基于北京大学4.5MV静电加速器的氘分布多能点NRA方法

Development of Multi-energies NRA Methods for Depth Profiling of Deuterium Based on 4.5 MV Electrostatic Accelerator in Peking University

为了满足核材料研究中对氘(D)滞留研究的需要,基于北京大学4.5 MV静电加速器,搭建三路探测系统的NRA分析装置,并建立氘含量及深度分布的多能点NRA方法。该方法利用D(~3He,p)~4He反应,采用多个能量(0.8~3.6 Me V)~3He^+入射,同时探测出射的p和4He,在较大的深度范围内有较好的深度分辨和较高的灵敏度。还在该系统上完成3He-D反应135°微分截面的测量,微分截面误差好于±3.9%。采用该方法进行初次样品氘含量的深度分布分析,靶为氘注入的PC-W样品以及TOKAMAK AUG偏滤器外打击点附近的CMSII-W样品。在钨样中获得的探测深度约6μm,在钨整个探测深度内的深度分辨小于1.5μm,表面可达约20 nm,其探测灵敏度约5×1019 D/m^2。该方法的分析误差除统计及拟合误差外,还包含±7.5%的实验参数测量误差。

To fulfill the need of studying the deuterium retention in nuclear materials, the authors set up an NRA to analyze device with three channel detecting system based on 4.5 MV electrostatic accelerator in Peking University, and developed a multi-energies NRA method for quantitative depth profiling deuterium. With the simultaneous energy spectra of p and ^4He created by the D （^3He, p）^4He nuclear reaction, by adopting several different incident ^3He^＋ energies （0.8-3.6 MeV）, a reasonable better depth resolution and higher sensitivity in a larger analyzing depth could be obtained. The authors also measured differential cross-section of the 3He-D reaction at 135°. The relative accuracy of these data was better than ±3.9%. The initial measurement of concentration and depth profiles of D was carried out, using targets of implanted PC-W samples, as well as CMSII- W samples from a W-coated outer divertor tile of TOKAMAK AUG near the strike points. A -6 μm analyzed depth could be obtained with a depth resolution less than 1.5 μm throughout the whole detecting range and a -20 nm minimal resolution at the sample surfaces. The detection limit was around 5×10^19 D/m^2. Apart from the statistical and fitting error of NRA spectra, the NRA system had an experimental error of ±7.5% from the parameter measurement.