ABSOLUTE DISINTEGRATION RATES BY GAMMA RAY SPECTROSCOPY AND COMPUTER ANALYSIS
In order to use resonance detectors it was necessary to determine the absolute disintegration rates of the isotopes. Gamma spectroscopy was selected to allow discrimination against impurities and competing reactions by analyzing energy as well as half life. The gamma spectrometer consists of a NaI (Tl) crystal, integrally mounted on a photomultiplier tube. Voltage is supplied to each dynode by individual batteries. The signal taken from the anode is preamplified by a cathode follower built with metallic resistors for stability. The voltage signal is pulse height analyzed. To determine absolute efffciencies of the system for various gamma energies, five sources of different energies and known disintegration rates were counted in the series of geometries to be used. The observed distributions were fitted by a digital computer code to a gaussian curve by a weighted least-squares technique. To establish a consistent method of determining the photopeak area, each gaussiau curve was integrated from minus infinity to plus infinity. The gamma spectrum of the elements activated was recorded and the photopeak count-rate was used in conjunction with branching ratio data to determine the disintegration rate. Coincidence losses were accounted for by counting at various positions. Neutron capture rates at the resonance energy were deduced from these disintegration rates, together with available data on the parameters of the resonance, the 2200-m/sec cross section, and a separate measurement of the 1/v flux by means of copper wires. To check the reliability and internal consistency of the entire resonance-activation technique, a set of wires was activated in an equilibrium graphite spectrum, and the indium and gold activation rates were taken as standards against which the activation rates of the other materials were compared. (auth)
- Research Organization:
- General Electric Co., Pleasanton, Calif.
- NSA Number:
- NSA-17-038995
- OSTI ID:
- 4628804
- Journal Information:
- Proc., Intern. Conf., Mod. Trends Activation Anal., College Station, Tex., Journal Name: Proc., Intern. Conf., Mod. Trends Activation Anal., College Station, Tex.
- Country of Publication:
- Country unknown/Code not available
- Language:
- English
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