An experimental investigation on two-component multi-phase helium and nitro
gen mixtures in a single-stage pulse tube refrigerator was carried out. The
experimental results show that both coefficient of performance (COP) and c
ooling power can be improved to some extent at above 70 K when the nitrogen
fraction in the mixture is less than 25%. An approximate stable temperatur
e platform at the triple point 63.15 K of nitrogen, which is independent of
nitrogen's fraction, is obtained when the cooling power is below 7 W. (C)
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