No abstract

A system was developed for obtaining γ-ray spectra with high resolution at high input rates. For rates up to 100 000 γ-ray events/sec in a 3.5 cm3 (13 mm thick) Ge(Li) detector, the FWHM at 1.33 MeV is 2–3½ keV and the spectral shift is no more than 0.1%. The amplifying chain, consisting of a cooled FET preamplifier and a simple main amplifier, is pole-zero compensated throughout. The amplifier produces unipolar pulses shaped with equal integrating and differentiating time constants of 1.2 μsec. The amplifier is followed by a two-diode baseline restorer, a pileup rejector, a linear gate, and an analog to digital converter. The salient features of the system are described and performance data are presented and discussed.

A new pulse amplitude discriminator, especially suitable for counting experiments, has been developed. Ten units were built and tested, and all of the threshold temperature coefficients are in the range −0.03 to +0.12mV per °C. At very high rates the threshold is stable and the output pulse width and the dead time change negligibly. Since the unit incorporates a number of convenient features, including provision for automatic dead-time correction, it is an extremely versatile instrument.

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