Recent state and progress in negative ion modeling by means ONIX code
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Transcript of Recent state and progress in negative ion modeling by means ONIX code
Mochalskyy Serhiy NI modeling workshop, Chiba, Japan, 2013
Recent state and progress in negative ion modeling by means ONIX code
Mochalskyy Serhiy1, Dirk Wünderlich1, Benjamin Ruf1, Peter Franzen1 Ursel Fanz1 and Tiberiu Minea2
1Max-Planck-Institut fuer Plasmaphysik
EURATOM Association
Boltzmannstr. 2,D-85748 Garching
2LPGP, Univerisity Paris-Sud, CNRS
F-91405 Orsay, France
Mochalskyy Serhiy NI modeling workshop, Chiba, Japan, 2013
Outline
• Introduction
• Code improvement
• Code validation
• Code benchmarking
• Realistic parameters
• Results
• Conclusions and future plans2/32
Mochalskyy Serhiy NI modeling workshop, Chiba, Japan, 2013
Introduction: Negative ion plasma source system
Driver Expansion region Extraction region
NI surface and volume production
The goal is to produce negative ion 48A H- (40A D-) (j~20mA/cm2) beam with INI/Ie~1 at low pressure 0.6pa during continuous 1 hour operation.
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Mochalskyy Serhiy NI modeling workshop, Chiba, Japan, 2013
Introduction: ONIX (Orsay Negative Ions eXtraction) code
3D Particle-in-Cell Monte Carlo Collision electrostatic code specially developed for modeling NI production and following extraction from ITER NBI plasma source.
Fully paralellized via MPI using domain and particle decomposition techniques. Able to deal with complex geometries as in the case of the extraction aperture.
Simulation domain
19 mm
14 mm
14 mm
Plasma
grid
Extraction
grid
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Mochalskyy Serhiy NI modeling workshop, Chiba, Japan, 2013
Code improvement: Second order charge and E field assignment routine (1)
First order
Potential distribution
Second order
Potential distribution
E(x) distribution E(x) distribution
P (V)
P (V)
P (V)
P (V)
Ex (V/cm)
Ex (V/cm)Ex (V/cm)
Ex (V/cm)
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x (mm)
y (mm)
Mochalskyy Serhiy NI modeling workshop, Chiba, Japan, 2013
Code improvement: Second order charge and E field assignment routine (2)
First order Second order
E(z) distribution E(z) distribution
Ex (
E(y) distribution E(y) distribution
Ey (V/cm)
Ey (V/cm) Ey (V/cm)Ey (V/cm)
Ez (V/cm)
Ez (V/cm) Ez (V/cm)Ez (V/cm)
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x (mm)
x (mm)
y (mm)
y (mm)
Mochalskyy Serhiy NI modeling workshop, Chiba, Japan, 2013
Code improvement: NI flux from PG (1) – injection method
Trajectories of NI Flux at the given x plane
Z (
mm
)
y (m
m)
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Mochalskyy Serhiy NI modeling workshop, Chiba, Japan, 2013
Code improvement: NI flux from PG (2) – extracted electron and NI current
Extracted NI current Extracted e current
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Mochalskyy Serhiy NI modeling workshop, Chiba, Japan, 2013
Code improvement: NI flux from PG (3) – potential well in vicinity to PG
Old routine
(normal injection, 1eV)
New routine
(random injection, 1eV)
New routine
(random injection, random energy 0.01 - 1eV)
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X (mm)
PG PG PG
X (mm) X (mm)
y (
mm
)
y (
mm
)
y (
mm
)
Potential (V) Potential (V) Potential (V)
Mochalskyy Serhiy NI modeling workshop, Chiba, Japan, 2013
Code improvement: Addition to the simulation H3+ ion and H-
in the volumeH3
+ density
y (m
m)
H- from volume density Y
(m
m)
Y (
mm
)
nH3+ (m-3)Extracted electron and
NI current
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nH3+ (m-3)
PG
PG
PG
PG
Mochalskyy Serhiy NI modeling workshop, Chiba, Japan, 2013
Code validation: Potential well test in simplified model
Potential well test Potential sheath test
X (mm)
Po
ten
tia
l (V
)
X (mm)
De
ns
ity
(m
-3)
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Mochalskyy Serhiy NI modeling workshop, Chiba, Japan, 2013
0V
-5V
-10V
0V
FIG. 10. Schematic of possible steady-state plasma potential profiles near a
positively biased plate. Curve A corresponds to a large plate. Curve B corresponds
to a small plate. Noah Hershkowitzb, Phys. Of Plasma (2005) 055502
Code validation: Potential well test in simplified model (2)
Negative bias
0V
5V
10V
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Po
ten
tia
l (V
)
Po
ten
tia
l (V
)
Potential (V)
Potential (V)
x (mm)
x (mm)
Positive bias
Mochalskyy Serhiy NI modeling workshop, Chiba, Japan, 2013
Code validation: different mesh size (real domain)
Ele
ctr
on
s c
urr
en
t
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PG PG
PG
x (mm)
x (mm)
x (mm)
y (m
m)
y (m
m)
y (m
m)
Potential (V)Potential (V)
Potential (V)
Mochalskyy Serhiy NI modeling workshop, Chiba, Japan, 2013
Code benchmark: ONIX vs KOBRA3D
2 completely different codes with different approaches:
1) ONIX – uses plasma parameters (density, temperature,…) to calculate the extraction current and meniscus shape;
2) KOBRA 3D –uses the extraction current to calculate the potential and meniscus shape
PI extraction test (2 runs)
Density 0.8, 1.6,*1017 m-3 , e:100%, H+:100%; Te=2eV, TPI=1eV
Extraction potential: -5kV; B field is switch off, no collisions
PG aperture 8 mm diameter
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Mochalskyy Serhiy NI modeling workshop, Chiba, Japan, 2013
Code benchmark: ONIX vs KOBRA3D (2)
PI extraction test (4 runs)
Density 0.8, 1.6, 2.4, 3.2*1017 m-3 , e:100%, H+:100%;
Te=2eV, TPI=1eV
Extraction potential: -5kV; B field is switch off, no collisions
PG aperture 8 mm diameter and 4mm length (2mm to PG knife
and 2 mm after)
ONIX
KOBRA3D
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Mochalskyy Serhiy NI modeling workshop, Chiba, Japan, 2013
Realistic parameters: Magnetic field map
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Filter field
Deflecting field
axial x directionve
rtic
al
z d
irect
ion
Mochalskyy Serhiy NI modeling workshop, Chiba, Japan, 2013
Realistic parameters: Magnetic field map
Complete 3D magnetic field structure and thus 3D model is necessary to perform realistic simulation of NI extraction.
Filter field
Deflecting field
axial x direction
vert
ical
z
dire
ctio
n
Bx
PG
Bz
PG
PG
PG
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Mochalskyy Serhiy NI modeling workshop, Chiba, Japan, 2013
Realistic parameters: Magnetic field map
By
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Filter field
Deflecting field
axial x direction
vert
ical
z
dire
ctio
n
Mochalskyy Serhiy NI modeling workshop, Chiba, Japan, 2013
Realistic parameters: Magnetic field map
By
Bz
Bx
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Mochalskyy Serhiy NI modeling workshop, Chiba, Japan, 2013
Realistic parameters: Plasma parameters in ONIX simulations
Probe measurements
ONIX
NI emission rate
BACON
Full 3D magnetic field map
3D field simulation
Geometry of the plasma grid
Engineering specification
OES
CRDS
n=3*1017m-3
ne=90%; nNI=10%,
nH+=40%, nH2+=40%, nH3+=20%
Te=2, TH-=0.1,TH+=0.8, TH2+=0.1, TH3+=0.1 (eV)
jNI,PG=660A/m2
nH=1*1019m-3, TH=0.8eV
nH2=4*1019, TH2=0.1eV
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Mochalskyy Serhiy NI modeling workshop, Chiba, Japan, 2013
Typical evolution of extracted NI currents
NI from the surface is dominant;
NI current from the inner surface of the PG is higher than one from outer side;
Co-extracted electron current ~3.5 times higher than total NI current in no PG bias test.
Conical PG surface
flat PG surface PG
ONIX results BATMAN results
(no PG bias)
29.16~ cmmAjNI
15.4~ NIe II 3~NIe II
214~ cmmAjNI
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Mochalskyy Serhiy NI modeling workshop, Chiba, Japan, 2013
Results: Limitation of the NI extraction
Potential distributionin vicinity to PG
PG
Potential (V)
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x (mm)
y (m
m)
Mochalskyy Serhiy NI modeling workshop, Chiba, Japan, 2013
Results: Potential at the wall
Emission rate ~250A/m2 (~-3V)
Emission rate ~800A/m2 (~-13V)
Emission rate ~2000A/m2 (~-20V)
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x (mm)
PG
PG
x (mm)y
(m
m)
y (
mm
)
Potential (V)
Potential (V)
Mochalskyy Serhiy NI modeling workshop, Chiba, Japan, 2013
Limitation of the NI extraction
NI density produced from the conical surface of PG
NI density produced from the flat surface of PG
NI density produced at the volume
Results:
Total NI density along domain
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x (mm)
x (mm) x (mm)
x (mm)
y (m
m)
y (m
m)
y (m
m)
y (m
m)
Density (m-3)
Density (m-3)
Density (m-3)
Density (m-3)
PG
PG
PG
PG
PG
PG
Mochalskyy Serhiy NI modeling workshop, Chiba, Japan, 2013
Results: Ion –Ion plasma calculation (NI current)
No B field With B field
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z ve
rtic
al d
irec
tion
z ve
rtic
al d
irec
tion
y horizontal direction y horizontal direction
curr
ent
(mA
)
curr
ent
(mA
)
Mochalskyy Serhiy NI modeling workshop, Chiba, Japan, 2013
Results: Ion –Ion plasma calculation (NI density distribution)
No B field With B field
x (mm) x (mm)
x (mm) x (mm)
y (
mm
)y
(m
m)
y (
mm
)y
(m
m)
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Density (m-3)
Density (m-3)Density (m-3)
Density (m-3)
Mochalskyy Serhiy NI modeling workshop, Chiba, Japan, 2013
Results: Ion –Ion plasma calculation (e current)
No B field With B field
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z ve
rtic
al d
irec
tion
y horizontal direction
z ve
rtic
al d
irec
tion
y horizontal direction
curr
ent
(mA
)
curr
ent
(mA
)
Mochalskyy Serhiy NI modeling workshop, Chiba, Japan, 2013
Results: Ion –Ion plasma calculation (e density distribution)
No B field With B field
x (mm) x (mm)
y (
mm
)
y (
mm
)
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Density (m-3) Density (m-3)
Mochalskyy Serhiy NI modeling workshop, Chiba, Japan, 2013
Results: Ion –Ion plasma calculation (H+ density distribution - meniscus)
No B field With B field
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x (mm) x (mm)
y (m
m)
y (m
m)
Density (m-3)Density (m-3)
Mochalskyy Serhiy NI modeling workshop, Chiba, Japan, 2013
Results: Ion-ion plasma simulations (5 runs)
e current densityNI current density
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Mochalskyy Serhiy NI modeling workshop, Chiba, Japan, 2013
Results: Meniscus shape for several ion-ion plasmas (5 runs)
H+ density95:5=e:NI (%)
75:25
50:50
25:75
5:95
PG
PG
PG
PG
PG
PG
PG
PG
PG
PG
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Mochalskyy Serhiy NI modeling workshop, Chiba, Japan, 2013
Thank you for your attention
Project is supported by
the Alexander von Humboldt foundation
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