DIRECTIONAL SENSITIVITY AND ENERGY DEPENDENCE OF THE GEMINI DOSIMETRY SYSTEM.

The Type 1 and Type 5 tissue-equivalent ionization chambers TEIC flown on GT-4 have been evaluated experimentally for exposure to X rays, cobalt60 gamma rays, and Sr Y90 beta rays. The directional sensitivity to various X-ray beams was determined for each instrument. Analysis of the data showed that the Type 1 is very closely omnidirectional in response for medium and hard X rays but that the Type 5 instrument does not respond as effectively as the Type 1 instrument. It was also found that a 18-in. brass shield around the Type 1 sensor is extremely effective in decreasing the response of the chamber to X rays of medium and low energy. Data from the beta ray exposures were somewhat difficult to reconcile with theory but agreed well with independent experimental data. A number of thermoluminescent passive dosimeters were exposed along with the Type 1 chamber and comparisons of response to beams of different quality were made. Finally, future expierment goals in view of the present results are discussed. Author