OPERATION SUN BEAM, SHOT SMALL BOY. Project Officer's Report - Project 7.10. Spectral Analysis with High-Time Resolution of the Thermal Radiation Pulse,
ARMY NUCLEAR EFFECTS LAB EDGEWOOD ARSENAL MD
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The primary objective of this project was to investigate the spectral irradiance and luminosity versus time for the first thermal pulse at Shot Small Boy. This was accomplished by use of spectral filters with narrow band passes, phototubes, and magnetic tape recorders with high time resolution at two locations. The measured elapsed time to the first thermal maximum was from 50 to 110 micro-seconds, depending on wavelength. A graph of radiant thermal power versus time was obtained for the thermal pulse. The delineation of the first thermal pulse, especially the rise portion, is considered to be more definite than has been obtained previously. The resolution time of the instrumentation was approximately 50 micro-seconds. Secondary objectives were to measure the total luminosity versus time and also to measure the atmospheric attenuation. These objectives were accomplished by making measurements at two distances, 2.5 and 3.5 miles, from ground zero. In the case of the total luminosity measurements, a system of filters with a spectral transmittance approximating the sensitivity response of the average human eye was used. The results are tabulated in the report.