Tabletop particle accelerators possible with new laser-plasma approach

Laser light needn't be as precise as previously thought to drive new breed of miniature particle accelerators, say Berkeley Lab researchers.

Researchers hope the finding could bring about a new era of accelerators that would need just a few metres to bring particles to great speeds, rather than the many kilometres required of traditional accelerators. The research, from scientists at the US Department of Energy's (DOE) Lawrence Berkeley National Laboratory, is presented n the May issue of Physics of Plasmas.

Traditional accelerators, like the Large Hadron Collider, rely on high-power radio-frequency waves to energise electrons. The new type of accelerator, known as a laser-plasma accelerator, uses pulses of laser light that blast through a soup of charged particles known as a plasma; the resulting plasma motion accelerates electrons to high speeds.

The problem, however, is creating a laser pulse that's powerful enough to compete with the big accelerators. In particular, lasers need to have the capability to fire a high-energy pulse thousands of times a second. Today's lasers can only manage one pulse per second at the energy levels required.

It was believed that the light from lasers would need to be matched in wavelength, phase, and other properties in order to produce the electron-accelerating motion within the plasma. However, paper co-authors Carlo Benedetti, Carl Schroeder, Eric Esarey and Wim Leemans investigated using an erratic laser pulse and found that the plasma responded. 

‘As an experimentalist for all these years we're trying to make these perfect laser pulses, and maybe we didn't need to worry so much,’ said Leemans. ‘I think this will have a big impact on the laser community and laser builders because, all of a sudden, they'll think of approaches where beforehand all of us said, “No, no, no. You can't do that.” This new result says, well maybe you don't have to be all that careful.’

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