1. Radiation Tolerance of Resins Rad-Hard Insulation Workshop Fermilab, April 20, 2007 Dick Reed Cryogenic Materials, Inc. Boulder, CO

2. Selection of Resin System for an Irradiation Environment *Processing Characteristics *Properties What are the most significant properties to assess radiation sensitivity?

3. Low-temperature Irradiation of Resins At 4 K: formation of radicals bond breakage Warming to 295 K: recombination of radicals increased mobility of smaller gas molecules (eg., H 2 ) increased mobility of larger gas molecules (eg., CO, CO 2,CH 4 ) When 295 K is reached: evolved gas (usually more H 2 than others) swelling and increased porosity (trapped gas molecules) resin crazing (from increased internal pressure, decreased bond strength)

5. Important Resin Properties in a Radiation Environment Gas Evolution: amount of gas evolved in resin exposed to (low-temperature) radiation (primarily H 2, CO, and CO 2 ) Swelling: increase in through-thickness composite dimensions from (low-temperature) radiation (range of 0-5%) Shear/compression static and fatigue strengths: shear strengths under a range of imposed compressive stresses; short-beam shear data may be substituted for qualitative comparisons

7. Estimate of Radiation-Sensitive Properties Resin Gas Evolution Swelling 25% reduction: (cm 3 g -1 MGy -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

8. Other Factors Related to Radiation Sensitivity of Resins Radiation under applied stress at low temperatures - increases sensitivity (US/ITER/model coil)

9. Effect of applied shear/compressive prestress during irradiation at 5 K on shear strength (45 o shear/compressive test) at 4 K

10. Other Factors Related to Radiation Sensitivity of Resins Radiation under applied stress at low temperatures - increases sensitivity (US/ITER/model coil) - and results in low temperature creep (Osaka U.)

12. Other Factors Related to Radiation Sensitivity of Resins Radiation under applied stress at low temperatures - increases sensitivity (US/ITER/model coil) - and results in low temperature creep (Osaka U.) Higher energy neutrons (14 Mev) are more deleterious than predicted (LASL)

13. Effect of 14 Mev Neutrons and Gamma Ray Radiation on Kapton at 295 K

14. Neutron fluence-to- absorbed dose conversion factors: Abe,etal., RTNS-II, 295 K: 3.25 x 10 -15 Gy/(n/m 2 ) Weber, et al., Vienna, 330 K: 5.3 x 10 -15 Gy/(n/m 2 ) Gerstenberg, et al., Garching, 5 K: 3.3 x 10 -15 Gy/(n/m 2 )

15. 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.)

17. Sources of Information Proc. ICMC, Advances Cryogenic Engineering – Materials, Plenum Press, New York, vols 22-46 (1977-2000); AIP Conference Proceedings, vols 48-52, (2002-2006) N. Simon, A Review of Irradiation Effects on Organic Superconductors, NISTIR 3999, NIST, Boulder, CO (1993) R. Reed, et al, U.S. ITER Insulation Irradiation Program: Final Report (1995) D. Evans, R. Reed, Gas Evolution from Potential ITER Insulating Materials, U.S. ITER Insulation Irradiation Program Report (1995) D. Evans, R. Reed, Effects of Applied Stress during Irradiation on the Shear/Compressive Strength of Insulation, U.S. ITER Insulation Irradiation Program Report (1997) Abe, et al., Irradiation Effects in Kapton Polyimide Film from 14-Mev Neutrons and Cobalt-60 Gamma Rays, ASTM STP 956 (1988) Nishiura, et al., Enhanced Creep of Epoxy Resin during Irradiation at Cryogenic Temperatures, Advances Cryogenic Engineering-Materials, Plenum Press, NY, vol 44 (1998) 291-297