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Proceedings Paper

Improving the intensity of the HELEN Laser at AWE
Author(s): Nicholas Hopps; Jonathan Nolan; Mark Girling; Maria Kopec; Ewan Harvey
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Paper Abstract

The HELEN laser is a three-beam, large aperture Nd:glass laser, used for plasma physics studies at the Atomic Weapons Establishment in the UK. Two of the beams nominally deliver 500 J each in 1 ns at the second harmonic (527 nm). The third beam, the “backlighter”, has recently been upgraded to operate as a chirped pulse amplification system and it now routinely delivers 70 J to target in 500 fs. Optimal focal spot performance is achieved using a closed-loop adaptive optics system, which ensures good wavefront characteristics, irrespective of whether previous firing of the amplifiers has induced refractive index variations in the laser glass. The system uses a 32 element bimorph mirror with 98 mm aperture, roughly half way through the laser chain. A Shack-Hartman wavefront sensor, positioned at the output of the laser is the diagnostic used to provide feedback to the deformable mirror. Correction of the static and slowly varying aberrations on the beam has been demonstrated. The fast aberrations induced during the flashlamp discharge have been evaluated. The improved focal spot characteristics result in an intensity on target of significantly greater than 1019 Wcm-2.

Paper Details

Date Published: 12 April 2005
PDF: 12 pages
Proc. SPIE 5708, Laser Resonators and Beam Control VIII, (12 April 2005); doi: 10.1117/12.609875
Show Author Affiliations
Nicholas Hopps, AWE plc (United Kingdom)
Jonathan Nolan, AWE plc (United Kingdom)
Mark Girling, AWE plc (United Kingdom)
Maria Kopec, AWE plc (United Kingdom)
Ewan Harvey, AWE plc (United Kingdom)

Published in SPIE Proceedings Vol. 5708:
Laser Resonators and Beam Control VIII
Alexis V. Kudryashov; Alan H. Paxton, Editor(s)

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