Track Registration in Various Solid-State Nuclear Track Detectors

TLDR

Solid‑state track detectors enable visualization of radiation‑damaged trails from energetic heavy particles, providing a unique advantage for studying such particles amid high background fluxes of light particles. The authors aimed to use detectors with different critical energy‑loss rates to obtain crude estimates of particle masses. They examined track‑registration in muscovite mica, Lexan polycarbonate, and cellulose nitrate by measuring dE/dx curves for fission fragments and heavy ions from argon to helium across a broad energy range. They found that each detector has a narrow dE/dx window where track‑registration efficiency drops from unity to zero, allowing definition of a critical dE/dx independent of energy and atomic number; this enables mass estimation (e.g., >3, 12, 28 amu for cellulose nitrate, Lexan, muscovite at <3 MeV/amu), accurate range estimation for fission fragments, and angle‑dependent registration favoring mica over plastics or glasses.

Abstract

In a number of materials energetic, heavy nuclear particles leave trails of radiation-damaged material which can be selectively attacked by chemical reagents to produce tracks visible in the optical microscope. The track-registration 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 $\frac{\mathrm{dE}}{\mathrm{dx}}$ versus particle energy were calculated for each solid, and the experimental results were displayed on the $\frac{\mathrm{dE}}{\mathrm{dx}}$ curves. It was found that for each detector there is a fairly narrow range of $\frac{\mathrm{dE}}{\mathrm{dx}}$ values over which the track-registration efficiency varies from unity to zero. This rapid drop in efficiency with $\frac{\mathrm{dE}}{\mathrm{dx}}$ makes it reasonable to define a critical energy-loss rate ${(\frac{\mathrm{dE}}{\mathrm{dx}})}_{\mathrm{crit}}$ 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 ${(\frac{\mathrm{dE}}{\mathrm{dx}})}_{\mathrm{crit}}$. For example, for particles with energies less than \ensuremath{\sim}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 $\frac{\mathrm{dE}}{\mathrm{dx}}\ensuremath{\gg}{(\frac{\mathrm{dE}}{\mathrm{dx}})}_{\mathrm{crit}}$, 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.