1. CRWG Overview
K. Yokoya
LCWS16 Morioka

2. Charge (abridged)
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.
Should assume
Detector Hall layout as specified in CR-003.
Tunnel geometry as specified in CR-004 (2x1.5km extension) and lattice ILC2015b.
ML tunnel cross-section as outlined for a 1.5 m central shielding wall (CR note the number changed 1312).
Avoid the temptation of trying to produce an engineering level of detail.
We are not scoped for such a task at this time
It is important to develop the central region concept in a timely way since changes have been made since the TDR and we need to progress towards a Kitakami site specific CFS footprint.
The Working Group should attempt to derive a cost-neutral (or cost reducing) approach
though I appreciate that the TDR baseline was estimated in a somewhat generic fashion for this part of the machine thus cost comparisons might prove difficult.
You should plan towards having a working concept for the ECFA workshop in Santander, in June 2016 (May 30 – Jun 5).
2016/9/8 CRWG+TB

3. New Members to CRWG Reorganization of CFS team in Japan
Lead by Hayano & Terunuma
Shinichiro Michizono
Hitoshi Hayano
Nobuhiro Terunuma
2016/9/8 CRWG+TB

4. Issues Discussed Since WG formed Main issues discussed after Santander
Positron-related
10Hz operation
Auxiliary positron source (APS)
Positron target region
Beam dumps
Main dumps
Tune-up dumps
BDS-related
Muon wall
Tunnel of the Central Region
Main issues discussed after Santander
BDS tunnel in positron side
2016/9/8 CRWG+TB

5. Tune-up Dumps There are 14 beam dumps in TDR There are classified as
Tune-up dumps (11 dumps)
O(200kW) 9 dumps
14MW dumps (E-4, E+4)
Photon dump (E+7)
Main dump (E-5,E+5)
Issue
Reduce the power ratings of tune-up dumps, especially 14MW dumps

6. Motivation of the Change Request
14MW dump is huge
~200kW dumps are not really small
Motivation to reduce the power levels are
easier system maintenance
reduced radiation shielding,
reduced cooling system
lower project risks.
Though the cost reduction is not the main motivation, some cost savings are expected.
Change request Sep D* , D* , D*
Approved.
2016/9/20 CMB, Yokoya

7. Commissioning Scenario
How can we reduce the power rating?
 Change of commissioning scenario
TDR assumes the commissioning schedule as
Tune-up each subsystem up to its full specification one by one
allowing simultaneous construction works of other systems
In particular 14MW BDS tune-up dumps are necessary for tuning the main linacs up to the full current without disturbing the works in BDS region
After tuning every subsystem to their full specification, tuning of the whole system is to be done by using the main dumps
In this last stage, one of the detectors must sit at IP
New strategy of commissioning
Tune-up each subsystem using its own tune-up dumps up using some “weak beam”. This allows lower power levels of most of the dumps.
Tuning of the whole system from weak current to the full current adiabatically using the main dumps, while one of the detectors sits at IP as the shield.
Impact on the project schedule is not expected to be large but requires detailed consideration.
2016/9/20 CMB, Yokoya

8. Weak Beam for Tuning
Appropriate power level of the ‘weak’ beam should be decided with the design of the dump hardware.
An example may be
Bunch intensity 1x (1/2)
Number of bunches per pulse ~100 (1/26)
Repetition frequency 1Hz (1/5)
Maximum beam energy 250GeV (1/2)
Some of these can be larger than these values, depending on the tuning purposes
Primary importance is the product of these numbers (average power)
2016/9/20 CMB, Yokoya

9. New Specification of the Tune-up Dumps
Details are in EDMS
Note the new specification include 20% margin
2016/9/20 CMB, Yokoya

11. 5+5 Hz 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
Special beam dump is needed for spent electron
Maximum 6.3MW is needed (150GeV, 2625 bunches)
The electron BDS tune-up dump (14MW) is implied in TDR to be used for this purpose
However, this dump would be reduced to 400kW if the new power ratings.
2016/9/20 CMB, Yokoya

12. A New Dump E-8
The present CR proposes a new dump (E-8) for 5+5Hz spent electron, to be housed in the same hall as the positron main dum E+5.
The beam line is somewhat long (2.4km)
Maximum 150GeV. (Large energy acceptance is not needed.)
No care needed for emittance increase.
5Hz pulsed dipoles needed just before and after undulator
A careful CFS design will enable to share some equipment (cooling system, chemical processing, ventilation system, etc.) with E+5.
Note that the power sum of E+5 and E-8 will never exceed 14MW.
Example of the dumpline designed by Okugi (up to the TDR E-4)
Note: this makes operation down to ECM=200GeV feasible, but does not guarantee Z-pole and W-pair.
2016/9/20 CMB, Yokoya

13. Design of the Individual Dumps
The choice of the hardware for the dumps is not in the scope of CRWG
But,
The main dumps (14MW, E-5, E+5) should be pressured water dumps as in TDR, together with the new dump E-8.
Solid dumps may be adopted for the small tune-up dumps (~60kW)
The BDS tune-up dumps (400kW, E-4, E+4) might be solid dumps (like the 300kW dump for E-XFEL) or can be aluminum ball dumps.
The undulator photon dump (E+7, 300kW) must be designed primarily by the positron group.
This is the statement at the change request (Sep.20)
Now, we know more than these
2016/9/20 CMB, Yokoya

14. Cost Impact Very crude estimation of the cost savings (MILCU)
2-300kW dumps  60kW -4.0
Reduced BDS dumps
New E-8 dump Sum
Cost of the dump line to E-8 would be around 5.4MILCU. (cost of this line, though a bit shorter, is not included in TDR)
The cost impact of this CR is anyways minor.
2016/9/20 CMB, Yokoya

15. Tunnel in BDS Region
We start with the positron BDS because there is no complication due to the positron source
We have nearly came to a conclusion
We have agreed
Single kamaboko tunnel (instead of twin tunnel in TDR for flat region) from the end of positron linac to the branching to DR
Move electron source upstream. Though this will make the 5GeV electron beamline longer, it has merits
Shorter cryogenics line from the access tunnel at linac end
Avoid radiation from the BDS collimators to shower on electron SC linac
No laser hut. Laser for electron gun can be well tuned without people in the tunnel working in beam time.
The tunnel width/height is still being studied

16. T. Okugi CRWG

17. Additional Issues in Positron BDS Tunnel
Service tunnel in <350m region from IP
Access tunnel from IP region to BDS tunnel
Power cable, cooling water,
Not for cryomodule
Safety
Link to utility hall (need 10% slope)
Muon wall

18. M.Miyahara, T.Okugi

20. Muon Wall
TDR: 5m long magnetized spoiler, filling the tunnel crosssection.
Background to the detector was re-estimated with different conditions
#/200 bunches
R=6.5m detector
R=2.5m TPC
No spoilers
138
9648
2x 5m mag.spoilers 25
1008
5x 5m toroid
3.3
273
both
0.5 17
Seems we can avoid muon wall
BDS: tomorrow by G.White
2016/9/8 CRWG+TB

21. Main Dumps Two 14 MW main dumps (plus 6.3MW spent electron dump)
Detailed check of the dump system is not CRWG expertise
But definitely needed
Need specialist team
Beam dump specialists
CFS
Issues
Check the dump concept
Robot work
Safety in particular window breakdown
Required human access
2016/9/8 CRWG+TB

22. 10atm water beam dump layout
B. Smith, CCLRC:
0-TB A D
2016/9/8 CRWG+TB

23. 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!)
2016/9/8 CRWG+TB

24. Auxiliary Positron Source
We discussed about it some half year ago.
Weak intensity but can still useful for DR emittance tuning if stacking possible
Now, under new commissioning strategy, is it still useful?
The ‘weak beam’ in the new commissioning scenario would be even stronger than this.
However, this ‘weak positron beam’ would not be available without 150GeV electron beam.
CRWG tend to eliminate APS, but will be discussed later.
2016/9/8 CRWG+TB

25. Positron (target region)
Main issues needed as inputs to CRWG
Design of photon dump
A problem (radiation damage of the window by photon beam) of TDR design pointed out at Santander
New dump concepts are being discussed (water curtain, gas)
The trend of the last one month may be a long photon line to the dump???  impact on CRWG
Required shielding of the target region including the thoughts on
Target replacement
Where/how waste targets to be stored
Path to take waste target to the surface
Lots of progress since Santander
In particular on the photon dump
Will be summarized my M.Kuriki
This would take some more time for CRWG to take into account the results
2016/9/8 CRWG+TB

26. Future Plan Expect change of organization in December
Need to finalize the positron BDS tunnel
Some items require more inputs
Electron BDS tunnel including positron target region
Main dump-related issues
Whole system must be reviewed
Installation
Commissioning
Accidents
Problem
Expand the expertise?
2016/9/8 CRWG+TB