New technique to control electron injection and x-ray generation in plasma based accelerators

A research team from the Institute for Plasmas and Nuclear Fusion (IPFN) from Instituto Superior Técnico (IST), constituted by Jorge Vieira, Samuel Martins, Vishwa Pathak, Ricardo Fonseca, and Luís Silva, in collaboration with researchers from University of California in Los Angeles (UCLA), published a paper on the reputed journal Physical Review Letters, demonstrating through advanced computational simulations a novel technique to precisely adjust some of the key features associated with the accelerated electrons in plasma-based accelerators, thus optimizing the x-ray generation in these ultra-compact devices. This work is a step forward for the use of this technology in several applications related with x-ray radiation emission, with a particular emphasis on the imaging of biological systems, and medical applications.

The propagation of intense light pulses or particle beams in gases may lead to the generation of plasma waves, with typical dimensions of the order of a few micrometers – thinner than a human hair. Similarly to a surfer on a sea wave, plasma electrons can also ride the plasma waves, accelerating to velocities that are very close to the maximum velocity predicted by Einstein’s special theory of relativity, the speed of the light. The extreme forces acting upon the plasma electrons are intense enough to reduce greatly the size of future particle accelerators. The key challenge for the use of this state-of-the-art technology in scientific experiments and related applications is closely linked to the precise manipulation of the accelerated electrons.

IPFN researchers searched for new configurations to control plasma accelerators by using external magnetic fields applied to the plasma regions where the complex acceleration mechanisms are initiated. According to main author Jorge Vieira “our research shows that it is possible to manipulate and to control the acceleration processes in plasmas by resorting to suitably designed external magnetic fields.”

Particle accelerators are critical devices for understanding the fundamental properties of matter, and have played a key role in unravelling the essential mechanisms associated with nuclear energy. They are also commonly present in daily life applications such as a number of medical therapies and x-ray diagnostics. The research and development of novel acceleration techniques is therefore relevant for the scientific and industrial progress. “Our work explores new paths for the use of this technology in several applications, providing an additional control over important features of plasma based accelerators,” says Luís Silva, the research team leader. Resorting to theoretical models and to high performance numerical simulations in some of the world’s largest supercomputers, the research shows that with an appropriately designed external magnetic field it is possible to control precisely key features of plasma-based accelerated electrons, shaping them for x-ray generation.

URL: J. Vieira, S. F. Martins, V. B. Pathak, R. A. Fonseca, W. B. Mori, and L. O. Silva, “Magnetic Control of Particle Injection in Plasma Based Accelerators”, Phys. Rev. Lett. 106, 225001 (2011)