Barbui T, Delgado-Aparicio L F, Pablant N, Disch C, Luethi B, Pilet N, Stratton B, VanMeter P
Princeton Plasma Physics Laboratory, Princeton, New Jersey 08540, USA.
DECTRIS Ltd., 5405 Baden-Daettwil, Switzerland.
Rev Sci Instrum. 2021 Feb 1;92(2):023105. doi: 10.1063/5.0040571.
A multi-energy hard x-ray pin-hole camera based on the PILATUS3 X 100K-M CdTe detector has been developed at the Princeton Plasma Physics Laboratory for installation on the Tungsten Environment in Steady State Tokamak. This camera will be employed to study thermal plasma features such as electron temperature as well as non-thermal effects such as fast electron tails produced by a lower hybrid radiofrequency current drive and the birth of runaway electrons. The innovative aspect of the system lies in the possibility of setting the threshold energy independently for each of the ∼100k pixels of the detector. This feature allows for the measurement of the x-ray emission in multiple energy ranges with adequate space and time resolution (∼1 cm, 2 ms) and coarse energy resolution. In this work, the energy dependence of each pixel was calibrated within the range 15 keV-100 keV using a tungsten x-ray tube and emission from a variety of fluorescence targets (from yttrium to uranium). The data corresponding to pairs of K emission lines are fit to the characteristic responsivity ("S-curve"), which describes the detector sensitivity across the 64 possible energy threshold values for each pixel; this novel capability is explored by fine-tuning the voltage of a six-bit digital-analog converter after the charge-sensitive amplifier for each of the ∼100k pixels. This work presents the results of the calibration including a statistical analysis. It was found that the achievable energy resolution is mainly limited by the width of the S-curve to 3 keV-10 keV for threshold energies up to 50 keV, and to ≥20 keV for energies above 60 keV.
普林斯顿等离子体物理实验室已研发出一款基于PILATUS3 X 100K-M碲化镉探测器的多能硬X射线针孔相机，用于安装在稳态托卡马克装置的钨环境中。该相机将用于研究热等离子体特征，如电子温度，以及非热效应，如下混合射频电流驱动产生的快电子尾巴和逃逸电子的产生。该系统的创新之处在于能够为探测器的约10万个像素中的每个像素独立设置阈值能量。这一特性允许在具有足够的空间和时间分辨率（约1厘米，2毫秒）以及粗略能量分辨率的多个能量范围内测量X射线发射。在这项工作中，使用钨X射线管和各种荧光靶（从钇到铀）的发射，在15 keV至100 keV范围内校准了每个像素的能量依赖性。将与K发射线对对应的数据拟合到特征响应率（“S曲线”），该曲线描述了每个像素在64个可能能量阈值下的探测器灵敏度；通过对约10万个像素中的每个像素在电荷灵敏放大器之后微调六位数字模拟转换器的电压来探索这一新颖能力。这项工作展示了校准结果，包括统计分析。结果发现，对于高达50 keV的阈值能量，可实现的能量分辨率主要受S曲线宽度限制，为3 keV至10 keV，对于高于60 keV的能量，分辨率≥20 keV。
