Track Registration in Various Solid-State Nuclear Track Detectors

In a number of materials energetic, heavy nuclear particles leave trails of radiation-damaged material that can be selectively attacked by chemical reagents to produce tracks visible in the optical microscope. The trackregistration characteristics of three such materials--muscovite mica, Lexan polycarbonate, and cellulose nitrate--were investigated using fission fragments and various heavy ions from argon down to helium, each over a wide range of energies. Curves of energy-loss rate dE/dx versus particle energy were calculated for each solid, and the experimental results were displayed on the dE/ dx curves. It was found that for each detector there is a fairly narrow range of dE/dx values over which the trackregistration efficiency varies from unity to zero. This rapid drop in efficiency with dE/dx makes it reasonable to define a critical energy-loss rate (dE/dx)/sub crit/ for each detector, which appears to be independent of energy and atomic number. Crude estimates of particle masses can be made using several detectors with different (dE/dx)/sub crit/. For example, for particles with energies less than approximates 3 Mev/amu, the mass must exceed 3, 12, and 28 amu if tracks register in cellulose nitrate, Lexan polycarbonate, and muscovite, respectively. For particles such as fission fragments, with initial dE/dx >> (dE/dx)/sub crit/, the track lengths are a fair approximation of the particle ranges. Particles incident at a very small angle to a detector surface are registered in mica but not in plastics or glasses. Solid-state track detectors presently offer unique advantages when heavy particles must be studied in the presence of a high background flux of light particles. (auth)