Cryotraps design discussion, 15Jun
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_ current AdV planning:   The installation of cryotraps is planned to start in mid 2012.
                                   The call for tender can start at end 2010

_ proposed next 4 months activity: the baseline design is sufficiently detailed.
    We can now evaluate possible alternatives (with respect to cost , bubbling noise issue, easyness operation, ...)

_ for instance, the LIGO cryotrap characteristics are:  
  Aluminum cryostat, half filled to have a quick vapour/liquid separation, with large passage
  sections for the gas and smooth continuous refill . Just one thermal shield, no MLI and inner bellows.

_ A proposed  option to be evaluated is the following: aluminum shield cooled with a 'reduced' LN2 cryostat. In particular we could study the technical feasibility, the thermal gradients and the thermalization time constants. See the principle design in a forthcoming sketch.

Details on present 'baseline' trap design:
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_ MLI + inner bellows :  advantages/drawbacks 
          

_ liquid nitrogen inlet , how to get a smooth continuous and silent flow

_ gas outlet: evaporation is concentrated at trap extremities, vapour flow is about 1 liter/sec .
Bubbles growth along the path to the exit: trapping points, cryostat walls, holed stiffening rings.

_ need of one large flange and large size bellows vs the tower side

_ Phase separator design

_ fluid-dynamic liquid/bubbles study

_ exp tests