The radiation magnetohydrodynamics of a nanosecond capillary discharge

The radiation of a nanosecond Xenon gas-filled capillary discharge is examined in 2D simulations by means of the radiation-magnetohydrodynamic code ZETA and compared with experimental data. The capillary discharge with hollow cathode is initiated by capacitor 0.8 nF charged to 17 kV. A discharge current with 4.8 kA amplitude, 16 ns period damped oscillations is produced. A gas pressure gradient 0.3-0.03 mbar from the anode to the cathode was initially organized in order to provide an effective electron beam pre-ionization wave in the hollow cathode discharge as well as to organize a blow-through of the capillary in high repetition rate operation. Due to small capillary radius a discharge current diffuses through and plasma compression has a volumetric character. In the case of initial gas density distribution with an axial gradient, the volumetric compression produces additional cumulative wave from lower to higher density. A theory of such three dimensional compression is developed and compared with simulations. This effect permits to increase the emission efficiency. Xenon plasma is preheated by Joule dissipation and heated by volumetric magnetic compression wave. The heating power exceeds 0.1 MW. It is emitted and absorbed by capillary walls mainly. Radiation through the open capillary end reaches 10 kW with effective pulse duration about 17 ns. Within the band 10-15 nm Xe radiation exceeds 10% of end radiation flux.