Space- and Time-Resolved Dynamics of Fast Electrons and of the Energy Partition Into Cold Electrons

• Published in: IEEE transactions on plasma science 2008-08, Vol.36 (4), p.1821-1824
• Main Authors: Antici, P., Fuchs, J., Grismayer, T., Borghesi, M., Brambrink, E., Cecchetti, C.A., Lancia, L., Mancic, A., Mora, P., Pipahl, A.C., Toncian, T., Willi, O., Audebert, P.
• Format: Article
• Language: English
• Subjects: Adiabatic flow; Charged-particle beams; Clouds; Communication, education, history, and philosophy; Density; Dynamics; Electromagnetism; electron and ion optics; Electrons; Energy use; Exact sciences and technology; Experiments; Fundamental areas of phenomenology (including applications); Hot/cold-electron temperature and density; Instruments, apparatus, components and techniques common to several branches of physics and astronomy; Interferometers; Interferometry; laser-accelerated particles; Laser-driven acceleration; Laser-plasma acceleration of electrons and ions; Laser-plasma interactions; Lasers; Measuring instruments; Micrometers; Optical instruments, equipment and techniques; Physics; Physics literature and publications; Physics of gases, plasmas and electric discharges; Physics of plasmas and electric discharges; Plasma; Plasma measurements; Plasma simulation; Plasma temperature; Probes; Simulation; Solid lasers; Spatial resolution; Surface emitting lasers; time- and space-resolved interferometry (TASRI); Wavelength measurement
• ISSN: 0093-3813; 1939-9375
• DOI: 10.1109/TPS.2008.2001230

Through the time- and space-resolved interferometry of a short-pulse low-energy probe beam reflecting on the rear surface of a solid target irradiated on its front surface by a high-intensity laser, we have measured a very abrupt expansion of the target rear surface. The experiments were performed using the LULI 100-TW laser facility with a maximum of 10-20 J energy pulses of > 10 19 W ldr cm -2 intensity, wavelength of 1.053 mum irradiating Al targets. The detected phase changes, with a few micrometers spatial resolution and picosecond temporal resolution, are interpreted as induced by the cloud of fast electrons having propagated through the target and expanding into vacuum. The measurements have been performed using a laser-pulse duration of 320 fs and a laser energy of 20 J, varying the target thickness from 25, 14, and 9.4 mum. The experimental phase measurements are compared to simulations obtained by post-processing simulation data, run with a 1-D adiabatic plasma-expansion code. The comparison allows one to access, for the first time, to the dynamics of the density and temperature of laser-accelerated fast electrons in solid targets and expanding into vacuum. The same technique also allows one to have information regarding the cold electrons and the energy-partition dynamics.