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Alternative Bunch Compressor

Explore the error-tolerant system of the Alternative Bunch Compressor for emittance tuning and control, featuring lattice locations, parameters, and performance studies. Learn about the dispersion and orbit corrections, alignment errors, and effects of machine errors. Discover the impact of random seed numbers, BPM offset errors, ISR, CSR, and RF voltage and phase angle jitters on emittance growth.

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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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