1. INSTITUTE OF HIGH ENERGY PHYSICS CEPC Survey and Alignment
Xiaolong Wang
On behalf of Survey and Alignment team
CEPC International Workshop
Nov , 2018, IHEP Beijing China

2. Outline 1、CDR Status 2、TDR work plan

3. CDR Status

4. S&A Overview
Survey and Alignment group(S&A) is responsible for CEPC components position alignment and maintenance.
S&A work can be divided into 4 parts:
Alignment control network survey
Component fiducialization and pre-alignment
Tunnel installation alignment
Components segmentally smooth alignment

5. Challenges
Error accumulation control.
Improve working efficiency.
To control the error accumulation
3 levels control network
Surface control network
Backbone control network
Tunnel control network

6. Surface control network
Composed of 16 control points (4 external points and 12 internal points)
Use GPS and level measure the surface network Y X Z
Tunnel permanent point

7. Instruments and software for Surface network survey
+ LGO software
LEICA GS10
AR20
LEICA NA2 + SHANWEI software
LEICA Wild NL
Tape
LEICA AT401

8. Backbone control network
tunnel control point
Large span double-traverse structure.
Points of adjacent sections must be intervisible and the distance should be as long as possible
Use total stations to carry out backbone network survey.
Backbone control network
sketch map

9. Tunnel control network Evenly distributed with an interval of 6 meters
Future upgrade to a Proton accelerator
Booster
Tunnel control network
Evenly distributed with an interval of 6 meters
Use laser trackers and levels carry out tunnel network survey
Tunnel cross-section view
Double-ring

10. Component fiducialization and tunnel alignment
Component fiducialization is to transfer the beam center to its fiducials, then the fiducials coordinates can be transferred to CEPC global coordinate system and used for component tunnel alignment
Laser tracker
Articulated arm
Photogrammetry
The precision of components’ fiducialization is about mm.
Get boundary dimensions
Reference features
Bunching cavity Fiducialization with Articulated flexible arm
Dipole Magnet
Fiducialization Datum Planes
Camera
Photogrammetry measurement

11. Use tunnel control network and laser trackers to perform tunnel components installation alignment.
After the initial installation, we will carry out some smooth alignment.

12. Alignment precision requirement
Provide by physics group
Component
Transversal/mm
Vertical/mm
Longitudinal/mm
Pitch
/mrad
Yaw
Roll
Dipole
0.1
0.15
0.2
Quadrupole
Sextupole
Corrector
 0.2
0.2 
 0.1

13. z CEPC should be built on a plane, its normal direction is Z.
The earth is an ellipsoid, its gravity directions along the CEPC tunnel are not parallel with the Z.
R=6374km Z
CEPC ring center
The earth
tunnel
D=32km
The angle between Z and tunnel local gravity direction is about °
In tunnel components will be not perpendicular to the ground.
CEPC plane z
0.144 °
Gravity direction

14. Interaction region alignment
Alignment in the interaction region will be much more demanding than in the Arcs due to the extremely low β-functions.
Use laser trackers to do a rough alignment first.
use a laser collimator system to do refined alignment
Laser collimator system
Laser tracker

15. Hydrostatic Levelling System(HLS)
Monitoring system
Settlement monitor
Hydrostatic Levelling System(HLS)
HLS sensors will be installed on the ground near the components.
Every 200m will be equipped with a sensor along the tunnel
Accuracy ±0.01mm
Component transversal and vertical monitor
Wire Positioning System (WPS)
HLS Sensor
HLS

16. TDR work plan

17. Content
1、Vision instrument R&D 2、 laser collimator system R&D 3、Geoid refining

18. 1、Vision instrument
The vision instrument is a kind of new type measurement instrument, it will integrate photogrammetry, distance, angle measurement functions and has high precision, high efficiency characteristics.
Research purpose
Improve tunnel survey efficiency, realize high precision multiple points measurement by taking pictures.
Convenient for oversize component assembly measurement.
Component fiducialization.
Heavy radiation area non-contact measurement

19. Challenges
Recognize control points from tunnel complex background environment.
Tunnel large scale space overlap measurement
Mass control point name match
Improve photogrammetry precision
Add angle and length measurement as constraint conditons into photogrammetry.
Methods to be adopted
R&D high precision photogrammetry camera
R&D special target

20. R&D high precision bearing system
Integrate laser distance meter, turntable and photogrammetry camera into the vision instrument.
Use a 3D calibration field for instrument parameters calibration.
R&D million capacity coded target for control point name match.
R&D photogrammetry algorithm to realize image extraction, data compression, image matching, control point recognition and target center calculation functions.
R&D instrument control software and adjustment software, realize image, angle and distance information integrated adjustment function.
Utilize the existing experiment field and accelerator tunnel carry out measurement experiment, test the instrument and software , explore measurement methods, to do further improvement.

21. R&D schedule
Goal: Key components calibration, integration, produce a prototype instrument.
Tasks:
High precision bearing system research
Assembly solutions and mechanical structure design.
Design parameter calibration schemes of turntable, camera and distance meter.
Finish parameters calibration.
Finish prototype instrument fabrication and assembly.

22.
Goal : instrument control system development
Goal : prototype instrument test, research accuracy compensation solutions
Goal : data process software and accuracy compensation software development
Tasks:
Research five-face target center calculation algorithm.
Big data adjustment algorithm.

23. Research how to improve image process speed.
How to use distance and angle as constraint conditions to improve adjustment accuracy.
Software debug.
Goal : produce a vision instrument which distance meter optic axis and camera optic axis are coaxial.
Research coaxial assembly solutions of distance meter and camera.
Structure design and fabrication
Goal : vision instrument test and improvement

24. Goal : High precision five-face target research
Goal : High precision five-face target research
High precision target body processing technic.
Retro-reflective coating technology.
Retro-reflective layer accurately assembly process.
Schedule
Date
Personnel
Prototype instrument research 2
Control system development 1
Prototype instrument test & accuracy compensation research
Application software research
Coaxial research
Vision instrument improvement
Five-face target research
Total 8

25. 2、Laser collimator system
Research purpose: Provide high precision position reference for straight section components alignment . Precision: 0.05μm/40m
Strategy
Use laser as a straight line reference. Through the transfer equipments the straight line reference can be transferred to the outside fiducials. Laser tracker measure these fiducials to get the straight line reference and carry out component alignment.
Challenges
keep the long distance laser stable
Accurately measure the laser center
Accurately transfer the straight line reference to the fiducials.

26. R&D plan
Laser optical system research
Laser position adjustment equipment design
Measurement device control system development
Measurement software research
Vacuum system development
Measurement device design
Transfer equipment design

27. Schedule Date Personnel
Component investigation 1
System general design
Laser optical system research
control system development
Measurement device design
Transfer equipment design
Mechanical structure design
Vacuum system development
Test and improvement
Total 6

28. 3、Geoid refining Research purpose:
CEPC geometric plane
Research purpose:
Establish a high precision geoid modle .
CEPC should be installed on a geometric plane
Level measurement is based on the local geoid.
The geoid is an irregular surface.
Difference need to be considered.
We need to get a precise geoid model for CEPC alignment

29. Use these data to establish a grid-based geiod model .
Methods to be adopted
Measure a certain density grid points within CEPC area, acquire their coordinate and gravity data.
Use these data to establish a grid-based geiod model .
Invite experts help us to do this work
Schedule
Date
Personnel
Geoid refining investigation 1
Scheme design
Measurement experiment 4
Scheme improvement
Total 6

30. Cooperation unit Beijing Prodetec Technoloy Co..Ltd. ;
Camera and coded target research
China Academy of Space Technology;
Vision instrument structure design, bearing system design and manufacture.
Hanzhong Yuanhang Precision Machinery Co..Ltd;
Five-face target body manufacture
Chang’an University;
Retro-reflective coating technology research

31. R&D Status Temperature & Humidity laboratory(constructed)
3D Calibration Field for instrument parameters calibration
3μm+3ppm photogrammetry camera
One million capacity coded target has been developed and the recognition software has been tested.
3D Calibration Field
Target extraction
Cross ratio invariance
Model point extraction
Affine transformation
Recover code structure
Coded value
3μm+3ppm Camera

32. High precision retro-reflective coating technology
Five-face target.
High precision retro-reflective coating technology
Vision instrument model integrated with a camera, a distance meter and a 2D-turnable.
High precision bearing system is under research.
Detailed structure is under research.
Purchased a distance meter
Distance meter
Five-face target
Photogrammetry experiment

33. 3 2 1 4 5 6 R&D Status Photogrammetry experiments 2017.12
Space:14m×7m×2m
6 pillars→3×2
7m interval
Explore photogrammetry method, successfully get all targets’ coordinate 3 2 1 4 5 6

34. 2018.1
14pillars ->7×2, 35m. Simulate tunnel control network
Tried three kinds measurement method
Compare with laser tracker
Point measurement precision is 0.4mm.
Conclusion
Target density influence measurement precision.
Measure target from different directions can improve measurement precision.
Local measurement + overall measurement.

35. 2018.8
CSNS ring tunnel
70m about ¼ ring, control network and 10 magnets
Hemisphere target
Compare with laser tracker

36. Hemisphere target measure control points, coded targets match images.
Strategy:
Hemisphere target measure control points, coded targets match images.
Local single magnet measurement + large range overall measurement
Measurement efficiency is much higher than laser tracker.
Measurement precision need to be further improved X Y Z
Total 1
0.226
0.282
0.214
0.420 2
0.288
0.266
0.209
0.445 3
0.333
0.220
0.189
0.442 4
0.173
0.271
0.187
0.372 5
0.259
0.256
0.181
0.407 6
0.204
0.205
0.185
0.343

37. 7、Summary CDR gave the general alignment strategy of CEPC.
Three R&D schedules are made up to 2022
Some researches have been done for vision instrument R&D
Laser collimator and geoid refining R&D will be pushed forward in condition of get financial support.

38. Thanks！