X射线吸收光谱技术中的滤光片研制

在同步辐射X射线吸收光谱(XAS)实验中,X射线滤光片用于吸收样品的康普顿散射和弹性散射,改善荧光信号的质量。我们将ZnO颗粒分散在聚氨酯溶液里,通过恰当的喷涂工艺,获得ZnO滤片。X射线衍射(XRD),X射线荧光(XRF)及X射线吸收光谱(XAS)实验结果表明：在滤片制备过程中,ZnO结构保持不变。进一步地,ZnO滤片用于测量Ga2O3的GaK边XAS谱,显示出好的信噪比。采用同样的方法还制备了其它X射线滤光片,表明这种X射线滤光片制备技术的可行性和实用性。     

高功率Z箍缩软X射线功率测量

针对“强光一号”装置喷氪气高功率Z箍缩等离子体实验产生1keV以下的软X射线，研制了脉冲恒压电源驱动的镍薄膜量热计，测量Z箍缩软X射线总能量，用快时间响应的X射线二极管(XRD)探测器建立了软X射线功率测量系统，给出了实验测量结果。     

胶片扫描法对低能X射线标准辐射场的研究

采用胶片剂量计测量了低能X射线辐射装置距X射线光管焦斑不同距离辐射野的大小,得出在距离光管焦斑1 000 mm的参考面辐射野大小及均匀性,并与二维矩阵电离室扫描结果进行了对比。实验结果表明,在距X射线光源焦斑1 000 mm处,在保证直径为100 mm的均匀野的条件下,非均匀性不大于1.5%。在保证非均匀性不大于5%和50%条件下,均匀野大小分别为130 mm和145 mm,满足了低能X射线空气比释动能基准装置量值复现,国际比对和向下量值传递的要求。     

X光管滤光片效应的蒙特卡罗仿真

在X射线荧光分析中,使用滤光片可有效降低原级光谱本底对待测元素的干扰,提高分析灵敏度。本文采用MCNP5方法仿真X光管滤光片对原级谱线的影响,比较了滤光片对不同能量电子束产生的X射线谱的差异,分析了不同滤光片材料及厚度与X射线原级谱衰减的关系,得到不同滤光片对X射线谱的衰减规律。     

四路并联二极管辐射X射线场参数计算

利用二极管的电压、电流计算了发射电子束能谱参数,建立了四路并联二极管阳极靶蒙特卡罗粒子输运计算模型,给出了辐射X射线场参数;将四路并联二极管的每个二极管划分为若干小单元,将其作为点源,采用数值积分的方法计算了辐射X射线剂量分布,并分析了空间不同位置处每路二极管对剂量的贡献。结果表明:真空中,距离四路并联二极管阳极靶5cm位置处,X射线注量为3.55mJ/cm2,光子平均能量为62.18keV,120keV以下的光子占辐射X射线谱总能量的81.84%,电子束转换效率为0.30%;在2 700cm2范围内,中轴线和对角线上的剂量均匀性分别为3.20和6.31;在2 000cm2范围内,中轴线和对角线上的剂量均匀性均小于2。     

球载大面积Phoswich能量分辨率研究

对混合型球载硬Ｘ射线天文望远镜（ＨＡＰＩ－４）ＰｈｏｓｗｉｃｈＮａＩ（Ｔｌ）／ＣｓＩ（Ｎａ）探测器的能量分辨率进行了研究。实测表明,光电倍增管光阴极面响应的非均匀性与入射光谱有关,用蓝色滤光片所测非均匀性小于２０％,采用对晶体窗玻璃进行罩膜处理,改变荧光收集条件,以牺牲幅度换取均匀性能量分辨率的改善效果是十分明显的,可将Ｐｈｏｓｗｉｃｈ探测器能量分辨从４５％（６０ｋｅＶ）提高到２４％,此外,对几种     

替代241Am低能光子源的准单色X射线机的研制

研究了用滤光片法产生50～60 keV的准单色X射线的条件,对输出的X射线进行了数种金属滤光片实验研究,选出合适的滤光片,通过实验对准直器的机械结构进行了确定。采用自行设计委托加工的X射线管、准直器和购买的高压电源,组装成符合实验要求的X射机。该装置输出了50～60 keV能量段的准单色光谱,在料位计上能替代²⁴¹Am低能光子源。     

X射线线阵列探测器数字图像的非均匀性原因分析

在论述X射线线阵列探测器辐射数字成像系统的基础上，对X射线线阵列探测器辐射数字成像系统获取的图像的非均匀性产生机理进行了理论分析，并在理论分析基础上从测量和校正的角度对各种非均匀性产生因素进行了分类，以便对图像的非均匀性校正的方法及减小图像非均匀性产生的技术途径。     

过滤X射线参考辐射场特性的蒙特卡罗模拟研究及实验验证

为研究过滤X射线参考辐射场特性,利用蒙特卡罗方法对中国原子能科学研究院计量测试部过滤X射线参考辐射场的原级谱、均匀性及散射辐射进行了模拟,并利用PTW球形电离室进行了实验测量。结果表明,蒙特卡罗模拟结果与实验结果符合较好,验证了所建模型的正确性及蒙特卡罗方法对模拟过滤X射线参考辐射场的有效性,为后续模拟研究工作奠定了基础。     

中能X射线标准辐射场的初步研究

采用石墨空腔电离室NE2561测量了中能X射线标准辐射场各点的剂量率,结果显示在非均匀性不大于1%的条件下,离X射线管焦斑1 200 mm处得到直径约为45 mm的均匀场。采用内插法测量80 kV能量点过滤X射线参考辐射束的第一半值层和第二半值层。结果显示辐射场均匀性和辐射质均符合ISO 4037的要求。     

滤光片对透射式微型X光管谱线影响的MC数值模拟分析

现场X射线荧光分析(EDXRF)中,使用滤光片可以有效的降低或消除由原级谱在样品中散射背景,特征谱对待测元素的干扰。论文采用MCNP5程序模拟了加不同厚度Al、Cu、Ag、Kapton滤光片前后的原级谱分布。依据模拟结果,原级X射线谱的谱分布与滤光片的材质和厚度有关。能量低于5ke V的射线对分析是无用的。在能量5~10 ke V的能量谱段,选择Al滤光片较为合适;在能量10~25ke V谱段范围,Ag滤光片相对于另外三种滤光片较为合适。从而为现场X荧光分析仪的研制提供技术支撑。     

Elongate X-ray detectors for application in security inspectionsystems

We have developed, manufactured, and investigated a novel type of long X-ray detector up to 1000 mm long with two exit windows. The sensitive element of the detector is an elongated polished rectangular plate of inorganic scintillator. The detector is highly sensitive to X-rays in the energy region 50-250 keV. The factors influencing the sensitivity and longitudinal uniformity of the detector response have been considered     

The effects of intense gamma-irradiation on the alpha-particle response of silicon carbide semiconductor radiation detectors

Silicon Carbide (SiC) semiconductor radiation detectors are being developed for alpha-particle, X-ray and Gamma-ray, and fast-neutron energy spectrometry. SiC detectors have been operated at temperatures up to 306 °C and have also been found to be highly resistant to the radiation effects of fast-neutron and charged-particle bombardments. In the present work, the alpha-particle response of a SiC detector based on a Schottky diode design has been carefully monitored as a function of ¹³⁷Cs gamma-ray exposure. The changes in response have been found to be negligible for gamma exposures up to and including 5.4 MGy, and irradiations to higher doses are in progress.     

Development of X-ray dark-field imaging towards clinical application

Review of X-ray dark-field imaging under development is presented. Its goal is its application to clini-cal diagnosis of organs that have been invisible by the ordinary techniques. In order to clinically visualize tissues in detail one needs high contrast and high spatial resolution say～50μm. This X-ray optics comprises a Bragg asymmet-ric monochro-collimator and a Bragg case or a Laue case filter with capability of analyzing angle in a parallel posi-tion. Their diffraction index is 4,4,0 and the X-ray energy 35 keV (λ=0.0354 nm). The filter has 0.6 mm thickness in the Bragg case or 1.075 mm or 2.15 mm thickness in the Laue case. Under this condition only the refracted X-rays from object can transmit through the filter while the beam that may receive absorption and/or phase change will not.Soft tissues at human joints thus taken show high contrast images so that the DFI is promising for clinical diagnosis.Preliminary X-ray absorption images of another clinical candidates of ear bones are also shown.     

Response of Si p-i-n diode and Au/n-Si surface barrier detector to heavy ions

Pulse height versus energy calibrations of a Si p-i-n diode and a Au-/n-Si surface barrier detector have been studied for heavy ions with atomic number (Z₁) from 3 to 79 in a range from 0.1 to 0.8 MeV per nucleon as a function of bias voltage and detector tilting angle. The detector response is simultaneously measured using a time of flight-energy elastic recoil detection analysis set-up with recoils produced over a wide energy range from a thick target of each element. Prior to impinging on the Si detector, the individual recoil is tagged by its energy determined from the time of flight and tabulated isotopic mass. For both detectors, the pulse height-energy calibration for recoils with a given Z₁ is described well by a linear relationship with small systematic deviations. The linear-fit parameters show similar, but not identical dependence on both Z₁ and bias voltage (collecting field strength) for the surface barrier detectors and the p-i-n diode. These results suggest that the efficiency of electron–hole pair collection is markedly dependent on the different electric field configurations for the two detector structures.     

Surface contamination of the charge－coupled device

An experimental method to study the influence of surface contamination of a thinned.backside illuminated charge-coupled device(CCD) upon its quantum efficiency in soft X-ray region is suggested.A transmission grating spectrometer(TGS),in which the transmission grating is coupled to a thinned.backside illuminated charge coupled device,is used to measure the continuum X-ray emission from the end of cylindrical target irradiated by laser.In the meausred spectra,only the carbon K absorption edge at wavelength of 4.4nm due to condensation of the vacuum oil on the CCD surface is clearly seen.The surface contamination is considered as an effective “carbon filter” and the filter absorption to correct the quantum efficiency of the CCD camera is taken into account.The effective thickness of the carbon filter is determined by comparing the jump height of the measured spectra at 4.4nm with those of the carbon absorption coefficient curves obtained from various carbon thickness.The accuracy of this method is tested by comparing the X-ray spectrum measured by the TGS with that obtained by a soft X-ray spectrometer.     

位敏电离室测X光强分布

用多收集电极的位置灵敏电离室测量了光刻用8光斑的均匀性分布及其总强度。实验结果表明该系统结构简单性能稳定,可推广应用到其他X光测量系统中去。     

The background calculation of the filter-fluorescer method

For the measurement of X-ray energy spectrum with filter-fluorescer method,the high energy tail at the rearward of response function is the main source of background.There are,traditionally,two techniques for measuring the background contributions:the same element Z for the fluorescer and filter,or the same element Z?1 for them.Using the formula of fluorescence intensity,and the elemental combinations of cobalt and iron,the backgrounds which the two techniques provide and the real one for measuring black-body radiation at equilibrium temperature of 7×106 K,were calculated.The results show that the Co-Co combination for the filter-fluorescer spectrometer can achieve better effect.A semi-quantitative analysis for the calculation results is discussed.