1. RHIC electron cloud and vacuum pressure rise characteristics P.He, H.C.Hseuh, W.Fischer, U.Iriso, D.Gassner, J.Gullotta, R.Lee, L.Smart, D.Trbojevic, L.F.Wang and S.Y.Zhang The 13 th ICFA Beam Dynamics Mini-Workshop Beam Induced Pressure Rise in Rings

2. Outline Part I: Residual gas composition during RHIC pressure rise Part II: Solenoid field effect on RHIC e-cloud

3. Accelerator Complex G10 G12 G8 G6 G4 G2

4. Two type of pressure rises observed at RHIC 2003 run *the beam transition pressure rise for ions *the electron cloud induced pressure rise at the injection The residual gas composition during multipacting and its evolution along the pressure rise is very helpful toward our understanding in this critical issue

5. Gas Composition and its Evolution along the Pressure Rise(G2)-Beam Transition Pressure Rise H2 CO H2O 1 min

6. More Concern about Gas Composition and its Evolution along the Electron Cloud induced pressure rise at the injection We will focus on that!

7. Gas Composition and its Evolution along the Pressure Rise(G2) S.Y.Zhang 5 mins

8. Gas Composition and its Evolution along the Pressure Rise(G12) H2 CO H2O Beam Intensity CCG: 1e-10 to 1e-7 torr 10 mins

9. Gas Composition and its Evolution along the Pressure Rise(G4) H2 CO H2O Beam Intensity CCG: 1e-9 to 3e-7 torr 10 mins

10. Gas Composition and its Evolution along the Pressure Rise(G8) H2 CO H2O Beam Intensity CCG: 3e-11 to 1e-8 torr 10 mins

11. Residual Gas Spectrum, during multipacting (CERN) Different scale respect to the above figure, where peak 2(H2) and 28 have been omitted, to show the behaviour of the peak 18(H2O ) H2 CO H2O CO2 30 mins

12. Extensive studies at CERN have shown that water vapour plays an important role in the contribution of the SEY. It is possible that the presence of water molecules increases the sticking probability for other gases. In-Situ SEY Measurement (CERN) N.Hilleret

13. RHIC Installed 11 x 5.2m x 12cmΦ TiZrV coated pipes this summer coated by SAES Getters with license from CERN at Q3-Q4 with high P during d-Au runs yo1, bo2, yi2(2), bi9(2), yi10(4), ip12 TiZrV NEG coating pipes

14. New Components for 2004 Run

15. A. Rossi NEG still pumping H2 CO CH4

16. Evidence of NEG saturation A. Rossi H2 CO CH4

17. CO H2 G12-PWX G12-PW1 G11-PW1 G11-PWX Run 2004: one NEG pipe at G11 RGA CC Gauge

18. Comparison with Run 2003: no NEG pipe at G11 G12-PWX G12-PW1 G11-PWX G11-PW1 Beam Intensity

19. Run 2004: four NEG pipes at YI10 H2 CO Enlarge this area Beam Intensity CCG RGA CCG

20. Run 2004: two NEG pipes at YI2 RGA CCG Beam Intensity

21. Part I: Residual gas composition during RHIC pressure rise Part II: Solenoid field effect on RHIC e-cloud

22. Noise level Electron Energy Spectrum Ubaldo

23. Solenoid Field Effect(1)-May 30 L.Smart CCG Beam Intensity CCG Beam Intensity Solenoid ED

24. Solenoid Field Effect(2)-May 09

25. Cyclotron Resonance at RHIC? Cyclotron frequency does not match bunch spacing -further study needed Cyclotron Resonance Condition SLAC-PUB-9813 M.Pivi

26. B - Sweep during fill #3812. (N=1.5 10 10 p-pb). Even at the maximum value of B, V ED is only reduced by a factor of ~3 (not enough to fully suppress the cloud). ~in RHIC we have ~7% solenoids covering, Maybe more solenoid needed in the future. Solenoid Field Effect(3) B can help to fully suppress the e-cloud during fill #3530. (N=1.1 10 10 p-pb).

27. PSR : EC was reduced by a factor ~50 by ~20G solenoid field. However, there was no measurable effect on the instability threshold when weak solenoids covering ~10% of the ring circumference were excited. R.Macek

28. Y. Suetsugu KEK PF:

29. Non-uniform Solenoid Field (Opposite Polarity) Uniform Solenoid Field (Equal Polarity) Y. Suetsugu

30. Solenoid Field Effect(4) From the simulation, we can see no electron in the center of the beam pipe if we use equal polarity solenoid field Run 2004, RHIC solenoid in equal polarity

31. Solenoid at RHIC tunnel & Solenoid PS

32. Conclusions and Future Works Evidence that solenoid will help to reduce the electron cloud build up Residual gas spectrum show electron stimulated desorption due to multipacting Improve electron detector design Verify experimentally the effectiveness TiZrV NEG coating to reduce the electron cloud build up after activated at 250°C(  max ~ 1.1 ) and also after saturation (  max <1.2~1.3 ) More solenoid(~30%), more NEG pipes(~300m), in-situ SEY measurement