THE ANGULAR AND ENERGY DISTRIBUTION OF ALUMINUM PHOTOPROTONS
The energy and angnlar distribution of photoprotons from aluminum was measured for protons in the energy range, 8 to 25 Mev. A collimated bremsstrahlung beam from the University of Virginia's 65 Mev synchrotron was used as a source of gamma radiation, with a maximum gamma energy of 63 plus or minus 0.5 Mev for all measurements. Photoprotons were counted by two silicon p-n junction detectors arranged as a summing counter. The energy response of the summing counter for protons was essentially linear for energies from 4 to 11 Mev. To extend the energy range of the measurements, and eliminate the effect of high energy protons, aluminum energy reduction foils were placed between the target and detector. Protons were counted at detector to beam-direction angies of 40, 80, 90, and l30 deg . Angalar distributions were determined for each of several proton energy ranges, and were fitted with a curve of the form, F( theta ) = a + (bsin theta + psin theta cos theta )/sup 2/. Proton energy spectra were obtained by successive subtractions of the high energy proton contribution to each set of data, measured with a particular energy reduction foil in place. Peaks were identified at proton energies of roughly 9, 13.5, 14.7, 19 and 21 Mev. An interpretation of these results was made using the direct interaction model. Silicon p-n junction detectors used for photoproton detection were fabricated by a high temperature diffusion of phosphorus into p-type of silicon having a resistivity of about 1,300 ohmcm. Detectors were made by this process with areas of up to 2 cm/sup 2/, to which a reverse bias of 400 to 500 volts could be applied. The detectors had an energy resolution for 5.3 Mev alpha particles of the order of 1%. The summing counter was calibrated by measuring its response to the monoenergetic proton groups of about 9, 7, 4.5, and 4.2 Mev produced in the B/ sup 10/(d,p)B/sup 11/ reaction. The response of single detectors to protons was also measured. The results indicated that the width of the space charge layer (sensitive portion for charged particle detection) of the p-n junctions was greater by almost a fuctor of 2 than was calculated. No explanation of this effect was found, with the exception of a possible failure of the calculational model for high reverse bias values. (Dissertation Abstr. 23: May 1963)
- Research Organization:
- Originating Research Org. not identified
- NSA Number:
- NSA-17-026636
- OSTI ID:
- 4666413
- Country of Publication:
- Country unknown/Code not available
- Language:
- English
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