Experimental judgement of the origin of threshold of bubble detectors

Experimental studies have been carried out with 500MeV/u \ 56 Fe, 650MeV/u \ 40 Ar, 600MeV/u \ 28 Si and 180MeV/u \ 4He for T-12 type bubble detectors. The studies show that threshold property of bubble detectors can be expressed by critical rate of energy loss. Contrarily, restricted energy loss rate can not be the criterion of track formation in bubble detectors under ordinary condition for the reason that different heavy ions create tracks at different critical values of the restricted energy loss rate.