New record for particle accelerator
A particle accelerator based on laser-driven plasma waves supplies charged particles with energy of one billion electron volts over a distance of just 3.3 centimetres. This makes it the first of its kind to come close to the energies used in conventional systems.
In order to bring the electrons to such high speeds, the researchers led by Wim Leemans from the Lawrence Berkeley National Laboratory, in cooperation with the University of Oxford, generated the plasma in fine tubes inside a sapphire, in contrast to previous experiments. There it condensed at the edges, creating a plasma tunnel that acts like an optical fiber. As a result, the laser pulse, which travels through the plasma and generates the decisive plasma waves, is continuously focused in the center of the tube. In this way, it is possible for the free electrons to ride the plasma wave for longer, like a surfer, and thus gain energy.
In contrast to the new method, the Slac linear accelerator used at Stanford generates fifty times the energy, but requires a distance that is around 100,000 times longer. The particles are accelerated using an electric field generated by high-energy microwave radiation.
As early as autumn 2004, the scientists were able to use similar techniques to accelerate highly focused bunches of electrons to an energy of up to 200 million electron volts. At that time, however, the required laser intensity could only be maintained over a few millimeters.
The new technology allows the construction of compact, high-energy experiments that can be used, for example, to explore the subatomic world. Other applications can be found in materials science and medicine.