Relativistic Tennis with Photons

Whoa! If this thing really works, all those multi-million dollar x-ray FEL facility such as the LCLS being constructed at SLAC might be obsolete!

Reported in today's Science daily news (link open only for a limited time), a team from Advanced Photon Research Center at the Japan Atomic Energy Agency has shown the ability to generate an ultrashort and ultraintense x-ray pulse using just ordinary laser.

However, Sergei Bulanov of the Advanced Photon Research Center at the Japan Atomic Energy Agency in Kyoto and colleagues say they have a prototype that can generate pulses of x-ray laser light on the cheap. The researchers call their technique "relativistic tennis with photons," but a more violent analogy may better convey how it works. Suppose you throw a golf ball at a locomotive that is speeding toward you. The golf ball will bounce off it and come flying back at you with tremendous energy--just before you get run over.

The golf ball is a pulse of ordinary low-energy photons. With a tabletop setup, Bulanov and colleagues create the equivalent of a locomotive by firing a different laser into a cloud of plasma, where it creates a wake that travels at near-light speed. When the photons hit the wake, their energy increases 56-fold. They are also focused into an ultrashort, ultraintense blast by the wake, which is shaped like a miniature radar dish.

They have recently uploaded two preprints on ArXiv that you may want to check out:

1. Relativistic Tennis with Photons: Demonstration of Frequency Upshifting by a Relativistic Flying Mirror through Two Colliding Laser Pulses


2. Generation and Observation of Coherent, Long--Lived Structures in a Laser--Plasma Channel

Zz.