R. Doerner, PFC Program Meeting, MIT, July 8-10, 2009 Mixed Interactions of W, Be, C, D & He R....

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R. Doerner, PFC Program Meeting, MIT, July 8-10, 2009

Mixed Interactions of W, Be, C, D & He

R. Doerner for the PISCES TeamIn collaboration with members of the US domestic fusion

program, the EU & Japanese programs, and the ITPA DIV/SOL



W Temperature & PMI are coupled

NAGDIS-II: He plasmaD. Nishijima et al. JNM (2004) 329-333 1029• Surface morphology • Shallow depth• Micro-scale

PISCES-A: D2-He plasmaM. Miyamoto et al. NF (2009) 065035600 K, 1000 s, 2.0x1024 He+/m2, 55 eV He+

• Little morphology• Occasional blisters

(b) Under focused (c) Over focused

10nm

10nm

(a) Bright field image (under focused image)

PISCES-B: pure He plasma M.J. Baldwin et al, NF 48 (2008) 0350011200 K, 4290 s, 2x1026 He+/m2, 25 eV He+

NAGDIS-II: pure He plasmaN. Ohno et al., in IAEA-TM, Vienna, 20061250 K, 36000 s, 3.5x1027 He+/m2, 11 eV He+

100 nm (VPS W on C) (TEM)

~ 600 - 700 K > 2000 K~ 900 – 1900 K

• Surface morphology • Evolving surface• Nano-scale ‘fuzz’



Mixed D/He reduces D retention in W at low temperature

date D Fluence

1026 D/m2

D retained

1020 D/m2

12/08 0.75 (+He) 0.109

12/08 1 3.77

12/08 0.5 3.84

03/08 1 3.27

03/08 0.1 2.37

0

0.001

0.002

0.003

0.004

-0.5 0 0.5 1 1.5 2 2.5 3

Depth (microns)

D/W

D+He 12/08 0.75E26 D/m2no He 12/08 1E26 D/m2no He 12/08 5E25 D/m2no He 03/08 1E26 D/m2no He 03/08 1E25 D/m2

W.R.WamplerSandia National Laboratories

200°C

With He

PISCES

● Addition of He to the D plasma reduced D retention by about a factor of 35.

● With He, D retention is mainly at the surface,whereas without He, D retention peaks ~ 1 micron beneath the surface.

See more details in talk of D. Nishijima

1e21 D/m2 ~ 3 mg/m2



At higher temperature, W ‘fuzz’ forms and is approx. 95% space

• SEM used to profile ‘fuzz’ layer thickness over sample surface.

• Geometric vol. of ‘fuzz’ layer est. (7.8 x10-10 m3 ±10%).

Distance from center of target (mm)

-10 0 10

Cro

ss s

ectio

nal h

eigh

t (

m)

-150

00

24

6 t = 3600 sEion = 30 eV

Ts=1120 K

He

nano-structuredlayer

W bulk

• ‘Fuzz’ layer removed. Mass change (Dm=0.87 mg ±1%).

Comp. w/ pure W, ( = 19.25 x103 kgm-3), ‘fuzz’ layer is 94 % porous.

PISCES



• If ‘fuzz’ is removed at equilibrium rate at 1120 K–

500 nm length:1.4 g.s-1m-2,0.62 g W per ITER shot 1600 shots to W dust limit.

10 nm length, 69 g.s-1m-2,0.3 kg W per ITER shot 320 shots to W dust limit.

Assuming ITER shot of 400 s and total strike point area w/ ‘fuzz’ growth to be 10 m2.

• ITER W dust limit is 100 kg.• A TOKAMAK experiment to

measure ‘fuzz’ erosion is NECESSARY.

‘Fuzz’ growth is fastest at early times

t (s)

0 5000 10000

Lay

er

thic

kne

ss, d

( m

)

05

Ts=1120 K

He

Ts=1320 K

He

Ts=1120 K

D2-0.2He

PISCES



Erosion rate of W fuzz

• Measurements are underway to determine erosion yield and angular distribution of eroded W fuzz

PISCES

0.01

0.1

1

0 100 200 300 400 500

W I/

Ar

II

Time [s]

Ei ~ 45 eV

Ei ~ 65 eV

Ei ~ 85 eV

Ei = 105 V

Integrated W atom surface loss rate from a nanostructured surface

Sputtered Ar on W angular distribution from a smooth surface

W fuzz

Smooth W



What about effects of D + He plasma on other ITER materials

PISCES

• D +10% He plasma also reduces retention in Be targets and alters surface

• D +10% He plasma on ATJ graphite has no effect on retention or surface

Pure DPlasma on Be200°C

D+0.1HePlasma on Be200°C

Surfacepits



PISCES

Retention in Be codeposits resulting from mixed D/He plasma exposure is also being investigated

• Co-deposits (from Be targetseroded by D2 and D2-He plasmas)is collected on W witness plates

• TDS up to 800 C shows a smallrelease of He from mixed speciesD2-He-Be co-deposits

• D2 release behavior is not significantly altered by thepresence of He

• Total D2 retention is increased byin the D2-He plasma case,but D/Be ratio is more relevant

• Be concentration is currently beingmeasured by NRA at IPP

Time (s)

1000 2000 3000

Par

tial P

ress

ure

(T

orr)

10-1

110

-10

10-9

10-8

10-7

Temperature (C)

200 400 600 800

He (Torr) D2 (Torr)

1000 2000 3000

Temperature (C)

200 400 600 800

He (Torr) D2 (Torr)



High priority ITPA DIV/SOL R&D tasks

The ITPA DIV/SOL group and ITER IO have identified 5 critical areas of R&D where community input is needed. While parts of the US PFC Program are included in the R&D effort, more involvement is encouraged. The next meeting of the ITPA DIV/SOL group will be at UCSD during Dec. 14-18, 2009. All are welcome to attend and contribute to this effort. The 5 primary R&D areas, along with the coordinators of those areas, are:

1) T retention – J. Roth and R. Doerner

2) Tungsten – A. Kallenbach and Y. Ueda

3) Dust – D. Rudakov and N. Ashikawa

4) Heat flux – A. Leonard and M. Lehnen

5) Erosion and Material Migration – P. Stangeby and V. Philipps

PISCES



Proposed T retention and removal work plan

1. Refine ITER prediction (MIT mini-meeting) : High priority• Participants (JAEA, FZJ, UCSD, IPP, Kyushu, CEA, MIT, UofT,

Sandia, ITER, JET, FOM)2. Fuel retention machine database : High priority

• Participants (FZJ, MIT, CEA, IPP, JET, GA, JAEA)

3. Ion cyclotron wall cleaning : High priority• Participants (VR, FZJ, MIT, CEA, IPP, JET, EAST, NIFS)

4. Disruption flash heating : Med. priority• Participants (CAE, UCSD, UKAEA, ITER, JET, MIT, GA)

5. Capability and risks of removing C : Med. priority• Participants (UofT, VR, FZJ, CEA, IPP, JET, GA)

6. Isotope exchange : Med. priority• Participants (JAEA, MIT, CEA, IPP, INL, Kyushu, FZJ, JET, GA)

7. T removal by heating to 350C : High priority• Participants (MIT, CEA, UCSD, IPP, INL, Sandia, UKAEA, GA. FZJ)

8. Retention in gaps : Med. priority• Participants (FZJ, IPP, INL, UKAEA, Kyushu, JET, GA, JAEA)

9. Influence of mixed species on retention : High priority• Participant (UCSD, IPP, Kyushu, FZJ, JAEA, UofT, JET)

R&D type

Time scale

Report Short(1-2 yr)

DSOL (new)

Med.(2-4 yr)

Report

Med.(2-4 yr)

Med.(2-4 yr)

Short(1-2 yr)

Short(1-2 yr)

Short(1-2 yr)

DSOL (with Material

Migration)

Med.(2-4 yr)

Collabo-ration

Short(1-2 yr)

Collabo- ration

DSOL (new)

DSOL (new)



Different heating profiles and different implantation doses are being studied

10-10

10-9

10-8

10-7

0

100

200

300

400

500

600

700

800

0 1000 2000 3000 4000

Be2C_2 [3.0E17 D implanted - 3.35E16 D retained]

Time (s)

Six types of material – Be on W Be on CFC Be12W Be2C C on Be W on Be

Four implantation doses - 3 E 16 D atoms (at room temp.) 3 E 17 D atoms

3 E 18 D atoms 3 E 19 D atoms

PISCES

10-10

10-9

10-8

10-7

0

200

400

600

800

1000

0 500 1000 1500 2000 2500 3000 3500

Be2C_3 [2.8E18 D implanted - 7.37E16 D retained]

Time[s]

350C



Retention and release from mixed material samples with Be-containing overlayers

• 200 nm Be layers deposited on substrates at MEdC, Romania

• Alloys formed and verified at IPP, Garching

• Samples implanted at room temperature with 200 eV D ions at IPP, Garching to a fluence of 4-5 E22 D/m2 (~3 E18 D atoms)

• TDS performed on samples at PISCES, UCSD

• Assumes all D is released from samples by TDS at 800C (to be confirmed by post-TDS NRA at IPP, Garching)

0

20

40

60

80

100

Annealed to 240CAnnealed to 350CAnnealed to 800C

Be on W Be on CFC Be2C Be12W

Total Dreleased

1.3E17 1.3E17 7.4E16 5.2E16

PISCES



Annealing to 350C is ineffective for release from C layers

W layers retain very little implanted DPISCES

10-10

10-9

10-8

10-7

0

200

400

600

800

1000

0 500 1000 1500 2000 2500 3000 3500

W on Be_3 [3E18 D implanted, 9.5E15 retained]

Time[s]

10-10

10-9

10-8

10-7

0

200

400

600

800

1000

0 500 1000 1500 2000 2500 3000 3500

C on Be_3 [3E18 D implanted - 8.3E16 retained]

Time[s]

350 C



PISCES continues to contribute to ITER R&D

• Mixed material/mixed plasma species effects on erosion, codeposition, retention and surface evolution

• Impact of transient heating on fuel retention and surface loss rates

• Plasma impurity transport, flow speed measurements and modeling comparison

• Active collaborations continue with members of the US fusion program, EU, Japan, China and the ITER IO

PISCES

R. Doerner, PFC Program Meeting, MIT, July 8-10, 2009 Mixed Interactions of W, Be, C, D & He R....

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