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(above) Method for generating high-velocity beams of protons by using a tabletop laser. The experimental apparatus is placed inside a steel vacuum chamber. The laser beam, shown in green in this enhanced photograph, is focused by a parabolic mirror, in the foreground, onto aluminum foil (which is stretched across a screen mesh). The ions are accelerated off the back of the target in the plasma formed at the laser focus and detected by a track detector, shown in the background.
(above) A schematic of the experiment. The terawatt laser, focused on a thin foil, produces a collimated beam of high-energy protons.
(above) A typical image of a proton beam observed from behind the target as a high-intensity laser strikes a 1.8 micron thick aluminum foil. This is the first time a proton beam has been photographed head-on. The proton beam passed through a 25-micron Mylar filter, which corresponds to an energy above 1.2 MeV. The laser intensity on target is 2.1018 W/cm2 at second harmonics illumination normal to the target.
(above) Spectrogram of fast protons emitted in the forward direction and deflected in a dipole magnetic spectrometer. A dashed line shows the position of the slit image without the magnet. CR-39 was used as a detector and covered with three steps of Mylar filter of 2, 4 and 6 mm thickness, which corresponds to proton cut-off energies of 0.2, 0.3 and 0.5 MeV. (All figures and captions courtesy University of Michigan.)
reported by: University of Michigan researchers at the 1999 American Institute of Physics Division of Plasma Physics Meeting in Seattle.