IPAC2018 - List of Authors (Leng, Y.B.)

Paper	Title	Page
WEPAF027	Low Q Cavity BPM Study for the Beam Position Measurement of Nanosecond Spaced Electron Bunches	1881
	L. Yang, X. He, L.W. Zhang CAEP/IFP, Mainyang, Sichuan, People's Republic of China S.S. Cao, Y.B. Leng, L.Y. Yu, R.X. Yuan SINAP, Shanghai, People's Republic of China
	Funding: National natural science foundation of China, 11705184 Low Q cavity BPM is a key to distinguish closely spaced electron bunches allowing precise beam handling for XFEL facilities operating in a multi-bunch mode at high repetition rate up to hundreds MHz. The inter-bunch signal pollution issue becomes significant when bunch separation is down to nanosecond and causes the position detection to be increasingly overestimated. Solely relying on extreme low Q to achieve sufficient decay within bunch interval leads to appreciable interference from non-signal modes due to strong overcoupling of antenna design is required. The error imposed on measured position raises a challenge to meet the goal of high resolution. Alternatively, a concept is proposed to remove the dominant part of signal pollution at the moment of sampling by intentionally shifting the phase of the last bunch signal 90degree respect to that of current bunch signal, where signal sampling is normally taken for nanosecond spaced bunches. This quadrature phase shift is defined by properly choosing the operational frequency of dipole mode regarding to the bunch frequency. A low Q cavity BPM prototype to identify technical challenges and verify this concept is under development in the R&D plan for future XFEL with high repetition rate
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPAF027
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THPML067	SXFEL Linac BPM System Development and Performance Evaluation	4794
SUSPF094	use link to see paper's listing under its alternate paper code
	F.Z. Chen, T. Wu SSRF, Shanghai, People's Republic of China J. Chen, L.W. Lai, Y.B. Leng, L.Y. Yu, R.X. Yuan SINAP, Shanghai, People's Republic of China
	Shanghai Soft X-ray Free Electron Laser (SXFEL) is a test facility to study key technologies and new FEL physics. In order to deliver high quality electron beams to the undulator section, a high resolution (better than 10 microns with 200pC beam) Linac beam position monitor system has been developed. The system consists of stripline pickup and custom designed DBPM processor. The hardware and software architecture will be introduced in this paper. The online performance evaluation results will be presented as well.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPML067
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THPML072	Injection Comparison using Bunch-by-Bunch Beam Size Measurement System at SSRF	4811
	H.J. Chen, J. Chen, B. Gao, Y.B. Leng SINAP, Shanghai, People's Republic of China
	Injection transient process happens every 5-10 minutes in storage ring during normal top-up operating mode at SSRF, which is a proper window for machine status and injection performance evaluation. In the recent year, a bunch-by-bunch beam size measurement system has been implemented at SSRF, which has the capability to offer transverse bunch-by-bunch position and size information and is a powerful tool for injection study. In this paper, we summarize three injection study results from July 2017 to April 2018, including betatron oscillation amplitude, spectrum, horizontal tune and damping time comparison. The oscillation amplitude and temporal behavior of recent injection are all better than results before contributed to the injection optimization work during maintenance in 2018 winter. In addition, the principal component analysis method is also applied to further study the injection behavior in turn-by-turn or bunch-by-bunch direction to the refilled bucket.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPML072
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THPML061	X-Band Low Q Cavity Beam Position Monitor Study	4777
SUSPF093	use link to see paper's listing under its alternate paper code
	S.S. Cao SINAP, Shanghai, People's Republic of China Y.B. Leng, R.X. Yuan SSRF, Shanghai, People's Republic of China
	The high repetition-rate and high peak brilliance of X-ray free-electron laser (XFEL) allow studying many scientific experiments that have not been feasible. To realize such high performance, a sub-micron beam transverse position measurement is required. The cavity-type beam position monitor (CBPM), as a non-destructive diagnostics tool with high potential in resolution performance, has been applied in different free electron laser facilities (FELs). In this research, an X-band high bandwidth CBPM has been studied and used for pre-research on bunch-by-bunch diagnostic for the pulsed FEL with high repetition-rate. Its bandwidth reaches 300 MHz. Design considerations and simulation results of the CBPM have been discussed and presented in this paper.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPML061
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THPML062	A Beam Based Method to Optimize the SBPM System	4780
SUSPF095	use link to see paper's listing under its alternate paper code
	J. Chen SINAP, Shanghai, People's Republic of China L.W. Lai, Y.B. Leng, T. Wu, R.X. Yuan SSRF, Shanghai, People's Republic of China
	For the electron accelerator, it is hoped that the trajec-tory of the beam can pass through the magnetic center of the quadrupole to minimize the orbital motion caused by the instability of the power supply. The relative deviation between the magnetic center of quadrupole and the elec-tric center of adjacent BPM is measured by electron beam usually in various accelerator facilities. But for the stripline BPM (SBPM) system, in order to achieve the best performance, the beam trajectory should also need to pass through the electrical center of the SBPM system. In this paper, a beam based method to optimize the SBPM system was proposed, the intensity of the magnet power was scanned to change the beam position in two-dimension and combine the change trend of the sum signal of adjacent SBPM to find out the relative deviation of BPM electric center and mechanical center. Relevant beam experiment work on the Shanghai Soft X-ray free electron laser (SXFEL) and the benefit of this method will be addressed as well.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPML062
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THPML068	Upgrade of Bunch Phase Monitor at SSRF Storage Ring	4797
	Y.M. Zhou, Y.B. Leng, T. Wu, N. Zhang SSRF, Shanghai, People's Republic of China
	Beam instability is a serious problem for physics in beam diagnosis technology. With regard to the evaluation of longitudinal phase oscillations during the transient injection process, bunch-by-bunch phase measurement is a useful tool for studying the behavior of the refilled bunches. A new upgraded beam phase monitor system with 1.2GHz bandwidth PXI waveform digitizer has been developed at Shanghai synchrotron radiation source (SSRF). Bunch-by-bunch phase information, retrieved from button pickup signals, is calculated by the zero-crossing detection method with the best phase resolution of 0.4ps. The refilled bunches can be separated from the stored ones, and the longitudinal offset of each refilled bunch has been measured. Several groups of experiments have been performed to verify the repeatability of bunch-by-bunch phase measurement, and some results regarding refilled bunches will be discussed in this paper.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPML068
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THPML069	The Control System Design of SCLF	4800
	Y.B. Yan, J.G. Ding, G.Y. Jiang, Y.B. Leng SSRF, Shanghai, People's Republic of China J.F. Chen SINAP, Shanghai, People's Republic of China
	The high-gain free electron lasers have given scientists hopes for new scientific discoveries in many frontier research areas. The Shanghai Coherent Light Facility (SCLF) was proposed by the central government of China on April 2017, which is a quasi-continuous wave hard X-ray free electron laser facility. The control system is responsible for the facility-wide device control, data acquisition, machine protection, high level database or application, as well as network and computing platform. It will be mainly based on EPICS to reach the balance between the high performance and costs of maintenance. The latest technology will be adopted for the high repetition rate data acquisition and feedback system. The details of the control system design will be reported in this paper.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPML069
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THPML070	Point Spread Function Study of Quasi-Monochromatic X-Ray Pinhole Camera at SSRF	4803
	B. Gao, H.J. Chen SINAP, Shanghai, People's Republic of China J. Chen, Y.B. Leng SSRF, Shanghai, People's Republic of China
	Since 2009 an X-ray pinhole camera that has been used to present the transverse beam size and emittance on diagnostic beam line of the storage ring at SSRF. The real beam size is a function of the image size of the CCD camera and point spread function (PSF) of the system. The performance of the measurement of the transverse electron beam size is given by the width of the PSF of X-ray pinhole camera. The contributions to the PSF width are the PSF of pinhole itself due to diffraction, and the PSF of the screen and camera. An X-ray monochromatic system has been established to measure the PSF accurately, and decrease the variation in the beam size between the theoretical values and the measured ones at SSRF. In this article, both calculated and measured PSF of quasi-monochromatic X-ray pinhole camera will be presented in detail.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPML070
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THPML071	Upgrade of Digital BPM Processor at DCLS and SXFEL	4807
	L.W. Lai, F.Z. Chen, Y.B. Leng, T. Wu, Y.B. Yan SSRF, Shanghai, People's Republic of China J. Chen SINAP, Shanghai, People's Republic of China
	A digital BPM processor has been developed at 2016 in SINAP for DCLS and SXFEL, which are FEL facilities built in China. The stripline BPM and cavity BPM processors share the same hardware platform and firmware, but the processing algorithms implemented in EPICS IOC on the ARM CPU are different. The capability of the ARM limits the processing speed to 10 bunches per second. Now the bunch rate of DCLS and SXFEL are going to increase from 10Hz to 50Hz. To meet the higher processing speed requirements, the processor firmware and software are upgraded in 2017. All BPM signal processing algorithms are implemented in FPGA, and EPICS IOC reads results only. After the upgrade, the processing speed reach 120 bunches per second. And this is also a good preparation for future Shanghai Hard-X ray FEL, which bunch rate is about 1MHz.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPML071
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

Paper

Title

Page

Low Q Cavity BPM Study for the Beam Position Measurement of Nanosecond Spaced Electron Bunches

1881

L. Yang, X. He, L.W. Zhang
CAEP/IFP, Mainyang, Sichuan, People's Republic of China
S.S. Cao, Y.B. Leng, L.Y. Yu, R.X. Yuan
SINAP, Shanghai, People's Republic of China

Funding: National natural science foundation of China, 11705184
Low Q cavity BPM is a key to distinguish closely spaced electron bunches allowing precise beam handling for XFEL facilities operating in a multi-bunch mode at high repetition rate up to hundreds MHz. The inter-bunch signal pollution issue becomes significant when bunch separation is down to nanosecond and causes the position detection to be increasingly overestimated. Solely relying on extreme low Q to achieve sufficient decay within bunch interval leads to appreciable interference from non-signal modes due to strong overcoupling of antenna design is required. The error imposed on measured position raises a challenge to meet the goal of high resolution. Alternatively, a concept is proposed to remove the dominant part of signal pollution at the moment of sampling by intentionally shifting the phase of the last bunch signal 90degree respect to that of current bunch signal, where signal sampling is normally taken for nanosecond spaced bunches. This quadrature phase shift is defined by properly choosing the operational frequency of dipole mode regarding to the bunch frequency. A low Q cavity BPM prototype to identify technical challenges and verify this concept is under development in the R&D plan for future XFEL with high repetition rate

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPAF027

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPML067

SXFEL Linac BPM System Development and Performance Evaluation

4794

SUSPF094

use link to see paper's listing under its alternate paper code

F.Z. Chen, T. Wu
SSRF, Shanghai, People's Republic of China
J. Chen, L.W. Lai, Y.B. Leng, L.Y. Yu, R.X. Yuan
SINAP, Shanghai, People's Republic of China

Shanghai Soft X-ray Free Electron Laser (SXFEL) is a test facility to study key technologies and new FEL physics. In order to deliver high quality electron beams to the undulator section, a high resolution (better than 10 microns with 200pC beam) Linac beam position monitor system has been developed. The system consists of stripline pickup and custom designed DBPM processor. The hardware and software architecture will be introduced in this paper. The online performance evaluation results will be presented as well.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPML067

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPML072

Injection Comparison using Bunch-by-Bunch Beam Size Measurement System at SSRF

4811

H.J. Chen, J. Chen, B. Gao, Y.B. Leng
SINAP, Shanghai, People's Republic of China

Injection transient process happens every 5-10 minutes in storage ring during normal top-up operating mode at SSRF, which is a proper window for machine status and injection performance evaluation. In the recent year, a bunch-by-bunch beam size measurement system has been implemented at SSRF, which has the capability to offer transverse bunch-by-bunch position and size information and is a powerful tool for injection study. In this paper, we summarize three injection study results from July 2017 to April 2018, including betatron oscillation amplitude, spectrum, horizontal tune and damping time comparison. The oscillation amplitude and temporal behavior of recent injection are all better than results before contributed to the injection optimization work during maintenance in 2018 winter. In addition, the principal component analysis method is also applied to further study the injection behavior in turn-by-turn or bunch-by-bunch direction to the refilled bucket.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPML072

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPML061

X-Band Low Q Cavity Beam Position Monitor Study

4777

SUSPF093

use link to see paper's listing under its alternate paper code

S.S. Cao
SINAP, Shanghai, People's Republic of China
Y.B. Leng, R.X. Yuan
SSRF, Shanghai, People's Republic of China

The high repetition-rate and high peak brilliance of X-ray free-electron laser (XFEL) allow studying many scientific experiments that have not been feasible. To realize such high performance, a sub-micron beam transverse position measurement is required. The cavity-type beam position monitor (CBPM), as a non-destructive diagnostics tool with high potential in resolution performance, has been applied in different free electron laser facilities (FELs). In this research, an X-band high bandwidth CBPM has been studied and used for pre-research on bunch-by-bunch diagnostic for the pulsed FEL with high repetition-rate. Its bandwidth reaches 300 MHz. Design considerations and simulation results of the CBPM have been discussed and presented in this paper.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPML061

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPML062

A Beam Based Method to Optimize the SBPM System

4780

SUSPF095

use link to see paper's listing under its alternate paper code

J. Chen
SINAP, Shanghai, People's Republic of China
L.W. Lai, Y.B. Leng, T. Wu, R.X. Yuan
SSRF, Shanghai, People's Republic of China

For the electron accelerator, it is hoped that the trajec-tory of the beam can pass through the magnetic center of the quadrupole to minimize the orbital motion caused by the instability of the power supply. The relative deviation between the magnetic center of quadrupole and the elec-tric center of adjacent BPM is measured by electron beam usually in various accelerator facilities. But for the stripline BPM (SBPM) system, in order to achieve the best performance, the beam trajectory should also need to pass through the electrical center of the SBPM system. In this paper, a beam based method to optimize the SBPM system was proposed, the intensity of the magnet power was scanned to change the beam position in two-dimension and combine the change trend of the sum signal of adjacent SBPM to find out the relative deviation of BPM electric center and mechanical center. Relevant beam experiment work on the Shanghai Soft X-ray free electron laser (SXFEL) and the benefit of this method will be addressed as well.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPML062

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPML068

Upgrade of Bunch Phase Monitor at SSRF Storage Ring

4797

Y.M. Zhou, Y.B. Leng, T. Wu, N. Zhang
SSRF, Shanghai, People's Republic of China

Beam instability is a serious problem for physics in beam diagnosis technology. With regard to the evaluation of longitudinal phase oscillations during the transient injection process, bunch-by-bunch phase measurement is a useful tool for studying the behavior of the refilled bunches. A new upgraded beam phase monitor system with 1.2GHz bandwidth PXI waveform digitizer has been developed at Shanghai synchrotron radiation source (SSRF). Bunch-by-bunch phase information, retrieved from button pickup signals, is calculated by the zero-crossing detection method with the best phase resolution of 0.4ps. The refilled bunches can be separated from the stored ones, and the longitudinal offset of each refilled bunch has been measured. Several groups of experiments have been performed to verify the repeatability of bunch-by-bunch phase measurement, and some results regarding refilled bunches will be discussed in this paper.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPML068

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPML069

The Control System Design of SCLF

4800

Y.B. Yan, J.G. Ding, G.Y. Jiang, Y.B. Leng
SSRF, Shanghai, People's Republic of China
J.F. Chen
SINAP, Shanghai, People's Republic of China

The high-gain free electron lasers have given scientists hopes for new scientific discoveries in many frontier research areas. The Shanghai Coherent Light Facility (SCLF) was proposed by the central government of China on April 2017, which is a quasi-continuous wave hard X-ray free electron laser facility. The control system is responsible for the facility-wide device control, data acquisition, machine protection, high level database or application, as well as network and computing platform. It will be mainly based on EPICS to reach the balance between the high performance and costs of maintenance. The latest technology will be adopted for the high repetition rate data acquisition and feedback system. The details of the control system design will be reported in this paper.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPML069

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPML070

Point Spread Function Study of Quasi-Monochromatic X-Ray Pinhole Camera at SSRF

4803

B. Gao, H.J. Chen
SINAP, Shanghai, People's Republic of China
J. Chen, Y.B. Leng
SSRF, Shanghai, People's Republic of China

Since 2009 an X-ray pinhole camera that has been used to present the transverse beam size and emittance on diagnostic beam line of the storage ring at SSRF. The real beam size is a function of the image size of the CCD camera and point spread function (PSF) of the system. The performance of the measurement of the transverse electron beam size is given by the width of the PSF of X-ray pinhole camera. The contributions to the PSF width are the PSF of pinhole itself due to diffraction, and the PSF of the screen and camera. An X-ray monochromatic system has been established to measure the PSF accurately, and decrease the variation in the beam size between the theoretical values and the measured ones at SSRF. In this article, both calculated and measured PSF of quasi-monochromatic X-ray pinhole camera will be presented in detail.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPML070

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPML071

Upgrade of Digital BPM Processor at DCLS and SXFEL

4807

L.W. Lai, F.Z. Chen, Y.B. Leng, T. Wu, Y.B. Yan
SSRF, Shanghai, People's Republic of China
J. Chen
SINAP, Shanghai, People's Republic of China

A digital BPM processor has been developed at 2016 in SINAP for DCLS and SXFEL, which are FEL facilities built in China. The stripline BPM and cavity BPM processors share the same hardware platform and firmware, but the processing algorithms implemented in EPICS IOC on the ARM CPU are different. The capability of the ARM limits the processing speed to 10 bunches per second. Now the bunch rate of DCLS and SXFEL are going to increase from 10Hz to 50Hz. To meet the higher processing speed requirements, the processor firmware and software are upgraded in 2017. All BPM signal processing algorithms are implemented in FPGA, and EPICS IOC reads results only. After the upgrade, the processing speed reach 120 bunches per second. And this is also a good preparation for future Shanghai Hard-X ray FEL, which bunch rate is about 1MHz.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPML071

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)