Fast Sampling Upgrade and Real-Time NTM Control Application of the ECE Radiometer on ASDEX Upgrade

Abstract The ASDEX Upgrade tokamak employs a 60-channel electron cyclotron emission (ECE) radiometer diagnostic for the measurement of radial electron temperature profiles of the plasma. The data acquisition (DAQ) portion of the system has now been upgraded to sample at 1 to 2 MHz, and accordingly, electron temperature fluctuations from 500 kHz to 1 MHz may be measured. The high spatial resolution of [approximately]1 cm and flexible magnetic field coverage from 1.5 to 3.0 T remain unchanged. The system can now provide observations of plasma phenomena on the magnetohydrodynamic timescale, such as neoclassical tearing modes (NTMs) and toroidal Alfvén eigenmodes (TAEs). The upgraded and existing DAQ systems may be run in parallel for comparison, and some of the first plasma measurements using the two systems together are presented, along with an example of localization of [approximately]120-kHz TAEs in the fast ECE data. A principal planned application of the upgraded radiometer is integration into a real-time NTM stabilization loop using targeted deposition of electron cyclotron resonance heating (ECRH) or electron cyclotron current drive. For this loop, it is necessary to determine the locations of the NTM and ECRH deposition using ECE measurements. The NTM location is determined via correlation between ECE and Mirnov coil measurements, and results of this technique for (2,1) and (3,2) NTMs are presented. ECRH deposition is located by observing the modulation signature of the injected ECRH power in ECE measurements. Several additional applications enabled by the upgraded radiometer are also discussed.

[1]  R. J. La Haye,et al.  Neoclassical tearing modes and their controla) , 2005 .

[2]  W. Suttrop,et al.  Practical Limitations to Plasma Edge Electron Temperature Measurements by Radiometry of Electron Cyclotron Emission , 1996 .

[3]  F. Leuterer,et al.  Diagnosing Electron Heat Transport in ASDEX Upgrade with ECH Power Modulation , 2003 .

[4]  E. Mazzucato,et al.  Simultaneous Microwave Imaging System for Density and Temperature Fluctuation Measurements on TEXTOR , 2004 .

[5]  F. Leuterer,et al.  Enhancement of the stabilization efficiency of a neoclassical magnetic island by modulated electron cyclotron current drive in the ASDEX upgrade tokamak. , 2007, Physical review letters.

[6]  T. Blaney.  Signal-to-noise ratio and other characteristics of heterodyne radiation receivers , 1975 .

[7]  O. Sauter,et al.  Recent Electron Cyclotron Emission Results on TCV , 2007 .

[8]  Gerhard Raupp,et al.  Development of a feedback system to control MHD instabilities in ASDEX Upgrade , 2007 .

[9]  Gerhard Raupp,et al.  Real-time diagnostics at ASDEX Upgrade—Integration with MHD feedback control , 2008 .

[10]  F. Leuterer,et al.  Analysis methods and conditions for feedback controlled NTM stabilization , 2003 .

[11]  Neville C. Luhmann,et al.  Chapter 3: Microwave Diagnostics , 2008 .

[12]  G. Gantenbein,et al.  Status of the new multi-frequency ECRH system for ASDEX Upgrade , 2007, International Conference on Plasma Science.

[13]  Gerhard Raupp,et al.  Real-time diagnostics at ASDEX Upgrade : Architecture and operation , 2008 .

[14]  E. Mazzucato,et al.  Comparison study of 2D images of temperature fluctuations during sawtooth oscillation with theoretical models. , 2006, Physical review letters.

[15]  W. Suttrop,et al.  Electron cyclotron emission radiometer upgrade on the Joint European Torus (JET) tokamak , 2004 .

[16]  M. Rosenbluth,et al.  Chapter 5: Physics of energetic ions , 1999 .

[17]  A. Manini,et al.  Algorithms for the Control of NTM by Localized ECRH. Principles and Requirements of the Real Time Diagnostic and Control System , 2008 .

[18]  J. Contributors,et al.  Physics of ECE Temperature Measurements and Prospects for ITER , 2008 .

[19]  McGuire,et al.  Observation of nonlinear neoclassical pressure-gradient-driven tearing modes in TFTR. , 1995, Physical review letters.

[20]  E. Wolfrum,et al.  Integrated density profile analysis in ASDEX Upgrade H-modes , 2008 .

[21]  Y. S. Park,et al.  Real-time determination of magnetic island location for neoclassical tearing mode control in DIII-D , 2006 .

[22]  P. McCarthy,et al.  Pedestal Studies at ASDEX Upgrade , 2009 .

[23]  N. Salmon.  First electron temperature edge measurements on the asdex upgrade tokamak using a heterodyne radiometer , 1994 .

[24]  Zhoujun Yang,et al.  Electron cyclotron emission radiometer upgrade on the DIII-D tokamak , 2003 .

[25]  H. Zohm,et al.  Fast-ion losses due to high-frequency MHD perturbations in the ASDEX upgrade Tokamak. , 2008, Physical review letters.

[26]  E. Mazzucato,et al.  Simultaneous microwave imaging system for density and temperature fluctuation measurements on TEXTOR (invited) , 2004 .

[27]  E. J. Strait,et al.  MHD limits to tokamak operation and their control , 2003 .

[28]  G. Gantenbein,et al.  Analysis of the structure of neoclassical tearing modes in ASDEX Upgrade , 2001 .

[29]  F. Leuterer,et al.  Modulated ECRH power deposition in ASDEX Upgrade , 2003 .

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

[31]  R. Nazikian,et al.  Radial structure of Alfvén eigenmodes in the DIII-D tokamak through electron-cyclotron-emission measurements. , 2006, Physical review letters.

[32]  M. Ottaviani,et al.  An upgraded 32-channel heterodyne electron cyclotron emission radiometer on Tore Supra , 2005 .

[33]  Gerhard Raupp,et al.  Real time magnetic field and flux measurements for tokamak control using a multi-core PCI Express system , 2009 .

[34]  E. Lazzaro,et al.  Electron cyclotron emission temperature fluctuations associated with magnetic islands and real-time identification and control system , 2005 .

[35]  A. Donné,et al.  Effect of heating on the suppression of tearing modes in tokamaks. , 2007, Physical review letters.

[36]  K. Kawahata,et al.  Development of multichannel intermediate frequency system for electron cyclotron emission radiometer on KSTAR Tokamak. , 2008, The Review of scientific instruments.

[37]  G. Taylor.  Recent Developments in Electron Cyclotron Emission Research on Magnetically Confined Plasmas , 2007 .

[38]  Gerhard Raupp,et al.  Real-time diagnostic integration with the ASDEX Upgrade control system , 2009 .

[39]  W. W. Heidbrink,et al.  Basic physics of Alfvén instabilities driven by energetic particles in toroidally confined plasmas , 2008 .

[40]  A. Costley.  50 Years of Electron Cyclotron Emission Research , 2009 .

[41]  Kozo Yamazaki,et al.  Achievement of high fusion triple product, steady-state sustainment and real-time NTM stabilization in high-βp ELMy H-mode discharges in JT-60U , 2003 .