M. Ukibe et al., A LOW-NOISE CHARGE-SENSITIVE PREAMPLIFIER FOR AN X-RAY-DETECTOR OF A NB-BASED SUPERCONDUCTING TUNNEL JUNCTION, Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment, 401(2-3), 1997, pp. 299-308
A low-noise charge-sensitive preamplifier with cooled 4-JFETs was deve
loped for an X-ray detector of a Nb-based superconducting tunnel junct
ion with a large capacitance and a low leakage current. The low-noise
characteristics for a wide range of shaping times were obtained by usi
ng a selected JFET, 2SK190 in the first stage of the preamplifier. A n
ew formula to simulate the preamplifier noise was developed and applie
d ro tile optimization of preamplifier design. A high-energy resolutio
n of 66 eV for 5.9 keV X-ray and 51 eV for pulser signals was obtained
by using the optimized preamplifier with an X-ray detector of a 178 m
u m x 178 mu m Nb/Al-AlO2/Nb superconducting tunnel junction with a ju
nction capacitance of 1900pF and a bias current of 1.44nA.