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

2. 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. 3 Designed lattice locations of 4 skew quadrupoles

4. 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. 5 Longitudinal phase space Initial bunch length of 6 mm Initial bunch length of 9 mm Initial After chicane 1 After chicane 2

6. 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. 7 Considered machine errors Error Magnitude H-misalignment in Q 300  m rms V-misalignment in Q 300  m rms Rotation in Q 300  rad rms V-misalignment in B 300  m rms H-misalignment in B 300  m rms Rotation in B 300  rad rms

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

9. 9 Emittance vs. Q-Vertical alignment error

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

11. 11 Emittance growth vs. Bending rotation error

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

13. 13 Emittance growth vs. Q-Horizontal alignment error

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

15. 15 Emittance growth vs. Q Rotation error

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

17. 17 Emittance growth vs. Bending misalignment error

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

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

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

21. 21 Effects of ISR and CSR on emittances At Chicane 1At Chicane 2  x for 6 mm bunch length  x for 9 mm bunch length CSR 8.20  m 8.14  m ISR 8.43  m 8.66  m CSR+ISR CSR 8.35  m 8.33  m CSRCSR+ISR 8.45  m 8.62  m CSR+ISR 8.63  m 8.8  m ISR is a main source to emittance growth.

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

23. 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.