MARS Simulation Progress

1
MARS Simulation Progress

• Tweaking the geometry
• Dose vs. Shield thickness
• Dose w/ vs. w/o a satellite
• Next steps

Tom Diehl 01/21/2004
2
Recent History

• Igor Rakhno Co. wrote
• Preliminary Results from MARS Calculations FNAL
  Technical Memo 2221 Mokhov, Rakhno, Striganov,
  Peterson Radiation Load to the SNAP CCD
  09/15/03.
• Modeling the Cosmic Rays
• SNAP Satellite Model
• Preliminary Dose Calculations
• We know we have some things to improve.
• We know we have some systematic tests to carry
  out.
• Igor sent me his code.

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Shielding and Detector Model (Rakhno)
4
The Rakhno Model

• The total mass included amounts to 276 kg.
• Shield is 2 cm thick, 35 to 41 kg aluminum.
• Cold Plate is 99 kg moly.
• Silicon substrate is 5 kg mixture.
• Silicon itself is 200 m thick amounting to 107 g.
• Radiator is 69 kg aluminum.
• The rest is deck, optical bench, supports, etc
  amounting to 61 kg.
• I modified the cold plate to 49 kg, close to the
  nominal design.I did this by halving the density
  of the molybdenum.

5
Progress Dec. 10th to Dec 31st.

• I learned MARS 14 tricks, pictures, plots.
• Reran Igors code
• Same Orbit (solar minimum) 10M galactic protons
  gt 6.8 R/y. Igor had 7.9 R/y.
• Same orbit (solar minimum) 100M trapped protons
  gt 34 kR/y. Igor had 21 kR/y.
• The program is functioning properly when I run
  it. Well I get approx. the same results as Igor
  does using that geometry.

6
Dose vs. Shield Thickness (AL)

• The shield in the nominal geometry is 2 cm thick
  aluminum cone. Is there an optimal thickness?

• Test dose in the silicon as change thickness (AL
  density) of the shield.
• A much thicker shield will block these protons
  effectively.
• No apparent reason to make the shield 35 kg.

2.7 g/cc
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Material vs. No Material

• Jodi L. has a fast cosmic ray simulation using 4
  charged particles/cm2/s. Thats the textbook
  unprotected rate. I can calculate a scale
  factor that accounts for the material.
• I set all the material to vacuum, except the
  silicon, and reran MARS, 10 M galactic protons
  10M galactic electrons, elliptical orbit.
• Dose (silicon) 4.7 R/y, less than with the
  material around the detector.
• Ratio (satellite vs. no satellite) 1.5 - 0.1
  from galactic protons.
• R 2.0- 0.2 from galactic electrons. But the
  electrons are 100 x less than the protons,
  anyway.

8
More Progress since Dec. 10th

• Nibble File (Cease, Page, Lanfranco)
• Solidworks Model -gt IDEAS CAD Program
• Step through the satellite volume in small cubes
• Report the material in each cube, its position,
  density, name, mass, and volume.
• I can turn this into a table suitable for MARS.
  Maybe it will be suitable for GEANT, as well.

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Summary Immediate Plan

• Change to L2 Orbit.
• The galactic spectrum will be similar to the
  elliptical orbit spectrum.
• Trapped radiation goes away
• Verify the shield thickness calculation
• Test some different materials
• Dose vs. Z at constant mass
• Polyethylene Lithiated polyethylene (may not be
  wise to use poly, but want to check that anyway)
• 2 material sandwich
• Start importing simple nibbled Solidworks parts.

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Buffer slide

• Stuff here on isnt part of this talk.

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Shielding and Detector Model (1)

• The trick with MARS is to select the appropriate
  level of detail.
• Include the most important shielding components.
  Consideration is given to proximity to detector
  and components mass.
• Put a lot of effort into detailing the detector.

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Microsoft Project Stuff
Done x

• I sketched this up Nov. 2003 _at_ Collaboration
  Meeting.
• I only show details for MARS stuff.
• I rolled up the rest.
• This isnt up to code
• it could already stand to be updated.

x
x
x
12/30/2003