Issues of stability and ground motion in ILC Andrei Seryi SLAC October 17, 2005 Selected pages from: Full talk at

2 17 Oct 05 A.Seryi, SLAC ILC jitter goals discussion The large capture range (10s of  ) of fast feedback does not mean that larger jitter is allowed along the machine Many reasons why the jitter should be smaller that beam size –The need to minimize  due to collimator wake-fields, –to provide acceptable conditions for beam diagnostics, –to minimize jitter effects on dispersion free steering, etc. The edge of the comfortable range: jitter < 50%  –the 50% jitter at the end of main linac => 40nm jitter of linac quads BDS (w. nonlinear elements) is more sensitive than weak linac –criteria for BDS must be different, tighter than in linac –may allow beam jitter to grow to ~100% before FD FD contributes one to one to IP jitter, but less relevant –FD jitter of ~100nm should be OK –No active stabilization should be needed (position monitoring useful)

3 17 Oct 05 A.Seryi, SLAC Discussion of ILC simulation results Linac (driving criteria is jitter) –GM K or C is OK for linac –If GM K or C, then linac component vibration 50nm is a bit too high, wish it to be no more than 30nm BDS (driving criteria is luminosity) –GM K or C is too noisy for BDS, wish to be ~3 quieter –GM B is just fine for BDS, can allow ~3 worse –Component jitter 25nm too high for BDS, wish it would be < 10nm –For FD may allow several times larger, 100nm? Linac and BDS may have different specs for on-the-floor noise –the noise consist of ground noise + noise from nearby utilities, which are different in linac and BDS areas –BDS area may be located in a quieter place than linac average Goals for tunnel floor stability & add. component jitter: –Linac: up to gm K or C & up to 30nm –BDS: up to gm B*3 or gm C/3 & up to 10nm

4 17 Oct 05 A.Seryi, SLAC Summary ILC stability goals for the beam, site and hardware suggested beam jitter: –50%  at the end of linac (or in BDS diagnostics) –100%  at the end of BDS, before FD –several  at IP Tunnel floor stability (site + noise of nearby ILC equipment): –Linac area: up to gm K or C –BDS area: up to gm B*3 or gm C/3 Additional noise due to beamline components: –Linac area: up to 30 nm –BDS area : up to 10 nm –FD : up to ~100nm Need to discuss these goals, their feasibility and consequences Many other issues not discussed, e.g. long term stability…