The ability to select and stabilize a single filament during propagation of an ultrashort high-intensity laser pulse in air makes it possible to examine the longitudinal structure of the plasma channel left in its wake. We present detailed measurements of plasma density variations along laser propagation. Over the length of the filament, electron density variations of 3 orders of magnitude are measured. They display evidence of a meter-long postionization range, along which a self-guided structure is observed coupled with a low plasma density, corresponding to approximately 3 orders of magnitude decrease from the peak density level.

Generation of low jitter capillary discharge channels triggered by a relatively low-energy laser pulse is reported. For ablative discharges in polyethylene and boron nitride capillaries, the dependences of the breakdown delay and jitter on the incident laser intensity and discharge voltage are presented. Low jitter (5 ns and less) and the absence of electric noise associated with the discharge ignition make this method very useful for applications such as channel-guided laser-wakefield accelerators and x-ray lasers, where precise synchronization of the discharge with a laser and/or electron beam entering the channel is required.

The evolution of longitudinal electron density and temperature profiles in plasma channel produced by a low-current Plexiglas capillary discharge with laser ignition was investigated by spectroscopic methods. The plasma was produced by an electric discharge using a 0.5mm diameter, 15mm long Plexiglas capillary. The electron density measured in near-outlet region was found to be lower by 30%. Simulations show that this variation of the plasma density near the entrance of the capillary can pose substantial difficulties for external injection of electrons for laser wakefield accelerator applications.

Guided propagation of ultrashort (100fs) high intensity (1016Wcm−2) laser pulses over distances up to 12.6cm using optimized segmented capillary is reported. A new diagnostic technique is presented in which the transport of a guided laser pulse at different delay times from the initiation of the discharge is sampled on a single discharge shot. The current waveform was optimized to obtain a long lasting, deep radial profile. Radial profiles with the maximal electron density from 4×1017 to 2×1018cm−3 and up to 25% deep were obtained thereby, whereas longitudinal profiles were found to be remarkably uniform. The potential application of these long channels to the laser wake field accelerator is discussed.

Articles you may be interested inHigh-current long-duration uniform electron beam generation in a diode with multicapillary carbon-epoxy cathode Note: Characterization of the plasma parameters of a capillary discharge-produced plasma channel waveguide to guide an intense laser pulse Rev. Sci. Instrum. 81, 046109 (2010); 10.1063/1.3397321 Longitudinal profiles of plasma parameters in a laser-ignited capillary discharge and implications for laser wakefield accelerator applications Appl. Phys. Lett. 87, 261501 (2005); 10.1063/1.2149183 Three-dimensional laser-induced fluorescence measurements in a helicon plasma Rev. Sci. Instrum. 75, 4103 (2004);Generation of axisymmetric stable, long plasma channels with temperatures of 8 eV and electron densities ϳ10 19 cm Ϫ3 by a high-current evaporating-wall capillary discharge with prepulse ablative plasma is reported. Results of spectroscopic measurements of the temperature and electron density of plasma produced in a polyethylene capillary are presented. The discharge provides a convenient source of dense highly ionized plasmas for laser-plasma interaction studies.