The construction and method of working of a helium adsorption pump are described. The flux of helium-2 film can be suppressed by an appropriate construction, which permits it to reach temperatures down to 0.71 K. By total utilization of the pump's cross-section, temperatures from 1.2 K to 0.71 K remain constant for several hours with a precision of 0.001 K

Frommann, G.

Keck, K.

English

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NASA TM-75336 
NASA TECHNICAL MEMORANDUM 
A HELIUM ADSORPTION PUMP FOR TEMPERATURES 
BETWEEN 0.71 AND 1.2 K 
G. Frommanf and K. Keck 
(NAS-itf-7533 6 ) -A HELIUDI-ADS ORPTIOI' PUMP1 
FOR TEMPERATURES BETWEEN' Cfll AND 1.2 K 
(National Aeronautics and Space 
Administration) - 7 p HC A02/MF A01 CSCL 13K G3/37 
N-18-264 
Unclas 
23395 
4 8 
Translation of "Eine Heliumadsorptionspumpe fur
 
Zeitschrift
Teeieraturen zwischen 0..71 und 1.2 K",, 
An dteP ik (West Germany) Vol. 31, Nos.fu e w 
"u 691pp._28-269 
,E6_19 
! JUL1978 ' 
RECEIVED D 
8ThFACILITY~HNAS  
NATIONAL AERONAUTICS AND SPACE ADMIISTRATION
 
JULY 1978
WASHINGTON, D. C. 20546 
https://ntrs.nasa.gov/search.jsp?R=19780018505 2020-03-22T03:10:25+00:00Z
STANDARD TITLE PAGE 
1. Report No. 2. Govetrneni Accession No. 3. Recipient's Cotolog No. 
N~ASA TM-75336 
4. Title d Subtitle . 5. Repott Date 
A ELIUM- ADSORPTION PUMP FORJuly 1978 
6. Performing Organization Cod .HE "EN I .1O.I 
7. Author(s) 8. Performing Organization Report No. 
G. Frommann and K. -Keck, 10. Work Unit No. 
9. Performing Organizo~ton Name and Address 11. Contract or Grant No. 
- NASW-2791
SGITRAN 
13. Type of Report and Period CoveredP. O.wBox 5456 
Santa Barbara; CA 93108 Translation
 
12. Sponsoring Agency Noa and Address'
 
National Aeronautics and Space Administration 14. Sponsoring Agency Cod.
 
Washington, D. C. 20546 
IS. SuppIam*entry Notes 
Translation of "Bine Ifeliumadsorptionspumpe fur Temperaturen zwischen
 
0.71 und 1.2 K",i -Zitsochiftfuer-Angeante-Ehysik tGer=any=)_: _ 
Vol 31 Ns. _hi5_ 9_71 ,-pp-o_ 58-26Q. ­
.16 Absut a 
17. Key Words (Selected by Author(s)) Distflbtiann Statement-1. 
Unclassified - Unlimited 
19. Scurity ClossIf(of tht. rport)" 20" Scurity Classf. (of this pog.) 21. N. of Pgni 22. 
A HELIUM ADSORPTION PUMP FOR TEMPERATURES BETWEEN 0.71 AND 1.2 K /258*
 
G. Frommann and K. Keck**
 
The construction and method of working of a helium adsorption
 
pump are described. The'flux of helium-II film can be suppressed by
 
an appropriate construction, which permits to reach temperatures down
 
to 0.71 K. By total utilization of the pump's cross-section, tempera-.
 
tures from 1.2 K to 0.71 K remain constant for several hours with a
 
precision of 10- 3K.
 
Introduction
 
One obtains He-bath temperatures of the maximum of 1.0 K using /259.
 
vapor pressure reduction, and a He-bath usingrotating vacuum pumps.
 
At these temperatures and laier temperatures,- the vaporization of the
 
helium primarily no longer, occurs at the liquid surface, but ihstead
 
this occurs due to the presence of a He-film, which rises without fric­
tion to regions of higher temperature along the vessel walls of the
 
cryostat.
 
This means that in this temperature range,, substantially higher
 
suction rates are required, which can be produced by adsorption pumps
 
[ll. The active carbon used as the adsorption agent has the capability
 
of the temperature of liquid helium to adsorb a substantial amount of
 
He-gas. Such a pump has been described by Eselson and Shvets [2],
 
Using a measurement chamber of 8 cm2 , and a temperature of 0.704 K,
 
they were able to maintain it over a forty-minute interval. By using
 
a small diaphragm, which was to prevent the propagation of the He-film,
 
the suction performance of the adsorption carbon was substantially re­
duced.
 
In the following paper, we will describe an adsorption pump, in
 
*Numbers in margin indicate pagination in foreign text.
 
**Institute for Physics at the University bf Mainz.
 
1
 
A 
14 
S K 
tLL 
w 
.-fi "h 
* Di 
S ORIGINAL PAGe S 
- .R op POO)R QUALMT 
-f 
Figure 1: Cryostat. A- level indicator M- Motor K-stainless steel
 
tube. Au- Lift W- Contact springs D - Helium Dewar .
 
R- measurement
D - -Measurement Chamber S tube enclolure 
r~sistor. 
which the.suction cross-section and therefore the adsorption capacity
 
are completely avoided. This allows fast and convenient operation of
 
the pump. Another advantage of this .design"is the fact that the tem­
perature can be held constant within + 2 x 10-3K over several hours.
 
Also, any temperature between 0.7 K and 1.2 K can be easily adjusted.
 
.Cryostat, Design, and Operation-

First we will describe the cryostat and the adsorption pump.
 
(Figure 1). There is a pump in a thin-wall stainless steel tube K.
 
The lower end of it is the measurement chamber D2 ,-in which the low
 
temperature is to be created. The stainless steel tube (110 cm long,
 
3 cm inner diameter), is pre-cooled in a He-Dewar D1 down.to 1.2 K.
 
At the upper edge of the tube K, there is an electrical motor M, which
 
can move the vessel Au (called the lift-in the following) with-the
 
2 
adsorption agent in the tube up and down. Molecular sieves (metal­
alumino silicate) are used as adsorption agents.
 
The lift (Figure 2a) is inside a stainless steel tube 20 cm long,
 
a cone K made of stainless steel mesh is soldered to the base of the
 
tube, in order to obtain the maximum possible area for the 75 g of ad­
sorption agent inside the lift. For better thermal contact with the
 
tube K and for better control, there are bronze springs W on the lower
 
K
°A 
_K 
S2 
ORIGINAL PAGE 1 
OF POOR QUALYI 
w 
a) b) 
Figures 2a, 2b: 	 2a: Lift: A- adsorption medium K- cone made of
 
wire mesh W- bronze springs
 
2b: Measurement chamber D2: K- stainless steel tube,
 
Sl tube enclosure S2- tear-off edge for helium
-

film*
 
edge of the lift. The position of the lift above the measurement in
 
the D2 can be read off from a level indicator A (Figure 1).
 
The measurement chamber D2 (Figure'2b) consists of a vessel
 
which is isolated to the outside He-bath, with a content of 20 cm3 .
 
In order to reduce heat transfer and avoid the He-film from leaving
 
the measurement dewar, ,a tube enclosure S1 with a tear-off edge S2
 
has been installed. The He-film-which is rising along the walls tears
 
off at this'point, and drops back into the He-bath in the form of
 
drops.
 
The adsorptipn pump is operated as follows: the external He­
bath in the dewar'D 1 is brought to a temperature'of 1.3 K and at the
 
same time a measured amount of He-gas is condensed in the measurement
 
dewar D2. After temperature equalization from the outer and inner He­
bath, the lift, which has been pre-cooled with liquid air, is dropped /260
 
down to the upper edge of the dewar D2 at a velocity of 2 mm/sec. There, 
the adsorption agent takes on the temperature of the external coolant 
because of the heat bridge W, and-the adsorption process starts. The 
temperature in D2 drops below 0.75 'K within five minutes (Figure 3). 
When the adsorption agent is saturated with He-gas, or if the
 
liquid He in-D 2 is used up, then the lift is again raised into the tem­
perature range of liquid air; there the He-gas is liberated and again
 
condenses in the dewar-D2. After the very short regeneration of 10-15
 
minutes, the'lift is lowered again and the adsorption process starts
 
again. This cycle can be repeated until the external coolant in D1 is
 
consumed.
 
The temperature in D2 was measured with a calibrated carbon re­
sistor R., The low temperatures were calculated using a formula given
 
by Quinnel F31:
 
R . ORIGINAL PAGE 15
*6AF' POOR QUALITy
 
Here, T is the absolute temperature, R is-the measured resistance, A,
 
B, and K are constants. Using a germanium resistor calibrated with
 
He3, it was possible to control the temperature measurement. The de­
viations of both temperature measurements from one another was a maxi­
- 3 
mum of only +.3 x l0 K.
 
Measurement results
 
Figure 3 shows the time variation of the temperature in the mea­
surement dewar D and the lift with the adsorption agents directly
 
above the dewar. The lowest achievable temperature of 0.71 K can be
 
maintained to within 2 x 10-3,K over several hours.- After 4.5 hours,
 
the helium in the dewar D2 isconsumed for the geometric conditions
 
used here, so that the regeneration process of the adsorption agent
 
discussed above must be started. Of course, the time available for
 
measurement at these temperatures depends on the heat which is intro­
duced into the measurement.dewar, by the supply lines. Of course, .there
 
is nothing against increasing the size of the measurement dewar.
 
'4
 
0.70 	 time-

I 2 3 h 
Figure 3: Time variation in the measurement chamber D
 
122
 
K 
time
 
1 2 h 
Figure 4: Temperature adjustment between 0.76 and 1.22 K.
 
The suction rate of the adsorption-agent is reduced, if the
 
lower end of the lift is a few cm above the measurement dewar. As
 
Figure 4 shows, by changing the lift height above the measurement
 
chamber, any temperature between 0.7 and 1.2 K can be adjusted, and
 
can be maintained constant over a long period to within 1 x l0- 3 K.
 
Our working group wishes to.- thank Mr.- F. -Kenntner, for his
 
information and discussion.
 
REFERENCES
 
1. Zamengof, S.: Physics 6, 47 (1939)
 
2. Eselson,.B. N., 	Shvets, A.'A.: Cryophysics 6, 274 (.1966)
 
3. Clement,- J. R., 	Quinnel, E. H.: Rev. Sci. Instr. 23, 215 (1951)
 
Dip]. Phys. Oorhzrd Fzomnmnn 
mid ?riv.-DezDr. Kim=~ KvokImtitut far Physik 
c~BRD-500 Mtai, Du 	 ORIGINAL PAGE IS 
OFPOOR QUALIY 5 


A helium adsorption pump for temperatures between 0.71 and 1.2 K

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