Plasma density diagnostic for capillary-discharge based plasma channels

摘要

The plasma density in discharged laser guiding structures, of order 10(18) cm(-3), is critical to laser-plasma accelerators. Here, we demonstrate a technique that uses spectral interferometry to measure the on-axis laser group velocity (and thus density) in cm-scale cylindrical hydrogen-discharge plasma channels by using laser pulses with a Gaussian transverse profile. Experimental density retrieval over a range of capillary parameters (density, length, and diameter) is presented. The accuracy (of order 8 x 10(16) cm(-3)) and shot-to-shot stability (of order 2 x 10(16) cm(-3)) of the diagnostic are discussed. (C) 2015 AIP Publishing LLC.