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Ion Beam Induced Desorption Yield Measurements at GSI

Ion Beam Induced Desorption Yield Measurements at GSI. The 13th ICFA Beam Dynamics Mini-Workshop Beam Induced Pressure Rise in Rings Brookhaven National Laboratory, Upton, NY December 9 - 12, 2003. Dynamic Vacuum and Beam Lifetime. P. Spiller, December 2001 8.75 MeV/u U 28+.

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Ion Beam Induced Desorption Yield Measurements at GSI

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  1. Ion Beam Induced Desorption Yield Measurements at GSI The 13th ICFA Beam Dynamics Mini-WorkshopBeam Induced Pressure Rise in RingsBrookhaven National Laboratory, Upton, NYDecember 9 - 12, 2003 Andreas Krämer - GSI Darmstadt

  2. Dynamic Vacuum and Beam Lifetime P. Spiller, December 2001 8.75 MeV/u U28+ Desorption processes degenerate the residual gas pressure. Initiated by: • Systematic beam losses on acceptance limiting devices (septa) • Stripped beam ions • Ionized and accelerated residual gas Beam losses increase with number of injected ions ( shorter beam life time due to stronger pressure bumps ) Andreas Krämer - GSI Darmstadt

  3. Desorption Processes in SIS18 vacuum chamber wall S: pumping speed/therm. desorption X septum or collimator X hloss X X UZ+ UZ+ UZ+ q e sX sloss X F50 Volt space charge potential X X X Xq+ UZ+q hX hloss beam loss induced desorption ion induced desorption desorption yield h: Andreas Krämer - GSI Darmstadt

  4. Measurements @ SIS18 Andreas Krämer - GSI Darmstadt

  5. Fast Pressure Measurements in SIS18 First fast pressure measurements and prove of desorption processes in SIS18 in October 2001 8.9 MeV/u U28+ S01 S04 S06 Transformer Andreas Krämer - GSI Darmstadt

  6. Vacuum Pressure Instability in SIS18 U28+ ion beam lifetime @ 8.9 MeV/u Beam current (mA) P average pressure, I beam current, S pumping speed, h desorption yield, s charge exchange cross section. (E. Mustafin et al., NIM A510, 199 (2003)) Andreas Krämer - GSI Darmstadt

  7. Fit Results for Lifetime Measurements of U28+ E. Mustafin et al., NIM A510, 199 (2003) 1mA corresponds to 109 ions Andreas Krämer - GSI Darmstadt

  8. Measurements @ SIS18 Andreas Krämer - GSI Darmstadt

  9. Pressure Rise During Localized Beam Loss U. Weinrich et al., GSI Internal Report (2002) Andreas Krämer - GSI Darmstadt

  10. Fast Pressure Measurements Continuous injection of 8.7 MeV/u 5107 U28+ ions every 1.8 sec S12 S01 S06 100 sec h  5200 U. Weinrich et al., GSI Internal Report (2002) Andreas Krämer - GSI Darmstadt

  11. SIP ion gauge ion gauge RGA collimator from accelerator current transformer conductance 10-7mbar sector valve TMP TMP TSP sample holder 10-10mbar 10-8mbar Experimental Setup for Ion Beam Induced Desorption Yield Measurements Experiments by: M. Bender (GSI) H. Kollmus (GSI) A. Krämer (GSI) Andreas Krämer - GSI Darmstadt

  12. Total Pressure Increase due to Desorption 1.4 MeV/u C2+ Al, perpendicular incidence Single shot Continuous bombardment 1Hz, 91010 ions/pulse h≈110 Continuous bombardment Single shot 91010 ions/pulse h≈170 Andreas Krämer - GSI Darmstadt

  13. Total Pressure Increase due to Ion Beam Induced Desorption 1.4MeV/u 1.8-3.1·109 (1.9-3.3mA, 4ms) Pb27+ stainless steel 304 Andreas Krämer - GSI Darmstadt

  14. Partial Pressure Increase due to Ion Beam Induced Desorption 1.4MeV/u 1.8-3.1·109Pb27+ stainless steel 304 The measured ion current was corrected for the ionization probabilities of the different gases: H2: x2.3 CO: x0.95 CO2: x0.71 CH4: x0.625 Desorption dominated by H2 (87%) and CO (11%) Andreas Krämer - GSI Darmstadt

  15. Single Shot Results of Desorption Yield Measurements at GSI [M. Bender, H. Kollmus, A. Krämer (GSI UHV group)] Energy: 1.4 MeV/u, Intensities: 109 – 1011 ions per pulse, perpendicular incidence The calculated desorption yields are not corrected for the "real" gas composition, which is H2 dominated. Therefore the desorption yields are underestimated by a factor of about 2. Andreas Krämer - GSI Darmstadt

  16. Experimental Set-Up with additional CERN hardware 1.4MeV/u Zn10+ Experiment by: E. Mahner (CERN) M. Bender (GSI) H. Kollmus (GSI) A. Krämer (GSI) GSI R.G.A. CERN B.A.G. GSI gauge high current injector (HLI) CERN R.G.A. Andreas Krämer - GSI Darmstadt

  17. Latest Experiment with Zn10+ at 1.4MeV/u CERN Samples by Edgar Mahner Andreas Krämer - GSI Darmstadt

  18. Target Holder with CERN Samples [pictures by G. Otto (GSI)] Andreas Krämer - GSI Darmstadt

  19. Desorption Yields calculated out of Single Shot Experiments 1.4MeV/u Zn10+ Desorption yields are calculated with: assuming S=5.52l/s (N2 equivalent) Dp was measured with an extractor ion gauge. • No influence of the high melting temperatures of Nb, Mo, Ta, W, • Re in comparison to 316LN and 304L •  of coatings independent of thickness and bulk material Andreas Krämer - GSI Darmstadt

  20. Desorption Yields Calculated from Scrubbing Plots by E. Mahner (CERN) 1.4MeV/u Zn10+ Mainly desorbed gases are H2 and CO. Andreas Krämer - GSI Darmstadt

  21. Pulse Length and Frequency Dependence of Partial Pressures 1.4 MeV/u Zn10+ TiZrV/316LN (fired) • Intensity dependence of : • linear? • new effects at high intensities? Plot by E. Mahner (CERN) Andreas Krämer - GSI Darmstadt

  22. 25Hz 5.5ms 10Hz 8.33Hz 6.25Hz 4.17Hz 2Hz 5.5ms 1Hz 5.5ms 4ms 3ms 2ms 1ms 0.49ms Pulse Length and Frequency Dependence of Partial Pressures 1.4 MeV/u Zn10+ 316LN (fired) Flux vs Dp 8.0x10-8 7.0x10-8 6.0x10-8 5.0x10-8 4.0x10-8 3.0x10-8 2.0x10-8 1.0x10-8 0.0 0.0 5.0x1011 1.0x1012 1.5x1012 Flux [ions/s] Plots by E. Mahner (CERN) Andreas Krämer - GSI Darmstadt

  23. Beam Scrubbing 1.4 MeV/u Zn10+ 304 1Hz, 5.5ms pulse length  4x1010 ions/pulse ° H2 ° CH4 ° H2O ° CO ° O2 ° CO2 Scrubbing effect for CO stronger than for H2 Plot by E. Mahner (CERN) Dose [ions/s/cm2] 2.9x1012 2.9x1013 2.9x1014 Andreas Krämer - GSI Darmstadt

  24. Summary & Outlook • First experiments under perpendicular incidence with different projectile ions and target materials/coatings at 1.4MeV/u at GSI • Next Step: Modified(?) experimental setup at UNILAC with energies up to 11MeV/u [implementation of an electron detector] • Together with material science: ERDA measurements for surface and bulk analysis up to 1mm depth (Ph.D. thesis) Further to be studied: • Desorption at higher energies up to 1GeV/u • Desorption of cold vacuum chamber walls for SIS100 and SIS300 Andreas Krämer - GSI Darmstadt

  25. E1 Z1 m1 E2 Z2 m2 Elastic Recoil Ion Detection Analysis (ERDA) Ion Beam Recoil Ion • same sensitivity for all elements • Z14 dependence ( m=2Z ) • depth profile easy accessible  Sample Rutherford-Scattering: ERDA-Cross Section: for heavy ions: m2/m1 << 1  all recoil ions have approx the same velocity v ( similar energy loss) Andreas Krämer - GSI Darmstadt

  26. Experimental Setup for ERDA Measurement UHV environment Sample Ion Beam Recoil Ion Cathode Window Lattice • E : Element (Z) • Erest: Depth • tD : Emission Angle () Anode (E) tD PIN-Diode (Erest) H. D. Mieskes et al., Measuring sputtering yields of high energy heavy ions on metals, NIM B 146 (1998) Andreas Krämer - GSI Darmstadt

  27. E Eres ERDA-Spektra in-situ ERD energy profile of O-contamination in a Ti - sample 200 MeV Au<30+>  304 L stainless steel O N C H. D. Mieskes et al., NIM B 146 (1998) Andreas Krämer - GSI Darmstadt

  28. Advantages of ERDA • element specific depth profile, • typical depth up to 1 m with 20 nm resolution • clear distinction between surface and bulk • in-situ measurement of material changes under radiation • combinable with total and partial pressure measurements • combinable with measurement of electronic desorption yields Andreas Krämer - GSI Darmstadt

  29. Acknowledgement • M. Bender, O. Boine-Frankenheim, B. Franczak,W. Kaufmann,H. Kollmus,E. Mustafin,H. Reeg, H. Reich-Sprenger, P. Schütt, P. Spiller, U. Weinrich (GSI; Accelerator Division) • E. Mahner (CERN; AT-Division, Vacuum Group) • C. Trautmann (GSI; Material Science) • W. Assmann (LMU Munich) Andreas Krämer - GSI Darmstadt

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