Snodgrass Ryan, Ullom Joel
National Institute of Standards and Technology, Boulder, CO 80305, USA, Department of Physics, University of Colorado Boulder, Boulder, CO 80309, USA.
Cryogenics (Guildf). 2022 Jun;124. doi: 10.1016/j.cryogenics.2022.103473.
The second-stage regenerators of pulse tube refrigerators (PTRs) are routinely used to intercept heat loads without disturbing cooling at their base temperatures, often near 4 K. Gifford-McMahon cryocoolers (GMCs) have not yet demonstrated a similar capability to provide regenerator cooling, possibly because of the thermal resistance between their regenerator shell and core. Here we show that GMCs do have capacity to provide regenerator cooling when heat loads are applied directly on the outer regenerator shell, although to a lesser extent compared to PTRs of similar cooling capacity. For example, we intercepted a 900 mW heat load at 21.6 K using the second-stage regenerator of a GMC while only giving up 10 mW of cooling at 3 K (out of 270 mW). This performance may possibly be improved by optimizing heat exchange between heat source and regenerator shell. We provide detailed temperature profile measurements from both a GMC and a PTR while applying heat to the regenerators, showing distinct behavior between the two. We also show that for GMCs, the optimal location of heat injection should be farther from the cold end than for PTRs. Although the physical source of regenerator cooling is less clear for GMCs than it is for PTRs, a useful amount of cooling is available and warrants further study.
脉管制冷机（PTR）的二级回热器通常用于在不干扰其基础温度（通常接近4K）下的制冷效果的情况下拦截热负荷。吉福德-麦克马洪低温制冷机（GMC）尚未展现出类似的提供回热器冷却的能力，这可能是由于其回热器外壳与芯体之间的热阻所致。在此我们表明，当热负荷直接施加在回热器外壳上时，GMC确实有能力提供回热器冷却，尽管与具有类似制冷能力的PTR相比程度较小。例如，我们使用一台GMC的二级回热器在21.6K拦截了900mW的热负荷，而在3K时仅损失了10mW的制冷量（总共270mW）。通过优化热源与回热器外壳之间的热交换，这种性能可能会得到改善。我们给出了在对回热器加热时GMC和PTR的详细温度分布测量结果，显示出两者之间的不同行为。我们还表明，对于GMC而言，热注入的最佳位置应比PTR离冷端更远。尽管GMC中回热器冷却的物理来源不如PTR那样清晰，但仍有可观的制冷量，值得进一步研究。
