Taking careful aim with a quadrillion watt laser, researchers at the US Department of Energy’s Lawrence Berkeley National Lab claim to have managed to speed up subatomic particles to the highest energies ever recorded for a compact accelerator. By blasting plasma in their tabletop-size laser-plasma accelerator, the scientists assert that they have produced acceleration energy of around of 4.25 giga-electron volts. Acceleration of this magnitude over the short distances involved correlates to an energy rise 1,000 times greater than that of a traditional – and very much larger – particle accelerator.
The Large Hadron Collider (LHC) at CERN, for example, is some 17 miles (27 km) in circumference, and accelerates particles by way of a series of sequential, modulated electromagnetic fields contained in a metal cavity. This is perfectly fine for anything up to about 100 mega-electron volts per meter before things go awry and the metal cavity starts to break apart.
By comparison, the tiny Berkeley Lab accelerator achieves its world record by accelerating electrons inside a plasma tube just 9 cm (3.5 in) long up to a speed that would normally take an average particle accelerator many, many miles to achieve (if at all), and in a unit that sits comfortably on the top of a laboratory table.
To be fair to traditional particle accelerators, laser-plasma accelerators take a completely different approach to exciting particles to such enormous energy levels. In this case, the experiment was realized with the assistance of one of the most powerful lasers in the world, the Berkeley Lab Laser Accelerator (BELLA). This laser system produces a beam of light equivalent to a quadrillion watts of power (a petawatt), which the Berkeley researchers used to focus on the very small, straw-like tube that contained the plasma of their particle accelerator. Though, in this initial experiment, it was limited to pulses of a "mere" 0.3 PW or 300,000 gigawatts.
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