共查询到20条相似文献,搜索用时 125 毫秒
1.
超短超强激光与等离子体相互作用产生的激光尾波场可以在毫米尺度上加速产生高能量的准单能电子束.在SILEX-Ⅰ激光装置上进行的激光尾波场加速实验中,利用超强飞秒激光与超声速锥形喷嘴产生的2.7mm直径氦气气体柱相互作用,获得了能散为15.5%、发散角为15mrad、能量为58MeV的准单能电子束.在70TW激光照射下获得的电子束总电量达到15.4nC.介绍了实验条件、方法和主要实验结果. 相似文献
2.
北京大学4.5 MV静电加速器是20世纪80年代我国自主研发的静电加速器。该器端电压在0.7~3.8 MV连续可调,主要加速氢/氦同位素离子,并可通过打靶产生准单能直流/脉冲中子场,具有多条束线及多个实验终端。该器作为开放仪器多年来为国内外从事核技术研究的团队提供了实验平台。近年来,针对我国在能源、航天和国防等领域材料研究的重要需求,该器进行了多次升级改造。一方面通过产生7 MeV以下和14~19 MeV的准单能中子场,应用于(n, a)核反应截面的测量和聚变堆中子谱仪刻度;另一方面,通过温控辐照、核反应分析等实验终端,实现了材料辐照损伤及聚变堆材料元素定量分析等研究方向的功能拓展。此外,设计新增用于半导体材料电学性能测试的原位在线辐照终端和用于研究材料微观尺度元素分布的离子束综合分析实验终端。目前部分新终端已设计组装完成,相关搭建和调试工作正在进行中。 相似文献
3.
4.
5.
采用蒙特卡罗方法模拟了1064 nm,GW/cm2级脉冲激光辐照下,纳米尺度材料中电子迁移及加速过程.电子在激光场中迁移的过程涉及晶格散射、表面散射以及碰撞电离等作用.结果表明:材料的尺度小到一定程度后,表面散射作用主导电子散射过程,小尺寸限制效应表现明显,电子很难有效地吸收激光能量.研究结果对分析具有纳米尺度微结构材料的激光损伤行为提供了依据.同时,根据该小尺寸限制效应可以设计出具有新型纳米微结构的高激光损伤阈值薄膜.
关键词:
激光辐照
小尺度效应
电子加速
蒙特卡罗模拟 相似文献
6.
7.
锆钛酸铅镧(Pb0.94La0.06Zr0.96Ti0.04O3,PLZT)具有良好的介电和储能性质,是高效、高能量密度电容元件和存储器件的基体材料.为研究该材料的中子辐照损伤,首先基于Geant4程序包模拟了能量为1—14 MeV中子辐照浩钛酸铅镧(PLZT)材料产生的反冲原子能谱,然后根据产生的反冲原子种类和最大能量,利用二元碰撞方法模拟了不同能量的离子在PLZT中产生的位移损伤(包括空位和间隙原子),最后根据反冲原子能谱和对应能量离子在材料中产生的缺陷数目计算了不同能量的中子在PLZT材料中产生缺陷浓度以及分布.结果发现,对于1—14 MeV能区的快中子而言,其在厚度为3 cm的PLZT材料中产生的缺陷数目近似与中子能量无关,约为460±120空位/中子.辐照损伤在3cm厚度内随深度的增加而略有减小,总体变化小于50%,该减小主要是由于中子的反散射导致.本工作为计算中子在材料中的位移损伤提供了一种方法,同时模拟结果可为研究PLZT基电子器件的中子辐照效应提供指导. 相似文献
8.
第四讲 超强激光脉冲与等离子体相互作用中高能离子的产生 总被引:2,自引:0,他引:2
近几年来,由于高功率激光技术的不断发展,利用超强激光脉冲与等离子体相互作用产生高能离子束的研究得到了极大推动.实验和理论模拟均发现,在超强激光脉冲与等离子体相互作用过程中,可以产生高亮度、小尺寸、方向性好的高能质子束和高能重离子束.这种基于超强激光的高能离子源在先进离子束成像技术、惯性约束聚变混合“快点火”、新型台面离子加速器以及医疗等方面都有很诱人的应用前景.文章主要介绍了超强激光与固体靶相互作用中高能离子束(尤其是质子束)的加速机制、高能离子束特性、常用测量方法及其潜在应用,并对最新的研究进展进行了简单介绍. 相似文献
9.
为了探讨聚变堆候选低活化钢的抗辐照性能,在兰州重离子加速器国家实验室HIRFL的材料辐照终端,利用63 MeV的~(14)N离子和336 MeV的~(56)Fe离子在-50?C下对一种国产低活化钢进行辐照实验.借助离子梯度减能装置,使入射离子能量在0.22—6.17 MeV/u之间变化,从而在样品表面至24μm深度范围内产生0.05—0.20 dpa的原子离位损伤坪区.利用纳米压痕仪测试样品辐照前后的显微硬度,通过连续刚度测量(constant stiffness measurement)得到低活化钢硬度的深度剖面信息.使用Nix-Gao模型很好地描述了纳米压痕硬度随深度递减的现象(压痕尺寸效应,indentation size effect),从而有效避免了低能离子辐照的软基体效应(softer substrate effect).正电子湮灭寿命谱显示低活化钢在辐照之后长寿命成分增加,说明样品中产生了大量缺陷形成空位团,从而导致了材料力学性能的变化,在离子辐照剂量增加至0.2 dpa时,平均寿命τ_m增加量逐渐变慢,材料中辐照产生的缺陷趋于饱和. 相似文献
10.
11.
Willingale L Mangles SP Nilson PM Clarke RJ Dangor AE Kaluza MC Karsch S Lancaster KL Mori WB Najmudin Z Schreiber J Thomas AG Wei MS Krushelnick K 《Physical review letters》2006,96(24):245002
A beam of multi-MeV helium ions has been observed from the interaction of a short-pulse high-intensity laser pulse with underdense helium plasma. The ion beam was found to have a maximum energy for He2+ of (40(+3)(-8)) MeV and was directional along the laser propagation path, with the highest energy ions being collimated to a cone of less than 10 degrees. 2D particle-in-cell simulations show that the ions are accelerated by a sheath electric field that is produced at the back of the gas target. This electric field is generated by transfer of laser energy to a hot electron beam, which exits the target generating large space-charge fields normal to its boundary. 相似文献
12.
Generation of Ultrahigh-Velocity Collisionless Electrostatic Shocks Using an Ultra-Intense Laser Pulse Interacting with Foil-Gas Target 下载免费PDF全文
Ultra high-velocity collisionless shocks are generated using an ultra-intense laser interacting with foil-gas target,which consists of copper foil and helium gas.The energy of helium ions accelerated by shock and the proton probing image of the shock electrostatic field show that the shock velocity is 0.02c,where c is the light speed.The numerical and theory studies indicate that the collisionless shock velocity exceeding 0.1 c can be generated by a laser pulse with picosecond duration and an intensity of 10~(20) W/cm~2.This system may be relevant to the study of mildly relativistic velocity collisionless shocks in astrophysics. 相似文献
13.
赵磊 徐妙华 张翌航 张喆 朱保君 姜炜曼 张笑鹏 赵旭 仝博伟 贺书凯 卢峰 吴玉迟 周维民 张发强 周凯南 谢娜 黄征 仲佳勇 谷渝秋 李玉同 李英骏 《物理学报》2018,67(22):222101-222101
在利用超强激光驱动中子源的研究和应用研究中,中子源的产额及其角分布至关重要.我们在星光Ⅲ号激光装置上采用气泡探测器对强激光驱动的中子源的产额及其角分布进行了测量.利用超强皮秒激光与碳氘薄膜靶相互作用产生高能氘离子束撞击次级碳氘靶,通过氘-氘核反应产生准单能快中子.实验发现中子束的发射具有一定的方向性,在入射氘离子的传输方向上中子束具有更高的强度,测量得到的中子束最大强度为5.13×107 n/sr.利用实验测量的氘离子能谱和角分布对中子束角分布进行了理论计算,结果与实验测量基本一致. 相似文献
14.
15.
To find a model that describes the gas diffusion on irradiated polymers (Makrofol KG polycarbonate) the diffusion constants have been measured with argon as diffusion gas. The polymers were irradiated with uranium, gold and lead ions of about 10 MeV/u and ion fluences between 1×1010 and 4×1011 ions/cm2. The ion irradiated probes show two quite different dependencies of the diffusion constant on the ion energy loss. These effects are strongly related to the fluence of the irradiation. In case of low ion fluences, the diffusion constant is up to 8 times higher than that of pristine material. In the probes with high ion fluences we observe a decrease of diffusion constant to half the value of the pristine material. To understand the dependence of the diffusion constant on ion fluences we apply a model of compacting. This model describes the compacting ability of shockwaves arising from latent tracks. A track formation model is suggested. When an ion penetrates the foil it creates shockwaves around its path. These shockwaves put compacting forces on earlier created latent tracks in the same foil. 相似文献
16.
实验中测量了0.38V_(Bohr)(460 keV)高电荷态Xe~(q+)(4≤q≤20)离子轰击高纯Ni表面发射的400-510 nm光谱.实验结果包括NiⅠ原子谱线,NiⅡ离子谱线,以及入射离子中性化发射的XeⅠ,XeⅡ和XeⅢ谱线.研究了谱线XeⅡ410.419,XeⅢ430.444,XeⅡ434.200,XeⅡ486.254,NiⅠ498.245,NiⅠ501.697,NiⅠ503.502,NiⅠ505.061和NiⅠ508.293 nm的光子产额随着入射离子电荷态的变化.结果表明,入射离子中性化和溅射Ni原子发射谱线的光子产额随着入射离子电荷态的增加而增加,其趋势与入射离子势能一致. 相似文献
17.
Kelly H. Lepone A. Marquez A. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》1997,25(3):455-459
The nitrogen ion spectrum generated from a low energy Mather-type Plasma Focus device is reported. The main species of ions present are N +1, N+2, and N+3. It is found that its relative concentrations at a distance of several cm from the ion source are in agreement with those predicted for an equilibrium charge-state of the beam, and hence the spectrum of the neutral nitrogen is also derived. By taking into account the lateral spread of the beam due to multiple elastic scattering with the background gas, the derivation of absolute values for the total ion spectrum within the investigated energy range (>170 keV), the total number and total energy of the fast particles has been obtained 相似文献
18.
19.
针对热核聚变面向等离子体钨材料中氦泡形成、演变以及机理研究的需求,克服目前常用离子注入、电子扫描显微镜和透射电子显微镜等离线研究手段存在的不足,提出氦离子显微镜对钨中氦的上述行为原位实时在线研究方法.借助氦离子显微镜的离子注入、显微成像和聚焦离子束纳米加工功能,它可以提供能量为0.5—35 ke V、束流密度可达10~(25) ions/(m~2·s)以上的氦离子束,在该设备上进行钨中氦的注入实验.同时在注入过程,实时在线监测钨中氦泡形成、演变过程以及钨材料表面形貌的变化,原位在线分析钨材料表面氦泡的大小、迁移合并以及其诱发的钨表面和近表面的微观损伤.实验结果表明:氦离子显微镜是研究钨中氦行为演变过程及其微观机理研究的新的研究手段和强有力的实验工具. 相似文献
20.
D. Behera T. Mohanty S. K. Dash T. Banerjee D. Kanjilal N. C. Mishra 《Radiation measurements》2003,36(1-6):125-129
Swift heavy ions (SHI) with electronic energy loss exceeding a value of 14.4 keVnm−1 create amorphized latent tracks in YBCO type superconductors. In the low fluence regime of an ion beam where tracks do not overlap, a decrease of the superconducting transition temperature as probed through resistivity studies, is not expected due to availability of percolating current paths. The present study however shows Tc decrease by about 1–3 K in thin films of YBCO when irradiated by 250 MeVAg ions at 79 K at a fluence of 5×1010–1×1012 ionscm−2. The highest fluence used in the present study is three times less than the fluence where track overlapping becomes significant. The Tc tends to increase towards the preirradiation value on annealing the films at room temperature. To explain this unusual result, we consider the effect of ion irradiation in inducing materials modification not only through creation of amorphized latent tracks along the ion path, but also through creation of atomic disorder in the oxygen sublattice in the Cu–O chains of YBCO by the secondary electrons. These electrons are emitted radially from the tracks during the passage of the SHI. Considering the correlation between the charge state of copper and its oxygen coordination, we show in particular that the latter process is a consequence of the inelastic interaction of the SHI induced low-energy secondary electrons with the YBCO lattice, which result in chain oxygen disorder and Tc decrease. 相似文献