IPAC2019 - List of Authors (Tantawi, S.G.)

Paper	Title	Page
TUPGW098	Fabrication & Cold Tests of a Millimeter-Period RF Undulator	1643
	F. Toufexis, B.J. Angier, D. Gamzina, S.G. Tantawi SLAC, Menlo Park, California, USA
	Funding: This project was funded by U.S. Department of Energy under Contract No. DE-AC02-76SF00515, and the National Science Foundation under Contract No. PHY-1415437. To reduce the linac energy required for an FEL radiating at a given wavelength, and hence its size, a smaller undulator period with sufficient field strength is needed. Previous work from our group successfully demonstrated a microwave undulator at 11.424GHz, using a corrugated cylindrical waveguide operating at the HE11 modes. We have designed a mm-wave undulator cavity at 91.392GHz* with an equivalent undulator period of 1.75 mm. This undulator requires 1.4 MW for sub microsecond pulses for an equivalent K value of 0.1. In this work we present the mechanical design and fabrication of this 91.392 GHz RF Undulator, as well as preliminary cold test data. * F. Toufexis and S.G. Tantawi, "A 1.75-mm Period RF-Driven Undulator", Proceedings of IPAC17.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPGW098
About •	paper received ※ 10 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019
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TUPTS077	Design of a High Gradient THz-Driven Electron Gun	2098
SUSPFO127	use link to see paper's listing under its alternate paper code
	S.M. Lewis, V.A. Dolgashev, A.A. Haase, E.A. Nanni, M.A.K. Othman, A.V. Sy, S.G. Tantawi SLAC, Menlo Park, California, USA D. Kim, E.I. Simakov LANL, Los Alamos, New Mexico, USA
	Funding: This work was supported by Department of Energy contract DE-AC02-76SF00515. This work was also supported by NSF grants PHY-1734015. We present the design of a high-gradient electron gun. The goal of this gun is to generate relativistic electrons using GV/m accelerating fields. The initial design is a standing-wave field-emission gun operating in the pi-mode with a cavity frequency of 110.08 GHz. A pulsed 110 GHz gyrotron oscillator will be used to drive the structure with power coupled in through a TM01 circular waveguide mode. The gun is machined in two halves which are bonded. This prototype will be used to characterize the electron beam and study RF breakdown at 110 GHz.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPTS077
About •	paper received ※ 14 May 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019
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WEPRB090	The Design of Parallel-Feed SC RF Accelerator Structure	3024
	M.H. Nasr, Z. Li, S.G. Tantawi, P.B. Welander SLAC, Menlo Park, California, USA
	Funding: Research funded by a SLAC Laboratory-Directed Research and Development award, supported by the U.S. Department of Energy, contract number DE-AC02-76SF00515 Development of superconducting RF (SRF) accelerator technology that enables both higher gradient and higher efficiency is crucial for future machines. While much of the recent R&D focus has been on materials and surface science, our aim is to optimize the cavity geometry to maximize performance with current materials. The recent demonstration of a highly efficient parallel-feed normal-conducting RF structure at SLAC has served as a proof-of-concept. Instead of coupled elliptical cells, the structure employs isolated re-entrant cells. To feed RF power to the cavities, each cell is directly coupled to an integrated manifold. The structure is made in two parts, split along the beam axis, which are then joined. Applied to SRF, simulations suggest such a structure could nearly double the achievable gradient, while reducing cryogenic RF loss by more than half. We are experimentally verifying the concept using an X-band SRF design to be tested at SLAC.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB090
About •	paper received ※ 24 May 2019 paper accepted ※ 27 May 2019 issue date ※ 21 June 2019
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THPGW080	Initial Results of High-Gradient Breakdown Tests for W-Band Accelerating Structures	3769
	M.A.K. Othman, V.A. Dolgashev, A.A. Haase, E.A. Nanni, J. Neilson, S.G. Tantawi SLAC, Menlo Park, California, USA S. Jawla, J.F. Picard, R.J. Temkin MIT/PSFC, Cambridge, Massachusetts, USA S.C. Schaub MIT, Cambridge, Massachusetts, USA B. Spataro INFN/LNF, Frascati, Italy
	Funding: This work was supported by Department of Energy contract DE-AC02-76SF00515 (SLAC) and grant DE-SC0015566 (MIT). This work was also supported by NSF grants PHY-1734015. Emerging accelerator technology at mm-wave and THz frequencies has recently shown notable progress. Indeed, metallic and dielectric accelerating structures at THz frequencies are plausible candidates toward miniaturization of accelerators. RF breakdown in such structures is a major factor limiting their performance. Therefore, comprehensive analysis of RF breakdown physics in mm-wave accelerating structures is needed, which includes understanding of dependencies of the breakdown rate on geometric, electromagnetic and material properties. In this work we report on high power tests of a 110 GHz single-cell standing wave accelerating structure powered by a 1 MW gyrotron. The RF power is coupled from the gyrotron into the accelerating structure with a Gaussian to TM01 mode converter through a quasi-optical setup. We demonstrate coupling of 10 ns, 100s of kilowatt pulses into the structure using a fast switch and achieving ~150 MV/m accelerating gradients. Measurements of RF signals and field-emitted currents allow for complete comprehensive of the high-gradient behavior of W-band structures, including breakdown probability.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPGW080
About •	paper received ※ 15 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPGW084	Corrections of Klystron Output Pulse in SW Accelerator Testing	3772
	M.H. Nasr, S.G. Tantawi SLAC, Menlo Park, California, USA
	Accelerator testing requires a good control over the shape of the used pulse. Usually, flat or stepped square pulses are used for testing. Producing a perfectly flat output pulse from the klystron can be challenging especially for testing standing wave (SW) accelerators. SW accelerator structures reflect high power back to the klystron and no isolator can withstand the reflected power level for high gradient operation. This results in a distorted output pulse from the Klystron. We developed a modulation technique that solves this problem using a negative feedback loop. This technique can also overcome a poor modulator performance and other system errors. The pulse correction feedback was successfully implemented for high gradient SW accelerator testing at SLAC and KEK.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPGW084
About •	paper received ※ 24 May 2019 paper accepted ※ 24 May 2019 issue date ※ 21 June 2019
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THPTS063	Development of a W-Band Power Extraction Structure	4252
	F. Toufexis, B.J. Angier, D. Gamzina, A. McGuire, M. Shumail, S.G. Tantawi SLAC, Menlo Park, California, USA
	Funding: This project was funded by U.S. Department of Energy under Contract No. DE-AC02-76SF00515, and the National Science Foundation under Contract No. PHY-1415437. We are modifying the X-Band Test Accelerator at SLAC to operate as an Extreme Ultra Violet (EUV) light source. The existing photo electron gun will be replaced by a thermionic X-Band injector which utilizes RF bunch compression. The beam is accelerated up to 129 MeV using an X-Band traveling wave structure followed by a novel high shunt impedance standing wave structure. The beam then goes through a mm-wave undulator with a period of 1.75 mm, producing EUV radiation around 13.5 nm. The undulator is powered by a W-Band decelerator structure, which extracts the RF power from the electron beam. In this work we present the mechanical design and fabrication of the 91.392 GHz decelerator structure, as well as structural characterization of its cavities using SEM and 3D microscopy. F. Toufexis, et al, "A Compact EUV Light Source using a mm-wave Undulator", Proceedings of IPAC17.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPTS063
About •	paper received ※ 10 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

Paper

Title

Page

Fabrication & Cold Tests of a Millimeter-Period RF Undulator

1643

F. Toufexis, B.J. Angier, D. Gamzina, S.G. Tantawi
SLAC, Menlo Park, California, USA

Funding: This project was funded by U.S. Department of Energy under Contract No. DE-AC02-76SF00515, and the National Science Foundation under Contract No. PHY-1415437.
To reduce the linac energy required for an FEL radiating at a given wavelength, and hence its size, a smaller undulator period with sufficient field strength is needed. Previous work from our group successfully demonstrated a microwave undulator at 11.424GHz, using a corrugated cylindrical waveguide operating at the HE11 modes. We have designed a mm-wave undulator cavity at 91.392GHz* with an equivalent undulator period of 1.75 mm. This undulator requires 1.4 MW for sub microsecond pulses for an equivalent K value of 0.1. In this work we present the mechanical design and fabrication of this 91.392 GHz RF Undulator, as well as preliminary cold test data.
* F. Toufexis and S.G. Tantawi, "A 1.75-mm Period RF-Driven Undulator", Proceedings of IPAC17.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPGW098

About •

paper received ※ 10 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

Export •

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

TUPTS077

Design of a High Gradient THz-Driven Electron Gun

2098

SUSPFO127

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

S.M. Lewis, V.A. Dolgashev, A.A. Haase, E.A. Nanni, M.A.K. Othman, A.V. Sy, S.G. Tantawi
SLAC, Menlo Park, California, USA
D. Kim, E.I. Simakov
LANL, Los Alamos, New Mexico, USA

Funding: This work was supported by Department of Energy contract DE-AC02-76SF00515. This work was also supported by NSF grants PHY-1734015.
We present the design of a high-gradient electron gun. The goal of this gun is to generate relativistic electrons using GV/m accelerating fields. The initial design is a standing-wave field-emission gun operating in the pi-mode with a cavity frequency of 110.08 GHz. A pulsed 110 GHz gyrotron oscillator will be used to drive the structure with power coupled in through a TM01 circular waveguide mode. The gun is machined in two halves which are bonded. This prototype will be used to characterize the electron beam and study RF breakdown at 110 GHz.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPTS077

About •

paper received ※ 14 May 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019

Export •

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

WEPRB090

The Design of Parallel-Feed SC RF Accelerator Structure

3024

M.H. Nasr, Z. Li, S.G. Tantawi, P.B. Welander
SLAC, Menlo Park, California, USA

Funding: Research funded by a SLAC Laboratory-Directed Research and Development award, supported by the U.S. Department of Energy, contract number DE-AC02-76SF00515
Development of superconducting RF (SRF) accelerator technology that enables both higher gradient and higher efficiency is crucial for future machines. While much of the recent R&D focus has been on materials and surface science, our aim is to optimize the cavity geometry to maximize performance with current materials. The recent demonstration of a highly efficient parallel-feed normal-conducting RF structure at SLAC has served as a proof-of-concept. Instead of coupled elliptical cells, the structure employs isolated re-entrant cells. To feed RF power to the cavities, each cell is directly coupled to an integrated manifold. The structure is made in two parts, split along the beam axis, which are then joined. Applied to SRF, simulations suggest such a structure could nearly double the achievable gradient, while reducing cryogenic RF loss by more than half. We are experimentally verifying the concept using an X-band SRF design to be tested at SLAC.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPRB090

About •

paper received ※ 24 May 2019 paper accepted ※ 27 May 2019 issue date ※ 21 June 2019

Export •

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

THPGW080

Initial Results of High-Gradient Breakdown Tests for W-Band Accelerating Structures

3769

M.A.K. Othman, V.A. Dolgashev, A.A. Haase, E.A. Nanni, J. Neilson, S.G. Tantawi
SLAC, Menlo Park, California, USA
S. Jawla, J.F. Picard, R.J. Temkin
MIT/PSFC, Cambridge, Massachusetts, USA
S.C. Schaub
MIT, Cambridge, Massachusetts, USA
B. Spataro
INFN/LNF, Frascati, Italy

Funding: This work was supported by Department of Energy contract DE-AC02-76SF00515 (SLAC) and grant DE-SC0015566 (MIT). This work was also supported by NSF grants PHY-1734015.
Emerging accelerator technology at mm-wave and THz frequencies has recently shown notable progress. Indeed, metallic and dielectric accelerating structures at THz frequencies are plausible candidates toward miniaturization of accelerators. RF breakdown in such structures is a major factor limiting their performance. Therefore, comprehensive analysis of RF breakdown physics in mm-wave accelerating structures is needed, which includes understanding of dependencies of the breakdown rate on geometric, electromagnetic and material properties. In this work we report on high power tests of a 110 GHz single-cell standing wave accelerating structure powered by a 1 MW gyrotron. The RF power is coupled from the gyrotron into the accelerating structure with a Gaussian to TM01 mode converter through a quasi-optical setup. We demonstrate coupling of 10 ns, 100s of kilowatt pulses into the structure using a fast switch and achieving ~150 MV/m accelerating gradients. Measurements of RF signals and field-emitted currents allow for complete comprehensive of the high-gradient behavior of W-band structures, including breakdown probability.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPGW080

About •

paper received ※ 15 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

Export •

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

THPGW084

Corrections of Klystron Output Pulse in SW Accelerator Testing

3772

M.H. Nasr, S.G. Tantawi
SLAC, Menlo Park, California, USA

Accelerator testing requires a good control over the shape of the used pulse. Usually, flat or stepped square pulses are used for testing. Producing a perfectly flat output pulse from the klystron can be challenging especially for testing standing wave (SW) accelerators. SW accelerator structures reflect high power back to the klystron and no isolator can withstand the reflected power level for high gradient operation. This results in a distorted output pulse from the Klystron. We developed a modulation technique that solves this problem using a negative feedback loop. This technique can also overcome a poor modulator performance and other system errors. The pulse correction feedback was successfully implemented for high gradient SW accelerator testing at SLAC and KEK.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPGW084

About •

paper received ※ 24 May 2019 paper accepted ※ 24 May 2019 issue date ※ 21 June 2019

Export •

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

THPTS063

Development of a W-Band Power Extraction Structure

4252

F. Toufexis, B.J. Angier, D. Gamzina, A. McGuire, M. Shumail, S.G. Tantawi
SLAC, Menlo Park, California, USA

Funding: This project was funded by U.S. Department of Energy under Contract No. DE-AC02-76SF00515, and the National Science Foundation under Contract No. PHY-1415437.
We are modifying the X-Band Test Accelerator at SLAC to operate as an Extreme Ultra Violet (EUV) light source*. The existing photo electron gun will be replaced by a thermionic X-Band injector which utilizes RF bunch compression. The beam is accelerated up to 129 MeV using an X-Band traveling wave structure followed by a novel high shunt impedance standing wave structure. The beam then goes through a mm-wave undulator with a period of 1.75 mm, producing EUV radiation around 13.5 nm. The undulator is powered by a W-Band decelerator structure, which extracts the RF power from the electron beam. In this work we present the mechanical design and fabrication of the 91.392 GHz decelerator structure, as well as structural characterization of its cavities using SEM and 3D microscopy.
* F. Toufexis, et al, "A Compact EUV Light Source using a mm-wave Undulator", Proceedings of IPAC17.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPTS063

About •

paper received ※ 10 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

Export •

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