Improved acoustic instrumentation of the SIMPLE detector

The application of Superheated Droplet Detectors in dark matter searches by the SIMPLE project uses an acoustic instrumentation sensitive to the shock wave generated by the bubble nucleation of the refrigerant droplets. Previous instrumentation has been unable to distinguish between true nucleation and background noise events in the device, in particular microleaks associated with the escape of overpressuring nitrogen gas into the surrounding water bath. We here describe the development of an improved instrumentation which is shown to provide this discrimination capacity through a reduced noise level of the transducer amplification circuitry.