Most existing track formation models for track-etch detectors relate the local etch-rate v t to the particle’s linear energy transfer (LET) along its trajectory. While this approach reproduces experimental data well, it has fundamental limitations: LET is an average measure of energy loss and does not capture the local energy deposition around the particle trajectory, i.e., the radial dose distribution. As a result, for conventional track formation models, the track etch-rate v t is derived from experiments for each particle type and energy, which is both very demanding and limits predictive capabilities. To generalise track formation modelling and overcome previous limitations, this work models the local etch-rate as a function of the local absorbed dose d , i.e. v d , rather than as a function of LET or residual range along the track, v t . The track contours are calculated in a three iterations: (i) The local dose d around the ion trajectory is modelled through a combination of amorphous track structure theory, which accounts for the radial dose deposition by secondary electrons, and stopping power tables. (ii) Next, a single generalised etch-rate function v d is identified to model how local polymer damage translates into etching speed for different ion species and energies. Along with the bulk etch-rate v bulk for unirradiated material, this enables the calculation local etch-rates v in the entire detector. (iii) Finally, the track contour is calculated by interpreting the etching front as a wave front propagating through a medium with spatially varying speed, where the local speed is given by the etch-rate v at each point. Iso-contours of equal arrival time correspond to the track contour after a given etching time. Validation against experimental data for various ion species and energies shows agreement within the uncertainties between predicted and observed track geometries. Unlike LET-based models, this local dose-based model provides predictive capabilities for ions and energies outside the calibration domain. The framework, tracketch , is available as an open-source package. • A unified CR-39 track formation model based on local absorbed dose, not LET. • Amorphous track structure theory provides the radial dose around ion tracks. • A wavefront method calculates track contours as iso-arrival-time surfaces. • One calibrated v ( d ) function predicts tracks across ion species and energies. • Model validated against multi-ion CR-39 shape data; open-source as tracketch.
Jeppe Brage Christensen (Fri,) studied this question.