IPAC2016 - List of Authors (Ha, G.)

Paper	Title	Page
TUOBB01	Demonstration of Current Profile Shaping using Double Dog-Leg Emittance Exchange Beam Line at Argonne Wakefield Accelerator	1065
	G. Ha, M.-H. Cho, W. Namkung POSTECH, Pohang, Kyungbuk, Republic of Korea M.E. Conde, D.S. Doran, W. Gai, G. Ha, K.-J. Kim, W. Liu, J.G. Power, Y.-E. Sun, C. Whiteford, E.E. Wisniewski, A. Zholents ANL, Argonne, Illinois, USA C.-J. Jing Euclid TechLabs, LLC, Solon, Ohio, USA P. Piot Fermilab, Batavia, Illinois, USA
	Emittance exchange (EEX) based longitudinal current profile shaping is the one of the promising current profile shaping technique. This method can generate high quality arbitrary current profiles under the ideal conditions. The double dog-leg EEX beam line was recently installed at the Argonne Wakefield Accelerator (AWA) to explore the shaping capability and confirm the quality of this method. To demonstrate the arbitrary current profile generation, several different transverse masks are applied to generate different final current profiles. The phase space slopes and the charge of incoming beam are varied to observe and suppress the aberrations on the ideal profile. We present current profile shaping results, aberrations on the shaped profile, and its suppression.
	Slides TUOBB01 [5.032 MB]
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUOBB01
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TUPMY031	Estimation and Suppression of Aberrations in Emittance Exchange based Current Profile Shaping	1615
	G. Ha, M.-H. Cho, W. Namkung POSTECH, Pohang, Kyungbuk, Republic of Korea W. Gai, G. Ha, K.-J. Kim, J.G. Power ANL, Argonne, Illinois, USA
	The longitudinal current profile manipulation has been explored for many applications including THz radiation, FEL and advanced acceleration schemes. Especially, collinear dielectric wakefield accelerations require a microbunch shaping for a high transformer ratio. We have studied aberrations from the emittance exchange based current profile shaping to preserve the high transformer ratio. All second order aberration terms in the double dog-leg emittance exchange beam line are discovered. Aberration patterns from each aberration sources like second order terms, space-charge, and CSR and their effect on the transformer ratio are estimated analytically. These aberration sources and corresponding patterns are confirmed using a particle tracking code GPT. Simple methods to suppress each aberration will be presented too. All calculation in this work is done with a double dog-leg emittance exchange beam line.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPMY031
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TUPMY036	Drive Generation and Propagation Studies for the Two Beam Acceleration Experiment at the Argonne Wakefield Accelerator	1629
SUPSS029	use link to see paper's listing under its alternate paper code
	N.R. Neveu, M.E. Conde, D.S. Doran, W. Gai, G. Ha, C.-J. Jing, W. Liu, J.G. Power, D. Wang, C. Whiteford, E.E. Wisniewski ANL, Argonne, Illinois, USA S.P. Antipov, C.-J. Jing Euclid TechLabs, LLC, Solon, Ohio, USA G. Ha POSTECH, Pohang, Kyungbuk, Republic of Korea N.R. Neveu IIT, Chicago, Illinois, USA D. Wang TUB, Beijing, People's Republic of China
	Funding: Work supported by by the U.S. Department of Energy under contract No. DE-AC02-06CH11357. Simplified staging in a two beam accelerator (TBA) has been accomplished at the Argonne Wakefield Accelerator (AWA) facility. This layout consists of a drive beamline and witness beamline operating synchronously. The drive photoinjector linac produces a 70 MeV drive bunch train of eight electron bunches (charge per bunch between 5-40 nC) that pass through decelerating structures in each TBA stage. The witness linac produces an 8 MeV witness bunch that passes through the accelerating structures in each TBA stage. Recent effort has been focused on improving the uniformity of the UV laser pulses that generate the bunch trains. Current work at the AWA is focused on the transition from simplified staging to full staging. A kicker will be designed and installed to direct bunch trains to one TBA stage only. Preliminary calculations and simulation results are presented.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPMY036
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TUPOW015	Experiment of High Resolution Field Emission Imaging in an rf Photocathode Gun	1772
	J.H. Shao, H.B. Chen, J. Shi, X.W. Wu TUB, Beijing, People's Republic of China S.P. Antipov, S.V. Baryshev, C.-J. Jing Euclid TechLabs, LLC, Solon, Ohio, USA M.E. Conde, W. Gai, G. Ha, E.E. Wisniewski ANL, Argonne, Illinois, USA F.Y. Wang SLAC, Menlo Park, California, USA
	The first in situ high resolution field emission (FE) imaging experiment has been carried out on an L-band photocathode gun test stand at Argonne Wakefield Accelerator facility (AWA). Separated strong emitters have been observed to dominate the field emission. Field enhancement factor, beta, of small regions on the cathode has been measured with the imaging system. It is shown that most strong emitters overlaps with the high beta regions. The post surface examinations reveal the origins of ~75% strong emitters overlap with the spots where rf breakdown have occurred. Detailed results are presented in this paper.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPOW015
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WEPOY025	High Power RF Generation From a W-Band Corrugated Structure Excited by a Train of Electron Bunches	3040
SUPSS062	use link to see paper's listing under its alternate paper code
	D. Wang, C.-X. Tang TUB, Beijing, People's Republic of China S.P. Antipov, C.-J. Jing, J.Q. Qiu Euclid TechLabs, LLC, Solon, Ohio, USA M.E. Conde, D.S. Doran, W. Gai, G. Ha, G. Ha, W. Liu, J.G. Power, E.E. Wisniewski ANL, Argonne, Illinois, USA V.A. Dolgashev SLAC, Menlo Park, California, USA
	We report on the generation of multi-megawatt peak RF power at 91textGHz, using an ultrarelativistic electron bunch train to excite electromagnetic fields in a high-impedance metallic corrugated structure. This device can be used as a power source for high gradient acceleration of electrons. To achieve precise control of the wakefield phase, a long range wakefield interferometry method was developed in which the RF energy due to the interference of the wakefields from two bunches was measured as a function of the bunch separation.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPOY025
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WEPOY026	Simulation and Measurement of the Beam Breakup Instability in a W-band Corrugated Structure	3044
	D. Wang, C.-X. Tang TUB, Beijing, People's Republic of China S.P. Antipov, C.-J. Jing, J.Q. Qiu Euclid TechLabs, LLC, Solon, Ohio, USA M.E. Conde, D.S. Doran, W. Gai, G. Ha, W. Liu, J.G. Power, E.E. Wisniewski ANL, Argonne, Illinois, USA
	The corrugated wakefield structure has wide application in electron beam energy manipulation and high frequency RF radiation generation. The transverse wakefield which cause beam breakup (BBU) instability is excited when the drive beam is not perfectly centered through the structure. Here we report on the numerical and experimental investigation of the BBU effect in a W-band corrugated structure, for both cases of short range wakefield and long range wakefield. In the numerical part we develop a point to point (P2P) code that allows rapid and efficiency simulations of the beam dynamics effect by wakefield, which is based on the the particle-wake function coupled dynamics equation of motion. And the experimental measurements of BBU effect are found to be in good agreement with the simulations.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPOY026
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THPOW021	Generation of Homogeneous and Patterned Electron Beams using a Microlens Array Laser-Shaping Technique	3983
SUPSS020	use link to see paper's listing under its alternate paper code
	A. Halavanau, P. Piot Northern Illinois University, DeKalb, Illinois, USA D.R. Edstrom, P. Piot, J. Ruan, J.K. Santucci Fermilab, Batavia, Illinois, USA W. Gai, G. Ha, J.G. Power, E.E. Wisniewski ANL, Argonne, Illinois, USA G. Ha POSTECH, Pohang, Kyungbuk, Republic of Korea G. Qiang TUB, Beijing, People's Republic of China
	Funding: Northern Illinois University - US DOE contract No. DE-SC0011831. Fermilab - US DOE contract No. DE-AC02-07CH11359. The Argonne wakefield facility - US DOE contract No. DE-AC02-06CH11357. In photocathodes the achievable electron-beam parameters are controlled by the laser used to trigger the photoemission process. Non-ideal laser distribution hampers the final beam quality. Laser inhomogeneities, for instance, can be "amplified" by space-charge force and result in fragmented electron beams. To overcome this limitation laser shaping methods are routinely employed. In the present paper we demonstrate the use of simple microlens arrays to dramatically improve the transverse uniformity. We also show that this arrangement can be used to produce transversely-patterned electron beams. Our experiments are carried out at the Argonne Wakefield Accelerator facility.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPOW021
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

Paper

Title

Page

Demonstration of Current Profile Shaping using Double Dog-Leg Emittance Exchange Beam Line at Argonne Wakefield Accelerator

1065

G. Ha, M.-H. Cho, W. Namkung
POSTECH, Pohang, Kyungbuk, Republic of Korea
M.E. Conde, D.S. Doran, W. Gai, G. Ha, K.-J. Kim, W. Liu, J.G. Power, Y.-E. Sun, C. Whiteford, E.E. Wisniewski, A. Zholents
ANL, Argonne, Illinois, USA
C.-J. Jing
Euclid TechLabs, LLC, Solon, Ohio, USA
P. Piot
Fermilab, Batavia, Illinois, USA

Emittance exchange (EEX) based longitudinal current profile shaping is the one of the promising current profile shaping technique. This method can generate high quality arbitrary current profiles under the ideal conditions. The double dog-leg EEX beam line was recently installed at the Argonne Wakefield Accelerator (AWA) to explore the shaping capability and confirm the quality of this method. To demonstrate the arbitrary current profile generation, several different transverse masks are applied to generate different final current profiles. The phase space slopes and the charge of incoming beam are varied to observe and suppress the aberrations on the ideal profile. We present current profile shaping results, aberrations on the shaped profile, and its suppression.

Slides TUOBB01 [5.032 MB]

DOI •

reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUOBB01

Export •

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

TUPMY031

Estimation and Suppression of Aberrations in Emittance Exchange based Current Profile Shaping

1615

G. Ha, M.-H. Cho, W. Namkung
POSTECH, Pohang, Kyungbuk, Republic of Korea
W. Gai, G. Ha, K.-J. Kim, J.G. Power
ANL, Argonne, Illinois, USA

The longitudinal current profile manipulation has been explored for many applications including THz radiation, FEL and advanced acceleration schemes. Especially, collinear dielectric wakefield accelerations require a microbunch shaping for a high transformer ratio. We have studied aberrations from the emittance exchange based current profile shaping to preserve the high transformer ratio. All second order aberration terms in the double dog-leg emittance exchange beam line are discovered. Aberration patterns from each aberration sources like second order terms, space-charge, and CSR and their effect on the transformer ratio are estimated analytically. These aberration sources and corresponding patterns are confirmed using a particle tracking code GPT. Simple methods to suppress each aberration will be presented too. All calculation in this work is done with a double dog-leg emittance exchange beam line.

DOI •

reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPMY031

Export •

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

TUPMY036

Drive Generation and Propagation Studies for the Two Beam Acceleration Experiment at the Argonne Wakefield Accelerator

1629

SUPSS029

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

N.R. Neveu, M.E. Conde, D.S. Doran, W. Gai, G. Ha, C.-J. Jing, W. Liu, J.G. Power, D. Wang, C. Whiteford, E.E. Wisniewski
ANL, Argonne, Illinois, USA
S.P. Antipov, C.-J. Jing
Euclid TechLabs, LLC, Solon, Ohio, USA
G. Ha
POSTECH, Pohang, Kyungbuk, Republic of Korea
N.R. Neveu
IIT, Chicago, Illinois, USA
D. Wang
TUB, Beijing, People's Republic of China

Funding: Work supported by by the U.S. Department of Energy under contract No. DE-AC02-06CH11357.
Simplified staging in a two beam accelerator (TBA) has been accomplished at the Argonne Wakefield Accelerator (AWA) facility. This layout consists of a drive beamline and witness beamline operating synchronously. The drive photoinjector linac produces a 70 MeV drive bunch train of eight electron bunches (charge per bunch between 5-40 nC) that pass through decelerating structures in each TBA stage. The witness linac produces an 8 MeV witness bunch that passes through the accelerating structures in each TBA stage. Recent effort has been focused on improving the uniformity of the UV laser pulses that generate the bunch trains. Current work at the AWA is focused on the transition from simplified staging to full staging. A kicker will be designed and installed to direct bunch trains to one TBA stage only. Preliminary calculations and simulation results are presented.

DOI •

reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPMY036

Export •

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

TUPOW015

Experiment of High Resolution Field Emission Imaging in an rf Photocathode Gun

1772

J.H. Shao, H.B. Chen, J. Shi, X.W. Wu
TUB, Beijing, People's Republic of China
S.P. Antipov, S.V. Baryshev, C.-J. Jing
Euclid TechLabs, LLC, Solon, Ohio, USA
M.E. Conde, W. Gai, G. Ha, E.E. Wisniewski
ANL, Argonne, Illinois, USA
F.Y. Wang
SLAC, Menlo Park, California, USA

The first in situ high resolution field emission (FE) imaging experiment has been carried out on an L-band photocathode gun test stand at Argonne Wakefield Accelerator facility (AWA). Separated strong emitters have been observed to dominate the field emission. Field enhancement factor, beta, of small regions on the cathode has been measured with the imaging system. It is shown that most strong emitters overlaps with the high beta regions. The post surface examinations reveal the origins of ~75% strong emitters overlap with the spots where rf breakdown have occurred. Detailed results are presented in this paper.

DOI •

reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPOW015

Export •

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

WEPOY025

High Power RF Generation From a W-Band Corrugated Structure Excited by a Train of Electron Bunches

3040

SUPSS062

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

D. Wang, C.-X. Tang
TUB, Beijing, People's Republic of China
S.P. Antipov, C.-J. Jing, J.Q. Qiu
Euclid TechLabs, LLC, Solon, Ohio, USA
M.E. Conde, D.S. Doran, W. Gai, G. Ha, G. Ha, W. Liu, J.G. Power, E.E. Wisniewski
ANL, Argonne, Illinois, USA
V.A. Dolgashev
SLAC, Menlo Park, California, USA

We report on the generation of multi-megawatt peak RF power at 91textGHz, using an ultrarelativistic electron bunch train to excite electromagnetic fields in a high-impedance metallic corrugated structure. This device can be used as a power source for high gradient acceleration of electrons. To achieve precise control of the wakefield phase, a long range wakefield interferometry method was developed in which the RF energy due to the interference of the wakefields from two bunches was measured as a function of the bunch separation.

DOI •

reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPOY025

Export •

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

WEPOY026

Simulation and Measurement of the Beam Breakup Instability in a W-band Corrugated Structure

3044

D. Wang, C.-X. Tang
TUB, Beijing, People's Republic of China
S.P. Antipov, C.-J. Jing, J.Q. Qiu
Euclid TechLabs, LLC, Solon, Ohio, USA
M.E. Conde, D.S. Doran, W. Gai, G. Ha, W. Liu, J.G. Power, E.E. Wisniewski
ANL, Argonne, Illinois, USA

The corrugated wakefield structure has wide application in electron beam energy manipulation and high frequency RF radiation generation. The transverse wakefield which cause beam breakup (BBU) instability is excited when the drive beam is not perfectly centered through the structure. Here we report on the numerical and experimental investigation of the BBU effect in a W-band corrugated structure, for both cases of short range wakefield and long range wakefield. In the numerical part we develop a point to point (P2P) code that allows rapid and efficiency simulations of the beam dynamics effect by wakefield, which is based on the the particle-wake function coupled dynamics equation of motion. And the experimental measurements of BBU effect are found to be in good agreement with the simulations.

DOI •

reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPOY026

Export •

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

THPOW021

Generation of Homogeneous and Patterned Electron Beams using a Microlens Array Laser-Shaping Technique

3983

SUPSS020

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

A. Halavanau, P. Piot
Northern Illinois University, DeKalb, Illinois, USA
D.R. Edstrom, P. Piot, J. Ruan, J.K. Santucci
Fermilab, Batavia, Illinois, USA
W. Gai, G. Ha, J.G. Power, E.E. Wisniewski
ANL, Argonne, Illinois, USA
G. Ha
POSTECH, Pohang, Kyungbuk, Republic of Korea
G. Qiang
TUB, Beijing, People's Republic of China

Funding: Northern Illinois University - US DOE contract No. DE-SC0011831. Fermilab - US DOE contract No. DE-AC02-07CH11359. The Argonne wakefield facility - US DOE contract No. DE-AC02-06CH11357.
In photocathodes the achievable electron-beam parameters are controlled by the laser used to trigger the photoemission process. Non-ideal laser distribution hampers the final beam quality. Laser inhomogeneities, for instance, can be "amplified" by space-charge force and result in fragmented electron beams. To overcome this limitation laser shaping methods are routinely employed. In the present paper we demonstrate the use of simple microlens arrays to dramatically improve the transverse uniformity. We also show that this arrangement can be used to produce transversely-patterned electron beams. Our experiments are carried out at the Argonne Wakefield Accelerator facility.

DOI •

reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPOW021

Export •

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