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Co-deposition of deuterium and impurities in plasma-wall interaction simulators Marek Rubel a, Per Petersson a, Arkadi Kreter b a Alfvén Laboratory, KTH,

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Presentation on theme: "Co-deposition of deuterium and impurities in plasma-wall interaction simulators Marek Rubel a, Per Petersson a, Arkadi Kreter b a Alfvén Laboratory, KTH,"— Presentation transcript:

1 Co-deposition of deuterium and impurities in plasma-wall interaction simulators Marek Rubel a, Per Petersson a, Arkadi Kreter b a Alfvén Laboratory, KTH, Association EURATOM–VR, Stockholm, Sweden b IEK-4, Forschungszentrum Jülich, Association EURATOM, Jülich, Germany O U T L I N E Exposures of carbon-based materials: PISCES-A and PSI-2. Surface composition of targets: deuterium and impurity species Summary and concluding remarks Content is a bit archaic but NOT obsolate - as long as PWI simulators are in operation.

2 PISCES-A (1988) Experiments The Aim: To determine erosion of carbon-based materials: CF222, CF222 + 1  m SiC, C+SiC 30% – Schunk GmbH; CL5890PT – Le Carbonne Lorraine Exposures:  D = 1.15 – 2.81 x 10 25 (2 samples 8.8 and 31.8 x 10 25 ) Target T: 623 – 1200 K Sample size: disk  25 mm E. Franconi, M. Rubel and B. Emmoth, Nucl. Fusion 29 (1989) 737. B. Emmoth, M. Rubel and E. Franconi, Nucl. Fusion 30 (1990) 1140.

3 Ion Beam Analysis E. Franconi, M. Rubel and B. Emmoth, Nucl. Fusion 29 (1989) 737. B. Emmoth, M. Rubel and E. Franconi, Nucl. Fusion 30 (1990) 1140. Methods: Rutherford Backscattering Spectroscopy (RBS) Nuclear Reaction Analysis: 3 He(d,p) 4 He and p( 11 B,  ) 8 Be Thin layer: 50 nm Thick layer: 3000 nm Channel Number Proton Yield (counts) Deuterium content and distribution PISCES-A, 1988

4 Ion Beam Analysis: Impurities E. Franconi, M. Rubel and B. Emmoth, Nucl. Fusion 29 (1989) 737. B. Emmoth, M. Rubel and E. Franconi, Nucl. Fusion 30 (1990) 1140. Backscattering Yield (counts 10 -2 ) Channel Number PISCES-A, 1988 Yield (counts 10 -2 ) Channel Number B Impurities from plasma generator: B and La from LaB 6 (cathode) Cu (anode) Erosion from the chamber wall: Steel components Fe, Ni, Cr

5 Deuterium and impurities on samples after single exposures D and impurity content on samples after single exposures. ExposureTargetT (K)D (10 15 cm -2 )Imp (10 15 cm -2 ) SingleCL5890PT6735730 - 50 CF 222102329 - 3936 - 81 CFC + SiC film12009 - 1588 - 340 C + SiC3012004 - 753 - 87 C + SiC3012004 - 10105 - 410 DoubleC + SiC30623 - 823116 - 158230 - 300 C + SiC3010231564 - 120 C + SiC30873 - 1073135 – 218300 – 550 8 exposuresCL5890PT623 – 120070 - 350044 - 10000 More impurities than deuterium. E. Franconi, M. Rubel and B. Emmoth, Nucl. Fusion 29 (1989) 737. B. Emmoth, M. Rubel and E. Franconi, Nucl. Fusion 30 (1990) 1140. PISCES-A, 1988

6 Messages Highly inhomogeneous distribution of species. Amount of impurities is greater than the deuterium content. ExposureTargetT (K)D (10 15 cm -2 )Imp (10 15 cm -2 ) SingleCL5890PT6735730 - 50 CF 222102329 - 3936 - 81 CFC + SiC film12009 - 1588 - 340 C + SiC3012004 - 753 - 87 C + SiC3012004 - 10105 - 410 DoubleC + SiC30623 - 823116 - 158230 - 300 C + SiC3010231564 - 120 C + SiC30873 - 1073135 – 218300 – 550 8 exposuresCL5890PT623 – 120070 - 350044 - 10000 E. Franconi, M. Rubel and B. Emmoth, Nucl. Fusion 29 (1989) 737. B. Emmoth, M. Rubel and E. Franconi, Nucl. Fusion 30 (1990) 1140. Deuterium and impurity content on samples: All results.

7 Ion Beam Analysis: Impurities E. Franconi, M. Rubel and B. Emmoth, Nucl. Fusion 29 (1989) 737. B. Emmoth, M. Rubel and E. Franconi, Nucl. Fusion 30 (1990) 1140. PISCES-A, 1988 Backscattering Yield (counts) Channel Number Spectra recorded in several points on the graphite sample exposed 8 times to plasma. Distance between points: 5 mm

8 PISCES-A (2008) Experiment The Aim: To determine deuterium retention in graphites and CFCs. (NB-41 = CFC, Snecma; ITER reference carbon material; ATJ = graphite) Exposure:  D = 1- 50 x 10 25 m -2 Target T: 370 - 820 K Sample size: disks  25 mm Number of samples: 3 A. Kreter et al., Phys. Scr. T138 (2009)

9 PISCES-A (2008): Example of results D: 152±5 La 3,4 D: 173±5 La 3,5 D: 155±7 La 3,9 D: 126±5 La 4,8 Sample NB41 (B) Surface concentration of deuterium and lanthanum (10 15 cm -2 ) NB41 Sample (C) D: 25 x 10 15 cm -2 La: 90 x 10 15 cm -2

10 PSI-2 (Berlin, 1998)

11 Experiment The Aim: To determine deuterium retention in NS-31. (NS-31 = CFC with SiC, Snecma) Exposure:  D = 1.26 x 10 25 (5 h, 7x10 21 m -2 s -1 ) Target T: 420 K Sample size: disk  20 mm

12 Ion Beam Analysis of NS-31 Channel Number 500 750 1.500 0 Backscattering Yield (Counts) 0 1.500 Impurities 800 10 4 0 Backscattering Yield (Counts) 10 4 0 0800 400 Channel Number C Si Enhanced Proton Scattering: 1500 keV H +, 1 or 3 mm beam

13 PSI-2 (Berlin, 1998): NS-31 Channel Number 500 750 1.500 0 Backscattering Yield (Counts) 0 1.500 C O Ta La Mo Cu Si O C Cu Mo Ta La Messages Significant amount of co-deposited impurity species originating from the plasma generator. Not uniform distribution of impurity species on the surfaces in areas located 5-7 mm apart. Significant difference in the Si content on the surface – very inhomogeneous NS-31 material. Enhanced Proton Scattering: 1500 keV H +, 1 or 3 mm beam

14 Summary of Results PSI-2 D: 104 – 152 x 10 15 cm -2 B: 46 – 290 x 10 15 cm -2 Cu and Ni: 93 – 189 x 10 15 cm -2 Mo:5.0 – 9.0 x 10 15 cm -2 La and Ta: 4.2 – 9.9 x 10 15 cm -2 Boron and copper (and nickel) are major impurities. The amount of impurity species exceeds the content of deuterium in the studied surface.

15 Summary and Concluding Remarks Plasma generation in PMI simulators is accompanied by erosion of materials from the plasma source and the experimental chamber. Main impurities are Cu, La, B, Mo, Ni, Ta. These species are co-deposited on the exposed target. Impurity co-deposition is independent on the target T surface. The amount of impurity species usually exceeds the content of deuterium on the studied surface. Deposition pattern is not homogeneous indicating strong differences in the uniformity of the plasma column.

16 Summary and Concluding Remarks It is unreasonable to expect that impurity production can be avoided but the process must be monitored and taken into account when concluding on: material erosion (sputter yield changes!); fuel retention (surface state plays here crucial role) effects of surface modification. Multiple exposures of targets should probably be avoided unless these are dedicated experiments.

17 Questions? Comments?


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