cips sewg fr, jet 2008c. hopf o 2 /he glow discharge cleaning: experience at ipp christian hopf,...
TRANSCRIPT
![Page 1: CIPS SEWG FR, JET 2008C. Hopf O 2 /He glow discharge cleaning: Experience at IPP Christian Hopf, Volker Rohde, Wolfgang Jacob Max-Planck-Institut für Plasmaphysik](https://reader035.vdocument.in/reader035/viewer/2022070305/5514e624550346935c8b589d/html5/thumbnails/1.jpg)
CIPS
SEWG FR, JET 2008C. Hopf
O2/He glow discharge cleaning: Experience at IPP
Christian Hopf, Volker Rohde, Wolfgang Jacob
Max-Planck-Institut für Plasmaphysik
![Page 2: CIPS SEWG FR, JET 2008C. Hopf O 2 /He glow discharge cleaning: Experience at IPP Christian Hopf, Volker Rohde, Wolfgang Jacob Max-Planck-Institut für Plasmaphysik](https://reader035.vdocument.in/reader035/viewer/2022070305/5514e624550346935c8b589d/html5/thumbnails/2.jpg)
CIPS
SEWG FR, JET 2008C. Hopf
Experience at IPP
ASDEX Upgrade (2005)
He/O2 DC glow discharge
5.4 A, ca. 600 V
2% O2 + 98% He
6 x 10-3 mbar
49 h total O2/He glow time
AUG + laboratory experiments:
(E) Efficiency of He/O2 mixtures as function of the mixture ratio
(A) Accessible locations
(B) Effect of boron in carbon redeposits
(C) Collateral damage: Physical sputtering of various materials and oxidation of tungsten
![Page 3: CIPS SEWG FR, JET 2008C. Hopf O 2 /He glow discharge cleaning: Experience at IPP Christian Hopf, Volker Rohde, Wolfgang Jacob Max-Planck-Institut für Plasmaphysik](https://reader035.vdocument.in/reader035/viewer/2022070305/5514e624550346935c8b589d/html5/thumbnails/3.jpg)
CIPS
SEWG FR, JET 2008C. Hopf
(E) Efficiency of He/O2 mixtures
![Page 4: CIPS SEWG FR, JET 2008C. Hopf O 2 /He glow discharge cleaning: Experience at IPP Christian Hopf, Volker Rohde, Wolfgang Jacob Max-Planck-Institut für Plasmaphysik](https://reader035.vdocument.in/reader035/viewer/2022070305/5514e624550346935c8b589d/html5/thumbnails/4.jpg)
CIPS
SEWG FR, JET 2008C. Hopf
(E) Why He/O2 mixtures?
Use of He/O2 mixtures rather than pure O2 because
• of safety hazards (oil-sealed rotary pumps, dust).
• He has lower physical sputtering yields.
• pure O2 DC glow discharges are hard to ignite/sustain.
→ How does the erosion rate depend on the mixture ratio?
![Page 5: CIPS SEWG FR, JET 2008C. Hopf O 2 /He glow discharge cleaning: Experience at IPP Christian Hopf, Volker Rohde, Wolfgang Jacob Max-Planck-Institut für Plasmaphysik](https://reader035.vdocument.in/reader035/viewer/2022070305/5514e624550346935c8b589d/html5/thumbnails/5.jpg)
CIPS
SEWG FR, JET 2008C. Hopf
(E) Mass spectrometry during discharge in AUG
0.0 0.5 1.0 1.5 2.00.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
sig
na
l (1
0-5
A)
O2/(O2 + He) (%)
mass 32 28 44
0 2 4 60.0
0.5
1.0
1.5
sig
na
l (1
0-5
A)
discharge current (A)
mass 32 28 44
I = 5.4 A O2/(O2+He) = 0.6 %
erosion limited by ion flux density, not O2 supply
![Page 6: CIPS SEWG FR, JET 2008C. Hopf O 2 /He glow discharge cleaning: Experience at IPP Christian Hopf, Volker Rohde, Wolfgang Jacob Max-Planck-Institut für Plasmaphysik](https://reader035.vdocument.in/reader035/viewer/2022070305/5514e624550346935c8b589d/html5/thumbnails/6.jpg)
CIPS
SEWG FR, JET 2008C. Hopf
(E) Dependence of rate on O2/(He + O2) ratio
0 20 40 60 80 1000.01
0.1
1
ero
sio
n r
ate
(n
m/s
)
R = O2 / (O2
+ He) (%)
hard a-C:H soft a-C:H
Rate saturation already at 10 % O2
ECR He/O2 discharge
Substrate bias: - 400 VPower constant: 150 WTotal pressure constant: 0.5 PaO2/He ratio changed
![Page 7: CIPS SEWG FR, JET 2008C. Hopf O 2 /He glow discharge cleaning: Experience at IPP Christian Hopf, Volker Rohde, Wolfgang Jacob Max-Planck-Institut für Plasmaphysik](https://reader035.vdocument.in/reader035/viewer/2022070305/5514e624550346935c8b589d/html5/thumbnails/7.jpg)
CIPS
SEWG FR, JET 2008C. Hopf
(E) Ion + O2 synergism
Particle beam experiment:
Ar+ (20 to 800 eV) plus thermal O2 (background gas)
200 400 600 8000
5
10
15
20
0
2x1013
4x1013
6x1013
8x1013
Ar++O2
800 eV 400 eV 200 eV 100 eV 50 eV 20 eV
only O2yiel
d (C
/ A
r+)
temperature (K)
rate
(cm
-2 s
-1)
10 100 10000.1
1
10
1012
1013
1014
O2 at 800 K
800 K150 K300 K
yiel
d (
C /
Ar+
)
energy (eV)
rate
(cm
-2s-1
)
C. Hopf,a M. Schlüter, and W. Jacob, Appl. Phys. Lett. 90 (2007) 224106C. Hopf, M. Schlüter, T. Schwarz-Selinger, and W. Jacob, New. J. Phys., submitted
![Page 8: CIPS SEWG FR, JET 2008C. Hopf O 2 /He glow discharge cleaning: Experience at IPP Christian Hopf, Volker Rohde, Wolfgang Jacob Max-Planck-Institut für Plasmaphysik](https://reader035.vdocument.in/reader035/viewer/2022070305/5514e624550346935c8b589d/html5/thumbnails/8.jpg)
CIPS
SEWG FR, JET 2008C. Hopf
(E) Ion + O2 synergism
0 1 10 100 1000 100000
1
2
3
4
5
0
1x1013
2x1013
400 eV Ar+ + O2 --> a-C:H
T = 300 Kjion = 4 x 1012 cm-2 s-1
yiel
d (C
/ A
r+)
R = jO2/ jAr+
rate
(cm
-2 s
-1)
Ar+ + O2: O2 flux dependence
![Page 9: CIPS SEWG FR, JET 2008C. Hopf O 2 /He glow discharge cleaning: Experience at IPP Christian Hopf, Volker Rohde, Wolfgang Jacob Max-Planck-Institut für Plasmaphysik](https://reader035.vdocument.in/reader035/viewer/2022070305/5514e624550346935c8b589d/html5/thumbnails/9.jpg)
CIPS
SEWG FR, JET 2008C. Hopf
(E) Rate Saturation
Saturation at
Ion energy
jion (cm-2 s-1) p (Pa) jO2 (cm-2 s-1) % O2
AUG 300 eV 1 1014 0.6 < 7 1015 < 0.5
ECR 400 eV 5 1015 0.5 1.2 1017 10
The required oxygen flux densityscales roughly
like the ion (energy) flux density.
![Page 10: CIPS SEWG FR, JET 2008C. Hopf O 2 /He glow discharge cleaning: Experience at IPP Christian Hopf, Volker Rohde, Wolfgang Jacob Max-Planck-Institut für Plasmaphysik](https://reader035.vdocument.in/reader035/viewer/2022070305/5514e624550346935c8b589d/html5/thumbnails/10.jpg)
CIPS
SEWG FR, JET 2008C. Hopf
(A) Accessible Locations
![Page 11: CIPS SEWG FR, JET 2008C. Hopf O 2 /He glow discharge cleaning: Experience at IPP Christian Hopf, Volker Rohde, Wolfgang Jacob Max-Planck-Institut für Plasmaphysik](https://reader035.vdocument.in/reader035/viewer/2022070305/5514e624550346935c8b589d/html5/thumbnails/11.jpg)
CIPS
SEWG FR, JET 2008C. Hopf
(A) a-C:H samples in AUG
sectors 6, 7, 8 sectors 3, 11, 15
C removedNo C removed
Glow discharge
accesses large surface area
does not access shielded places, such as tile gaps, behind first wall, and deep in the divertor
See T. Schwarz-Selinger, tile gap experients
![Page 12: CIPS SEWG FR, JET 2008C. Hopf O 2 /He glow discharge cleaning: Experience at IPP Christian Hopf, Volker Rohde, Wolfgang Jacob Max-Planck-Institut für Plasmaphysik](https://reader035.vdocument.in/reader035/viewer/2022070305/5514e624550346935c8b589d/html5/thumbnails/12.jpg)
CIPS
SEWG FR, JET 2008C. Hopf
(B) Effect of Boron in Redeposited Layers
![Page 13: CIPS SEWG FR, JET 2008C. Hopf O 2 /He glow discharge cleaning: Experience at IPP Christian Hopf, Volker Rohde, Wolfgang Jacob Max-Planck-Institut für Plasmaphysik](https://reader035.vdocument.in/reader035/viewer/2022070305/5514e624550346935c8b589d/html5/thumbnails/13.jpg)
CIPS
SEWG FR, JET 2008C. Hopf
(B) “Real layers”
a-C:H → Tokamak redeposits
Laboratory glow discharge:
Layer removed
AUG:
No signs of erosion
Ion beam analysis of 2005 layers:
Dominated by boron
B/C >> 1
![Page 14: CIPS SEWG FR, JET 2008C. Hopf O 2 /He glow discharge cleaning: Experience at IPP Christian Hopf, Volker Rohde, Wolfgang Jacob Max-Planck-Institut für Plasmaphysik](https://reader035.vdocument.in/reader035/viewer/2022070305/5514e624550346935c8b589d/html5/thumbnails/14.jpg)
CIPS
SEWG FR, JET 2008C. Hopf
(B) Effect of boron on a-C:H erosion
0.0 0.2 0.4 0.6 0.8 1.0
1013
1014
1015
1016
B + C
rem
oval
rat
e (a
tom
s cm
-2 s
-1)
B / (C+B)
a-B:C:H films (varying B content)
ECR oxygen discharge
RF substrate bias -60 eV
![Page 15: CIPS SEWG FR, JET 2008C. Hopf O 2 /He glow discharge cleaning: Experience at IPP Christian Hopf, Volker Rohde, Wolfgang Jacob Max-Planck-Institut für Plasmaphysik](https://reader035.vdocument.in/reader035/viewer/2022070305/5514e624550346935c8b589d/html5/thumbnails/15.jpg)
CIPS
SEWG FR, JET 2008C. Hopf
(B) Effect of boron on a-C:H erosion
0.0 0.2 0.4 0.6 0.8 1.0
1013
1014
1015
1016
B + C
rem
oval
rat
e (a
tom
s cm
-2 s
-1)
B / (C+B)
a-B:C:H films (varying B content)
ECR oxygen discharge
RF substrate bias -60 eV
Erosion rate drops by factor of 50.
20 % B → factor 10 reduction
![Page 16: CIPS SEWG FR, JET 2008C. Hopf O 2 /He glow discharge cleaning: Experience at IPP Christian Hopf, Volker Rohde, Wolfgang Jacob Max-Planck-Institut für Plasmaphysik](https://reader035.vdocument.in/reader035/viewer/2022070305/5514e624550346935c8b589d/html5/thumbnails/16.jpg)
CIPS
SEWG FR, JET 2008C. Hopf
(B) Effect of boron on a-C:H erosion
0.0 0.2 0.4 0.6 0.8 1.0
1013
1014
1015
1016
B + C B C
rem
oval
rat
e (a
tom
s cm
-2 s
-1)
B / (C+B)
a-B:C:H films (varying B content)
ECR oxygen discharge
RF substrate bias -60 eV
Erosion rate drops by factor of 40.
20 % B → factor 10 reduction
![Page 17: CIPS SEWG FR, JET 2008C. Hopf O 2 /He glow discharge cleaning: Experience at IPP Christian Hopf, Volker Rohde, Wolfgang Jacob Max-Planck-Institut für Plasmaphysik](https://reader035.vdocument.in/reader035/viewer/2022070305/5514e624550346935c8b589d/html5/thumbnails/17.jpg)
CIPS
SEWG FR, JET 2008C. Hopf
(B) Effect of boron on a-C:H erosion
0.0 0.2 0.4 0.6 0.8 1.0
1013
1014
1015
1016
B + C B C
rem
oval
rat
e (a
tom
s cm
-2 s
-1)
B / (C+B)
a-B:C:H films (varying B content)
ECR oxygen discharge
RF substrate bias -60 V
Boron erosion rate constant:
• Enrichment of boron at surface
• B eroded by physical sputtering
• Carbon eroded according to stoichiometry
Erosion rate drops by factor of 40.
20 % B → factor 10 reduction
![Page 18: CIPS SEWG FR, JET 2008C. Hopf O 2 /He glow discharge cleaning: Experience at IPP Christian Hopf, Volker Rohde, Wolfgang Jacob Max-Planck-Institut für Plasmaphysik](https://reader035.vdocument.in/reader035/viewer/2022070305/5514e624550346935c8b589d/html5/thumbnails/18.jpg)
CIPS
SEWG FR, JET 2008C. Hopf
(B) Arcing during DC glow discharge
Layers’ conductivity decreased during venting prior to AUG GDC cleaning.
Surface charged positively. → Local arcs burnt holes through layer, tungsten, and graphite.
No energetic ion bombardment on major parts of the films.→ Main reason for finding no erosion of the layers.
![Page 19: CIPS SEWG FR, JET 2008C. Hopf O 2 /He glow discharge cleaning: Experience at IPP Christian Hopf, Volker Rohde, Wolfgang Jacob Max-Planck-Institut für Plasmaphysik](https://reader035.vdocument.in/reader035/viewer/2022070305/5514e624550346935c8b589d/html5/thumbnails/19.jpg)
CIPS
SEWG FR, JET 2008C. Hopf
(B)
Conclusion:
High B concentrations in AUG layers would have significantlyreduced their erosion rates
but
as they had become insulating they experienced no energetic ion flux
and were not eroded at all.
![Page 20: CIPS SEWG FR, JET 2008C. Hopf O 2 /He glow discharge cleaning: Experience at IPP Christian Hopf, Volker Rohde, Wolfgang Jacob Max-Planck-Institut für Plasmaphysik](https://reader035.vdocument.in/reader035/viewer/2022070305/5514e624550346935c8b589d/html5/thumbnails/20.jpg)
CIPS
SEWG FR, JET 2008C. Hopf
(C) Collateral Damage
![Page 21: CIPS SEWG FR, JET 2008C. Hopf O 2 /He glow discharge cleaning: Experience at IPP Christian Hopf, Volker Rohde, Wolfgang Jacob Max-Planck-Institut für Plasmaphysik](https://reader035.vdocument.in/reader035/viewer/2022070305/5514e624550346935c8b589d/html5/thumbnails/21.jpg)
CIPS
SEWG FR, JET 2008C. Hopf
(C) Sputtering of C, Al, Fe, and W by He+ and O+
10 100 1000 1000010-4
10-3
10-2
10-1
100
O on Al (this work) He on Al (Eckstein, Bohdansky) He on Al2O3 (Eckstein, Bohdansky)
O on Al, TRIM.SP (this work) He on Al, TRIM.SP (Eckstein)
sput
terin
g yi
eld
energy (eV)
Target: Al and Al2O3
100 1000 1000010-3
10-2
10-1
100
sput
terin
g yi
eld
energy (eV)
O on C (Hechtl, Eckstein) He on C (Eckstein) O on C, TRIM.SP (this work) He on C, TRIM.SP (Eckstein)
Target: graphite
100 1000 1000010-3
10-2
10-1
100
sput
terin
g yi
eld
energy (eV)
He on Fe (Eckstein) O on Fe, TRIM.SP (this work) He on Fe, TRIM.SP (Eckstein)
Target: Fe
100 1000 1000010-4
10-3
10-2
10-1
100
sput
terin
g yi
eld
energy (eV)
O on W (Hechtl, Eckstein) O on W (this work) He on W (Eckstein) O on W, TRIM.SP (Eckstein) He on W, TRIM.SP (Eckstein)
Target: W
Reactivity of oxygen can
increase (carbon)
or
decrease (Al, W)
the sputtering yield.
![Page 22: CIPS SEWG FR, JET 2008C. Hopf O 2 /He glow discharge cleaning: Experience at IPP Christian Hopf, Volker Rohde, Wolfgang Jacob Max-Planck-Institut für Plasmaphysik](https://reader035.vdocument.in/reader035/viewer/2022070305/5514e624550346935c8b589d/html5/thumbnails/22.jpg)
CIPS
SEWG FR, JET 2008C. Hopf
(C) Collateral damage: Selectivity
Erosion yields for 300 eV ion bombardment:
to be compared to a yield of 1 C/ion for a-C:H or 0.1 C/ion for B-impurified films
Selectivity: Keep ion energy low!
![Page 23: CIPS SEWG FR, JET 2008C. Hopf O 2 /He glow discharge cleaning: Experience at IPP Christian Hopf, Volker Rohde, Wolfgang Jacob Max-Planck-Institut für Plasmaphysik](https://reader035.vdocument.in/reader035/viewer/2022070305/5514e624550346935c8b589d/html5/thumbnails/23.jpg)
CIPS
SEWG FR, JET 2008C. Hopf
(C) Redeposition of sputtered metals
O2/He DC GDC in stainless steel vessel:
Analysis (chemical, XRF, XPS): Fe, Cr, Ni, O → redeposited and oxidized SS
![Page 24: CIPS SEWG FR, JET 2008C. Hopf O 2 /He glow discharge cleaning: Experience at IPP Christian Hopf, Volker Rohde, Wolfgang Jacob Max-Planck-Institut für Plasmaphysik](https://reader035.vdocument.in/reader035/viewer/2022070305/5514e624550346935c8b589d/html5/thumbnails/24.jpg)
CIPS
SEWG FR, JET 2008C. Hopf
(C) Collateral damage II: Oxidation of W
0 20 40 60 800
1
2
3
4
5
6
7
8
polished solid W W coatings
10
16 O
/ c
m2
exposure time (min)
28 min H2
after 17 min O2
O2 plasma -200 V
0 50 100 150 200 2500
10
20
30
40
50
60
10
16 O
/ c
m2
exposure time (min)
O2 plasma -400 V
H2 plasma -400 V
Oxidation of W saturates
Rapid oxygen removal in H discharge
![Page 25: CIPS SEWG FR, JET 2008C. Hopf O 2 /He glow discharge cleaning: Experience at IPP Christian Hopf, Volker Rohde, Wolfgang Jacob Max-Planck-Institut für Plasmaphysik](https://reader035.vdocument.in/reader035/viewer/2022070305/5514e624550346935c8b589d/html5/thumbnails/25.jpg)
CIPS
SEWG FR, JET 2008C. Hopf
Summary
• Accessible locations: Critical issue: gaps
• O2/He mixtures: Required oxygen concentrations depend on ion energy flux density (understood by modelling)Typically 1–10% O2 required
• Effect of impurities:Boron: Huge reduction of erosion rate even at low concentrationsOther impurities that do not form volatile oxides:Experiments under well defined laboratory conditions needed
• Collateral damage: Selectivity: Keep ion energy low (problem for DC discharges)Oxidation: rapidly reversible, no problems reported after tokamak experiments
![Page 26: CIPS SEWG FR, JET 2008C. Hopf O 2 /He glow discharge cleaning: Experience at IPP Christian Hopf, Volker Rohde, Wolfgang Jacob Max-Planck-Institut für Plasmaphysik](https://reader035.vdocument.in/reader035/viewer/2022070305/5514e624550346935c8b589d/html5/thumbnails/26.jpg)
CIPS
SEWG FR, JET 2008C. Hopf
![Page 27: CIPS SEWG FR, JET 2008C. Hopf O 2 /He glow discharge cleaning: Experience at IPP Christian Hopf, Volker Rohde, Wolfgang Jacob Max-Planck-Institut für Plasmaphysik](https://reader035.vdocument.in/reader035/viewer/2022070305/5514e624550346935c8b589d/html5/thumbnails/27.jpg)
CIPS
SEWG FR, JET 2008C. Hopf
(E) Ion + O2 synergism
1013 1014 1015 1016 1017 10181012
1013
1014
1015
1016
1017T = 400 KE = 300 eVHe+ + O2
jion = 1 x 1013
jion = 1 x 1014
jion = 1 x 1015
jion = 1 x 1016
eros
ion
rate
(cm
-2 s
-1)
O2 flux density (cm-2 s-1)
jion = 1 x 1017
![Page 28: CIPS SEWG FR, JET 2008C. Hopf O 2 /He glow discharge cleaning: Experience at IPP Christian Hopf, Volker Rohde, Wolfgang Jacob Max-Planck-Institut für Plasmaphysik](https://reader035.vdocument.in/reader035/viewer/2022070305/5514e624550346935c8b589d/html5/thumbnails/28.jpg)
CIPS
SEWG FR, JET 2008C. Hopf
(E) Ion + O2 synergism
1013 1014 1015 1016 1017 1018 1019 1020 1021 1022 10231012
1013
1014
1015
1016
1017
1018
T = 400 KE = 300 eVHe+ + O2
jion = 1 x 1013
jion = 1 x 1014
jion = 1 x 1015
jion = 1 x 1016
eros
ion
rate
(cm
-2 s
-1)
O2 flux density (cm-2 s-1)
jion = 1 x 1017
![Page 29: CIPS SEWG FR, JET 2008C. Hopf O 2 /He glow discharge cleaning: Experience at IPP Christian Hopf, Volker Rohde, Wolfgang Jacob Max-Planck-Institut für Plasmaphysik](https://reader035.vdocument.in/reader035/viewer/2022070305/5514e624550346935c8b589d/html5/thumbnails/29.jpg)
CIPS
SEWG FR, JET 2008C. Hopf
(E) Ion + O2 synergism
Particle beam experiment:
Ar+ (20 to 800 eV) plus thermal O2 (background gas)
C. Hopf,a M. Schlüter, and W. Jacob, Appl. Phys. Lett. 90 (2007) 224106C. Hopf, M. Schlüter, T. Schwarz-Selinger, and W. Jacob, New. J. Phys., submitted
200 400 600 8000
5
10
15
20
0
2x1013
4x1013
6x1013
8x1013
Ar++O2
400 eV 200 eV 50 eV
only O2
yiel
d (C
/ A
r+)
temperature (K)
rate
(cm
-2 s
-1)
10 100 10000.1
1
10
1012
1013
1014
O2 at 800 K
800 K150 K300 K
yiel
d (
C /
Ar+
)
energy (eV)
rate
(cm
-2s-1
)
![Page 30: CIPS SEWG FR, JET 2008C. Hopf O 2 /He glow discharge cleaning: Experience at IPP Christian Hopf, Volker Rohde, Wolfgang Jacob Max-Planck-Institut für Plasmaphysik](https://reader035.vdocument.in/reader035/viewer/2022070305/5514e624550346935c8b589d/html5/thumbnails/30.jpg)
CIPS
SEWG FR, JET 2008C. Hopf
(3) a-C:H erosion samples: toroidal scan
123
4
5
6
7
8
9 1011
12
13
14
15
16
No a-C:H erosion where arcing occurred
C removedNo C removed
![Page 31: CIPS SEWG FR, JET 2008C. Hopf O 2 /He glow discharge cleaning: Experience at IPP Christian Hopf, Volker Rohde, Wolfgang Jacob Max-Planck-Institut für Plasmaphysik](https://reader035.vdocument.in/reader035/viewer/2022070305/5514e624550346935c8b589d/html5/thumbnails/31.jpg)
CIPS
SEWG FR, JET 2008C. Hopf
0
100
200
300
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 160
100
200
300
Thi
ckne
ss [
nm]
Sector
a-C:H erosion samples: toroidal scan
Anodes:
Roof Baffle
Outer Divertor
Film thickness left of initial 350 nm
No a-C:H erosion where arcing occurred
![Page 32: CIPS SEWG FR, JET 2008C. Hopf O 2 /He glow discharge cleaning: Experience at IPP Christian Hopf, Volker Rohde, Wolfgang Jacob Max-Planck-Institut für Plasmaphysik](https://reader035.vdocument.in/reader035/viewer/2022070305/5514e624550346935c8b589d/html5/thumbnails/32.jpg)
CIPS
SEWG FR, JET 2008C. Hopf
(B) Composition of AUG layers in 2005
Layers on all investigated tiles are boron and oxygen dominated
No significant erosion
No significant reduction of C or D concentration
HS IUD OUD0
10
20
30
40
50
60
70
80
90
Ato
mic
Fra
ctio
n (%
)
B
12C D O
13C
before O2 glow
HS IUD OUD0
10
20
30
40
50
60
70
80
90
B
12C D O
13C
after O2 glow
minimum and maximum concentrations on tiles
![Page 33: CIPS SEWG FR, JET 2008C. Hopf O 2 /He glow discharge cleaning: Experience at IPP Christian Hopf, Volker Rohde, Wolfgang Jacob Max-Planck-Institut für Plasmaphysik](https://reader035.vdocument.in/reader035/viewer/2022070305/5514e624550346935c8b589d/html5/thumbnails/33.jpg)
CIPS
SEWG FR, JET 2008C. Hopf
(E) Ion + O2 synergism
0 1 10 100 1000 100000
1x1013
2x1013
400 eV Ar+ + O2 --> a-C:H
T = 300 Kjion = 4 x 1012 cm-2 s-1
yiel
d (C
/ A
r+)
R = jO2/ jAr+
rate
(cm
-2 s
-1)
Ar+ + O2: O2 flux dependence
![Page 34: CIPS SEWG FR, JET 2008C. Hopf O 2 /He glow discharge cleaning: Experience at IPP Christian Hopf, Volker Rohde, Wolfgang Jacob Max-Planck-Institut für Plasmaphysik](https://reader035.vdocument.in/reader035/viewer/2022070305/5514e624550346935c8b589d/html5/thumbnails/34.jpg)
CIPS
SEWG FR, JET 2008C. Hopf
Where do the removed 25 g C come from?
Eroded carbon: 25 g = 1.2 x 1024 C atomsIons: 50 h x 5.4 A = 6 x 1024 Ions
Yield: 0.2 (in lab experiment: 0.1)
Arc pits: 40 holes / cm2
1 mm x 0.1 mm x 7 µmassumption: 20 m2 affected
8 g C eroded
Not W-covered surface: 34 %
Carbon dust
Not analyzed tiles with C-rich layers