# Presentation: 947461

## MARS Simulation Progress

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

- Tom Diehl
- 01/21/2004

## 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.

## Shielding and Detector Model (Rakhno) 

## 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  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.

## Progress Dec. 10th to Dec 31st.

- I learned MARS 14 tricks, pictures, plots.
- Reran Igor’s code
- Same Orbit (solar minimum) 10M galactic protons => 6.8 R/y.  Igor had 7.9 R/y.
- Same orbit (solar minimum) 100M trapped protons => 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.

## 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

## Material vs. No Material

- Jodi L. has a fast cosmic ray simulation using 4 charged particles/cm^2/s. That’s 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.

## More Progress since Dec. 10th

- “Nibble File” (Cease, Page, Lanfranco)
- Solidworks Model -> IDEAS CAD Program
- Step through the satellite volume in small cubes
- Report the material in each cube, it’s 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.

## 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.

## Buffer slide

- Stuff here on isn’t part of this talk.

## 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.

## Microsoft Project Stuff

- I sketched this up ~ Nov. 2003 @ Collaboration Meeting.
- I only show details for MARS stuff.
- I rolled up the rest.
- This isn’t up to code
- & it could already stand to be updated.

- x

- x

- x

- Done = x

- 12/30/2003