Beam Delivery update Andrei Seryi December 12, 2005 Snowmass 2005 Beam Delivery update Andrei Seryi adapted from the talk on GDE meeting last week, will skip most of slides December 12, 2005 GDE Meeting at INFN-LNF

Plan of the talk List, very briefly, topics where progress were made after Snowmass Describe in more details R&D progress in areas relevant to IR configuration Describe ranking of IR configurations Present example, where evaluation is ongoing and ranking is still being discussed Outline plans for the next year If time left (unlikely), comment in more details about design progress in some of the areas

Snowmass Baseline & Alternatives Baseline (supported, at the moment, by GDE exec) two BDSs, 20/2mrad, 2 detectors, 2 longitudinally separated IR halls Alternative 1 two BDSs, 20/2mrad, 2 detectors in single IR hall @ Z=0 Alternative 2 single IR/BDS, collider hall long enough for two push-pull detectors 2006 => will work on design and cost of baseline, choose IR configuration (20,14,2,0mr) of Alternative 2 and cost it

Design and R&D progress since Snowmass (1) Evaluate possibility to remove full power tune-up dumps Collimation optimization, calc. of wakes & beam damage Prepare ESA (BDS instrumentation & IR facility) run at SLAC ATF2 design, fabrication of hardware, collaboration Work with detector concepts to minimize solenoids leakage Optimize DID field shape to be more TPC friendly Introduced anti-DID to minimize pairs background Work on linac and BDS stability criteria (with WG1) Optimize self shielded compact SC quad design, produce a prototype and make successful experimental test at BNL … ESA = End Station A at SLAC ATF2 = Accelerator Test Facility -2 at KEK DID = Detector Integrated Dipole anti-DID = DID with reverse sign of the field TPC = Time Projection Chamber

Design and R&D progress since Snowmass (2) Consider effects of e+ source location Work on diagnostics system optimization & laser wire requirements Continue crab cavity design study, plan phase stability tests in UK Evaluate effects of parasitic crossings in head-on case Study of beam-cal performance to detect small angle tagging electrons Studying losses in extraction line for various design, parameters and study effects on diagnostics & IR background Continue work on forward region optimization Study of beam-beam and pair productions, EM deflection effect on Bhabha scattering …

Intermediate crossing angle At Snowmass, WG4 suggested to study intermediate crossing angle and asked 2-3month to complete design Motivations for intermediate crossing angle Snowmass discussion of single IR With two IRs, one of them may be more risky for machine performance in expectation of better backgrounds and hermeticity With single IR configuration, need to put the overall performance, reliability and operability on the first place With one IR the optimal baseline may be neither 20mr nor 2mr Optimization of detector performance while minimizing risk “…would be interested in the smallest crossing angle that does not compromise downstream E and P measurement, does not increase backgrounds, does not significantly increase the risk of backgrounds, and does not reduce the reliability of the machine … . This may well be more than 2 and less than 20 mrad…” [SiD] Technical possibility to reduce the angle with compact BNL quads At Nanobeam 2005 in October, presented complete 14mrad design including IR magnets, extraction optics, IR optimization & background reduction, civil considerations & upgrade paths

Compact quad design developments

IR with self shielding quads

Tests of short prototype of SC quad

Tests of self shielded quad at BNL Test quad Rotating coil to measure the field is inside this brass tube The cancellation of the external field with a shield coil has been successfully demonstrated in a recent test at BNL

DID and anti-DID Detector Integrated Dipole= Dipole coils wound on detector solenoid, giving small sine-like transverse field (anti-)DID allows aligning the detector solenoid field lines along the (outgoing) incoming beam trajectory => anti-DID effectively zeroes the crossing angle for the outgoing beam and pairs, while the effective angle for the incoming beam is increased 1.5-1.6 times Decreased SR, in 14mrad, ease the use of anti-DID

Field lines in LDC Pairs: High E Low E Fringe and internal field of QD0 not included

Field lines in LDC with anti-DID Pairs: High E Low E

DID/ anti-DID field shape for detectors with TPC Field in the central region is flattened with two DID coils (short and long) whose currents are properly adjusted, to ease TPC calibration Suggestion that flattening the field in central region would ease TPC calibration came from Dan Paterson in discussion with Witold Kozanecki

Pairs in LDC with DID & anti-DID apertures: Incoming Extraction anti-DID

Photons into Tracker Pair energy into BeamCal is smaller in 14 mrad crossing. Anti-DID can further reduce the energy to the 2 mrad crossing level. # of secondary photons generated in BeamCal is also smaller. # photons/BX into Tracker 14 mrad + DID + Anti-DID 2 mrad 1800 1900 830 720 Takashi Maruyama

“ From physics points of view, the effect of crossing angle is mainly low angle tagging and beam background (they are correlated).   AntiDID seems to reduce the background for large crossing angle case to the same level for the small angle crossing case, so the crossing angle is not a large factor in physics cases - provided that the AntiDID works (including TPC). ” from Hitoshi Yamamoto, November 15, 2005

Ranking of BDS Configurations Rank 1 - directly affecting energy and luminosity reach, background, and precision measurements of beam properties or a single point failure Rank 2 - may affect energy, luminosity and background indirectly, e.g. via reliability of operation (integrated luminosity) Rank 3 - affecting only cost, difficulty of R&D and difficulty of the design Special Rank – compatibility with other physics programs and upgrades (Relative weight of this category should be discussed and determined by the whole community): http://www-project.slac.stanford.edu/ilc/acceldev/beamdelivery/bds_bcd_acd.htm#ir_configs_rank

Rank 1 – directly affecting energy and luminosity reach, background and precision measurements of beam properties, or a single point failure: Luminosity reach – best 14 and 20mr, worst 2mr and head on Crab-crossing – best head-on, then 2mr, then 14mr, worst 20mr Fast feedback hardware and its integration into IR  – best 20 and 14mr, then head-on, worst 2mr Hermeticity & min veto angle – best head-on and 2mr, then 14mr, worst 20mr Pairs background – best head-on, 2mr and 14mr, worst 20mr Flexibility of extraction optics and possibility of downstream diagnostics – best 20 and 14mr, then 2mr, worst head-on Losses and background conditions in downstream diagnostics – best 20 and 14mr, then 2mr, worst head-on Losses in extraction affecting IR background - best 20 and 14mr, worst 2mr and head-on

Rank 2 – may affect energy, luminosity and background indirectly, e. g Rank 2 – may affect energy, luminosity and background indirectly, e.g. via reliability of operation (integrated luminosity): Parasitic crossings – best 20,14,2mr, worst head-on Vertical orbit correction in IP – best head on and 2mr, then 14mr, worst 20mr Tracking, in particular TPC operation and calibration – best head on and 2mr, worst 14 and 20mr Radiation in solenoid field – best head on and 2mr, then 14mr, worst 20mr Extraction line clearance for beamstrahlung photons – best 20 and 14mr, worst head-on and 2mrad Photon losses in FD, direct sight to vertex – best 20,14 and head-on, worst 2mr Extraction devices affecting MPS – best 20,14, worst 2mr and head on Extraction devices affecting collision stability – best 20,14 & 2mr, worst head-on

Rank 3 – affecting only cost, difficulty of r&d and of the design: Difficulty of final doublet magnets – best 20 and 14mr, then head-on, worst 2mr Length of extraction line – best 20 and 14mrad, worst 2mr and head on Difficulty of final doublet integration in detector – best 20, 14mr and head on, worst 2mr Special extraction magnets – best 20 and 14, then head on, worst 2mr Special coils for detector solenoid – best 2mr and head-on, worst 14 and 20mr

Special Rank –compatibility with other physics programs and upgrades Compatibility with gamma-gamma – best 20mr, worst head-on, 2mr, 14mr Compatibility with e-e- – best 20 and 14mr, then head-on, worst 2mr Compatibility with multi-TeV – best 20mr and 14mr, worst head on and 2mr

Ongoing work and discussion (rank 1) Luminosity reach – best 14 and 20mr, worst 2mr and head on In 2mr and head-on, to extract the disrupted beam, it is bent by a separator, rf kicker or field off-center of the final quadrupole. Large energy spread of disrupted beam causes beam losses and limits the luminosity reach by more than a factor of two in comparison with 20 and 14mr Luminosity reach for considered versions 20/14mr: all parameter sets work except 1TeV High Lumi (alternative 1TeV High L works OK) 2mr: problems with Large Y, Low P, High Lum for 500GeV CM, Large Y, Low P, High Lum, High Lum Alternative 1TeV CM head-on: does not work for Low Q (parasitic crossings), other sets not evaluated, issues likely for low P and high L Discuss with detector community the relative merits of parameter sets with larger beamstrahlung and disruption

Ongoing work and discussion (rank 1) Crab-crossing – best head-on, then 2mr, then 14mr, worst 20mr No need for crab cavity in head-on Small to moderate luminosity loss (5%, 10% or 30% for low Q, nominal or large sigma Y parameters) in 2mr without crab cavity… Crab cavity is essential for 14 or 20mr. Luminosity loss without crab cavity is 60-75-90% in 14mr and 75-85-95% in 20mr (for low Q, nominal or large sigma Y parameters) Warm transverse cavities are in use now, SC cavities are not yet. A deflecting SC CKM cavity is being built at FNAL. Crab cavity system can be built and experimentally verified during TDR phase, before start of ILC operation.

Ongoing work and discussion (rank 1) Fast feedback hardware and its integration into IR  – best 20 and 14mr, then head-on, worst 2mr In 20 and 14mr, feedback BPMs and kickers do not see other beam In head-on with shared aperture, BPM sees other beam and need to be directional, there may be losses of low energy beam tail on the kicker. In 2mrad, the feedback BPM has to be placed in front of FD, where disrupted beam envelope is still small, there is offset of outgoing beam in the BPM, the kicker should be large aperture, there are potential losses on the kicker. Performance of IP feedback, with all effects of beam losses included, is difficult to guarantee from simulations (which have advanced significantly) or from simplified beam tests. Eventual verification cannot be done before start of ILC operation.

Summary & plan for the next year Since Snowmass, a lot of progress in all areas Next year, will continue design, … Choose IR configuration for single IR case Consider in more details optimization for push-pull Consider upgrade paths to two IRs in more details Cost the baseline and single IR alternative Consider possibilities to reduce the cost further Consider optimization of 500GeV stage while keeping 1TeV reach