different number of extraction slits are used the height can be adjusted accordingly thus based on the dimensions of w and h given above there is a central region of about 8 cm in height and 60 cm in width free of magnetic field fig5 a and 5b show the extracted ion beam current densities obtained with the small form factor u03be u02dc 0 32 plasma source for two different precursor gases bf 3 and ph 3 as a function of input power as predicted there is a linear relationship between the extracted beam current j extr and the rf power with a slope of approximately 4 06 ma cm 2 kw and approximately 4 3 ma cm 2 kw for bf 3 and ph 3 respectively the high current density values demonstrate the very efficient coupling of the rf power to the plasma assuming an electron temperature of approximately 3 ev will result in a bohm velocity v b of the bf 2 ion of approximately 2 5 u00d7 10 5 cm s this results in equation 13 where e is the elementary charge calculus shows a plasma density n of approximately 5 u00d7 10 11 cm u2212 2 for 5 kw input rf power i e close to the maximum attainable inductively coupled plasma icp density the ion source described above allows the resulting plasma density and composition to be changed according to the desired beam current and elemental composition higher rf power and low flow rate low pressure.