McClintock, Peter V. E. (1978) An apparatus for preparing isotopically pure 4He. Cryogenics, 18 (4). pp. 201-208. ISSN 0011-2275
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Abstract
A cryostat has been constructed for extracting pure He4 from He II of natural isotopic composition by means of a heat flush technique. It is shown that the method is in principle capable of yielding He4 which is entirely devoid of He3 isotopic impurities. A secondary heat flush, operated in conjunction with a conical heat exchanger of novel design, was used to place an experimental lower bound of 2 × 1015 on the ratio of the product, a standard sufficient for all present or projected applications requiring isotopically pure He4. The apparatus produces 2 000 1 (at standard temperature and pressure) of He4 per thermal cycle. The design of future purifiers is discussed.