New techniques for predicting solar proton fluences for radiation effects applications.

At geosynchronous altitudes, solar proton events can be a significant source of radiation exposure for devices such as optical imagers, memories and solar cells. These events appear to occur randomly with respect to time and magnitude during the active period of each solar cycle. New probabilistic descriptions, including extreme value theory, are given in forms applicable to assessing mission risks for both single events and the cumulative fluence of multiple events. The analyses yield simpler forms than previous models, include more recent data, and can easily be incorporated into existing computer programs.

Energy deposition and ionization fluctuations induced by ions in small sites--an analytical approach.

A concise, analytical approach is developed for calculating energy deposition and ionization fluctuations in volumes within ion-irradiated media which have dimensions as small as 1 nm. The method accounts for both direct ion interactions with the site and interactions of secondary electrons which are produced by ions in the surrounding medium. Particular attention is given to the way the contributions of the two types of events are combined. Since energy deposition fluctuations are simply related to the fundamental quantities ZD and yD employed in microdosimetry theory, this new approach provides a convenient means to obtain these parameters. Results obtained with the analytical method show good agreement with Monte Carlo charged-particle track-structure calculations of yD for 0.5 to 20 MeV protons incident on spherical sites of water vapor with diameters ranging from 1 nm to 10 microns. In contrast to Monte Carlo techniques, the analytical method does not depend on knowing the intricacies of single ion and electron interactions with the target and can therefore be adapted to calculations with heavier incident ions and different target materials, including those of the condensed state.

Resistance of holograms made in dichromated gelatin emulsion to fission neutron damage.

We have found that holograms made in a dichromated gelatin emulsion sandwiched between Suprasil-2 plates are resistant to damage caused by 4.8 x 10(13)-Cm(-2) [1-Mev(Si) equivalent] fission neutrons. These holograms are, therefore, suitable for use in certain radiation environments.

Resistance of holograms made in Polaroid DMP128 photopolymer to ionizing radiation damage.

Because of their light weight and general wave-front-transforming ability, holograms appear potentially useful as beam correctors and collimators for diode-laser arrays in intersatellite optical data links. However, to survive in space a hologram must withstand damage from electrons and protons trapped in the Van Allen belts. We have found that holograms made with Polaroid DMP128 photopolymer on Suprasil-2 can withstand 63-MeV protons up to a total dose of 2 Mrad (Si) and withstand (60)Co gamma rays up to a total dose of 2 Mrad (Si) without loss of diffraction efficiency. It appears that these holograms are sufficiently radiation hard for space application.