Download - WG3b Damping ring
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WG3b Damping ring
K. Ohmi
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Beam parameters in the damping ring
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Lattice
• TESLA, OTW OCS
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Fill pattern (500MHz 650MHz)
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Aperture
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Vertical emittance and misalignment
• Design y=20 nm
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Resistive wall impedance• Resistive wall wake integrated along the ring with
considering chamber radius and beta function.
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Broad band impedance• Longitudinal
• Transverse
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Single bunch instability
• Longitudinal unstable, bu
nch lengthing
• Transverse stable
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Coupled bunch instability• Transverse bunch by bun
ch feedback system, 15 turn.
• Longitudinal, no problem (KEKB type SC cav.).
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Intrabeam scattering
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Space charge effect• TESLA, no problem (the coupling bump is required).• OCS(6km), no problem• BRU(6km,3.7GeV), serious.• Structure resonances should be avoided.
TESLA OCS BRU
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Table 1. Electron cloud density near beam (m-3) before bunch passage, compared with threshold density for secondary electron yield 2,max=1.2.
SEY=1.2 TESLA MCH DAS 2 x OCS OCS BRU OTW PPA PEP-II LER KEKB LERLb,tot 695.2 1445.4 653.6 434.0 433.6 1445.4 460.0 767.2 86 102
BEND re 2.8E+10 2.8E+10 2.8E+10 3.9E+10 4.0E+11 4.0E+11 1.0E+11 8.0E+11re Lb/L 1.15E+09 2.54E+09 1.08E+09 2.77E+09 2.84E+10 9.13E+10 0.00E+00 0.00E+00 3.93E+09 2.70E+10Lquad,tot 200.0 310.8 323.2 177.5 177.5 254.4 148.1 153.6 174.4
QUAD re 8.0E+09 8.0E+09 8.0E+09 2.1E+10 3.0E+11 3.0E+11 8.0E+10re Lq/L 9.41E+07 1.56E+08 1.52E+08 6.10E+08 8.71E+09 1.21E+10 0.00E+00 0.00E+00 0.00E+00 4.63E+09Lsext, tot 100.0 100.8 22.4 96.0 96.0 100.8 60.0 22.4 41.6
SEXT re 8.0E+09 8.0E+09 8.0E+09 2.1E+10 3.0E+11 3.0E+11 8.0E+10(~Quad) re Ls/L 4.71E+07 5.06E+07 1.05E+07 3.30E+08 4.71E+09 4.77E+09 0.00E+00 0.00E+00 0.00E+00 1.10E+09
Lwig 417.4 441.0 432.9 196.0 196.0 441.0 144.0 92.8 96WIGG re 6.5E+11 6.5E+11 6.5E+11 1.2E+12 9.2E+12 9.2E+12
re Lw/L 1.60E+10 1.80E+10 1.65E+10 3.85E+10 2.95E+11 6.41E+11 0.00E+00 0.00E+00 0.00E+00 0.00E+00Ldrift,arc 499.2 499.2 499.2 5210.5 5210.9 4091.9 2410.9 1788.0 1372.8 2602.2
DRIFT re 4.0E+10 4.0E+10 4.0E+10 7.9E+10 3.0E+11 3.0E+11 8.7E+11 8.7E+11 1.5E+12(ARC) re Ld/L 1.17E+09 1.25E+09 1.17E+09 6.73E+10 2.56E+11 1.94E+11 6.51E+11 5.51E+11 0.00E+00 1.29E+12
Ldrift 15088.2 13137.8 15082.7 0.0 0.0 0.0 0.0 0.0 739.8DRIFT re 2.0E+09 2.0E+09 2.0E+09(LONG*) re Ld/L 1.78E+09 1.65E+09 1.77E+09 0.00E+00 0.00E+00 0.00E+00 0.00E+00 0.00E+00 0.00E+00 0.00E+00
L 17000.0 15935.0 17014.0 6114.0 6114.0 6333.5 3223.0 2824.0 2199 3016AVERAGE re,ave 2.02E+10 2.36E+10 2.07E+10 1.10E+11 5.92E+11 9.43E+11 0.00E+00 0.00E+00 3.93E+09 1.33E+12SOLEN ON re,ave 1.72E+10 2.07E+10 1.78E+10 4.22E+10 3.37E+11 7.49E+11 0.00E+00 0.00E+00 3.93E+09 3.40E+10
re,th (sim) 1.10E+11 3.00E+11 1.20E+11 1.40E+11 1.40E+11 3.00E+11 3.50E+11 3.26E+11 4.66E+11 3.64E+11
Electron cloud effect
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Ion cloud effect
• Mini gap,• Growth time ~10 turn.• Tune shift.
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Kicker• Rise/fall time ~3ns is achieved for a
conventional strip-line kicker.• Base line: strip-line, alternative: RF sep. Fourier.
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Other technical issues
• RF cavity frequency 500MHz, super (base) or normal (alt.)
• Wiggler super (base) or normal (alt.)• Magnet normal (base) or permanent
(alt.)• Vacuum choice of pipe radius, shape,
material, coating.• Instrumentation monitor, feedback
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Circumference
Alt. Base line