Laser-driven proton acceleration via excitation of surface plasmon polaritons into TiO(2) nanotube array targets
Authors: Cristoforetti G., Baffigi F., Brandi F., D’Arrigo G., Fazzi A., Fulgentini L., Giove D., Koester P., Labate L., Maero G., Palla D., Romé M., Russo R., Terzani D., Tomassini P., Gizzi LA.
Autors Affiliation: 1 ILIL, Istituto Nazionale di Ottica, CNR, Pisa, Italy
2 Istituto per la Microelettronica e Microsistemi, CNR, Catania, Italy
3 Dipartimento di Energia, Politecnico di Milano, Milano, Italy
4 INFN, Sez. Milano, Italy
5 INFN, Sez. Pisa, Italy
6 Dipartimento di Fisica, Universit`a degli Studi di Milano, Milano, Italy
Abstract: In this paper we report the measurement of laser-driven proton acceleration obtained by irradiating nanotube array targets with ultrashort laser pulses at an intensity in excess of 1020W cm−2. The energetic spectra of forward accelerated protons show a larger flux and a higher
proton cutoff energy if compared to flat foils of comparable thickness. Particle-In-Cell 2D simulations reveal that packed nanotube targets favour a better laser-plasma coupling and produce an efficient generation of fast electrons moving through the target. Due to their sub-wavelength size, the propagation of e.m. field into the tubes is made possible by the excitation of Surface Plasmon Polaritons, travelling down to the end of the target and assuring a continuous electron acceleration. The higher amount and energy of these electrons result in turn in a stronger electric sheath field on the rear surface of the target and in a more efficient acceleration of the protons via the target normal sheath acceleration mechanism.
Journal/Review: PLASMA PHYSICS AND CONTROLLED FUSION
Volume: 62 (11) Pages from: 114001-1 to: 114001-10