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					              Recent Studies of Mixed-Material
             Surface Processes at IPP Garching

                                       presented by K. Krieger

       Scientific team:
       K. Ertl, K. Krieger, Ch. Linsmeier, M. Mayer, K. Schmid (Senior Scientists).
       K. Sugiyama, M. Reinelt (Post-Docs).
       A. Anghel, Y. Gasparyan, F. Kost, H. Lee, K. Moshkunov, M. Oberkofler, B.
       Tyburska (PhD students)



K. Krieger, IAEA, Vienna, 12.03.2009
 Tasks from previous CRP meeting



       Measurements of erosion, implantation and D retention of D+C / He+C co-

           bombardment on W, D+13C co-bombardment on 12C at RT and elevated

           temperatures

       Benchmark TRIM.SP-2D with model system of 2D rough surface (Si ridges on Si)

       Studies of surface chemistry and D-retention in W/Be, W/C, Be/C and W/Be/C

           systems

       Measure D-retention in deposited mixed material layers




K. Krieger, IAEA, Vienna, 12.03.2009
 Outline




       Co-Bombardment of tungsten by deuterium and carbon.
       2D surface roughness model system.
       Surface processes in the ternary ITER materials system Be/C/W.
       Influence of mixed material layers on fuel retention and
        permeation properties.




K. Krieger, IAEA, Vienna, 12.03.2009
 Outline




       Co-Bombardment of tungsten by deuterium and carbon.
       2D surface roughness model system.
       Surface processes in the ternary ITER materials system Be/C/W.
       Influence of mixed material layers on fuel retention and
        permeation properties.




K. Krieger, IAEA, Vienna, 12.03.2009
 The IPP Dual Beam Experiment

                                                     Sputter Ion Source:
    Sputter ion source                                produces beams of solid
                                                      state elements in E=1-12keV

                                                     Duoplasmatron Source:
                                                      produces H, D, He, Ne, Ar
                                                      beams in E=0.5-10keV




                                       High energy
                                       beamline      Variable C/D ratio by
                                                     independent sources

                                                     MeV Beam Line:
              Duoplasmatron ion source               provides in-situ Ion Beam
                                                     Analysis (NRA, RBS)

K. Krieger, IAEA, Vienna, 12.03.2009
 Experimental procedures
 Model system: W layer on substrate


                                       Beam Viewing System




  Bombard tungsten
   simultaneously with D and C
  Measure W erosion and C/D
   implantation as function of
   incident fluence and temperature

  Key parameters:
   local C/D fluence
   local C/D ratio

K. Krieger, IAEA, Vienna, 12.03.2009
 Simulation of sputter/implantation dynamics - TRIDYN

         Monte-Carlo simulation of particle trajectories in solid assuming
         binary collisions (TRIDYN ≡ SDTrimSP)
          Scattering angles computed according to classical scattering theory
          Dynamic change of target composition by adaptive layer structure




                                        Processes not in TRIDYN:
                                         Thermally enhanced C self-sputtering
                                         Chemical erosion of C by D
                                         Development of surface roughness
                                         Diffusion (not in this temp. range)


K. Krieger, IAEA, Vienna, 12.03.2009
 Two Principal Regimes
                                        C layer growth     6keV C + 3keV D              W
                         0.6
                                                                EXP.           TRIDYN
                                                                  25%      :
                                                                  16%      :
   Implanted C (10 m )
  -2




                         0.4
                                                                  13%      :                  Deviations from
                                                                  7%       :
  22




                                                                                              TRIDYN observed
                                                                                              for W erosion case


                         0.2
                                                                                              Continuous
                                                                                              W Erosion



                         0.0
                            0.0   0.1        0.2         0.3    0.4        0.5          0.6
                                                               22     -2
                                           W Sputtered (10 m )

K. Krieger, IAEA, Vienna, 12.03.2009
 Continous W erosion regime – Chemical effect
                                                                                            C fraction in incident flux (%)
         6keV C + 3keV D               W                                    0.20
                                                                                   0               5               10                15

                                                                                             TRIDYN
                                                                                             EXP.                 Steady state
  TRIDYN indicates increasing C                                                             TRIDYN




                                             C implanted (x10 m )
                                                                            0.15




                                           -2
   concentration with fc




                                           22
                                                                            0.10
  Transition point : 8%<fc<9%
                                                                            0.05
  Experiments indicates constant C
   concentration with fc
                                                                            0.00
                                                                                       [1] M. Balden et al. JNM 337-339 (2005) 980
  Transition point : 10%<fc<12%



                                           Chemical Sputter Yield (YC/D )
                                                                            0.02
  Chemical erosion from mixed material:
    C lower limit: ~0.75x1022m-2
                                                                            0.01

  Chemical sputter yield’s maximum is
  before the onset of C layer buildup
                                                                            0.00
    CD4/D = ~0.025 [1]                                                            0               5               10                15

                                                                                            C fraction in incident flux (%)


K. Krieger, IAEA, Vienna, 12.03.2009
 Continous W erosion regime – High Temp
                                                         6keV 3keV D
                                                      6keV C + + 3keV D               W

                                                                    Temp : 7%   TRIDYN          Increasing Temp:
                            0.2                                     RT :
                                                                    400C:
                                                                    500C:
                                                                                                increase in
                                                                    600C:                      implanted C amount
      Implanted C (10 m )
     -2




                                                                                                in mixed material
     22




                                                                                                layer

                            0.1                                                                 approaches
                                                                                                TRIDYN results.
                                                                                                Chemical erosion
                                                                                                from mixed material
                                                                                                is largest at RT
                            0.0
                               0.0   0.2   0.4       0.6     0.8         1.0    1.2       1.4
                                                               22   -2
                                                 W Sputtered (10 m )



K. Krieger, IAEA, Vienna, 12.03.2009
 C deposition regime – High Temp
                                                    6keV C + 3keV D          W
                                                                                   Increasing Temp:
                                                      Temp : 25% : TRIDYN
                                                      RT    :                      increase in W
                         0.8
                                                      500C :                      sputtering due to
   Implanted C (10 m )
  -2




                                                      600C :                      loss of C in mixed
                                                                                   material layer
  22




                         0.6

                                                                                   Transition point
                         0.4                                                       shifts to higher fc
                                                                                   400-500°C: 11%<fc<14%
                                                                                   600°C: 14%<fc

                         0.2
                                                                                   Need to separate
                                                                                   kinematic from
                         0.0                                                       chemical effects
                            0.0   0.1   0.2   0.3   0.4   0.5    0.6   0.7   0.8

                                                           22    -2
                                         W Sputtered (10        m )

K. Krieger, IAEA, Vienna, 12.03.2009
 C deposition regime – Chemical effect
                                                                    6keV C + 3keV D                                             W
                                         Kinematic component                                                                    Chemical component
                                                         Temp : 25% : TRIDYN                                              500C          TRIDYN
                                                         RT    :
                        0.8
                                                         500C :
                                                                                                                0.8       25%:




                                                                                         Implanted C (x10 m )
  Implanted C (10 m )




                                                                                        -2
 -2




                                                         600C :                                                                 ()/  = 1-R-Yphys




                                                                                        22
 22




                        0.6                                                                                     0.6


                        0.4                                                                                     0.4


                        0.2                                                                                     0.2

                                                                                                                                               ’()/ ’ = 1-R-Yphys-Ychem
                        0.0                                                                                     0.0
                           0.0     0.1    0.2   0.3   0.4    0.5    0.6   0.7   0.8                                   0     2       4      6        8        10    12    14

                                                             22     -2                                                                                  22    -2
                                           W Sputtered (10         m )                                                           Total Fluence (x10 m )



              Assuming Yphys & R is similar: first approximation yields YC/D ~ 0.07-0.08
                • Similar to the chemical yield of pure C at 3keV D at 527°C [3]
                                 [3] J. Roth, C. Garcia-Rosales, Nuclear Fusion, Vol. 36, No. 12 (1996)
              At high temp the effect of D is observed with the buildup of a C layer

K. Krieger, IAEA, Vienna, 12.03.2009
 Summary




       In W sputtering regime: chemical erosion of W-C greatest at RT
        and decreases with temperature.
       In C deposition regime: chemical contribution negligible until
        buildup of C occurs which follows pure C behavior.




K. Krieger, IAEA, Vienna, 12.03.2009
 Outline




       Co-Bombardment of tungsten by deuterium and carbon.
       2D surface roughness model system.
       Surface processes in the ternary ITER materials system Be/C/W.
       Influence of mixed material layers on fuel retention and
        permeation properties.




K. Krieger, IAEA, Vienna, 12.03.2009
                                                 Collaboration with I. Bizyukov (U.
 2D Model System - Ar bombardment                Toronto), A. Mutzke, R. Schneider
                                                 (U. Greifswald)




                           virgin      after irradiation




                                                                        Si ridges




                                                                        Si substrate


K. Krieger, IAEA, Vienna, 12.03.2009
 SDTrimSP-2D




K. Krieger, IAEA, Vienna, 12.03.2009
                                         Collaboration with I. Bizyukov (U.
 Comparison to modelling                 Toronto), A. Mutzke, R. Schneider
                                         (U. Greifswald)




                           experiment   SDTrimSP-2D result




K. Krieger, IAEA, Vienna, 12.03.2009
 Outline




       Co-Bombardment of tungsten by deuterium and carbon.
       2D surface roughness model system.
       Surface processes in the ternary ITER materials system Be/C/W.
       Influence of mixed material layers on fuel retention and
        permeation properties.




K. Krieger, IAEA, Vienna, 12.03.2009
 Depth resolved XPS at BESSY - Experimental setup




                                       Approach: Characterisation of temperature
                                       driven processes such as diffusion,
                                       sublimation and phase transitions by depth-
                                       resolved XPS using synchrotron radiation




K. Krieger, IAEA, Vienna, 12.03.2009
 Investigation of C/Be/W-system with depth-resolved XPS

                                                                 elemental   carbidic

                                                              C 1s                                h = 340 eV
  • C / Be / W                                                                                    Ekin = 60 eV




                                                                                    temperature
  • dBe = 2.4 nm, dC = 1.5 nm




                                           intensity [a.u.]
                                                              1200K
  • 5 temperature steps, RT – 1200 K
  • 4 analysis depths
                                                              300K



                                                              1200K                               h = 980 eV
  Status:                                                                                         Ekin = 700 eV
  • First depth-resolved synchrotron
    measurements performed successfully
  • Measurements deliver deeper insight into                  300K
    the reaction kinetics                                     290 288 286 284 282 280 278

                                                              binding energy [eV]




  Plans for 2009/10 • Setup of a preparation chamber at BESSY

K. Krieger, IAEA, Vienna, 12.03.2009
 Summary

        • Be2C formation complete at 850 K

        • Be2C formation starts at the interface and
          expands to the surface
        • beginning island formation at 1020 K,
          pronounced island formation at 1200 K

        • C diffusion into the bulk

        • Be2W formation increases up to 850 K, then
          decrease due to W2C formation

        • W2C formation starting at 850 K


                                       Consistent with laboratory experiments


K. Krieger, IAEA, Vienna, 12.03.2009
 Outline




       Co-Bombardment of tungsten by deuterium and carbon.
       2D surface roughness model system.
       Surface processes in the ternary ITER materials system Be/C/W.
       Influence of mixed material layers on fuel retention and
        permeation properties.




K. Krieger, IAEA, Vienna, 12.03.2009
 D retention in ITER-related mixed material layers

       Preparation of compound layer
       • Annealing of C film (~ 200 nm) on Be substrate sample at 773K with 3 hours
         → Be2C layer formation
       • Annealing of W film (~ 200 nm) on Be substrate sample at 1073K with 10 hours
         → Be12W layer formation
       • Annealing of W film (~ 200 nm) on graphite substrate at 1373K with 3 hours
         → Tungsten carbide layer formation


       D implantation to prepared layers
       • 200 eV D ions implantation (flux ~ 1019 D/m2) in the High Current Ion Source in
         Garching.


       Evaluation on D retention in prepared layers
       • Quantitative analysis by NRA using D(3He, p)4He reaction




K. Krieger, IAEA, Vienna, 12.03.2009
 D retention in ITER-related mixed material layers


                                                   Be2C
    Layer characterisation by RBS / XRD
    • Annealing of C film (~ 200 nm) on Be
      substrate sample at 773K with 3 hours
       → Be2C layer (~ 900 nm) formation

    • Annealing of W film (~ 200 nm) on Be         Be12W
      substrate sample at 1073K with 10 hours
       → Be12W layer (~ 2 µm) formation

    • Annealing of W film (~ 200 nm) on graphite
      substrate at 1373K with 3 hours
                                                   W2C / WC
       → W2C / WC layer (~ 300 nm) formation




K. Krieger, IAEA, Vienna, 12.03.2009
 D retention in ITER-related mixed material layers

                                                                                                                              100% retention
                                                                                                                               Pyrolytic Graphite
                                                                                                                              Pyrolytic graphite
                                                                                                                                Pyrolytic graphite
                                                                                                                              Be (Anderl et
                                                                                                                              100% retention al.)
                                                                                                                               Beryllium
                                                                                                                                Beryllium
    D in compound layers                                                                                                      200eV GraphiteW
                                                                                                                              Pyrolytic D -> PCW
                                                                                                                               Polycrystalline W
                                                                                                                                Polycrystalline
                                                                                                                              Be (Anderl et al.)
                                                                                                            22                Be2C
                                                                                       10                                     200eV D -> PCW
    • Fluence dependence of Be12W is                                                                        10
                                                                                                                 22           Be12W
                                                                                                                              Be2CC(~ 900 nm) on Be
                                                                                                                               Be2C (~ 900 nm) on Be
                                                                                                                               Be2
      close to that of Be rather than PCW.                                                                        22          W carbide m) on Be
                                                                                                                              Be12W (~ 2 on Graphite
                                                                                                                                  Be12W (~ 2 m) on Be
                                                                                                                               Be W
                                                                                                             10                    12
                                                                                                                               WC W on Graphite
                                                                                                                              W carbideC (~ 300 nm) on graphite
                                                                                                                              WC //W C (~ 300 nm) on graphite
                                                                                                                                             22

    • D in Be2C layer showed similar




                                               D retained fluence [D/m ]
                                               2
      fluence dependence to Be as well as                                                                   21




                                                              D retained fluence [D/m ]
                                                                                       10




                                                                   2
                                                                                                                                                                  Be2C




                                                                                D retained fluence [D/m ]
      Be12W layer, but its amount was




                                                                                    2




                                                                                                                                        n
                                                                                                                 21




                                                                                                                                       tio
                                                                                                            10
                                                                                                             10
                                                                                                                  21
      slightly higher.




                                                                                                                                  en
                                                                                                                              r et
    • D in tungsten carbide layers is larger




                                                                                                                           0%
      than PCW by a factor of 2 ~ 3, and                                                                    20                                    Be12W
                                                                                       10




                                                                                                                         10
      similar fluence dependence with                                                                        10
                                                                                                              20
                                                                                                                  20

      PCW rather than graphite.                                                                             10                W2C / WC

                                                                                                            19
                                                                                       10
                                                                                                                  19
                                                                                                                  19              20              21             22             23                 24          25
                                                                                                             10
                                                                                                             10              10              10             10             10                 10          10
                                                                                                                        19             20              21             22         23                 24             25
                                                                                                                 1910             10           10       10      10
                                                                                                                                             Incident fluence [D/m ]
                                                                                                                                                                                 2             10         10
                                                                                                            10                                                                       2
                                                                                                                       19               20        Incident fluence [D/m ]
                                                                                                                                                       21        22                           23              24
                                                                                                                  10              10               10                 10                 10              10
                                                                                                                                                                                               2
                                                                                                                                                       Incident fluence [D/m ]
K. Krieger, IAEA, Vienna, 12.03.2009
 Influence of surface layers on D-retention in W




K. Krieger, IAEA, Vienna, 12.03.2009
 Boron film/W:NRA
                         2.5h +        1.3h

    Irradiation time:
                                                     Bulk deuterium signal
                           Complete film
                           erosion time




                                              8 µm
                             2h
                                                             7 nm
     Irradiation time:




K. Krieger, IAEA, Vienna, 12.03.2009
 Al2O3/W: NRA

                                        10h +                        6h
                                                 Irradiation time:


                                                           Complete film
                                                           erosion time




                                                            8h

                                       Irradiation time:



K. Krieger, IAEA, Vienna, 12.03.2009

				
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