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