一种用于波长色散X射线荧光光谱仪的流气式正比计数器的研制

Development of a flow-gas proportional counter for wavelength dispersive X-ray fluorescence spectrometer

流气式正比计数器(F-PC)是波长色散X射线荧光光谱仪(WDXRF)常用的探测器。传统的F-PC一般采用1~6μm的镀铝聚丙烯薄膜作为光窗,采用模拟运放进行信号放大,存在X射线透过率低、光窗耐久度差、信号放大倍数不可调等问题。基于具有金属网格支撑的0.6μm镀铝聚丙烯膜、数字可调信号放大技术,研制了一种可在真空中使用的F-PC,提高了X射线透过率和薄膜的耐久度,实现了阳极脉冲信号放大倍数连续可调。将上述F-PC用于顺序式波长色散X射线荧光光谱仪,依照国家计量检定规程JJG810—1993对整机进行了精密度、稳定性、探测器分辨率的考察。精密度考察发现,纯铝块样品中AlKα计数值的相对标准偏差(RSD,n=20)为0.086%;稳定性考察发现,铬镍不锈钢块样品中NiKα计数值的相对极差(n=400)为0.193%;使用纯铝块样品计算F-PC能量分辨率R为39.03%。以上结果均达到该检定规程中A级指标要求。

The flow-gas proportional counter (F-PC) is the common detector for wavelength dispersive X-ray fluorescence spectrometer (WDXRF). For the conventional F-PC, 1-6 μm aluminum-coated polypropylene film was usually employed as the window. The simulation operational amplifier was used for signal amplification. It has some problems such as low transmittance of X-ray, poor durability of window and nonadjustable signal amplification factor. A kind of F-PC which could be used in vacuum was developed based on 0.6 μm aluminum-coated polypropylene film with metal grid support and digital adjustable signal amplification technique. The transmittance of X-ray and durability of film were improved, realizing the continuous adjustment of amplification of anode pulse signal. The developed F-PC was applied for sequential wavelength dispersive X-ray fluorescence spectrometer. The precision, stability of instrument and resolution of detector were investigated according to the national metrology verification regulation JJG 810-1993. The precision test indicated that the relative standard deviation (RSD, n =20) of AlKα count value in pure aluminum sample was 0.086%. The stability test indicated that the relative range ( n =400) of NiKα count value in chromium nickel stainless steel sample was 0.193%. The energy resolution ( R ) of F-PC calculated by pure aluminum sample was 39.03%. The results above could meet A-level index requirement in verification regulation.