SNAP Shield SubGroup Meeting 
                 10:30 AM December 10th, 2003 IB1 2nd floor
          Cease, Dejongh, Diehl, Lanfranco, Marriner, Nichol, Page


    Meeting Schedule:
    Next meeting: December 24th, 2003 10:00 AM. IB1 2nd floor. 

    Agenda (of this meeting):
    Optical Studies (Herman Cease)
    Progress on the MARS Simulation (Tom Diehl)
    AOB

    Optical Studies (Herman Cease)
    ------------------------------
    Herman has built a 2D simulation of the optical components of
    the satellite. The intent is to use this to study required optical 
    properties of the inside surface of the shield. He's doing the 
    calculations in Excel and making pictures using IDEAS. The progress is 
    that the model is working; that is, the calculations reproduce
    the optical model Mike Scholl and Co. have at LBL.  The focus is 
    at the focal plane. The incident light at the limits of the 
    acceptable angles land at the correct place on the focal plane and
    so forth.  He's starting to look at reflections.
    
    Herman also showed a potential design for a small test setup
    including vacuum chamber with internal mount for a shield sample.
    It has connections so the sample could be cooled, for instance to 
    liquid N temperature.  The purpose is to test reflectance of the shield 
    material in the optical and infra-red and to test the adherance of 
    surface coatings. This sounds like something we could build and operate
    and it's consistent with our groups purpose.  We'd like to develop this 
    plan for a few more days and show it Wednesday 12/17 at the FNAL-SNAP
    meeting. Then at the next Focal Plane Meeting.

    We appreciate the quite a few communications with Mike Scholl. 

    Progress on the MARS Simulation (Tom Diehl)
    -------------------------------------------
    The strategy is to build on Igor Rahkno's work that culminated in the 
    TM in September. Igor gave his code to TD who linked it, can run it,
    and is learning how it works.  There have been some improvements in 
    MARS since (I) last used it a few years ago. There are some visual 
    interfaces that make nice displays of the geometry and can overlay 
    those with jobs results.  Igor had pictures in the TM that were made 
    with these utilities. TD practiced moving pieces around.  TD compiled
    the masses of all objects presently in the simulation. It totals 276 kg. 
    The shield was about twice as massive as is specified in the mass budget. 
    The cold plate came in at 99 kg. The silicon itself amounted to 107 grams 
    at 200 microns thick.  That this represents ~10% of the total satellite
    mass indicates that it's important to find the solution that produces
    a table of materials using the solid model. 
      Prior to the meeting Igor showed me how to extract
    the dose. Plan is to reproduce Igor's TM results, then modify the geometry
    to improve the baseline calculation. After that or perhaps simultaneously
    to work on shield material and thickness optimization.  TD showed his
    slides in the Instrumentation Meeting. They can be found on the 
    BSCW Server and in this directory at diehl_12_10_2003.ppt.

    AOB
    ---
    Peter Limon reported Mike Levy offered to get us a Solidworks seat.
    Fact is, none of the PPD engineers have a Solidworks seat. The cost
    is about $4.k + $1.5k/yr. We should either accept Mike's generosity
    or buy one ourselves.

 
                                             Cheers,
                                             Tom Diehl