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.