  In recent data on neutron induced acoustic cavitation in
deuterium--containing liquids obtained by neutron measurements it was shown
that very high temperatures could arise in some special cases. To study
temperature of so--called bubble plasma it is desirable to have
micro--detectors of X-rays, which can be prepared on the basis of
room--temperature semiconductor detectors, in particular on mercuric iodide
($\alpha$--HgI$_2$) crystals. Having in view this aim, the properties of
gel--grown ($\alpha$--HgI$_2$) crystals was studied by means of isothermal
currents, and trap parameters was estimated. Results are promising for special
aim of preparing X-ray detectors with moderate energy resolution needed in
bubble--plasma diagnostic, though improving of crystal growing technology is
necessary.
  {\it PACS:} 29.40.Wk; 52.70.La {\it Keywords:} X-ray and gamma--ray
measurements; semiconductor detectors; mercuric iodide; plasma diagnostics;
cavitation
