Prof Peter Norreys FInstP;

Abstract:

Protons accelerated by a picosecond laser pulse have been used to radiograph a 500μm diameter capsule, imploded with 300 J of laser light in 6 symmetrically incident beams of wavelength 1.054μm and pulse length 1 ns. Point projection proton backlighting was used to characterize the density gradients at discrete times through the implosion. Asymmetries were diagnosed both during the early and stagnation stages of the implosion. Comparison with analytic scattering theory and simple Monte Carlo simulations were consistent with a 3±1g/cm3 core with diameter 85±10μm. Scaling simulations show that protons >50MeV are required to diagnose asymmetry in ignition scale conditions. © 2006 The American Physical Society.

Abstract:

With the addition of recent PW shots, the propagation of short-pulse laser generated electron beams have been studied using laser pulse energies from 30 J to 300 J, generating currents up to ∼15 MA in solid Al:Cu targets. This is ∼5% of the current that will be required in an ignition pulse. To this level, the current appears to simply scale with laser power, the propagation spread not change at all. The resistance of the aluminum does not seem to play a role in the propagation characteristics, though it might in setting the current starting parameters. We do find that at the highest currents parts of these targets reach temperatures high enough to modify the Cu-K2 emission spectrum rendering our Bragg imaging mirrors ineffective; spectrometers will be needed to collect data at these higher temperatures. © EDP Sciences.