1. Institute of High Energy Physics, Beijing
Status of CEPC
Yifang Wang
Institute of High Energy Physics, Beijing
FCPPL, March 30, 2017

2. Science of CEPC-SPPC Electron-positron collider(90, 250 GeV)
Higgs Factory（106 Higgs）:
Precision study of Higgs(mH, JPC, couplings)，Similar & complementary to ILC
Looking for hints of new physics
Z & W factory（1010 Z0）:
precision test of SM
Rare decays ?
Flavor factory: b, c, t and QCD studies
Proton-proton collider(~100 TeV)
Directly search for new physics beyond SM
Precision test of SM
e.g., h3 & h4 couplings
Precision measurement + searches:
Complementary with each other !
2018/11/21

3. CEPC is also a great light source
From dipole magnet, the photon energy can reach 628keV.
From Wiggler or undulator，the photon energy can reach 100MeV
Incredible application on nuclear physics, material science, micro-processing, etc.
CEPC

4. CEPC is a Great Opportunity
There are new physics, and also “standard” physics to be learned
No need to wait for LHC
If LHC finds nothing, a Higgs factory can give us a first indication
If LHC finds something, it is a new era
Higgs need(s) to be understood anyway
new energy scale, new spectrum, LHC can not complete it  A higher energy pp collider is needed
An e+e- Higgs factory can give us time to develop technologies for T magnet and SC cables
ILC may not be enough. CEPC is a Complementary:
Push-pull option can be given up
CEPC has a high Luminosity at H, Z, W
ILC can go to higher energy
High energy frontier is still the center of particle physics

5. Can be downloaded from http://cepc.ihep.ac.cn/preCDR/volume.html
403 pages, 480 authors
328 pages, 300 authors
2018/11/21

6. CEPC Accelerator Design
Energy Ramp
10 ->120GeV
LINAC
Booster
Storage Ring
Electron
Positron
6~10 GeV
45/120 GeV
3 Machines in a tunnel：
CEPC & booster
SppC
Compatibility is the key

7. Baseline：
100 km, 30 MW
Upgradable to
50 MW
High lumi on Z

9. Design of the RF Region RF region of CEPC
Dedicated lattice for Higgs and W & Z mode to optimize the luminosity.
Common cavities for H mode, bunches filled in half ring for e+ and e-.
Independent cavities for W & Z mode, bunches filled in full ring.
2.0 km
1.25 km
2.2 km
RF region of CEPC

10. Lattice of the Interaction Region
Provide local chromaticity correction for vertical plane.
Keep ARC sextupoles and final doublet on phases for horizontal chromaticity correction
Reverse bending direction of last bends to avoid synchrotron radiation to IP.
New IR bends
Higgs Interaction region with solenoid field Z
IR of IP upstream, Critical energy of photon < 100 keV within 250m
IR of IP downstream, Critical energy of photon < 300 keV within 250m

11. Lattice of the ARC region Sextupole configuration
FODO cell, 90/90, non-interleaved sextupole scheme
period N=5cells
all 3rd and 4th resonance driving terms (RDT) due to sextupoles cancelled, except small 4Qx, 2Qx+2Qy, 4Qy, 2Qx-2Qy
tune shift dQ(Jx, Jy) is very small
DA on momentum: large
Chromaticity dQ() need to be corrected with many families
DA off momentum: with many families to correct dQ() and –I break down
Should be 5 cells -I -I
Sextupole configuration

12. Parameters of CEPC (double ring)
Higgs W Z
Number of IPs 2
Energy (GeV)
120 80
45.5
Circumference (km)
100
SR loss/turn (GeV)
1.67
0.33
0.034
Half crossing angle (mrad)
16.5
Piwinski angle
3.19
5.69
4.29
Ne/bunch (1011)
0.968
0.365
0.455
Bunch number
412
5534
21300
Beam current (mA)
19.2
97.1
465.8
SR power /beam (MW) 32
16.1
Bending radius (km) 11
Momentum compaction (10-5)
1.14
4.49
IP x/y (m)
0.171/0.002
0.171 /0.002
0.16/0.002
Emittance x/y (nm)
1.31/0.004
0.57/0.0017
1.48/0.0078
Transverse IP (um)
15.0/0.089
9.9/0.059
15.4/0.125
x/y/IP
0.013/0.083
0.0055/0.062
0.008/0.054
RF Phase (degree)
128
126.9
165.3
VRF (GV)
2.1
0.41
0.14
f RF (MHz) (harmonic)
650
650 (217800)
Nature z (mm)
2.72
3.37
3.97
Total z (mm)
2.9
3.4
4.0
HOM power/cavity (kw)
0.41(2cell)
0.36(2cell)
1.99(2cell)
Energy spread (%)
0.098
0.065
0.037
Energy acceptance (%)
1.5
Energy acceptance by RF (%)
1.1 n
0.26
0.15
0.12
Life time due to beamstrahlung (min) 52
F (hour glass)
0.96
0.98
Lmax/IP (1034cm-2s-1)
2.0
5.15
11.9

13. CEPC Detector Requirements Key sub-detectors: Momentum: Vertex:
Energy:
Key sub-detectors:
Silicon vertex and tracking
SC solenoid magnet
Gaseous tracking
Calorimeters
Electronics, trigger & DAQ

14. Civil Construction
Surface buildings
2018/11/21

15. Site selections (a few main candidates)
Qinhuangdao
秦皇岛
Shanxi
陕西黄陵
Available Land
Geological conditions
Good social，environmental, transportational and cultural conditions
Fit to local development plan：mid-size city  + Science city
Shenzhen
深汕合作区

16. Challenges and Key R&D items
Accelerator design
Beam physics: dynamic aperture, momentum acceptance, electron cloud, single ring scheme, …
Power consumption, cost effectiveness
Key technology development
High Q0 SRF cavities and high efficiency thermal power removing SRF accelerating unit
High efficiency RF power sources(Klystron, solid state, …)
High power Cryogenic system
Beam monitor and diagnostics
Silicon detectors
High field SC magnets …

17. Current Status and the Plan
Pre-CDR completed
No show-stoppers
Technical challenges identified  R&D issues
Preliminary cost estimate
Working towards CDR
A working machine on paper
Ready to be reviewed by government at any moment
R&D issues identified and funding request underway
Seed money from IHEP: 12 M RMB/3 yrs
MOST: 36 M/5 yr approved, ~40 M to be asked next year
NSFC: ~12M RMB approved/4 yrs  6 M/yr to be approved
NCDR: ~0.8 B RMB/5 yr, failed in a voting process
CAS: ~ 8M/yr, more under discussion
CNSF: under discussion
Beijing Municipal Government: R&D platform

18. SRF System: Source of acceleration
Useful for all future accelerators
Key for the cost reduction
Extremely high Q0 cavities
New technology: N-doping to improve Q0 by a factor ~ 4
Efficient thermal power extraction
SR power
HOM power
Mass production
R&D started: (N2 doping) cavities, HOM extraction, cryomodules, …
Benefit from our R&D efforts on ILC and ADS. Industrial capabilities to be improved
Lab space (4500 m2) and equipment for R&D and (mass) testing to be built within 3 years

19. R&D and industrialization for two types started
RF Power: Source of SRF
Key factors for the cost and the power
Useful for radar, communication tech., …
R&D and industrialization for two types started
Existing technology
New design
Frequency (MHz)
650+/-0.5
Output power (kW)
800
Beam voltage (kV) 80 70
Beam current (A) 16 15
Efficiency (%) 65
Gun assembly
Collaboration with industries
Collector design

20. Common Issues with HEPS
HEPS-TF approved by NCDR
HEPS(80 km from IHEP) to be approved in 2018 ?
Applicable to CEPC: Beam diagnostics, vacuum, mechanics, …
A large R&D platform for accelerators and detectors, supported by the Municipal Government of Beijing
Beam Energy: 6 GeV
Beam Current: 200 mA
Circumference: 1300 m
Emittance: 0.06 nmrad
Requiring a factor of 10 better orbit precision, magnet precision & stability, etc.
2018/11/21

21. R&D Platform for Light Source
Applicable to CEPC:
SRF
Cryogenic system
Beam testing
X-ray semiconductor detector
Good enough for R&D and mass production test of SRF
Construction time:
2018/11/21

22. HTC Superconducting Cables
Huge impact If magnet can be used at ~ 4.5K - 20 K
Fe-based HTC cable
Metal, easy to process; Isotropic; Cheap in principle
Background in CAS
World highest Tc Fe-based materials
World first ~ 115 m Fe-based SC cables: T
A collaboration on “HTC SC materials” : Institute of Physics, USTC, Institute of electric engineering, IHEP, 3 SC cable companies in China
Iron based HTC cables
ReBCO & Bi-2212
Goal: ~ 3-5 $ /kAm
Current density:  10
Cost/m: 10

23. International Collaboration
Limited international participation for the pre-CDR
An excise for us
Build confidence for the Chinese HEP community
A new scheme of international collaboration to be explored
An international advisory board is formed to discuss in particular this issue, together with others
MOUs have been signed with many institutions
Many non-Chinese have joined working groups.
Some will join the steering committee

24. Summary
CEPC is the first Chinese effort for a Science project at such a scale  Challenges every where.
Tremendous progresses up to now, but a long way to go
Given the importance of Higgs, we hope that at least one of them, FCC-ee, ILC, or CEPC, can be realized.
We fully support a global effort, even if it is not built in China