Experimental characterization of a compact ECR ion source

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Abstract
A small ECR plasma source is experimentally evaluated. The compact, coaxial cavity source has an outer diameter of about 5.8 cm and is less than 15 cm in length, and can therefore be fitted on vacuum ports on existing MBE machines. Double- and single-Langmuir probes and an energy analyzer are used to measure ion density, electron temperature, plasma potential, and energy distributions at various downstream and cross-sectional positions in the plasma beam. The measurements are made for a variety of flow rates (2–30 sccm) and the corresponding pressures (from about 10−5 to 10−4 Torr), incident powers ranging from 80 to 164 W, and various gas types including argon and oxygen. The experimental measurements show that the ion source provides ion density of about 1011/cm3 at relatively low powers of 123 W and at sub-mTorr pressures. The ions created follow typical ambipolar diffusion out of the discharge creation region. Ions impinging downstream on a grounded substrate in an argon discharge show a narrow, peaked energy distribution that varies with pressure and power. Low-energy ion beams with energies less than 35 eV can easily be produced by varying the pressure and input power.