Abstract

Low temperature measurement of the thermal conductivity of insulating materials is generally made using a boil-off calorimetry technique involving liquid hydrogen (LH2). Liquid neon (LNe) has nearly the same normal boiling point as LH2, but has a much larger heat of vaporization, allowing extended run times. In the past, the main drawback of using LNe has been its excessive cost; $170.00 per liter versus $1.50 per liter for LH2 (1989 prices). A neon liquefaction plant has been designed and constructed to capture, purify and refrigerate the neon boil-off from calorimetry experiments. Recycling the neon reduces operating costs to approximately $20 per liter. The system consists of a purification section, which removes air and other contaminants from the calorimetry boil-off, a heat exchanger, LNe and LH2 storage dewars and a fully automated control system. After purification, neon is liquified in the heat exchanger by LH flowing countercurrently through stainless steel cooling coils. Hydrogen flow is automatically adjusted to keep the neon at its normal saturation temperature, 27 K. The liquid neon is then stored in a dewar placed directly below the heat exchanger. A 5 watt Gifford-McMahon refrigerator provides cooling during extended storage or low-flow applications.

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