Imaging Neutron Activation Analysis

这个小型企业创新研究(SBIR)第一阶段项目是在分析和表面化学的一般领域，以及痕量表面分析的子领域。这项活动的主旨是建造和测试成像中子活化分析探测器，该探测器能够逐点辨别元素浓度。中子活化分析是测量各种样品中主要、次要和痕量元素浓度的一种非常有效的方法。在这种方法中，被分析元素吸收一个中子形成放射性核素，通常通过发射B粒子和伽马射线来衰变。伽马射线能量是分析物元素的特征，通常用锗探测器进行测量。当B粒子从薄样品中通过时，样品表面产生的二次电子可以被加速和成像。当伽马射线和B粒子被同时探测到时，伽马射线能量回答了“什么”的问题，二次电子位置回答了单个放射性核素解体的“在哪里”的问题。这些信息将被组织到元素图和局部区域伽马射线谱中。这项研究的成功开展将有助于将成像中子活化分析应用于非均质固体的表征。在第二阶段的成功工作之后，可以预期在地质学、生物学、材料科学和颗粒分析等领域的广泛应用。

This Small Business Innovation Research (SBIR) Phase I project is in the general area of analytical and surface chemistry and in the subfield of trace surface analysis. The thrust of this activity is the construction and testing of an imaging neutron activation analysis detector capable of discerning element concentrations on a point by point basis. Neutron activation analysis is an extremely powerful method for measuring major, minor, and trace element concentrations in a wide variety of samples. In this method, analyte elements absorb a neutron to form a radionuclide which usually decays by emitting a B particle and a gamma ray. The gamma ray energies are characteristic of the analyte element and they are normally measured with a germanium detector. Secondary electrons produced at a sample surface as a B-particle passes out of a thin sample can be accelerated and imaged. When gamma rays and B-particles are detected in coincidence, the gamma ray energy answers the question "what" and the secondary electron position answers the question "where" for an individual radionuclide disintegration. This information will be organized into element maps and local area gamma ray spectra. Successful pursuit of this research should facilitate the application of imaging neutron activation analysis to the characterization of heterogeneous solids. Following a coupled successful Phase II effort, widespread applications in fields such as geology, biology, materials science, and particle analysis can be anticipated.