Impedance Mismatch study between the Microwave Generator and the PUPR Plasma Machine
- Polytechnic University of Puerto Rico, San Juan, 00919-2017 (Puerto Rico)
Impedance mismatch inside the connection from the microwave power generator to the plasma machine is studied. A magnetron power generator transmits microwaves of 2.45 GHz and variable power from 50W to 5000W, through a flexible rectangular waveguide to heat plasma inside a Mirror Cusp devise located at the Polytechnic University of Puerto Rico. Before the production of plasma, the residual gas of the devise must be extracted by a vacuum system (5Torr or better), then Argon gas is injected to the machine. The microwaves heat the Argon ions to initiate ionization and plasma is produced. A dielectric wall is used inside the rectangular waveguide to isolate the plasma machine and maintain vacuum. Even though the dielectric will not block the wave propagation, some absorption of microwaves will occur. This absorption will cause reflection, reducing the efficiency of the power transfer. Typically a thin layer of Teflon is used, but measurements using this dielectric show a significant reflection of power back to the generator. Due to the high-power nature of the generator (5KW), this mismatch is not desirable. An electromagnetic field solver based on the Finite Difference Time Domain Method(FDTD) is used to model the rectangular waveguide connection. The characteristic impedance of the simulation is compared with the analytical formula expression and a good agreement is obtain. Furthermore the Teflon-loaded guide is modeled using the above program and the input impedance is computed. The reflection coefficient is calculated based on the transmission line theory with the characteristic and input impedances. Based on the simulation results it is possible to optimize the thickness, shape and dielectric constant of the material, in order to seal the connection with a better match.
- OSTI ID:
- 20898796
- Journal Information:
- AIP Conference Proceedings, Vol. 875, Issue 1; Conference: 16. IAEA technical meeting on research using small fusion devices; 11. Latin American workshop on plasma physics, Mexico City (Mexico), 30 Nov - 3 Dec 2005; 5-9 Dec 2005; Other Information: DOI: 10.1063/1.2405928; (c) 2006 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 0094-243X
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
GENERAL PHYSICS
ABSORPTION
ARGON IONS
CUSPED GEOMETRIES
DIELECTRIC MATERIALS
ELECTROMAGNETIC FIELDS
IMPEDANCE
IONIZATION
MAGNETRONS
MICROWAVE RADIATION
PERMITTIVITY
PLASMA
POWER TRANSMISSION LINES
REFLECTION
SIMULATION
TEFLON
THICKNESS
THIN FILMS
VACUUM SYSTEMS
WAVE PROPAGATION
WAVEGUIDES