1. K. Yokoya 2016.5.31 CRWG, ECFALC2016, KEK
Overview of CRWG
K. Yokoya
CRWG, ECFALC2016, KEK
VIDYO info
2016/5/31 CRWG Overview

2. 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

3. 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

4. Session Schedule
2016/5/31 CRWG Overview

5. 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?
GeV: 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

6. 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

7. 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

8. 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

9. 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

10. Conclusion on APS
APS of TDR specification can be used for DR tuning (most important is the low emittance tuning) if APS bunches can be accumulated in a single DR bucket to reach ~1E9, though the rep rate would be reduced to 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

11. 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

12. 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

13. 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

14. 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

15. 10atm water beam dump layout
B. Smith, CCLRC:
0-TB A D
2016/5/31 CRWG Overview

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

17. 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 ( kW)
Revisit the designs of tune-up dumps
 Ewan
2016/5/31 CRWG Overview

18. 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

19. 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

20. 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

21. 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