Isolated proton bunch acceleration by a petawatt laser pulse

Abstract

Often, the interpretation of experiments concerning the manipulation of the energy distribution of laser-accelerated ion bunches is complicated by the multitude of competing dynamic processes simultaneously contributing to recorded ion signals. Here we demonstrate experimentally the acceleration of a clean proton bunch. This was achieved with a microscopic and three-dimensionally confined near critical density plasma, which evolves from a 1 µm diameter plastic sphere, which is levitated and positioned with micrometer precision in the focus of a Petawatt laser pulse. The emitted proton bunch is reproducibly observed with central energies between 20 and 40 MeV and narrow energy spread (down to 25%) showing almost no low-energetic background. Together with three-dimensional particle-in-cell simulations we track the complete acceleration process, evidencing the transition from organized acceleration to Coulomb repulsion. This reveals limitations of current high power lasers and viable paths to optimize laser-driven ion sources.

Parametric study of a high amplitude electromagnetic pulse driven by an intense laser

“…These characteristics limit its potential applications. Numerous experiments with engineered targets have been performed to optimize and control the properties of the ion sources [9][10][11][12][13].…”

Spectral and spatial shaping of laser-driven proton beams using a pulsed high-field magnet beamline

“…In parallel to ongoing development and improvement of the high power laser sources on the petawatt (PW) level [20][21][22] , continuous efforts in the field have been undertaken to study and optimise the laser-matter interaction. Advanced acceleration schemes 23 and sophisticated targetry [24][25][26][27][28] are recognised as possible routes to improving key features of the laser accelerated proton beams, such as narrowed spectra or enhanced intensity and energy. However, target normal sheath acceleration (TNSA) from thin solid-density foils remains today the best established and most stable acceleration mechanism.…”

Nm-sized cryogenic hydrogen clusters for a laser-driven proton source

“…The second problem, the energy loss by the escaping electrons, could be overcome by the so-called mass-limited targets. In this case, however, the target with the very fine support structure or the fully levitated target 22 has to be replaced after every laser shot.…”