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Alternative Bunch Compressor

Alternative Bunch Compressor. 30 th Sep. 2008 KNU Eun-San Kim. Introduction. Alternative BC has two rf sections and two chicanes with 4 bending magnets each. Length of each bending was reduced from 6.8 m to 2.4. Bunch lengths of 6 mm rms and 9 mm rms can be

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Alternative Bunch Compressor

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  1. Alternative Bunch Compressor 30th Sep. 2008 KNU Eun-San Kim

  2. Introduction • Alternative BC has two rf sections and two chicanes with 4 bending magnets each. Length of each bending was reduced from 6.8 m to 2.4. • Bunch lengths of 6 mm rms and 9 mm rms can be compressed to 0.15 mm rms and 0.3 mm rms, respectively. • We performed the lattice tunings to control the emittance growths with machine errors. : It was shown that the system was error tolerant.

  3. Designed lattice locations of 4 skew quadrupoles

  4. Main parameters • Initial bunch length 6 mm 9 mm • Final bunch length 0.15 mm 0.3 mm • Final emittance (H/V) 8.6/0.02 8.8/0.02(9.1/0.2) • R56 in chicane 1 474.2 mm • R56 in chicane 2 50.8 mm • Initial beam energy 5 GeV 5 GeV • Final beam energy 13.2 GeV 14.5 GeV • Final energy spread(%) 2.4(2.6) 2.1(2.4) ( ) : 6.8 m bending magnet

  5. Longitudinal phase space Initial After chicane 1 After chicane 2 Initial bunch length of 6 mm Initial bunch length of 9 mm

  6. Emittance Tuning • Correction of vertical dispersion that is generated by skew components was performed by using of 4 skew-quadrupoles.  We performed both dispersion correction and orbit correction at the same time such that they have a minimum value.

  7. Considered machine errors

  8. Vertical alignment error in Q* With lattice correction Without lattice correction

  9. Emittance vs. Q-Vertical alignment error

  10. Rotation error in Bending With lattice correction Without lattice correction

  11. Emittance growth vs. Bending rotation error

  12. Horizontal alignment error in Q* Without lattice correction With lattice correction

  13. Emittance growth vs. Q-Horizontal alignment error

  14. Rotation error in Q* Without lattice correction With lattice correction

  15. Emittance growth vs. Q Rotation error

  16. Bending vertical misalignment error Without lattice correction With lattice correction

  17. Emittance growth vs. Bending misalignment error

  18. Lattice distortion due to 6 machine errors Growths of emittance : factors of 1.48 / 254 in H / V With lattice correction Without lattice correction Growths of emittance : factors of 1 / 1.04 in H / V

  19. Effect of random seed number With 6 machine errors 80 and 70 % of seed number shows emittance growth less than 10 % in x and y-direction.

  20. Effect of BPM offset error With 6 machine errors Offset error of 300 mm rms shows negligible emittance growth.

  21. Effects of ISR and CSR on emittances ISR is a main source to emittance growth.

  22. Fluctuation in bunch length 100 successive bunches due to rf voltage jitter (left) and rf phase angle jitter (right).

  23. Summary • Studies on performance, error tolerance and jitter of alternative BC are presented.  Results on emittance tuning in the alternative BC show that the system is error tolerant.

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