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

无机固态材料的用途来自于它们所显示的各种电和磁特性，例如超导性（例如悬浮列车）和铁磁性（例如计算机磁盘驱动器）。 需要精确测量这些特性，以通过更精确地理解结构和功能之间的关系来开发性能更好的材料。 为此目的的一个关键设备是量子设计物理特性测量系统（PPMS），它可以产生高磁场（高达9特斯拉），并能够达到非常低的温度（低至2 K）。 液氦被用作制冷剂，以保持高场磁体所需的超导状态，并实现低温。 不幸的是，液氦非常昂贵（13美元/升），并且在目前的储存配置下，不可回收。 到2015年，根据法律规定，世界上现有的氦储备（约90%来自美国）将被出售。 因为不可回收的氦气会从地球上逃逸出来，是一种不可再生的资源。 为了应对氦气短缺的阻碍，我们建议为PPMS配备一个低温冷却器，它可以压缩已经蒸发的氦气，并将其重新冷凝回液态。 通过这种翻新，氦气的消耗量从每月2000 L氦液体（2500美元）大幅减少到每月一缸氦气（<100美元）;更重要的是，几乎所有使用的氦气都被回收（>95%），从而为后代保留了这一宝贵的资源。

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.