CEPC Beam Instrumentation Yanfeng Sui On behalf Beam
CEPC Beam Instrumentation Yanfeng Sui On behalf Beam Instrumentation Group Accelerator Center, IHEP The 2019 International Workshop on CEPC, Nov. 18 -20, 2019. IHEP.
Outline • Refine of CDR design • Beam instrumentation R&D towards TDR • Summary 10/3/2020 2
The beam instrumentation in CEPC ring Item Beam position monitor Storage ring Method Closed orbit Button electrode BPM Bunch by bunch Button electrode BPM Bunch current BCM Average current DCCT Parameter Measurement area ± 20 mm×± 10 mm Amounts (x y): Resolution:<0. 002 mm Measurement time of COD:< 4 s Measurement area (x y): ± 40 mm×± 20 mm Resolution: 0. 1 mm Measurement range: 10 m. A / per bunch Relatively precision: 1/4095 Dynamic measurement range: 0. 0~1. 5 A Linearity: 0. 1 % 2900 2 2 Zero drift: <0. 05 m. A Beam size Double slit interferometer x ray pin hole Resolution: 0. 2 µm 4 Bunch length Streak camera Two photon intensity interferometer Resolution: 1 ps 2 Frequency sweeping method Resolution: 0. 001 DDD Resolution: 0. 001 PIN-diode Dynamic range: 120 d. B Maximum counting rates≥ 10 MHz 5800 TFB Damping time<=rise time 2 LFB Damping time<=rise time 2 TUNE measurement Beam loss monitor Feedback system 2
The beam instrumentation in CEPC booster Item Beam position monitor Method Closed orbit Bunch by bunch Bunch current Button electrode BPM BCM Parameter Measurement area ± 20 mm×± 10 mm Amounts (x y): 1808 Resolution:<0. 002 mm Measurement time of COD:< 4 s Measurement area ± 40 mm×± 20 mm Resolution: 0. 1 mm (x y): Measurement range: 10 m. A / per bunch Relatively precision: 1/4095 1808 2 Dynamic measurement range: 0. 0~1. 5 A Average current DCCT Linearity: 0. 1 % 2 Zero drift: <0. 05 m. A Booster Beam size Bunch length TUNE measurement Double slit interferometer x ray pin hole Streak camera Two photon intensity interferometer Frequency sweeping method DDD Resolution: 0. 2 µm 2 Resolution: 1 ps 2 Resolution: 0. 001 Beam loss monitor optical fiber Space resolution: 0. 6 m 400 Feedback system TFB Damping time<=rise time 2
Refine of CDR design • Beam position monitor • Beam current monitor • Feedback systems 10/3/2020 5
Beam Position monitor l To provide the beam position and orbit l To calculate machine parameters related to beam position l Apart from specific BPMs, there are 4708 BPMs in booster and storage ring. l Button type electrode with 8 mm diameter will be adopted, for its good high frequency response and small beam impedance l The resolution of BPM will be ~2 um 10/3/2020 6
BPM simulation Ø Volts getting on the pickup is more than 100 V when button diameter is 8 mm Ø Sensitivity be simulated at the different angle 10/3/2020 7
Beam current monitor l Including DCCT (for average current) and BCM (bunch current monitor) l Using Bergoz-type DCCT to measure the average current of the beam and to calculate the life time of beam. The resolution will be µA level; 10/3/2020 8
Beam current monitor • Bunch current monitor with fast ADC sampling BPM sum signal is used to measure bunch current and share data with injection control system for bucket selection. • The fast ADC is commercial product. Innovative Integration XG-12. 2 channels 12 -bits ADC with 1 G sampling rate. 512 MBytes DDR 2 DRAM and PCI Express x 8 sockets for data transmission.
Two topologies of FB design One BPM and One kicker, 90 degree phase shift and DC filter both are got in FPGA. The tap number is always more than 2. Two BPMs and One kicker, 90 degree phase shift can got by adjusting the amplitude of two BPMs signal and DC filter are got in FPGA. The tap number is 2. 10/3/2020 10
The Composition of feedback system AR AMP BPM Front end electronic s Signal processor AMP Kicker AMP Home made AMP Back end AMP Kicker
Transverse feedback on the booster E=10 Ge. V,βm=βk=120 m,Δx=0. 3 mm, τFB =1. 45 ms,so ΔVFB⊥= 9. 27 k. V, P=344 w. • 4 -tap filter was considered • One BPM and One kicker, 90 degree phase shift and DC rejection both are got in FPGA. • 2 amplifiers, 300 W for each 12
Transverse feedback Kicker on the booster ※ shunt impedance Rs 50 45 40 35 30 25 20 15 10 5 0 l=500 Rs(kΩ) Zc : Characteristic Impedance 50Ω; gtrans=1; k =w / c a: radius; l: length of strip line l=577 mm SHUNT IMPEDANCE 0 100 200 300 Frequency (MHz) 400 500
Longitudinal feedback status E=10 Ge. V,α=0. 0000244, νs=0. 1, τFB =50 ms,so ΔVFB|| = 2144 V,P=884 W. 65 • 20 -tap filter was considered • One BPM and One kicker • 90 degree phase shift and DC rejection both are got in FPGA. • 4 amplifiers, 250 W for each 14
Parameters of the CEPC main ring parameter Higgs W Z nus 0. 065 0. 04 0. 028 Nux/nuy Energy(Ge. V) 363. 10 / 365. 22 120 alphp 80 45. 5 1. 11 E-5 Rising time(ms) 51. 6 19. 6 2. 3 Natural damping time(ms) 46. 5 156. 4 850 Revolution time(ms) 0. 33 Bunch number 242 1524 12000 Bunch space(ns) 680 210 25 current(m. A) 17. 4 88 461 • Z is the most dangerous mode which need feedback system. • Fast beam ion instability is dominant. • Damping time requirement for transverse feedback : <2. 3 ms 10/3/2020 15
Calculation result of TFB on main ring 1,two BPMs, one kicker. 2,2 -tap filter, total processing time is about 2 turn,0. 66 ms 3,Damping time should be smaller than 1. 64 ms. For CEPC main ring Z mode, E=45. 5 Ge. V, βm=225 m, βk=225 m, Δx=0. 2 mm, take τFB =1. 60 ms,so ΔVFB⊥= 16. 7 k. V, P=898 w. AR 500 A 250 A, the output power is 500 w. Optional choice:using multi-TFBs to shorter the damping time. 10/3/2020 16
R&D of CEPC beam instrumentation l BPM electronics ü The upgrading design of electronics ü The application of the electronics in BEPCII ü B&B BPM electronics R&D 10/3/2020 17
R&D Motivation • To reduce the budget of BI system, due to a large number of beam position monitors and the high price of commercial products. • Customized for different part of CEPC-Linac, Booster and storage ring. • Easy to maintain and upgrade.
The BPM electronics • The R&D of BPM electronics founded by seed money of IHEP and other funding(HEPS-TF etc. ) • Kicked off in the start of 2015 • The first version of the electronics was finished in the last year. Some results of the electronics are from testing in lab and real beam. • To improve the performance of the electronics, modification was done in the new version electronics.
The BPM electronics • The V 2. 0 BPM electronics was finished. • The ADCs are located in RF front end, the mismatch between the connectors of AFE and DFE would do not effect digital signal. The AFE board with ADCs The Lab. test results of new version electronics, the resolution is better than 40 nm in both directions
Application of BPM electronics in BEPCII • The single-pass mode BPM electronics is developed for the linac. • After finishing prototype test, small batch production and application has been done in BEPCII • The results shows that the resolution of electronics is about 14 um in the lab test and 27 um for the real beam test. The lab test result shows that the The beam test result shows that the resolution is about 27 mm resolution is about 14 mm 10/3/2020 21
Bunch by bunch BPM electronics R&D • The beam trip is an important problem for accelerator operation. Because the accelerator system is very complicated, involves many subsystems, and various conditions are mixed together, so, it is difficult to get to the real cause for beam trip. • At present, many accelerators all over the world have established a powerful beam trip diagnostic system. • Beam trip seriously affects the efficiency of the machine, also may cause damage to the hardware system. So, it is necessary for CEPC to develop bunch by bunch BPM for studying the beam trip. 10/3/2020 22
Bunch by bunch BPM electronics Trigger 10/3/2020 Buffer of bunch by bunch raw ADC data 23
Bunch by bunch BPM electronics Sampling clock: 500 MHz, free running clock or externally clocked with beam signal ADC_a ADC_b AFE DFE clock ADC_c ADC_d 10/3/2020 24
Bunch by bunch BPM electronics Input: simulation pattern of BEPCII , repetition period 6 ns 10/3/2020 25
summary l Based on the CDR, beam position monitor, beam current monitor and feedback in booster are refined. l Modification has been made in digital BPM electronics to improves the performance. l The bunch by bunch system are developed for beam failure monitor. More test should be done in the real machine. l In the future, more attention should be paid in the SR feedback and beam instrumentation in interaction point(IP). 10/3/2020 26
Thanks for your attention ! 27
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