Radiative collapse of a dense plasma

Radiative collapse of a dense θ pinch plasma driven by an annular Z-pinch is considered. A cryogenic fiber is coaxially located within the annular gas jet Z-pinch. The imploding Z-pinch traps an applied axial magnetic field and conserves the flux. The axial magnetic field increases due to the compression and has attained values in excess of 20 M-Gauss. If a fiber is placed on axis an azimuthal θ-current is induced with a rise time that is an order of magnitude shorter than the rise time of the Z-pinch current. Such a rise time could not be achieved with a simple Z-pinch because of the large inductance of the axial fiber-plasma. The implosion transfers the kinetic energy of the Z-pinch to the magnetic field and then to the θ-pinch. The terminal particle pressure of the θ-pinch exceeds the magnetic pressure so that the pinch then expands-the only confinement is inertial. It is possible to make an intense neutron source e.g. a yield of 4 × 10¹⁵ neutron/cm with a Z-pinch current of 10 M-Amperes; but break-even would require much larger currents. To reach break-even and beyond with a reasonable Z-pinch current, we propose to make use of radiative collapse. By seeding the cryogenic Hydrogen-like fiber with higher Z-material, the radiation would be substantially increased and the θ-pinch would cool and collapse thereby increasing the density. For example, a density of order 10²⁴ cm⁻³ has been observed with a seeded plasma focus. The confinement time is determined by the temperature and would not decrease. Thus nτ ∼ 10¹⁴ could be reached with a confinement time of 1 nanosec.