IPAC2017 - List of Authors (Graves, W.S.)

Paper	Title	Page
MOPAB150	Imaging the Spatial Modulation of a Relativistic Electron Beam	480
	C. Zhang, W.S. Graves, L.E. Malin, J. Spence Arizona State University, Tempe, USA D.B. Cesar, J.M. Maxson, P. Musumeci, A. Urbanowicz UCLA, Los Angeles, USA C. Limborg, E.A. Nanni SLAC, Menlo Park, California, USA
	Funding: Work supported by NSF awards 1632780, 1415583, 1231306 and DOE award de-sc0009914 We describe Bragg diffraction of relativistic electron beams through a patterned Si crystal consisting of alternating thick and thin strips to produce nanometer scale electron density modulations. Multi-slice simulations show that a two-beam situation can be set up where, for a particular thickness of Si, nearly 100% of the electron beam is diffracted. Plans are underway to carry out experiments showing this effect in UCLA's ultrafast electron microscopy lab with 3.5 MeV electrons. We will select either the diffracted beam or the primary beam with a small aperture in the diffraction plane of a magnetic lens, and so record either the dark or bright field magnified image of the strips. Our first goal is to observe the nanopatterned beam at the image plane. We will then investigate various crystal thickness and sample orientations to maximize the contrast in the pattern and explore tuning the period of the modulation through varying magnification.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPAB150
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TUPAB139	Design of an X-Band Photoinjector Operating at 1 kHz	1659
	W.S. Graves, A.C. Goodrich, M.R. Holl, N.J. O'Brien Arizona State University, Tempe, USA V. Bharadwaj, P. Borchard Tibaray Inc., Stanford, USA V.A. Dolgashev, E.A. Nanni SLAC, Menlo Park, California, USA
	A kHz repetition rate RF photoinjector with novel features has been designed for the ASU CXLS project. The photoinjector consists of a 9.3 GHz 4.5 cell standing-wave RF cavity that is constructed from 2 halves. The halves are brazed together, with the braze joint bisecting the irises and cells, greatly simplifying its construction. The cathode is brazed onto this assembly. RF power is coupled into the cavity through inline circular waveguide using a demountable TM01 mode launcher. The mode launcher feeds the power through 4 ports distributed azimuthally to eliminate both dipole and quadrupole field distortions. The brazed-in cathode and absence of complex power coupler result in a very inexpensive yet high performance device. The clean design allows the RF cavity to sit entirely within the solenoid assembly. The cathode gradient is 120 MV/m at 3 MW of input power. The cathode cell is just 0.17 RF wavelength so that laser arrival phase for peak acceleration is 70 degrees from zero crossing resulting in exit energy of 4 MeV. The photoinjector will operate with 1μs pulses at 1 kHz, dissipating 3 kW of heat. Details of the design are presented.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-TUPAB139
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THPAB088	Comparison of Theory, Simulation, and Experiment for Dynamical Extinction of Relativistic Electron Beams Diffracted Through a Si Crystal Membrane	3924
SUSPSIK064	use link to see paper's listing under its alternate paper code
	L.E. Malin, W.S. Graves, J. Spence, C. Zhang Arizona State University, Tempe, USA R.K. Li, C. Limborg, E.A. Nanni, X. Shen, S.P. Weathersby SLAC, Menlo Park, California, USA
	Diffraction in the transmission geometry through a single-crystal silicon slab is exploited to control the intensity of a relativistic electron beam. The choice of crystal thickness and incidence angle can extinguish or maximize the transmitted beam intensity via coherent multiple Bragg scattering; thus, the crystal acts as a dynamical beam stop through the Pendel'sung effect, a well-known phenomenon in X-ray and electron diffraction. In an initial experiment, we have measured the ability of this method to transmit or extinguish the primary beam and diffract into a single Bragg peak. Using lithographic etching of patterns in the crystal we intend to use this method to nanopattern an electron beam for production of coherent x-rays. We compare the experimental results with simulations using the multislice method to model the diffraction pattern from a perfect silicon crystal of uniform thickness, considering multiple scattering, crystallographic orientation, temperature effects, and partial coherence from the momentum spread of the beam. The simulations are compared to data collected at the ASTA UED facility at SLAC for a 340 nm thick Si(100) wafer with a beam energy of 2.35 MeV.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPAB088
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Paper

Title

Page

Imaging the Spatial Modulation of a Relativistic Electron Beam

480

C. Zhang, W.S. Graves, L.E. Malin, J. Spence
Arizona State University, Tempe, USA
D.B. Cesar, J.M. Maxson, P. Musumeci, A. Urbanowicz
UCLA, Los Angeles, USA
C. Limborg, E.A. Nanni
SLAC, Menlo Park, California, USA

Funding: Work supported by NSF awards 1632780, 1415583, 1231306 and DOE award de-sc0009914
We describe Bragg diffraction of relativistic electron beams through a patterned Si crystal consisting of alternating thick and thin strips to produce nanometer scale electron density modulations. Multi-slice simulations show that a two-beam situation can be set up where, for a particular thickness of Si, nearly 100% of the electron beam is diffracted. Plans are underway to carry out experiments showing this effect in UCLA's ultrafast electron microscopy lab with 3.5 MeV electrons. We will select either the diffracted beam or the primary beam with a small aperture in the diffraction plane of a magnetic lens, and so record either the dark or bright field magnified image of the strips. Our first goal is to observe the nanopatterned beam at the image plane. We will then investigate various crystal thickness and sample orientations to maximize the contrast in the pattern and explore tuning the period of the modulation through varying magnification.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPAB150

Export •

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

TUPAB139

Design of an X-Band Photoinjector Operating at 1 kHz

1659

W.S. Graves, A.C. Goodrich, M.R. Holl, N.J. O'Brien
Arizona State University, Tempe, USA
V. Bharadwaj, P. Borchard
Tibaray Inc., Stanford, USA
V.A. Dolgashev, E.A. Nanni
SLAC, Menlo Park, California, USA

A kHz repetition rate RF photoinjector with novel features has been designed for the ASU CXLS project. The photoinjector consists of a 9.3 GHz 4.5 cell standing-wave RF cavity that is constructed from 2 halves. The halves are brazed together, with the braze joint bisecting the irises and cells, greatly simplifying its construction. The cathode is brazed onto this assembly. RF power is coupled into the cavity through inline circular waveguide using a demountable TM01 mode launcher. The mode launcher feeds the power through 4 ports distributed azimuthally to eliminate both dipole and quadrupole field distortions. The brazed-in cathode and absence of complex power coupler result in a very inexpensive yet high performance device. The clean design allows the RF cavity to sit entirely within the solenoid assembly. The cathode gradient is 120 MV/m at 3 MW of input power. The cathode cell is just 0.17 RF wavelength so that laser arrival phase for peak acceleration is 70 degrees from zero crossing resulting in exit energy of 4 MeV. The photoinjector will operate with 1μs pulses at 1 kHz, dissipating 3 kW of heat. Details of the design are presented.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-TUPAB139

Export •

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

THPAB088

Comparison of Theory, Simulation, and Experiment for Dynamical Extinction of Relativistic Electron Beams Diffracted Through a Si Crystal Membrane

3924

SUSPSIK064

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

L.E. Malin, W.S. Graves, J. Spence, C. Zhang
Arizona State University, Tempe, USA
R.K. Li, C. Limborg, E.A. Nanni, X. Shen, S.P. Weathersby
SLAC, Menlo Park, California, USA

Diffraction in the transmission geometry through a single-crystal silicon slab is exploited to control the intensity of a relativistic electron beam. The choice of crystal thickness and incidence angle can extinguish or maximize the transmitted beam intensity via coherent multiple Bragg scattering; thus, the crystal acts as a dynamical beam stop through the Pendel'sung effect, a well-known phenomenon in X-ray and electron diffraction. In an initial experiment, we have measured the ability of this method to transmit or extinguish the primary beam and diffract into a single Bragg peak. Using lithographic etching of patterns in the crystal we intend to use this method to nanopattern an electron beam for production of coherent x-rays. We compare the experimental results with simulations using the multislice method to model the diffraction pattern from a perfect silicon crystal of uniform thickness, considering multiple scattering, crystallographic orientation, temperature effects, and partial coherence from the momentum spread of the beam. The simulations are compared to data collected at the ASTA UED facility at SLAC for a 340 nm thick Si(100) wafer with a beam energy of 2.35 MeV.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPAB088

Export •

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