Effect of plasma scale length on multi-MeV proton production by intense laser pulses

• Published in: Physical review letters Vol. 86; no. 9; pp. 1769 - 1772
• Main Authors: Mackinnon, A J, Borghesi, M, Hatchett, S, Key, M H, Patel, P K, Campbell, H, Schiavi, A, Snavely, R, Wilks, S C, Willi, O
• Format: Journal Article
• Language: English
• Published: United States The American Physical Society 26-02-2001
• Subjects: ELECTROSTATICS; LASERS; PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; PLASMA; PLASMA DENSITY; PRODUCTION; PROTONS; TARGETS
• ISSN: 0031-9007; 1079-7114
• DOI: 10.1103/physrevlett.86.1769

The influence of the plasma density scale length on the production of MeV protons from thin foil targets irradiated at I lambda(2) = 5 x 10(19) W cm(-2) has been studied. With an unperturbed foil, protons with energy >20 MeV were formed in an exponential energy spectrum with a temperature of 2.5+/-0.3 MeV. When a plasma with a scale length of 100 microm was preformed on the back of the foil, the maximum proton energy was reduced to <5 MeV and the beam was essentially destroyed. The experimental results are consistent with an electrostatic accelerating mechanism that requires an ultrashort scale length at the back of the target.