Millimeter Wave Plasma Interferometry in the Near Field of a Hall Plasma Accelerator (PREPRINT)
Abstract
Measurements are described of electron number density in the near field of a 200W Hall plasma accelerator using a 90 GHz microwave interferometer. The system is of a phase-bridge design, utilizing two signal arms from a fixed frequency source (one passing through the plasma) that recombine at two balanced mixers. A line-integrated electron density is obtained by comparing the in-phase and quadrature signals from the mixers. Measurements across chords through a "symmetric" plasma plume are Abel inverted to give the radial variation in the plasma density. The first direct non-intrusive measurements of the electron density in the near field of this source reveals structure not previously resolved with electrical probes. This interferometer is suitable for measuring time-dependent plasma density fluctuations offering non-intrusive information about plasma oscillations and instabilities in the near exit region where electrical probes are known to interfere with the discharge operation.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jan 27, 2006
- Accession Number
- ADA456676
Entities
People
- Mark Cappelli
- Nicholas C. Gascon
- William Hargus
Organizations
- Stanford University