Preparing for the coming sortage of helium: A critical magnetometer upgrade

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Inorganic solid-state materials derive their usefulness from the diverse electrical and magnetic properties that they display, such as superconductivity (e.g. in levitating trains) and ferromagnetism (e.g. in computer disk drives). Accurate measurements of these properties is required to develop better performing materials by understanding more precisely how structure and function are related. A critical piece of equipment for this purpose is a Quantum Design Physical Property Measurement System (PPMS), which generates high magnetic fields (up to 9 Tesla) and is capable of reaching very low temperatures (down to 2 K). Liquid helium is consumed as a cryogen to maintain the superconducting state required for the high-field magnet and to achieve the low temperatures. Unfortunately, liquid helium is very expensive ($13/L) and, under the current configuration in which it is stored, not recoverable. In 2015, most of the world's current reserve of helium (about 90% from the US) will be sold off, as required by law. Because unrecycled helium gas escapes irretrievably from the earth, it is a non-renewable resource. To prepare for the impeding shortage of helium, we propose to equip the PPMS with a cryocooler, which compresses helium that has vaporized and recondenses it back into the liquid state. With this refurbishment, the consumption of helium is dramatically reduced from 2000 L of helium liquid per month ($2500) to one cylinder of helium gas per month (<$100); more importantly, nearly all of the helium used is recycled (>95%), thereby preserving this precious resource for future generations.