Diagnostic of the plasma-wall transition region in a ... Fusion Research... · Electrical...
Transcript of Diagnostic of the plasma-wall transition region in a ... Fusion Research... · Electrical...
Diagnostic of the plasma-wall transitionregion in a divertor-like system
G. Popa, C. Costin, S. Teodoru, C. Lupu,V. Anita, M. Solomon, C. Agheorghiesei
Faculty of Physics, “Al. I. Cuza” University IasiAssociation EURATOM - MEdC
FOM Institute for Plasma Physics “Rijnhuizen”, The Netherlands, Association EURATOM-FOM
Theoretical Plasma Physics Group & Department for Ion Physics, Innsbruck University, Austria, Association EURATOM-ÖAW
Castor Tokamak, Institute of Plasma Physics, Prague, Czech Republic, Association EURATOM/IPP.CR
Collaborations
Achievements
Numerical modelling for PILOT-PSI
2D fluid model
PIC model
Electrical diagnostic of PILOT-PSI plasma beam
Future plans
Evolution of the charged space sheath
Secondary electron emission induced by electron bombardment
Probe plasma diagnostic on Castor Tokamak
Multi-channel analyser (MCA). Experiments on PILOT-PSI
Evolution of the charged space sheath
Evolution of the charged space sheath
Time evolution of the collector potential for different values of the angle θbetween the magnetic field and the normal direction to the wall surface
-70
-60
-50
-40
-30
-20
-10
0
10
θ = 90 [ deg ]θ = 70 [ deg ]
θ = 30 [ deg ]V
[ V
]θ = 10 [ deg ]
0.00 1.50x10-10 3.00x10-10 4.50x10-10 6.00x10-10-60
-50
-40
-30
-20
-10
0
V [ V
]
t [ s ]0.00 1.50x10-10 3.00x10-10 4.50x10-10 6.00x10-10
t [ s ]
Evolution of the charged space sheath
Spectrum of the potential oscillations at the collector for (a) constant B = 1T and different θ,(b) constant θ = 30° and different B
Secondary electron emission induced by electron bombardment
Measured current-voltage characteristics
-800 -600 -400 -200 0
-12
-6
0
ni = 4.313*1017m-3 nf/ni = 3.98*10-4
Te= Ti= 20 eV Tf= 10 eV Esh= 500 eV
Vp(V)
simulation without SEE simulation with SEE theory
j (10
2 A/m
2 )
Current-voltage characteristic for Deuteriumplasma, simulation (1D-PIC) and theory
Probe plasma diagnostic on Castor TokamakMeasurements of the diffusion coefficient
Katsumata probe – schematic representation
Castor Tokamak: R = 40 cm, a = 8.5 cm, B = 1.2 T and Ip =10 kA
Probe plasma diagnostic on Castor TokamakMeasurements of the diffusion coefficient
Fluctuation power spectra for different collector position h [mm] (r = 65 mm)
Probe plasma diagnostic on Castor TokamakMeasurements of the diffusion coefficient
Radial decay of the spectrumat different frequencies
Dependence of 1/L2 on the frequency
2
14Df
Lπ=
Probe plasma diagnostic on Castor TokamakMeasurements of the diffusion coefficient
Radial profile of the measured diffusion coefficient (black points) and of the Bohm one (red line)
Probe plasma diagnostic on Castor TokamakIon temperature measurements by Katsumata probe
I-V characteristic of the collector;linear scale (top) and logarithmic scale (bottom)
(h = -0.5 mm, r = 80 mm)
Probe plasma diagnostic on Castor TokamakIon temperature measurements by Katsumata probe
Radial profile of the Ti for two positionsof the collector h = -0.5 and -0.3 mm
Ion temperature measured with Katsumata and Tunnel probe
Multi-Channel Analyser (MCA)
B
dp = 10 mm dc1 = 0.9 mmdc2 = 0.6 mmdc3 = 0.3 mm
PILOT-PSI device
PILOT-PSI MCA measurements
0.1 0.2 0.3 0.4 0.5
10-4
10-3
10-2
10-1
H2, Ti = 2 eV H2, Ti = 4 eV Ar, Ti = 2 eV Ar, Ti = 4 eV H2 exp H2+Ar exp Ar exp
f = I/
I 0
R (mm)
2 2 2 2 2
2(1 )1 2
8 (1 sin )
0 0 0
1 1i
i i
q B R xkT m xIf e xdxd
I
πϕ ϕ
π⊥
−−
−⎡ ⎤⎢ ⎥= = −⎢ ⎥⎣ ⎦
∫ ∫
Fraction f of the collected current versus channel radius R
theory
experiment
-30 -20 -10
-800
-600
-400
-200
Ar, Isource = 80 A, B = 0.4 T
I plat
e (m
A)
Uplate (V)
-250 -200 -150 -100 -50
-300
-200
-100
H2, Qv=1 l/min, Vf = -11,2 V, VfB = - 79 V
I plat
e (μA
, mA)
Uplate (V)
B = 0.0 T, I (μA) B = 0.4 T, I (mA)
Current-voltage characteristics of MCA plate
PILOT-PSI measurements
-40 -30 -20 -10 10 20 30 40-20
20
40
60
80
100
120
Ar, Isource = 90 A, B = 0.4 T, p = 0.03 mbar
I targ
et (A
)
Utarget (V)
-40 -30 -20 -10
-40
-30
-20
-10
Ar, B = 0.4 T, p = 0.03 mbar
I targ
et (A
)
Utarget (V)
I = 90 A I = 120 A I = 150 A
Current-voltage characteristics of the target (Carbon)
Publications [1] R. Schrittwieser, C. Ionita, J. Adamek, J. Stockel, J. Brotankova, E. Martines, G. Popa, C. Costin, L. van de Peppel and G. van Oost, “Direct measurements of the plasma potential by katsumata-type probes”, Czech. J. of Phys. 56 (2006), Suppl. B, pp B145 – B 150
[2] J. Brotankova, J. Adamek, J. Stockel, E. Martines, G. Popa, C. Costin, R. Schrittwieser, C. Ionita, G. van Oost and L. van de Peppel, “A probe-based method for measuring the transport coefficient in the tokamak edge region”, Czech. J. of Phys. 56 (2006), pp. 1321–1328
[1] C. Costin, L. Grigoras and G. Popa, “Multi-channel analyser and perpendicular ion energy distribution in magnetised plasma”, 33rd European Physical Society (EPS) Conference on Controlled Fusion and Plasma Physics, 19-23 June 2006, Rome, Italy (poster)
[2] J. Brotankova, E. Martines, J. Adamek, J. Stockel, G. Popa and C. Costin, “A new-probe based method for measuring the diffusion coefficient in the tokamak edge region”, 33rd European Physical Society (EPS) Conference on Controlled Fusion and Plasma Physics, 19-23 June 2006, Rome, Italy (poster)
[3] R. Schrittwieser, J. Adamek, C. Ionita, J. Stockel, E. Martines, J. Brotankova, C. Costin, G. Popa, G. van Oost and L. van de Peppel, “Direct measurements of the plasma potential by Katsumata-type probes”, 33rd European Physical Society (EPS) Conference on Controlled Fusion and Plasma Physics, 19-23 June 2006, Rome, Italy (poster)
[4] C. Lupu, D. D. Tskhakaya sr., S. Kuhn, D. Tskhakaya jr. and G. Popa, “Floating sheath formation in a collisional magnetised plasma”,33rd European Physical Society (EPS) Conference on Controlled Fusion and Plasma Physics, 19-23 June 2006, Rome, Italy (poster)
[5] J. Adamek, J. Stockel, R. Panek, M. Kokan, E. Martines, R. Schrittwieser, C. Ionita, G. Popa, C. Costin, J. Brotankova, G. van Oostand L. van de Peppel, “Simultaneous measurements of the parallel and perpendicular ion temperature by Katsumata and segmented tunnel probe”, 9th Workshop on the Electric Fields, Structures and Relaxation in Edge Plasma, 26-27 June 2006, Rome, Italy (oral presentation)
[6] J. Brotankova, E. Martines, J. Adamek, J. Stockel, G. Popa, C. Costin, R. Schrittwieser, C. Ionita and G. van Oost, “A probe-based method for measuring the transport coefficient in the tokamak edge region”, 9th Workshop on the Electric Fields, Structures and Relaxation in Edge Plasma, 26-27 June 2006, Rome, Italy (oral presentation)
Conferences
Future plans
Numerical modelling for PILOT-PSI
2D fluid model
PIC model
Electrical diagnostic of PILOT-PSI plasma beam
Numerical modelling for PILOT-PSI
Scheme of the device
Numerical modelling for PILOT-PSI
( ) , ,ss s iz e
n n v f n s e it
∂+∇⋅ = =
∂
ur
( ) ( )ss s s s s s s s
vm n v v q n E v B Pt
⎡ ⎤∂+ ⋅∇ = + × −∇ −⎢ ⎥∂⎣ ⎦
urur ur ur ur ur
1 e izs s ms s
s ms
n fm n f vn f
⎛ ⎞+⎜ ⎟
⎝ ⎠
ur
( ) ( )e ee e e e e e
n n v E ntε ε θ∂
+∇ ⋅ = −Γ ⋅ −∂
ur uur ur
2D Fluid model
( ) /ee e e e e e e e e men v n E D n n v fμΓ = = − −∇ − ×Ωuur ur ur ur ur
eff
i i i i i i in v n E D nμΓ = = − ∇uur ur ur
( )eff
eff e imi iz
i i i
nE f E E ft n n μ
Γ∂= − −
∂
uururur ur
Numerical modelling for PILOT-PSI
Particle fluxes
Poisson equation
0
( )i ee n nVε−
Δ = −
12e e en v⊥Γ = < >
14
effi i thi i in v n Eδμ⊥ ⊥Γ = +
|| 0 , ,s s e i nΓ = =12e e e en vε ε⊥Γ = < >
|| 0eεΓ =
Numerical modelling for PILOT-PSI
Boundary conditions
walls
source
target secondary electron emission is consideredimposed V
0n⊥Γ =
, ,simposed s e i n and V⊥Γ =
0V =
Electrical diagnostic of PILOT-PSI plasma beam
- Langmuir probe (self-emissive probe)- emissive probe
Electrical diagnostic of PILOT-PSI plasma beam
I-V characteristics of a self-emissive probein a magnetron discharge
Electrical diagnostic of PILOT-PSI plasma beam
- Multi-channel end-plate
Thank you for your attention!
Assumptions: -Only the ions enter into the channels, the electrons are rejected.-2R < the sheath thickness formed in front of the MCA ~ a few Debyelengths.
Example:-Hydrogen plasma, n0 = 1021 m-3, Te = 2 eV, Ti = 4 eV (working conditions for Pilot) Debye length is ~ 0.3 μm.-B = 1 T ion Larmor radius ~ 0.3 mm.
MCA + grid
-Hydrogen plasma, Te = 2 eV, Ti = 4 eV, R = 0.15 ÷ 0.45 mm Debye length ~ 0.1 mm n0 ≤ 1016 m-3.
-B = 0.4 T ion Larmor radius ~ 0.7 mm.
Multi-Channel Analyser (MCA)