Multichord optical interferometry of FRX-L's field reversed configuration
- Air Force Research Laboratory, Directed Energy Directorate, Kirtland AFB, New Mexico 87117 (United States)
A 0.633 {mu}m laser interferometer provides detailed time resolved information about the spatial distribution of the plasma density of field reversed configurations (FRC's) produced by the FRX-L experiment at Los Alamos National Laboratory. This experiment is an effort to produce a magnetized plasma with closed field lines suitable for compression by a solid metal liner imploded by the Shiva Star capacitor bank at the Air Force Research Laboratory. The interferometer probes a fanned array of eight chords through the FRC midplane, measuring the line integrated free electron density via its effect on optical phase shift relative to eight reference beams as a function of time. The reference beams are given nominally identical optical paths, except that they are folded for compactness and given an 80 MHz higher optical frequency by use of a Bragg cell beam splitter. After the beams are recombined, interference results in 80 MHz electromagnetic beat waves with dynamic phase shifts equal to those of the corresponding optical probes. Quadrature mixing of the electronically monitored light is then performed with rf components. Noteworthy features of the interferometer's design are the unique compact folding scheme of the reference paths, inclusion of a fused quartz tube in the reference path similar to that of the FRC's vacuum vessel to compensate for cylindrical lensing, and transmission of the interfering light via optical fibers to a rf shielded room for processing. Extraneous contributions to the phase shift due to vibration resulting from the system's pulsed magnetic field, and dynamic refractive changes in or near the fused quartz tube wall (possibly due to radiation heating) are corrected for.
- OSTI ID:
- 20861167
- Journal Information:
- Review of Scientific Instruments, Vol. 77, Issue 10; Other Information: DOI: 10.1063/1.2354568; (c) 2006 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 0034-6748
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
BEAM SPLITTING
BEAMS
CAPACITORS
CYLINDRICAL CONFIGURATION
FIELD-REVERSED THETA PINCH DEVICES
INTERFEROMETERS
INTERFEROMETRY
MHZ RANGE
OPTICAL FIBERS
PHASE SHIFT
PLASMA DENSITY
PLASMA DIAGNOSTICS
QUARTZ
RADIATION HEATING
REVERSE-FIELD PINCH
REVERSED-FIELD PINCH DEVICES
SPATIAL DISTRIBUTION
TIME RESOLUTION
VISIBLE RADIATION