  The superheated droplet detector (SDD) is known to be gamma insensitive below
a threshold temperature which made them excellent candidates for neutron
detection in the presence of gamma rays. Above the threshold temperature, the
gamma ray detection efficiency increases with increase in temperature. In this
work the gamma ray threshold temperature has been studied for SDD using R404A
as the active liquid and is compared to the theoretical prediction. The
temperature variation of gamma ray detection efficiency and interstate
transition kinetics has also been studied using a two-state model. The
experiments are performed at the ambient pressure of 1 atmosphere and in the
temperature range of 17-32oC using a 662 keV 137Cs gamma ray source.
