Capillary optical guiding experiments for the NRL laser wakefield accelerator

Extended propagation of terawatt (TW) laser pulses has been shown in plasma channels formed with a capillary discharge. Capillary optical guiding experiments at NRL utilize plasma channels formed using both laser ablation and electrical discharge. Present experiments aim to develop laser preionization and ablation from capillary walls as a formation technique for the guiding plasma. Electron density measurements of laser-formed plasmas within the capillary yield values as low as 10/sup 18/ cm/sup -3/. These densities hold promise for optimization of plasma conditions for standard laser wakefield acceleration (LWFA). Experiments also aim to characterize plasma ablation dynamics and plasma channel conditions within the capillary using a variety of imaging and other diagnostics. Imaging diagnostics include axial shadowgraphy. Capillary guiding diagnostics such as transmission efficiency, output beam mode imaging, time resolved backward-scattered Raman spectra, forward Raman spectra, and Thomson scattering imaging are also employed.