Driver-chamber interface: lasers (contíd.)

• Neutrons scattered off of the final optical component (wedge or GIMM) dominate the fast neutron flux at the focusing mirrors:

  • Relatively sensitive focusing mirrors may have fast neutron fluence limit of only 1018-1019 n/cm2 leading to a lifetime of only 0.25-2.5 FPY

• Final focusing mirror dose rate is dominated by neutron-induced gamma-rays:

  • 4 Gy/s at mirror location (200_ higher than neutron dose rate)
  • Recent work1 shows that g-ray dose is important for transmissive optics_can this also be an issue for mirrors?

• Wedge/GIMM sits in line-of-sight; is subjected to much higher levels

  • Fast neutron flux at the wedge/GIMM location is 9.5 _ 1012 n/cm2-s
  • Yields wedge/GIMM lifetime of 0.33-33 FPY for 1020-1022 n/cm2 limits

1 C. D. Marshall, J. A. Speth, S. A. Payne, Induced optical absorption in gamma, neutron and ultraviolet irradiated fused quartz and silica, J. of Non-Crystalline Solids 212 (1997) 59-73.

JFL 6/7/2000

Previous slide

Back to first slide

View graphic version