CAREER: Bright Femtosecond x- and Gamma-Ray Pulse Production Using Ultra-Intense Lasers

Regents Of The University Of Michigan - Ann Arbor, Ann Arbor MI

Investigators

Abstract

The research objective of this project is to measure and model the properties of radiation, and the complex electron dynamics, resulting from the electromagnetic interaction of electron beams generated in high-intensity laser-plasma interactions. Conventional accelerator facilities must be large because the accelerating fields are limited by electrical breakdown of the material when the potential difference reaches some threshold. Energy gain is force times distance, so if the field strength (and therefore force) is limited then the distance must be increased to achieve higher and higher particle energies. This has lead to many mile scale facilities being constructed. However, if we use completely ionized gas -- plasma -- it turns out that an accelerating structure can be generated that is not limited in field strength. In other words; an accelerator can be miniaturized. The astonishing field strength in a plasma based accelerator can typically be equivalent to a 2 mile conventional accelerator being reduced to half a meter in length. Plasma accelerators can be created using high intensity lasers, which generate an evacuated ionic cavity, or 'bubble' with strong accelerating electric fields. It turns out that this plasma 'bubble' also has ideal characteristics for providing a miniature wiggler structure; an alternative to an external magnetic structure (such as the 1 mile length LCLS extension to SLAC) for generating radiation. The plasma can therefore be both an accelerator and wiggler combined. Alternatively, a second laser beam can also be used to wiggle the electrons. In both caes, a Doppler-like effect means that the radiation emitted by the relativistic electron beam is upshifted to much higher frequencies than those of the oscillating structure. The combination of lasers and plasmas can therefore provide very intense, energetic sources of x and gamma rays. The drive for radiation sources is prompted by the numerous applications, from aiding the development of the anti-flu drug Relenza or a vaccine for foot and mouth disease to imaging residual stresses in aircraft wings or determining whether Beethoven was poisoned by analysis of a sample of his hair. This has motivated the development of large x-ray light sources around the world. The research proposed here is of a fundamental nature but also with an exciting applicability and potential technological impact. There are a vast number of unanswered questions on the laser propagation, plasma behavior, and radiation generation to be explored. However, one of the most exciting things associated with the research is the potential for miniature and inexpensive synchrotron light sources that could be available more widely; accessible to universities, small research facilities or hospitals. This could revolutionize a vast swath of scientific and engineering disciplines, as researchers from biotechnology to mechanical engineering are currently waiting for time on existing synchrotron light sources. Increased access to brilliant x-ray light sources could therefore increase the progress of technologic development in many fields.