Quasi-quadrature interferometer for plasma density radial profile measurements
A cw Mach Zehnder multichannel interferometer has been developed to measure time-dependent fractional fringe shifts with an accuracy of one-fortieth fringe. The design is quasi-quadrature in that known phase shifts, introduced in the reference beam, are time multiplexed with the normal reference beam. This technique requires only one detector per interferometer channel as compared to two detectors for most quadrature designs. The quadrature information makes the sense of density changes unambiguous, it automatically calibrates the instrument during the plasma event, and it makes fringe shift measurements virtually independent of fringe contrast fluctuations caused by plasma refractive and/or absorptive effects. The interferometer optical design is novel in that the electro-optic crystal used to introduce the 90/sup 0/ phase shifts is located in the common 2-mm-diam HeNe entrance beam to the interferometer, by exploiting polarization techniques, rather than in the expanded 1--2-cm reference beam itself. This arrangement greatly reduces the size, cost, and high-voltage requirements for the phase modulating crystal.
- Research Organization:
- Mathematical Sciences Northwest, Inc., P.O. Box 1887, Bellevue, Washington 98009
- OSTI ID:
- 6246072
- Journal Information:
- Rev. Sci. Instrum.; (United States), Vol. 50:7
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
MACH-ZEHNDER INTERFEROMETER
DESIGN
PLASMA DIAGNOSTICS
HELIUM
LASER-RADIATION HEATING
MULTI-CHANNEL ANALYZERS
MULTIPLEXERS
NEON
PARTICLE BEAMS
PHASE SHIFT
PHOTOMULTIPLIERS
PLASMA DENSITY
POLARIZATION
PULSE GENERATORS
BEAMS
CRYOGENIC FLUIDS
ELECTRONIC EQUIPMENT
ELEMENTS
FLUIDS
FUNCTION GENERATORS
HEATING
INTERFEROMETERS
MEASURING INSTRUMENTS
NONMETALS
PHOTOTUBES
PLASMA HEATING
PULSE ANALYZERS
RARE GASES
700102* - Fusion Energy- Plasma Research- Diagnostics