NAPAC2016 - List of Authors (Xu, Y.L.)

Paper	Title	Page
TUPOA40	Low Noise Digitizer Design for LCLS-II LLRF	364
	G. Huang, L.R. Doolittle, Y.L. Xu, J. Yang LBNL, Berkeley, California, USA Y.L. Xu, J. Yang TUB, Beijing, People's Republic of China
	Modern accelerators use a digital low level RF controller to stabilize the fields in accelerator cavities. The noise in the receiver chain and analog to digital conversion (ADC) for the cavity probe signal is critically important. Within the closed-loop bandwidth, it will eventually become part of the field noise seen by the beam in the accelerator. Above the open-loop cavity bandwidth, feedback processes transfer that noise to the high power drive amplifiers. The LCLS-II project is expected to use an undulator to provide soft X-rays based on a stable electron beam accelerated by a superconducting linac. Project success depends on a low noise, low crosstalk analog to digital conversion. We developed a digitizer board with 8 ADC channels and 2 DAC channels. The broadband phase noise of this board is measured at <-151\thinspace dBc/Hz, and the adjacent channel crosstalk is measured at <-80\thinspace dB. In this paper we describe the digitizer board design, performance test procedures, and bench-test results.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2016-TUPOA40
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TUPOA41	FPGA Control of Coherent Pulse Stacking	367
SUPO52	use link to see paper's listing under its alternate paper code
	Y.L. Xu, J.M. Byrd, L.R. Doolittle, Q. Du, G. Huang, W. Leemans, R.B. Wilcox, Y. Yang LBNL, Berkeley, California, USA J. Dawson LLNL, Livermore, California, USA A. Galvanauskas, J.M. Ruppe University of Michigan, Ann Arbor, Michigan, USA
	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 from fiber lasers. Due to advantages of precise timing and fast processing, we use an FPGA to process digital signals and do feedback control so as to realize stacking-cavity stabilization. We develop a hardware and firmware design platform to support the coherent pulse stacking application. A firmware bias control module stabilizes the amplitude modulator at the minimum of its transfer function. A cavity control module ensures that each optical cavity is kept at a certain individually-prescribed and stable round-trip phase with 2.5 deg rms phase error.
	Poster TUPOA41 [5.546 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2016-TUPOA41
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TUPOA42	Multicavity Coherent Pulse Stacking Using Herriott Cells	370
	Y. Yang, J.M. Byrd, L.R. Doolittle, G. Huang, W. Leemans, Q. Qiang, R.B. Wilcox LBNL, Berkeley, California, USA J. Dawson LLNL, Livermore, California, USA A. Galvanauskas, J.M. Ruppe University of Michigan, Ann Arbor, Michigan, USA Y.L. Xu TUB, Beijing, People's Republic of China
	Coherent Pulse Stacking provides a promising way to generate a single high-intensity laser pulse by stacking a sequence of phase and amplitude modulated laser pulses using multiple optical cavities. Optical misalignment and phase stability are two critical issues that need to be addressed. Herriott cells are implemented for their relaxed alignment tolerance and a phase stabilization method based on cavity output pattern matching has been developed. A single pulse with intensity enhancement factor over 7.4 has been generated by stacking 13 modulated pules through a four-cavity stacking system. This can be a possible path for generating TW KHz laser pulses for a future laser-driven plasma accelerator.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2016-TUPOA42
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

Paper

Title

Page

Low Noise Digitizer Design for LCLS-II LLRF

364

G. Huang, L.R. Doolittle, Y.L. Xu, J. Yang
LBNL, Berkeley, California, USA
Y.L. Xu, J. Yang
TUB, Beijing, People's Republic of China

Modern accelerators use a digital low level RF controller to stabilize the fields in accelerator cavities. The noise in the receiver chain and analog to digital conversion (ADC) for the cavity probe signal is critically important. Within the closed-loop bandwidth, it will eventually become part of the field noise seen by the beam in the accelerator. Above the open-loop cavity bandwidth, feedback processes transfer that noise to the high power drive amplifiers. The LCLS-II project is expected to use an undulator to provide soft X-rays based on a stable electron beam accelerated by a superconducting linac. Project success depends on a low noise, low crosstalk analog to digital conversion. We developed a digitizer board with 8 ADC channels and 2 DAC channels. The broadband phase noise of this board is measured at <-151\thinspace dBc/Hz, and the adjacent channel crosstalk is measured at <-80\thinspace dB. In this paper we describe the digitizer board design, performance test procedures, and bench-test results.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2016-TUPOA40

Export •

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

TUPOA41

FPGA Control of Coherent Pulse Stacking

367

SUPO52

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

Y.L. Xu, J.M. Byrd, L.R. Doolittle, Q. Du, G. Huang, W. Leemans, R.B. Wilcox, Y. Yang
LBNL, Berkeley, California, USA
J. Dawson
LLNL, Livermore, California, USA
A. Galvanauskas, J.M. Ruppe
University of Michigan, Ann Arbor, Michigan, USA

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 from fiber lasers. Due to advantages of precise timing and fast processing, we use an FPGA to process digital signals and do feedback control so as to realize stacking-cavity stabilization. We develop a hardware and firmware design platform to support the coherent pulse stacking application. A firmware bias control module stabilizes the amplitude modulator at the minimum of its transfer function. A cavity control module ensures that each optical cavity is kept at a certain individually-prescribed and stable round-trip phase with 2.5 deg rms phase error.

Poster TUPOA41 [5.546 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2016-TUPOA41

Export •

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

TUPOA42

Multicavity Coherent Pulse Stacking Using Herriott Cells

370

Y. Yang, J.M. Byrd, L.R. Doolittle, G. Huang, W. Leemans, Q. Qiang, R.B. Wilcox
LBNL, Berkeley, California, USA
J. Dawson
LLNL, Livermore, California, USA
A. Galvanauskas, J.M. Ruppe
University of Michigan, Ann Arbor, Michigan, USA
Y.L. Xu
TUB, Beijing, People's Republic of China

Coherent Pulse Stacking provides a promising way to generate a single high-intensity laser pulse by stacking a sequence of phase and amplitude modulated laser pulses using multiple optical cavities. Optical misalignment and phase stability are two critical issues that need to be addressed. Herriott cells are implemented for their relaxed alignment tolerance and a phase stabilization method based on cavity output pattern matching has been developed. A single pulse with intensity enhancement factor over 7.4 has been generated by stacking 13 modulated pules through a four-cavity stacking system. This can be a possible path for generating TW KHz laser pulses for a future laser-driven plasma accelerator.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2016-TUPOA42

Export •

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