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

该提案旨在为Andrea Damascelli博士领导的量子材料光谱中心（QMSC）光束线的低温流动低温恒温器购买一台闭路低温冷却器，该光束线位于萨斯卡通的加拿大光源（CLS）。新的低温冷却器将用于将最先进的液氦流低温恒温器转换为自旋和角度分辨光电子能谱（Spin+ARPES）实验，其中消耗的氦不能回收到基本上是封闭循环的，同时在最低温度下保持高冷却功率。 今天，低温实验采用两种冷却方法：直接使用液氦在流动低温恒温器或封闭循环制冷系统设计的低温温度。每一种都有独特的优点和缺点。流动式低温恒温器的一个关键问题是显著的运行成本，特别是对于CLS-QMSC来说，其典型的用户程序运行10个月/年的24/7。因此，在Spin+ARPES项目中使用传统的流动低温恒温器每年花费10万美元，消耗地球上最宝贵的不可再生资源之一，并将其释放到大气中。此外，氦气杜瓦瓶必须每3-4天更换一次，需要在再次冷却之前预热系统。这严重影响了光束线传输器，这对来自世界各地的学术和工业用户来说是一种宝贵的商品，每个用户都有有限的分配光束时间。总的来说，这是非常昂贵和低效的。另一方面，典型的闭合循环低温恒温器可以保持在其最低操作温度，几乎无限期地最大化制冷操作，而不会损失氦。它在样品位置的冷却能力也比流动低温恒温器低得多，这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束线上的Spin+ARPES流动低温恒温器有效地转换为具有ColdEdge Technologies的4K Stinger的封闭循环系统，该系统在4K下具有0.9W的冷却功率。这将使我们能够在无限的时间内达到并保持6 K的样品温度，大大提高QMSC光束线的效率和稳定性，并消除高昂的运营成本。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接口，无需重新设计或硬件修改，并且与传统的闭合循环系统不同，只要需要，只需切换到液氦杜瓦瓶并在排气侧进行泵送，就能够达到3.0 K。对于量子材料和器件研究来说，这些看似“微小”的基础温度差异最为显著。因此，该系统为CLS-QMSC国家和国际用户群体提供了最佳解决方案，保证了几乎无限的操作时间和非常低的基础温度，同时大大降低了CLS 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.