Re: How cold can I go...

[tdc@ehssun.lbl.gov (Ted M. de Castro)]

>>     A  research  lab, where I work has to, upon occasion,  check
>>equipment  operation  at very cold temperatures i.e.  77  degrees
>>kelvin  (-195  C) or colder (4.2 K).  I'm sorry that I  can't  go
>>into specific details of why (and where).

Ahhhh - space borne projects!!??

>>     2.    Does  anyone have any concrete data on  whether  these
>>double-walled   stainless  steel  capsules  can  withstand  these
>>thermal  stresses  indefinitely - or until the source becomes  so
>>old as to be impractical...Inquiring minds want to know..

Sorry - NO concrete data nor am I a materials engineer - but I do know that 
these kinds of thermal stresses certainly DO cause welds and the metal 
itself to fail!

But then - is the source large enough and in a vacuum so that its own decay 
heat helps lessen the stress somewhat??

If no concrete answers are forthcoming on this listserver - I'll try to find 
you some appropriate contacts here in our materials science group at LBL.