wg3b damping ring
DESCRIPTION
WG3b Damping ring. K. Ohmi. Beam parameters in the damping ring. Lattice. TESLA, OTW OCS. Fill pattern (500MHz 650MHz). Aperture. Vertical emittance and misalignment. Design e y =20 nm. Resistive wall impedance. - PowerPoint PPT PresentationTRANSCRIPT
WG3b Damping ring
K. Ohmi
Beam parameters in the damping ring
Lattice
• TESLA, OTW OCS
Fill pattern (500MHz 650MHz)
Aperture
Vertical emittance and misalignment
• Design y=20 nm
Resistive wall impedance• Resistive wall wake integrated along the ring with
considering chamber radius and beta function.
Broad band impedance• Longitudinal
• Transverse
Single bunch instability
• Longitudinal unstable, bu
nch lengthing
• Transverse stable
Coupled bunch instability• Transverse bunch by bun
ch feedback system, 15 turn.
• Longitudinal, no problem (KEKB type SC cav.).
Intrabeam scattering
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
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
Ion cloud effect
• Mini gap,• Growth time ~10 turn.• Tune shift.
Kicker• Rise/fall time ~3ns is achieved for a
conventional strip-line kicker.• Base line: strip-line, alternative: RF sep. Fourier.
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
Circumference
Alt. Base line