Journal
FUSION ENGINEERING AND DESIGN
Volume 74, Issue 1-4, Pages 847-851Publisher
ELSEVIER SCIENCE SA
DOI: 10.1016/j.fusengdes.2005.06.241
Keywords
automatic fringe jump corrector (AFJC); phase counter; LHD
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Phase counters, which are used with heterodyne interferometers for plasma density measurements, frequently suffer from phase jumping and cause difficulties for data interpretation. An automatic fringe jump corrector (AFJC) circuit has been developed to compensate for fringe jumps. The AFJC can correct phase jumps automatically in real-time. The AFJC, which is integrated on one chip, is installed on the presently working phase counter circuit. As for the specification of this phase counter the intermediate beat signal is 1 MHz, the phase detection range is 31 fringes with phase resolution of 1/80 of a fringe and the response time of 10 mu s. The circuit has been tested on the far infrared (FIR) laser interferometer on LHD. The AFJC works fine to correct fringe jumps, when fringe jumps occurred due to the strong density gradient produced by the hydrogen pellet injection. (c) 2005 Elsevier B.V All rights reserved.
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