A Broadband Current Preamplifier Configuration for Obtaining Htgh Resolutton Energy and Time Information from Nuclear Radiation Detectors

A broadband current preamplifier was developed to complement nuclear spectroscopy systems requiring linear gating. The preamplifier stage configuration consists of an FET input, a broadband interstage current gain section, and a high-impedance feedback network. The preamplifier produces a noise line width comparable to charge-sensitive designs having similar parameters. Because of large bandwidths and low-noise performance, the preamplifier, connected directly to a fast leading-edge discriminator, generates very accurate timing data. A preamplifier consisting of three gain stages was built and subsequently tested with Ge(Li) detectors. This preamplifier had a current gain of 10,000, a rise time of 8 nsec with a 10 pF detector capacitance, and a 0-pF noise line width, using an RC-RC ungated filter, of 1.4 keV (fwhm Ge). With the preamplifier operating from a 10 cc Ge(Li) coaxial detector, timing experiments utilizing the 60Co gamma cascade indicated resolutions as low as 1.15 nsec fwhm.