1 - IAEA Nuclear Data Services

5.2 Semiconductor Spectrometers
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W. Michaelis, F, Horsch, D. Lange, 0. Meyer, TI. Tamm
5.2.1 Detector Technology
Coaxial Li-drifted germanium detectors have been fabricated with
active volumes up to 33 cm £1J r . The energy resolution (3.3 keV
for Bcv = 662 keV) is comparable with the energy resolution of planar
detectors. The time distribution has been investigated for various
detector shapes (circular and trapezoidal cross section, one open
end and double-open end detectors).
High-resolution particle detectors are now produced by ion-implantation
technique £"2.J* The improved performance of these counters is due
to the fact that well-channeled ions at relative low energy and low
ion-concentration minimize bulk damage effects. High-resistivity
n-type, p-type and intrinsic germanium and silicon have been bombar­
ded with ions of more than 30 elements in the energy range between
+ +
5 and 10 keV ¿ 3.y. The properties of large-area n and p contacts
produced in this way have been studied in detail. Very thin entrance
windows are obtained by ion-implantation.
The gamma-ray response characteristics of lithium-drifted germanium
detectors have been determined experimentally for several detector
geometries J^^J*
5*2.2 Electronic Instrumentation
For high-resolution studies preamplifiers with cooled paralleled
field-effect transistors have been applied with great success £~5_7.
A pulse-shape discrimation circuit has been developed which is
sensitive to a slow time-constant component in the charge carrier
collection of lithium-drifted germanium detectors /J~6_7. Pre­
amplifier output pulses containing such a component are rejected.
By this method the spectrum shapes can be improved considerably.