INSTITUTE OF HIGH ENERGY PHYSICS CEPC Survey and Alignment Xiaolong Wang On behalf of Survey and Alignment team CEPC International Workshop Nov. 12-14, 2018, IHEP Beijing China

Outline 1、CDR Status 2、TDR work plan

CDR Status

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

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

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

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

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

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

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 0.05-0.10 mm. Get boundary dimensions Reference features Bunching cavity Fiducialization with Articulated flexible arm Dipole Magnet Fiducialization Datum Planes Camera Photogrammetry measurement

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

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

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 0.144 ° In tunnel components will be not perpendicular to the ground. CEPC plane z 0.144 ° Gravity direction

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

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

TDR work plan

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

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

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

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.

R&D schedule 2018.10-2020.5 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.

2019.9-2020.5 Goal : instrument control system development 2020.6-2020.10 Goal : prototype instrument test, research accuracy compensation solutions 2019.1-2021.5 Goal : data process software and accuracy compensation software development Tasks: Research five-face target center calculation algorithm. Big data adjustment algorithm.

Research how to improve image process speed. How to use distance and angle as constraint conditions to improve adjustment accuracy. Software debug. 2019.1-2021.5 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 2021.6-2022 Goal : vision instrument test and improvement

Goal : High precision five-face target research 2018.10-2019.12 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 2018.10-2020.5 2 Control system development 2019.9-2020.5 1 Prototype instrument test & accuracy compensation research 2020.6-2020.10 Application software research 2019.1-2021.5 Coaxial research Vision instrument improvement 2021.6-2022 Five-face target research 2018.10-2019.12 Total 8

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.

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

Schedule Date Personnel Component investigation 2018.10-2019.6 1 System general design 2019.1-2019.6 Laser optical system research 2019.7-2020.6 control system development Measurement device design Transfer equipment design 2020.7-2020.12 Mechanical structure design 2019.7-2020.12 Vacuum system development Test and improvement 2021.1-2022 Total 6

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

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 2018.10-2019.6 1 Scheme design 2019.7-2019.12 Measurement experiment 2020.1-2020.12 4 Scheme improvement 2021.1-2022 Total 6

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

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

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

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

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.

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

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

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.

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