Frederick S. Goulding

Simultaneous ballistic deficit immunity and resilience to parallel noise sources: A new pulse shaping technique

A new and different time variant pulse processing system has been developed based on a simple CR-RC filter and two analog switches. The new pulse processing technique combines both ballistic deficit immunity and resilience to parallel noise without a significant compromise to the low energy resolution, generally considered a mutually exclusive requirement. The filter is realized by combining two different pulse-shaping techniques. One of the techniques creates a low rate of curvature at the pulse peak, which reduces ballistic deficit, while the second technique increases the tolerance to low frequency noise by modifying the noise history. Several experimental measurements are presented, including tests on a co-planar grid CdZnTe detector. Improvements on both the resolution and line shape are shown for the 662 keV line of /sup 137/Cs.

Status and problems of semiconductor detectors

J U —HIB LBL-12380 Lawrence Berkeley Laboratory UNIVERSITY OF CALIFORNIA Engineering & Technical Services Division wtftt Presented at the 1981 International Nuclear Society, International Symposivim on Nuclear Radiation Detectors, Tokyo, Japan, March 23-26, 1981 STATUS AND PROBLEMS OF SEMICONDUCTOR DETECTORS Jack T. Walton, Frederick S. Goulding, Eugene E. Haller, and Richard H. Pehl March 1981 Prepared for ths U.S. Department of Energy under Contract W-740S-ENQ-48 mmmttmmBmnumm*

Bipolar pulsed reset for AC coupled charge-sensitive preamplifiers

A new type of charge restoration is described for use particularly in germanium gamma-ray spectrometers for accelerator and space physics applications. A bipolar pulsed reset technique is applied to these applications for the first time. This technique overcomes the problems introduced by the need here to AC couple detectors and the fact that very large energy depositions occur due to charged particles present in substantial fluxes, particularly in space. The circuit is described and experimental results are presented and discussed.

A Germanium Field-Effect Transistors Made from a High-Purity Substrate

Field effect transistors have been fabricated on high-purity germanium substrates using low temperature technology. The aim of this work is to preserve the low density of trapping centers in high-quality starting material by low temperature (<350°C) processing. The use of germanium promises to eliminate some of the traps which cause generation-recombination noise in silicon field effect transistors (FETs) at low temperatures. Typically, the transconductance (gm) in the germanium FETs is 10 mA/V and the gate leakage can be less than 10-12 A. Our present devices exhibit a large 1/f noise component and most of this noise must be eliminated if they are to be competitive with silicon FETs commonly used in high-resolution nuclear spectrometers.