Detection of energetic heavy ions

Abstract

The delta-ray theory of track structure, applied earlier to such 1-or-more hit detection systems as the inactivation of dry enzymes and viruses, the NaI(Tl) scintillation counter, and nuclear emulsion, is extended to the silver activated phosphate glass dosimeter, the LiF thermoluminiscent dosimeter, the creation of free radicals in solid biological substances, solid and liquid organic scintillators, and the ferrous sulfate (Fricke) dosimeter. The response of these systems to both gamma-rays and heavy ions is characterized by two parameters: 1) D γ 37, the dose of gamma-rays at which 37% of the sensitive elements remain unaffected by the radiation, and 2) a 0, the physical radius (or the exciton diffusion length, or the range of short-range order) of the sensitive element. The decline of detector response with increase in the stopping power of the bombarding ion, and the non-linearity of the detector response are characteristic properties of 1-hit detectors, and are most pronounced for the most sensitive detectors. Explicit information about the cross-sectional area of the sensitive target cannot be gained from measurement of the activation cross-section as a function of the stopping power of the incident ion, for there is no saturation cross-section for 1-hit detectors. Since parameters describing the incident ion and those describing the detector are not separable variables, the response of a detector cannot be described through a product of two factors, one containing only ion parameters and representing “radiation quality”, and the other containing only detector parameters and representing “detector quality”.