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Advancements in Barrier RF Stacking Techniques for Proton Beam Acceleration at Fermilab

This presentation discusses innovative methods in Barrier RF stacking utilized during proton beam acceleration, presented at ICFA-HB2004. Key topics include the motivation and goals of the study, simulation results, experimentation with barrier RF systems, and methods to optimize proton delivery to targets at Fermilab. By proposing adiabatic and fast stacking techniques, researchers aim to significantly increase the number of protons per second leading to enhancements in both the Pbar and NuMI experiments. Contributors include teams from Fermilab, KEK, and Caltech.

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Advancements in Barrier RF Stacking Techniques for Proton Beam Acceleration at Fermilab

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  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. 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 ICFA-HB2004 Workshop, October 20, 2004

  3. Outline • Motivation • Goals and methods • Simulations • Barrier rf system • Beam experiments • Summary http://www-bd.fnal.gov/pdriver/barrier/ ICFA-HB2004 Workshop, October 20, 2004

  4. Collider Experiment Run2 Pbar target CDF D0 ICFA-HB2004 Workshop, October 20, 2004

  5. Neutrino Experiment NuMI ICFA-HB2004 Workshop, October 20, 2004

  6. Booster – the Bottleneck • The newMain Injectorcan accept25e12protons per Booster cycle. • However, the oldBoostercan only deliver5e12particles per cycle. Webber’s data in October 2000 Prebys/Lackey’s data in January 2004 ICFA-HB2004 Workshop, October 20, 2004

  7. 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) ICFA-HB2004 Workshop, October 20, 2004

  8. 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 ICFA-HB2004 Workshop, October 20, 2004

  9. 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 ICFA-HB2004 Workshop, October 20, 2004

  10. Two Types of Barrier Stationary barrier +V -V Moving barrier +V -V ICFA-HB2004 Workshop, October 20, 2004

  11. Adiabatic Stacking Simulation (K-Y. Ng) Measurement ICFA-HB2004 Workshop, October 20, 2004

  12. Fast Stacking Simulation: 2-Batch (courtesy K.Y. Ng) ICFA-HB2004 Workshop, October 20, 2004

  13. 2-Batch Stacking(cont…) ICFA-HB2004 Workshop, October 20, 2004

  14. Fast Stacking Simulation: 12-Batch (courtesy K.Y. Ng) ICFA-HB2004 Workshop, October 20, 2004

  15. 12-Batch Stacking(cont…) ICFA-HB2004 Workshop, October 20, 2004

  16. 12-Batch Stacking(cont…) ICFA-HB2004 Workshop, October 20, 2004

  17. 12-Batch Stacking(cont…) ICFA-HB2004 Workshop, October 20, 2004

  18. 12-Batch Stacking(cont…) ICFA-HB2004 Workshop, October 20, 2004

  19. 12-Batch Stacking(cont…) ICFA-HB2004 Workshop, October 20, 2004

  20. 12-Batch Stacking(cont…) ICFA-HB2004 Workshop, October 20, 2004

  21. 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) ICFA-HB2004 Workshop, October 20, 2004

  22. Fast Switch (Behlke) HTS 161-06-GSM Peak voltage 2  16kV Peak current 60 A Pulse width 300 ns Pulse spacing 0.4-11s Repetition rate 100 kHz Burst length 400 ms Burst rep rate 0.5 Hz Finemet Core (Hitachi) FT3M OD 500 mm ID 139.8 mm thickness 25 mm Inductance 56 H (per core) Resistance 190  (per core) Specifications ICFA-HB2004 Workshop, October 20, 2004

  23. Barrier RF System(cont…) Finemet core High voltage fast switch ICFA-HB2004 Workshop, October 20, 2004

  24. Finemet vs. Ferrite (4M2) ICFA-HB2004 Workshop, October 20, 2004

  25. Barrier RF System(cont…) Modulator Cavity ICFA-HB2004 Workshop, October 20, 2004

  26. Full-Bridge Push-Pull Bipolar Circuit 9:1 1:9 upstairs in the tunnel ICFA-HB2004 Workshop, October 20, 2004

  27. Bench Test Before tuning After tuning trigger current primary voltage gap voltage 6 kV ICFA-HB2004 Workshop, October 20, 2004

  28. Beam Experiment in the Main Injector RF voltage Beam intensity acceleration capture rebunch debunch squeeze ICFA-HB2004 Workshop, October 20, 2004

  29. Beam Experiment(cont…) Beam squeezing 6 kV Moving barrier Squeezing Squeezed ICFA-HB2004 Workshop, October 20, 2004

  30. Mountain View 1.6 s t 3.2 s Stacking off Stacking on ICFA-HB2004 Workshop, October 20, 2004

  31. More Mountain Views ICFA-HB2004 Workshop, October 20, 2004

  32. High Beam Intensity after Stacking 8.3e12 @120 GeV squeezing ICFA-HB2004 Workshop, October 20, 2004

  33. Try Even Higher Beam Intensity Beam intensity (10e12) 53 MHz RF voltage ICFA-HB2004 Workshop, October 20, 2004

  34. Emittance Simulation  ESME(2 x 5e12, final bunch after recapture, courtesy J. MacLachlan) Bucket size = 0.30 eV-s Bucket size = 0.35 eV-s ICFA-HB2004 Workshop, October 20, 2004

  35. Emittance Measurement – Injected Bunch Stationary bucket, beam intensity = 5.23e12, emittance = 0.13 eV-s ICFA-HB2004 Workshop, October 20, 2004

  36. Emittance Measurement – Stacked Bunch Low intensity High intensity Medium intensity ICFA-HB2004 Workshop, October 20, 2004

  37. Emittance Measurement – Accelerated Bunch Bunch width = 10 ns moving area factor = 0.45 Stationary bucket area = 1.6 eV-sbunch emittance = 0.72 eV-s ICFA-HB2004 Workshop, October 20, 2004

  38. 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 ICFA-HB2004 Workshop, October 20, 2004

  39. Questions?

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