Wetted foam capsules for direct drive ICF reactor application

The authors propose a new target approach that provides a passive mechanism for producing highly uniform spherically symmetric cryogenic D-T layers. This target employs a rigid foam matrix to support liquid (or solid) D-T in a spherical shell configuration. Capillary forces generated by the D-T wetting the foam matrix stabilize the liquid against gravitational flow. A schematic of the proposed wetted sponge reactor target is shown. In this design, a spherical sponge shell wetted with liquid D-T serves as ablator, tamper, and fuel layer. To serve as a capsule material, the foam must be open cell, have a high pore volume, and have sufficient mechanical strength. To minimize energy loss due to bremsstrahlung radiation during ignition and burn propagation, the foam in the fuel region should be both low density and low atomic number. One-dimensional LASNEX calculations predict that direct drive capsules composed of D-T-saturated plastic foam can achieve gains of 100 to 200 for incident laser energy at 200 to 700 kJ