Intense, High-Quality Ion Beams Generated by Ultra-Intense Lasers

Abstract

The advent of ultra‐intense short‐pulse laser systems has opened the field of relativistic laser‐generated plasmas in which the electron temperature exceeds several MeV. One particularly exciting topic of recent interest has been the discovery of intense, collimated, energetic beams of ions off the back surface of solid targets. The beam currents exceed several hundreds of kiloamperes at a pulse duration of only a few picoseconds. The dominant acceleration mechanism is known as the Target Normal Sheath Acceleration (TNSA) mechanism, which is fundamentally different from the well known ion acceleration processes observed using long pulse laser over the past decades. This mechanism offers the prospect of low‐emittance, laminar, directed ion beams. The laser to ion beam conversion efficiency can be as high as 10 %, which makes these beams interesting to a whole variety of applications. The strong dependence of the ion beam acceleration on the conditions of the target back surface in agreement with theoretical predictions based on the TNSA mechanism was confirmed. Shaping of the ion beam has been demonstrated by the appropriate tailoring of the target and the laser beam. In addition, we demonstrated the use of laser accelerated protons for time resolved proton radiography, which is able provide complementary information about the properties of matter not accessible by current techniques.