Ranges and Energy-Loss Processes of Heavy Ions in Emulsion

Abstract

The range-energy relations for C, N, O, Ne, and A ions in nuclear-track emulsion have been measured for energies up to 10 Mev/nucleon. The ions, accelerated by the heavy-ion linear accelerator, were suitably degraded and subsequently analyzed by a 180\ifmmode^\circ\else\textdegree\fi{} double-focusing magnetic spectrometer. The heavy-ion ranges were measured relative to those of alpha particles which were employed to calibrate the instrument. Within the energy interval studied, it has been found that a general expression for the range of a heavy ion is $R=(\frac{M}{{z}^{2}})\ensuremath{\lambda}(\ensuremath{\beta})+M{z}^{\frac{2}{3}}{C}_{z}(\frac{\ensuremath{\beta}}{z})$, where $\ensuremath{\lambda}(\ensuremath{\beta})$ is the range of a particle of proton mass and charge at velocity $\ensuremath{\beta}c$, ${C}_{z}(\frac{\ensuremath{\beta}}{z})$ is an empirical function that corrects for the extension in range caused by neutralization of the ionic charge as electrons are captured at low velocities, and $M$ and $z$ are the ionic mass and charge in units of the proton. The range data are sufficiently complete and accurate to allow detailed analyses of rates of energy loss and effective charge of the heavy ions as they come to rest. The relative importance of primary and secondary ionization processes in producing the taper in the track of a multicharged ion has been studied by examining the ions in emulsions of various sensitivities. Buckling-type distortions of heavily ionizing tracks in strongly developed emulsions are also discussed. The range-energy relation for low-velocity protons is re-examined and an improved range point at 0.585 Mev is reported.