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Published byValentine McLaughlin Modified over 4 years ago

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

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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.

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3 Designed lattice locations of 4 skew quadrupoles

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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

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

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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.

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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

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

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9 Emittance vs. Q-Vertical alignment error

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10 Rotation error in Bending Without lattice correction With lattice correction

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11 Emittance growth vs. Bending rotation error

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

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13 Emittance growth vs. Q-Horizontal alignment error

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14 Rotation error in Q* Without lattice correctionWith lattice correction

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15 Emittance growth vs. Q Rotation error

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16 Bending vertical misalignment error Without lattice correctionWith lattice correction

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17 Emittance growth vs. Bending misalignment error

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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

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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

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

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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.

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

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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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