The Scintillating Bubble Chamber (SBC) collaboration will be using acoustic transducers, designed and fabricated at IUSB, in their search for low mass (0.7 – 7 GeV/c^2) WIMP dark matter with a liquid argon bubble chamber. The transducers, which are the primary instrument for distinguishing radioactivity-induced background events from dark matter-induced events, will need to operate at a temperature of 87 K (liquid argon temperature), while maintaining sensitivity to acoustic waves in the 1kHz to 200 kHz regime. IUSB has tested three transducer build modifications for SBC which seek to increase the physical robustness of the devices. At the same time, there is evidence from the liquid-fueled rocket industry that the piezoelectric ceramic (the active elements in the acoustic transducers) made from Lead Zirconate Titanate (“PZT”) currently used might lose sensitivity at these low temperatures, whereas single-crystal piezoelements are less susceptible to such effects.
This project has three main goals. First, we compared the mechanical robustness of three transducer designs under simulated experimental conditions. Second, we are currently testing the degree to which acoustic sensitivity is lost in PZT in going from room temperature to 77K (liquid nitrogen temperature). Third, in the future, we will test a novel piezoceramic being developed for this project which has characteristics between those of a single-crystal piezoelectric element and a random phase element which should have similar sensitivity to single crystals at low temperature, but which are easier and less expensive to produce and can be grown with low radioactivity contamination.
