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  Equilibrium Crystal Shape of 4He under Microgravity
 

 

 
 

Time: 1:20pm, November 5 (Thursday)

Title:Equilibrium Crystal Shape of 4He under Microgravity
-----Collaboration of low temperature and microgravity-----

Speaker: Prof. Yuichi Okuda
     (RIKEN, Japan)

Place: Science Building III 1F SC157

Abstract:
Solid 4He is produced by applying the pressure above 25 bar on the supersfluid at low temperatures. Unique properties of solid 4He come from the fact that it is in the equilibrium with superfluid. The latent heat is negligible, the mass transport for crystallization is carried out via superfluid, and any impurities are frozen out from superfluid. So, the growth coefficient goes up divergently towards T=0. The relaxation time at 0.1 K would be less than 1 second. So, solid 4He is the best material to study the crystal shape at low temperatures. On the other hand, the gravity on the ground would deform the crystal easily, masking the true shape of crystal. The, in order to observe the real equilibrium shape of crystal (ECS), the microgravity environment is definitely needed. Fortunately, JAXA (Japan Aeronautical Exploration Agency) offered the ground-based research program, seeking for the interesting experiments on ISS. We got started the project to produce the 4He crystal on a small jet plane, aiming at observing ECS of solid 4He, supported by JAXA. Recently we succeeded in observing ECS on the jet plane. At the seminar, the analysis of ECS would be presented, together with interesting movies.

References
1. New J. Phys. 14, 123023-1-11 (2012)
http://iopscience.iop.org/1367-2630/14/12/123023/
http://www.iop.org/news/12/dec/page_59131.html
2. Science Advances, to be published, 2015.

 

 

     
 
Update: 2015/10/29
Contacts: Li-Chun Chen

 
   
 
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