1. ICFA Workshop, December 9-12, 2003 Andreas Krämer - GSI Darmstadt1 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

2. ICFA Workshop, December 9-12, 2003 Andreas Krämer - GSI Darmstadt2 Dynamic Vacuum and Beam Lifetime 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 ) Desorption processes degenerate the residual gas pressure. P. Spiller, December 2001 8.75 MeV/u U 28+

3. ICFA Workshop, December 9-12, 2003 Andreas Krämer - GSI Darmstadt3 Desorption Processes in SIS18 desorption yield  beam loss induced desorptionion induced desorption vacuum chamber wallS: pumping speed/therm. desorption septum or collimator U Z+ X X X X X X X X X q+ q e U Z+q  loss XX  loss XX  50 Volt space charge potential

4. ICFA Workshop, December 9-12, 2003 Andreas Krämer - GSI Darmstadt4 Measurements @ SIS18

5. ICFA Workshop, December 9-12, 2003 Andreas Krämer - GSI Darmstadt5 Fast Pressure Measurements in SIS18 S01 S04 S06 Transformer First fast pressure measurements and prove of desorption processes in SIS18 in October 2001 8.9 MeV/u U 28+

6. ICFA Workshop, December 9-12, 2003 Andreas Krämer - GSI Darmstadt6 Vacuum Pressure Instability in SIS18 P average pressure, I beam current, S pumping speed,  desorption yield,  charge exchange cross section. Beam current (mA) U 28+ ion beam lifetime @ 8.9 MeV/u (E. Mustafin et al., NIM A510, 199 (2003))

7. ICFA Workshop, December 9-12, 2003 Andreas Krämer - GSI Darmstadt7 Fit Results for Lifetime Measurements of U 28+ injected ion current [mA] pumping speed [l/s per pump station]  charge exchange cross section [10 -20 m 2 ] desorption yield  initial pressure [10 -11 mbar] 1.081601.1200006.0 1.401200.82700014 1.971601.3160006.5 5.361502.11100010 1mA corresponds to 10 9 ions E. Mustafin et al., NIM A510, 199 (2003)

8. ICFA Workshop, December 9-12, 2003 Andreas Krämer - GSI Darmstadt8 Measurements @ SIS18

9. ICFA Workshop, December 9-12, 2003 Andreas Krämer - GSI Darmstadt9 Pressure Rise During Localized Beam Loss U. Weinrich et al., GSI Internal Report (2002)

10. ICFA Workshop, December 9-12, 2003 Andreas Krämer - GSI Darmstadt10 Fast Pressure Measurements S12 S01 S06 Continuous injection of 8.7 MeV/u 5  10 7 U 28+ ions every 1.8 sec  5200 U. Weinrich et al., GSI Internal Report (2002) 100 sec

11. ICFA Workshop, December 9-12, 2003 Andreas Krämer - GSI Darmstadt11 Experimental Setup for Ion Beam Induced Desorption Yield Measurements Experiments by: M. Bender (GSI) H. Kollmus (GSI) A. Krämer (GSI)

12. ICFA Workshop, December 9-12, 2003 Andreas Krämer - GSI Darmstadt12 Total Pressure Increase due to Desorption 1.4 MeV/u C 2+  Al, perpendicular incidence Continuous bombardment 1Hz, 9  10 10 ions/pulse Single shot 9  10 10 ions/pulse Single shot Continuous bombardment  ≈ 170  ≈ 110

13. ICFA Workshop, December 9-12, 2003 Andreas Krämer - GSI Darmstadt13 Total Pressure Increase due to Ion Beam Induced Desorption 1.4MeV/u 1.8-3.1·10 9 (1.9-3.3  A, 4ms) Pb 27+  stainless steel 304

14. ICFA Workshop, December 9-12, 2003 Andreas Krämer - GSI Darmstadt14 Partial Pressure Increase due to Ion Beam Induced Desorption 1.4MeV/u 1.8-3.1·10 9 Pb 27+  stainless steel 304 The measured ion current was corrected for the ionization probabilities of the different gases: H 2 : x2.3 CO: x0.95 CO 2 : x0.71 CH 4 : x0.625  Desorption dominated by H 2 (87%) and CO (11%)

15. ICFA Workshop, December 9-12, 2003 Andreas Krämer - GSI Darmstadt15 Single Shot Results of Desorption Yield Measurements at GSI [M. Bender, H. Kollmus, A. Krämer (GSI UHV group)] Energy: 1.4 MeV/u, Intensities: 10 9 – 10 11 ions per pulse, perpendicular incidence The calculated desorption yields are not corrected for the "real" gas composition, which is H 2 dominated. Therefore the desorption yields are underestimated by a factor of about 2.

16. ICFA Workshop, December 9-12, 2003 Andreas Krämer - GSI Darmstadt16 Experimental Set-Up with additional CERN hardware high current injector (HLI) 1.4MeV/u Zn 10+ Experiment by: E. Mahner (CERN) M. Bender (GSI) H. Kollmus (GSI) A. Krämer (GSI) CERN B.A.G. CERN R.G.A. GSI R.G.A. GSI gauge

17. ICFA Workshop, December 9-12, 2003 Andreas Krämer - GSI Darmstadt17 Latest Experiment with Zn 10+ at 1.4MeV/u CERN Samples by Edgar Mahner

18. ICFA Workshop, December 9-12, 2003 Andreas Krämer - GSI Darmstadt18 Target Holder with CERN Samples [pictures by G. Otto (GSI)]

19. ICFA Workshop, December 9-12, 2003 Andreas Krämer - GSI Darmstadt19 Desorption Yields calculated out of Single Shot Experiments 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 Desorption yields are calculated with: assuming S=5.52l/s (N 2 equivalent)  p was measured with an extractor ion gauge. 1.4MeV/u Zn 10+

20. ICFA Workshop, December 9-12, 2003 Andreas Krämer - GSI Darmstadt20 Desorption Yields Calculated from Scrubbing Plots by E. Mahner (CERN) 1.4MeV/u Zn 10+ Mainly desorbed gases are H 2 and CO.

21. ICFA Workshop, December 9-12, 2003 Andreas Krämer - GSI Darmstadt21 Pulse Length and Frequency Dependence of Partial Pressures Rate [Hz] Pulse length [ms] 10.49 12 14 15.5 2 6.255.5 105.5 255.5 Intensity dependence of  : linear? new effects at high intensities? Plot by E. Mahner (CERN) 1.4 MeV/u Zn 10+  TiZrV/316LN (fired)

22. ICFA Workshop, December 9-12, 2003 Andreas Krämer - GSI Darmstadt22 Pulse Length and Frequency Dependence of Partial Pressures 1.4 MeV/u Zn 10+  316LN (fired) Plots by E. Mahner (CERN) Flux vs  p 0.05.0x10 11 1.0x10 12 1.5x10 12 1.0x10 -8 3.0x10 -8 4.0x10 -8 2.0x10 -8 6.0x10 -8 7.0x10 -8 5.0x10 -8 8.0x10 -8 Flux [ions/s] 0.0 25Hz 10Hz 8.33Hz 6.25Hz 4.17Hz 2Hz 5.5ms 4ms 5.5ms 3ms 2ms 1ms 0.49ms 1Hz 5.5ms

23. ICFA Workshop, December 9-12, 2003 Andreas Krämer - GSI Darmstadt23 Beam Scrubbing 1.4 MeV/u Zn 10+  304 Plot by E. Mahner (CERN) ° H 2 ° CH 4 ° H 2 O ° CO ° O 2 ° CO 2 Scrubbing effect for CO stronger than for H 2 1Hz, 5.5ms pulse length  4x10 10 ions/pulse Dose [ions/s/cm 2 ]2.9x10 12 2.9x10 13 2.9x10 14

24. ICFA Workshop, December 9-12, 2003 Andreas Krämer - GSI Darmstadt24 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 1  m 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

25. ICFA Workshop, December 9-12, 2003 Andreas Krämer - GSI Darmstadt25 Elastic Recoil Ion Detection Analysis (ERDA) E 1 Z 1 m 1 E 2 Z 2 m 2 ERDA-Cross Section: for heavy ions: m 2 /m 1 << 1  all recoil ions have approx the same velocity v (  similar energy loss) same sensitivity for all elements Z 1 4 dependence ( m=2Z ) depth profile easy accessible Rutherford-Scattering:  Sample Ion Beam Recoil Ion

26. ICFA Workshop, December 9-12, 2003 Andreas Krämer - GSI Darmstadt26 Cathode Anode (  E) Lattice PIN-Diode (E rest ) Window  E : Element (Z) E rest : Depth t D : Emission Angle (  ) tDtD UHV environment Ion Beam Recoil Ion Sample Experimental Setup for ERDA Measurement H. D. Mieskes et al., Measuring sputtering yields of high energy heavy ions on metals, NIM B 146 (1998)

27. ICFA Workshop, December 9-12, 2003 Andreas Krämer - GSI Darmstadt27 E res EE C O N 200 MeV Au  304 L stainless steel in-situ ERD energy profile of O-contamination in a Ti - sample ERDA-Spektra H. D. Mieskes et al., NIM B 146 (1998)

28. ICFA Workshop, December 9-12, 2003 Andreas Krämer - GSI Darmstadt28 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

29. ICFA Workshop, December 9-12, 2003 Andreas Krämer - GSI Darmstadt29 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)