A Continuous 4He Refrigerator for Use in a Superfluid Helium Bath

2006 ◽  
Author(s):  
Suwen Wang ◽  
D. Avaloff ◽  
J. A. Nissen ◽  
D. A. Stricker ◽  
J. A. Lipa
Keyword(s):  
Superfluid Helium ◽  
Helium Bath

Variable transfer rates in superfluid helium films

1966 ◽  
Vol 290 (1420) ◽  
pp. 1-13 ◽  
Keyword(s):  
Thick Film ◽  
Superfluid Helium ◽  
Transfer Rate ◽  
Bath Surface ◽  
Helium Films ◽  
Third Sound ◽  
Transfer Rates ◽  
Superfluid Flow ◽  
Helium Bath ◽  
The Difference

From an experimental investigation of superfluid film transfer in narrow beakers in helium II it emerges that there are probably two kinds of film. A ‘normal’ film is formed by superfluid creep over a dry substrate. A ‘thick’ film remains when liquid has drained from a substrate that has previously been immersed in the liquid helium bath. A comparison has been made of the superfluid flow between the two types of film. Scatter of values of transfer rate associated with a normal film is attributed to third sound generated by bath waves impinging on the meniscus at the base of the film. The thick film shows an enhanced rate of transfer which can persist for long periods of time in quiet conditions, but which can be abruptly diminished by disturbances such as bath surface agitation. There is a maximum stable length for a thick film exhibiting the full enhanced rate. The enhanced rate can be as much as 60% greater than the normal rate at 1° K, but the difference between the two rates of transfer disappears above 1.8 °K. No enhanced rate of transfer at any temperature is observed in beakers as large as 8 mm diameter.

High-Resolution Cryo-Electron Microscopy of Biological Macromolecules

1990 ◽  
Vol 48 (1) ◽  
pp. 126-127
Author(s):  
Yoshinori Fujiyoshi
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Diffraction Pattern ◽  
Superfluid Helium ◽  
Copper Phthalocyanine ◽  
Optical Diffraction ◽  
Irradiation Damage ◽  
Biological Macromolecules ◽  
Cross Sectional ◽  
Instrumental Resolution

The resolution of direct images of biological macromolecules is normally restricted to far less than 0.3 nm. This is not due instrumental resolution, but irradiation damage. The damage to biological macromolecules may expect to be reduced when they are cooled to a very low temperature. We started to develop a new cryo-stage for a high resolution electron microscopy in 1983, and successfully constructed a superfluid helium stage for a 400 kV microscope by 1986, whereby chlorinated copper-phthalocyanine could be photographed to a resolution of 0.26 nm at a stage temperature of 1.5 K. We are continuing to develop the cryo-microscope and have developed a cryo-microscope equipped with a superfluid helium stage and new cryo-transfer device.The New cryo-microscope achieves not only improved resolution but also increased operational ease. The construction of the new super-fluid helium stage is shown in Fig. 1, where the cross sectional structure is shown parallel to an electron beam path. The capacities of LN2 tank, LHe tank and the pot are 1400 ml, 1200 ml and 3 ml, respectively. Their surfaces are placed with gold to minimize thermal radiation. Consumption rates of liquid nitrogen and liquid helium are 170 ml/hour and 140 ml/hour, respectively. The working time of this stage is more than 7 hours starting from full LN2 and LHe tanks. Instrumental resolution of our cryo-stage cooled to 4.2 K was confirmed to be 0.20 nm by an optical diffraction pattern from the image of a chlorinated copper-phthalocyanine crystal. The image and the optical diffraction pattern are shown in Fig. 2 a, b, respectively.

VISCOSITY OF NORMAL AND SUPERFLUID HELIUM THREE

1978 ◽  
Vol 39 (C6) ◽  
pp. C6-35-C6-36 ◽  
Author(s):  
J. M. Parpia ◽  
D. J. Sandiford ◽  
J. E. Berthold ◽  
J. D. Reppy
Keyword(s):  
Superfluid Helium ◽  
Helium Three
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