a Pulsed Laser Experiment Simulating Acoustic Signals from High Energy Charged Particles in Water

The effects and thermoacoustic mechanism involved in the use of distilled water as an acoustic medium for the detection of high-energy charged particles have been examined using a Q-switched YAG laser with a 1.06 micron wavelength and a typical pulse energy of about 0.3 J. The behavior of water above or below 4 C is in agreement with the predictions of thermoacoustic theory. At 4 C, however, a tripolar pulse appears which must be a nonthermoacoustic signal. The latter begins with a rarefaction produced by electrostriction rather than compression. The characteristics of this signal are discussed in some detail. It is found that if the energy of deposition exceeds a certain level the thermoacoustic theory no longer holds, and it is concluded that Q-switched YAG lasers can perfectly simulate the acoustic generating mechanism of high-energy charged particles.