1. Barrier RF Stacking Weiren Chou and Dave Wildman Fermilab, U.S.A. October 20, 2004 Presentation at the Proton Driver Session ICFA-HB2004, Bensheim, Germany, Oct 18-22, 2004

2. W. Chou ICFA-HB2004 Workshop, October 20, 20042 Barrier RF Study Group Fermilab-KEK-Caltech collaboration: Fermilab - D. Wildman, J. Griffin, K.Y. Ng, J. MacLachlan, C. Bhat, W. Chou KEK - A. Takagi, Y. Mori Caltech - H. Zhang, D. Michael Acknowledgement: Helpful discussions with Takayama’s group

3. W. Chou ICFA-HB2004 Workshop, October 20, 20043 Outline  Motivation  Goals and methods  Simulations  Barrier rf system  Beam experiments  Summary http://www-bd.fnal.gov/pdriver/barrier/

4. W. Chou ICFA-HB2004 Workshop, October 20, 20044 Collider Experiment Run2 Pbar target CDF D0

5. W. Chou ICFA-HB2004 Workshop, October 20, 20045 Neutrino Experiment NuMI

6. W. Chou ICFA-HB2004 Workshop, October 20, 20046 Booster – the Bottleneck  The new Main Injector can accept 25e12 protons per Booster cycle.  However, the old Booster can only deliver 5e12 particles per cycle. Webber’s data in October 2000Prebys/Lackey’s data in January 2004

7. W. Chou ICFA-HB2004 Workshop, October 20, 20047 Solution - Stacking  A solution is to stack two Booster bunches into one Main Injector RF bucket  This is possible because the Main Injector longitudinal acceptance (0.72 eV-s) is larger than the Booster beam emittance (0.13 eV-s)

8. W. Chou ICFA-HB2004 Workshop, October 20, 20048 Goals  Run2 – To increase protons per second (pps) on the pbar target by 100% Present: 5e12 every 2 sec Goal: 2 x 5e12 every 2 sec  NuMI – To increase pps on the NuMI target by 70% Baseline: 3e13 every 2 sec Goal: 2 x 3e13 every 2.333 sec

9. W. Chou ICFA-HB2004 Workshop, October 20, 20049 Two Methods  Adiabatic stacking:  Beam injected on-axis  Adiabatically compress the beam by moving rf barrier  Fast stacking:  Beam injected off-axis  Using two barriers, one stationary, another moving  Continuous injection and stacking  First proposed by J. Griffin

10. W. Chou ICFA-HB2004 Workshop, October 20, 200410 Two Types of Barrier Stationary barrier Moving barrier +V -V +V -V

11. W. Chou ICFA-HB2004 Workshop, October 20, 200411 Adiabatic Stacking Simulation (K-Y. Ng)Measurement

12. W. Chou ICFA-HB2004 Workshop, October 20, 200412 Fast Stacking Simulation: 2-Batch (courtesy K.Y. Ng)

13. W. Chou ICFA-HB2004 Workshop, October 20, 200413 2-Batch Stacking (cont…)

14. W. Chou ICFA-HB2004 Workshop, October 20, 200414 Fast Stacking Simulation: 12-Batch (courtesy K.Y. Ng)

15. W. Chou ICFA-HB2004 Workshop, October 20, 200415 12-Batch Stacking (cont…)

16. W. Chou ICFA-HB2004 Workshop, October 20, 200416 12-Batch Stacking (cont…)

17. W. Chou ICFA-HB2004 Workshop, October 20, 200417 12-Batch Stacking (cont…)

18. W. Chou ICFA-HB2004 Workshop, October 20, 200418 12-Batch Stacking (cont…)

19. W. Chou ICFA-HB2004 Workshop, October 20, 200419 12-Batch Stacking (cont…)

20. W. Chou ICFA-HB2004 Workshop, October 20, 200420 12-Batch Stacking (cont…)

22. W. Chou ICFA-HB2004 Workshop, October 20, 200422 Barrier RF System  Design goal:  6 kV wideband RF system  Two main components:  Cavity: made of Finemet cores (Hitachi, Japan)  Modulator: made of high voltage fast switches (Behlke, Germany)

23. W. Chou ICFA-HB2004 Workshop, October 20, 200423 Specifications Fast Switch (Behlke)  HTS 161-06-GSM  Peak voltage2  16kV  Peak current60 A  Pulse width300 ns  Pulse spacing0.4-11  s  Repetition rate100 kHz  Burst length400 ms  Burst rep rate0.5 Hz Finemet Core (Hitachi)  FT3M  OD500 mm  ID139.8 mm  thickness25 mm  Inductance56  H (per core)  Resistance190  (per core)

24. W. Chou ICFA-HB2004 Workshop, October 20, 200424 Barrier RF System (cont…) Finemet coreHigh voltage fast switch

25. W. Chou ICFA-HB2004 Workshop, October 20, 200425 Finemet vs. Ferrite (4M2)

26. W. Chou ICFA-HB2004 Workshop, October 20, 200426 Barrier RF System (cont…) ModulatorCavity

27. W. Chou ICFA-HB2004 Workshop, October 20, 200427 Full-Bridge Push-Pull Bipolar Circuit in the tunnelupstairs 9:1 1:9

28. W. Chou ICFA-HB2004 Workshop, October 20, 200428 Bench Test trigger current primary voltage gap voltage Before tuning After tuning 6 kV

29. W. Chou ICFA-HB2004 Workshop, October 20, 200429 Beam Experiment in the Main Injector capture debunch squeeze rebunch acceleration Beam intensity RF voltage

30. W. Chou ICFA-HB2004 Workshop, October 20, 200430 Beam Experiment (cont…) SqueezingSqueezed Moving barrier Beam squeezing 6 kV

31. W. Chou ICFA-HB2004 Workshop, October 20, 200431 Mountain View Stacking offStacking on t 1.6  s 3.2  s

32. W. Chou ICFA-HB2004 Workshop, October 20, 200432 More Mountain Views

33. W. Chou ICFA-HB2004 Workshop, October 20, 200433 8.3e12 @120 GeV squeezing High Beam Intensity after Stacking

34. W. Chou ICFA-HB2004 Workshop, October 20, 200434 53 MHz RF voltage Beam intensity (10e12) Try Even Higher Beam Intensity

35. W. Chou ICFA-HB2004 Workshop, October 20, 200435 Emittance Simulation  ESME (2 x 5e12, final bunch after recapture, courtesy J. MacLachlan) Bucket size = 0.30 eV-sBucket size = 0.35 eV-s

36. W. Chou ICFA-HB2004 Workshop, October 20, 200436 Stationary bucket, beam intensity = 5.23e12, emittance = 0.13 eV-s Emittance Measurement – Injected Bunch

37. W. Chou ICFA-HB2004 Workshop, October 20, 200437 Low intensity Emittance Measurement – Stacked Bunch High intensity Medium intensity

38. W. Chou ICFA-HB2004 Workshop, October 20, 200438 Bunch width = 10 ns moving area factor = 0.45 Stationary bucket area = 1.6 eV-s bunch emittance = 0.72 eV-s Emittance Measurement – Accelerated Bunch

39. W. Chou ICFA-HB2004 Workshop, October 20, 200439 Summary  A barrier RF system has been built and installed in the Main Injector  It has successfully stacked two Booster batches into one and reached 8.3e12 at 120 GeV, ~ 60% increase in beam intensity  There is large emittance dilution during stacking  Causing losses at the beginning of acceleration  Making bunch too long for pbar production  But not a problem for NuMI  A second system is under construction and will be used for fast stacking experiment

40. Questions?