The energy loss per unit path length for a charged particle incident on a spatially uniform isothermal Maxwellian plasma is a function of the temperature and density of the medium. Within this model the temperature and compression &rgr;&Dgr;rof the tamper of a laser‐driven microshell target can be accurately determined, in the absence of electrostatic acceleration, by the simultaneous measurement of the energy loss from 3.52‐MeV &agr; particles from D‐T reactions and 3.02‐MeV protons from D‐D reactions.