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Submitted on 1 Jan 1978
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FAST LOADING DILUTION REFRIGERATOR
G. Binnig, H. Hoenig
To cite this version:
JOURNAL DE PHYSIQUE Colloque
C6,
supplkment auno
8, Tome 39, aolit 1978, page ~ 6 - 1 1 4 8FAST LOADING D1
LUTI
ON REFRIGERATOR
XG. Binnig and H.E. Hoenig
PhysikaZisches I n s t i t u t der Universitat Frankfurt, Germany
Rdsum6.- Le rdfrigdrateur P dilution present5 ici est le premier dont la bo?te 2 melange soit acces-- sible depuis l'extgrieur du cryostat. En outre les 6chantillons peuvent Stre changes en dix minutes pendant la ritfrigeration.
Abstract.- The dilution refrigerator presented here is the first one with access from outside the cryostat &to the mixing chamber. Furthermore the samples can be interchanged within ten minutes during the operation of the refrigerator.
The development of dilution refrigerators has been concentrated so far on reaching a low final temperature and on obtaining a high cooling power. For the solid state physicist, however, two other features are important as well : the fast and un- complicated cooling of his samples to low tempera- tures. In this respect the refrigerator described here represents a novelty.
For the interchange of samples in conventio- nal systems the cryostat has to be taken apart. This is very time consuming and causes several risks with respect to leaks for instance.
The bestway to get around these problems
-
that was our idea-
would be to feed the sample from outside the cryostat into the mixing chamber. This should be possible during the operation of the refrigerator. The cryostat described here is based on this idea with the conception that the sample inside a sample tube should find its way from out- side the cryostat into the mixing chamber in good thermal contact to all important parts of the dilu- tion refrigerator.One way-perhaps the best way- to do this (figure 1) is to place the sample tube (10) inside the pumping line (151, the still (2), the heat ex- changer (3), the mixing chamber ( 1 ) in thermal con- tact (22) to the discrete heat exchangers (4). The continuous heat exchanger consists of an outer tube
(3.3), a guide tube (3.1) with several holes and with an inner diameter equal to the diameter of the
sample tube (uncritical up to 0.1 mm difference), and of a capillary (3.2) carrying the concentrated 3 ~ e down to the mixing chamber. The diluted 3 ~ e is
locked in between the windings of the 3 ~ e capillary (3.2) and the tubes (3.1) and (3.3) and flows up- wards in a spiral to the still. The sample chamber
(21) also has some holes in order to have the sample in direct contact to the mixture.
Fig. 1 : Important parts of the fast loading dilu- tion refrigerator. On the left the sample feed through mechanism is scetched (0-ring seal and ball valve). On the right we show in detail how the sam- ple tube passes through the still (2) and the heat exchanger (3) (forming part of the heat exchanger). The other numbers are explained in the text. . ~ . - ~~ ~
X Work supported by Deutsche Forschungsgemeinschaf t/
SFB 65
In order to avoid 'He-film flux upwards in the sample tube, the waist (25) in the still can be heated. Thus the 'He-f ilm is evaporated and the va- pour condenses again at the walls of the still. The
References
'He is pumped through an electropolished tube (24) /l/ Hoenig, H.E., Lingner, C., Binnig, G. and and the wall (23) provides, that the evaporated '~e Keller, J., J. Phys.
F.
Metal Physics 1_ (1977) is not pumped too. Furthermore in figure 1 the 3 ~ e 1747/ 2 / Binnig, G., Hoenig, H.E., The Energy Gap of inletline (16) and the heat exchanger (6) and the Superconducting (SN)--, this conference
A
impedance (5) at the still (2) within the vacuum can (8) are shown.
We have completed two of these cryostats with the following properties :
(i) final temperature : 45 f: 3 mK continuously (with heat exchanger (3) only, without exchanger
(4)
(ii) Time for sample interchange : ten minutes After these ten minutes the new sample alrea- dy has a temperature of 200 mK.
