1 Radiation hardness in ITER Diagnostics Robin Barnsley ITER Diagnostics Division - Overview of...

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Radiation hardness in ITER Diagnostics

Robin Barnsley

ITER Diagnostics Division

- Overview of Fusion and ITER

- ITER Diagnostics

- Labyrinth shielding

- X-ray spectroscopy

- Plasma modelling

- Neutronics modelling

- Radiation-hard detectors

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Leading magnetic confinement device is the Tokamak

- Closed magnetic field minimizes particle losses

- Combined toroidal and poloidal fields produce helical field, that stabilizes +ve/-ve charged particle drifts.

- Plasma current induced by inner poloidal coils.

- Additional heating from neutral beams and RF/microwave

- Self-heating from fusion alphas

1 Magnetic confinement fusion research

D-T fusion requires lowest temperature

Ein + D + T -> (4He + 3.5 MeV) + (n + 14.1 MeV)

Breeding T from Li:nslow + 6Li -> 4He + Tnfast + 7Li -> 4He + T + nslow

Energy multiplication, Q: Q = Pout / Pin

Breakeven, Q=1 Palpha + Pneutron = Pin

Ignition: self-heating Palpha = Pin

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The JET Torus Hall (www.jet.efda.org)

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Inside JET without and with plasma

Remote-handling in-vessel since 1997 Visible radiation dominated by D near edgeCore radiation mostly x-raysOn JET 0.5 < Prad < 5 MW

5

D-T fusion achievements to date

JET has unique D-T capability- Tritium handling plant- Remote handling- Shielded torus hall- DT compatible diagnostics- Neutral beam upgrade to ~ 40 MW- Proposed to run until ITER operational

For a JET D-T plasma,

with 20 MW input into the plasma

total output : max 16 MW

E

Record: Q = 0.8 (JET)

Steady state: Q = 0.3 (JET)

JET (Joint European Torus), located near Oxford, England, is the largest Tokamak worldwide, and is a leading test-bed for ITER physics and technology

6

AUG JET

ITER

Scaling to ITER from previous experiments

Physics performance can be extrapolated better than factor 2.

Technological developments ongoing for:

- First wall: blanket and divertor modules.

- Material properties under heavy neutron irradiation.

7

Participating Teams all ratified by end of 2007China, Europe, India, Japan, Russia, South Korea, USA.

Construction site: Cadarache, St Paul les-Durance, Provence, France

Goals: Develop and demonstrate the physics and technology required for a fusion power plant.

Construction: 10 yrs. Began in 2008 with preparation of the site

Operations: 10 yrs. Hydrogen phase > Deuterium phase > Low-duty D-T > High duty D-T

ITER overview

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ITER (www.iter.org)

- Superconducting Tokamak

- Single-null divertor

- Elongated, triangular plasma

- Additional heating from RF, and negative-ion neutral-beams and

500Pfus(MW)

10Q (Pfus/Pin)

80+P (MW)

40-90Paux (MW)

1.85, 0.5,

5.3Bt (T)

15(17)IP (MA)

850VP (m3)

2a (m)

6.2R (m)

1st EIROforum School on Instrumentation, CERN, 11-15 May 2009, R Barnsley

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ITER cross-section


11

Characteristics of the plasma radiation

Main plasma

- Fuel ions D-D or D-T are diluted by impurities. Eg 2%C, 0.1% O, 0.001% Ni.

-Density ~1020 /m3 ,

-Te ~ 25 keV, Ti ~ 25 keV.

Optically thick > ~1mm:

- Emits and absorbs RF and microwave.

- Electrons orbiting in magnetic field

Optically thin < ~1mm.

- Emits quasi-blackbody Bremsstrahlung spectrum peaked at few keV.

- Many discrete spectral lines from fuel and impurity neutrals and ions.

Neutron and gamma emission from fusion reactions.

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Passive Diagnostic Techniques

Magnetics Pick-up coils B-fields, position, current, stored energy

RF ~ 30MHz RF antennae Ion cyclotron emission

mm-wave Waveguide Electron cyclotron emission - Te profile

IR Camera Tile thermography

Visible Filters, Gratings Edge impurity spectroscopy, vis. Brems Zeff

VUV/XUV Grating + MCP Impurity spectroscopy, machine protection

Soft x-ray camera Diode array Broadband tomography

Soft x-ray survey Crystals + GPC Impurity spectroscopy, machine protection

High res. X-ray Crystal + MWPC Doppler spectroscopy of Ti, bulk motion

Hard x-ray Scintillators Supra-thermal electrons

-ray Scintillators Fusion products

C-X neutrals Mass-spec Ion dynamics

Ions, electrons Langmuir probe Edge Te, Ne

Wide band Bolometry Total radiated power

Neutrons Imaging, counting, spectroscopy, activation

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Active Diagnostic Techniques

1 MW, 1 GHz gryrotron Collective Thomson scatt. Ion dynamicsmm-wave ~ 100 GHz Reflectometry Plasma positionFIR DCN laser 0.2 mm Interferometer Density profileRuby laser LIDAR Thomson Scattering Electron density and temp.Neutral beam 100 keV Charge exchange spectr. Ion temp, impurity densityLithium beam ~ 20 keV Spectroscopy Edge Te, NeHeavy ion beam Vis spect, Mass spect E-fieldsLaser ablation Impurity injection Impurity transport

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Diagnostics are linked to physics and operations by ITER Measurements Requirements – about 45 parameter groups.

Below are some relating to Spectroscopy

MEASUREMENT PARAMETER CONDITIONRANGE or

COVERAGERESOLUTION ACCURACY

10. Plasma Rotation

VTOR 1-200 km/s 10 ms a/30 30 %

VPOL 1-50 km/s 10 ms a/30 30 %

12. Impurity Species Monitoring

Be, C rel. conc. 1x10-4-5x10-2 10 ms Integral 10 % (rel.)

Be, C influx 4x1016-2x1019 /s 10 ms Integral 10 % (rel.)

Cu rel. conc. 1x10-5-5x10-3 10 ms Integral 10 % (rel.)

Cu influx 4x1015-2x1018 /s 10 ms Integral 10 % (rel.)

W rel. conc. 1x10-6-5x10-4 10 ms Integral 10 % (rel.)

W influx 4x1014-2x1017 /s 10 ms Integral 10 % (rel.)

Extrinsic (Ne, Ar, Kr) rel. conc.

1x10-4-2x10-2 10 ms Integral 10 % (rel.)

Extrinsic (Ne, Ar, Kr) influx 4x1016-8x1018 /s 10 ms Integral 10 % (rel.)

28. Ion Temperature Profile

Core Ti r/a < 0.9 0.5 - 40 keV 100 ms a/10 10 %

Edge Ti r/a > 0.9 0.05 - 10 keV 100 ms TBD 10 %

32. Impurity Density Profile

Fractional content, Z<=10r/a < 0.9 0.5 - 20 % 100 ms a/10 20 %

r/a > 0.9 0.5 - 20 % 100 ms 50 mm 20 %

Fractional content, Z>10r/a < 0.9 0.01 - 0.3 % 100 ms a/10 20 %

r/a > 0.9 0.01 - 0.3 % 100 ms 50 mm 20 %


15INDiagnostic Neutral BeamEUBolometric Array For Divertor

tbdTritium Retention MonitorsEUBolometric Array For Main Plasma

tbdDust and Erosion MonitorsBolometric System

CNLangmuir ProbesEUCollective Scatt. (LFS front end)

JAIR Thermography DivertorJAPolarimetric Syst. (Pol. Field Meas)

USResidual Gas AnalyzersUSToroidal Interferom./Polarim

EUPressure GaugesRFThomson Scat/LIF Interfaces (Div. region)

EU/JAThermocouplesJAThomson Scattering (Edge)

EU/USIR Cameras, visible/IR TVEUThomson Scattering (Core)

Plasma-Facing Comps and Operational Diagnostics

Optical Systems

USDivertor InterferometerEUHigh Res Neutron Spectr (interfaces)

EUReflectometers for Plasma PosnKONeutron Activation System

RF/USReflectometers for Main PlasmaEU/RFGamma-Ray Spect. (interfaces)

IN/USECE Diagnostics for Main PlasmaRFNeutron Flux Monitors (Divertor)

Microwave DiagnosticsCN

Neutron Flux Monitors (Ex-Vessel)

EUHard X-ray MonitorJAMicrofission Chambers

USMSE (based on heating beam)RFVertical Neutron Camera

RFNeutral Particle AnalysersEURadial Neutron Camera

INBeam Emission SpectroscopyNeutron and Fusion Product Diag.

CNRadial X-Ray CameraEUHalo Current Sensors

IN/USX-Ray Crystal SpectrometersEUDiamagnetic Loop

JAVisible & UV Imp Mon (Div)EUContinuous Rogowski Coils

KOVUV Imp Mon (Main Plas and Div)EUDivertor Magnetics

RFH Alpha SpectroscopyEUIn-Vessel Magnetics

EU/RFCXRS Active Spectr. (based on DNB)EUOuter-Vessel Magnetics

Spectroscopic and NPA SystemsMagnetic Diagnostics

INDiagnostic Neutral BeamEUBolometric Array For Divertor

tbdTritium Retention MonitorsEUBolometric Array For Main Plasma

tbdDust and Erosion MonitorsBolometric System

CNLangmuir ProbesEUCollective Scatt. (LFS front end)

JAIR Thermography DivertorJAPolarimetric Syst. (Pol. Field Meas)

USResidual Gas AnalyzersUSToroidal Interferom./Polarim

EUPressure GaugesRFThomson Scat/LIF Interfaces (Div. region)

EU/JAThermocouplesJAThomson Scattering (Edge)

EU/USIR Cameras, visible/IR TVEUThomson Scattering (Core)

Plasma-Facing Comps and Operational Diagnostics

Optical Systems

USDivertor InterferometerEUHigh Res Neutron Spectr (interfaces)

EUReflectometers for Plasma PosnKONeutron Activation System

RF/USReflectometers for Main PlasmaEU/RFGamma-Ray Spect. (interfaces)

IN/USECE Diagnostics for Main PlasmaRFNeutron Flux Monitors (Divertor)

Microwave DiagnosticsCN

Neutron Flux Monitors (Ex-Vessel)

EUHard X-ray MonitorJAMicrofission Chambers

USMSE (based on heating beam)RFVertical Neutron Camera

RFNeutral Particle AnalysersEURadial Neutron Camera

INBeam Emission SpectroscopyNeutron and Fusion Product Diag.

CNRadial X-Ray CameraEUHalo Current Sensors

IN/USX-Ray Crystal SpectrometersEUDiamagnetic Loop

JAVisible & UV Imp Mon (Div)EUContinuous Rogowski Coils

KOVUV Imp Mon (Main Plas and Div)EUDivertor Magnetics

RFH Alpha SpectroscopyEUIn-Vessel Magnetics

EU/RFCXRS Active Spectr. (based on DNB)EUOuter-Vessel Magnetics

Spectroscopic and NPA SystemsMagnetic Diagnostics


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ITER diagnostics are port-based where possible

Each diagnostic port-plug contains an integrated instrumentation package


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In-Vessel

Distributed Diagnostics

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Divertor, Equatorial & Upper Port Diagnostics

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Ports contain several diagnostics

Common features:

High fluxes onto plasma-facing mirrors

- Nuclear radiation - 0.5 MW / m2

- Heat, peaking in x-rays

- Escaping neutrals and ions

Mirror/waveguide labyrinths for shielding

- Require extensive neutronics analysis

- Performance compromised

- No fibres, lenses or windows in port

Some systems cannot use labyrinths

- X-ray camera, spectroscopy

- Neutron and gamma cameras

Some systems require vacuum extensions

- VUV spectroscopy

- Neutral particle analyser

High electromagnetic loads

- Plasma current of 15MA can disrupt in 40ms



LocationNeutron

flux/cm2.s

Suitable technology Issues

Plasma - facing ~1014

Metal mirrorsRetro-reflectorsWaveguides

Deposition and erosion by plasma.Maintenance: - possible if in-port - almost impossible if in-vessel

In-vesselBehind blanket

~1012

Mineral-insulated cablePick-up coils for magnetics

Radiation induced, EMF, currents, insulation breakdownMaintenance almost impossible

Inside port-plug

~108 - 1012

MirrorsReplaceable detectors

Some maintenance possible

Behind port-plug

< ~108

Optical fibres, lenses, CCD detectors, conventional electronics.“Almost anything”

Easily maintainable

Radiation issues according to location

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Mirror labyrinth collection optics on ITER upper port #3Neutronics by G.E.Shatalov, S.V.Sheludiakov, Kurchatov Inst. Moscow

The neutron environment ranges from mild behind the port-plug to severe at the blanket. StSt:H2O 80:20,Allowable activation

at Flange <100 uSv/hrbehind BioSh <10 uSv/hr

Normalized to 500 MW fusion power Neutron flux at flange ~ 1. 107 n/cm2 s-1 This is less than inside JET torus hall.

Equivalent to local dose <5 uSv/h (10 days after s/d)

Total nuclear heating power to:BSM 420 kWA 58 kWB 0.43 kWC 9W

Addition power deposition in TFC ~10WM1 Heating ~2W/cc Total Neutron flux ~6.1013 n/cm2 s-1

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ArXVII spectrum from NSTX - Manfred Bitter

Te = 0.58 keV from all diel. satellites & line w; Ti = 0.45 keV

3000

2000

1000

03.94 3.95 3.96 3.97 3.98 3.99 4.00

Ph

oto

n C

ou

nts

/ C

ha

nn

el

Wavelength (Å)

(c) w

x y q r a k

n >

3 s

ate

llite

s

z

j

n

High-resolution x-ray spectroscopyExtensively, but not exclusively, He-like ions.

~Te/Z: 250eV: Ne, 500eV,:Ar, 2keV: Fe-Ni, 10keV:Kr

Requires/ >~ 5000, hence < 1.3 nm for crystals

Ti: Doppler broadening

Vtor/pol: Doppler shift

Te Dielectronic satellite ratio

ne Forbidden line ratio z/(x+y) (sometimes)

Zeff Continuum imp Impurity injection

nimp Absolute calibration

Simple and reliable - bent crystal & pos. sens. detector.

Crystals are cheap dispersive elements, eg Si < 1kEur

Energy resolving detector makes it doubly dispersive, with excellent signal-to-noise ratio.

All crystal-window-detector processes are volume effects, leading to calculable and stable calibration. (1 mm Carbon ~ transparent at 10 keV).

Detector developments have been the key to progress:

1st gen. Photographic film

2nd gen. Multiwire prop. counter, ~ 3 - 25 m radiius

3rd gen. Solid state eg CCD, 0.5 - 2 m radius

4th gen. Imaging with fast 2-d detector

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High resolution imaging crystal spectrometers

Recent advances in active pixel detectors such as Pilatus and Medipix have enabled a new generation of imaging crystal spectrometer.

The technique has moved quickly from demonstration, to routine production of a wide range of new physics results (Matt Reinke, John Rice, this meeting)

The ITER design has been based on this principle since 2003

Extensive analysis and modelling has been performed:- Plasma emission modelling- Spectrometer sensitivity and signal estimates- Neutronics analysis to optimize the forward position of detectors

Fig.14a. Spherical crystal optics Fig.14b. Toroidal crystal optics

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Advances in detector technology enable new measurement capability CERN-led Medipix 3 – in development

Active pixel detector- Each pixel has analog pulse processing, thresholds, and digital counter- 256 x 256 array. Pixels 55 um square - Multiple enrgy windows- 1 us pulse-process time per pixel - Radiation-hard to ~1014 neutron/cm2

Diagnostic applications- X-ray spectroscopy and imaging - Particle detection and spectroscopy - Fast visible and VUV framing (with MCP)- Neutron and gamma spectroscopy

27 September 2004 Michael Campbell

MEDIPIX2 Hybrid Pixel DetectorMEDIPIX2 Hybrid Pixel Detector

Detector and electronics readout are optimized separately

27 September 2004 Michael Campbell

Charge sensitive preamplifier with individual leakage current compensation2 discriminators with globally adjustable threshold3-bit local fine tuning of the threshold per discriminator1 test and1 mask bitExternal shutter activates the counter13-bit pseudo-random counter1 Overflow bit

Medipix2 Cell SchematicMedipix2 Cell Schematic

Preamp

Disc1

Disc2

Double Disc logic

VthLow

VthHigh

13 bits

Shift Register

Input

Ctest

Testbit

Test Input

Maskbit

Maskbit

3 bits threshold

3 bits threshold

Shutter

Mux

Mux

ClockOut

Previous Pixel

Next Pixel

Conf

8 bits configuration

Polarity

Analog Digital

Preamp

Disc1

Disc2

Double Disc logic

VthLow

VthHigh

13 bits

Shift Register

Input

Ctest

Testbit

Test Input

Maskbit

Maskbit

3 bits threshold

3 bits threshold

Shutter

Mux

Mux

ClockOut

Previous Pixel

Next Pixel

Conf

8 bits configuration

Polarity

Analog Digital

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3 PILATUS II Detectors Provide Continuous Spatial Coverage of He-like Ar Spectra

Bottom

Core

Top

Crystal

Detector

C-Mod Plasma(Height =72 cm)

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Lower Hybrid Wave Induced Rotation on Alcator C-ModMeasured by imaging crystal spectrometer (Ken Hill et al)

New measurement capability for non-NBI discharges

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High resolution imaging crystal spectrometer for ITER

Plasma coverage by toroidal viewsPlasma coverage by radial views

Crystal

• Yellow represents view tunnel within the port plug and its virtual extension into the plasma• Aim is to view the tangent to all plasma flux surfaces• Spatial coverage drives detector height

View from top of plug

radial

toroidal

Detector

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ITER impurity line emission and spectrometer signals

Top left Modelled ITER radial profiles

Top right Local emissivity of impurity spectral lines

(O’Mullane, ADAS-SANCO)

Bottom Simulated signals for imaging x-ray crystal spectrometer

Incremental radiated powers for added impurity concentrations of 10-5.ne are:

Ar 0.25 MW Fe 0.8 MW Kr 1.4 MW


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Z-plane cross section of the neutron flux, modelled in Attila finite-element neutron transport code

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Neutron spectra at the detector locations

1.0E+00

1.0E+01

1.0E+02

1.0E+03

1.0E+04

1.0E+05

1.0E+06

1.0E+07

1.0E+08

1.0E+09

1.0E+10

1.0E+11

1.E-07 1.E-06 1.E-05 1.E-04 1.E-03 1.E-02 1.E-01 1.E+00 1.E+01 1.E+02

energy (MeV)

ne

utr

on

flu

x (n

/cm

2s)

d1 d2d3 d4d5 d6

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Photon spectra at the detector locations

1.E+00

1.E+01

1.E+02

1.E+03

1.E+04

1.E+05

1.E+06

1.E+07

1.E+08

1.E+09

1.E+10

1.E+11

1.E+12

1.E-03 1.E-02 1.E-01 1.E+00 1.E+01 1.E+02

energy (MeV)

ph

oto

n fl

ux

(n/c

m2

s)d1 d2

d3 d4

d5 d6

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Background and lifetime for a Medipix-like detector

Detector location within port-plug

Rear Mid Front

X-ray – gamma background

Total gamma flux

(ph/cm2 .s)3 .104 9 . 106 1 . 1012

Fractional dead-time for 1% QDE

1 . 10-8 4 . 10-5 0.33

Neutron background Neutron flux > 1 keV

(n/cm2 .s)6 . 106 1.5 . 108 5 . 1011

Fractional dead-time for 1% QDE

2 . 10-6 5 . 10-4 0.18

Detector life

(ITER life ~ 2.107 s)

Time to reach fluence of 1014 n/cm2 (s) 2 . 1010 2 . 107 500

Saturation rate: 3 . 1010 /cm2 .s (106 /s per 55 um pixel)

Lifetime fluence of 1 MeV neutrons: 1014 /cm2

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High energy physics requires radiation-hard detectorsSLHC core neutron fluence >10^16/cm^2 over 10 yrs

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Estimated detector lifetimes along the line between front and rear detectors

1.00E+02

1.00E+03

1.00E+04

1.00E+05

1.00E+06

1.00E+07

1.00E+08

1.00E+09

1.00E+10

1 3 5 7 9

Line between front detector d5 (1) and rear detector d2 (10)

Det

ecto

r lif

etim

e (s

)

Fluence 10^14 / cm^2

Fluence 10^16 / cm^2

ITER lifetime

Maintainable

KU-1 glass


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Imaging Crystal Spectrometer Layout, with overlap between upper and equatorial views

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Neutron and Neutron and -cameras for ITER-cameras for ITER

Radial camera

- 20 Views total

- 12 ex-vessel

- 8 in-vessel – dictated by narrow port

Vertical camera

- Required to detect in-out asymmetry

- Difficult to integrate

- Divertor location favoured

Instrumentation

- Counters and spectrometers

- Fission chambers for neutrons

- Scintillators for gammas and neutrons

- Natural and CVD diamonds

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Summary- The ITER diagnostic system deals with radiation in a number of ways:

- Real hardness: waveguides, mirrors, mineral-insulated cables- Shielding: optical labyrinths, remote detectors- Use of radiation-hard detectors: x-ray spectroscopy and imaging

- Neutronics modelling is essential to optimize diagnostic designs

- ITER Diagnostics are entering the detailed design phase.

- Construction time for a complete diagnostic system: ~ 6 yrs

1 Radiation hardness in ITER Diagnostics Robin Barnsley ITER Diagnostics Division - Overview of...

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