crack heights and sizes can affect the results and there is a critical depth for crack propagation. The model gives good results to real experimental observations and has potential applications for different intense pulsed electron/plasma beams and different target materials as well. 相似文献
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YANG Yao LIU Zhanwen ZHANG Wenhui MA Hongyit ZHANG Xuezhen ZHAO Hongwei YAO Zeen 《核技术(英文版)》2012,(2):83-89
A 2.45 GHz electron cyclotron resonance intense proton source and a low energy beam transport line with dual-Glaser lens were designed and fabricated by Institute of Modern Physics for a compact pulsed hadron source at Tsinghua. The intense proton beams extracted from the ion source are transported through the transport line to match the downstream radio frequency quadrupole accelerator. Particle-in-cell code BEAMPATH was used to carry out the beam transport simulations and optimize the magnetic field structures of the transport line. Emittance growth due to space charge and spherical aberrations of the Glaser lens were studied in both theory and simulation. The results show that narrow beam has smaller aberrations and better beam quality through the transport line. To better match the radio frequency quadrupole accelerator, a shorter transport line is desired with sufficient space charge neutralization. 相似文献
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Sangappa S. Asha Ganesh Sanjeev R. Somashekar 《Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms》2009,267(14):2385-2389
Radiation-induced changes in hydroxypropyl methylcellulose (HPMC) films under electron irradiation were investigated and correlated with dose. Polymer samples were irradiated in air at room temperature by an electron beam accelerator in the range of 0-100 kGy. Various properties of the irradiated films were studied using a Ultraviolet-Visible spectrophotometer and Fourier transform infrared spectroscopy and thermogravimetric analysis. Electron irradiation was found to induce changes in the physical, chemical and thermal properties, depending on the irradiation dose. 相似文献
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《Journal of Nuclear Science and Technology》2013,50(5):698-702
The electron beam in medium scale (1-2 GeV) synchrotron radiation ring is attractive to generate an intense and narrow energy spread of laser-Compton gamma-ray beam in an MeV-region. Since the storage ring is operated with fixed electron energy for synchrotron radiation (SR) users, methods for changing the gamma-ray energy should be investigated. Three methods, 1) using a tunable laser, 2) changing the collision angle between the laser and the electron beam, and 3) selecting the scattering angle of the laser-Compton gamma-ray by using a collimator and an absorber, are studied by analytical calculation and simulation which takes into account the electron beam size and effective length of laser-electron interaction. Since a tunable laser has no enough power in the infrared wavelength region, an intense gamma-ray beam can not be generated by using a tunable laser at present stage. The collimator-absorber method generates enough amounts of gamma-rays, but simulation shows a broad energy spread, -7%, of the gamma-ray. An acceptable gamma-ray beam can be obtained by changing the incident angle of the laser beam whose pulse width and timing are synchronized with the electron beam pulse. 相似文献
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分析了脉冲离子轰击靶膜和衬底的热效应,在能量较低的情形下,离子轰击处理为靶膜表面热流输入。采用有限元程序,对能量为600keV、束流为12mA的不同束斑半径的脉冲离子流轰击Cu基Ti靶的热传导进行了数值计算,得到了热传导清晰物理图象。 相似文献
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S. K. Ngoi S. L. Yap B. T. Goh R. Ritikos S. A. Rahman C. S. Wong 《Journal of Fusion Energy》2012,31(1):96-103
A 3.3 kJ Mather type dense plasma focus device is used to generate a pulsed argon ion beam of 100 KeV in this work. Hydrogenated
amorphous silicon (a-Si:H) film prepared by plasma enhanced chemical vapor deposition (PECVD) on c-Si substrate was irradiated
with the argon ion beam produced by this dense plasma focus device. The effects of exposure to a single, 5 and 10 shots of
dense plasma focus argon ion beam irradiation on the surface morphology, crystallinity and chemical bonding properties of
the a-Si:H films were studied using Field Emission Scanning Electron Microscope (FESEM), X-ray Diffraction (XRD), Raman scattering
and Fourier Transform Infrared (FTIR) spectroscopy, respectively. Formation of nano-crystalline silicon phase along with increase
in structural order and hydrogen content in the film structure has been observed when the a-Si:H film was irradiated with
a single shot of dense plasma focus argon ion beam. Exposure to 5 and 10 shots of the dense plasma focus argon ion beam irradiation
reduced the hydrogen content resulting in a decrease in crystallinity and structural order in the film structure. 相似文献