28/29 October 2008Colloquium on ITER-CODAC 1

Examples of ITER CODAC requirements for

diagnosticsS. Arshad

Colloquium on ITER-CODAC Plant Control Design Handbook

and EU Procurement of Control and Instrumentation for ITER

28 October 2008

28/29 October 2008Colloquium on ITER-CODAC 2

Hot fusion plasma can be contained in a magnetic field

28/29 October 2008Colloquium on ITER-CODAC 3

JET: World’s largest tokamak

ITER

R (m) 6.2

a (m) 2

IP (MA) 16

Bt (T) 5.3

Paux (MW) 40 – 90

P (MW) 80+

Q (Pfus/Pin) 10

Prad (MW) 48

tpulse (s) 400+

R a

New engineering and physics challenges for measurement and control

Containment improves with size – ITER will be much larger than today’s machines

28/29 October 2008Colloquium on ITER-CODAC 4

UPPER PORT 11• Edge Thomson

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

EQUATORIAL PORT 9• MSE• Toroidal

Interferometer / Polarimeter

• ECE• Wide Angle TV/IR

Port type

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

DIVERTOR PORT 8• Divertor

Reflectometry

DIVERTOR PORT 10• X-point LIDAR• Divertor Thomson

Scattering• H-Alpha Spectroscopy

Wide range of diagnostics needed to diagnose fusion plasma

No. usedEquatorial 9Upper 12

Lower 9

Additionally many measurements inside vessel

28/29 October 2008Colloquium on ITER-CODAC 5

The EU will supply a range of diagnostics to ITER

Analog processing ADC

Off-line processing

Real-time processing

ControllerMachine protection & plasma control

Physics studies

Ports for diagnostics & heating systems General scheme for processing of diagnostic data

Processed data from diagnostics (Courtesy of EFDA-JET)

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

About 40 diagnostic systems installed in ports and inside / outside the toroidal chamber; 13 to be supplied by the EU:

28/29 October 2008Colloquium on ITER-CODAC 6

The magnetics diagnostic is a large system for basic plasma control, machine protection and physics studies

• Diagnostic comprises pick-up coils, flux loops, Rogowski coils

• ~1050 sensors inside the vessel (shown in figure)

• ~600 additional sensors outside vessel

In-vessel pick-up coil

Copper Core

Polyimide ribbon

Glass fibre fillerGlass fibre filler

1st Copper layer(=5.5 mm,pitch=1mm)

Glass fibre filler

Copper or Stainlesssteel braided sheath

2nd Copper layer(=8.3 mm,pitch=1mm)

In-vessel pick-up coil

Ex-vessel pick-up coil

External rogowski coil

Purpose Prototype magnetics sensors

• 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

Control Protection Physics

Hall probe

28/29 October 2008Colloquium on ITER-CODAC 7

Overview of magnetics signal processing

• Around 1650 sensors in total

• Digital or analogue integrators

• Amplifiers

• 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)

Event triggers

Off-line processing

Real-time processing

Physics studies

Control & protection

dB/dt B

dB/dt

Int

Amp

ADC

ALL NUMBERS ARE INDICATIVE

28/29 October 2008Colloquium on ITER-CODAC 8

Plasma current and shape (1/2)

• Plasma current measured by integrating magnetic field over poloidal contour (Ampere’s law)

• Plasma shape characterised by gap between plasma boundary (solid red line) and first wall

• Shape controlled by changing current in tokamak coils

28/29 October 2008Colloquium on ITER-CODAC 9

Plasma current and shape

Event triggers

ADC

Off-line processing

Real-time processing

Physics studies

Control & protection

dB/dt B

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

• Individual signals integrated (typical time constant 100ms; output +/-5V) and digitised separately

• Integrated signal in range of 0.06Vs; frequency response ~10kHz; drift <0.35mVs after pulse of 3600s

• Summing integrator for ‘hardware’ calculation of plasma current (10kA-15MA range, 1% accuracy)

• 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)

Int

Amp

Similar arrangement for 410 in-vessel Rogowski coils feeding vessel

current reconstruction code

ALL NUMBERS ARE INDICATIVE

28/29 October 2008Colloquium on ITER-CODAC 10

High frequency instabilities – analysis & control

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

• 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

• 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

Event triggers

Off-line processing

Real-time processing

Physics studies

Control & protection

dB/dt B

dB/dt

Int

Amp

Similar arrangement for around 380 in-vessel sensors for plasma

vertical speed control; 10kHz sampling; 30GB

storage; 1GFLOPS

ADC

ALL NUMBERS ARE INDICATIVE

28/29 October 2008Colloquium on ITER-CODAC 11

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