Ion acceleration by a double stage accelerating device for laser-induced plasma ions

Abstract

A new laser ion source configuration was studied and realized in order to generate and accelerate ions of different elements. This ion source consisted of a laser-induced plasma from solid targets where the plume was made to expand before the action of the accelerating field. The accelerating field was reached by the application of two high voltage power supplies of different polarity. Therefore, the ions were made to undergo double acceleration that can imprint a maximum ion energy up to 160 keV per charge state. We analyzed the extracted charge from a Cu target as a function of the accelerating voltage at the laser fluences of 1.7 and 2.3 J/cm2. At 60 kV of total accelerating voltage and higher laser fluence, the maximum ion dose was 1012 ions/cm2. Under this last condition, the maximum output current was 5 mA and the emittance measured by the pepper pot method resulted in 0.22π mm mrad. With this machine, biomedical materials such as polyethylene were implanted with carbon and titanium ions. At doses of 6×1015 ions/cm2, the polyethylene surface increased its micro-hardness by about 3-fold, as measured by the scratch test.