Real-time, vibration-compensated CO/sub 2/ interferometer operation on the DIII-D tokamak
A multichannel, two-color, quadrature heterodyne interferometer is used to measure the line density in the DIII-D tokamak. The unique feature of this real-time vibration-compensated interferometer is the combination of high speed (1 MHz), high resolution (2..pi../256), and wide range ( +- 8193 fringes). Quadrature phase information from a CO/sub 2/ laser (10.6 ..mu..m) and a He--Ne laser (0.63 ..mu..m) are digitized with high-speed (6 MHz) flash digitizers. Zero crossings of the signals are counted with digital circuitry yielding quarter fringe resolution with a 4-MHz bandwidth. Further fringe resolution of 1/256 is provided at 350 kHz by a PROM which uses the digital signals as input to a look-up table. Analog line density is presently available at 80 kHz with a system noise equivalent phase shift of +- 2/256. Error monitoring is provided for low signal amplitude and exceeding the maximum fringe rate. In addition, a method to prevent coating of in-vessel mirrors due to plasma and vessel wall cleaning discharges has been developed.
- Research Organization:
- GA Technologies, P.O. Box 85608, San Diego, California 92138
- OSTI ID:
- 6964499
- Journal Information:
- Rev. Sci. Instrum.; (United States), Vol. 59:7
- Country of Publication:
- United States
- Language:
- English
Similar Records
Precise density profile measurements by using a two color YAG/CO{sub 2} laser imaging Interferometer on LHD
High resolution CO{sub 2} interferometry on the TJ-II stellarator by using an ADC-based phase meter
Related Subjects
INTERFEROMETERS
DESIGN
RESOLUTION
PLASMA DIAGNOSTICS
TOKAMAK DEVICES
DATA ACQUISITION SYSTEMS
ELECTRON DENSITY
ELECTRONIC CIRCUITS
REAL TIME SYSTEMS
CLOSED PLASMA DEVICES
MEASURING INSTRUMENTS
THERMONUCLEAR DEVICES
700102* - Fusion Energy- Plasma Research- Diagnostics