Development of Efficient FPGA-Based Multi-Channel Phase Meters for IR-Interferometers

Infrared (IR) interferometry is a method for measuring the line-electron density of fusion plasmas. The significant performance achieved by FPGAs in solving digital signal processing tasks advocates the use of this type of technology in two-color IR interferometers of modern stellarators, such as the TJ-II (Madrid, Spain) and the future W7-X (Greifswald, Germany). In this work the implementation of a line-average electron density measuring system in an FPGA device is described. Several optimizations for multichannel systems are detailed and test results from the TJ-II as well as from a W7-X prototype are presented.

[1]  P. Zubarev,et al.  Precision Phase Discriminator for the Heterodyne Interferometric Plasma-Density Measurement Technique , 2003 .

[2]  H. Lamela,et al.  High resolution CO2 interferometry on the TJ-II stellarator by using an ADC-based phase meter , 2004 .

[3]  Miguel Correia,et al.  Reconfigurable ATCA hardware for plasma control and data acquisition , 2010 .

[4]  H. Lamela,et al.  CO2(λm=10.6 μm) He–Ne (λc=633 nm) two-color laser interferometry for low and medium electron density measurements in the TJ-II Stellarator , 2004 .

[5]  Joao M. C. Sousa,et al.  ATCA data acquisition system for gamma-ray spectrometry , 2008 .

[6]  C. Gil,et al.  Analysis and improvements of fringe jump corrections by electronics on the JET tokamak far infrared interferometer. , 2010, The Review of scientific instruments.

[7]  A. Barbuti,et al.  Fringe jump analysis and electronic corrections for the Tore Supra far infrared interferometer. , 2008, The Review of scientific instruments.

[8]  I. Hutchinson.  Principles of Plasma Diagnostics , 1987 .

[9]  P. Kornejew,et al.  Continuous Phase Measurement in the W7-X Infrared Interferometer by Means of a FPGA and High-Speed ADCs , 2010 .

[10]  V. Krivenski,et al.  TJ-II Project: A Flexible Heliac Stellarator , 1990 .

[11]  M. Hirsch,et al.  Heterodyne methods in millimetre wave plasma diagnostics with applications to ECE, interferometry and reflectometry , 1997 .

[12]  A. Murari,et al.  Real-time recovery of the electron density from interferometric measurements affected by fringe jumps , 2006 .

[13]  O. Nieto-Taladriz,et al.  Continuous plasma density measurement in TJ-II infrared interferometer—Advanced signal processing based on FPGAs , 2010 .

[14]  H. Dreier,et al.  Design of multichannel laser interferometry for W7-X , 2006 .

[15]  Two color multichannel heterodyne interferometer set up for high spatial resolution electron density profile measurements in TJ-II. , 2010, The Review of scientific instruments.

[16]  Octavio Nieto-Taladriz,et al.  Improved Interval-Based Characterization of Fixed-Point LTI Systems With Feedback Loops , 2007, IEEE Transactions on Computer-Aided Design of Integrated Circuits and Systems.

[17]  T. Kirimoto,et al.  Performance analysis of Independent Component Analysis to separate mixtures of complex sinusoidal signals , 2008, 2008 SICE Annual Conference.

[18]  P. Kornejew,et al.  Admissible Crosstalk Limits in a Two Colour Interferometers for Plasma Density Diagnostics. A Reduction Algorithm , 2008 .

[19]  K. C. Lee,et al.  Fringe-jump corrected far infrared tangential interferometer/polarimeter for a real-time density feedback control system of NSTX plasmas. , 2010, The Review of scientific instruments.