Analysis of pulse shape from a high-resolution superconducting tunnel junction X-ray spectrometer
Analysis of pulse shape from a high-resolution superconducting tunnel junction X-ray spectrometer
复制标题
高分辨率超导隧道结 X 射线光谱仪的脉冲形状分析
DOI：
10.1016/0168-9002(95)01047-5
复制
发表时间：
1996
影响因子：
1.4
通讯作者：
A. Barfknecht
中科院分区：
文献类型：
--
作者：
C. Mears;S. Labov;M. Frank;M. Lindeman;M. Lindeman;L. J. Hiller;L. J. Hiller;H. Netel;A. Barfknecht
超导-绝缘-超导（SIS）隧道结与超导吸收剂耦合，可作为高分辨率、高效率的x射线光谱仪。直到最近，这种装置产生的x射线感应电流脉冲一直是使用基于fet的负反馈电荷或电流放大器来测量的。这些放大器的有限带宽和反馈特性使得很难推断出x射线感应电流脉冲的真实形状。最近，我们开始使用基于超导量子干涉器件（squid）的高带宽放大器来测量隧道结x射线光谱仪的电流脉冲。我们已经测量了来自铌x射线吸收层和铝层耦合的装置的脉冲，铝层作为准粒子陷阱。本文研究了脉冲形状随偏置电压的变化规律。一般来说，随着偏置电压的增加，x射线诱导脉冲的振幅增大，长度变长。我们发现，通过测量电流脉冲的上升时间，可以区分由顶部铌膜中的x射线吸收产生的脉冲和底部铌膜中产生的脉冲。这使我们能够仅使用底部铌膜中产生的脉冲产生高分辨率光谱。该光谱在5.89 keV下的能量分辨率为29 eV FWHM，比使用半导体电离探测器获得的能量分辨率高约5倍。
Superconducting-insulating-superconducting (SIS) tunnel junctions coupled to superconducting absorbers may be used as high-resolution, high-efficiency X-ray spectrometers. Until recently, the X-ray-induced current pulse from such devices has been measured using FET-based negative-feedback charge or current amplifiers. The limited bandwidth and feed-back nature of these amplifiers have made it difficult to deduce the true shape of the X-ray induced current pulse. Recently, we have begun to use high-bandwidth amplifiers based on Superconducting Quantum Interference Devices (SQUIDS) to measure the current pulses from our tunnel junction X-ray spectrometers. We have measured pulses from devices with niobium X-ray absorbing layers coupled to aluminum layers that serve as quasiparticle traps. We present here a study of pulse shape as a function of bias voltage. In general, the X-ray induced pulses increase in amplitude and become longer as we increase the bias voltage. We found that it is possible to differentiate pulses produced by X-ray absorption in the top niobium film from those produced in the bottom niobium film by measuring the rise time of the current pulses. This allows us to produce a high resolution spectrum using only pulses produced in the bottom niobium film. The measured energy resolution of this spectrum is 29 eV FWHM at 5.89 keV, about 5 times better than that obtainable using semiconductor ionization detectors.