STOPPING POWERS OF 200-3200 KEV HE-4 AND 550-1550 KEV H-1 IONS IN POLYIMIDE

Accurate stopping powers of polyimide have been determined for mean en ergies ((E) over bar) in the range of 200 keV less than or equal to (E ) over bar less than or equal to 3200 keV for He-4 ions and 550 keV le ss than or equal to (K) over bar less than or equal to 1550 keV for H- 1 ions, using the transmission method for foils with areal densities o f 30-225 mu g/cm(2). The overall uncertainties of similar to 2% are ma inly due to the foil thickness determination. The present data have be en parametrized and compared to results obtained by previous authors i n the upper energy range and to various parametrizations found in the literature. The best description of the data is given by Bragg's rule calculations using parametrized elemental stopping powers that were de rived from large data sets (deviations <2%). No support is found for t he cores-and-bonds model showing deviations of 3%-5%, that may be due to the neglect of phase state effects. (C) 1996 American Institute of Physics.