FEL2017 - List of Authors (Simakov, E.I.)

Paper	Title	Page
TUP050	Beam Driven Acceleration and RF Breakdown in Photonic Band Gap Travelling Wave Accelerator Structure	333
	J. Upadhyay, E.I. Simakov LANL, Los Alamos, New Mexico, USA
	We report the results of an experiment to demonstrate excitation of wakefields and wakefield acceleration in a photonic band gap (PBG) accelerating structure. The experiment was conducted at the Argonne Wakefield Accelerator (AWA) facility. For modern X-ray free electron lasers (FELs), preservation of the electron beam quality during the beam acceleration is of crucial importance. Therefore, new accelerating structures must be designed with careful attention paid to the suppression of wakefields. PBG structures are widely studied due to their ability to exclude higher order modes. A 16-cell travelling-wave normal conducting PBG structure operating at 11.700 GHz is installed at the AWA beam line. We passed a high-charge single bunch or multiple bunch train through the structure that generated wakefields and evaluated the effect of these wakefields on a low-charge witness beam. We also passed high-charge multiple bunch trains through the structure that generated up to 100 MV/m accelerating gradient and studied the RF breakdown.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-TUP050
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WEP015	Current Experimental Work with Diamond Field-Emitter Array Cathodes	450
	H.L. Andrews, R.L. Fleming, J.W. Lewellen, K.E. Nichols, D.Y. Shchegolkov, E.I. Simakov LANL, Los Alamos, New Mexico, USA B.K. Choi Vanderbilt University, Nashville, 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, thereby providing high emission currents with small emittance and energy spread. To date they have been demonstrated in a close-diode configuration, spaced only a few hundred microns from a solid anode, and have shown very promising results in terms of emittance, energy spread, and per-tip emission currents. We present recent results investigating DFEA performance in a large-gap configuration, such that the cathodes are a few millimeters from a solid anode, and show that performance is the same or better as the close-diode geometry previously studied. However, array performance is still limited by anode damage. We are redesigning our cathode test stand to overcome the inherent limitations of a solid anode, allow for transport of the emitted beam, and further explore real-world DFEA performance.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-WEP015
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WEP016	Modeling of Diamond Field-Emitter Arrays for High-Brightness Photocathode Applications	454
	C. Huang, H.L. Andrews, B.K. Choi, R.L. Fleming, T.J. Kwan, J.W. Lewellen, D.C. Nguyen, K.E. Nichols, V.N. Pavlenko, A. Piryatinski, D.Y. Shchegolkov, E.I. Simakov LANL, Los Alamos, New Mexico, USA
	Funding: Work performed under the auspices of the U.S. DOE by the LANS, LLC, Los Alamos National Laboratory (LANL) under Contract No. DE-AC52-06NA25396. Work supported by the LDRD program at LANL. Dielectric Laser Accelerator (DLA) is capable of generating high output power for an X-ray free-electron laser (FEL), while having a size 1-2 orders of magnitude smaller than existing Radio-Frequency (RF) accelerators. Single Diamond Field-Emitter (DFE) or array of such emitters (DFEA) can be employed as high-current ultra-low-emittance photocathodes for compact DLAs. We are developing a first principle semi-classical Monte-Carlo (MC) emission model for DFEAs that includes the effects of carriers' photoexcitation, their transport to the emitter surface, and the tunnelling through the surface. The electronic structure size quantization affecting the transport and tunnelling processes within the sharp diamond tips is also accounted for. These aspects of our model and their implementation and validation, as well as macroscopic electromagnetic beam simulation of DFE are discussed.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-WEP016
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Paper

Title

Page

Beam Driven Acceleration and RF Breakdown in Photonic Band Gap Travelling Wave Accelerator Structure

333

J. Upadhyay, E.I. Simakov
LANL, Los Alamos, New Mexico, USA

We report the results of an experiment to demonstrate excitation of wakefields and wakefield acceleration in a photonic band gap (PBG) accelerating structure. The experiment was conducted at the Argonne Wakefield Accelerator (AWA) facility. For modern X-ray free electron lasers (FELs), preservation of the electron beam quality during the beam acceleration is of crucial importance. Therefore, new accelerating structures must be designed with careful attention paid to the suppression of wakefields. PBG structures are widely studied due to their ability to exclude higher order modes. A 16-cell travelling-wave normal conducting PBG structure operating at 11.700 GHz is installed at the AWA beam line. We passed a high-charge single bunch or multiple bunch train through the structure that generated wakefields and evaluated the effect of these wakefields on a low-charge witness beam. We also passed high-charge multiple bunch trains through the structure that generated up to 100 MV/m accelerating gradient and studied the RF breakdown.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-TUP050

Export •

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

WEP015

Current Experimental Work with Diamond Field-Emitter Array Cathodes

450

H.L. Andrews, R.L. Fleming, J.W. Lewellen, K.E. Nichols, D.Y. Shchegolkov, E.I. Simakov
LANL, Los Alamos, New Mexico, USA
B.K. Choi
Vanderbilt University, Nashville, 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, thereby providing high emission currents with small emittance and energy spread. To date they have been demonstrated in a close-diode configuration, spaced only a few hundred microns from a solid anode, and have shown very promising results in terms of emittance, energy spread, and per-tip emission currents. We present recent results investigating DFEA performance in a large-gap configuration, such that the cathodes are a few millimeters from a solid anode, and show that performance is the same or better as the close-diode geometry previously studied. However, array performance is still limited by anode damage. We are redesigning our cathode test stand to overcome the inherent limitations of a solid anode, allow for transport of the emitted beam, and further explore real-world DFEA performance.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-WEP015

Export •

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

WEP016

Modeling of Diamond Field-Emitter Arrays for High-Brightness Photocathode Applications

454

C. Huang, H.L. Andrews, B.K. Choi, R.L. Fleming, T.J. Kwan, J.W. Lewellen, D.C. Nguyen, K.E. Nichols, V.N. Pavlenko, A. Piryatinski, D.Y. Shchegolkov, E.I. Simakov
LANL, Los Alamos, New Mexico, USA

Funding: Work performed under the auspices of the U.S. DOE by the LANS, LLC, Los Alamos National Laboratory (LANL) under Contract No. DE-AC52-06NA25396. Work supported by the LDRD program at LANL.
Dielectric Laser Accelerator (DLA) is capable of generating high output power for an X-ray free-electron laser (FEL), while having a size 1-2 orders of magnitude smaller than existing Radio-Frequency (RF) accelerators. Single Diamond Field-Emitter (DFE) or array of such emitters (DFEA) can be employed as high-current ultra-low-emittance photocathodes for compact DLAs. We are developing a first principle semi-classical Monte-Carlo (MC) emission model for DFEAs that includes the effects of carriers' photoexcitation, their transport to the emitter surface, and the tunnelling through the surface. The electronic structure size quantization affecting the transport and tunnelling processes within the sharp diamond tips is also accounted for. These aspects of our model and their implementation and validation, as well as macroscopic electromagnetic beam simulation of DFE are discussed.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-WEP016

Export •

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