High resolution CO{sub 2} interferometry on the TJ-II stellarator by using an ADC-based phase meter
- DENA Laser SL, 28035 Madrid (Spain)
A 10 MSample/s analog-to-digital converter has been used to analyze the signals from the double wavelength heterodyne interferometer (CO{sub 2} 10.6 {mu}m, HeNe 0.63 {mu}m) in the TJ-II stellarator. The phase difference between the two interferometers has been calculated using a new algorithm in Labview environment. A systematic study of the 1 MHz intermediate frequency has been done using our software and Labview tools. Different sources of noise and nonlinear effects have been analyzed. Crosstalk (from the reference path) has been detected and corrected by software. The complete system (single channel double pass) has been routinely working during the complete TJ-II autumn experimental campaign, providing the plasma line integral density in scenarious with average densities ranging from few 10{sup 18} m{sup -3} to more than 5x10{sup 19} m{sup -3}. The results have been compared with those from a 2 mm interferometer, obtaining an excellent agreement. Working with a final bandwidth of 4 kHz, a one pass line integral error level about {+-}-2x10{sup 17} m{sup -2} has been achieved.
- OSTI ID:
- 20636640
- Journal Information:
- Review of Scientific Instruments, Vol. 75, Issue 10; Other Information: DOI: 10.1063/1.1786638; (c) 2004 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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