Observation of stable, high Mach number collisionless electrostatic shocks

Observation of large amplitude ion acoustic shocks with a high Mach number up to two in a collisionless laboratory plasma characterized by Te/Ti approximately 10 is described. Although they have large fluctuations behind the front, these shocks are almost laminar rather than turbulent, and they behave nonstationarily during propagation. A discussion about the upper critical Mach number for the excitation of laminar shocks and the behavior of the shocks is also presented.