The effect of simulated Nimbus spacecraft orbital (1100 km, circular, and polar) radiation on wide-band-pass glass filters, narrow-bandpass thin-film interference filters, and several fused silicas was determined by transmittance measurements over the 200-3400-nm wavelength region. No changes were observed in the filters, which were shielded with fused silica during irradiation, after exposure to a 1-yr equivalent orbital dose of electrons, nor were changes observed in the fused silicas after the same electron exposure plus a 1-yr equivalent dose of protons. Exposure to a (1/2)-yr equivalent dose of solar uv radiation, however, caused a significant degradation in the transmittance of two uv-transmitting interference filters but had no effect on two colored glass filters that transmitted in the visible and near-ir regions. As a result of the uv exposure, the fused silicas exhibited losses of several percent over the 200-300-nm wavelength region.

The variation of grain density in the tracks of 5-, 8-, 12-, and 24-GeV/c protons incident at angles of 75°, 60°, 50°, and 40°, respectively, and of 5-GeV/c pions incident at an angle of 75° to the edge of the plate has been investigated as a function of velocity in the same Ilford G-5 pellicle. About 80 000 blobs were counted for each beam. The ratio of grain densities at 5-GeV/c pion to proton is ~1.114=fc0.01. The results are in agreement with the Sternheimer theory using an ionization potential for AgBr of 434 eV and a cutoff energy To of 2-5 keV, which is in contradiction with the result due to Jongejans (who uses the cutoff energy To = 100 keV), but in agreement with Shapiro's result (T 0 between 2 and 5 keV) and with Barkas's result (with 0-10% correction due to secondary ionization). The data are also consistent with the slow rate of rise in the g* value as a function of velocity which is predicted by the theory.

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