SNAP Shield Subgroup Meeting
                 10:15 AM January 21st, 2004 IB1 2nd floor
                 Cease, Diehl, Lanfranco, Marriner, Nicol


 Meeting Schedule (All times are FNAL-time):
 Focal Plane Meeting:  Thursday, January 29 at 1:00 PM IB1 2nd floor w/ LBL.
 FNAL SNAP Group:      January 28 at 10:30 on WH7X.
 SNAP Shield Subgroup: Wednesday, February 04 at 10:00 AM 
                       Instrumentation Meeting with LBL follows immediately 
                       after.

 Agenda
 ------
 MARS Simulation Progress (Diehl)
 Verbal Reports from Herman and Giobatta

 MARS Simulation Progress (Diehl)
 --------------------------------
 HTD made a series of MARS runs using galactic protons from the elliptical
 orbit. This is thought to be nearly the same spectrum as would be 
 encountered at L2. He found that the thickness of the aluminum shield, 
 when modified by adjusting the density from much less than normal to twice 
 normal, had little effect on the dose in the silicon.  In fact, when all 
 the material in the model, except the silicon, was turned into vacuum, the 
 dose in the silicon from galactic protons was reduced by 1.5+-0.1. The 
 protons are making secondaries in the other material. Tom suggested that 
 this factor could be used to modify the 4 charged-particle/cm^2/s cosmic
 ray calculation by Jodi. Nikolai has said that in-general the correspondence
 between dose and hit-rate is pretty good.  In the meeting with LBL we were 
 reminded out that the correspondence between dose and number of charged hits 
 isn't straightforward, which is also correct.  
   Next, Tom wants to do a simple de/dx-range calculation at the spectrum 
 peak, do a test of dose vs. shield Z at constant density, and use the 
 particle spectra from orbit at L2.
   It was suggested in the meeting with LBL that Tom see if he can extract the 
 energy spectrum of incident particles and secondaries on the silicon. Also,
 that he find out about a Hubble Tiger Team investigating differences in the 
 rad damage effects on the wide-field camera and the ACS, which is suffering
 worse from ?neutrons?. 
   Diehl's slides are in this directory in file diehl_01_21_2004.ppt.
 
 Verbal Reports
 --------------
 Giobatta had suceeded in importing from LBL Solidworks the whole SNAP model 
 in step file format for the first time.

 Herman has had difficulty arranging drafting for the optical test stand.
 He needs roughly 9 drawings plus an assembly.  It seems all the PPD drafters
 are busy for the next 4 weeks. Diehl is to bug Crisler and Krempetz. Herman
 presented the plan for his optical tests in the Focal Plane Meeting with 
 LBL on Thursday. It was pretty well-received though I think they wanted 
 more capability to make mechanical tests on the adherence of the 
 optical black to the shield material, whatever they will be. We will put
 more test capability in the design. Also, Herman was to check with Nick Mostek
 about photodiodes at 2 microns instead of 1.7.  Maybe we should produce a
 write-up of the tests and procedures we want.
 
   Cease and Scarpine have been working on a modified shield shape. At
 present it is kinda conical-shaped. They are considering making the top
 blunter so that more light can be reflected out.  Apparently it's not
 a "Winston Cone", though, which is skinnier in aspect. Herman presented it
 in the Thursday Meeting. Determination of the shape has gotten tangled-up in 
 a discussion of the shutter design and the thickness of the flat-fold mirror. 

   All of Herman's slides are on the Jan 22 Focal Plane Meeting page
 in BSCW.
 
  LBL will see about one Solidworks license for FNAL-SNAP use.
   

                                               Cheers,
                                               Scribe