This research, sponsored by NASA, is related to dosimetry of cosmic radiation during manned s pace missions. We are measuring the response of tissue equivalent proportional counters (TEPC) to beams of particles such as Fe-56, Ne-20, C-12 and He-4 that are produced at Brookhaven National Laboratory and the National Institute of Radiological Science s (NIRS) in Japan. This work is in collaboration with physicists from the Lawrence Berkeley National Laboratory and NIRS.

Here is a picture of the experimental setup at Brookhaven National Laboratory's Alternating Gradient Synchrotron.

Results showing measurements of energy deposition, lineal energy (keV/um), as a function of the path length through a simulated volume of tissue 1 um in diameter. The p hysical diameter of the TEPC is 12.7 mm. In this case the pathlength is represented by the impact parameter which is the distance of the particle trajectory from the center of the detector. An impact parameter of 6.35 mm just grazes the side wall of the s pherical detector. The green circles represent total energy deposition equivalent to pathlength* LET. This indicates that energy deposition is less than expected for trajectories through the center of the detector and larger than expected for trajectories near the sides of the detector.