A Study of X-ray Response of the TES X-ray Microcalorimeter for STEM
A Study of X-ray Response of the TES X-ray Microcalorimeter for STEM
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STEM TES X 射线微量热仪的 X 射线响应研究
DOI：
10.1109/tasc.2017.2661738
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发表时间：
2017
影响因子：
1.8
通讯作者：
Toru Hara and Keisuke Maehata
中科院分区：
文献类型：
--
作者：
Haruka Muramatsu;Tasuku Hayashi;Keisei Maehisa;Yuki Nakashima;Kazuhisa Mitsuda;Noriko Y.Yamasaki;Toru Hara and Keisuke Maehata
TES微量热计显示出非线性的脉冲高度-能量关系，反映了它们在过渡边缘的非线性电阻-温度关系。在一些TES应用中，例如能量色散X射线光谱学，需要宽的能量范围（例如0.5 - 15keV）和良好的能量校准（例如在几eV内）。研究了非线性脉冲幅度能量比的标定方法和在数据分析中的校正方法。我们用三种放射性同位素同时照射TES微量热计，获得了覆盖3.3至17.8 keV的无连续谱线谱。来自这些同位素的X射线线分别是包含精细结构和/或卫星线的线复合物，其不能用TES微量热仪完全分离。因此，特殊的治疗是必要的。本文首先建立了一种精确估计PHA（最佳滤波脉冲高度分析值）与线复合体X射线能量之间关系的方法：假定在包含一个线复合体的窄能量范围内，PHA = aE + B局部近似为线性函数，并由线复合体PHA谱的模型拟合确定a和B。然后，从六个线复合物的PHA-Energy关系，我们确定了一个近似公式，它代表了整体的PHA-Energy关系。然后，我们应用全局关系将所有脉冲的PHA值转换为能量等效值，我们称之为PI（脉冲不变量）。然后，我们用模型函数拟合PI光谱，以检查能量的一致性。我们从两种不同形式的数据开始进行这些过程; TES电流作为时间的函数，TES电阻作为时间的函数。对于TES电阻脉冲，PHA与能量的非线性较小，获得了较好的能量校准。我们发现，从TES电阻脉冲获得的PI谱再现的X射线能量在± 3 eV的不确定度，而从TES电流脉冲获得的PI谱的不确定度变得高达10 eV。
TES microcalorimeters show a nonlinear pulse-height-to-energy relation, reflecting their nonlinear resistance-to-temperature relation on the transition edge. In some of TES applications, such as energy dispersive X-ray spectroscopy, a wide energy range (e.g. 0.5-15 keV) and a good energy calibration (e.g. within a few eV) are required. We have studied the method to calibrate the nonlinear pulse-height-to-energy and to correct for it in the data analysis. We irradiated a TES microcalorimeter with three radio isotopes simultaneously to obtain continuum-free line spectra covering from 3.3 to 17.8 keV. X-ray lines from those isotopes are, respectively, a line complex containing fine structures and/or satellite lines, which cannot be fully separated with TES microcalorimeters. Thus, a special treatment is necessary. We first established a method to estimate the relation between PHA (pulse height analyzed value by optimum filtering) and X-ray energy of the line complex precisely: we assumed that the relation could be approximated with a linear function, PHA = aE +b , locally in the narrow energy range containing one of the line complex, and determined a and b from the model fit of the PHA spectrum of the line complex. Then, from the PHA-to-energy relations of six line complexes, we determined an approximation formula which represented the global PH-to-energy relation. We then applied the global relation to convert PHA values of all pulses to energy equivalent value, which we call PI (pulse invariant). We then fitted the PI spectra with the model function to check the consistency of energy. We have done these processes starting from two different forms of data; TES current as a function of time, and TES resistance as a function of time. The nonlinearity of PHA-to-energy was smaller for TES resistance pulses, and a better energy calibration is obtained. We found that the PI spectra obtained from TES resistance pulses reproduced the X-ray energies within ±3 eV uncertainty, while the uncertainties becomes as large as 10 eV for the PI spectra obtained from TES current pulses.