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Booster Synchrotron Cavities: An Overview in the Context of PIP

Booster Synchrotron Cavities: An Overview in the Context of PIP. Mohamed Hassan , Timergali Khabiboulline , Vyacheslav Yakovlev 07/03/2013. Fermilab’s Booster Parameters. The Fermilab Booster is a synchrotron that accelerates protons from 400 MeV to 8 GeV

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Booster Synchrotron Cavities: An Overview in the Context of PIP

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  1. Booster Synchrotron Cavities: An Overview in the Context of PIP Mohamed Hassan, TimergaliKhabiboulline , VyacheslavYakovlev 07/03/2013

  2. Fermilab’s Booster Parameters • The Fermilab Booster is a synchrotron that accelerates protons from 400 MeV to 8 GeV • The Booster circumference is 474.2 meters, the magnetic cycle is a biased 15 Hz and the RF operates at harmonic 84 of the revolution frequency

  3. Proton Improvement Plan • Objectives: Increase the Proton Source throughput while maintain good availability and acceptable residual activation through 2025. S. Hederson, Dec 2010 • Goals: • PIP should enable Linac/Booster to • deliver: 1.80E17 protons per hour (12 Hz) by May 1, 2013 • deliver 2.25E17 protons per hour (15 Hz) by January 1, 2016 • while maintaining Linac/Booster availabilty > 85% and residual activation at acceptable levels and ensuring a useful operation life of the proton source through 2025. S. Hederson, Dec 2010 S. Henderson, Accelerator Advisory Committee, Nov. 7-9, 2011

  4. Specifications for Design of New Accelerating Cavities for the Fermilab Booster

  5. Brainstorming

  6. Slow versus Fast Frequency Tuning

  7. Ferromagnetic Tuning • Classical way of tuning microwave components using bias current that will change the permittivity of the material

  8. Parallel Biased Cavities • Bias Field is Parallel to the RF Field • Ferrites with High Saturation Magnetization (Ni-Zn) • Larger values of Mu (Larger Losses, Lower Q) • Relatively limited by the heating in the ferrites • Gradient is limited also by voltage breakdown in air h H

  9. Perpendicular Biased Cavities • Bias Field is Perpendicular to the RF Field • Ferrites with Relatively Low Saturation Magnetization (Mn-Zn) • Smaller values of Mu (Smaller Losses, Larger Q) • Cooling is difficult • Some environmental hazards because of Beryllium Oxide • Only prototypes (up to our knowledge) H h rotating (on cone) magnetic vector – Gyromagnetic Resonance H=f/2.8

  10. Comparison Between Booster Cavities

  11. Tunable Booster Cavities H h h H

  12. Voltage Breakdown Measured • In Air ~ 3 MV/m (30 KV/cm) • In Vacuum (according to Kilpatrick) is ~ 10 MV/m (theoretical) 18 MV/m (measured) Theoretical Kilpatrick Theoretical Peter et. Al. W. Peter, R. J. Fael, A. Kadish, and L. E. Thode, “Criteria for Vacuum Breakdown in RF Cavities,” IEEE Transactions on Nuclear Science, Vol. Ns-30, No. 4, Aug 1983

  13. Max Field in Air Electric Field for 55KV Assumed 0.25” Blend Radius upon John Reid’s recommendation 1.7 MV/m

  14. Max Electric Field Electric Field for 55kV Electric Field for 60 kV 3.6 MV/m 3.3 MV/m 1.85 MV/m 1.7 MV/m

  15. Why Perpendicular Biased Cavity Could Achieve Higher Voltage Gradient? • Air fills most of the cavity volume (breakdown ~30 kV/cm) • Vacuum windows are nearby the gap • Tuner is filled with air • Vacuum fills most of the cavity volume (breakdown ~ 100 kV/cm) • Vacuum windows are right away on the tuner connection • Tuner is filled with dielectric

  16. Possible Changes to the Current Design • How about rounding the stem corners with large radius >0.25”? • How about enlarging the stem connection between the tuner and the cavity? • How about moving the vacuum window position? • How about filling the tuner with dielectric medium (though it might be a problem for cooling)? • How about designing a perpendicular biased tuner to be used with the current cavity? • How about using TRIUMF cavity (we have one somewhere here in FNAL)?

  17. Conclusion • Possible design changes have been identified • Major changes in the current tuner have been suggested • Perhaps TRIUMF cavity could be used as a test prototype for perpendicular-biased option

  18. Ferroelectric Booster Cavity? • High Q across the band ~1000 • Fast Response ~ ns • But 10% tunability • Need high voltage to be applied 50 kV/cm • Bias Circuit will be completely different • Conceptual, No Prototype • Very early developement • Would require quite involved development Newsham, D., N. Barov, and J. S. Kim. "RAPIDLY TUNABLE RF CAVITY FOR FFAG ACCELERATORS."

  19. Ferromagnetic Superconducting? • Uranium Compounds under Low Temperature& High Pressure • It might be a day that we see ferromagnetic superconducting cavities Aoki, Dai, and Jacques Flouquet. "Ferromagnetism and superconductivity in uranium compounds." arXiv preprint arXiv:1108.4807 (2011).

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