  In this paper we present a method for single track coincidence measurements
using two different track detector materials. We employed plastic and
fluorescent nuclear track detectors (PNTDs and FNTDs) in the entrance channel
of a monoenergetic carbon ion beam covering the therapeutically useful energy
range from 80 to 425 MeV/u. About 99 % of all primary particle tracks detected
by both detectors were successfully matched, while 1 % of the particles were
only detected by the FNTDs because of their superior spatial resolution. We
conclude that both PNTDs and FNTDs are suitable for clinical carbon beam
dosimetry with a detection efficiency of at least 98.82 % and 99.83 %
respectively, if irradiations are performed with low fluence in the entrance
channel of the ion beam. The investigated method can be adapted to other
nuclear track detectors and offers the possibility to characterize new track
detector materials against well-known detectors. Further, by combining two
detectors with a restricted working range in the presented way a
hybrid-detector system can be created with an extended and optimized working
range.
