A new type of low‐temperature heat switch is described. The switch uses unforced convection of helium gas within a closed loop. We report measurements of the performance of a simple version of the heat switch.

1.
A. C. Rose‐Innes, Low Temperature Techniques (Van Nostrand, New York 1964), Chap. 3.
2.
G. K. White, Experimental Techniques in Low‐Temperature Physics (Oxford, London, 1959), Chap. 6.
3.
J.
Anesin
and
J. L. G.
Lamarche
,
Rev. Sci. Instrum.
38
,
368
(
1967
).
4.
J. H.
Colwell
,
Rev. Sci. Instrum.
40
,
1182
(
1969
).
5.
For a recent version of this scheme see
E.
Tward
,
Gas Heat Switches, NBS Special Publication
607
,
178
(
1981
).
6.
See, for example, O. V. Lounasmaa, Experimental Principles and Methods Below IK (Academic, New York, 1974), Chap. 2.
7.
As is shown in Fig. 1(a), the loop also included short sections of copper tube at the top and bottom. These copper tubes will make some extra contribution to the efficiency of the heat exchangers. However, this heat exchange is limited because of the fairly thin wall of the tube (0.08 cm) and because the copper was just oridinary copper (i.e., not high conductivity).
8.
J. P.
Franck
,
F. D.
Manchester
, and
D. L.
Martin
,
Proc. R. Soc. (London)
263A
,
494
(
1961
);
V. J. Johnson, A Compendium of the Properties of Materials at Low Temperature (U.S. Dept. of Commerce, Washington, DC, 1960), Part II.
9.
See Ref. 2, pp. 184–186.
10.
We are considering here the helium to be a gas even though 4.2‐K helium at 2 and 4 bars must strictly be a liquid. We do this because, as discussed below, the efficiency of the cold heat exchanger is not large enough to cool the helium to close to 4.2 K. Thus, it will remain a gas at all points on the loop.
11.
See Ref. 2, pp. 75 and 76.
12.
We have not included any contribution from the copper tubes (see Ref. 7).
13.
M. Jakob, Heat Transfer (Wiley, New York, 1948), Vol. I.
14.
W. McAdams, Heat Transmission (McGraw‐Hill, New York, 1954).
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