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Crab crossing at KEKB

Crab crossing at KEKB. K. Ohmi, KEK Beam-beam workshop 2-4, July, 2007, SLAC. T. Abe, T. Agho, K. Akai, M. Akemoto, A. Akiyama, M. Arinaga, K. Ebihara, K. Egawa, A. Enomoto, J. Flanagan, S. Fukuda, H. Fukuma, Y. Funakoshi, K. Furukawa, T. Furuya, K. Hara, T. Higo, S. Hiramatsu,

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Crab crossing at KEKB

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  1. Crab crossing at KEKB K. Ohmi, KEK Beam-beam workshop 2-4, July, 2007, SLAC

  2. T. Abe, T. Agho, K. Akai, M. Akemoto, A. Akiyama, M. Arinaga, K. Ebihara, K. Egawa, A. Enomoto, J. Flanagan, S. Fukuda, H. Fukuma, Y. Funakoshi, K. Furukawa, T. Furuya, K. Hara, T. Higo, S. Hiramatsu, H. Hisamatsu, H. Honma, T. Honma, K. Hosoyama, T. Ieiri, N. Iida, H. Ikeda, M. Ikeda, S. Inagaki, S. Isagawa, H. Ishii, A. Kabe, E. Kadokura, T. Kageyama,K. Kakihara, E. Kako, S. Kamada, T. Kamitani, K. Kanazawa, H. Katagiri, S. Kato, T. Kawamoto, S. Kazakov, M. Kikuchi, E. Kikutani, K. Kitagawa, H. Koiso, Y. Kojima, I. Komada, T. Kubo, K. Kudo, N. Kudo, K. Marutsuka, M. Masuzawa, S. Matsumoto, T. Matsumoto, S. Michizono, K. Mikawa, T. Mimashi, S. Mitsunobu, K. Mori, A. Morita, Y. Morita, H. Nakai, H. Nakajima, T. T. Nakamura, H. Nakanishi, K. Nakanishi, K. Nakao, S. Ninomiya, Y. Ogawa, K. Ohmi, S. Ohsawa, Y. Ohsawa, Y. Ohnishi, N. Ohuchi, K. Oide, M. Ono, T. Ozaki, K. Saito, H. Sakai, Y. Sakamoto, M. Sato, M. Satoh, K. Shibata, T. Shidara, M. Shirai, A. Shirakawa, T. Sueno,M. Suetake, Y. Suetsugu, R. Sugahara, T. Sugimura, T. Suwada, O. Tajima, S. Takano, S. Takasaki, T. Takenaka, Y. Takeuchi, M. Tawada, M. Tejima, M. Tobiyama, N. Tokuda, S. Uehara, S. Uno, Y. Yamamoto, Y. Yano, K. Yokoyama, Ma. Yoshida, Mi. Yoshida, S. Yoshimoto, K. Yoshino, KEK, Oho, Tsukuba, Ibaraki 305-0801, Japan E. Perevedentsev, D. N. Shatilov, BINP, Novosibirsk, Russia

  3. Input Coupler Liq. Helium Vessel SUS Support Pipe Stub Support Notch Filter Coaxial Coupler RF Absorber 80 K Liq. Nitrogen Shield Copper Bellows Aluminum End Plate Aluminum End Plate Crab Crossing @ KEKB Crab Crossing can boot the beam-beam parameter higher than 0.15 ! K. Ohmi Head-on (crab) (Strong-strong simulation) Crossing angle 22 mrad Crab cavities were successfully produced and beam study has started in Feb. 2007. K. Hosoyama, et al

  4. Crab Cavities in the KEKB Rings 1 cavity per ring HER LER

  5. Single Crab Cavity Scheme • Beam tilts all around the ring. • z-dependent horizontal closed orbit. • tilt at the IP: • 1 crab cavity per ring. • saves the cost of the cavity and cryogenics. • avoids synchrotron radiation hitting the cavity.

  6. Crab cavity creates a dispersion, (x,px)=(’)z • Periodic solution at crab cavity. • Synchrotron radiation damping realizes an equilibrium orbit (closed orbit) and beam size with periodic condition. • (,') is transferred as • (,') is matched at IP as follow Remember the ordinary dispersion, (x,px)=(’)

  7. Parameterization of 6x6 revolution matrix K. Ohmi, K. Hirata, K.Oide, PRE 54, 751, 1994

  8. Crab Phase Scan (LER) V(z=0) gives a dipole kick. crab Horizontal orbit distortion by a crab kick measured with 453 BPMs. Dependence of the horizontal kick the crab cavity of the rf phase. The kick angles estimated from the orbit response agree well those from the setting voltage of the crab cavity by 3.6%.

  9. Beams has indeed tilted! - Observation with Streak Cameras (H. Ikeda et al, FRPMN035) inside of the rings outside of the rings longitudinal HER LER horizontal The streak camera

  10. H. Koiso Vcrab Scan (HER) Beam lifetime Vertical beam size Luminosity Ratio design 3.6 mrad

  11. HER Warmup to 300K LER IHER = 0.7 A, ILER = 1.3 A, L > 1034 with crab crossing. Crab cav. detuned

  12. 22 mrad crossing Head-on Working Point of Tunes We are here. HER Simulations give good guidelines. LER K. Ohmi, et al. Phys. Rev. ST Accel. Beams 7, 104401(2004)

  13. Achievable luminosity for various emittance cases

  14. Luminosity with/without crab cavity Ecloud? Ecloud?

  15. H. Koiso Specific Luminosity L18 H24 (3/11, 4/3) L18 H24 (4/10, 4/19) L24 H24 (3/29, 4/1) L24 H29 (6/14) No crab

  16. What we expect crab cavity? • Establish symmetry of the collision • Degree of freedom of the collision system is decreased to one for x->+0.5. • Vertical motion is decoupled, therefore vertical emittance growth become weak. • Motion in one degree of freedom is confined in KAM surface.

  17. Symmetry breaking source • Optimization with a large number of parameters • Offset Dx, Dy, Dx’, Dy’ • Twiss parameters, b(waist), Ri=1,4, hx,y, h’ x,y of each beam.

  18. Tolerance for twiss parameters • Tolerance of all parameters are individually in controllable range. 1 unit for KEKB tuning: r4=0.021,=0.00016 Difficulty for multi-parameters optimization

  19. Crossing Angle and Horizontal Offset Luminosity The luminosity should be significantly degraded by small errors in the crab crossing mode. Therefore it is important to keep both the crossing angle and the horizontal offset between two beams sufficiently small. The crossing angle was optimized by adjusting the crab kick voltage. The horizontal offset must be less than 20 m. The offset was maintained by an orbit feedback to keep the canonical beam-beam kick constant. The target position was determined by the offset scan.

  20. Effect on the beam-beam performance of the phase jitter of RF’s • Luminosity and beam size as functions of dx. • Correlation time of the jitter, 1 or 10 turns, is important for the degradation. • Since Q=200,000 and H=5120, the correlation time will be larger than 10 turns. • Tolerance is 0.05 degree.

  21. RF Phase Stability LER HER • Phase stability of the crab mode was better than the requirement with the rf feedback. • Slow stability below 1 Hz is shown above. • Independent measurement by a spectrum analyzer shows better than 0.01 deg for f > 2 kHz, 0.1 deg for 2 Hz < f < 2 kHz. • Backlash or friction exists in the coaxial tuner for the LER.

  22. LER x, y tune dependence x +s =integer These resonances have to be eliminated. Succeeded in some lattices, but not in some others. x -x =integer

  23. Most serious issue in the crab operation • Asymmetry for the horizontal offset • Beam life time is very short in a region of a horizontal offset. • This asymmetry can not be reproduced by the simulation. • We had a similar experience. Remember “egure”. • Banana shape of beam (D. Shatilov), or nonlinear? Long life time e- e+ Short life time

  24. Horizontal offset scan • The (HER) beam current seems to be limited by the short life time of the LER beam. • The (LER) beamlifetime is very asymmetric with respect to H offset. LER lifetime Collision center given by the beam-beam kick

  25. Beam-beam halo in simulation • Long term simulation by Gaussian weak-strong model. 500x106 particle turn Head-on 11 mrad Life time can be improved due to the crab cavity.

  26. Beam-Beam Simulation with lattice non-linearity • Luminosity drops (beam loss) abruptly at threshold strengths. • However, the threshold strengths are about 2 order higher than expected values.

  27. Summary • Crab cavity operation starts from Feb. 2007. • High current operation was succeeded, 1.3 A (e+) and 0.7 A(e-). • RF Phase fluctuation (20 sec period) was seen at high current operation due to the backlash in the coaxial tuner. The fluctuation is seen only in collision mode. Related to beam-beam? • Luminosity gain is not yet. • It seems to be essential for me to solve the asymmetry.

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