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Proceedings Paper

Investigations of sacrificial and plasma mirrors on the HELEN laser CPA beam
Author(s): James E. Andrew; Andrew J. Comley
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Paper Abstract

The performance of sacrificial and plasma mirrors has been investigated on the HELEN laser chirped pulse amplification [CPA] beam line. Sacrificial mirrors are initially highly reflective surfaces that degrade during the course of a pulsed laser experiment. They are being considered for protecting the off axis parabolic surfaces used to focus CPA lasers from plasma physics target generated debris and shrapnel. Plasma mirrors are initially low reflectivity surfaces that transmit low intensity beams but produce a reflecting plasma surface during the course of the laser pulse. They are being investigated to prevent prepulse effects in plasma physics experiments and increase the contrast ratio of the incident laser beam.The sacrificial mirrors were operated at 45 degrees angle of incidence and an average input beam diameter of ~14 mm with intensities in the range 8 TW/cm2 to 44 TW/cm2. Dielectric protected silver and gold coatings as well as dielectric multi layers were studied as the mirror surfaces for directing all of the short pulse [500fs] laser beams onto tantalum foil targets of 10 microns thickness. Proton emissions from the foils monitored by radiochromic film were used to evaluate the beam irradiance achieved from the mirror surfaces. Glass witness plates were used to evaluate debris and shrapnel emissions from the mirror surfaces, the diagnostics and the target foils. The plasma mirrors were operated in a similar configuration but with beam diameters of ~8mm and irradiances of 57 TW/cm2 to 235 TW/cm2. Uncoated and sol gel anti-reflection coated fused silica were used as the high intensity mirror surfaces. The influence of surface coating on laser damage morphology will be described as well as post shot inspection of debris distributions.

Paper Details

Date Published: 15 January 2007
PDF: 13 pages
Proc. SPIE 6403, Laser-Induced Damage in Optical Materials: 2006, 64030P (15 January 2007); doi: 10.1117/12.695559
Show Author Affiliations
James E. Andrew, AWE plc (United Kingdom)
Andrew J. Comley, AWE plc (United Kingdom)

Published in SPIE Proceedings Vol. 6403:
Laser-Induced Damage in Optical Materials: 2006
Gregory J. Exarhos; Arthur H. Guenther; Keith L. Lewis; Detlev Ristau; M. J. Soileau; Christopher J. Stolz, Editor(s)

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