Hohlraum
First proposed by Gustav Kirchhoff in 1860 and used in the study of black-body radiation (hohlraumstrahlung),[1] this idealized cavity can be approximated in practice by a hollow container of any opaque material.The outer portion of the fuel capsule explodes outward when ablated by the x-rays produced by the hohlraum wall upon irradiation by lasers.The advantage to this approach, compared to direct drive, is that high mode structures from the laser spot are smoothed out when the energy is re-radiated from the hohlraum walls.Hence imperfection is to be carefully prevented so surface finishing is extremely important, as during ICF laser shots, due to intense pressure and temperature, results are highly susceptible to hohlraum texture roughness.By the end of the 1990s, target physicists developed a new family of designs in which the ion beams are absorbed in the hohlraum walls, so that X-rays are radiated from a large fraction of the solid angle surrounding the capsule.
HoluhraunradiationthermodynamicsGermanradiative equilibriumradiant energyGustav Kirchhoffblack-body radiationopaqueKirchhoff’s lawNational Ignition Facilityinertial confinement fusionfusioncylindricalX-raysimplosionhydrodynamic instabilitiessolid anglethermonuclear bombTeller-Ulam designfissionHarrison, Edward R.Bibcode