  A novel method for characterising the full spectrum of deuteron ions emitted
by laser driven multi-species ion sources is discussed. The procedure is based
on using differential filtering over the detector of a Thompson parabola ion
spectrometer, which enables discrimination of deuterium ions from heavier ion
species with the same charge-to-mass ratio (such as C6+, O8+, etc.). Commonly
used Fuji Image plates were used as detectors in the spectrometer, whose
absolute response to deuterium ions over a wide range of energies was
calibrated by using slotted CR-39 nuclear track detectors. A typical deuterium
ion spectrum diagnosed in a recent experimental campaign is presented.
