Shielding Analysis for X-Ray Sources Generated in Target Chamber of the National Ignition Facility

Prompt doses from X-rays generated as result of laser beam interaction with target material are calculated at different locations inside the National Ignition Facility. The maximum dose outside a target chamber diagnostic port is [approximately]10 mSv for a shot utilizing the 192 laser beams and 1.8 MJ of laser energy. The dose during a single bundle shot (eight laser beams) drops to [approximately]0.4 mSv. Doses calculated outside the target bay (TB) doors and inside the switchyards (SYs) [except for the 5.33-m (17-ft 6-in.) floor level] range from a few microsieverts to [approximately]110 Sv for 192 beams and scale down proportionally with a smaller number of beams. At the 5.33-m (17-ft 6-in.) floor level, two diagnostic ports are directly facing two of the TB doors, and the maximum doses outside the doors are 0.5 and 0.16 mSv, respectively. Shielding each of the two TB doors with 6.35-mm-thick Pb (¼-in.) reduces the dose by a factor of 50. One or two bundle shots (8 to 16 laser beams) present a small hazard to personnel in the SYs.