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表现出的各种电和磁特性，例如超导(例如在悬浮列车中)和铁磁性(例如在计算机磁盘驱动器中)。为了开发性能更好的材料，需要对这些性质进行准确的测量，以便更准确地了解结构和功能是如何相关的。用于这一目的的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2K)。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/L)，而且在目前的储存配置下，无法回收。根据法律规定，2015年，世界上目前的大部分氦储备(约90%来自美国)将被出售。由于未回收的氦气不可逆转地从地球上逸出，因此它是一种不可再生的资源。为了应对氦的短缺，我们建议为PPMS配备一个制冷器，它可以压缩蒸发的氦，并将其重新冷凝到液体状态。通过这次翻新，氦的消耗从每月2,000 L氦液(2,500美元)大幅减少到每月一瓶氦气(100美元)；更重要的是，几乎所有使用的氦都被回收(&gt；95%)，从而为子孙后代保留了这一宝贵资源。

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.