Generating Proton Beams Exceeding 10 MeV Using High Contrast 60TW Laser**Supported by the National Basic Research Program of China under Grant No 2013CBA01502, the National Natural Science Foundation of China under Grant Nos 11475010, 11575011 and 11535001, and the National Grand Instrument Project under Grant No 2012YQ030142.

Abstract

A prototype of a laser driven proton accelerator is built at Peking University. Protons exceeding 10 MeV are accelerated from micrometer-thick aluminum targets irradiated by tightly focused laser pulse with 1.8 J energy and 30 fs duration. The beam energy spectrum and charge distribution are measured by a Thomson parabola spectrometer and radiochromic film stacks. The sensitivity of proton cut-off energy to the focusing of the laser beam, the pulse duration, and the foil thickness are systematically investigated in the experiments. Stable proton beams have been produced with an optimized parameter set, providing a cornerstone for the future applications of laser accelerated protons.