R. Doerner, EU SEWG meeting, JET. July 9-10, 2007 Co-deposition/Co-implantation R. Doerner, M. Baldwin, G. De Temmerman, D. Nishijima UCSD K. Schmid, Ch

U C S DU niversity o f C alifo rn ia S a n D iego

R. Doerner, EU SEWG meeting, JET. July 9-10, 2007

Co-deposition/Co-implantation

R. Doerner, M. Baldwin, G. De Temmerman, D. Nishijima

UCSDK. Schmid, Ch. Linsmeier, J. Roth

IPP Garching

• Database on atomic fraction of D in C, Be, W and mixtures

• Issues with the D/X invariant concept

• Thermal release behavior

• Conclusions



D codeposition with C

• No systematic data for D in C codeposits at different temperatures exist

• Data from Doyle is retention in a deuterium saturated carbon surface at different temperatures (in principle the same as a C codeposit)

0.001

0.01

0.1

1

0 100 200 300 400 500 600 700 800

D/C [from Doyle JNM 103&104(1981)513,]

Temperature (C)



D codeposition with C, Be

• Data from Mayer JNM 240(1997)164

• Low arrival rates of Be & D led to oxidation of deposit with water & CO

0.001

0.01

0.1

1

0 100 200 300 400 500 600 700 800

D/C

D/BeO (with ~15% C)

Temperature (C)




• Data from Causey JNM 254(1998)84

• Better vacuum conditions led to less O in codeposits and less D retained

• However,

@ 100C – 12% O

@ 150C – 3% O

@ 200C – 12% O

@ 300C – 6% O

0.001

0.01

0.1

1

0 100 200 300 400 500 600 700 800

D/CD/BeOD/Be (high O content)D/Be (low O content)

Temperature (C)




• Data from Baldwin JNM 337-339(2005)590.

• Oxygen content in 50C codeposits was 2-3%

• Oxygen content in 150C and 300C codeposits was 30%

• O content does not determine D content

0.001

0.01

0.1

1

0 100 200 300 400 500 600 700 800

D/CD/BeOD/Be D/BeD/Be

Temperature (C)



D codeposition with C, Be, W

• Data obtained in PISCES-B using 85% D & 15% Ar plasma

• Room temperature W codeposition measured by Mayer JNM 240(1997)164 also concluded a level below a few percent

0.001

0.01

0.1

1

0 100 200 300 400 500 600 700 800

D/CD/BeOD/BeD/BeD/BeD/W

Temperature (C)



D codeposition with mixed, Be/C and W/C, materials becomes less clear

• Be/C codeposits [Schmid 2005 ITPA] seem to retain D at levels between ‘pure’ Be & C

• W/C codeposits [Alimov Phys. Scripta T108(2004)46] seem to retain D similarly to pure W codeposits

• What is the role of C?0.001

0.01

0.1

1

0 100 200 300 400 500 600 700 800

D/CD/BeOD/BeD/BeD/BeD/WD/(W+C)D/(Be+C)

Temperature (C)



Focus on BerylliumWhat variables determine D/Be?

• Temperature of the layer during deposition seems to be the ‘most’ important (or at least most consistent) variable

• Oxygen content may have an influence, but does not solely determine the level of retention in Be codeposited/coimplanted samples

• Implantation energy of D may play a role

• Arrival rates of species may be important

• Other variables, geometry, pressure, layer structure…?



D/Be does not appear to be an invariant quantity

• Co-implantation energy alters the level of D/Be

• Baldwin (50 eV) and ‘cleaner’ Causey (100 eV) data consistent

• Both D and Be levels change with energy

• At similar energy, 3x increase in Be arrival rate results in 3x lower D/Be (X data point)

6 1016

8 1016

1 1017

1.2 1017

1.4 1017

1.6 1017

1.8 1017

2 1017

2.2 1017

0

0.2

0.4

0.6

0.8

1

40 60 80 100 120 140 160

D in Be on Tungsten witness plate at 100C

D/Be on Tungsten witness plate at 100C

Bias Voltage (~incident ion energy)

PISCES-B data recently analyzed by IPP

X



If D/’X’ is not invariant,

what can we say?



Thermal removal of D from C codeposits

Thermal desorption in vacuum from a-C:H layer created at 200°C [Winter Nucl. Instr.Methods B23(1987) 538]

[H/C ~ 0.4 +/- 0.14, in agreement with Doyle]



Thermal removal of D from Be codeposits

0

0.5

1

1.5

2

2.5

3

3.5

4

0 100 200 300 400 500 600 700 800

Temp (C)

Thermal desorption in vacuum from Be/D codeposit created at 150°C [Baldwin JNM 337-339(2005)590]

0

20

40

60

80

100

0 200 400 600 800 1000

Temp (C)



Thermal removal of D from W codeposits

Thermal desorption in vacuum from W/D codeposit created at 200°C

0

5 1012

1 1013

1.5 1013

100 200 300 400 500 600 700 800

Temperature (C)

0

20

40

60

80

100

100 200 300 400 500 600 700 800

Temp (C)



Deuterium is released more easily from Be codeposits during vacuum heating

0

20

40

60

80

100

120

0 200 400 600 800 1000

D remaining in BeD remaining in WD remaining in C

Temp (C)

[C containingmixed codeposits,Be/C or W/C,retain significant levels of D until heated to high temperature(>500C)]



Deposition conditions affect layer structure75 nm Be on Cu @ 300C6 mTorr D2~50% porosity

100 nm W on Cu @ 300C6mTorr D/Ar plasma

Thorton’s Zone model

From Thorton J. Vac. Sci. 11(1974)666.



Conclusions/summary

• The process of co-deposition/co-implantation is still poorly understood

• The existing methodology of attempting to determine the value of D/X for different ITER materials and mixtures of materials may be flawed

• Are present co-deposition layers representative of those expected in ITER? Are deposition conditions similar to those in ITER divertor, at ITER first wall?

• Emphasis needs to be placed on removal of retained D

Documents

R. Doerner, EU SEWG meeting, JET. July 9-10, 2007 Co-deposition/Co-implantation R. Doerner, M. Baldwin, G. De Temmerman, D. Nishijima UCSD K. Schmid, Ch