Diapositive 1

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• Diagnostic needs for Heating and Current Drive
• Bécoulet,
• with the help of the HCD TG Executive Board

http//www.tpg.efda.org/hcd/public/index.htm
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Introduction

• Two categories of diagnostics
• Physics diagnostics providing information on
  the effect of the HCD systems
• On the confined plasma
• On the structure, PFCs,
• HCD diagnostics providing information on the
  way the power is coupled to the plasma and the
  system safety
• Overview of diagnostics work ongoing in the
  associations in the field of HCD no specific
  talk per se. Some illustrations along this talk.
  Associations are invited to present any relevant
  material in the second part of the session

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Physics Diagnostics
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Physics Diagnostics

• Physics of heating and current drive
• Fast ion population measurement
• lt1-2 MeV
• Perpendicular vs parallel
• Fast electron population measurement
• lt 100-200 keV
• Perpendicular vs parallel
• Deleterious effect of neutrons on Hard-X ray
  measurement
• Neutral population
• Isotopic ratio (ICRH)
• Current density profile Rotation profile Zeff
  profile ...
• Core MHD (..CD)
• Phase contrast imaging for electrostatic wave
  amplitude measurements (cf C-Mod)

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Physics Diagnostics

• Physics of RF-produced plasma for start-up or
  wall conditioning
• The information about these plasmas is generally
  poor because of the low density and temperature
  in partially ionized plasmas. Desirable 2-D
  density and temperature profiles, neutral
  pressure profiles, species concentration, fast
  ions,
• Information for the characterization of the
  plasma-wall interaction (uniformity,
  localization, strength, ) is needed for the
  interpretation of RF wall cleaning procedures.

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Physics Diagnostics

• Physics of wave coupling
• Density profile, in particular scrape-off and
  edge. Profile in front of antenna and ideally at
  different poloidal locations would allow better
  understanding of sheath effects and convective
  cell generation by the RF
• For the ITER system at reduced BT it would be
  necessary to measure density down to 0.5 1018m-3.
  Techniques available?
• Infrared camera for hot spots detection and
  sheath effect analysis
• Neutral pressure inside IC antenna box (in
  particular during ELMs)

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Physics Diagnostics

• Physics of wave coupling (2)
• Plasma density in contact with antenna elements
  Langmuir probes in and around antenna box (to be
  correlated with possible voltage stand-off
  reduction). Also important for sheath analysis.
• Electromagnetic probes for measuring RF fields at
  various places around the torus (in particular on
  field lines connected to the area in front of
  antennas or to antenna parts) would be useful.
  Langmuir probes in the areas would also be useful
  to diagnose far field sheath effects.

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HCD Diagnostics
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HCD Diagnostics NBI

• Diagnostics for NB protection systems
• Thermography for hotstpots due to beam losses.
  This has to cover the outer wall (first orbit
  losses) and in particular the area adjacent to
  the beam ports and any structures which connect
  magnetically with the zone in the mouth of the
  port where beam ionisation occurs in the
  scrape-off layer plasma, or by beam-gas
  collisions at the plasma edge. In general such
  thermography will require an IR field of view
  which is highly tangential.
• Thermocouples desirable in any dedicated
  protections designed to cater for such beam
  losses.
• As above for shinethrough monitoring/protection

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HCD Diagnostics NBI

• Diagnostics for NB protection systems (2)
• Fast measurements of neutral gas pressure in the
  duct and tokamak edge close to the beam port.
• Optical beam/gas emission measurements in the
  duct and close to beam port (a fast measure of
  ionisation by beam-gas collisions).
• Secure validated density measurement for
  shinethrough preventive interlock, and simple
  backup (is bremsstrahlung suitable in an
  ITER-like plasma?)
• Secure DC magnetic field probes for beamline and
  its active magnetic field cancellation system.

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HCD Diagnostics NBI

• Tomography of the Ion Source parameters and of
  the Beam
• Advanced diagnosis of ITER NB ion source and beam
  profile will contribute to understanding,
  performance and reliability of ITER heating beams

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HCD Diagnostics ICRH/LHCD

• Diagnostics for antenna protection and control
• Specific diagnostics are necessary for the safe
  operation of RF systems
• IR survey powering long pulse plasmas with RF
  systems require a detailed monitoring of the
  antenna front faces (sheath effects, fast
  particle losses)
• The plasma operation control loops must include
  the safe operation of the HCD power systems

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HCD Diagnostics ICRH

• Diagnostics for arc detection systems
• The existing arc detection systems (reflected
  power and probes, subharmonic detection, S-matrix
  arc detection) do not presently provide full
  confidence the all arcs will be detected without
  false detections
• Optical detection systems are only local
• Fully operational SMAD or SHAD is required to
  operate the JET ILA at full power in conjugate-T
  mode.
• it is desirable to investigate new ways of
  detecting arcs. Active arc detection systems
  based on radar techniques seem to hold such a
  promise.

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HCD Diagnostics RF

• Compatibility between the high power RF systems
  and the diagnostics !
• ECRH in particular for microwave diagnostics
• Windows, Feedthroughs, ..

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Conclusions and Priorities

• Physics
• Neutral Pressure (edge, antenna locations)
• Low n / low T plasmas (conditionning)
• Current density, rotation and Zeff profiles
• Fast ion population
• Fast electron population (with neutrons)
• RF probes
• Systems
• arc detection (ICRH, LHCD)
• IR survey (incl. interpretation control alg.)
• Tomography of the NB Ion Source parameters and of
  the Beam