Physics & Astronomy Faculty and Staff Publications

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It is well known that extraordinary levels of vibration isolation from the noise of mechanical cryocoolers can be obtained in small cryostats using 1-atm helium exchange gas combined with a soft bellows. This technique has been used successfully by others in a number of small, special-purpose research and commercial cryostats, enabling, for example, Mossbauer spectroscopy below 5K with a GiffordMcMahon cooler. Our group has an ongoing project to implement this technique in a general-purpose research cryostat, with the long-term goal of achieving vibration performance comparable to the best vibration-isolated helium bath cryostats while maintaining adequate 4K working volume, cooling power, and base temperature. In this report we describe the design, thermal performance, and some operational details of a cryostat incorporating a compact exchange-gas envelope and heat exchangers constructed around a Cryomech PT405 0.5W/4.2K pulse-tube cryocooler. This cryostat is in regular use in our lab and performs well, cooling a large shielded 4K working volume (~35 L) containing a heavy iron-shielded superconducting magnet (total metal at 4K ~20 kg) from room temperature to 4K in about 24 hours, achieving base temperatures(condensing the helium), and maintaining temperature ≤4.8K for an externally-applied heat load of 0.5W.

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Cryogenic Engineering Conference & International Cryogenic Materials Conference



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