Overview of Design Issues
17th KEKB Accelerator Review
Feb. 20, 2012
Haruyo Koiso

Parameters2011 Feb.
HER no wiggler

2012 Feb.
HER 60% wigglers

Energy (GeV) (LER/HER)

4.0/7.00729

4.0/7.00729

βy* (mm)

0.27/0.30

0.27/0.30

βx* (mm)

32/25

32/25

εx (nm)3.2/5.3

3.2/4.6

εy /εx (%)

0.27/0.24

0.27/0.28

σy(nm)

48/62

48/62

0.0897/0.0807

0.0881/0.0801

σz (mm)6/5

6/5

Ibeam (A)3.6/2.6

3.6/2.6

Nbunches

2500

2500

Luminosity (1034 cm‐2 s‐1)8080

ξyHER εx with 60% wigglers is used as the nominal value.
Lower HER εx can relax some other parameters (βx/y*, εy /εx , etc. ).
At present, larger εy /εx in HER is adopted.

HER Wiggler Section

Oho Straight SecOon

beam
Reuse LER wiggler

RF section

・Decrease the horizontal emittance with wigglers.
・Only reuse LER wiggler magnets at T=0. (60%)
・Install more wigglers if possible. (40%)

IR Design•

Design of IR (magnets, vacuum chamber, beam backgroundestimation, collimation system, collision feedback system, etc)
has been improved.
–––––

•

Modeling of IR optics has also been improved by using 3D
magnetic field calculation.
–•

Iron yokes for 3 more superconducting quadrupoles (QC1LE,QC1RE, QC2RP)
More precise correction of higher multipoles
Optimization of solenoid field distribution
Optimization of physical aperture

Touschek lifetime is marginally kept to be ~600 sec.

Lattice design of IR (Tsukuba section + a part of arcs) isrequired to be finalized around the end of this fiscal year(March 31) to meet the construction schedule.
-> A. Morita, Ohuchi, Nakayama, Kanazawa, Funakoshi, et al.

Injection•The synchrotron injection (fully or partially) will be necessary
in HER because the transverse aperture is not sufficiently large
for the betatron injection.

•With the beam-beam interaction, simulations say thattransient vertical blowup occurs after the betatron injection
even in LER, which causes beam loss or background.
–•Optimization of phase space profile by octupole correctors may
cure this blowup.

Good qualities of injected beams with sufficient intensities areessential for stable operation with very short lifetimes.
––Overall (Touschek, luminosity and beam-gas) lifetime: LER/HER
360/373 sec, estimated by A. Morita.
Needs optimization of beam distribution in Linac/BT lines.

-> M. Yoshida, T. Kamitani, H. Ikeda, T. Mori, et al.

Error Correction•Estimation of error tolerance and development of optics
correction system have been in progress.
–Requirements for beam diagnostics and control system (numberof monitors, accuracy, speed, etc) are being decided step by step.

•Error tolerances of IR magnets ( vibration, ripple of power
supplies, etc) are very small. Realistic solution to maintain
good conditions of optics and collision should be developed.

•Sufficient correction and tuning knobs for optics correction
and luminosity tuning should be equipped.
––––

Correction winding of each quadrupole (0.5%)
Skew quadrupole windings of each sextupole (Δy ~ 1 mm)
Rotated sextupoles or skew sextupoles to correct chromatic couplingsetc.

-> H. Sugimoto, Y. Funakoshi, et al.

Example of Parameter Dependence

90%

90%
HER coupling
0.28 -> 0.329 %to keep ξy LER<0.09

Luminosity degradation depending on some parameters are not so steep.
We will find several ways to reach 90 % of the target luminosity.

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