A Flipping-coil Field Measurement System for the CSNS/RCS Dipole Magnet

1. A Flipping-coil Field Measurement System for the CSNS/RCS Dipole Magnet Wan Chen，Mei Yang*，Bao Gui Yin，Xi Wu，Wen Kang Institute of High Energy Physics, Beijing, China 18th International Magnetic Measurement Workshop June 3-7,2013 Brookhaven National Laboratory *yangmei@ihep.ac.cn

2. Outline • Introduction • Flip coil measurement system • Measurement results and analysis • Summary

3. Introduction • CSNS construction site locates at Dongguan, Guangdong province, China. The facility consists of an 80MeV H - linac, a 1.6GeV RCS, 2 beam transport lines, a target station, and 3 instruments. • Upgradable to 200kW at 25Hz and 20 instruments .

4. Main dipole of CSNS/RCS-180B RCS lattice-4 fold structure180B parameters Curved magnet with parallel ends Excited by a 25Hz current with DC biased sinusoidal waveform

5. Original Curved coil measurement system • Curved coil with Hall probe on the center head. • translate along Axis X : △BL/B0L • travel along the central trajectory(Axis Z): B0L • coil coefficient is calibrated by the hall probe Translating Axis X1&X2 Arc Rail Boards Central Trajectory R=8021mm Curved Coil

6. Motivation of the Flip coil measurement system • A supplementary to the curved coil measurement results • Curved coil can translate along X and along Z (the central trajectory ), and can only detect the AC component, which miss the DC part. • Flip coil can flip semi-circle, and detect the AC+DC component of the BL. Flip Coil inside the new prototype 160B

7. Motivation of the Flip coil measurement system(continued) • Flip coil is a straight one，and can flip 4 semi-cycle，and then average the datato reduce the measurement error. • Coil’s flip mode • 0°-180 °, 180°-360°, 360°-180°, 180°-0° • Contents to measure • Flipping the coil to get the whole component of the integral field strength(BLdc+BLac) • Transfer function • To measure the consistence of the total 24 dipoles. • Time dependent harmonics of the field and current. °

8. Basic Theory of the Flip Coil Measurement System • Faraday law of electromagnetic induction • Coil flip a semi-cycle: induce a modulation waveform • W=2πf, f=25Hz :freq of I • W1=2πf1,f1=1Hz, freq of coil • S0：area of the coil • N : coil turns • Coil static :induce a sinusoidal waveform, f1=0 Bmax Bdc Bmin

9. The System Block Diagram(AC measurement) Axis0 Control AI 0 Stepper Driver 3 axes X2 Motor with linear encoder Axis0 Feedback AI 1 Axis1 Control X1 Motor with linear encoder AI 2 Axis1 Feedback NI UMI-7774 Axis2 Control AI 3 Motor & Encoder Magnet Axis2 Feedback Flip Coil Servo Driver Axis3 Control Axis3 Feedback NI PXI-1042Q NI PXI-8105 NI PXI-4462 NI PXI-7354 Coil Signal DCCT Signal DCCT Feedback Trigger Signal Timing System 25Hz,100KHz,10MHz AC Power Supply 25Hz 25Hz 100KHz 10MHz backup

10. Main Parameters of DSA and Motion Control Card • PXI-4462 • Six gain settings for input ranges from ±316 mV to ±42.4 V • Four simultaneously sampled analog inputs at up to 204.8 kS/s • Software-configurable AC/DC coupling and IEPE conditioning • Variable antialiasing filters • Support for IEEE 1451.4 Class 1 Smart (TEDS) Sensors • 24-bit resolution ADCs with 118 dB dynamic range • PXI-7354 • 4 axes of servo or stepper motion control • High-speed 4 MHz position triggers • Built-in data acquisition with eight 16-bit analog I/O lines • 64 lines of digital I/O

11. Flip Coil Design and Construct Coil framework’s material: fiberglass-reinforced epoxy (G10) Wire: enamelled copper wire Multi segment shaft Coil With Motor & Encoder Pre installation Winding the wire

12. Software • LabVIEW code • Timing system & Synchronization & Trigger • Data acquisition • Motion control • Power supply control • File save • Data analysis • … Modulated signal

13. Data Analysis Procedure (AC part) I B DCCT Feedback Voltage Signal Modulation Voltage Signal FFT& Drift Removal FFT In, Φn, Idc, Imax, Imin Trapezoidal Integration ΔΦ FFT Bn, Φn, Bdc ,Bmax,Bmin

14. Some measurement results-DC • DC measurement • Using a high precision DC power supply (2000A/90V, 20ppm) • BL(0)@Iinj, Idc, Iext • Transfer Function • Nonlinearity(1.1%) • Reproducibility

15. Some measurement results-AC • Coil static • AC component • In，BLn Harmonic component of I & BL Coilstatic mode

16. Some measurement results-AC-2 • Coil flip half a circle • AC/DC component • In, BLn • BLmax,BLmin,BLdc • Transfer Function • Nonlinearity(2.5%) Coilflip mode (0-180 ° ) Transfer Function

17. 72 hours of baking machine • The magnetic field variation trend

18. Current harmonic injection control Before Injection After Injection After the current harmonic injection, the high order harmonic content decreased significantly, and within 0.03%.

19. Summary • The main functions of this system is nearly completed. • The whole component of BL, the dynamic characterization • The high order harmonics of BL& I • Can used to measure the consistence of the 24 dipoles • Some considerations and next steps • The trend of the BL along with time. • Compare the analog trigger and digital trigger. • The system errors study • Phase difference between the front side (0 deg) and the back side (180deg) while flipping the coil. • The reproducibility of the system at AC measurement. • …

20. Acknowledgements • Personnel arrangement • Thank you to all the other members who give great help in this procedure.

21. Thanks very much for your attentions !