K. Yokoya 2016.5.31 CRWG, ECFALC2016, KEK Overview of CRWG K. Yokoya 2016.5.31 CRWG, ECFALC2016, KEK VIDYO info https://vidyoportal.cern.ch/flex.html?roomdirect.html&key=a3CCS7vpf9rmPNMeU36jW55GOM 2016/5/31 CRWG Overview

Charge of CRWG (Nov.2016) To develop a conceptual design for the central region of the ILC at a level of detail consistent with a change request and sufficient to define the CFS features of this area of the machine. Central region: the e- source, the undulator driven e+ source, the damping ring transfer lines (but not the damping rings), RTML, the beam delivery system including associated hardware (dumps, collimators, spoilers etc..) and the interaction region. Should assume: Detector hall as in CR003, tunnel geometry as CR004, lattice ILC2015b, ML tunnel crosssection with 1.5m shield, undulator positron source modified by CR011 Avoid engineering level of detail Cost-neutral (or cost reducing) approach Time line: a working concept for the ECFA workshop in Santander.  But need a few more months for the conclusion 2016/5/31 CRWG Overview

Issues Discussed Positron-related MPS,PPS Beam dumps BDS-related 10Hz operation Auxiliary positron source (APS) Positron target region MPS,PPS Beam dumps Main dumps Tune-up dumps BDS-related Muon wall Tunnel of the Central Region 2016/5/31 CRWG Overview

Session Schedule 2016/5/31 CRWG Overview

10Hz Operation TDR mentions 10Hz operation for ECM < 250GeV Gives parameter sets for 200 and 230GeV Damping ring with stronger wigglers But detail of linac operation, additional beam line, beam dynamics are not given Is 10Hz operation really needed? 200-250GeV: sweep the region above LEP But most important is Z-pole (92GeV) and W-pair (160GeV) Conclusion in CRWG Prepare spaces for beamlines that guarantee down to ECM=200GeV Actually the extra space needed is tiny  Okugi This does not guarantee ECM<200GeV. Beam dynamics complex Will think of 92GeV and 160GeV later, if turn out to be necessary 2016/5/31 CRWG Overview

Additional Beamline for 10Hz (Okugi, CRWG Mini-WS, Apr.18) Add 5Hz pulsed magnets before and after undulator Lead the spent electron to the tune-up dump (designed up to 14MW) Use vertical bends to lift up the beamline to the ceiling (max. energy = 150GeV) Required extra space of the tunnel is small Move undulator upstream slightly 2016/5/31 CRWG Overview

APS in TDR Its specification in TDR is very brief (10 lines in vol.3 part.2 p.91) 500MeV S-band NC linac Single bunch (intensity ~1%) This means 0.01/1312 = 10-5 of the nominal pulse intensity 8 SLAC-type 3m-structures, 4 RF stations, each with a 100MW modulator, 50kW klystron and SLED Location: side-by-side with the photon line from undulator. Share the target with the undulator source. Length ~40m 2016/4/19 CRWG MiniWS Yokoya

Roles of the APS Commissioning of positron DR, RTML, ML, BDS when undulator source is not available KAS (Keep Alive Source) Keep DR etc tuned while the electron ML is in (long) shutdown (due to any reason) Really needed? Positron beam for detector calibration at Z-pole Does not require 10Hz operation Parameter Group (led by Jim Brau) is making an inquiry to the detector groups on the calibration demand Time scale: Santander WS Presumably, the APS is too weak even for calibration. APS is not needed when we start with e-driven positron source, so this question is not necessary. But CRWG will concentrate on undulator scheme. 2016/4/19 CRWG MiniWS Yokoya

Is APS Really Useful? For DR For BDS For detector calibration Bunch intensity too low for measuring the orbit (Special BPM may be possible but expensive. No use in normal operation) For BDS Bunch intensity is enough for tuning (need larger dynamic range and more digitizer bits) Not enough for laser wire and beam-beam (unless the beam is small < 100nm) For detector calibration Luminosity too low even for calibration 2016/5/31 CRWG Overview

Conclusion on APS APS of TDR specification can be used for DR tuning (most important is the low emittance tuning) if 5-10 APS bunches can be accumulated in a single DR bucket to reach ~1E9, though the rep rate would be reduced to 0.5-1.0 Hz No damping time requirements High intensity phenomena (beam loading, electron cloud, etc) cannot be seen This will also help BDS tuning Replacement by electron source not realistic Prepare to change polarity Additional beam line So, keep TDR specification. Must be taken into account in the tunnel design 2016/4/19 CRWG MiniWS Yokoya

PPS Difference from TDR Questions to be answered by CRWG soon Access to ML service tunnel limited (1.5m shield) Twin tunnel  Kamaboko in BDS region? Questions to be answered by CRWG soon Allow for transport of replacement equipment. Allow emergency egress for personnel. Be consistent with ventilation of tunnels in both normal and emergency conditions. Least progress up to now 2016/5/31 CRWG Overview

MPS Protect machine against the low emittance, high intensity beam Basically, an issue of the whole machine What must be considered Check system at beam start Avoid single bunch damage Abort kicker and dump Collimation system Restart after failure Pilot bunch Mentioned in TDR as an option Should be indeipensable Should be more specific 2016/5/31 CRWG Overview

Muon Wall TDR: 5m long magnetized spoiler, filling the tunnel crosssection. Background to the detector was re-estimated with different conditions Spoiler having gap with the tunnel surface Should be taken into account for tunnel design Will be discussed in BDA/MDI session 2016/5/31 CRWG Overview

Beam Dump (main dump) CFS aspect of the 14MW dumps (2 main dumps and 2 tune-up dumps) Detailed check of the dump system is not CRWG charge Need experts Main beam dump requires Surface building Ventilation shaft Main issue is the safety To be discussed by Benno Create a team to study the main dump  Vic E-JADE?  Akira 2016/5/31 CRWG Overview

10atm water beam dump layout B. Smith, CCLRC: 0-TB-0067-404-00-A D00000000945405 2016/5/31 CRWG Overview

Water beam dump surface site scheme B. Smith, CCLRC: 0-TB-0067-410-00-A D00000000945465 Shows surface facilities that service the dump, including cooling and exhaust for gases (tritium!) 2016/5/31 CRWG Overview

Tune-up Dumps Various kinds of beam dumps in TDR Those needed for normal operation Main dumps (1 for e+, 1 for e-) electron/photon dumps in positron production line Spent beam dump for 10Hz operation may be added to this category Emergency dumps Tune-up dumps Needed for commissioning and retuning These are not very small (200-400 kW) Revisit the designs of tune-up dumps  Ewan 2016/5/31 CRWG Overview

Positron (target region) Most complicated region Issues discussed (on-going) Human access constraint Should prohibit human access when the high energy beam is on 1.5m thick separation shield between service and accelerator tunnels can be sufficient Local radiation near the target region Target, flux concentrator, first few cavities, photon dump and electron dump require additional shield Remote handling of target replacement Photon dump Layout of the target region 2016/5/31 CRWG Overview

Consensus among ILC positron team No human access to the accelerator and service tunnels needed during high-energy beam on (normal operation and commissioning) as in main linac region Special shield wall needed for target+FC+solenoid+a few cavities Photon/electron dumps must also be shielded This figure is for illustration only. To be discussed in the WS 2016/5/31 CRWG Overview

Positron (continued) To be discussed this morning in 2 sessions Joint CFS/CRWG/Sources Sources II Summary will be given in CRWG session  Kuriki san 2016/5/31 CRWG Overview

Conclusion No conclusion yet WG charge says: Time line: a working concept for the ECFA workshop in Santander. But need a few more months for the conclusion 2016/5/31 CRWG Overview