Examples of ITER CODAC requirements for diagnostics

1
Examples of ITER CODAC requirements for
diagnostics
S. Arshad
Colloquium on ITER-CODAC Plant Control Design
Handbook and EU Procurement of Control and
Instrumentation for ITER 28 October 2008
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Hot fusion plasma can be contained in a magnetic
field
3
Containment improves with size ITER will be
much larger than todays machines
New engineering and physics challenges for
measurement and control
4
Wide range of diagnostics needed to diagnose
fusion plasma
Port type
No. used
Equatorial
9
Upper
12
Lower
9
Additionally many measurements inside vessel

• UPPER PORT 10
• X-Ray Survey
• Imaging VUV Spectroscopy

• UPPER PORT 11
• Edge Thomson

• EQUATORIAL PORT 11
• X-Ray Crystal Spectroscopy, array
• Divertor VUV Spectroscopy
• X-Ray Survey
• Core VUV Monitor
• Neutral Particle Analyser
• Reflectometry

• EQUATORIAL PORT 9
• MSE
• Toroidal Interferometer / Polarimeter
• ECE
• Wide Angle TV/IR

• DIVERTOR PORT 10
• X-point LIDAR
• Divertor Thomson Scattering
• H-Alpha Spectroscopy

• DIVERTOR PORT 8
• Divertor Reflectometry

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The EU will supply a range of diagnostics to ITER
General scheme for processing of diagnostic data
Ports for diagnostics heating systems
Physics studies
Analog processing
Off-line processing
ADC
Real-time processing
Controller
Machine protection plasma control
Processed data from diagnostics (Courtesy of
EFDA-JET)
About 40 diagnostic systems installed in ports
and inside / outside the toroidal chamber 13 to
be supplied by the EU
Plasma shape neutron profile
Plasma wall interaction
Temperature density profiles

• Wide-angle viewing system
• Magnetics
• Radial neutron camera
• Core Thomson scattering
• Bolometers
• Core charge exchange recombination spectrometer
• Hard X-ray monitor
• Plasma position reflectometer
• Pressure gauges
• Thermocouples
• LFS collective Thomson scattering
• High-resolution neutron spectrometer
• Gamma-ray spectrometers

6
The magnetics diagnostic is a large system for
basic plasma control, machine protection and
physics studies
Purpose
Prototype magnetics sensors
Control
Protection
Physics

• Determine plasma current, shape and movement
• Measure thermal energy of plasma
• Detect and quantify plasma instabilities
• Reconstruct magnetic flux surfaces (equilibrium)
• Detect and quantify any current flowing from
  plasma into vessel

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In-vessel pick-up coil
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Ex-vessel pick-up coil
In-vessel pick-up coil

• Diagnostic comprises pick-up coils, flux loops,
  Rogowski coils
• 1050 sensors inside the vessel (shown in figure)
• 600 additional sensors outside vessel

Hall probe
External rogowski coil
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Overview of magnetics signal processing
Event triggers
B
Off-line processing
dB/dt
Int
Physics studies
ADC
Real-time processing
Amp
Control protection
dB/dt

• Around 1650 sensors in total

• Slow (4kHz) ADCs for basic equilibrium
• Fast (1 MHz) ADCs for instabilities
• Typically with optical isolation

• Data stored for specialist off-line studies
• Real-time signals distributed to other plant
  systems (power amplifiers for tokamak magnets,
  machine protection systems)

• Digital or analogue integrators
• Amplifiers

ALL NUMBERS ARE INDICATIVE
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Plasma current and shape (1/2)

• Plasma current measured by integrating magnetic
  field over poloidal contour (Amperes law)
• Plasma shape characterised by gap between plasma
  boundary (solid red line) and first wall
• Shape controlled by changing current in tokamak
  coils

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Plasma current and shape
Similar arrangement for 410 in-vessel Rogowski
coils feeding vessel current reconstruction code
Event triggers
B
Off-line processing
dB/dt
Int
Physics studies
ADC
Real-time processing
Amp
Control protection
dB/dt

• Around 750 sensors (of which 380 in-vessel)
• Typical raw signal from 0.05m2 pick-up coil in
  /-60mV range under normal operation /-5V at
  disruptions

• Integrated signals typically sampled at 4kHz
  (20kHz at events)
• Typically 16 bit ADC with dithering, 25 bits
  without)

• Calibration of signals
• On-line data validation checks and corrective
  actions (e.g. voting system with 3 toroidal
  positions)
• Second plasma current calculation from individual
  signals
• Plasma boundary and plasma-wall gaps determined
  (1-2cm accuracy) 100k FLOP/cycle (10ms cycle time
  ? 0.01GFLOPS)
• Control signals generated for gap control and
  distributed to power amplifiers for tokamak coils
• Data stored for specialist off-line studies
  including full equilibrium reconstruction
  combining data from other diagnostics (20GB per
  pulse)

• Individual signals integrated (typical time
  constant 100ms output /-5V) and digitised
  separately
• Integrated signal in range of 0.06Vs frequency
  response 10kHz drift lt0.35mVs after pulse of
  3600s
• Summing integrator for hardware calculation of
  plasma current (10kA-15MA range, 1 accuracy)

ALL NUMBERS ARE INDICATIVE
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High frequency instabilities analysis control
Event triggers
B
Off-line processing
dB/dt
Int
Physics studies
ADC
Real-time processing
Amp
Control protection
dB/dt

• Around 270 high frequency sensors (with response
  up to 100kHz)

• 16 bit resolution likely to be adequate
• Sampling rates up to 1 MHz
• Event triggering to manage data quantities

• Data stored for specialist off-line studies of
  order 50GB per pulse
• Real-time signals for feedback control
  (resistive-wall modes)
• Additional, more specialised, event triggers

• High frequency results in relatively strong
  (voltage-range) signals which can be recorded
  directly with low gain
• Frequency response up to 300kHz
• RMS signals from summing amplifiers may for rapid
  overview of instabilities or for event triggering

Similar arrangement for around 380 in-vessel
sensors for plasma vertical speed control 10kHz
sampling 30GB storage 1GFLOPS
ALL NUMBERS ARE INDICATIVE
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Overview of requirements for some diagnostics
System
Electronics
ADCs
Storage (per pulse)
Magnetics

• 1200 integrators
• 650 amplifiers

• 1600 slow ADC channels (20kHz)
• 270 fast ADC channels (1 MHz)

110GB
Bolometry

• 500 lock-in amplifiers (50kHz)

• 500 ADC channels

360MB
Charge Exchange

• Read-out from up to 75 CCD cameras (100
  spectra/sec. 560 pixels each)

• N/A

30GB
Core LIDAR TS

• 150 ADC channels at 20GSa/S 10-bit samples

100MB
ALL NUMBERS ARE INDICATIVE