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RESEARCH PRODUCT

A ten-fold divided total absorption Ge(Li) gamma-ray detector

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Abstract We have constructed a split-crystal total absorption Ge(Li) gamma-ray spectrometer and special logic electronics for rejecting Compton continuum in spectra. A 10 cm3 planar detector was divided into ten electrically separated detectors by grinding nine parallel slots on the n-surface of the detector. In operation both the n- and p-contacts are isolated from the ground. Using capacitive sharing, most of the released electrical charge is taken from the p-contact into an ordinary pulse amplifier line and analyzed. A small fraction of the charge collected at the n-strips is observed with voltage-sensitive FET-preamplifiers. The following logic electronics provides a gate pulse for the analyzer if at least a two-fold coincidence with certain energy relations is found between pulses from different parts of the detector. The energy relations are nonlinearly determined by the total energy absorbed in the detector. The electronics thus effectively rejects pulses caused by single Compton scattering events. The figure-of-merit value (introduced by Cooper) of the detector was improved by a factor of 1.5 for 662 keV quanta. The improvement is significant down to energies of about 300 keV. A detailed discussion of improving the principles and applying them to large detectors is included.