The JET-ITER Like
Wall experiment&Use of compact
spectrometer infusion plasmas
S. Brezinsek
on behalf of
JET-EFDA Contributors
S. Brezinsek / 16.01.2013 / Avantes/ 1(28)1 Nuclear Fusion and Plasma-Surface Interaction
 The ITER-Like Wall at JET
 Installation
 Key Results
 Spectroscopic Diagnostics
 Requirements
 Compact spectrometer Summary

S. Brezinsek / 16.01.2013 / Avantes/ 2(28)2Nuclear Fusion by Gravity


Nuclear fusion of protons dueto high gravity forces in corefuelashpp chain1
1

H + 11H

H + e+ + n2121

1H + 1H+ energy

He + γ32protons
323

He +2 He

42HeliumHe +2 11 H
Core temperature: 1.3 keVPlasma pressure: 1016 Pa

Plasma density: 1032 m-3

HeII at 30.4nm

S. Brezinsek / 16.01.2013 / Avantes/ 3(28)1eV=11600K

3

Nuclear Fusion by Magnetic Confiment

Nuclear fusion due to gravity not possible in magnetic confinement experiments

Thermonuclear reaction with highest reaction rate: DT fusion

Measure for fusion power is the triple product (Lawson criterion):ion density ni (1020m-3) x ion temperature Ti (10KeV) x confinement time tE (5s)

Tritium production (breeding):
6Li + n  He + T + 4.8 MeV
7Li + n  He + T + n‘ – 2.5 MeV

The tokamak principle … pulsed plasma

S. Brezinsek / 16.01.2013 / Avantes/ 4(28)4DT Fusion Experiments
DT experiments in JET and TFTR executed Fusion power demonstrated (up to 60% of injected power) Next step device shall demonstrate 10 x power amplification => ITER
 Support in present tokamaks to address critical questions => PWI

J. Jacquinot PPCF 1999

Next DT experiment in JET with ITER-like Wall in 2015
 ITER plasma scenario development and W compatibility
 Plasma-wall interaction studies: Tritium retention/removal techniques Alpha particle heating and MHD instability studies
S. Brezinsek / 16.01.2013 / Avantes/ 5(28)5Plasma-Wall Interaction Processes
Main plasma

Reflection

Scrape-offlayer

Re-depositionand co-deposition
ErosionnLow temperature plasma
in the plasma edge
Te= 1-50 eV
Ne= 1-50x1019m-3
EFDA TaskForce Plasma-Wall-Interaction

S. Brezinsek / 16.01.2013 / Avantes/ 6(28)6First Wall Materials for Magnetic Fusion
Plasma Performance
Components Lifetime

Fuel Retention
1
D/C
D/BeO
D/Be
D/Be
D/Be
D/W
D/(W+C)
D/(Be+C)

Radiation
0.1

Dilution

D/C
0.01

D/Be

0.001

High wall ersion for low Z,
but no melting of C.

0100

200

300

400

500

600

700

800

Temperature (C)Wall erosion by D+ is low with high Z.
Only intrinsic impurities sputter(Ion impact energy: Ei = 3ZTe + 2Ti)
+ neutron hardness

D/W

Tritium retention by codeposition ismain issue for carbon
Minimum impact on
fusion performance with low Z

EFDA TaskForce Plasma-Wall-Interaction

S. Brezinsek / 16.01.2013 / Avantes/ 7(28)7ITER – the next step
500 MW fusion power
Power amplification Q=10
burn time > 8 minutes
Major radius:
Minor radius:
Volume:Plasma current:
Magnetic field:
Stored energy:
Auxiliary heating:
Height:Diameter:First Wall:
Divertor:

http://www.iter.org/

6.2 m
2.0 m
840 m315 MA
5.3 T (12 T)
350 MJ
70-100 MW
~25 m
~26 m
Beryllium
Tungsten / (Carbon)

International Project: EU, Japan, USA,Russia, China, South Korea, India

EU has a cost share of 46% - others 9%

S. Brezinsek / 16.01.2013 / Avantes/ 8(28)8 Nuclear Fusion and Plasma-Surface Interaction
 The ITER-Like Wall at JET
 Installation
 Key Results
 Spectroscopic Diagnostics
 Requirements
 Compact spectrometer Summary

S. Brezinsek / 16.01.2013 / Avantes/ 9(28)9First Wall Combinations in ITER
Critical issues: safety and lifetime„or“ fuel retention and first wall erosion

Beryllium

ITER~1 year full DT
operationTungsten

J. Roth et al.
JNM 2009http://www.iter.org/Carbon

 Fuel retention predictions made on basis of CFC
devices, laboratory experiments and modelling Benchmark tokamak experiment required

S. Brezinsek / 16.01.2013 / Avantes/ 10(28)10ITER-Like Wall at JETITER

 ITER-material mix used for the first in a tokamak
 “Carbon-free” environment
 Reduced tritium retention
 Loss of carbon as main radiator

JET Change in operational space Need for better plasma control
 Need for heat load mitigation schemes Main goals of the ILW experiment
I.

Demonstrate low fuel retention, migrationand possible fuel recovery

II. Demonstrate plasma compatibility
with metallic walls
V. Philipps
FED 2011
G. Matthews
PSI 2012

 Input to the decision about the first ITER divertor
S. Brezinsek / 16.01.2013 / Avantes/ 11(28)11Installation via Remote Handling Systems

S. Brezinsek / 16.01.2013 / Avantes/ 12(28)12ILW Installation
Be limiter

Total: 2t of Be installedbulk
W divertor

Total: 2t of W installed

Ph. Mertens
PSI2012

 Removal of CFC tiles => no active cleaning of the vessel wall => residual C content
 Complete installation of 82 273 parts in one shutdown by remote handling system
 ITER-wall material combination, but only inertial cooled plasma-facing components
 New energy and power loadS.limitations
imposedwith 13(28)respect to JET-C
Brezinsek / 16.01.2013/ Avantes/13

24.8.2011: First Plasma (Limiter Shape)
 Complex cycle of heating and glow discharge
in D performed before first plasma attempt First breakdown successful

 “Clean” plasma in limiter phase Be/C ratio changed by more than a factor
100 with respect to JET with CFC walls

Ohmic plasma in limiter shape
S. Brezinsek / 16.01.2013 / Avantes/ 14(28)14Monitoring Pulse
H-modeL-mode
ohmicdensitylimiterNBI

Ohmic phase of first campaign repeated regularly in monitoring pulse to study
evolution of impurities (Be, C, O, Ar) , plasma conditions, material migration ….
S. Brezinsek / 16.01.2013 / Avantes/ 15(28)15Stable H-mode Operation
Pulse 82240 IP=2.0MA, BT=2.1T, Zeff=1.2
PNBI, PICRH
PRAD, [MW]Type I ELMy H-modes achieved in low
and high triangular plasma with NBI

 Operational window is smaller and requires
 Gas fuelling (to reduce W source)nC[1019 m-3]

 Minimum ELM frequency (to flush W)
 Central heating (to avoid peaking)otherwise W-accumulation can occur

βN

H98y2

 Stable ELMy H-mode at D injection rates Γ≥
0.5x1022/s with H98~1 (Ip=2.0 MA, Bt=2.0 T)
 ELM flushing successful at f>10Hz

Ha [a.u.]1314

 W concentration below CW~5x10-5

15time [s]

16

17

18
E. Joffrin
IAEA2012

S. Brezinsek / 16.01.2013 / Avantes/ 16(28)16Comparison JET-C vs. JET-ILW
Long Term Fuel Retention
2210L-mode

H-modetype III

21

10Reduction

2010ohmic

1910ab cdegas balances with different conditions

low triangularity
high triangularity

H-modetype I

height [m]retention rate [D/s]normalised to divertor time

ILW (with cryo pump)
ILW (with turbo pump)
ILW (NBI & long outgasing)
CFCfS. Brezinsek et al.
IAEA 2012major radius [m]Long term fuel retention rate below 1.5x1020Ds-1 (w.r.t. to divertor operation time / all scenarios)
Moderate increase of retention rate with divertor flux
Retention rate reflects the upper limit as long term outgassing reduces the inventory furtherReduction is in line with expectations for ITER and allow operation within saftey limits
main reason: lower retention in Be layers (factor 10) and reduction of residual C by factor 10
S. Brezinsek / 16.01.2013 / Avantes/ 17(28)17Initial Material Migration Experiment
Measure and simulate initial start-up situation with Be/W material mix First wall Be erosion by impinging ions => transport in the scrape-off layer=> deposition in the W divertor => material mixing
 Be deposition in both legs, but initial Be contamination from limiter plasmas
Be flux in the divertor after first 1000 plasma seconds

SOLflow

10DIVIMPBeII 527nm
Be neterosion

Experiment

Ion flux
Vessel walls

B×∇B

BeII [1012 ph/(cm2 s sr)]

8642PFRdeposition/ erosion

0W divertor target plates

Inner divertor
2.2

Outer divertor

2.4
2.6
2.8
LOS major radius at z=-1.6 [m]S. Brezinsek / 16.01.2013 / Avantes/ 18(28)3.0

3.2 K. KriegerPSI201218

 Nuclear Fusion and Plasma-Surface Interaction
 The ITER-Like Wall at JET
 Installation
 Key Results
 Spectroscopic Diagnostics
 Requirements
 Compact spectrometer Summary

S. Brezinsek / 16.01.2013 / Avantes/ 19(28)19Measurement of Wall Fluxes
Are Be and W suitable first wall materials?
What is the impact of the Be and W influx from the plasma edge to the centre?
 Measurement of the poloidal distribution of Be, C and W sourcesin the divertor and the main chamber.
 Measurement (real time) of transient events in Be and W sources.
 Measurement of photon fluxes of eroded species.
 Determination of core W concentrations.
 Avantes AvaSpec systems with 2048 pixel liner array (200µm) height used toaddress erosion source functions.
 Wavelength span optimised for fusion plasmas:
Be I-IV, C I-IV, O I-II, Ar I-II, Ne I-II, He I-II, W I-II and H, D, T atomic lines
Molecular transtions: BeD, CD, D2, N2, CN etc.
 High resolution spectrometer for Zeeman-splitting analysis
 Photomultiplier tubes for fast (below 200µs time resolution) events
 Endoscope 2D cameras with interference filters for spatial information
Total spectroscopic system update: ~3 Mio € + internal costs
Internal costs: design, manufactoring, software development
S. Brezinsek / 16.01.2013 / Avantes/ 20(28)20Wall Flux Measurements
8x4 custom-made compact spectrometer (KS8)
to monitor inner wall sources BeII(527nm),CIII(465nm), W(400nm), Dα etc...
UV

VIS1 VIS2 NIR

fibre to JET(>100m)JET inner wall (octant 7)
NBI shine
throughprotection

Poloidallimiter

wavelength coverage:
380nm-915 nm
time resolution:~100 ms

Avantes: AvaSpec+ 5 custom-made compact spectrometer (KS3)

Cross-dispersion spectrometer to distinguishinner/outer wall sources via Zeeman-splitting
wavelength range:
365-705nm
spectral resolution:
20 000aperture: f/3.6
EMCCD detector

KS3
main chamberline-of-sightBe (tile)

KS8
main chamberlines-of-sightBe (on Inconel)

W (on CFC)

S. Brezinsek / 16.01.2013 / Avantes/ 21(28)21Optical Arrangment – long distance

Spot size

S. Brezinsek / 16.01.2013 / Avantes/ 22(28)22System Composition
24 monitoring systems
KS8

8 specific systems
KS86 systems (diff. Limiter)
KS3S. Brezinsek / 16.01.2013 / Avantes/ 23(28)23System Arrangement
patch panel

100m
UV fibre
4 x splitter
tokamak

4 ch Avaspec

PC Avasoft

spectrometer room

Control& Trigger
Unitcontrol room

Development of own
control and timming software under UNIX
(generalised for all spectrometers at JET)
S. Brezinsek / 16.01.2013 / Avantes/ 24(28)24Optical Splitter Design

S. Brezinsek / 16.01.2013 / Avantes/ 25(28)25Emission Spectrum – KS8
Identification of main impurity lines:
BeI-III, CI-IV, OI-II, NI-IV
and fuel lines Dγ, Dδ in the fullrange between 360 and 1000nm
8 lines-of-sight = 32 devices

In-situ calibration
with Ulbricht sphere in torus
during shut down phase

S. Brezinsek / 16.01.2013 / Avantes/ 26(28)26

Typical Output Data
Identification of main impurity lines:
BeI-III, CI-IV, OI-II, NI-IV
and fuel lines Dγ, Dδ
Spectral line integration withbackground subtraction
Time Traces on common time baseMultiple lines-of-sight=> Poloidal and toroidal distribution
Flux evolution as function ofdischarge parameter

S. Brezinsek / 16.01.2013 / Avantes/ 27(28)27Summary JET ITER-Like Wall Project successful
 Operation with Be and W wall materials
 Low fuel retention

 Compact spectrometers
 Custom-made devices according to fusion needs developed Avantes successfully installed in fusion environment Excellent data for monitoring and dedicated physics studies obtained

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FAX:048-871-0068

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S. Brezinsek / 16.01.2013 / Avantes/ 28(28)28