Laboratory helium liquifier for supersolid research

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This is a proposal to acquire a small-scale helium liquifier for a low temperature physics laboratory.  The research that will be enabled by this liquifier involves experimental studies of solid helium at high pressures and ultralow temperatures, a regime where a new "supersolid" phase of matter was recently discovered.  Because of the extremely low temperatures needed (within 0.2 degrees of absolute zero), all such experiments require the use of a powerful "dilution refrigerator", which uses substantial amounts of liquid helium to operate.  Helium is an expensive and non-renewable resource but recent developments in cryogenic technology (pulse tube refrigerators) have dramatically reduced the cost of recovering and reliquifying helium on a small scale.  The helium liquifier in this proposal will allow us to recycle the gas produced as the liquid helium boils off and produce up to 20 liters of liquid helium per day.  This will allow us to continuously operate our dilution refrigerator and perform more experiments, more effectively.  It will also conserve approximately 2 million liters of helium gas each year.  This will save approximately $30,000 per year in liquid helium costs, repaying the investment within 3 years.  The cost savings will be used to support graduate students being trained in low temperature and experimental condensed matter physics.