An international team of physicists at Los Alamos National Laboratory has
succeeded in using intense laser light to accelerate protons to energies never
before achieved. Using this technique, scientists can now accelerate particles
to extremely high velocities that would otherwise only be possible using large
accelerator facilities. Physicists around the world are examining laser particle
acceleration and laser produced radiation for potential future uses in cancer
treatment.
 | | This is an image of the infrared laser (not seen, entering from left-hand side) interacting with a flat target (center), and the associated plasma production from the interaction on the various diagnostic instruments in the chamber. This is a time integrated image over five seconds. Credit: Joe Cowan and Kirk Flippo, LANL |
Experiments by Sandrine Gaillard, performed as part of her doctoral thesis
which is supervised by Prof. Cowan, director of the Institute of Radiation Physics
at the Forschungszentrum Dresden-Rossendorf (FZD), achieved world-record energies
for laser accelerated particles. These record results were obtained in partnership
with scientists at FZD, Sandia National Laboratories, the University of Nevada,
Reno, and the University of Missouri, Columbia, all working at the Trident Laser
Facility at the Los Alamos National Laboratory in New Mexico. Protons were accelerated
to velocities of 254 million miles per hour (or 37% of the speed of light).
The new record was achieved using specially shaped targets at Trident, the
world's highest contrast high-intensity, high-energy laser. The scientists shot
high-contrast ultrashort laser pulses lasting approximately 600 femtoseconds
(600 quadrillionths of a second) and around 80 Joules directly into the cone-shaped
structures, whose flat-top tips are covered with a thin film. The surfaces were
created using nanotechnology, and produced by the company Nanolabz.
When the intense laser light collides with the inside of these anvil-like microstructures,
electrons are liberated from the material. In contrast to flat-foils, the microstructures
act as an electron guide to the tip. The electric field generated can then be
used to accelerate the protons to energies that were previously unachievable.
X-ray imaging (see Fig. 2) was used as a diagnostic tool to help illustrate
and clarify the laser-cone interaction. The precise interactions, however, must
still be resolved by the scientists via computer simulations. Next, they will
study the cones ability to efficiently convert laser light into high energy
protons.
The record measurements will be presented at the annual APS
Division of Plasma Physics meeting in November 2009 in Atlanta, GA.
Posted November 2nd, 2009
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