An ion source using laser ablation

This article describes the measurement of the fractional ionization in an a blated plume produced by excimer laser, and the application of the plume as an ion source. Laser ablation of iron, aluminum, and tantalum with a KrF e xcimer laser was performed in a vacuum chamber. The ablated plume was caugh t by a cup type electrode used to measure the amount of charged particles a s current wave forms. Applying electrostatic potential larger than 40 V, th e current wave forms were separated into electropositive and electronegativ e peaks. Each peak indicates ions and electrons, respectively. The amount o f ions, 6 x 10(13) ions/pulse, was estimated by integrating the electroposi tive peak. The ionization degree of 1.7% was also estimated by a series of analyses. For an aluminum target, the ion current reached 2 A at the peak a nd 1 mA on average at 60 kJ/m(2), 500 mJ, and 50 Hz. (C) 2000 Laser institu te of America. [S1042-346X(00)00104-2].