IPAC2018 - List of Authors (Ha, G.)

Paper	Title	Page
TUPMK005	CSR Shielding Effect in Dogleg and EEX Beamlines	1498
	G. Ha, M.E. Conde, J.G. Power, E.E. Wisniewski ANL, Argonne, Illinois, USA
	Funding: Department of Energy, Office of HEP and BES under Contract No. DE-AC02-06CH11357. CSR shielding is a well-known CSR suppression scheme which works by cutting off the low frequency CSR radiation. Although the shielding scheme is well known, its effects on the beam has been rarely studied. We investigate the CSR effect on the beam emittance when passing through a dogleg and a double dogleg type EEX beamline. An experimental study is planned at the Argonne Wakefield Accelerator facility where we can generate a 0.1-100 nC electron beam with an energy of 50 MeV and have a double dogleg EEX beamline. Tunable shielding plates are installed at the dipole magnet chambers of the EEX beamline to vary the shielding condition. Transverse and longitudinal phase space measurement systems are prepared to characterize the beam-CSR interaction, and bolometer and interferometry are prepared to characterize CSR. We present simulation results and preliminary experimental results.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPMK005
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TUPML009	Design and Test Plan for a Prototype Corrugated Waveguide	1550
	G.J. Waldschmidt, D.S. Doran, G. Ha, R. Kustom, A. Nassiri, J.G. Power, A. Zholents ANL, Argonne, Illinois, USA A.E. Siy UW-Madison/PD, Madison, Wisconsin, USA
	A cylindrical, corrugated wakefield accelerating structure with a 1 mm radius bore is being designed to facilitate sub-terahertz Čerenkov radiation produced by an elec-tron bunch propagating along the waveguide. A 220 GHz axial mode for the wakefield is being considered. The waveguide is being optimized to maximize the trailing wakefield potential while maintaining a ratio of the trail-ing potential to the peak decelerating voltage in the bunch, or transformer ratio, of approximately 5 for the door step peak current distribution [1]. In order to evalu-ate the manufacturing tolerances and perform rf and electron beam testing of the waveguide, a 21 GHz proto-type waveguide structure will be built consisting of re-configurable parts allowing modelling of various fabrica-tion errors. Measurements with an electron beam will be performed at the Argonne Wakefield Accelerator (AWA) test facility. Analysis of the experimental layout has been performed.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPML009
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THPAK060	Transverse-to-Longitudinal Photocathode Distribution Imaging	3361
SUSPF084	use link to see paper's listing under its alternate paper code
	A. Halavanau, P. Piot Northern Illinois University, DeKalb, Illinois, USA W. Gai, G. Ha, J.G. Power, E.E. Wisniewski ANL, Argonne, Illinois, USA G. Ha PAL, Pohang, Republic of Korea P. Piot Fermilab, Batavia, Illinois, USA G. Qiang TUB, Beijing, People's Republic of China
	In this paper, we present a tunable picosecond-scale bunch train generation technique combining a microlens array (MLA) transverse laser shaper and a transverse-to-longitudinal emittance exchange (EEX) beamline. The modulated beamlet array is formed at the photocathode with the MLA setup. The resulting patterned electron beam is accelerated to 50 MeV and transported to the entrance of the EEX setup. A quadrupole channel is used to adjust the transverse spacing of the beamlet array upstream of the EEX, thereby enabling the generation of a bunch train with tunable separation downstream of the EEX beamline. Additionally, the MLA is mounted on a rotation stage which provides additional flexibility to produce high-frequency beam density modulation downstream of the EEX. Experimental results obtained at the Argonne Wakefield Accelerator (AWA) facility are presented and compared with numerical simulations.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK060
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TUPMF020	Demonstration of Fast, Single-shot Photocathode QE Mapping Method Using MLA Pattern Beam	1293
	E.E. Wisniewski, M.E. Conde, D.S. Doran, W. Gai, Q. Gao, W. Liu, J.G. Power, C. Whiteford ANL, Argonne, Illinois, USA Q. Gao TUB, Beijing, People's Republic of China G. Ha PAL, Pohang, Republic of Korea A. Halavanau, P. Piot Northern Illinois University, DeKalb, Illinois, USA P. Piot Fermilab, Batavia, Illinois, USA
	Funding: UChicago Argonne, LLC, Operator of Argonne National Laboratory ("Argonne"). Argonne, a U.S.A. Department of Energy Office of Science laboratory, is operated under Contract No. DE-AC02-06CH11357. Quantum efficiency (QE) is the chief figure of merit in the characterization of photocathodes. Semiconductor photocathodes, especially when used in high rep-rate photo-injectors, are known to show QE degradation over time and must be replaced. The total QE is the basic diagnostic which is used widely and is easy to obtain. However, a QE map indicating variations of QE across the cathode surface has greater utility. It can quickly diagnose problems of QE inhomogeneity. Most QE mapping techniques require hours to complete and are thus disruptive to a user facility schedule. A fast, single-shot method has been proposed (citation) using a micro-lens array (MLA) generated QE map. In this paper we report the implementation of the method at Argonne Wakefield Accelerator facility. A micro-lens array (MLA) is used to project an array of beamlets onto the photocathode. The resulting photoelectron beam in the form of an array of electron beamlets is imaged at a YAG screen. Four synchronized measurements are made and the results used to produce a QE map of the photocathode.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPMF020
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TUPMK006	Sub-fs Electron Bunch Generation Using Emittance Exchange Compressor	1501
	J.M. Seok, M. Chung UNIST, Ulsan, Republic of Korea M.E. Conde, J.G. Power ANL, Argonne, Illinois, USA G. Ha PAL, Pohang, Republic of Korea
	Sub-fs electron bunch has been pursued in the last decade using several different methods. These methods rely on one of the velocity difference or path length difference to compress a long bunch to sub-fs bunch. Here, we introduce a new method to generate the compression. Emittance Exchange (EEX) beamline makes transverse-to-longitudinal exchange of phase space. In this beamline, a transverse focusing at the upstream introduces a longitudinal compression at the downstream due to the exchange. Since this exchange scheme does not rely on the velocity or the path length differences, it does not require any longitudinal manipulation (e.g. chirp), and it could generate a short bunch with well-controlled nonlinear effects using nonlinear magnets. We present preliminary simulation results of EEX based bunch compression and sub-fs bunch generation.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPMK006
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THXGBE3	Proof of Principle Experiment for Single Shot Transverse Phase Space Measurement
	M.E. Conde, W. Liu, J.G. Power, E.E. Wisniewski ANL, Argonne, Illinois, USA G. Ha PAL, Pohang, Republic of Korea
	Funding: Department of Energy, Office of HEP and BES under Contract No. DE-AC02-06CH11357. We introduce a new method for single-shot transverse phase-space measurement. Existing phase space measurement methods are based on either average multiple shots of the full beam (e.g. scanning slit and quad scan tomography) or a single-shot sample of the beam (e.g. pepper pot and multi-slit). To achieve a single-shot measurement of the full beam, we project the beam's x-coordinate to the y-coordinate and its x'-coordinate to the x-coordinate using a skew quadrupole magnet followed by a normal quadrupole magnet. We present a theoretical description of this projection scheme and a proof-of-principle experimental demonstration done at the Argonne Wakefield Accelerator facility.
	Slides THXGBE3 [2.904 MB]
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Paper

Title

Page

CSR Shielding Effect in Dogleg and EEX Beamlines

1498

G. Ha, M.E. Conde, J.G. Power, E.E. Wisniewski
ANL, Argonne, Illinois, USA

Funding: Department of Energy, Office of HEP and BES under Contract No. DE-AC02-06CH11357.
CSR shielding is a well-known CSR suppression scheme which works by cutting off the low frequency CSR radiation. Although the shielding scheme is well known, its effects on the beam has been rarely studied. We investigate the CSR effect on the beam emittance when passing through a dogleg and a double dogleg type EEX beamline. An experimental study is planned at the Argonne Wakefield Accelerator facility where we can generate a 0.1-100 nC electron beam with an energy of 50 MeV and have a double dogleg EEX beamline. Tunable shielding plates are installed at the dipole magnet chambers of the EEX beamline to vary the shielding condition. Transverse and longitudinal phase space measurement systems are prepared to characterize the beam-CSR interaction, and bolometer and interferometry are prepared to characterize CSR. We present simulation results and preliminary experimental results.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPMK005

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

TUPML009

Design and Test Plan for a Prototype Corrugated Waveguide

1550

G.J. Waldschmidt, D.S. Doran, G. Ha, R. Kustom, A. Nassiri, J.G. Power, A. Zholents
ANL, Argonne, Illinois, USA
A.E. Siy
UW-Madison/PD, Madison, Wisconsin, USA

A cylindrical, corrugated wakefield accelerating structure with a 1 mm radius bore is being designed to facilitate sub-terahertz Čerenkov radiation produced by an elec-tron bunch propagating along the waveguide. A 220 GHz axial mode for the wakefield is being considered. The waveguide is being optimized to maximize the trailing wakefield potential while maintaining a ratio of the trail-ing potential to the peak decelerating voltage in the bunch, or transformer ratio, of approximately 5 for the door step peak current distribution [1]. In order to evalu-ate the manufacturing tolerances and perform rf and electron beam testing of the waveguide, a 21 GHz proto-type waveguide structure will be built consisting of re-configurable parts allowing modelling of various fabrica-tion errors. Measurements with an electron beam will be performed at the Argonne Wakefield Accelerator (AWA) test facility. Analysis of the experimental layout has been performed.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPML009

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

THPAK060

Transverse-to-Longitudinal Photocathode Distribution Imaging

3361

SUSPF084

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

A. Halavanau, P. Piot
Northern Illinois University, DeKalb, Illinois, USA
W. Gai, G. Ha, J.G. Power, E.E. Wisniewski
ANL, Argonne, Illinois, USA
G. Ha
PAL, Pohang, Republic of Korea
P. Piot
Fermilab, Batavia, Illinois, USA
G. Qiang
TUB, Beijing, People's Republic of China

In this paper, we present a tunable picosecond-scale bunch train generation technique combining a microlens array (MLA) transverse laser shaper and a transverse-to-longitudinal emittance exchange (EEX) beamline. The modulated beamlet array is formed at the photocathode with the MLA setup. The resulting patterned electron beam is accelerated to 50 MeV and transported to the entrance of the EEX setup. A quadrupole channel is used to adjust the transverse spacing of the beamlet array upstream of the EEX, thereby enabling the generation of a bunch train with tunable separation downstream of the EEX beamline. Additionally, the MLA is mounted on a rotation stage which provides additional flexibility to produce high-frequency beam density modulation downstream of the EEX. Experimental results obtained at the Argonne Wakefield Accelerator (AWA) facility are presented and compared with numerical simulations.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK060

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TUPMF020

Demonstration of Fast, Single-shot Photocathode QE Mapping Method Using MLA Pattern Beam

1293

E.E. Wisniewski, M.E. Conde, D.S. Doran, W. Gai, Q. Gao, W. Liu, J.G. Power, C. Whiteford
ANL, Argonne, Illinois, USA
Q. Gao
TUB, Beijing, People's Republic of China
G. Ha
PAL, Pohang, Republic of Korea
A. Halavanau, P. Piot
Northern Illinois University, DeKalb, Illinois, USA
P. Piot
Fermilab, Batavia, Illinois, USA

Funding: UChicago Argonne, LLC, Operator of Argonne National Laboratory ("Argonne"). Argonne, a U.S.A. Department of Energy Office of Science laboratory, is operated under Contract No. DE-AC02-06CH11357.
Quantum efficiency (QE) is the chief figure of merit in the characterization of photocathodes. Semiconductor photocathodes, especially when used in high rep-rate photo-injectors, are known to show QE degradation over time and must be replaced. The total QE is the basic diagnostic which is used widely and is easy to obtain. However, a QE map indicating variations of QE across the cathode surface has greater utility. It can quickly diagnose problems of QE inhomogeneity. Most QE mapping techniques require hours to complete and are thus disruptive to a user facility schedule. A fast, single-shot method has been proposed (citation) using a micro-lens array (MLA) generated QE map. In this paper we report the implementation of the method at Argonne Wakefield Accelerator facility. A micro-lens array (MLA) is used to project an array of beamlets onto the photocathode. The resulting photoelectron beam in the form of an array of electron beamlets is imaged at a YAG screen. Four synchronized measurements are made and the results used to produce a QE map of the photocathode.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPMF020

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TUPMK006

Sub-fs Electron Bunch Generation Using Emittance Exchange Compressor

1501

J.M. Seok, M. Chung
UNIST, Ulsan, Republic of Korea
M.E. Conde, J.G. Power
ANL, Argonne, Illinois, USA
G. Ha
PAL, Pohang, Republic of Korea

Sub-fs electron bunch has been pursued in the last decade using several different methods. These methods rely on one of the velocity difference or path length difference to compress a long bunch to sub-fs bunch. Here, we introduce a new method to generate the compression. Emittance Exchange (EEX) beamline makes transverse-to-longitudinal exchange of phase space. In this beamline, a transverse focusing at the upstream introduces a longitudinal compression at the downstream due to the exchange. Since this exchange scheme does not rely on the velocity or the path length differences, it does not require any longitudinal manipulation (e.g. chirp), and it could generate a short bunch with well-controlled nonlinear effects using nonlinear magnets. We present preliminary simulation results of EEX based bunch compression and sub-fs bunch generation.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPMK006

Export •

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

THXGBE3

Proof of Principle Experiment for Single Shot Transverse Phase Space Measurement

M.E. Conde, W. Liu, J.G. Power, E.E. Wisniewski
ANL, Argonne, Illinois, USA
G. Ha
PAL, Pohang, Republic of Korea

Funding: Department of Energy, Office of HEP and BES under Contract No. DE-AC02-06CH11357.
We introduce a new method for single-shot transverse phase-space measurement. Existing phase space measurement methods are based on either average multiple shots of the full beam (e.g. scanning slit and quad scan tomography) or a single-shot sample of the beam (e.g. pepper pot and multi-slit). To achieve a single-shot measurement of the full beam, we project the beam's x-coordinate to the y-coordinate and its x'-coordinate to the x-coordinate using a skew quadrupole magnet followed by a normal quadrupole magnet. We present a theoretical description of this projection scheme and a proof-of-principle experimental demonstration done at the Argonne Wakefield Accelerator facility.

Slides THXGBE3 [2.904 MB]

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