Target chambers for megajoule laser facilities

The authors present a 5-m-radius, 2.5-cm-wall-thickness target chamber designed to withstand buckling, impulse, and pressure loads in a 1-2-MJ laser fusion facility. Although the maximum expected fusion yield is <30 MJ, yields up to ~500 MJ are possible without exceeding allowable stresses. No wall ablation is expected unless the energy in the target chamber exceeds 1.2 MJ; this minimizes damage to optics and diagnostics caused by condensation during low-yield shots. The facility can illuminate indirect drive targets with good uniformity when either all or only a portion of 288 beamlets are operational. Direct drive targets can be illuminated by up to 72 beamlets in a separate target chamber. Sacrificial silica debris shields, with ~10-torr precharge of incondensable gas in the beam tubes, are used for protection of the final optics. The target chamber room has a 1-2-m-thick water neutron shield