Design & Characterization of the RF Matching Network for the LUPIN Ion Source

This study presents an impedance matching network (MN) design and characterization procedure

for the Large, Uniform Plasma for Ionizing Neutrals (LUPIN), an RF inductively coupled plasma

using a single strap, four turn (SSFT) coil and a multi-strap, single turn (MSST) coil. To match

power densities of the full-scale ion source, LUPIN will drive 10 kW RF power at 2 MHz

through a tunable L-type MN composed of 20 - 2000 pF capacitors placed in series and shunt.

LUPIN reaches electron densities (ne) ranging between 1014 and 1017 m-3 between 1 and 2 Pa.

Transformer equivalent circuit modeling is used to determine plasma inductance and resistance

for the SSFT coil. The SSFT coil has a nominal impedance of 105 Ω. A minimum 20% increase

in the load impedance is observed as ne increased from 1014 to 1017 m-3. Moreover, frequency

tuning across the generator range 1.80 - 2.17 MHz enabled an additional 15% change in the load

impedance with fixed electron density. Future research will use a vector network analyzer to

experimentally validate the MN design and build a matching network for the MSST coil.