1 alternative bunch compressor 30 th sep. 2008 knu eun-san kim
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Alternative Bunch Compressor
30th Sep. 2008
KNU Eun-San Kim
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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, respecti
vely.
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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Designed lattice
locations of 4 skew quadrupoles
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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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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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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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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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Vertical alignment error in Q*
Without lattice correction With lattice correction
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0 200 400 600 800 1000
1
10
100
1000yom
y/ yo
RMS quadrupole vertical alignment error (m)
without correction with correction
Emittance vs. Q-Vertical alignment error
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Rotation error in Bending
Without lattice correction With lattice correction
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0 200 400 600 800 1000
1
10
100
yom
without correction with correction
RMS Bending rotation error (m)
y/ yo
Emittance growth vs. Bending rotation error
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Horizontal alignment error in Q*
Without lattice correction With lattice correction
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0 200 400 600 800 1000
1
10
RMS quadrupole horizontal alignment error (m)
x/ xo
xom without correction with correction
Emittance growth vs. Q-Horizontal alignment error
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Rotation error in Q*
Without lattice correction With lattice correction
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0 200 400 600 800 1000
1
10
yom
RMS quadrupole rotation error (m)
y/ yo
without correction with correction
Emittance growth vs. Q Rotation error
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Bending vertical misalignment error
Without lattice correction With lattice correction
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0 200 400 600 800 1000
1
10
yom
y/ yo
RMS Bending vertical alignment error (m)
without correction with correction
Emittance growth vs. Bending misalignment error
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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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0 50 100 150 2000.8
1.0
1.2
1.4
1.6
1.8
2.0
2.2
2.4
y/ yo
Number of Random Seed
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
0 50 100 150 2000.9
1.0
1.1
1.2
1.3
1.4
1.5
1.6
x/ xo
Number of Random Seed
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Effect of BPM offset error
Offset error of 300 m rms shows negligible emittance growth.
165 170 175 180 185 190 195 200
1.0
1.1
1.2
1.3
1.4
1.5
x/ xo
Number of Random Seed
without BPM offset with 300 m BPM offset
With 6 machine errors
165 170 175 180 185 190 195 2000.8
1.0
1.2
1.4
1.6
1.8
2.0
2.2
2.4 without BPM offset with 300 m BPM offset
Y/ Yo
Number of Random Seed
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Effects of ISR and CSR on emittances
At Chicane 1 At Chicane 2 x for 6 mm bunch length
x for 9 mm bunch length
CSR CSR 8.20 m 8.14 m
ISR ISR 8.43 m 8.66 m
CSR+ISR CSR 8.35 m 8.33 m
CSR CSR+ISR 8.45 m 8.62 m
CSR+ISR CSR+ISR 8.63 m 8.8 m
ISR is a main source to emittance growth.
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Fluctuation in bunch length
0 20 40 60 80 1000.94
0.96
0.98
1.00
1.02
1.04
1.06
Number of bunches
Re
latv
e b
un
ch
le
ng
th
1% rms voltage error 2% rms voltage error
0 20 40 60 80 1000.94
0.96
0.98
1.00
1.02
1.04
1.06
0.1 degree rms phase error 0.3 degree rms phase error
Number of bunchesR
ela
tve
bu
nc
h l
en
gth
100 successive bunches due to rf voltage jitter (left) and rf phase angle jitter (right).
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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.