Prompt phonon signals from particle interactions in Si crystals

The authors discuss the prompt (ballistic and quasidiffuse) phonon physics associated with elementary particle interactions within silicon crystals at temperatures below 1 K, and the difference in the ballistic and quasidiffuse phonon production from primary electron recoils versus primary nuclear recoils within these crystals. The results from a growing body of direct experimental evidence on prompt phonon signals from particle detectors bombarded with alphas, x-rays, and neutrons are summarized.