Measurement of energies and intensities of multiple ionization satellite (MIS) excited in light elements by helium ion beams

TNA project number: 19001708-ST Measurement of energies and intensities of multiple ionization satellite (MIS) excited in light elements by helium ion beams Scientific background: Over 1600 X-ray spectra have been collected from the alpha particle X-ray spectrometers on Mars rovers including the present Curiosity rover. The spectra are excited by the radionuclide 244Cm, which emits 5 MeV He ions for PIXE and Pu L X-rays for XRF. These spectra provide elemental analysis of rocks, soils and dust as part of the quest to identify formerly habitable (water-bearing) environments. Applicant is a member of the Curiosity APXS team within NASA’s Mars Science Laboratory. Excitation of K X-rays by 5 MeV He ions produces also energy-shifted satellites due to 1, 2 or 3 L-shell spectator vacancies. These cause significant distortion of the diagram lines and worsen the quality of spectrum fits by the GUPIX(Mars) code. An MIS database is needed to support a correction procedure that is already devised. This work will increase analytical accuracy and will also support more accurate terrestrial PIXE analysis using alpha beams, especially when partnered with RBS; this could lead to increased use of these two IBA methods in a complementary manner. Measurements performed within TNA project: The wavelength-dispersive in-vacuum x-ray spectrometer of J. Stefan Institute (Ljubljana, Slovenia) [1] have been used to record high energy resolution KaLN X-ray spectra of Ca and Cr induced in collisions with MeV alpha particles. The targets used were metallic Cr, Cr2O3, and CaF2. The KaLN X-ray spectra of Cr and Cr2O3 were measured using three different energies of He ions, namely 3 MeV, 4 MeV and 5 MeV. For CaF2 we have collected only spectra induced with 5 MeV He beam. The main purpose of the experiment was to record KaLN spectra with good enough statistics to determine precisely energy/intensity of the corresponding satellite lines. The results for the energy shifts and relative intensities of the groups will be incorporated in the MIS database providing an empirical means for inclusion of one peak per satellite group when modelling energy-dispersive spectra (GUPIX(Mars) code). [1] M. Kavčič, M. Budnar, A. Mühleisen, F. Gasser, M. Žitnik, K. Bučar, R. Bohinc, Design and performance of a versatile curved-crystal spectrometer for high-resolution spectroscopy in the tender x-ray range, Rev. Sci. Instr. 83, 033113 (2012). http://dx.doi.org/10.1063/1.3697862 Data files: We are sharing the detector files (a series of single exposure 2D raw images) collected by the Andor DX438-BV CCD camera (770 × 1152 pixels with pixel size 22.5×22.5 μm2) after the diffraction on the crystal analyzer. The horizontal axis of the detector corresponds to the dispersion axis and diffracted photons are detected at different horizontal positions according to their wavelength, the vertical axis of the detector serves mainly to accumulate more statistics. The final emission spectra are obtained from the corresponding detector files using the home-written data processing software.TNA项目编号：19001708-ST，主题为氦离子束轰击轻元素产生的多电离卫星峰（Multiple Ionization Satellite, MIS）的能量与强度测量。 科学背景：火星漫游车（含当前的好奇号漫游车）搭载的α粒子X射线光谱仪已收集超过1600组X射线能谱，这些能谱由放射性核素²⁴⁴Cm激发：该核素会发射用于质子激发X射线荧光分析（PIXE）的5MeV氦离子，以及用于X射线荧光光谱法（XRF）的钚L系X射线。此类能谱可用于岩石、土壤与尘埃的元素分析，助力识别曾具备宜居性（含水）的火星环境。本项目申请人为NASA火星科学实验室任务中好奇号APXS（α粒子X射线光谱仪）团队成员。当5MeV氦离子激发K系X射线时，还会因L壳层存在1、2或3个旁观空位产生能量偏移的卫星峰，此类峰会显著扭曲特征谱线，降低GUPIX(Mars)代码拟合能谱的精度。目前已开发出相关校正程序，但亟需一套MIS数据库以支撑该校正流程。本研究不仅可提升分析精度，还能助力使用氦离子束的地面PIXE分析（尤其是与卢瑟福背散射光谱法（RBS）联用时），有望推动两种离子束分析（IBA）方法的互补应用。 TNA项目内实验工作：使用斯洛文尼亚卢布尔雅那约瑟夫·斯特凡研究所的真空波长色散X射线光谱仪[1]，记录了MeV级α粒子轰击钙（Ca）与铬（Cr）产生的高能量分辨率KaLN系X射线能谱。实验靶材包括金属铬、三氧化二铬（Cr₂O₃）以及氟化钙（CaF₂）：针对铬与三氧化二铬靶，分别采用3MeV、4MeV、5MeV三种能量的氦离子束激发并采集KaLN能谱；针对氟化钙靶，仅采集了5MeV氦离子束激发的能谱。本实验的核心目标是获取统计性良好的KaLN能谱，以精确测定对应卫星峰的能量与相对强度。本研究得到的能量偏移量与峰组相对强度数据，将被整合至MIS数据库，为使用GUPIX(Mars)代码建模能量色散能谱时，为每个卫星峰组添加单峰校正提供经验依据。[1] M. Kavčič, M. Budnar, A. Mühleisen, F. Gasser, M. Žitnik, K. Bučar, R. Bohinc, 《用于软X射线范围高分辨率光谱的多功能弯晶光谱仪设计与性能》，Rev. Sci. Instr. 83, 033113 (2012). https://dx.doi.org/10.1063/1.3697862 数据文件：本次共享的是Andor DX438-BV型CCD相机采集的探测器原始数据文件（一系列单次曝光的二维原始图像），该相机分辨率为770×1152像素，像素尺寸为22.5×22.5μm²，数据采集于晶体分析仪衍射之后。探测器的横轴对应色散轴，衍射光子会根据其波长在不同的水平位置被探测；纵轴主要用于累积更多统计数据。最终的发射能谱将通过自研的数据处理软件，从对应的探测器原始文件中提取得到。