The Geyser effect in the expansion of solid helium into vacuum

The mechanism behind the intensity oscillations accompanying the flow of solid helium through a micron-sized orifice into vacuum, called the geyser effect, is investigated by measuring the pressure pulses at various locations in the entire flow system. The new results reveal that the source chamber pressure pulses have the same shape as the external detector pulses monitored in the previous experiments [G. Benedek et al., Phys. Rev. Lett. 95, 095301 (2005)]. New experiments in which the external gas reservoir is isolated from the pressure regulator provide direct information on the mechanism of the collapse leading to the geyser pulses. Thus each geyser pulse is triggered by the breakdown of a plug located upstream of the source chamber. The flow of liquid through the orifice determines the shape of the subsequent geyser pulse.