SNAP Shield SubGroup Meeting 
                   10:00 AM October 15th, 2003 IB1 2nd floor
                Cease, Diehl, Lanfranco, Nichol, Olis, Rakhno


    Meeting Schedule:
    Next meeting: October 29, 2003 10:00 AM. IB1 2nd floor. Followed
    by the Instrumentation Meeting with LBL.  Approximate agenda will be
    10:00 to 10:30 Tuning the R&D plan (all)
    10:30 to 11:00 Cosmic Ray Simulation (Jodi Lamoureux).
    AOB

    Agenda (of this meeting):
    TM 2221 - Igor Rakhno
    Advice from Nikolai Mokhov - Igor Rakhno

    TM 2221 - Igor Rakhno
    ---------------------
    TM 2221 is complete. It is titled "Radiation Load to the SNAP CCD"
    by Mokhov, Rakhno, Striganov, and Peterson. One can download it from 
    http://www-d0.fnal.gov/~diehl/Public/snap/meetings/tm-2221-09-15-2003.pdf
    for now.

    Igor presented this note using slides taken from it. The skinny is
    that the galactic (primary) hadrons and electrons contribute 11.4 rad 
    per year with the main component being secondary neutrons generated by 
    proton interactions with the cold plate. The trapped radiation (Van Allen 
    belts) contribute 28.4 krad per year. The shielding is partially 
    effective in stopping these particles because they are low energy.
    However, there are orders of magnitude more of them than primaries.
    See the memo. It is possible to block more of these if the shutter was 
    closed during the transit through the trapped particles. But that
    calculation wasn't done. We should be taking that up next, I think.
    Also, it would be interesting to see the effect on the primary rad.
    dose if the material for the shield was changed from aluminum.  
      Depending on the expected rate of degeneration of the CCD's,
    after 4 years the CCD's  signal would be reduced by 40-73%.

      Questions, comments, and some answers can be found in 
    this directory at tm-2221-comments.txt.

    Advice from Nikolai Mokhov - Igor Rakhno  
    ----------------------------------------
    Igor reported that Nikolai advises us to use high-Z material to 
    stop protons and low-Z material to stop neutrons. 

                                              Cheers,
                                             Tom Diehl