AWE maintains a high-power laser, HELEN, as a service to the Plasma Physics community, so that they have a facility on which to perform their research. Currently, Orion, which will be the successor to HELEN, is under construction at AWE.
HELEN
Currently the centrepiece of these laser facilities is HELEN (which stands for High Energy Laser Embodying Neodymium); a large-aperture, multi-pass, Nd:glass laser.
HELEN, which has been operational since the late 1970s, was a world-first for this type of experimental facility and over the years it has evolved considerably.
It consists of three beams, two of which can deliver up to 500J in 1 ns square pulse, at a wavelength of 527nm (2w) and a third arm, which is used to backlight experiments. This can operate at either 1053 or 527nm (the first or second harmonic) and either as a conventional, long-pulse beam-line or, more usually, as a 100TW, CPA (~1ps) beam-line.
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Orion – The Future
Orion is an exciting, ambitious project to construct a world-leading laser facility for the creation and study of hot, dense matter. It will eventually replace AWE’s existing HELEN laser facility, giving our scientists access to extreme states of matter which exist nowhere else on Earth. Construction of the new Orion laser research facility is well underway, with full commissioning of the state-of-the-art laser expected by 2010.
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Orion will have 10 'long-pulse' (ns) beam-lines, each producing 500J at 351nm (3w) and two powerful chirped-pulse amplification (CPA) arms, producing ~500J in ~0.5ps (1w).
It will be maintained under 'operating theatre' conditions, housed in a huge clean-room within a specially designed building which will isolate it from the effects of vibration and contamination.
Orion will be approximately 100 metres long, 60 metres wide, and 25 metres high. High-tech laser components and systems at the very edge of current technological limits, including CPA, adaptive optics (AO) and metre-diameter gold-coated diffraction gratings, will be incorporated in the laser.
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Orion will support AWE’s science mission of maintaining confidence in the safety and operability of the stockpile in the present era, which follows the ratification of the Comprehensive Test Ban Treaty (CTBT).
It will be capable of creating conditions in the laboratory which replicate those which occur in an operating nuclear warhead. This will enable materials properties to be measured in a regime of high applicability to the weapon. It will also help to bridge between interpretative and predictive computer codes by providing experimental data for benchmarking.
Another key aspect of Orion's mission will be the provision of beam-time to the academic community. There is a significant overlap between the physical processes that occur in an exploding warhead and objects of more general scientific interest such as evolving stars, super-dense matter and high-temperature systems. Orion is designed to be configured to support an even wider field of scientific exploration including particle acceleration, X-ray laser research and the production of short-lived isotopes.
Access to laser facilities at the leading edge of world capability plays an important part in helping universities to attract the highest calibre researchers and young scientists to the subject of Plasma Physics. It is from this pool of expertise that many future AWE scientists will be recruited and the vitality of the subject is very important to the sustainability of AWE's technical programmes.