IPAC2018 - List of Authors (Huang, G.)

Paper	Title	Page
WEPAL039	LCLS-II Gun/Buncher LLRF System Design	2258
	G. Huang, K.S. Campbell, L.R. Doolittle, J.A. Jones, Q. Qiang, C. Serrano LBNL, Berkeley, California, USA S. Babel, A.L. Benwell, M. Boyes, G.W. Brown, D. Cha, J.H. De Long, J.A. Diaz Cruz, B. Hong, A. McCollough, A. Ratti, C.H. Rivetta, D. Rogind, F. Zhou SLAC, Menlo Park, California, USA R. Bachimanchi, C. Hovater, D.J. Seidman JLab, Newport News, Virginia, USA B.E. Chase, E. Cullerton, J. Einstein-Curtis, D.W. Klepec Fermilab, Batavia, Illinois, USA J.A. Diaz Cruz CSU, Fort Collins, Colorado, USA
	Funding: This work was supported by the LCLS-II Project and the U.S. Department of Energy, Contract n. DE-AC02-05CH11231. For a free electron laser, the stability of injector is critical to the final electron beam parameters, e.g., beam energy, beam arrival time, and eventually it determines the photon quality. The LCLS-II project's injector contains a VHF copper cavity as the gun and a two-cell L-band copper cavity as its buncher. The cavity designs are inherited from the APEX design, but requires more field stability than demonstrated in APEX operation. The gun LLRF system design uses a connectorized RF front end and low noise digitizer, together with the same general purpose FPGA carrier board used in the LCLS-II SRF LLRF system. The buncher LLRF system directly adopts the SRF LLRF chassis design, but programs the controller to run the normal conducting cavities. In this paper, we describe the gun/buncher LLRF system design, including the hardware design, the firmware design and bench test.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPAL039
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WEPAL040	High Precision Synchronization Development for HiRES, the Ultrafast Electron Diffraction Beamline at LBNL	2262
	Y. Yang, K.M. Baptiste, M. Betz, L.R. Doolittle, Q. Du, D. Filippetto, G. Huang, F. Ji LBNL, Berkeley, California, USA
	Precise synchronization between the laser and electron is critical for the pump-probe experiments in the HiRES Ultrafast Electron Diffraction facility. We are upgrading the LLRF and laser control system, which ultimately aims at a synchronization below 50 fs RMS between the pump laser pulse and electron probe at the sample plane. Such target poses tight requirements on the RF field stability both in amplitude and phase, and on the synchronization between the RF field and the laser repetition rate. We are presently developing a new LLRF system that has the potential to decrease the overall noise, reaching the required stability of tens of ppm on RF amplitude and phase. For the laser control side, we are replacing the long coaxial cables with fibers for both control signal transmission and laser signal reception. The control transmission side has been implemented, and the timing jitter has been reduced.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPAL040
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WEPAL041	FPGA Based Optical Phase Control for Coherent Laser Pulse Stacking	2265
	Y. Yang, L.R. Doolittle, Q. Du, G. Huang, W. Leemans, R.B. Wilcox, T. Zhou LBNL, Berkeley, California, USA A. Galvanauskas University of Michigan, Ann Arbor, Michigan, USA
	Coherent temporal pulse stacking combines the energy from a train of pulses into one pulse through a series of optical cavities. To stabilize the output energy, the cavity roundtrip phases must be precisely locked to particular values. Leveraging the LLRF expertise we have for conventional accelerators, a FPGA-based control system has been developed for optical cavity phase control. A phase measurement method, ''Modulated Impulse Response'', has been developed and implemented on FPGA. An experiment demonstrated that it can measure and lock the optical phases of four stacking cavities, leading to combination of 25 pulses into one pulse with 1.5 % RMS stability over 30 hours.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPAL041
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THYGBE3	RF Controls for High-Q Cavities for the LCLS-II	2929
	C. Serrano, K.S. Campbell, L.R. Doolittle, G. Huang, A. Ratti LBNL, Berkeley, California, USA R. Bachimanchi, C. Hovater JLab, Newport News, Virginia, USA A.L. Benwell, M. Boyes, G.W. Brown, D. Cha, G. Dalit, J.A. Diaz Cruz, J. Jones, R.S. Kelly, A. McCollough SLAC, Menlo Park, California, USA B.E. Chase, E. Cullerton, J. Einstein-Curtis, J.P. Holzbauer, D.W. Klepec, Y.M. Pischalnikov, W. Schappert Fermilab, Batavia, Illinois, USA L.R. Dalesio, M.A. Davidsaver Osprey DCS LLC, Ocean City, USA
	Funding: This work was supported by the LCLS-II Project and the U.S. Department of Energy, Contract n. DE-AC02-76SF00515. The SLAC National Accelerator Laboratory is building LCLS-II, a new 4 GeV CW superconducting (SCRF) Linac as a major upgrade of the existing LCLS. The LCLS-II Low-Level Radio Frequency (LLRF) collaboration is a multi-lab effort within the Department of Energy (DOE) accelerator complex. The necessity of high longitudinal beam stability of LCLS-II imposes tight amplitude and phase stability requirements on the LLRF system (up to 0.01% in amplitude and 0.01° in phase RMS). This is the first time such requirements are expected of superconducting cavities operating in continuous-wave (CW) mode. Initial measurements on the Cryomodule test stands at partner labs have shown that the early production units are able to meet the extrapolated hardware requirements to achieve such levels of performance. A large effort is currently underway for system integration, Experimental Physics and Industrial Control System (EPICS) controls, transfer of knowledge from the partner labs to SLAC and the production and testing of 76 racks of LLRF equipment.
	Slides THYGBE3 [14.383 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THYGBE3
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THPML099	Phase Extraction and Stabilization for Coherent Pulse Stacking	4895
SUSPL060	use link to see paper's listing under its alternate paper code
	Y.L. Xu, W.-H. Huang, C.-X. Tang, L.X. Yan TUB, Beijing, People's Republic of China L.R. Doolittle, Q. Du, G. Huang, W. Leemans, D. Li, R.B. Wilcox, Y. Yang, T. Zhou LBNL, Berkeley, California, USA A. Galvanauskas University of Michigan, Ann Arbor, Michigan, USA
	Funding: This work was supported by the U.S. Department of Energy, Office of Science, Office of High Energy Physics, under Contract DE-AC02-05CH11231. Coherent pulse stacking (CPS) is a new time-domain coherent addition technique that stacks several optical pulses into a single output pulse, enabling high pulse energy and high average power. We model the CPS as a digital filter in the Z domain, and implement two deterministic algorithms extracting the cavity phase from limited data where only the pulse intensity is available. In a 2-stage 15-pulse CPS system, each optical cavity is stabilized at an individually-prescribed round-trip phase with 0.7 deg and 2.1 deg RMS phase errors for Stage 1 and Stage 2 respectively. Optical cavity phase control with nm accuracy ensures 1.2% intensity stability of the stacked pulse over 12 hours.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPML099
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THPML100	A High Voltage Feedforward Subsystem of Low Level RF System for the High Power RF System	4898
SUSPL062	use link to see paper's listing under its alternate paper code
	Z.Y. Lin, Y. C. Du, H.Q. Feng, W.-H. Huang, CY. Song, C.-X. Tang, Y.L. Xu, J. Yang TUB, Beijing, People's Republic of China G. Huang LBNL, Berkeley, California, USA
	The Low Level Radio Frequency control (LLRF) system measures the RF signals from the accelerator tube, compares it with the phase reference received from the timing distribution system, and provides the drive signal to the high power RF system to provide synchronized RF voltage to the electron beam. Usually, the LLRF system can achieve a ~50 fs RMS phase jitter which is limited by the microwave devices. The phase noise arise from the high voltage variation of the high power system will significantly increase phase noise from low level RF signal to high power RF. A high voltage feed forward subsystem is proposed to deal with the phase noise caused by the high voltage jitter of the modulator. The demo system is depolyed in Thomson scattering X-ray source (TTX).and the primary experiment result anaylse is discussed.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPML100
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THPML101	A Novel Double Sideband-Based Phase Averaging Line for Phase Reference Distribution System	4901
	Z.Y. Lin, Y.-C. Du, W.-H. Huang, Z. Pan, C.-X. Tang, C.-X. Tang, Y.L. Xu, J. Yang TUB, Beijing, People's Republic of China G. Huang LBNL, Berkeley, California, USA
	Coaxial cable based solution is one of the most important scheme in Phase Reference Distribution System. A novel double sideband-based phase averaging line has been developed in Tsinghua accelerator lab. The sender chassis generates the 2856 MHz signal as the forward signal and receives the 2856 MHz signal and the reflected double sideband signal from the receiver. The forward signal is phase-locked with the reference signal, and the forward signal and the sideband signal are adjusted by the FPGA virtual delay line. The preliminary experiments result shows the phase stability can achieve about 1% by signal distorted by the phase shifter.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPML101
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Paper

Title

Page

LCLS-II Gun/Buncher LLRF System Design

2258

G. Huang, K.S. Campbell, L.R. Doolittle, J.A. Jones, Q. Qiang, C. Serrano
LBNL, Berkeley, California, USA
S. Babel, A.L. Benwell, M. Boyes, G.W. Brown, D. Cha, J.H. De Long, J.A. Diaz Cruz, B. Hong, A. McCollough, A. Ratti, C.H. Rivetta, D. Rogind, F. Zhou
SLAC, Menlo Park, California, USA
R. Bachimanchi, C. Hovater, D.J. Seidman
JLab, Newport News, Virginia, USA
B.E. Chase, E. Cullerton, J. Einstein-Curtis, D.W. Klepec
Fermilab, Batavia, Illinois, USA
J.A. Diaz Cruz
CSU, Fort Collins, Colorado, USA

Funding: This work was supported by the LCLS-II Project and the U.S. Department of Energy, Contract n. DE-AC02-05CH11231.
For a free electron laser, the stability of injector is critical to the final electron beam parameters, e.g., beam energy, beam arrival time, and eventually it determines the photon quality. The LCLS-II project's injector contains a VHF copper cavity as the gun and a two-cell L-band copper cavity as its buncher. The cavity designs are inherited from the APEX design, but requires more field stability than demonstrated in APEX operation. The gun LLRF system design uses a connectorized RF front end and low noise digitizer, together with the same general purpose FPGA carrier board used in the LCLS-II SRF LLRF system. The buncher LLRF system directly adopts the SRF LLRF chassis design, but programs the controller to run the normal conducting cavities. In this paper, we describe the gun/buncher LLRF system design, including the hardware design, the firmware design and bench test.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPAL039

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WEPAL040

High Precision Synchronization Development for HiRES, the Ultrafast Electron Diffraction Beamline at LBNL

2262

Y. Yang, K.M. Baptiste, M. Betz, L.R. Doolittle, Q. Du, D. Filippetto, G. Huang, F. Ji
LBNL, Berkeley, California, USA

Precise synchronization between the laser and electron is critical for the pump-probe experiments in the HiRES Ultrafast Electron Diffraction facility. We are upgrading the LLRF and laser control system, which ultimately aims at a synchronization below 50 fs RMS between the pump laser pulse and electron probe at the sample plane. Such target poses tight requirements on the RF field stability both in amplitude and phase, and on the synchronization between the RF field and the laser repetition rate. We are presently developing a new LLRF system that has the potential to decrease the overall noise, reaching the required stability of tens of ppm on RF amplitude and phase. For the laser control side, we are replacing the long coaxial cables with fibers for both control signal transmission and laser signal reception. The control transmission side has been implemented, and the timing jitter has been reduced.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPAL040

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WEPAL041

FPGA Based Optical Phase Control for Coherent Laser Pulse Stacking

2265

Y. Yang, L.R. Doolittle, Q. Du, G. Huang, W. Leemans, R.B. Wilcox, T. Zhou
LBNL, Berkeley, California, USA
A. Galvanauskas
University of Michigan, Ann Arbor, Michigan, USA

Coherent temporal pulse stacking combines the energy from a train of pulses into one pulse through a series of optical cavities. To stabilize the output energy, the cavity roundtrip phases must be precisely locked to particular values. Leveraging the LLRF expertise we have for conventional accelerators, a FPGA-based control system has been developed for optical cavity phase control. A phase measurement method, ''Modulated Impulse Response'', has been developed and implemented on FPGA. An experiment demonstrated that it can measure and lock the optical phases of four stacking cavities, leading to combination of 25 pulses into one pulse with 1.5 % RMS stability over 30 hours.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPAL041

Export •

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THYGBE3

RF Controls for High-Q Cavities for the LCLS-II

2929

C. Serrano, K.S. Campbell, L.R. Doolittle, G. Huang, A. Ratti
LBNL, Berkeley, California, USA
R. Bachimanchi, C. Hovater
JLab, Newport News, Virginia, USA
A.L. Benwell, M. Boyes, G.W. Brown, D. Cha, G. Dalit, J.A. Diaz Cruz, J. Jones, R.S. Kelly, A. McCollough
SLAC, Menlo Park, California, USA
B.E. Chase, E. Cullerton, J. Einstein-Curtis, J.P. Holzbauer, D.W. Klepec, Y.M. Pischalnikov, W. Schappert
Fermilab, Batavia, Illinois, USA
L.R. Dalesio, M.A. Davidsaver
Osprey DCS LLC, Ocean City, USA

Funding: This work was supported by the LCLS-II Project and the U.S. Department of Energy, Contract n. DE-AC02-76SF00515.
The SLAC National Accelerator Laboratory is building LCLS-II, a new 4 GeV CW superconducting (SCRF) Linac as a major upgrade of the existing LCLS. The LCLS-II Low-Level Radio Frequency (LLRF) collaboration is a multi-lab effort within the Department of Energy (DOE) accelerator complex. The necessity of high longitudinal beam stability of LCLS-II imposes tight amplitude and phase stability requirements on the LLRF system (up to 0.01% in amplitude and 0.01° in phase RMS). This is the first time such requirements are expected of superconducting cavities operating in continuous-wave (CW) mode. Initial measurements on the Cryomodule test stands at partner labs have shown that the early production units are able to meet the extrapolated hardware requirements to achieve such levels of performance. A large effort is currently underway for system integration, Experimental Physics and Industrial Control System (EPICS) controls, transfer of knowledge from the partner labs to SLAC and the production and testing of 76 racks of LLRF equipment.

Slides THYGBE3 [14.383 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THYGBE3

Export •

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

THPML099

Phase Extraction and Stabilization for Coherent Pulse Stacking

4895

SUSPL060

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

Y.L. Xu, W.-H. Huang, C.-X. Tang, L.X. Yan
TUB, Beijing, People's Republic of China
L.R. Doolittle, Q. Du, G. Huang, W. Leemans, D. Li, R.B. Wilcox, Y. Yang, T. Zhou
LBNL, Berkeley, California, USA
A. Galvanauskas
University of Michigan, Ann Arbor, Michigan, USA

Funding: This work was supported by the U.S. Department of Energy, Office of Science, Office of High Energy Physics, under Contract DE-AC02-05CH11231.
Coherent pulse stacking (CPS) is a new time-domain coherent addition technique that stacks several optical pulses into a single output pulse, enabling high pulse energy and high average power. We model the CPS as a digital filter in the Z domain, and implement two deterministic algorithms extracting the cavity phase from limited data where only the pulse intensity is available. In a 2-stage 15-pulse CPS system, each optical cavity is stabilized at an individually-prescribed round-trip phase with 0.7 deg and 2.1 deg RMS phase errors for Stage 1 and Stage 2 respectively. Optical cavity phase control with nm accuracy ensures 1.2% intensity stability of the stacked pulse over 12 hours.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPML099

Export •

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THPML100

A High Voltage Feedforward Subsystem of Low Level RF System for the High Power RF System

4898

SUSPL062

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

Z.Y. Lin, Y. C. Du, H.Q. Feng, W.-H. Huang, CY. Song, C.-X. Tang, Y.L. Xu, J. Yang
TUB, Beijing, People's Republic of China
G. Huang
LBNL, Berkeley, California, USA

The Low Level Radio Frequency control (LLRF) system measures the RF signals from the accelerator tube, compares it with the phase reference received from the timing distribution system, and provides the drive signal to the high power RF system to provide synchronized RF voltage to the electron beam. Usually, the LLRF system can achieve a ~50 fs RMS phase jitter which is limited by the microwave devices. The phase noise arise from the high voltage variation of the high power system will significantly increase phase noise from low level RF signal to high power RF. A high voltage feed forward subsystem is proposed to deal with the phase noise caused by the high voltage jitter of the modulator. The demo system is depolyed in Thomson scattering X-ray source (TTX).and the primary experiment result anaylse is discussed.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPML100

Export •

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

THPML101

A Novel Double Sideband-Based Phase Averaging Line for Phase Reference Distribution System

4901

Z.Y. Lin, Y.-C. Du, W.-H. Huang, Z. Pan, C.-X. Tang, C.-X. Tang, Y.L. Xu, J. Yang
TUB, Beijing, People's Republic of China
G. Huang
LBNL, Berkeley, California, USA

Coaxial cable based solution is one of the most important scheme in Phase Reference Distribution System. A novel double sideband-based phase averaging line has been developed in Tsinghua accelerator lab. The sender chassis generates the 2856 MHz signal as the forward signal and receives the 2856 MHz signal and the reflected double sideband signal from the receiver. The forward signal is phase-locked with the reference signal, and the forward signal and the sideband signal are adjusted by the FPGA virtual delay line. The preliminary experiments result shows the phase stability can achieve about 1% by signal distorted by the phase shifter.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPML101

Export •

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