a CdS crystal annealed in an inert atmosphere at {HEAD ~ a temperature} and for a period of time to provide {TAIL ~ substantially maximum acoustic attenuation} at the operating frequency of the crystal; and 
a CdS crystal annealed in an inert atmosphere at { HEAD ~ a temperature } and for a period of time to provide { TAIL ~ substantially maximum acoustic attenuation } at the operating frequency of the crystal ; and
OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH