The High-Repetition-Rate Advanced Petawatt Laser System (HAPLS) under construction in the Czech Republic is designed to generate a peak power of more than 1 quadrillion watts (1 petawatt, 1015 watts). The key component to this instrument – the laser "pump" – will be a set of solid-state laser diode arrays recently constructed by Lawrence Livermore National Laboratory (LLNL). At peak power, this electronic assemblage develops a staggering 3.2 million watts of power and are the most powerful laser diode arrays ever built.

The pump in a high-energy laser system is the element or set of elements that use high-powered light to excite (or "pump") atoms in the lasing medium – for example, a ruby rod or a gas-filled glass tube (in the HAPLS system, it is titanium-doped sapphire) – to produce laser light. In earlier high energy laser systems, this was usually achieved with flashlamps of quartz or xenon to generate the super-intense flashes of light required.

Unfortunately these types of laser pumps suffer from both very large amounts of heat being generated as they flash – up to 900° C (1,650° F) in quartz flashlamps, for example – and flash rates too slow to be useful in newly-developed fields of research. In the HAPLS, however, the diode arrays acting as a pump are much cooler by comparison and are also able to fire at a rate of up to 10 times per second (10 Hertz).

"Flashlamp technology for lasers has been around for more than 50 years, and we’ve pretty much pushed the limits of that technology and maxed out what we can do with them," said Andy Bayramian, systems architect on HAPLS. "We’ve closed the books on flashlamps and started a new one with these laser diode arrays, enabling a far more advanced class of high-energy laser systems."

As a result of the new LLNL diode array’s ability to shoot multi-kilojoule laser pulses into the final power amplifier of the HAPLS, the system will not only be able to generate peak powers greater than one quadrillion watts, but at a repetition rate of 10 Hertz and 30 femtoseconds (30 quadrillionths of a second) duration per pulse.

Such powers and speeds the team believes will motivate a range of areas of research in fields as assorted as particle acceleration physics, biophysics, chemistry, advanced imaging, and quantum physics. The team asserts that such technology may also be key to new advances in industrial processes like laser peening and laser fusion.

The HAPLS is also a relatively compact system compared to other petawatt-capable laser systems, such as Lawrence Berkeley National Lab’s BELLA system, which occupies a space of around 100 sq m (1,076 sq ft). In comparison, HAPLS will only take up 78 sq m (840 sq ft) of space when it is finally installed in the European Union’s Extreme Light Infrastructure (ELI) Beamlines facility, currently being built in the Czech Republic.

"The Extreme Light Infrastructure in Europe is building international scientific user facilities equipped with cutting-edge laser technology to explore fundamental science and applications," said HAPLS Program Director Constantin Haefner. "Livermore (LLNL) is one of the world leaders in high-energy, high-average-power laser systems, and ELI Beamlines in Prague has partnered with us to build HAPLS, a new-generation petawatt laser system, enabling new avenues of scientific research."

As well as producing extraordinary levels of laser power, the LLNL diode laser arrays likewise consume an inordinate amount of power. To supply this energy, LLNL has also developed and patented a new pulsed power supply system that converts grid-sourced electricity into exceptionally high-current, accurately shaped electrical pulses, whose individual power supplies are able to output an enormous 40,000 amps of electrical current.

The HAPLS is being constructed and commissioned at LLNL and is then slated for installation in the ELI Beamlines facility sometime in 2017.

Source: Lawrence Livermore National Laboratory

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