X-ray laser cavity based on multiple pulse laser excitation of capillary discharge

Abstract

An ambient plasma with a low temperature (<10 eV) and high density (>10/sup 19/ cm/sup -3/) is formed from a rectangular slot in a capillary discharge. This plasma, moving at approximately 2*10/sup 6/ cm/s, exits out of a 1-cm-long, 200- mu m-wide slit. A high-energy Q-switched laser in a cylindrical focusing geometry irradiates the ambient plasma, creating a rectangular parallelepiped of laser-heated plasma. The geometry, initial conditions, and versatility of this source are suited to the generation of amplified soft X-ray lasing along the 1-cm length. The capillary-discharge-produced ambient plasma lasts on the order of 8 mu s, during which an ambient plasma is being produced and will replace the heated plasma approximately every 10 ns. Thus, one can create in a single event, i.e. capillary discharge and laser-pulse chain, numerous heated plasma pulses. In the current work, a mode-locked laser was used to produce a train of many pulses at the oscillator. Instead of switching out a single pulse, three pulses were switched out from the laser oscillator and delivered to a chain of amplifiers. This chain of laser pulses, spaced at intervals >10 ns, is focused onto the ambient plasma. This method can be used to construct an X-ray laser cavity.<>