Ring to Main Linac (RTML): Status and Plans ILC January Meeting (KEK) Peter Tenenbaum 19-Jan-2006

Peter Tenenbaum2 A Few Improvements The RTML is almost unchanged from the design described in the BCD There are a few changes which are proposed –Move boundary of Damping Ring section to include damping ring extraction region (DRX) Proposed boundary is at zero-dispersion point at end of DRX –Replace multi-wire emittance station in Emit1 with single wire or other profile device –Insert 610 m (approx) transfer line (DRStretch) to optimize DR position within site boundary –Remove skew correction section from Emit2 –Extend Linac Launch + diagnostic section (not quite long enough in BCD) –Remove first diagnostic section in main linac Redundant with last diagnostic station in RTML! This talk assumes that these changes will be accepted, and describes the changed system

19-Jan-2006Peter Tenenbaum3 RTML Footprint

19-Jan-2006Peter Tenenbaum4 Basis for Estimates of Lengths and Components Bunch compressors: lattice files of 3 rd generation designs from 2005 Other systems: scaling from TESLA or NLC lattices based on changes in beam parameters, if any –These estimates are necessarily rougher than the bunch compressors

19-Jan-2006Peter Tenenbaum5 System Lengths RegionLength Skew Correction35 m Collimation110 m DR Stretch610 m Turnaround170 m Spin Rotator80 m Emittance35 m BC1400 m BC21000 m Linac Launch60 m Total2500 m

19-Jan-2006Peter Tenenbaum6 Magnet Counts RegionBendsQuadsSextsCorrsFast Kickers Solenoids Skew Collimation DR Stretch Turnaround100 10?20000 SpinRot Emittance BC BC LinacLaunch Total ?600444

19-Jan-2006Peter Tenenbaum7 Instrumentation RegionBPMsWIREsPROFsBLMsPhase Skew170 or 11 or 001 Collimation DR Stretch Turnaround Spin Rotator Emittance BC BC Linac Launch Total30410 or 110 or 023

19-Jan-2006Peter Tenenbaum8 BC RF Systems BC1 has 3 cryomodules, 1 klystron, plus one spare klystron with waveguide switch BC2 has 57 cryomodules, 19 klystrons, of which 1 klystron + 3 cryomodules are spare Gradients modestly lower than 31.5 MV/m needed Stations operate far from RF crest –Need to change klystron amplitude and phase during train to compensate beam loading –Larger average power goes to RF loads than in main linac stations Phase and amplitude tolerances are tight –Phase jitter < 0.1°  2% loss of integrated luminosity from longitudinal jitter of collision point Most promising bunch length monitor requires crab cavity –Based on system prototyped at SPPS and TTF2 –Might need crab cavities for bunch length measurement, depending on downselect of BLM technology

19-Jan-2006Peter Tenenbaum9 Bunch Compressor Wiggler Each BC in baseline has 240 meters of bend magnets arranged in chicanes to generate compression –Long! Considering two approaches to reducing length –Enhancing R 56 by forcing nonzero D’ at quads –Replacing wiggler with 4-bend chicane with optimized lattice functions for emittance preservation Issue here is control of vertical dispersion and emittance growth from pitched cavities –Studies ongoing at this time

19-Jan-2006Peter Tenenbaum10 Beam Stops Current design has 3 –Low power (< 1 kW) insertable stopper Somewhere in skew correction or collimation section – need to find the best spot for it –Allows single-bunch tuneup of beams extracted from DR –Full power (220 kW and 660 kW) pulsed dumps after BC1 and in Linac Launch Allow bunch length tuneup without sending beam into next RF section Also may have machine protection role 3 possible modes of operation –Train-by-train, using pulsed bends –Intra train, with fast (100 nsec risetime) kickers –Bunch stealing – take 1 bunch out of train for diagnostic purposes (open to debate) Are these enough? Or possibly too much? Can we save money in pulsed systems by limiting their average power but allowing a large peak power? –Can take a full train for MPS occasionally, or a fraction of a train forever

19-Jan-2006Peter Tenenbaum11 Spin Dynamics Each side has 1 complete spin rotator Implications: –Can’t simultaneously run to 2 IRs with spin optimized in both Need 2 spin rotators per side –Can’t to train-to-train spin-flipping of positrons Would need either 2 or 4 spin rotators on positron side How important is this? Can we do it upstream of the DR? At 250 MeV?

19-Jan-2006Peter Tenenbaum12 Tunnels etc. Current assumption: RTML is laser- straight –Main linac is curved –Somewhere there must be dispersion matching between RTML and ML Two parts of RTML beamline (upstream of turnaround and downstream) share tunnel –Is that OK? Is it cost-optimal?

19-Jan-2006Peter Tenenbaum13 Collimation Assuming 2 phases x 2 planes x 1 iteration of collimation Spoiler survival probably not a problem –Large geometric emittances –Close to DR – can halt extraction quickly Collimated halo points at BC2 and BC1 RF stations –Is that OK? Assuming energy collimation in turnaround or bunch compressor wigglers

19-Jan-2006Peter Tenenbaum14 Progress since Frascati Work started on shorter BC wigglers and turnaround optics Leaders of all Technical and Global systems contacted –Notified about potentially interesting issues in the RTML –Dialogue begun – “What do you need from us, when do you need it, and with whom should we be corresponding?” –Most TS and GS have replied already!

19-Jan-2006Peter Tenenbaum15 Upcoming Milestones (Tentative Map) 20 Jan –Finalize boundaries and other changes described on Slide 2 29 Jan –Site layout, RF unit, PPS / MPS issues finalized Impact DR Stretch and other areas 12 Feb –Complete optics for turnaround –Complete optics for collimation system –Complete optics for BC wigglers 26 Feb: –Complete optics for pulsed dumplines –Select BLM technology (or technologies)

19-Jan-2006Peter Tenenbaum16 Milestones (2) 12 Mar: –Complete all optics –Select size monitor technology for Skew section 22 Mar: –Attend Sisters of Mercy Warfield in San Francisco 27 Mar: –Complete system integration of lattices (“Woodley- fication”) April: –Review RTML design and place lattices and documentation under change control