快中子活化法对声空化核效应的验证

采用纯铜作为阈探测器检测声致核聚变产生的14 MeV中子。根据14 MeV中子与Cu的核反应,选择合适的放射性核素及其特征γ峰作为测量依据。中子辐照时间为50 min,经30 min和198 min冷却,NaI探测器分别测量了超声和非超声下活化铜片的511 keV特征γ峰计数,测量结果显示,采用短冷却时间可测得⁶²Cu的511 keV γ特征峰,γ峰净面积计数增量ΔC均为正值,具有统计意义,在声空化条件下核反应液体中D-T反应产生的14 MeV中子发生率大于在非声空化条件下的;采用长冷却时间可测得⁶⁴Cu的511 keV γ特征峰,ΔC均为正值,具有统计意义,在声空化条件下核反应液体中D-D反应产生的2.45 MeV中子发生率大于在非声空化条件下的。由此验证了声空化核效应（NEAC）,并初步分析了中子成核声空化核效应的机制。     

利用伴随α粒子能谱分析固体氚靶中氚浓度深度分布

在目前的氘氚中子发生器源中子分析过程中,固体氚靶中氚浓度深度分布信息的缺失是普遍遇到的问题。为解决此问题,本文建立了利用伴随粒子能谱反演氚浓度深度分布的模型,采用来自氚钛靶的α实验能谱作为模型测试对象,通过该模型获得了氚钛靶中氚浓度深度分布的数据。结果表明,氚浓度随氚钛靶深度的增加呈双峰趋势,两峰之间的氚浓度波谷位于靶中0.94 μm处,该深度正是入射氘粒子的射程极限。所得的氚浓度深度分布趋势与其他实验方法测量结果相符,表明该模型能为氘氚中子发生器的源中子分析提供即时的氚浓度深度分布信息。     

反冲质子望远镜效率计算中的相对论修正

反冲质子望远镜和伴随粒子法是绝对测量14 MeV单能快中子通量的两种独立的方法,在高压倍加器上利用T(d,n)~4He反应可以获得14 McV单能快中子。反冲质子望远镜是通过中子入射在聚乙烯辐射体上产生反冲质子,用记录反冲质子数来确定中子通量的,而伴随粒子法则是通过记录α粒子数来测定中子通量。随着14 MeV单能快中子的应用越     

多探测器快中子飞行时间谱仪

描述了一台串列加速器HI-13上的多探测器快中子飞行时间谱仪,并与国际上同类谱仪进行了比较。本谱仪主要用于能量大于8 MeV的快中子散射实验、次级中子双微分截面及带电粒子引起的出射中子能谱的测量。简要介绍了谱仪各主要部分(包括零信号拾取筒、氘气体靶、探测器、电子学等)的结构和特性及其在快中子实验中的应用。     

基于3层硅探测器的主动式中子个人剂量计研制

研制了一种具有能量分辨能力的中子个人剂量计。该个人剂量计由3层硅探测器组成，硅探测器周围装有⁶LiF、聚乙烯和含硼聚乙烯作为转化体、慢化体和吸收体。个人剂量计有直读和解谱两种工作模式。直读模式将中子能区划分为低能、中能和快中子3个能区，可实时测量。解谱模式可获得快中子能区的中子能量分布。利用GEANT4程序模拟了7 MeV γ射线的能量沉积谱，设置适当的甄别域以降低γ射线的影响。采用GEANT4程序模拟了个人剂量计对不同能量入射中子的个人剂量当量率响应。在加速器单能中子参考辐射场中完成了单能中子剂量响应的实验校准，对模拟计算的响应函数进行了实验修正，并得出了不同能区的平均中子个人剂量当量率响应。     

快中子照相MCNP模拟计算

正快中子照相是近些年新开展的一种照相技术,与热中子照相相比,快中子照相快中子具有能量较高、与物质作用截面较小、穿透能力强等特点,快中子穿过较厚被测样品材料时,通过记录出射的快中子可检测出物体内的元素空间分布、材料结构上差异等信息。本工作利用MCNP模拟计算了2.45 MeV中子穿过不同厚度聚乙烯样品及金属样品后的计数情况(图1),样品出射中子选用塑料闪烁体进行探测,实物如图2所示。对2.45 MeV快中子成像分辨率及塑料闪烁体探测     

基于14 MeV μs脉冲中子发生器与NaI(Tl)和BGO闪烁探测器的爆炸物检测系统的研制

介绍了利用14 MeV μs脉冲中子发生器、NaI(Tl)和BGO闪烁探测器建立的爆炸物检测实验系统.研究了中子感生瞬发γ能谱的时间特性,分别测量了快中子的非弹性散射γ能谱和热中子辐射俘获γ能谱.使用了NaI(Tl)和BGO两种探测器测量γ能谱;NaI(Tl)探测器在测量14N的热中子辐射俘获γ 10.835 MeV时表现出了很好的性能,而BGO探测器则在测量12C和16O的快中子非弹性散射γ时得到了较好的结果.利用这两种探测器测量了22种样品,其中包括RDX、TNT、NQ 3种炸药.根据NaI(Tl)和BGO测量到的中子感生瞬发γ能谱,在分析了1H、12C、14N、16O的元素含量之后,有效地实现了对炸药与普通物品的分辨.     

LiF-TLD的响应对致电离粒子LET的依赖性初步实验研究

对LiF热释光探测器（TLD）的响应对致电离粒子的LET的依赖性进行了初步实验研究。用作实验研究的粒子主要是中子,包括热中子和由7Li(p,n)7Be、T（p,n）3He核反应生成的中能中子、快中子（0.018～0.945MeV）及14MeV中子。实验结果表明：LiF(Mg、Cu、P)-TLD的响应对致电离粒子LET的依赖性是显著的。对于较高能量的中子,由LiF-TLD产生的热释光量仅与6Li、7Li在LiF-TLD中导致的吸收剂量相对应,这与某些文献的报道相一致。     

可更换轰击靶位的偏心靶室装置

0°方向引出中子的旋转靶由于很难提供α粒子引出管道,因此,给用伴随粒子方法进行中子源强的精确测量带来了困难;而文献[1]中用的靶室由于束流斑点的中心与氚钛靶的几何中心偏离甚小,使它的应用受到了限制。为了满足快中子辐照和快中子活化分析等实验对靶子方面提出的要求,使中子源强能较长时间地稳定在10~(11)n/s水平,并且尽可能充分利用靶面,我们设计并调试好偏心固定靶靶室,改进了水冷系统,对于直径为5cm、活性区直径为4.4cm的氚钛靶,使用的半寿命由原来的6～12μA·h,提高到30～60μA·h。     

用~6Li半导体谱仪测量临界装置中子能谱

本文介绍~6Li夹心半导体中子谱仪的组成、原理及其实验技术。在2.5MeV静电加速器及400keV倍加器上用单能中子验证了谱仪的能量线性。讨论了分辩函数半宽度随中子能量变化的规律。用这种谱仪测量了浓缩铀裸球临界装置中心快中子谱,复盖能区40keV—10MeV;解谱程序移植了SAND-Ⅱ方法展开箔片积分数据。     

声空化核效应实验的中子探测系统

设计建立了用于声空化核效应的中子测量系统,该系统由ST-451液闪探测器和BF₃正比计数管组成,各中子谱仪的仪器精度<2.42%,并导出BF₃正比计数管的中子探测灵敏度计算式。利用高压倍加器氘离子轰击D-Ti靶产生的2.45MeV中子,对BF₃计数管进行探测灵敏度标定。利用BF₃正比计数管测量声空化核效应实验的声核中子,由此估算有效中子发生率为7.0×10⁴～8.0×10⁵s^-1。     

声核中子测量的屏蔽设计

通过测定声空化核效应实验室各测量点的中子注量率,了解实验室墙壁和地面对出射中子的散射,选定散射中子相对较弱的位置作为声核中子测量点。利用SHIELD程序模拟不同材料的中子屏蔽效果,选用4cm铁和20cm含硼石蜡组成屏蔽体,以降低中子本底。测定影屏蔽及影屏蔽结合BF₃正比计数管环绕屏蔽两种方式下的散射修正因子F_s,提出以统计显著性增量S.S.I≥3/[KF(]F_s[KF)]作为超声中子计数相对于非超声中子计数的增量ΔC是否具有统计意义的判据。     

50MeV／u^12C离子实验靶区中子注量率的测量

用阈探测器中子活化法测量了50MeV/u~(12)C离子实验靶区出射的热中子以及E_n分别大于6、11、20、50MeV的中子注量率。     

Characterization of displacement cascade damage produced in Cu3Au by fast-particle irradiation

Zones of reduced long-range order created at displacement cascade sites in well-ordered Cu₃Au may be directly imaged in the transmission electron microscope so that quantitative information can be obtained on individual cascade events. This technique has been used to characterise the cascade damage created by three fast particles (3.5 MeV protons, a source of moderated fission neutrons and a source of fusion neutrons with energies peaking at 14.8 MeV) with the aim of comparing the experimental observations with the relevant collision models. In each case, disordered zone number densities, sizes and shapes were determined, and were found to be characteristic of each irradiation, with the sizes of disordered zones and the proportion of zones of complex shape increasing on going from 3.5 MeV protons to fission neutrons to fusion neutrons. The quantitative results are largely consistent with the different calculated primary recoil spectra, although in the fusion neutron case some discrepancies are found which cannot readily be explained by limitations in the experimental technique. More specifically, more and larger disordered zones are found than expected from the calculated recoil spectrum. Subcascade formation was observed only in the neutron irradiations, with the distributions of sizes and shapes of individual sub-cascades being very similar in the two cases (in marked contrast to those obtained from sizing total cascade events). Finally, the production of point-defect clusters at cascade sites was studied. The efficiency of cascade collapse increased on going from 3.5 MeV protons to fission neutrons to fusion neutrons.     

Deuterated liquid scintillator (NE230) as a fast neutron detectorfor cold-fusion and other research

Deuterated scintillators (NE230) can provide, without time-of-flight, usable neutron energy spectra for neutrons E _n⩾1 MeV. The authors have assembled and calibrated several of these detectors and used them in experiments searching for d+d fusion-neutron emission (E_n, 2.5 MeV) in Pd+D ₂O electrolysis and Ti+D₂ adsorption at LN temperatures. The detectors yielded direct fusion-neutron spectra and set limits in the Pd+D and Ti+D experiments of <7×10^-24 fusion n/s/dd pair and <3×10^-24 fusion n/s/dd pair respectively. In addition, these detectors have been used for in-beam accelerator experiments requiring coincidence between fast neutrons and scattered ions     

Proton simulation of displacement effects induced in metals by 14 mev neutrons

In designing a D-T fusion reactor, one must know the effect of a high flux of 14 MeV neutrons on structural materials. Available laboratory sources of 14 MeV neutrons are not intense enough to expose samples to the expected flux. Bombardment with other particles is one way of simulating the anticipated neutron environment. The energy spectrum of atoms recoiling from collisions with bombarding particles can be calculated from elastic-scattering and nonelastic-reaction data for the incident species. This analysis shows that 16 MeV protons closely simulate the displacement effects caused by 14 MeV neutrons. In niobium the average atom recoiling from a 14 MeV neutron interaction has 65 keV of damage energy. The mean damage energy deposited per cm³ of niobium by a fluence of one 14 MeV neutron per cm² is 14 keV. The equivalent quantity for 16 MeV protons incident on niobium is 33 keV.     

Calculation of Response Function for Bonner Sphere Spectrometer Based on Geant4

In order to make further studies on fusion neutron diagnosis on HL-2A /HL-2M,we have developed and succeeded in the calculation of the Response Function for a Bonner sphere spectrometer,which consists of eight polyethylene spheres with ³He proportional counters inside.The response function of the Bonner spectrometer to neutrons is of fundamental importance for its neutron spectrum unfolding procedure and is directly related to the quality of the unfolded spectrum.In this paper,we calculated the response function to neutrons from 10-9 MeV to100 MeV by Geant4.In order to test the accuracy of the Geant4 simulation,we apply it to measure an ²⁴¹Am-Be neutron source,and the measured neutron counts of the spectrometer and simulated counts are found to be highly consistent,with a relative error up to 9.3%.This has proven the calculation of the neutron response of the Bonner sphere spectrometer by Geant4 to be quite accurate.     

Confirmatory experiments for nuclear emissions during acoustic cavitation

Confirmatory experiments were conducted to assess the potential for nuclear fusion related emissions of neutrons and tritium during neutron-seeded acoustic cavitation of deuterated acetone. Corresponding control experiments were conducted with normal acetone. Statistically significant (5–11S.D. increased) emissions of 2.45 MeV neutrons and tritium were measured during cavitation experiments with chilled deuterated acetone. Control experiments with normal acetone and irradiation alone did not result in tritium activity or neutron emissions. Insights from imaging studies of bubble clusters and shock trace signals relating to bubble nuclear fusion are discussed.     

A thin film 10B sample for measuring the atom number

In order to measure differential cross sections of the 10B(n,α)7Li reaction induced by MeV neutrons using the forward-backward coincidence method, a thin film 10B sample was designed and the 10B atom number was determined with a reference 10B film sample. Alpha counts of the 10B(nth,α)7Li reaction from the 10B thin film and the reference sample were measured using a gridded ionization chamber and thermal neutrons, which were moderated and thermalized by paraffin from fast neutrons produced in D(d,n)3He reaction on a 4.5 MV Van de Graaff. The neutron flux was normalized by measuring the fission yield of a small 238U fission chamber.