Assessment of measurement performance for a low field side IDTT plasma position reflectometry system

Abstract The Italian Divertor Test Tokamak (IDTT) facility will study advanced exhaust solutions applicable to DEMO. This new machine also opens the possibility to test and validate relevant non-magnetic control diagnostics in support of a DEMO design implementation. Reflectometry, compatible with a full grade reactor implementation, has been proposed as a source of real-time (RT) plasma position and shape measurements for control purposes, in replacement or complement of standard magnetic measurements, to ensure reliability and safety on the machine. Additionally, such a system can be useful to obtain the characteristics of edge turbulence, useful for Neoclassical Tearing Mode (NTM) control or to improve the efficiency of other diagnostics as Collective Thomson Scattering (CTS). This new control technique based on multiple, poloidally distributed, non-magnetic measurements, must be tested, in all of its aspects, before it can be fully implemented in future fusion reactors. IDTT will be one of the best candidates to implement and build a knowledge database of nonstandard reflectometry (away from the equatorial plane) that will be needed on DEMO and is currently unavailable. The performance of three Ordinary mode (O-mode) Plasma Position Reflectometers (PPR) at the Lower Field Side (LFS) on IDTT is assessed using the two-dimensional (2D) full-wave Finite-Difference Time-Domain (FDTD) code, REFMULF, in two of the foreseen IDTT plasma scenarios: 5MA Single Null (SN) and Double Null (DN) configurations.

[2]  Recent results on turbulence and MHD activity achieved by reflectometry. Invited paper , 2006 .

[3]  H. Bottollier-Curtet,et al.  Microwave reflectometry with the extraordinary mode on tokamaks: Determination of the electron density profile of Petula‐B , 1987 .

[4]  R. Albanese,et al.  DTT: a divertor tokamak test facility for the study of the power exhaust issues in view of DEMO , 2016 .

[5]  Jean-Pierre Berenger,et al.  A perfectly matched layer for the absorption of electromagnetic waves , 1994 .

[6]  C. Lechte,et al.  Edge turbulence effect on ultra-fast swept reflectometry core measurements in tokamak plasmas , 2018 .

[7]  C. Lechte,et al.  Investigation of nonlinear effects in Doppler reflectometry using full-wave synthetic diagnostics , 2020 .

[8]  M. Schubert,et al.  Reconstruction of the turbulence radial profile from reflectometry phase root mean square measurements , 2012 .

[9]  W. Treutterer,et al.  Diagnostics for plasma control – From ITER to DEMO , 2019, Fusion Engineering and Design.

[10]  F. Clairet,et al.  Ordinary-mode reflectometry: modification of the scattering and cut-off responses due to the shape of localized density fluctuations , 1996 .

[11]  M. E. Manso,et al.  Initialization of plasma density profiles from reflectometry , 1995 .

[12]  A. Silva,et al.  Modelling reflectometry diagnostics: finite-difference time-domain simulation of reflectometry in fusion plasmas , 2019, Journal of Instrumentation.

[13]  A. Silva,et al.  Assessment of a multi-reflectometers positioning system for DEMO plasmas , 2019, Journal of Instrumentation.

[14]  W. Treutterer,et al.  Real-time reflectometry – An ASDEX Upgrade DCS plugin App for plasma position and shape feedback control , 2017 .

[15]  V. Tribaldos,et al.  Microwave Reflectometry Diagnostics: Present Day Systems and Challenges for Future Devices , 2012 .

[16]  Reconstruction of hollow areas in density profiles from frequency swept reflectometry , 2020 .

[17]  S. Heuraux,et al.  Electron cyclotron resonance heating beam broadening in the edge turbulent plasma of fusion machines , 2015 .

[18]  C. Giroud,et al.  Global and pedestal confinement and pedestal structure in dimensionless collisionality scans of low-triangularity H-mode plasmas in JET-ILW , 2015 .

[19]  N. Yuan,et al.  FDTD Formulations for Scattering From 3-D Anisotropic Magnetized Plasma Objects , 2006, IEEE Antennas and Wireless Propagation Letters.

[20]  Stéphane Heuraux,et al.  Benchmarking 2D against 3D FDTD codes in the assessment of reflectometry performance in fusion devices , 2019 .

[22]  Constantine A. Balanis,et al.  Antenna Theory: Analysis and Design , 1982 .

[23]  F. Crisanti,et al.  The DTT device: Poloidal field coil assessment for alternative plasma configurations , 2017 .

[24]  Design status of the in-vessel subsystem of the ITER Plasma Position Reflectometry system , 2019, Journal of Instrumentation.

[25]  S. Hacquin,et al.  Unidirectional transparent signal injection in finite-difference time-domain electromagnetic codes -application to reflectometry simulations , 2005 .

[26]  Nazikian,et al.  Radial scale length of turbulent fluctuations in the main core of TFTR plasmas. , 1993, Physical review letters.

[27]  S. Hacquin,et al.  New density profile reconstruction methods in X-mode reflectometry. , 2017, The Review of scientific instruments.

[28]  F. Simonet,et al.  Measurement of electron density profile by microwave reflectometry on tokamaks , 1985 .

[29]  W. Treutterer,et al.  Reflectometry-based plasma position feedback control demonstration at ASDEX Upgrade , 2012 .