IPAC2018 - List of Authors (Fleming, R.L.)

Paper	Title	Page
MOPML052	The Path to Compact, Efficient Solid-State Transistor-Driven Accelerators	520
	D.C. Nguyen, C.E. Buechler, G.E. Dale, R.L. Fleming, M.A. Holloway, J.W. Lewellen, D. Patrick LANL, Los Alamos, New Mexico, USA V.A. Dolgashev, E.N. Jongewaard, E.A. Nanni, J. Neilson, A.V. Sy, S.G. Tantawi SLAC, Menlo Park, California, USA
	Funding: Research presented in this work is supported by (LANL) Laboratory Directed Research and Development 20170521ER and by (SLAC) Department of Energy contract DE-AC02-76SF00515. Small, lightweight, few-MeV electron accelerators that can operate with low-voltage power sources, e.g., solid-state transistors running on 50 VDC, instead of high-voltage klystrons, will provide a new tool to enhance existing applications of accelerators as well as to initiate new ones. Recent advances in gallium nitride (GaN) semiconductor technologies * have resulted in a new class of high-power RF solid-state devices called high-electron mobility transistors (HEMTs). These HEMTs are capable of generating a few hundred watts at S-, C- and X-bands at 10% duty factor. We have characterized a number of GaN HEMTs and verified they have suitable RF characteristics to power accelerator cavities *. We have measured energy gain as a function of RF power in a single low-beta C-band cavity. The HEMT powered RF accelerators will be compact and efficient, and they can operate off the low-voltage DC power buses or batteries. These all-solid-state accelerators are also more robust, less likely to fail, and are easier to maintain and operate. In this poster, we present the design of a low-beta, 5.1-GHz cavity and beam dynamics simulations showing continuous energy gain in a ten-cavity C-band prototype. See for example, http://www.wolfspeed.com/downloads/dl/file/id/463/product/174/cghv59350.pdf ** J.W. Lewellen et al., Proceedings of LINAC2016, Paper MO3A03
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPML052
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WEPAL045	An Electrostatic Fixed-Slit Emittance Measurement System	2274
	J.W. Lewellen, H.L. Andrews, R.L. Fleming, K.E. Nichols, E.I. Simakov LANL, Los Alamos, New Mexico, USA
	Funding: Los Alamos National Laboratory LDRD Program The emittance of a field emission cathode can be difficult to measure close to the emitter, due to the high average current density of the beam and the potential for desorbed material from an imaging screen to contaminate the cathode. We present the design for a dual fixed-slit emittance measurement system for a field emitter cathode, implemented using electrostatic deflecting plates. Results from fabrication and initial testing will be presented.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPAL045
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THPAL024	A Simple Variable Focus Lens for Field Emitter Cathodes	3677
	R.L. Fleming, H.L. Andrews, K. Bishofberger, D. Kim, J.W. Lewellen, K.E. Nichols, D.Y. Shchegolkov, E.I. Simakov LANL, Los Alamos, New Mexico, USA
	Funding: Los Alamos National Laboratory LDRD Program We present the design for a simple, variable-focus solenoidal lens with integrated emittance filtering. The design was developed as a first-iteration injection optics solution for transport of a beam from a field-emitter cathode into a dielectric laser accelerator structure. The design is easy to fabricate and, while based on permanent magnets, can readily be modified to allow for remote control of the focal length. The emittance is controlled via selection of collimating irises. The focal length can be changed by altering the spacing between two permanent ring magnets. Results from fabrication and initial testing will be presented.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAL024
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THPML007	An Investigation of Electron Beam Divergence from a Single DFEA Emitter Tip	4662
	H.L. Andrews, B.K. Choi, R.L. Fleming, D. Kim, J.W. Lewellen, K.E. Nichols, D.Y. Shchegolkov, E.I. Simakov LANL, Los Alamos, New Mexico, USA
	Funding: We gratefully acknowledge the support of the U.S. Department of Energy through the LANL/LDRD Program for this work. Diamond Field-Emitter Array (DFEA) cathodes are arrays of micron-scale diamond pyramids with nanometer-scale tips. DFEAs can produce high emission currents with small emittance and energy spread. At LANL, we have an ongoing program to test DFEA cathodes for the purpose of using them to generate high-current, low-emittance electron beams for dielectric laser accelerators. We have recently upgraded our cathode test chamber to use a mesh anode in place of a solid luminescent anode. In addition to allowing for downstream beam transport, this arrangement may eliminate earlier problems with reduced cathode performance due to ion back-bombardment. We are measuring divergence of the electron beam past the mesh in an effort to characterize the inherent beam divergence off the diamond tip and divergence contribution from the mesh. We will compare these observations with theoretical and modeled values.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPML007
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Paper

Title

Page

The Path to Compact, Efficient Solid-State Transistor-Driven Accelerators

520

D.C. Nguyen, C.E. Buechler, G.E. Dale, R.L. Fleming, M.A. Holloway, J.W. Lewellen, D. Patrick
LANL, Los Alamos, New Mexico, USA
V.A. Dolgashev, E.N. Jongewaard, E.A. Nanni, J. Neilson, A.V. Sy, S.G. Tantawi
SLAC, Menlo Park, California, USA

Funding: Research presented in this work is supported by (LANL) Laboratory Directed Research and Development 20170521ER and by (SLAC) Department of Energy contract DE-AC02-76SF00515.
Small, lightweight, few-MeV electron accelerators that can operate with low-voltage power sources, e.g., solid-state transistors running on 50 VDC, instead of high-voltage klystrons, will provide a new tool to enhance existing applications of accelerators as well as to initiate new ones. Recent advances in gallium nitride (GaN) semiconductor technologies * have resulted in a new class of high-power RF solid-state devices called high-electron mobility transistors (HEMTs). These HEMTs are capable of generating a few hundred watts at S-, C- and X-bands at 10% duty factor. We have characterized a number of GaN HEMTs and verified they have suitable RF characteristics to power accelerator cavities **. We have measured energy gain as a function of RF power in a single low-beta C-band cavity. The HEMT powered RF accelerators will be compact and efficient, and they can operate off the low-voltage DC power buses or batteries. These all-solid-state accelerators are also more robust, less likely to fail, and are easier to maintain and operate. In this poster, we present the design of a low-beta, 5.1-GHz cavity and beam dynamics simulations showing continuous energy gain in a ten-cavity C-band prototype.
* See for example, http://www.wolfspeed.com/downloads/dl/file/id/463/product/174/cghv59350.pdf
** J.W. Lewellen et al., Proceedings of LINAC2016, Paper MO3A03

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPML052

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WEPAL045

An Electrostatic Fixed-Slit Emittance Measurement System

2274

J.W. Lewellen, H.L. Andrews, R.L. Fleming, K.E. Nichols, E.I. Simakov
LANL, Los Alamos, New Mexico, USA

Funding: Los Alamos National Laboratory LDRD Program
The emittance of a field emission cathode can be difficult to measure close to the emitter, due to the high average current density of the beam and the potential for desorbed material from an imaging screen to contaminate the cathode. We present the design for a dual fixed-slit emittance measurement system for a field emitter cathode, implemented using electrostatic deflecting plates. Results from fabrication and initial testing will be presented.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPAL045

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

THPAL024

A Simple Variable Focus Lens for Field Emitter Cathodes

3677

R.L. Fleming, H.L. Andrews, K. Bishofberger, D. Kim, J.W. Lewellen, K.E. Nichols, D.Y. Shchegolkov, E.I. Simakov
LANL, Los Alamos, New Mexico, USA

Funding: Los Alamos National Laboratory LDRD Program
We present the design for a simple, variable-focus solenoidal lens with integrated emittance filtering. The design was developed as a first-iteration injection optics solution for transport of a beam from a field-emitter cathode into a dielectric laser accelerator structure. The design is easy to fabricate and, while based on permanent magnets, can readily be modified to allow for remote control of the focal length. The emittance is controlled via selection of collimating irises. The focal length can be changed by altering the spacing between two permanent ring magnets. Results from fabrication and initial testing will be presented.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAL024

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THPML007

An Investigation of Electron Beam Divergence from a Single DFEA Emitter Tip

4662

H.L. Andrews, B.K. Choi, R.L. Fleming, D. Kim, J.W. Lewellen, K.E. Nichols, D.Y. Shchegolkov, E.I. Simakov
LANL, Los Alamos, New Mexico, USA

Funding: We gratefully acknowledge the support of the U.S. Department of Energy through the LANL/LDRD Program for this work.
Diamond Field-Emitter Array (DFEA) cathodes are arrays of micron-scale diamond pyramids with nanometer-scale tips. DFEAs can produce high emission currents with small emittance and energy spread. At LANL, we have an ongoing program to test DFEA cathodes for the purpose of using them to generate high-current, low-emittance electron beams for dielectric laser accelerators. We have recently upgraded our cathode test chamber to use a mesh anode in place of a solid luminescent anode. In addition to allowing for downstream beam transport, this arrangement may eliminate earlier problems with reduced cathode performance due to ion back-bombardment. We are measuring divergence of the electron beam past the mesh in an effort to characterize the inherent beam divergence off the diamond tip and divergence contribution from the mesh. We will compare these observations with theoretical and modeled values.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPML007

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