Overblik over fusionsdiagnostikker. Poul Kerff Michelsen.

Overblik over fusionsdiagnostikker.

Poul Kerff Michelsen

16/11/20102 Risø DTU, Technical University of Denmark

Oversigt• Introduktion• Tokamakken• Typiske værdier plasma parametre• Strøm-spændingsmålinger• Langmuirprobe• Brydningsindeks/dielektritetskonstanten• Andre tætheds- og temperaturmålinger• Tæthed- og temperaturprofiler• Andre diagnostikker


Tokamakken

Magnetspoler til toroidalfeltet

Plasma og også den sekundære

vikling TransformerjernkerneMagnetfeltlinje

Primærvikling


Magnetiske felter som kan holde et plasma i ligevægt


Ligevægt og stabilitet

• Et toroidaltformet plasma kan være ustabilt på mange måder. De fleste af disse ”instabiliteter” er forstået teoretisk og kan kontroleres, men de sætter grænser for den maksimale plasmatæthed og det maksimale plasmatryk


Karakteristiske parametre for JET og ITER

Plasmaparametre JET ITER Power Plant

Storradius 2,96 m 6,20 m 6 – 10 m

Lilleradius 1,25 m x 2,10 m 2,0 m x 3,3 m 2 – 3,5 m

Plasmalevetid 20 s >300 s lang

Plamavolumen 150 m3 828 m3 1000 - 4000 m3

Plasma tæthed 1020 m-1 1020 1,1 - 1,4 1020

Temperatur 20 keV 20 keV 12 – 22 keV

Magnetfelt 3,4 T 5,3 T 5,5 – 7 T

Plasmastrøm 4,8 MA 15 MA 15 – 30 MA

Opvarmningseffekt 25 MW 75 MW 70 – 270 MW

Fusionseffekt 16 MW 200 - 700 MW 2,5 – 5 GW

Q-value 0,65 6 - 15 15 - 35


Måling af strøm


Rogowskispole


Strøm og spænding


Langmuir probe


Edge Te and ne: Langmuir probes

Langmuir Probes

The first diagnostic in plasma physics (1920’s)

The simplest….simply a wire inserted in the plasma!

Ion saturationcurrent density

Electron collection

DITE Tokamak

S. Pitcher, 1987


• laserlys• elektr

on• Doppler-frekvens-skift

Frekvens

IntensitetBredden giver elektrontemperaturen

Måling af elektrontemperatur v.h.a. Thomson spredning


Thomson scattering at JET


Laser-aided diagnostics: Thomson scattering

The monochromatic laser light is scattered and Doppler-shifted by the moving plasma electrons producing a broad spectrum of scattered light

Thomson scattering: exists also for divertor!


Range of measurements


Brydningsindeks for plasma

)½(),½(

af funktionerer og ,

cos4sin)(

)cos1(sin

cossin

2

:ndexBrydningsi

222422

22

22

2

LRDLRS

PLR

DPPSRLF

PSRLB

PSA

A

FBn

c

k

n


Microwave diagnostics: Electron Cyclotron Emission

ece m

eB

Magnetic field BElectron

gyrationElectron Cyclotron Emission

(ECE)

eB

ce Tkc

nI

ce 2

2

Typical Instruments:• Radiometers (JET, Tore Supra, JT-60U, DIII-D, AUG, TJ-II, TCV, TEXTOR, RTP, TEXT-U, T-

10, HT-7,…)• Michelson interferometers (TFTR, FTU, JET, DIII-D,…)


Resonances and cut-offsEceReflectometry

0

0,5

1

1,5

2

2,5

-1 -0,5 0 0,5 1

position

freq

uen

cy


Electron Cyclotron Emission => n*f(Te)


Microwave diagnostics: ECE and Te during sawteeth

1. Time traces2. Te - profiles

3. 2D-evolution

Tore Supra;

V.S. Udintsev et al., PPCF 2005


Microwave diagnostics: reflectometry

Density profiles (Tore Supra)

Principles


Microwave diagnostics: ECE-Imaging, NTM control,…

ECE-Imaging: TEXT-U, RTP, TEXTOR, AUG,…

H Park et al., RSI 75, 3787 (2004); PRL 2006

NTM Control: AUG, TEXTOR, TCV,…

N. Hicks et al., EPS 2008

ECE imaging measurements and simulations for sawtooth in TEXTOR


Laser-aided diagnostics: interferometry

Interferometry measures the line-averaged electron density by comparing the phase change of two waves, one traveling through the plasma, and another through the vacuum or air.

Several viewing chords allow obtaining the profiles across the plasma.

Can also be a mm-wave diagnostic (TCV)!

Interferometry on TEXTOR(Koslowski, Fus. Eng. Des. 1995)


Stark splitting


L1

L2BS

interference filter

L5

HD-Geissler-

tube

L4 echelle grating

f

fibre

Echelle spectrometer in Littrow arrangement

Focal length f=1 mObseravtion: 2nd orderGrating: 600 l/mmResolving Power: R>12000f=20 Hz

L5

M

CCD


Balmer spectrum

with line of sight on

the main toroidal belt limiter

Cold component

from molecules

(recycling flux)

Hot component

from CXRS etc.


Spectroscopy and particle diagnostics – CXRS

The beam neutral atoms can loose their electron to any ion of the high-temperature plasma. The getter ion then emits a series of spectral lines including visible and ultraviolet lines.

Spectroscopy of these lines enables us to measure the temperature of the getter ions from the Doppler broadening of the lines.

TCV DNBI; courtesy A. Karpushov, Ch. Schlatter, B.P. Duval

D. Thomas, FST 2008


NBI

Charge eXchange Recombination SpectroscopyPrinciple of CXRS

Dpl+ + HNBI

0 Dpl0 + HNBI

+ + hn

Lines of sights


CXRSExample of TEXTOR spectrum

- Beam density (atten.) - Localisation- Density fluctuations- B-field- MSE (q)

- H/D/T ratio- Ti bulk- Fast ions


CXRSActive beam spectroscopy of the H/D ratio

Complicated!!

E/1E/2

E/3

CII multiplet (10 Zeeman components: ADAS603)

Cold H/Dalpha features(usually overexposed)neglected in fit

Dα-PCX(Gaussian)

Dα –CX (Gaussian) initial estimate Ti usually from CVI

H coupled to D with external H/(H+D) if available


Spectroscopy and particle diagnostics – Soft X-Ray

TCV: multi-chord cameras, such as X-ray diodes, with thin Beryllium filters

Tomography reconstruction (together with modelling)

G. Turri et al., PPCF 2008V.S. Udintsev et al., PPCF 2008


Neutron and gamma


Collective Thomson ScatteringPrinciple and geometry

k

Incident radiation

Received scattered radiation

ks

kiResolved fluctuations

ReceiverProbe

CTS is based on scattering of injected microwaves on microscopic collective fluctuations in the plasma – e.g. caused by energetic ions


CTSSpectral power density

The spectral information is contained in the scattering function Σ

Example of Σ for a standard fast ion geometry at TEXTOR (kδ, B) >100˚ or <80˚

For ITER, CTS has mainly been developed as a fast ion diagnostic, enabling spatio-temporally resolved measurements of the velocity distribution of confined fast ions


Cyclotron radiation and CTS

0

0,5

1

1,5

2

2,5

3

3,5

4

4,5

5

-1 -0,8 -0,6 -0,4 -0,2 0 0,2 0,4 0,6 0,8 1

position

freq

uen

cy


CTSSensitivity to ion Bernstein waves

For geometries with (kδ, B) near 90˚ the CTS spectrum is sensitive to ion Bernstein waves


CTSSensitivity of IBW spectrum to fuel ion ratio

Model spectra for a TEXTOR H-D plasma at two different ratios


CTSFirst results of proof-of-principle diagnostic

Green: resolved angle not perpendicular

Blue: resolved angle approx 89˚

Distance between peaks is ~20 MHz – corresponding to the cyclotron frequency of Deuterium at 2.6 T


CTSPossible D/T-ratio measurements on ITER

Described in the final report of EFDA Contract 04-1213 - deliverable 4.1- D3

Derivative of the spectral power density of the CTS spectrum with respect to the fuel ion ratio for an ITER diagnostic Spectrum is sensitive to D/T-ratio

Zeff 1.82 2.37 4.60

σRi 0.146 0.151 0.138

• Possibly separate low power probe – 10 kW

• Temporal resolution of 100 ms

• Spatial resolution of a/10 across the full radius

• Uncertainty: STD ~ 0.15

• Limited influence of impurity content

• Not part of the ITER baseline design


Diganostics på JET


ITER diagnostics: practically everywhere!

C. Walker, 2008

Overblik over fusionsdiagnostikker. Poul Kerff Michelsen.

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