IPAC2019 - List of Authors (Li, R.K.)

Paper	Title	Page
THXXPLS3	Science Frontiers of Megaelectronvolt Ultrafast Electron Probes
	X.J. Wang, R.K. Li, X. Shen, J. Yang SLAC, Menlo Park, California, USA
	Ultrafast electron probe is the new frontier for electron scattering instrumentations. The development in high-brightness electron beam made it feasible to explore megaelectronvolt electrons for Ultrafast Electron diffraction and Microsscopy (MeV-UED/UEM). Recent development in MeV-UED [2-3] has enabled broad scientific opportunities in ultrafast material science and chemical dynamics, such as the ripples of monolayer MoS2 and atomic movie of light-induced structural distortion in the perovskites solar cell were captured for the first time by the MeV-UED. Single-shot MeV-UED was successfully employed for the first observation of heterogeneous melting. In the gas phase UED, real space movie of a nuclear wavepacket passing through conical intersections was sucesffuly recorded *. To probe and controlling electron motion within a molecule and image bio-molecules in its nature environments, new generation electron scattering instruments with better time resolution, higher sensitivity and real space imaging are needed. SLAC’s strategy for next generation ultrafast electron instrument based on the superconductor RF gun will be discussed. X.J. Wang et al, Phys. Rev. E , 54, No.4, R3121 -3124 (1996). M. Z. Mo et al, Science 360 1451-1455 (2018). * J. Yang et al, Science, 361, 64-67. (2018).
	Slides THXXPLS3 [12.167 MB]
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPGW079	THz-Based Femtosecond MeV Electron Bunch Compression	3766
	M.A.K. Othman, M.C. Hoffmann, M.E. Kozina, R.K. Li, E.A. Nanni, X. Shen, E.J. Snively, X.J. Wang SLAC, Menlo Park, California, USA
	Funding: This work was supported by Department of Energy contract DE-AC02-76SF00515. Probing structural dynamics at atomic spatial and ultrashort temporal scales reveals unprecedented details of fundamental behavior of nature, allowing for better understanding of intricate energy-matter interaction occurring at such scales. Developing state-of-the-art technology to access these details entails utilizing X-ray free-electron lasers (XFELs), ultrafast electron diffraction (UED), and advanced electron microscopes. In particular, ultrafast diffraction science received growing attention thanks to innovation in sources, detectors and instrumentation in general. Within this context, interest in laser-generated THz wave-matter interaction has recently emerged as a new regime for controlling electrons with high temporal precision. Previously, the SLAC UED team has demonstrated attosecond electron metrology using laser-generated single-cycle THz radiation, which is intrinsically phase locked to the optical drive pulses, to manipulate multi-MeV relativistic electron beams. Here we demonstrate further steps towards achieving ultrafast timing resolution that utilizes femtosecond electron bunches. The proposed setup allows for compressing electron beam bunches down to a femtosecond using interaction with high field single-cycle THz pulses. We demonstrate a novel design of a dispersion-free parallel-plate tapered waveguide that provides focusing of THz pulses achieving >100 MV/m field strength at the interaction point as measured by electro-optical sampling for ~7 μJ of incoming THz pulse energy. The structure is being designed and built for bunch compression experiments using the SLAC UED facility.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPGW079
About •	paper received ※ 15 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUPTS053	Design of a 217 MHz VHF Gun at Tsinghua University	2050
SUSPFO084	use link to see paper's listing under its alternate paper code
	L.M. Zheng, H. Chen, Y.C. Du, W.-H. Huang, R.K. Li, Z.Z. Li, C.-X. Tang TUB, Beijing, People’s Republic of China B. Gao IHEP, Beijing, People’s Republic of China
	A 217 MHz VHF gun operating in CW mode is designing at Tsinghua University. The cathode gradient is designed to be 30 MV/m to accelerate the electron bunches up to 878 keV. The cavity profile is optimized in CST to minimize the input power, peak surface electric field, and peak wall power density. The multipacting analysis and the thermal analysis are also presented in this paper. Further gun shape optimization and mechanical design are ongoing.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPTS053
About •	paper received ※ 15 May 2019 paper accepted ※ 18 May 2019 issue date ※ 21 June 2019
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

Paper

Title

Page

THXXPLS3

Science Frontiers of Megaelectronvolt Ultrafast Electron Probes

X.J. Wang, R.K. Li, X. Shen, J. Yang
SLAC, Menlo Park, California, USA

Ultrafast electron probe is the new frontier for electron scattering instrumentations. The development in high-brightness electron beam made it feasible to explore megaelectronvolt electrons for Ultrafast Electron diffraction and Microsscopy (MeV-UED/UEM)*. Recent development in MeV-UED [2-3] has enabled broad scientific opportunities in ultrafast material science and chemical dynamics, such as the ripples of monolayer MoS2 and atomic movie of light-induced structural distortion in the perovskites solar cell were captured for the first time by the MeV-UED. Single-shot MeV-UED was successfully employed for the first observation of heterogeneous melting**. In the gas phase UED, real space movie of a nuclear wavepacket passing through conical intersections was sucesffuly recorded ***. To probe and controlling electron motion within a molecule and image bio-molecules in its nature environments, new generation electron scattering instruments with better time resolution, higher sensitivity and real space imaging are needed. SLAC’s strategy for next generation ultrafast electron instrument based on the superconductor RF gun will be discussed.
* X.J. Wang et al, Phys. Rev. E , 54, No.4, R3121 -3124 (1996).
** M. Z. Mo et al, Science 360 1451-1455 (2018).
*** J. Yang et al, Science, 361, 64-67. (2018).

Slides THXXPLS3 [12.167 MB]

Export •

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

THPGW079

THz-Based Femtosecond MeV Electron Bunch Compression

3766

M.A.K. Othman, M.C. Hoffmann, M.E. Kozina, R.K. Li, E.A. Nanni, X. Shen, E.J. Snively, X.J. Wang
SLAC, Menlo Park, California, USA

Funding: This work was supported by Department of Energy contract DE-AC02-76SF00515.
Probing structural dynamics at atomic spatial and ultrashort temporal scales reveals unprecedented details of fundamental behavior of nature, allowing for better understanding of intricate energy-matter interaction occurring at such scales. Developing state-of-the-art technology to access these details entails utilizing X-ray free-electron lasers (XFELs), ultrafast electron diffraction (UED), and advanced electron microscopes. In particular, ultrafast diffraction science received growing attention thanks to innovation in sources, detectors and instrumentation in general. Within this context, interest in laser-generated THz wave-matter interaction has recently emerged as a new regime for controlling electrons with high temporal precision. Previously, the SLAC UED team has demonstrated attosecond electron metrology using laser-generated single-cycle THz radiation, which is intrinsically phase locked to the optical drive pulses, to manipulate multi-MeV relativistic electron beams. Here we demonstrate further steps towards achieving ultrafast timing resolution that utilizes femtosecond electron bunches. The proposed setup allows for compressing electron beam bunches down to a femtosecond using interaction with high field single-cycle THz pulses. We demonstrate a novel design of a dispersion-free parallel-plate tapered waveguide that provides focusing of THz pulses achieving >100 MV/m field strength at the interaction point as measured by electro-optical sampling for ~7 μJ of incoming THz pulse energy. The structure is being designed and built for bunch compression experiments using the SLAC UED facility.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPGW079

About •

paper received ※ 15 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

Export •

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

TUPTS053

Design of a 217 MHz VHF Gun at Tsinghua University

2050

SUSPFO084

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

L.M. Zheng, H. Chen, Y.C. Du, W.-H. Huang, R.K. Li, Z.Z. Li, C.-X. Tang
TUB, Beijing, People’s Republic of China
B. Gao
IHEP, Beijing, People’s Republic of China

A 217 MHz VHF gun operating in CW mode is designing at Tsinghua University. The cathode gradient is designed to be 30 MV/m to accelerate the electron bunches up to 878 keV. The cavity profile is optimized in CST to minimize the input power, peak surface electric field, and peak wall power density. The multipacting analysis and the thermal analysis are also presented in this paper. Further gun shape optimization and mechanical design are ongoing.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPTS053

About •

paper received ※ 15 May 2019 paper accepted ※ 18 May 2019 issue date ※ 21 June 2019

Export •

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