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Electrical Engineering, Measurement and Control Technology
Experiments have been carried out to optimize the yield of Pb+4 ions from the plasma produced by a 100 J CO2 laser. The laser power density on the target surface was varied between 1010 W/cm2 and 9×1010 W/cm2 by changing the focal spot size. Data on the production of Pb+4 to Pb+10 ions are presented for the 15 and 40 ns laser pulse durations. The 10 mA/80 μs pulses of Pb+4 ions (about 1012 ions per pulse) were directed into an extraction aperture of 3.4 cm in diameter for optimal irradiation conditions. This is comparable with the parameters of the MEVVA ion source. Laser ion sources can be especially attractive due to the absence of the "noise" problem, typical for the MEVVA ion source, and because of the possibility of generating higher charge states. The emittance of the lead ion beam extracted from the laser-produced plasma was measured by using a 5 J laser, which provided plasma parameters (the electron temperature, ion velocities, and the charge state distribution) close to those of the plasma generated by the 100 J CO2 laser under optimized (for the yield of Pb+4 ions) conditions. The emittance was measured for 30 and 50 kV extraction voltages with a 10 μs temporal resolution. The value of about 400 π mm mrad was obtained for the lead ion beam with the total current of 10 mA, and a pulse length of 75 μs for about 75% of the beam ions. © 2002 American Institute of Physics.
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