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

Hot fusion plasma can be contained in a magnetic field

New engineering and physics challenges for measurement and control Containment improves with size – ITER will be much larger than today’s machines JET: World’s largest tokamak ITER R (m) 6.2 a (m) 2 IP (MA) 16 Bt (T) 5.3 Paux (MW) 40 – 90 Pa (MW) 80+ Q (Pfus/Pin) 10 Prad (MW) 48 tpulse (s) 400+ R a New engineering and physics challenges for measurement and control

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

The EU will supply a range of diagnostics to ITER Ports for diagnostics & heating systems General scheme for processing of diagnostic data 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 wall interaction Plasma shape & neutron profile 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

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

Overview of magnetics signal processing Event triggers dB/dt B Int Off-line processing Physics studies ADC Amp Real-time processing Control & protection dB/dt 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) ALL NUMBERS ARE INDICATIVE

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

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

High frequency instabilities – analysis & control Event triggers dB/dt B Int Off-line processing Physics studies ADC Amp Real-time processing Control & protection dB/dt 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 Similar arrangement for around 380 in-vessel sensors for plasma vertical speed control; 10kHz sampling; 30GB storage; 1GFLOPS ALL NUMBERS ARE INDICATIVE

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