The IR lattice design and optimization of the dynamic aperture for the ring Yiwei Wang, Huiping Geng, Yuan Zhang, Sha Bai, Dou Wang, Tianjian, Jie Gao Institute of High Energy Physics (IHEP, Beijing) CEPC workshop IHEP, 11-12 Sep 2015 Yiwei Wang 23-27 Sep 2015 1
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The IR lattice design and optimization of the dynamic aperture for the ring Yiwei Wang, Huiping Geng, Yuan Zhang, Sha Bai, Dou Wang, Tianjian, Jie Gao.
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23-27 Sep 2015 1
The IR lattice design and optimization of the dynamic aperture for the ring
• As shown in beam-beam simulation, the luminosity are almost the same when y* increased from 1.2 mm to 3 mm.
• For the first try, we just refit the final transformer.– the parts other than FT are almost kept
L*=1.5my*=1.2mm
Yiwei Wang
L*=1.5my*=3mm
Design principle of final doublet• constraint R22=0, R44=0 at the exit of QF1
– point to parallel image on both x and y planes
– The real design just adjust the gradient a bit (less than 10%)
L* dl1 l2
QD0 QF1
L*, d, G1, G2y, x, R, B1, B2 y*, x*, ay, ax
l1, l2our main concern
Optimization of final doublet
L*=1.5m, G1=G2
• When G>200T/m– y decrease slowly with the increase of G– B increase almost linearly with G and independent of the space between
QD0 and QF1• Seems possible to reduce the gradient from 300T/m to 200T/m
– y slightly increased from -148 to -149 and B significantly decreased from 6.4 to 4.5 T with ay (7.88*10^-8 mrad) used in the pre-CDR
– With a more optimistic ay (5.33*10^-8 mrad), B could be further reduce to be 3.9 T
– need to check with a full IR lattice. At present we still work with G=300T/mL*=1.5m, G1=G2
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Local chromaticity correction• Add additional sextupoles next to the main one*
– Compensate the finite length effect (Lsext=0.3m)
Yiwei Wang
*A.Bogomyagkov et al.http://arxiv.org/abs/0909.4872
k=1, S1/S2=-0.1
• Adjust the phase advances between the final doublet and the sextupoles to minimize second order chromaticity – QD0 and VS1– QF1 and HS1
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Local chromaticity correction (cont.)
• residual functions are =6.6, =5.6 and second order dispersion is =-0.15 m
Yiwei Wang
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Lattice of the whole ring• Close the whole ring
– matching linear lattice function
Yiwei Wang
Dispersion suppressor and FODO cell in the ARC
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Tune vs. momentum deviation
• Adjust the tune to be .08/.22 (x/y)– determined by beam-
beam study• match Q’ to be ~0.5 with
the sextupoles in the ARC– Currently only 2 family
of sextupoles in the ARC
• Good region of ±1% in Dp/p
Yiwei Wang
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Dynamic aperture for the ring• without radiation damping, error of the magnets• Synchrotron motion included• Tracking with 3 times of damping time• Coupling factor =0.003 for emitty
– -2% (2x , 20y), 2% (1x , 7y)
Yiwei Wang
Result in Pre-CDR
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Optimization of the dynamic aperture
Yiwei Wang
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FFS_3.0mm_v0_Feb_2015
FFS_3.0mm_v1_Mar_2015
FFS_3.0mm_v2.2_Sep_2015
Remove 2 quads in FT
Additional sext at 1st image point
Reduce y in CCY Remove 2 quads
Yiwei Wang
Beta and tune vs. deltap
v1 v2.2v0
• Upper for FFS only and lower for the whole ring– Tune vs. deltap on vertical plane become very flat– Qx’ for FFS should be optimized in next step
Tianjian Bian, Feng Su, Ming Xiao, Zhe Duan, Gang Xu, Jie Gao, Qing Qin, Demin Chou, Kazuhito Ohmi, Yoshihiro Funakoshi, Yukiyoshi Ohnishi, A. Bogomyagkov, Luis Eduardo Medina Medrano
• Thanks for your kind help and beneficial discussion!
Yiwei Wang
23-27 Sep 2015 21
Thank you for your attention!
Yiwei Wang
23-27 Sep 2015 22
reserved
Yiwei Wang
23-27 Sep 2015 23
Comparison of y*=1.2 mm and 3 mm
• Strengh of sextupoles in IR reduced– For y*=1.2mm: k2vs = 17.2 , k2hs = 2.92 – For y*=3mm: k2vs = 10.58 , k2hs = 2.80
• Tune vs. momentum deviation for the ring
Yiwei Wang
y*=1.2mm y*=3mm
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Comparison of y*=1.2 mm and 3 mm
• With the real ring• DA for off momentum:
– For y*=1.2mm, the DA is almost zero for off momentum 2%– For y*=3mm, the DA has been extended to 2% region: