Performance of an X-ray spectroscopic system based on a double-gate double-feedback charge preamplifier
A. Fazzi,P. Rehak;A. Fazzi;P. Rehak;
nuclear instruments and methods in physics research section a: accelerators, spectrometers, detectors and associated equipment1999Vol. 439pp. 391-402
84
rehak1999nuclearperformance
Abstract
The performance of a near room temperature X-ray spectroscopic system is reported. The system is based on a charge preamplifier with the first transistor having two separated gates. The preamplifier operates in a continuous reset mode without any physical resistor connected to the input node. The leakage current and the current due to the rate of X-rays is neutralized by an average current of holes, flowing under the control of an additional feedback, from the bottom to the top gate. The preamplifier is followed by a simple circuit which exactly cancels the long tail of the impulse response of a pure double-gate preamplifier. The compensation of this tail, due to the very principle of the preamplifier's continuous reset through the double-gate mechanism, improves substantially the high-rate performance of the system. The preamplifier based on a commercially available double-gate front JFET MX-40 (MOXTEK) coupled to a silicon drift detector produced at BNL achieved ENC of 13 electrons at −30°C. The analysis of the system's performance, the noise analysis and optimization are described.