Beam and hot-spot formation in a low impedance line driven vacuum spark discharge

Observations of a vacuum spark discharge are presented using a coaxial line driver. A 120 ns, 1.5 Ω coaxial line is used to give peak discharges of 90 kA. The usual line spark gap is shorted out giving a new mode of operation. The discharge is initiated once the rising sinusoidal voltage is applied by focusing a Nd:YAG laser onto the cathode front surface, peak current is reached at 250 ns after this. Reproducible hot spot formation is observed at this time. Holographic interferometry combined with time and space resolved x-ray observations show emission from a dense anode plasma as well as from the dense plasma column in which hot spot forms at peak current.