New Nonlinear Phenomena in Focused Acoustic Beam in Pressurized Superfluid 4He

摘要: We have studied the propagation properties of a focused acoustic beam in superfluid 4 He at 300 mK under several pressures and observed new nonlinear phenomena higher than 18 atm. Under these high (normal dispersion region), received power is increased proportion to input for low-power region, but it depleted rapidly after saturation input. It exhibits sharp dips further power. This phenomenon completely one, so there as yet no explanatory theory. propose possible mechanism explain which consists two processes.