Döge Stefan, Hingerl Jürgen
Institut Laue-Langevin, 71 Avenue des Martyrs, F-38042 Grenoble Cedex 9, France.
Rev Sci Instrum. 2018 Mar;89(3):033903. doi: 10.1063/1.4996296.
The improvement of the number of extractable ultracold neutrons (UCNs) from converters based on solid deuterium (sD) crystals requires a good understanding of the UCN transport and how the crystal's morphology influences its transparency to the UCNs. Measurements of the UCN transmission through cryogenic liquids and solids of interest, such as hydrogen (H) and deuterium (D), require sample containers with thin, highly polished and optically transparent windows and a well defined sample thickness. One of the most difficult sealing problems is that of light gases like hydrogen and helium at low temperatures against high vacuum. Here we report on the design of a sample container with two 1 mm thin amorphous silica windows cold-welded to aluminum clamps using indium wire gaskets, in order to form a simple, reusable, and hydrogen-tight cryogenic seal. The container meets the above-mentioned requirements and withstands up to 2 bar hydrogen gas pressure against isolation vacuum in the range of 10 to 10 mbar at temperatures down to 4.5 K. Additionally, photographs of the crystallization process are shown and discussed.
要提高基于固态氘（sD）晶体的转换器中可提取超冷中子（UCN）的数量，需要深入了解UCN的输运过程以及晶体形态如何影响其对UCN的透明度。测量UCN透过诸如氢（H）和氘（D）等感兴趣的低温液体和固体的情况，需要具有薄的、高度抛光且光学透明窗口以及明确样品厚度的样品容器。最困难的密封问题之一是低温下氢气和氦气等轻气体对高真空的密封。在此，我们报告一种样品容器的设计，该容器有两个1毫米厚的非晶态二氧化硅窗口，使用铟丝垫圈冷焊到铝夹上，以形成一个简单、可重复使用且气密的低温密封。该容器满足上述要求，在温度低至4.5 K时，能承受高达2巴的氢气压力，对抗10至10毫巴范围内的隔离真空。此外，还展示并讨论了结晶过程的照片。
