Abstract
Abstract There are several petawatt-scale laser facilities around the world and the fidelity of the pulses to target is critical in achieving the highest focused intensities and the highest possible contrast. The United Kingdom has three such laser facilities which are currently open for access to the academic community: Orion at AWE, Aldermaston and Vulcan & Astra-Gemini at the Central Laser Facility (CLF), STFC (Science and Technology Facilities Council) Rutherford Appleton Laboratory (RAL). These facilities represent the two main classes of petawatt facilities: the mixed OPCPA/Nd:glass high-energy systems of Orion and Vulcan and the ultra-short-pulse Ti:Sapphire system of Astra-Gemini. Many of the techniques used to enhance and control the pulse generation and delivery to target have been pioneered on these facilities. In this paper, we present the system designs which make this possible and discuss the contrast enhancement schemes that have been implemented.
Highlights
The facilities highlighted within this paper are operated at AWE, Aldermaston, UK and the Central Laser Facility (CLF), STFC (Science and Technology Facilities Council) Rutherford Appleton Laboratory (RAL), UK and have the following system parameters:
Contrast measurements[33] were made with several optical configurations of the pulse stretcher, in which different components were eliminated or replaced, allowing us to distinguish the contribution to the coherent pedestal from different optics
In an experiment at the CLF[38] the specular reflectivity of plasma mirrors formed by sub-picosecond pulses from a Ti:Sapphire laser was measured for different angles of incidence and for two different pulse lengths as a function of the laser intensity
Summary
The facilities highlighted within this paper are operated at AWE, Aldermaston, UK and the Central Laser Facility (CLF), STFC (Science and Technology Facilities Council) Rutherford Appleton Laboratory (RAL), UK and have the following system parameters:. Orion is the latest facility to be built in the UK and became operational in April 2013[1] It is a Nd:glass laser system which combines 10 long-pulse beamlines (500 J, 1 ns @ 351 nm) with two synchronized infrared petawatt beams (500 J in 500 fs). It is operated as an academic user facility It has two ultra-high-power beamlines delivering 15 J in 30 fs pulses @800 nm, generating focused intensities >1021 W cm−2 to target. Having generated the petawatt beam, the use of adaptive optics holds the key to achieving the spot size and pulse duration required for irradiances on target >1020 W cm−2. The optical images, taken in the output beam diagnostics prior to the compressors and shown in Figures 6(a) and 6(b), show the quantitative improvement in focusability in moving from the use of the flat mirror to the deformable mirror. The streaked optical transition radiation (OTR) emission gives a central image size of ∼8 μm FWHM (shown in Figure 6(d)) on a 100 TW shot, which gives an irradiance on target of 2 × 1020 W cm−2
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