Charge state and stopping dynamics of fast heavy ions in dense matter

Abstract

$K$-shell radiation of fast heavy ions penetrating solid matter was used to analyze the stopping dynamics of ions over more than 80% of the stopping path. The most important advantage of this method is that the data is obtained with a high spatial resolution directly from the interaction volume. In experiments $11.4\phantom{\rule{0.3em}{0ex}}\mathrm{MeV}∕\mathrm{u}$ Ca projectile were slowed down in solid quartz and low-density $\mathrm{Si}{\mathrm{O}}_{2}$ aerogel targets. Characteristic projectile and target spectra in the photon energy range of 1.5--4 keV were registered by means of spherically bent crystal spectrometers with high spectral and spatial resolution in the direction of the ion beam propagation. $K$-shell spectra of heavy ions induced by close collisions with target atoms provided information about the projectile charge state and velocity dynamics. The line intensity distribution of the $K$-shell transitions arising from ions with different ion charges represents the charge state distribution along the ion beam track. The variation of the line Doppler shift due to the ion deceleration in the target material was used to determine the ion velocity dynamics. The spectroscopic analysis of the stopping process was complemented by measurements of the energy loss and ion charge state distribution after the ion beam emerged from the target using a standard time-of-flight method and magnet spectrometer.