Cost-effective continuous operation of the CLS-QMSC Beamline at cryogenic temperatures

这项提议是为量子材料光谱分析中心(QMSC)的光束线购买一台闭路循环低温冷却器，该低温流冷器由Andrea Damascelli博士领导，位于萨斯卡通的加拿大光源(CLS)。新的低温冷却器将用于转换最先进的液氦流动低温恒温器，该恒温器用于自旋和角度分辨光电子能谱(SPIN+ARPES)实验，在这种实验中，消耗的氦不会被回收到基本上是闭合循环的，同时在最低温度下保持高冷却功率。 今天，低温实验使用两种冷却方法：在流动低温恒温器中直接使用液氦或设计用于低温的闭路循环制冷系统。每一种都有独特的优点和缺点。流动低温恒温器的一个关键问题是巨大的运行成本，这对CLS-QMSC来说尤其令人望而却步，因为它的典型用户程序每天24小时运行10个月/年。因此，使用传统的流动低温恒温器进行Spin+ARPES项目的成本为每年10万美元，并消耗地球上最宝贵的不可再生资源之一，将其释放到大气中。此外，氦气杜瓦必须每隔3-4天更换一次，要求系统预热后才能再次冷却。这严重影响了光束线正常运行时间，对于世界各地的学术和工业用户来说，这是一种宝贵的商品，每个用户分配的光束时间都是有限的。总体而言，这是极其昂贵和低效的。另一方面，典型的闭合循环低温恒温器可以几乎无限期地保持其最低工作温度，从而最大限度地延长正常运行时间，而不会损失氦。它在样品位置的冷却功率也将比流动低温恒温器低得多，后者需要相当多的设计考虑才能达到合理的低温。 我们的目标是将QMSC光束线上的自旋+ARPES流低温恒温器有效地转换为使用ColdEdge Technologies的4K Stinger的闭合循环系统，该系统在4K下的冷却功率为0.9W。它将允许我们达到并在无限的时间内保持6K的样品温度，大大提高QMSC光束线的效率和正常运行时间，并消除令人望而却步的运营成本。值得注意的是，这种冷却器与我们现有的流动低温恒温器无缝对接，不需要重新设计或修改硬件，并且与传统的闭路循环系统不同，只要改用液氦杜瓦并在排气侧抽气，就能够在必要时达到3.0K。对于量子材料和器件的研究来说，这些看起来很小的基温差异是最显著的。因此，该系统为CLS-QMSC国内和国际用户社区提供了最佳解决方案，保证了几乎无休止的运行时间和非常低的基准温度，同时显著降低了CLS的QMSC光束线的运营成本。

This proposal is for the purchase of a closed-cycle cryogenic cooler for a low-temperature flow cryostat for the Quantum Materials Spectroscopy Centre (QMSC) beamline led by Dr. Andrea Damascelli and located at the Canadian Light Source (CLS) in Saskatoon. The new cryogenic cooler will be used to convert a state-of-the-art liquid helium flow cryostat reserved for spin- and angle-resolved photoemission spectroscopy (Spin+ARPES) experiments for which consumed helium is not recovered to one that is essentially closed-cycled while maintaining high cooling power at the lowest temperatures. Today, low temperature experiments utilize two cooling approaches: the direct use of liquid helium in a flow cryostat or a closed-cycle refrigeration system designed for cryogenic temperatures. Each has unique benefits and drawbacks. A key problem with flow cryostats is the significant operating cost, particularly prohibitive for the CLS-QMSC whose typical users' program runs 24/7 for 10 month/year. Thus, using a conventional flow cryostat for the Spin+ARPES effort costs $100,000/year and consumes one of the earth's most precious non-renewable resources, releasing it into the atmosphere. Also, the helium dewar must be changed every 3-4 days requiring the system to be warmed up before it can be cooled again. This severely impacts the beamline uptime, a precious commodity to the academic and industrial users from around the world, each with limited allotted beamtime. Overall, this is extremely costly and inefficient. On the flip side, a typical closed cycle cryostat can be maintained at its lowest operational temperature almost indefinitely maximizing uptime operation, without the loss of helium. It will also have much lower cooling power at the sample location than a flow cryostat, which requires considerable design considerations to get to reasonably low temperatures. Our aim is to effectively convert the Spin+ARPES flow cryostat on the QMSC beamline into a closed cycle system with the 4K Stinger from ColdEdge Technologies, which has a demonstrated 0.9W of cooling power at 4K. It will allow us to reach and maintain a sample temperature of 6K for an unlimited time period, substantially increasing the QMSC beamline efficiency and uptime, and removing the prohibitive operational costs. Notably, this cooler seamlessly interfaces with our existing flow cryostat no redesign or hardware modifications needed and, unlike a conventional close-cycle system, is capable of reaching 3.0 K whenever necessary, by simply switching over to a liquid helium dewar and pumping on the exhaust side. For quantum materials and devices research, these seemingly “small” differences in base temperature are most significant. Thus, this system offers the best solution for CLS-QMSC national and international users' community, guaranteeing virtually endless operating times and very low base temperatures, while considerably decreasing the operational costs of the QMSC beamline at CLS.