IPAC2017 - List of Authors (Limborg, C.)

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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TUPAB129	Optimization of Beam Dynamics for an S-Band Ultra-High Gradient Photoinjector	1626
	A.D. Cahill, A. Fukasawa, J.B. Rosenzweig UCLA, Los Angeles, California, USA C. Limborg, W. Qin SLAC, Menlo Park, California, USA
	Funding: Work Supported by DOE/SU Contract DE-AC02-76-SF00515, US NSF Award PHY-1549132, the Center for Bright Beams, and DOE SCGSR Fellowship. Travel to IPAC'17 supported by the Div. of Phys. of the US NSF (Accel. Sci. Prog.) and the Div. of Beam Phys. of the APS New electron sources with improved brightness are desired to enhance the capabilities of FELs, making them more compact and fully coherent. Improvements in electron source brightness can be achieved by increasing electric fields on the cathode of photo-emitted electron guns. Recent developments in pulsed RF accelerator structures show that very high gradient fields can be sustained with low breakdown rates by operating at cryo-temperatures, which when applied to photoguns will lead to a large increase in the electron beam brightness. In particular, our simulations show that when operating with a peak gradient field of 240 MV/m on the cathode of an S-band, electron beam brightness of 80~nC/(mm· mrad)²/mm can be achieved with 100~pC bunches. In this paper, we present the design and optimization of an 1.x cell S-Band RF photoinjector, where the x varies from 4-6. The optimization in brightness has been obtained by using a multi-objective genetic algorithm on the solutions calculated with the ASTRA code. We calculate the optimum length of the rf gun, position of accelerating structure, and laser pulse dimensions for a variety of charges.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-TUPAB129
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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

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

TUPAB129

Optimization of Beam Dynamics for an S-Band Ultra-High Gradient Photoinjector

1626

A.D. Cahill, A. Fukasawa, J.B. Rosenzweig
UCLA, Los Angeles, California, USA
C. Limborg, W. Qin
SLAC, Menlo Park, California, USA

Funding: Work Supported by DOE/SU Contract DE-AC02-76-SF00515, US NSF Award PHY-1549132, the Center for Bright Beams, and DOE SCGSR Fellowship. Travel to IPAC'17 supported by the Div. of Phys. of the US NSF (Accel. Sci. Prog.) and the Div. of Beam Phys. of the APS
New electron sources with improved brightness are desired to enhance the capabilities of FELs, making them more compact and fully coherent. Improvements in electron source brightness can be achieved by increasing electric fields on the cathode of photo-emitted electron guns. Recent developments in pulsed RF accelerator structures show that very high gradient fields can be sustained with low breakdown rates by operating at cryo-temperatures, which when applied to photoguns will lead to a large increase in the electron beam brightness. In particular, our simulations show that when operating with a peak gradient field of 240 MV/m on the cathode of an S-band, electron beam brightness of 80~nC/(mm· mrad)²/mm can be achieved with 100~pC bunches. In this paper, we present the design and optimization of an 1.x cell S-Band RF photoinjector, where the x varies from 4-6. The optimization in brightness has been obtained by using a multi-objective genetic algorithm on the solutions calculated with the ASTRA code. We calculate the optimum length of the rf gun, position of accelerating structure, and laser pulse dimensions for a variety of charges.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-TUPAB129

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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

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