Magnet Radiation Issues Giorgio Ambrosio Fermilab

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Magnet Radiation Issues Giorgio AmbrosioFermilab
LARP Collaboration Meeting 13 Port
Jefferson Nov. 4-6, 2009

• Outline
• - Summary of Radiation Hard Insulation Workshop
• Updates and other programs
• Options

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Rad-Hard Insulation WorkshopFNAL April 07
Talks on the LARP plone at https//dms.uslarp.or
g/MagnetRD/SupportingRD/Rad_Hard_Insul/Apr07_works
hop/
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Questions

• Develop plan to arrive to these answers
• Can this magnet withstand the expected radiation
  dose?
• We should be able to reply either
• - Yes it can, and we have data to demonstrate
  it
• - No it cannot, but we have tested a TQ with an
  insulation/impregnation scheme that can withstand
  the expected dose

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Radiation Environment in the LARP IR Magnets and
Needs for Radiation Tests
Rad-Hard Workshop
Fermilab
Nikolai Mokhov Fermilab

• Rad-Hard Insulation Workshop
• Fermilab, Batavia, IL
• April 20, 2007

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OUTLINE

• IR Energy Deposition-Related Design Constraints
• Basic Results for LHC IR at Nominal Luminosity
• Dose in IR Magnets at 1035 for 3 Designs
• Particle Energy Spectra etc.
• Radiation Damage Tests

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LHC IR QUENCH LIMITS AND DESIGN CONSTRAINTS

• Quench limits and energy deposition design goals
• NbTi IR quads 1.6 mW/g (12 mJ/cm3) DC (design
  goal 0.5 mW/g)
• Nb3Sn IR quads 5 mW/g DC (design goal 1.7 mW/g)
• Energy deposition related design constraints
• Quench stability keep peak power density emax
  below the quench limits, with a safety margin of
  a factor of 3.
• Radiation damage use rad-resistant materials in
  hot spots with the above levels, the estimated
  lifetime exceeds 7 years in current LHC IRQ
  materials RD is needed for materials in Nb3Sn
  magnets.
• Dynamic heat load keep it below 10 W/m.
• Hands-on maintenance keep residual dose rates
  on the component outer surfaces below 0.1
  mSv/hr.
• Engineering constraints are always obeyed.

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Quad IR Power Density and Heat Loads vs L

The goal of below the design limit of 1.7 mW/g is
achieved with Coil ID 100 mm. W25Re liner
6.21.5 mm in Q1, and 1.5 mm in the rest
Total dynamic heat load in the triplet 1.27,
1.47 and 1.56 kW for L23, 19.5 and 17.4 m
Peak dose in Nb3Sn coils 40 MGy/yr at 1035 107
s/yr
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Peak Dose Neutron Fluence in SC Coils
IR magnets Luminosity, 1034 cm-2s-1 D (MGy/yr) at 107 s/yr Flux ngt0.1 MeV (1016 cm-2)
70-mm NbTi quads 1 7 0.3
100-mm Nb3Sn quads 10 35 1.6
Block-coil Nb3Sn quads 10 25 1.2
Dipole-first IR Nb3Sn 10 15 0.7

Both increase 5 times
Shell-coil quads at 1035 Averaged over coils D
0.5 MGy/yr, at slide bearings 25 kGy/yr
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Radiation Damage Tests (1)

• Peak dose in the LHC Phase-2 Nb3Sn coils will be
  about 200 MGy over the expected IR magnet
  lifetime. Seems OK for metals and ceramics, not
  OK for organics. It is gt 90 due to
  electromagnetic showers, with ltEggt 7 MeV and
  ltEegt 40 MeV test coil samples (and other
  magnet materials) with electron beams.
• 2. Hadron flux seems OK for Tc and Ic, but needs
  verification for Bc2. Hadron fluxes (DPA) are
  dominated by neutrons with ltEngt 80 MeV, the
  most damaging are in 1 to 100 MeV region. Very
  limited data above 14 MeV for materials of
  interest (e.g., APT Handbook).

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Radiation Damage Tests (2)

• Propose an experiment with Nb3Sn coil fragments
  (and other magnet materials) at a proton
  facility with emulated IR quad radiation
  environment (done once with MARS15 for the
  downstream of the Fermilab pbar target). Look at
  BLIP (BNL), Fermilab, and LANL beams.
• One of the important deliverables a
  correspondence of data at high energies to that
  at reactor energies (scale?).
• 5. Do we need beam tests at cryo temperatures?
• 6. Analyze if there are other critical regions in
  the quads with the dose much lower than all of
  the above but with radiation-sensitive materials.
  For example, is it OK 10 kGy/yr on end parts,
  cables etc.?

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Radiation Effects on Nb3Sn, copper and inorganic
insulation
Al Zeller NSCL/ MSU
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General limits for Nb3Sn
Nikolai Dose 200 MGy Neutrons 1021 n/m2

• 5 X 108 Gy (500MGy) end of life
• Tc goes to 5 K 5 X 1023 n/m2
• Ic goes to 0.9 Ic0 at 14T 1 X 1023 n/m2
• Bc2 goes to 14T - 3 X 1022 n/m2
• NOTE En lt 14 MeV
• Damage increases as neutron energy increases

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Important Note All of the radiation studies on
Nb3Sn are 15-25 years old and we have lots of new
materials.
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Need new studies
But I may be able to help. Have funding for HTS
irradiation, so may be able to irradiate
Nb3Sn Need place to test samples

• Hot samples ? transp/handling isuess
• Should we do it?
• Can we use results of other programs (ITER, )?

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Copper Radiation increases resistance
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From the Wiedemann-Franz-Lorenz law at a constant
temperature?? constant Thermal conductivity
decreases Minimum propagating zone
decreasesLmpz ??(?(Tc-To)/?j2) So Lmpz -gt ?
Should check if this may affect our magnets
flux is smaller but energy is higher
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 Can cause swelling, rupture of containment
vessel or fracturing of epoxy
Problem
This is 40 cm3/g in one year!
Gas evolutionRanges from 0.09 for Kapton to gt1
cm3/g/MGy for other epoxiesGas is released upon
heating to room temperature
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Big caution Damage in inorganic materials is
temperature dependent. Damage at 4 K, for some
properties, is 100 times more than the same dose
or fluence absorbed at room temperature. Since
Nb3Sn has a useful fluence limit of 1023 n/m2,
critical properties of inorganic insulators
should be stable to 1025 n/m2 at 4 K. Note that
electrical insulation properties are 10 times
less sensitive than mechanical ones.
This is concerning!
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Radiation Tolerance of Resins
We need epoxy resin or equivalent material for
coil impregnation

• Rad-Hard Insulation Workshop
• Fermilab, April 20, 2007
• Dick Reed
• Cryogenic Materials, Inc.
• Boulder, CO

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(No Transcript)
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Estimate of Radiation-Sensitive Properties

• Resin Gas Evolution Swelling
  25 reduction
• (cm3 g-1MGy-1) ()
  dose/shear strength (4,77K)
• DGEBA,
• DGEBF/
• anhydride 1.2 1-5
  5 MGy/75 MPa
• amine 0.6 1.0
  10 MGy/75 MPa
• cyanate ester 0.6 1.0
  50 MGy/45-75 MPa
• blend
• Cyanate ester 0.5 0.5
  100 MGy/40-80 MPa
• TGDM 0.4 0.1 50
  MGy/45 MPa
• BMI 0.3 lt0.1 100
  MGy/38 MPa
• PI 0.1 lt0.1 100
  MGy

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Other Factors Related to Radiation Sensitivity of
Resins

• Radiation under applied stress at low
  temperatures - increases sensitivity
  (US/ITER/model coil)
• Higher energy neutrons (14 Mev) are more
  deleterious than predicted (LASL)
• Irradiation enhances low temperature creep
  (Osaka U.)

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Radiation-Resistant Insulation For High-Field
Magnet Applications Presented by Matthew W.
Hooker
Presented at Radiation-Hard Insulation
Workshop Fermi National Accelerator
Laboratory April 2006
NOTICEThese SBIR data are
furnished with SBIR rights under Grant numbers
DE-FG02-05ER84351 and DE-FG02-06ER84456 .  For a
period of 4 years after acceptance of all items
to be delivered under this grant, the Government
agrees to use these data for Government purposes
only, and they shall not be disclosed outside the
Government (including disclosure for procurement
purposes) during such period without permission
of the grantee, except that, subject to the
foregoing use and disclosure prohibitions, such
data may be disclosed for use by support
contractors.  After the aforesaid 4-year period
the Government has a royalty-free license to use,
and to authorize others to use on its behalf,
these data for Government purposes, but is
relieved of all disclosure prohibitions and
assumes no liability for unauthorized use of
these data by third parties.  This Notice shall
be affixed to any reproductions of these data in
whole or in part.
2600 Campus Drive, Suite D Lafayette, Colorado
80026 Phone [phone] www.CTD-materials.co
m
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CTD-403
Proposed substitute for epoxy resin

• CTD-403 (Cyanate ester)
• Excellent VPI resin
• High-strength insulation from cryogenic to
  elevated temperatures
• Radiation resistant
• Moisture resistance improved over epoxies
• Quasi-Poloidal Stellarator
• Fusion device
• Compact stellarator
• 20 Modular coils, 5 coil designs
• Operate at 40 to gt100C
• Water-cooled coils

QPS
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Braided Ceramic-FiberReinforcements
Proposed substitute for S2 glass

• Minimizing cost
• Lower-cost fiber reinforcements for ceramic-based
  insulation (CTD-CF-200)
• CTD-1202 ceramic binder is 70 less than previous
  inorganic resin system
• Improving magnet fabrication efficiency
• Textiles braided directly onto Rutherford cable
  (eliminates taping process)
• Wind-and-react, ceramic-based insulation system
• Enhancing magnet performance
• Insulation thickness reduced by 50
• Closer spacing of conductors enables higher
  magnetic fields
• Robust, reliable insulation
• Mechanical strength and stiffness
• High dielectric strength
• Radiation resistance

Use or disclosure of the data contained on this
page is subject to the restriction on the cover
page of this document.
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CTD Irradiation Timelines
Proposed Ceramic/Polymer Hybrids SBS Gas
Evolution at 4 K
Epoxy-Based Insulations SBS E-beam Irradiated at
4 K
1992-93 SSC GA
2008-2009 DOE SBIR NIST
HEP
Not completed
1988 CTD Founded
Fusion
Gas evolution , irradiation at 70 C
80 C
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Insulation Irradiations
Is this low shear strength acceptable in a
small area?

• Fiber-reinforced VPI systems
• CTD-101K (epoxy)
• CTD-403 (cyanate ester)
• CTD-422 (CE/epoxy blend)
• Insulation performance
• Shear strength most affected by irradiation
• Compression strength largely un-affected by
  irradiation
• Ongoing irradiations
• Ceramic/polymer hybrids
• CTD-403
• 20, 50, 100 MGy doses
• Expect to complete by 8/07

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Radiation Resistance
2009 data

• Insulation irradiations at Atomic Institute of
  Austrian Universities (ATI)
• CTD-403 (CE)
• CTD-422 (CE/epoxy blend)
• CTD-101K (epoxy)
• CTD-403 shows best radiation resistance
• CTD-422 is improved over epoxy, but lower than
  pure CE
• Irradiation conditions
• TRIGA reactor at ATI (Vienna)
• 80 gamma, 20 neutron
• 340 K irradiation temperature

77 K
77 K
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Radiation-Induced Gas Evolution
2009 data

• Gas evolution testing
• Irradiate insulation specimens in evacuated
  capsules
• As bonds are broken, gas is released into capsule
• Breaking capsule under vacuum allows gas
  evolution rate to be determined
• Test results
• Cyanate esters show lowest gas evolution rate of
  VPI systems
• Epoxies have higher gas-evolution rates
• Results consistent with relative SBS performance

Irradiated at ATI, Vienna, Austria
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Proposed 4 K Irradiation

• Low-temperature irradiations
• Linear accelerator facility
• CTD Dewar design
• Insulation characterization
• Short-beam shear
• Gas evolution
• Dimensional change
• Insulations to be tested
• Ceramic/polymer hybrids
• Polymer composites
• Ceramic insulations

Use or disclosure of the data contained on this
page is subject to the restriction on the cover
page of this document.
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Discussion

• We need to optimize absorbers from a radiation
  damage point of view
• Detailed map of damage by Mokhov,
• Effects on mechanical design by Igor (acceptable
  or not?)
• If not, increase liners and iterate
• We need to assess damage under expected dose
• Test under conditions as close as possible to
  operation conditions
• Start testing CTD-403 (cyanate ester) or other
  alternative material
• Ten stack for testing impregnation, mechanical,
  electrical and thermal properties
• Generate table with all materials (in magnet) and
  compare damage threshold with expected dose

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Other Programs (incomplete list)

• NED-EuCARD RAL started RD on rad-hard
  insulation for Nb3Sn magnets
• Initial focus on binder/sizing mat.
• CEA ceramic insulation w/o impregnation
• I dont know if its still in progress
• CERN proposal of an irradiation test facility
  that could accommodate a SC magnet (cold)
• Workshop in december

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Options

• Set acceptable dose with present
  ins./impregnation scheme ? optimize liners and
  absorbers
• - Do we have enough info for this plan?
• Perform measurement in order to set previous
  limit
• - How much aperture do we expect to gain?
• - What measurement should we perform?
• Develop more rad-hard ins/impregnation scheme
• - What measurement should we perform?

How do we want to proceed new task, WG, core
progr., ?
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EXTRA
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Quad IR Fluxes and Power Density (Dose)

Q2B
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LARP Insulation Requirements
Design Parameter Design Value CTD-1202/CTD-CF-200 Performance
Compression Strength 200 MPa 650 MPa (77 K)
Shear Strength 40-60 MPa 110 MPa (77 K)
Dielectric Strength 1 kV 14 kV (77 K)
Mechanical Cycles 10,000 Planned testing to 20,000 cycles
Relative Cost 1.00 0.20-0.30
200 MPa is yield strength of Nb3Sn Relative
cost as compared to CTD-1012PX
Use or disclosure of the data contained on this
page is subject to the restriction on the cover
page of this document.
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Enhanced Strain in Ceramic-Composite Insulation
Graceful Failure
Brittle Failure
Use or disclosure of the data contained on this
page is subject to the restriction on the cover
page of this document.
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Radiation-Induced Gas Evolution

• Gas evolution testing
• Irradiate insulation specimens in evacuated
  capsules
• As bonds are broken, gas is released into capsule
• Breaking capsule under vacuum allows gas
  evolution rate to be determined
• Test results
• Cyanate esters show lowest gas evolution rate of
  VPI systems
• Epoxies have higher gas-evolution rates
• Results consistent with relative SBS performance

Irradiated at ATI, Vienna, Austria
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Fabrication of Test Coils

• Successful test coils have been produced around
  the world using CTDs Cyanate Ester insulations
  for fusion and other applications
• Mega Ampere Spherical Torus (MAST) diverter coil
  United Kingdom
• ITER Double Pancake test article Japan
• Quasi Poloidal Stellarator (QPS) test coils USA
  (Univ. of Tennessee)
• CTD-422 used to produce accelerator magnet for
  MSU/NSCL
• Commercial use of CTD-403 in coils for medical
  systems is ongoing

QPS Test Coil USA
MAST Test Coil UKAEA
ITER DP Test Article JAEA
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Radiation-Induced Gas Evolution

• Gas evolution in polymeric materials
• Attributed to breaking of C-H bonds, releasing H2
  gas
• Gas causes swelling of insulation
• Gas evolution measurements
• Composite specimens sealed in evacuated quartz
  capsules
• After irradiation, capsule fractured in evacuated
  chamber
• Gas evolution correlated to pressure rise in
  chamber
• Dimensional change measured

Use or disclosure of the data contained on this
page is subject to the restriction on the cover
page of this document.