Determining of Radial Profile of Hydrogen Isotope Composition of TCV plasmas

Determining of Radial Profile of Hydrogen Determining of Radial Profile of Hydrogen Isotope Composition of TCV plasmasIsotope Composition of TCV plasmas

A.Karpushov, B.P.Duval, Ch.Schlatter, H.Weisen

with contribution from Laboratory of Atomic Collision Physics, Ioffe PTI

for 32nd EPS Conference on Plasma Physics,

27 June - 1 July 2005, Tarragona, Spain

Centre de Recherches en Physique des PlasmasAssociation Euratom – Confėdėration Suisse,

Lausanne, Switzerland

RS TCV, Friday, June 3, 2005

32nd EPS Conference on Plasma Physics, 27 June - 1 July 2005, Tarragona, Spain2

Introduction. Direct measurement of plasma hydrogen isotope neutral particle emission has been used to study particle transport in TCV. A Compact NPA (CNPA), with mass and energy separation has, been used to obtain information on accumulation, propagation and relaxation of hydrogen particles in a deuterium background plasma using programmed H-gas puffs. A series of thermal hydrogen gas injections into a deuterium background plasma, with a simultaneous switch-off of the main deuterium gas injection, leads to partial replacement of deuterium ions by hydrogen. A recovery algorithm has been designed to get information on the temporal behaviour of the radial hydrogen density profile. Algorithm uses the measured electron temperature and density profiles (TS), ion temperature profiles (CXRS), information on Zeff profiles and numerical modelling of neutral

density profiles and energy spectrums of neutrals escaping plasma with DOUBLE and KN1D codes.


M 410: M 410: “Effects of plasma shape on tokamak operational space and performance” “Effects of plasma shape on tokamak operational space and performance” Jaunt 414: Jaunt 414: “Ion transport”“Ion transport”p 414-1: p 414-1: “H-gas puff experiments on TCV”“H-gas puff experiments on TCV”

Method: Modulated hydrogen gas injection in deuterium plasma. Measurement of temporal variations of energy spectra of neutral hydrogen isotope fluxes: Jcx

H,D(E,t).

Reconstruction of temporal behavior of hydrogen isotope radial profiles: nH,D(). Calculation of transport parameters (DH,D,VH,D,H,D) and Analysis of their dependences on plasma parameters (ne,Te, shape) - tbd.

M414


(1) acceleration/stripping unit; (2) carbon stripping foil; (3) analysing magnet; (4) Hall probe; (5) analysing electrostatic condenser; (6) detector array; (A0) atomic flux emitted by plasma; (A+) secondary ions see http://www.ioffe.rssi.ru/ACPL/npd/npa05.htm

Compact NPA. Designed and manufactured in A.F.Ioffe Phisico-Technical Institute (St. Petersburg, Russia)

Installed on TCV in 2004Operating principles:

magneto-electric separation, E||B schemestripping in 100 Å diamond-like carbon foil

10 kG NdFeB permanent magnetelectrostatic acceleration of ions

ion focusing at the detector area Basic parameters:

two CEM arrays for detection of H and D (or D and He)H:0.64-50keV (11 channels), D:0.56-33.6keV (17 ch.)

E/E:0.6(for 0.6keV) – 0.1(for E>3keV)Operating regime:

counting with pulse amplitude discrimination Acquisition time resolution 0.5-4 msMax. count rate 800 pulse/ms

hardware


experimental scenario

A series of thermal hydrogen injection (duration of 10-100ms and period of 150-500ms) in background plasma with simultaneous switch-off main deuterium gas injection leads to partial replacement of deuterium ions by hydrogen

Plasma current, 150 kA

TS nemax: 4x1019m-3

FIR nl: 1.4x1019m-2

TS Temax: 900eV

CNPA Tieff: 400eV

Safety factor

Gas injection, mbarl/secHydrogenDeuterium 5

CNPA countrates deuterium, counts/2.5ms

CNPA countrates hydrogen, counts/2.5ms

The CNPA views the TCV plasma along horizontal view-line thought plasma axis for Zo=0


CNPA measurement

N

ttQdt

dN )(

Fitting of CNPA hydrogen countrates (N):

Q – “source”, proportional to hydrogen injection rate; – “confinement” (12-80 msec);t – “delay” (<<, 2-6 msec);

N ch.1

N ch.2

N ch.3

EE

EJEF

cxdc

)(

)()(

NPA data analysis“CX spectrum”:

)(

)()(

det EEt

ENEJ

NPA countrate (N) energy spectrum of atomic flux (J(E))

detection efficiency

dzvvEfnnSEJa

a

iaiacxiia

)()()(plasma parameters energy spectrum of atomic flux (J(E))

attenuation

“CX spectrums” for Ho and Do in TCV deuterium discharge

Following H-gas puff, count-rates in the CNPA hydrogen channels (ch.1-5: 0.6-4keV) increase by a factor of 3-4 and counting rates in deuterium channels(ch.12-20: 0.5-6keV) decrease by ~1/2.

emissivity (E,z)


DOUBLE-TCV code

0

200

400

600

800

1000

Te

,Ti,

eV

P lasma profiles for #29601 @0.75s

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 10

1

2

3

4

5x 10

19

psi

n,

m-3

ne

ni

HD

C

Te

Ti

DOUBLE-TCV: Simulation of CX fluxes emitted by tokamak plasma (Maxim Mironov, A.F.Ioffe PTI, March 2005)

The code uses the same Monte-Carlo technique to calculate neutrals distribution in plasmaAssumes that plasma is surrounded by homogenous atomic gasNeutral beam injection (NBI) included

INPUT: Plasma geometry ― poloidal flux map ((R,Z));Boundary conditions ― edge (=1) atomic neutral

density and energy (H,D,(T,He));Electron and ion density and temperature profiles

(up to 3x2 ion species, mass x temperature); Impurity Zeff and Timp profiles, atomic mass and

charge (one component ― carbon).

OUTPUT:2D distribution of total (wall+beam) neutral density

of each mass species in poloidal plane;Neutral densities along NPA view lines;Emissivity distribution for each ion component

along NPA view lines;CX spectrums for each ion component for each

view line.


DOUBLE-TCV code

DO distribution in plasma, log(no, m-3)0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

1016

1017

1018

1019

n,

m-3

Neutral density profiles for #29601 (models)

KN1D:D0

KN1D:D20

DOUBLE: H0

DOUBLE: D0

LF side

HF side

DO , HO , , D2O distribution along NPA view line

0.6 0.7 0.8 0.9 1 1.1

-0.3

-0.2

-0.1

0

0.1

0.2

0.3

R,m

Z,m

16.5

17

17.5

18

18.5

19

Neutral density profiles calculated by DOUBLE-TCV are in good agreement with KN1D simulation (slab geometry) for >0.6


DOUBLE-TCV code

500 1000 1500 2000 2500 3000 3500 4000 4500 500010

23

1024

1025

1026

1027

1028

1029

1030

1031

E, eV

Fd

cCNPA CX-spectrum for #29601 before H-puff

H exp

D exp

H mod

D mod

H and D CX-spectrums before H-puffnH/nD:[5.6-7.8]%

500 1000 1500 2000 2500 3000 3500 4000

1025

1026

1027

1028

1029

E, eV

Fd

c

H puff in #29601 @0.786 sec

005-007 ms

007-010 ms010-015 ms

015-020 ms

020-025 ms

025-030 ms030-040 ms

040-050 ms

CX-spectrums of H-ion population created by H-puff


recovery algorithm

0 0.2 0.4 0.6 0.8 10

0.5

1

1.5

2x 10

18

psi

n H,

m-3

Base functions from 'base 29601 XXX.mat'

500 1000 1500 2000 2500 3000 3500 4000 4500

1024

1026

1028

E, eV

Fd

cAssume a hydrogen density distribution as a linear combination of density base functions and build basefunctions.

i

baseiiH nkn

Dbasei nn with

nH/nD=const

nH/nD(=0)=0

nH/nD(=1)=0

i

baseiidc FkF mod

For each nibase calculates CX-spectrums (Fi

base)Model CX spectrum is a linear combination of “base CX-spectrums” with same ki

k kdc

kdckdc

EF

EFEFexp

expmod

Fond ki from minimisation of difference between “model” and “experimental” CX-spectrums

Density base functions

CX-spectrum base functions


results

CX-spectrum and density profile at 5-7 msblack – result, colours – ki “base functions”

400 600 800 1000 1200 1400 1600 1800E, eV

Fd

c

#26001 @ 5.00-7.00ms

0 0.2 0.4 0.6 0.8 10

0.5

1

1.5

2x 10

17

psi

n H,

m-3

1000 2000 3000 4000 5000 6000

1024

1026

1028

1030

E, eV

Fd

c

#26001 @ 10.00-15.00ms

0 0.2 0.4 0.6 0.8 10

1

2

3

4

5

6

7x 10

17

psi

n H,

m-3



results

500 1000 1500 2000 2500 3000 3500 4000

1026

1028

E, eV

Fd

c#26001 @ 30.00-40.00ms

0 0.2 0.4 0.6 0.8 10

1

2

3

4

5

6x 10

18

psi

n H,

m-3

500 1000 1500 2000 2500 3000 3500 4000

1026

1028

E, eV

Fd

c

#26001 @ 100.00-125.00ms

0 0.2 0.4 0.6 0.8 10

2

4

6

8

10

12

14x 10

17

psi

n H,

m-3




results

0 0.2 0.4 0.6 0.8 10

2

4

6

8x 10

18

psi

n H,

m-3

H puff in #29601 @0.786 sec

0 0.2 0.4 0.6 0.8 10

0.05

0.1

0.15

0.2

0.25

psi

n H/n

D,

m-3

H puff in #29601 @0.786 sec

005-007 ms

007-010 ms010-015 ms

015-020 ms

020-025 ms

025-030 ms030-040 ms

040-050 ms

005-007 ms

007-010 ms010-015 ms

015-020 ms

020-025 ms

025-030 ms030-040 ms

040-050 ms

500 1000 1500 2000 2500 3000 3500 4000

1025

1026

1027

1028

1029

E, eV

Fd

c

H puff in #29601 @0.786 sec

005-007 ms

007-010 ms010-015 ms

015-020 ms

020-025 ms

025-030 ms030-040 ms

040-050 ms

density profiles during H-puff CX-spectrums during H-puff

During H2-puff, the nH/nD ratio evolves from a hollow radial profile (<20ms) to a flat profile (20-25ms). After puff switch off hydrogen accumulated in internal region.


results

density profiles after H-puff CX-spectrums after H-puff

0 0.2 0.4 0.6 0.8 10

2

4

6

8x 10

18

psi

n H,

m-3

H puff in #29601 @0.786 sec

0 0.2 0.4 0.6 0.8 10

0.05

0.1

0.15

0.2

0.25

psi

n H/n

D,

m-3

H puff in #29601 @0.786 sec

040-050 ms

050-060 ms

060-070 ms

070-080 ms080-090 ms

090-100 ms

100-125 ms

040-050 ms050-060 ms

060-070 ms

070-080 ms

080-090 ms

090-100 ms100-125 ms

500 1000 1500 2000 2500 3000 3500 4000

1025

1026

1027

1028

1029

E, eV

Fd

c

H puff in #29601 @0.786 sec

040-050 ms

050-060 ms

060-070 ms

070-080 ms080-090 ms

090-100 ms

100-125 ms

With successive H-puffs, the hydrogen profile becomes peaked; hydrogen “accumulation” in internal regions takes place. “Confinement time” for low density, low current L-mode discharges was 15-25ms.


results

0 1 2 3 4 5 6 7

0

1

2

3

4

5

6

-grad(nH)/n

H, m-1

H

/nH

, m/s

# 2 9 6 0 1 VH

:-0 .3 5 m /s DH

:0 .8 3 m 2 /s for :[0 .3 5 :0 .6 5 ]

VnnD To explain H-puff results from TCV, a plasma pinch must be considered.An estimation of effective diffusion coefficient yields a value ~1m2/sec, pinch velocity is ~1m/s for dn/dt1020 m-3sec-1


results

H-puff

EE

EJEF

cxdc

)(

)()(

NPA data analysis“CX spectrum”:

1

ln)(

EFdE

dET dc

effNPA – effective NPA ion temperature

)(

)()(

det EEt

ENEJ

NPA countrate (N) energy spectrum of atomic flux (J(E))

dzvvEfnnSEJa

a

iaiacxiia

)()()(plasma parameters energy spectrum of atomic flux (J(E))

“CX spectrums” for Ho and Do in TCV deuterium discharge

Subtraction of interpolated “background” from hydrogen “CX-spectrum” allows to get temporal behavior of NPA “CX-spectrum” and ion temperature of additional hydrogen population created due to H-gas injection.

Energy spectra of additional hydrogen population relaxes to background Maxwellian CX-spectra in 10-30 ms. (Ion-Ion local thermal equilibration time < 1 ms)

hydrogen and deuterium interpolated “background”and subtracted additional hydrogen population

effective CNPA ion temperaturefor E[0.5 3.0keV],error bars ~15%

detection efficiency

attenuation


results

hydrogen injection, mbarl/sec

H, 0.64keV

H, 1.10keV

H, 1.64keV

N

ttQdt

dN )(

Fitting of CNPA hydrogen countrates (N):

Q – “source”, proportional to hydrogen injection rate; – “confinement” (12-80 msec);t – “delay” (<<, 0.3-6 msec);

Response time () of NPA counrates on H-puff increases with increase of plasma density


discussion

V I Afanasyev, A Gondhalekar, and A I Kislyakov, “On the Possibility of Determining the Radial Profile of Hydrogen Isotope Composition of JET Plasmas, and of Deducing Radial Transport of the Isotope Ions”, JET report JET–R(00)04 (Oct. 2000)

TCV result is contradictory to the observation of deuterium transport in hydrogen plasma observed on JET with short pulses of D2 gas injection (JET discharge #43446), where the nD/nH ratio

was hollow during and after gas injection. Such behaviour of radial profile of hydrogen isotope ratio probably can be explained by dependence on mass pinch velocities and ion diffusion coefficients.

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 10

0.05

0.1

0.15

0.2

0.25

psi

n H/n

D,

m-3

H puff in #29601 @0.786 sec


limitations

Analysis of H propagation in TCV plasma with high current and high density is “difficult” due to effects of sawtooth activity.

In CNPA measurement a plasma centre can not be resoled due to low NPA counting rates at high energies (>3-4keV); high is limited by a low energy limit of NPA (Ti(=1)~30eV)

“GOOD”L-mode, OHTe > 400 eV, NL<3x1019m-2

“BAD” sawtooth ELMs + H-mode X2 ECH non-Maxwellian F(E) High density

Ip:340kA, FIR nl: 3.2x1019m-2,

TS ne:5.5x1019m-3, Te=1keV


summary

1) CNPA was successfully tested as tool to measure hydrogen isotope composition.

2) A recovery algorithm of hydrogen isotope ratio radial profile from NPA measurement was developed and tested for TCV.

3) A density profiles can be recovered for TCV L-mode, low density, low current discharges.

4) Ion transport coefficients are in reasonable agreement with other observations on TCV (D~1m2/sec, V~-1m/s).

Determining of Radial Profile of Hydrogen Isotope Composition of TCV plasmas

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