Development of a Minicomputer System for on-Line Processing of gamma--Gamma Coincidence Events and Measurements of E2/M1Mixing Ratios in exp 110Cd and exp 134Ba.

摘要

A megachannel pulse-height analysis system using a 32,000-word PDP-8/E minicomputer and two moving-head disk memories was developed. The system has a storage capacity of 2exp 18events at any of 2exp 20data locations,is capable of processing 1,040events/s,and provides on-line sorting and disk storage. An X-or Y-pulse-height spectrum in coincidence with one to four arithmetically combined pulse-height windows can be assembled in core for scope display and spectral analysis within 2to 20seconds. The software for the system was written extensively in machine language. Excellent energy and timing resolution were achieved. An energy resolution of 2.3keV fwhm and a timing resolution of 8.5ns fwhm were obtained for exp 60Co at a singles rate of 10,000counts/s. The prompt timing peak remained Gaussian down to the fwtm by gating the TAC with SCAs which discriminated against low-energy events. The coincidence electronics also allowed on-line subtraction of accidental coincidence events. Alignment of the detectors and tests of the system's performance were made by measuring solid-angle correction factors for the Ge(Li) detectors through the correlation measurements of the 0exp + --2exp + --0exp +cascade in exp 106Pd,and by measuring the angular spread of positron annihilation radiation coincidences. These experimental results were in excellent agreement with theoretical solid-angle correction factors calculated. Directional correlation data were obtained for gamma-ray cascades in exp 134Ba and exp 110Cd. Analyses of these data gave E2/M1mixing ratios which are in excellent agreement with results obtained by other investigators. The improved resolution and data processing capabilities of this system gave new results for the 563-keV transition in exp 134Ba and the 1505-keV transition in exp 110Cd. E2/M1mixing ratios of 13.3/sup +2.3/sub -1.8/for the 563-keV transition and -1.24 +- 0.20for the 1505-keV transition were measured. (ERA citation 03:013205)