The radiation magnetohydrodynamics of a nanosecond capillary discharge

The dynamics and radiation emission of a nanosecond electrical discharge in a gas-filled (Ar or Xe) capillary with hollow cathode is studied. Mechanisms of plasma heating and radiation generation are examined in 2D simulations by means of the radiation-magnetohydrodynamic code ZETA with spectral and EOS properties calculated in non-LTE approximation. Simulations are performed in geometry and with discharge parameters similar to the experimental ones 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 0.3-0.03mbar 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. Multicharged ion plasma is preheated by Joule dissipation and heated by volumetric compression wave induced by magnetic field pressure and cumulation due to the density axial gradient. The heating power exceeds 0.1 MW. It is emitted and absorbed by capillary walls mainly. Radiation through the open capillary end reaches 10kW with effective pulse duration about 17ns. Within the band 10-15nm interesting for applications Xenon emission exceeds 10% of end radiation flux. Theory of axially inhomogeneous capillary discharge magnetohydrodynamics is discussed.