NUCLEAR EMULSION

The objective of the flight was to search for solar gamma rays above 20 Mev near the peak of the solar cycle 19 using nuclear emulsions. The flight was a cooperative effort between the Case Institute of Technology from Cleveland, Ohio and the Los Alamos Scientific Laboratory, from New Mexico.

The gamma-ray detector was a nuclear emulsion stack composed by 100 Ilford G-5 pellicles measuring 7 cm x 14 cm and with a thickness of 600 microns. The emulsion technique was selected as the detector because it provided both good spatial resolution and good energy resolution. The electron-positron pair was practically a unique event in the emulsion, and, therefore, a low-intensity gamma-ray signal could be detected in the presence of a much more intense charged-particle flux.

The nuclear emulsion stack remained fixed with respect to the celestial sphere thanks to an orienting system which counteracted the rotation of the earth and the rotation of the balloon about the zenith. The system consisted of a servo drive about the zenith plus a clock-driven 24-hour rotation about an axis inclined at 54.3º to the zenith direction. The correction signal for the zenith rotation was supplied by two balanced phototransistors that gave an error signal whenever the solar orientation drifted. The orientation was continuously monitored by a pinhole camera that advanced a frame every 15 minutes.

Balloon launched on: 3/16/1959 at ~ 14:00 utc
Launch site: Los Alamos, New Mexico, US  
Balloon launched by: ?
Balloon manufacturer/size/composition: Zero Pressure Balloon  
End of flight (L for landing time, W for last contact, otherwise termination time): 3/17/1959 at 1:45 utc
Balloon flight duration (F: time at float only, otherwise total flight time in d:days / h:hours or m:minutes - ): ~ 11 h

• Search for solar and cosmic gamma rays Journal of Geophysical Research, 71(13), 3119 (1966)