Magnet Radiation Issues Giorgio Ambrosio Fermilab

1. Magnet Radiation IssuesGiorgio AmbrosioFermilab BNL - FNAL - LBNL - SLAC LARP Collaboration Meeting 13 Port Jefferson Nov. 4-6, 2009 • Outline: • - Summary of Radiation Hard Insulation Workshop • Updates and other programs • Options

2. Rad-Hard Insulation WorkshopFNAL April 07 Talks on the LARP plone at: https://dms.uslarp.org/MagnetRD/SupportingRD/Rad_Hard_Insul/Apr07_workshop/

3. 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”

4. Rad-Hard Workshop Fermilab Radiation Environment in the LARP IR Magnets and Needs for Radiation Tests Original slides, I added comments and underlines Nikolai Mokhov Fermilab Rad-Hard Insulation Workshop Fermilab, Batavia, IL April 20, 2007

5. 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

6. 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; R&D 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.

7. 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: 6.2+1.5 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 L*=23, 19.5 and 17.4 m Peak dose in Nb3Sn coils 40 MGy/yr at 1035 & 107 s/yr

8. Peak Dose & Neutron Fluence in SC Coils Both increase 5 times Shell-coil quads at 1035: Averaged over coils D ~ 0.5 MGy/yr, at slide bearings ~ 25 kGy/yr

9. 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 > 90% due to electromagnetic showers, with <Eg> ~ 7 MeV and <Ee> ~ 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 <En> ~ 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).

10. 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 beamtests 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.?

11. Radiation Effects on Nb3Sn, copper and inorganic insulation Al Zeller NSCL/ MSU

12. Nikolai: Dose: 200 MGy Neutrons: 1021 n/m2 General limits for Nb3Sn: 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 < 14 MeV Damage increases as neutron energy increases

13. Important NoteAll of the radiation studies on Nb3Sn are 15-25 years old and we have lots of new materials.

14. 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, …)?

15. Copper Radiation increases resistance

16. Should check if this may affect our magnets: flux is smaller but energy is higher From the Wiedemann-Franz-Lorenz law at a constant temperatureλρ = constantThermal conductivity decreasesMinimum propagating zone decreases:Lmpz = ((Tc-To)/j2)So Lmpz -> λ

17. Problem: Can cause swelling, rupture of containment vessel or fracturing of epoxy This is 40 cm3/g in one year! Gas evolutionRanges from 0.09 for Kapton to >1 cm3/g/MGy for other epoxiesGas is released upon heating to room temperature

18. 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!

19. 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

21. 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 <0.1 100 MGy/38 MPa PI 0.1 <0.1 100 MGy

22. 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.)

23. 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 andDE-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: 303-664-0394 • www.CTD-materials.com

24. 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 >100°C Water-cooled coils CTD-403 Proposed substitute for epoxy resin QPS

25. 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 Braided Ceramic-FiberReinforcements Proposed substitute for S2 glass Use or disclosure of the data contained on this page is subject to the restriction on the cover page of this document.

26. CTD Irradiation Timelines 1992-1998 ITER Garching/ATI 2005-2007 DOE SBIR MIT-NRL 2000-2003 DOE SBIR ATI Epoxy-Based Insulations SBS, Compression Shear/Compression at 4 K Resins & Ceramic/Polymer Hybrids SBS, Compression Adhesive Strength Gas Evolution Epoxies & Cyanate Esters SBS, Compression Gas Evolution 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

27. Insulation Irradiations Is this low shear strength acceptable in a “small” area? Nikolai: Peak dose in 1 year • 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

28. Radiation Resistance 2009 data 77 K • 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

29. 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 Radiation-Induced Gas Evolution 2009 data Irradiated at ATI, Vienna, Austria

30. 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.

31. 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

32. Other Programs (incomplete list) • NED-EuCARD: RAL started R&D on rad-hard insulation for Nb3Sn magnets • Initial focus on binder/sizing mat. • CEA: ceramic insulation w/o impregnation • I don’t know if it’s still in progress • CERN: proposal of an irradiation test facility that could accommodate a SC magnet (cold) • Workshop in december • … G. Ambrosio - Long Quadrupole

33. 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.,… ? G. Ambrosio - Long Quadrupole

34. EXTRA

35. Quad IR: Fluxes and Power Density (Dose) Q2B

36. LARP Insulation Requirements *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.

37. 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.

38. 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 Radiation-Induced Gas Evolution Irradiated at ATI, Vienna, Austria

39. Fabrication of Test Coils • Successful test coils have been produced around the world using CTD’s 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

40. 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.