The Radiation Shields

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The Radiation Shields
SNAP Collaboration Workshop March 27-30, 2003 LBL

• The Fermilab Shield Group
• Plan Progress for Radiation Shields

Tom Diehl
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The Fermilab Shield Group
(At Present)

• Physicists Fritz DeJongh, Tom Diehl, Sandor
  Fehers, Nikolai Mokhov, Igor Rakhno, Sergei
  Striganov
• Engineer/Designers Tom Peterson, Clark Reid

Temporary location of web page http//www-d0.fnal
.gov/diehl/Public/snap/snap.html
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The General Plan

• Develop a simulation of the satellite
• Import the Model
• Find out how much material is in the components
• Describe the important parts of the satellite and
  detector geometry
• Obtain a parameterized description of the sources
• Use Spenvis, MARS GEANT, etc to simulate the
  effect of the material on the rate and dose
  obtained by the electronics during an event
• An event is an orbit
• An event is an exposure
• Get the best shield we can within material
  constraints

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SPACECRAFT CONFIGURATION
Secondary Mirror Hexapod and Lampshade Light
Baffle
This is to remind me!
Door Assembly
Main Baffle Assembly
Secondary Metering Structure
Primary Solar Array
Primary Mirror
Optical Bench
Solar Array, Dark-Side
Instrument Metering Structure
Instrument Radiator
Tertiary Mirror
Fold-Flat Mirror
Instrument Bay
Spacecraft
Shutter
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The Shield Components

• The shield consists of a conical object 2/3m
  tall 2/3 meter wide.
• Multi Purpose
• Ionizing radiation
• Thermal Isolation of detector
• Block or absorb stray light

• All material is potentially shielding
• Cold plate behind the shield
• Other satellite components

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Important Shielding Components

• The dewar and cold plate
• The optical bench forms a container around the
  dewar. What is it made of?
• MLI covers everything
• The mirrors. What are they made of?
• The radiator is the main thing behind the cold
  plate. What about it?

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Importing the Model

• text

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The SNAP Orbit

• FD found out the apogee is 152830 km and the
  perigee is 10000 km.
• Inclination is 26.3 deg.
• Closed Orbit takes 3 days.

Scale picture of the orbit.
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Sources of Radiation

• Trapped Radiation Belts
• Protons peak at 3000 km
• Electrons peak at 3000 and 25000 km
• Galactic Cosmic Rays
• 4 particles /CM2/S 108 to 1019 eV
• 85 p, 14 a, 1 heavier elements
• Produces single event effects
• Solar Proton Events
• Flares can last for days
• We have references for all of this.

These pictures are from The Space Environment
by Alan C. Tribble.
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Scale Picture of Radiation Belts
Orbit (to scale) Overlaid with Trapped
radiation Plot (to same scale).
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Mars Geant Simulation

• Mars Simulation
• Weve a lot of experience in HEP applications
• Mokhov is the author/maintainer of Mars
  simulation and a member of NASA radiation group.
• S.S. and I. R. are incorporating heavy ion
  interactions into Mars.

• Geant Simulation
• Common geometry possible so thats its not much
  additional work

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Summary Outlook

• The Fermilab Shield Group has started work on the
  multipurpose radiation shields
• We have a plan for understanding the effect of
  the shielding on ionizing radiation and are
  beginning to carry it out.
• Getting a grasp of the thermal radiation and
  visible light shielding issues comes next.
  Mechanical, as well.

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Humbling thought for the day?

• Nah!