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A simplified helium dewar for optical studies
A simplified helium dewar for optical studies a.
HAGENE
The author is with the Laboratoire de Radmelectncite, Faculte des Soences de Rennes, France Received 12 December 1967
cm
-75
k\\\"
~P49x50 = Hehum g a s - 70
-65
;7x 70
A DEWAR meant for short time (1 to 2 h) experiments requiring irradiation with visible light of a sample placed in liquid helium has been built m a particularly simple way It is constructed without a hquld nitrogen shield, escaping hehum vapour cools a radiation shield fastened to the neck of the dewar We shall describe only a few particulars of Its construction. The apparatus Includes three concentric walls (see Figure l) The liquid helium container is a stainless-steel tube, 0 5 m m thick, carefully polished, whose lower end is hard soldered to a brass bottom bearing the windows (Figure 2)--these are annealed Pyrex disks, 2 m m thick, pressed on flat indium joints The radiation shield, in l m m thick copperplate, is made in two parts to allow access to the windows The upper part is soft soldered on a brass ring (Figure 1 (a)), itself hard soldered along its length (25 ram) to the stainless steel tube The thermlc connection with the lower part IS secured with contact fingering used in radloelectriclty To avoid inside and outside polishing on the copper tubes, they are sheathed with very bright aluminlum foil The exterior sheathing, in 1 5 m m thick brass, polished inside, is also in two parts linked with a neoprene joint The lower part bears Pyrex windows cemented with araldlte Results
-60 Vacuum
55
50
Light, and small in size, the dewar is indifferent to thermic shocks, as it comprises only one soldered joint In the helium bath It contains at most 800 cm ~ liquid helium In practice, 300 to 400 cm 3 quickly evaporate, and the rest evaporates at the mean rate of 2 cma/mIn at 418°K, and of 2 5 c m a / m i n at 2 0 ° K A two hour experiment is thus possible where the heat flux brought through the windows and by the apparatus plunged in liquid helium is very small
I
,
i8x60
-10
-i
i
See porhculors Figure 2
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. . . . . . .
"J
0 I
"//~/ / / / / / / / / / / / /
///
1 I
3 I
2 I
4 I cm
Figure 1 2,~
Figure 2 CRYOGENICS
A U G U S T 1968
HAGENE
The author is with the Laboratoire de Radmelectncite, Faculte des Soences de Rennes, France Received 12 December 1967
cm
-75
k\\\"
~P49x50 = Hehum g a s - 70
-65
;7x 70
A DEWAR meant for short time (1 to 2 h) experiments requiring irradiation with visible light of a sample placed in liquid helium has been built m a particularly simple way It is constructed without a hquld nitrogen shield, escaping hehum vapour cools a radiation shield fastened to the neck of the dewar We shall describe only a few particulars of Its construction. The apparatus Includes three concentric walls (see Figure l) The liquid helium container is a stainless-steel tube, 0 5 m m thick, carefully polished, whose lower end is hard soldered to a brass bottom bearing the windows (Figure 2)--these are annealed Pyrex disks, 2 m m thick, pressed on flat indium joints The radiation shield, in l m m thick copperplate, is made in two parts to allow access to the windows The upper part is soft soldered on a brass ring (Figure 1 (a)), itself hard soldered along its length (25 ram) to the stainless steel tube The thermlc connection with the lower part IS secured with contact fingering used in radloelectriclty To avoid inside and outside polishing on the copper tubes, they are sheathed with very bright aluminlum foil The exterior sheathing, in 1 5 m m thick brass, polished inside, is also in two parts linked with a neoprene joint The lower part bears Pyrex windows cemented with araldlte Results
-60 Vacuum
55
50
Light, and small in size, the dewar is indifferent to thermic shocks, as it comprises only one soldered joint In the helium bath It contains at most 800 cm ~ liquid helium In practice, 300 to 400 cm 3 quickly evaporate, and the rest evaporates at the mean rate of 2 cma/mIn at 418°K, and of 2 5 c m a / m i n at 2 0 ° K A two hour experiment is thus possible where the heat flux brought through the windows and by the apparatus plunged in liquid helium is very small
I
,
i8x60
-10
-i
i
See porhculors Figure 2
-o
. . . . . . .
"J
0 I
"//~/ / / / / / / / / / / / /
///
1 I
3 I
2 I
4 I cm
Figure 1 2,~
Figure 2 CRYOGENICS
A U G U S T 1968