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A new technique is proposed for an internal calibration of a two-layer detector assembly. Spatially coincident pairs of conical tracks on one surface and overetched tracks on the adjacent surface are selected for measurement. Both the etch rate ratio and the particle range can be obtained from the minor and major diameters of the elliptical track and the radii of the circular tracks for two etching steps. This technique was applied to CR-39 detectors exposed to fast neutrons and those flown on a high altitude balloon in order to evaluate the proton response. An improvement by using multi-step etching was also carried out. It was found that not only a single set of the etch rate ratio and the range but also the response curve could be estimated in an extended region by analyzing combined growth curves.

A summary of measurements of high-LET particle radiation inside U.S. manned spacecraft is given for ASTP (Apollo Soyuz Test Project), Skylab and Apollo missions. The results include particle fluxes, integral LET spectra, and stopping-density charge distributions derived from measurements made in plastic nuclear track detectors worn by astronauts and located at various positions inside spacecraft. The results presented for different missions cover a wide range of shielding depth and missions type.

The radiation environment inside Spacelab 1 was measured by a set of passive radiation detectors distributed throughout the volume inside the module, in the access tunnel, and outside on the pallet. Measurements of the low-LET (linear energy transfer) component obtained from the thermoluminescence detectors ranged from 102 to 190 millirads, yielding an average low-LET dose rate of 11.2 millirads per day inside the module, about twice the low-LET dose rate measured on previous flights of the space shuttle. Because of the higher inclination of the orbit (57 degrees versus 28.5 degrees for previous shuttle flights), substantial fluxes of highly ionizing HZE particles (high charge and energy galactic cosmic rays were observed, yielding an overall average mission dose-equivalent of about 150 millirems, more than three times higher than measured on previous shuttle missions.

On the Apollo and Skylab missions the high energy heavy ion (HZE) flux was measured by means of plastic nuclear track detectors. Measurements involve the fluxes of high linear energy transfer (LET), 6 < or approximately Z < or approximately 26 particles incident on astronauts and on several biological experiments. Partial results of these measurements are presented; the effects of shielding and solar modulation are discussed.