Survey and compilation of stopping power data conducted by the International Commission on Radiation Units and Measurements
One of the principal objectives of the International Commision on Radiation Units and Measurements (ICRU) is to recommend internationally acceptable values of physical quantities relevant to radiation measurements and radiological dosimetry. Among a large variety of the physical quantities treated by the ICRU, the stopping power is one of the most fundamental. In 1984, the ICRU issued its Report (No. 37) concerning stopping power for electrons and positrons. Currently the ICRU is preparing a report on data for protons and alpha particles. Work planned for the future concerns heavier charged particles, which include most importantly carbon, oxygen, and nitrogen ions resulting from neutron irradiation of human tissues. The task requires, in addition to mere collection of published data, critical evaluation of those data for their reliability, precision, and accuracy. The critical evaluation in turn requires full knowledge of experimental and theoretical methods for the determination of stopping power. The present article points out key issues and major unsolved problems involved in the determination.