Ion acceleration by laser induced surface waves
As part of an ongoing research project, the goal of this proposal is to investigate the possibility of using a method based on laser induced surface waves for ion acceleration. Laser-based plasma-driven acceleration of particles is a technique which can achieve high energy particle beams on a much shorter length scale than conventional accelerators. There are a manifold of possible applications to such accelerators and this is a very active area of research. Specifically, acceleration of heavier particles or ions is of interest due to the many possible applications e.g. for hadron therapy and diagnostics. The most common laser-based ion acceleration technique used today, TNSA, is based on shooting a laser on a thin metallic film to heat up the electrons which are then expelled. The electrons will then drag the ions along, creating a beam of ions. For many applications ions of high energy and low transverse emittance is desired. However, with this technique it has turned out to be difficult to control the properties of the beam to a sufficient degree to achieve this. In this project we would like to investigate the possibility of using a method for acceleration based on surface waves. These waves have some promising properties which can potentially be utilised to simultaneously achieve high energy and well focused beams. A high intensity laser pulse which interacts with a metallic film can quickly accelerate the electrons within the metal to velocities close to the speed of light. However, ions need more time to reach high velocities due to their higher masses. This calls for finding acceleration schemes where the interaction time between the laser pulse and the particles is increased. Surface waves, which are perturbations localised to the surface of a solid, presents a way to achieve this, since by varying the parameters involved (wavelength of the laser, density of the metal, etc) the velocity of the waves can be controlled. Furthermore, since the waves are well localised to the surface, it is possible to consider geometries where the beam is naturally collimated. Particles tend to move away from regions where the field is strongest. By considering e.g. a cylindrical hole with the wave traveling on the inner surface, the particles will be pushed in towards the center where the field is weaker and hence creating a more narrow beam. In this project the computational resources will be used to: - Investigate properties of high-intensity laser induced surface waves in general. - Consider different ways of exciting the wave modes using lasers and different geometries. - Determine how the pulse velocity can be controlled by varying the geometry and the parameters involved and how this can be used to affect acceleration. The Knut and Alice Wallenberg foundation awarded 38.5MSEK for a 5-year project (1 July 2014 -- 30 Jun 2019) on the above topic (the PLIONA project). Short popular science film on the project can be seen on the webpage of the Wallenberg foundation.