IPAC2016 - List of Authors (Tantawi, S.G.)

Paper	Title	Page
MOOCA01	R&D of a Super-compact SLED System at SLAC	39
	J.W. Wang, G.B. Bowden, S. Condamoor, Y. Ding, V.A. Dolgashev, J.P. Eichner, M.A. Franzi, A.A. Haase, P. Krejcik, J.R. Lewandowski, S.G. Tantawi, L. Xiao, C. Xu SLAC, Menlo Park, California, USA
	Funding: Work supported by Department of Energy contract DE-AC03-76SF00515. We have successfully designed, fabricated, installed and tested a super-compact X-Band SLED system at SLAC. It is composed of an elegant mode converter/polarizer and a single sphere energy store cavity with high Q of 94000 and diameter less than 12 cm. The available RF peak power of 50 MW can be compressed to peak average power of more than 200 MW in order to double the kick for the electron bunches in a RF transverse deflector system and greatly improve the measurement resolution for both the electron bunch and the x-ray FEL pulse. High power operation has demonstrated the excellent performance of this RF compression system without any problems in RF breakdown, pulse heating and radiation. The design physics and fabrication as well as the measurement results will be presented in detail.
	Slides MOOCA01 [20.278 MB]
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOOCA01
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MOPMW038	Measurements of Copper RF Surface Resistance at Cryogenic Temperatures for Applications to X-Band and S-Band Accelerators	487
	A.D. Cahill, A. Fukasawa, J.B. Rosenzweig UCLA, Los Angeles, California, USA G.B. Bowden, V.A. Dolgashev, M.A. Franzi, S.G. Tantawi, P.B. Welander, C. Yoneda SLAC, Menlo Park, California, USA J. Guo JLab, Newport News, Virginia, USA Y. Higashi OIST, Onna-son, Okinawa, Japan
	Funding: Funding from DOE SCGSR and DOE/SU Contract DE-AC02-76-SF00515 Recent SLAC experiments with cryogenically cooled X-Band standing wave copper accelerating cavities have shown that these structures can operate with accelerating gradients of ~250 MV/m and low breakdown rates. These results prompted us to perform systematic studies of copper rf properties at cryogenic temperatures and low rf power. We placed copper cavities into a cryostat cooled by a pulse tube cryocooler, so cavities could be cooled to 4K. We used different shapes of cavities for the X-Band and S-Band measurements. Properties of the cavities were measured using a network analyzer. We calculated rf surface resistance from measured Q0 and Q external of the cavity at temperatures from 4 K to room temperature. The results were then compared to the theory proposed by Reuter and Sondheimer. These measurements are a part of studies with the goal of reaching very high operational accelerating gradients in normal conducting rf structures.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPMW038
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MOPMW040	Electron Beam Excitation of a Surface Wave in mm-Wave Open Accelerating Structures	494
	M. Dal Forno, G.B. Bowden, C.I. Clarke, V.A. Dolgashev, M.J. Hogan, D.J. McCormick, A. Novokhatski, B.D. O'Shea, S.G. Tantawi, S.P. Weathersby SLAC, Menlo Park, California, USA B. Spataro INFN/LNF, Frascati (Roma), Italy
	Funding: Work supported by the US DOE under contract DE-AC02-76SF00515. As part of research on the physics of rf breakdowns we performed experiments with high gradient traveling-wave mm-wave accelerating structures. The accelerating structures are open, composed of two identical halves separated by an adjustable gap. The electromagnetic fields are excited by an ultra-relativistic electron beam. We observed that a confined travelling-wave mode exists in half of the accelerating structure. The experiments were conducted at FACET facility at SLAC National Accelerator Laboratory. Depending on the gap width, the accelerating structure had beam-synchronous frequencies that vary from 90 to 140 GHz. When we opened the gap by more than half wavelength the synchronous wave remains trapped. Its behavior is consistent with the so called "surface wave". We characterized this beam-wave interaction by several methods: measurement of the radiated rf energy with the pyro-detector, measurement of the spectrum with an interferometer, measurement of the beam deflection by using the beam position monitors and profile monitor.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPMW040
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MOPMW041	Measurements of RF Breakdowns in Beam Driven mm-Wave Accelerating Structures	497
	M. Dal Forno, G.B. Bowden, C.I. Clarke, V.A. Dolgashev, M.J. Hogan, D.J. McCormick, A. Novokhatski, S.G. Tantawi, S.P. Weathersby SLAC, Menlo Park, California, USA B. Spataro INFN/LNF, Frascati (Roma), Italy
	Funding: Work supported by the US DOE under contract DE-AC02-76SF00515 We studied the physics and properties of rf breakdowns in high gradient traveling-wave accelerating structures at 100 GHz. The structures are open, made of two halves with a gap in between. The rf fields were excited in the structure by an ultra-relativistic electron beam generated by the FACET facility at the SLAC National Accelerator Laboratory. We observed rf breakdowns generated in the presence of GV/m scale electric fields. We varied the rf fields excited by the FACET bunch by moving structure relative to the beam and by changing the gap between structure halves. Reliable breakdowns detectors allowed us to measure the rf breakdown rate at these different rf parameters. We measured radiated rf energy with a pyro-detector. When the beam was off-axis, we observed beam deflection in the beam position monitors and on the screen of a magnetic spectrometer. The measurements of the deflection allowed us to verify our calculation of the accelerating gradient.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPMW041
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MOPMW042	Multi-Dimensional RF Sources Design	501
	M. Dal Forno, A. Jensen, R.D. Ruth, S.G. Tantawi SLAC, Menlo Park, California, USA
	Funding: Work supported by the US DOE under contract DE-AC02-76SF00515. Vacuum electronic devices, such as rf sources for accelerator applications, must provide high rf power with high efficiency. To achieve these requirements, multi-beam klystron and sheet-beam klystron devices have been developed. Multi-beam klystrons, at high frequency employ separate output cavities; hence they have the disadvantage that combining all the rf pulses, generated by all the beams, is challenging. Sheet-beam klystrons have problems with instabilities and with space charge forces that makes the beam not naturally confined. We are proposing an alternative approach that reduces space charge problems, by adopting geometries in which the space charge forces are naturally balanced. An example is when the electron beam is generated by a central source (well) and the electron motion corresponds to the natural expansion of the electron cloud (three-dimensional device). In this paper we will present the design and challenges of a bi-dimensional rf source, a cylindrical klystron, composed by concentric pancake resonant cavities. In this case, space charge forces are naturally balanced in the azimuthal direction.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPMW042
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MOPMY034	The Distributed Bunch Amplifier	573
	M.A. Franzi, A. Jensen, S.G. Tantawi, F. Toufexis, A.R. Vrielink SLAC, Menlo Park, California, USA
	The Distributed Bunch Amplifier (DBA) is a high efficiency RF source that utilizes a phase locked deflecting cavity and output circuit to produce a synchronous beam-wave interaction. The DBA improves on the design of previous embodiments of this technology, such as the Gyrocon, by implementing a modern decoupled output circuit design and conical PPM beam focusing array in order to scale to higher frequencies and efficiency than previously demonstrated. Presented is a proof-of-concept S-band, 2.856 GHz, device operating with a 60 kV, 8 Amp, electron beam. Each stage of the three-cavity decoupled output circuit is optimized based on complex amplitude and shunt impedance to achieve an electronic efficiency of greater than 90%. Initial numerical analysis of this design indicates that an overall operating efficiency of greater than 70% is feasible. Detailed simulated results of the S-band model and designs to scale this technology to higher power and frequency will be discussed. Budker, G. I., et al. "The Gyrocon: An Efficient Relativistic High Power VHF Generator." Part. Accel. 10 (1979): 41-59.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPMY034
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MOPMY035	Theoretical Analysis and Simulation of a Compact Frequency Multiplier for High Power Millimeter and Terahertz Sources	576
SUPSS098	use link to see paper's listing under its alternate paper code
	A.R. Vrielink, S.G. Tantawi, F. Toufexis SLAC, Menlo Park, California, USA
	As the demands on accelerating gradients and the temporal resolution of beam diagnostics and manipulation schemes grow, millimeter-wave and terahertz (THz) accelerator structures may present a natural solution. The recent advent of a radiofrequency undulator and the development of a 0.45 THz accelerator demonstrate growing interest in this frequency regime; however, growth in this area is limited by the lack of efficient, compact high power sources. We present a novel vacuum electronic device featuring an interaction between a radially bunched electron beam and azimuthally traveling waves. The use of an inward traveling radial sheet beam mitigates space charge effects at the low operating energy of 10-30 keV and allows for a high input beam current of approximately 0.5-10 A. Based on preliminary calculations, these devices could operate from 50 GHz to 250 GHz with tens of kiloWatts of output power, while the expected efficiency would scale from 60% at 80 GHz to 15% at 230 GHz. Here we present the underlying theory, possible structure design, and preliminary results from analytical calculations and simulation. Tantawi, S. et al. Phys. Rev. Lett. 112, 164802 (April, 2014) Nanni, E. et al. Nat. Commun. 6, 8486 (October, 2015)
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPMY035
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MOPMY036	High-harmonic mm-Wave Frequency Multiplication using a Gyrocon-like Device	579
	F. Toufexis, V.A. Dolgashev, M.V. Fazio, A. Jensen, S.G. Tantawi, A.R. Vrielink SLAC, Menlo Park, California, USA P. Borchard Dymenso LLC, San Francisco, USA
	Funding: This project was funded by U.S. Department of Energy under Contract No. DE-AC02-76SF00515, and the National Science Foundation. Traditional linear interaction RF sources, such as Klystrons and Traveling Wave Tubes, fail to produce significant power levels at millimeter wavelengths. This is because their critical dimensions are small compared to the wavelength, and the output power scales as the square of the wavelength. We present a vacuum tube technology, where the device size is inherently larger than the operating wavelength. We designed a low–voltage mm–wave source, with an output interaction circuit based on a spherical sector cavity. This device was configured as a phased-locked frequency multiplier. We report the design and cold test results of a proof-of-principle fifth harmonic frequency multiplier with an output frequency of 57.12 GHz.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPMY036
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TUPOW030	A CW Normal Conducting RF Cavity for Fast Chirp Control in the LCLS-II	1817
	M.H. Nasr, P. Emma, S.G. Tantawi SLAC, Menlo Park, California, USA
	The LCLS-II is a high repetition-rate Free-Electron Laser (FEL) facility under construction at SLAC. A new 4-GeV continuous wave (CW) superconducting (SC) L-band linac is being built to provide an electron bunch rate of up to 1 MHz, with bunches rapidly switched between two FEL undulators. It is desirable to provide peak current (i.e., pulse length) control in each FEL independently by varying the RF phase (chirp) prior to the first bunch compressor. However, the high-Q, SCRF, with its 1-ms fill-time, cannot be changed within one bunch spacing (1 us). So to provide a small chirp adjustment from bunch to bunch, we propose a short CW copper RF accelerating cavity, located just after the injector, with < 250-ns fill-time designed to adjust the beam chirp at zero-crossing phase. We examined RF cavity designs spanning RF frequencies from L-band to X-band. We considered both SW and TW structures. We found an optimal solution with 2 cm iris diameter, SW RF cavity, operating at C-band with input power of only 10 kW. If one can afford to operate with smaller diameter, from a wakefield point of view, then similar structure at X-band may require only 500 W with 5 mm iris diameter.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPOW030
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THPOR044	mm-Wave Standing-Wave Accelerating Structures for High-Gradient Tests	3884
	E.A. Nanni, M. Dal Forno, V.A. Dolgashev, J. Neilson, S.G. Tantawi SLAC, Menlo Park, California, USA S.C. Schaub MIT, Cambridge, Massachusetts, USA R.J. Temkin MIT/PSFC, Cambridge, Massachusetts, USA
	We present the design and parameters of single-cell accelerating structures for high-gradient testing at 110 GHz. The purpose of this work is to study the basic physics of ultrahigh vacuum RF breakdown in high-gradient RF accelerators. The accelerating structures consist of pi-mode standing-wave cavities fed with TM01 circular waveguide mode. The geometry and field shape of these accelerating structures is as close as practical to single-cell standing-wave X-band accelerating structures, more than 40 of which were tested at SLAC. This wealth of X-band data will serve as a baseline for these 110 GHz tests. The structures will be powered from a pulsed MW gyrotron oscillator. One MW of RF power from the gyrotron may allow us to reach a peak accelerating gradient of 400 MeV/m.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPOR044
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Paper

Title

Page

R&D of a Super-compact SLED System at SLAC

39

J.W. Wang, G.B. Bowden, S. Condamoor, Y. Ding, V.A. Dolgashev, J.P. Eichner, M.A. Franzi, A.A. Haase, P. Krejcik, J.R. Lewandowski, S.G. Tantawi, L. Xiao, C. Xu
SLAC, Menlo Park, California, USA

Funding: Work supported by Department of Energy contract DE-AC03-76SF00515.
We have successfully designed, fabricated, installed and tested a super-compact X-Band SLED system at SLAC. It is composed of an elegant mode converter/polarizer and a single sphere energy store cavity with high Q of 94000 and diameter less than 12 cm. The available RF peak power of 50 MW can be compressed to peak average power of more than 200 MW in order to double the kick for the electron bunches in a RF transverse deflector system and greatly improve the measurement resolution for both the electron bunch and the x-ray FEL pulse. High power operation has demonstrated the excellent performance of this RF compression system without any problems in RF breakdown, pulse heating and radiation. The design physics and fabrication as well as the measurement results will be presented in detail.

Slides MOOCA01 [20.278 MB]

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reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOOCA01

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MOPMW038

Measurements of Copper RF Surface Resistance at Cryogenic Temperatures for Applications to X-Band and S-Band Accelerators

487

A.D. Cahill, A. Fukasawa, J.B. Rosenzweig
UCLA, Los Angeles, California, USA
G.B. Bowden, V.A. Dolgashev, M.A. Franzi, S.G. Tantawi, P.B. Welander, C. Yoneda
SLAC, Menlo Park, California, USA
J. Guo
JLab, Newport News, Virginia, USA
Y. Higashi
OIST, Onna-son, Okinawa, Japan

Funding: Funding from DOE SCGSR and DOE/SU Contract DE-AC02-76-SF00515
Recent SLAC experiments with cryogenically cooled X-Band standing wave copper accelerating cavities have shown that these structures can operate with accelerating gradients of ~250 MV/m and low breakdown rates. These results prompted us to perform systematic studies of copper rf properties at cryogenic temperatures and low rf power. We placed copper cavities into a cryostat cooled by a pulse tube cryocooler, so cavities could be cooled to 4K. We used different shapes of cavities for the X-Band and S-Band measurements. Properties of the cavities were measured using a network analyzer. We calculated rf surface resistance from measured Q0 and Q external of the cavity at temperatures from 4 K to room temperature. The results were then compared to the theory proposed by Reuter and Sondheimer. These measurements are a part of studies with the goal of reaching very high operational accelerating gradients in normal conducting rf structures.

DOI •

reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPMW038

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MOPMW040

Electron Beam Excitation of a Surface Wave in mm-Wave Open Accelerating Structures

494

M. Dal Forno, G.B. Bowden, C.I. Clarke, V.A. Dolgashev, M.J. Hogan, D.J. McCormick, A. Novokhatski, B.D. O'Shea, S.G. Tantawi, S.P. Weathersby
SLAC, Menlo Park, California, USA
B. Spataro
INFN/LNF, Frascati (Roma), Italy

Funding: Work supported by the US DOE under contract DE-AC02-76SF00515.
As part of research on the physics of rf breakdowns we performed experiments with high gradient traveling-wave mm-wave accelerating structures. The accelerating structures are open, composed of two identical halves separated by an adjustable gap. The electromagnetic fields are excited by an ultra-relativistic electron beam. We observed that a confined travelling-wave mode exists in half of the accelerating structure. The experiments were conducted at FACET facility at SLAC National Accelerator Laboratory. Depending on the gap width, the accelerating structure had beam-synchronous frequencies that vary from 90 to 140 GHz. When we opened the gap by more than half wavelength the synchronous wave remains trapped. Its behavior is consistent with the so called "surface wave". We characterized this beam-wave interaction by several methods: measurement of the radiated rf energy with the pyro-detector, measurement of the spectrum with an interferometer, measurement of the beam deflection by using the beam position monitors and profile monitor.

DOI •

reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPMW040

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MOPMW041

Measurements of RF Breakdowns in Beam Driven mm-Wave Accelerating Structures

497

M. Dal Forno, G.B. Bowden, C.I. Clarke, V.A. Dolgashev, M.J. Hogan, D.J. McCormick, A. Novokhatski, S.G. Tantawi, S.P. Weathersby
SLAC, Menlo Park, California, USA
B. Spataro
INFN/LNF, Frascati (Roma), Italy

Funding: Work supported by the US DOE under contract DE-AC02-76SF00515
We studied the physics and properties of rf breakdowns in high gradient traveling-wave accelerating structures at 100 GHz. The structures are open, made of two halves with a gap in between. The rf fields were excited in the structure by an ultra-relativistic electron beam generated by the FACET facility at the SLAC National Accelerator Laboratory. We observed rf breakdowns generated in the presence of GV/m scale electric fields. We varied the rf fields excited by the FACET bunch by moving structure relative to the beam and by changing the gap between structure halves. Reliable breakdowns detectors allowed us to measure the rf breakdown rate at these different rf parameters. We measured radiated rf energy with a pyro-detector. When the beam was off-axis, we observed beam deflection in the beam position monitors and on the screen of a magnetic spectrometer. The measurements of the deflection allowed us to verify our calculation of the accelerating gradient.

DOI •

reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPMW041

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MOPMW042

Multi-Dimensional RF Sources Design

501

M. Dal Forno, A. Jensen, R.D. Ruth, S.G. Tantawi
SLAC, Menlo Park, California, USA

Funding: Work supported by the US DOE under contract DE-AC02-76SF00515.
Vacuum electronic devices, such as rf sources for accelerator applications, must provide high rf power with high efficiency. To achieve these requirements, multi-beam klystron and sheet-beam klystron devices have been developed. Multi-beam klystrons, at high frequency employ separate output cavities; hence they have the disadvantage that combining all the rf pulses, generated by all the beams, is challenging. Sheet-beam klystrons have problems with instabilities and with space charge forces that makes the beam not naturally confined. We are proposing an alternative approach that reduces space charge problems, by adopting geometries in which the space charge forces are naturally balanced. An example is when the electron beam is generated by a central source (well) and the electron motion corresponds to the natural expansion of the electron cloud (three-dimensional device). In this paper we will present the design and challenges of a bi-dimensional rf source, a cylindrical klystron, composed by concentric pancake resonant cavities. In this case, space charge forces are naturally balanced in the azimuthal direction.

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reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPMW042

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MOPMY034

The Distributed Bunch Amplifier

573

M.A. Franzi, A. Jensen, S.G. Tantawi, F. Toufexis, A.R. Vrielink
SLAC, Menlo Park, California, USA

The Distributed Bunch Amplifier (DBA) is a high efficiency RF source that utilizes a phase locked deflecting cavity and output circuit to produce a synchronous beam-wave interaction. The DBA improves on the design of previous embodiments of this technology, such as the Gyrocon*, by implementing a modern decoupled output circuit design and conical PPM beam focusing array in order to scale to higher frequencies and efficiency than previously demonstrated. Presented is a proof-of-concept S-band, 2.856 GHz, device operating with a 60 kV, 8 Amp, electron beam. Each stage of the three-cavity decoupled output circuit is optimized based on complex amplitude and shunt impedance to achieve an electronic efficiency of greater than 90%. Initial numerical analysis of this design indicates that an overall operating efficiency of greater than 70% is feasible. Detailed simulated results of the S-band model and designs to scale this technology to higher power and frequency will be discussed.
* Budker, G. I., et al. "The Gyrocon: An Efficient Relativistic High Power VHF Generator." Part. Accel. 10 (1979): 41-59.

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reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPMY034

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MOPMY035

Theoretical Analysis and Simulation of a Compact Frequency Multiplier for High Power Millimeter and Terahertz Sources

576

SUPSS098

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

A.R. Vrielink, S.G. Tantawi, F. Toufexis
SLAC, Menlo Park, California, USA

As the demands on accelerating gradients and the temporal resolution of beam diagnostics and manipulation schemes grow, millimeter-wave and terahertz (THz) accelerator structures may present a natural solution. The recent advent of a radiofrequency undulator and the development of a 0.45 THz accelerator demonstrate growing interest in this frequency regime; however, growth in this area is limited by the lack of efficient, compact high power sources. We present a novel vacuum electronic device featuring an interaction between a radially bunched electron beam and azimuthally traveling waves. The use of an inward traveling radial sheet beam mitigates space charge effects at the low operating energy of 10-30 keV and allows for a high input beam current of approximately 0.5-10 A. Based on preliminary calculations, these devices could operate from 50 GHz to 250 GHz with tens of kiloWatts of output power, while the expected efficiency would scale from 60% at 80 GHz to 15% at 230 GHz. Here we present the underlying theory, possible structure design, and preliminary results from analytical calculations and simulation.
Tantawi, S. et al. Phys. Rev. Lett. 112, 164802 (April, 2014)
Nanni, E. et al. Nat. Commun. 6, 8486 (October, 2015)

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reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPMY035

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MOPMY036

High-harmonic mm-Wave Frequency Multiplication using a Gyrocon-like Device

579

F. Toufexis, V.A. Dolgashev, M.V. Fazio, A. Jensen, S.G. Tantawi, A.R. Vrielink
SLAC, Menlo Park, California, USA
P. Borchard
Dymenso LLC, San Francisco, USA

Funding: This project was funded by U.S. Department of Energy under Contract No. DE-AC02-76SF00515, and the National Science Foundation.
Traditional linear interaction RF sources, such as Klystrons and Traveling Wave Tubes, fail to produce significant power levels at millimeter wavelengths. This is because their critical dimensions are small compared to the wavelength, and the output power scales as the square of the wavelength. We present a vacuum tube technology, where the device size is inherently larger than the operating wavelength. We designed a low–voltage mm–wave source, with an output interaction circuit based on a spherical sector cavity. This device was configured as a phased-locked frequency multiplier. We report the design and cold test results of a proof-of-principle fifth harmonic frequency multiplier with an output frequency of 57.12 GHz.

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reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPMY036

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TUPOW030

A CW Normal Conducting RF Cavity for Fast Chirp Control in the LCLS-II

1817

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

The LCLS-II is a high repetition-rate Free-Electron Laser (FEL) facility under construction at SLAC. A new 4-GeV continuous wave (CW) superconducting (SC) L-band linac is being built to provide an electron bunch rate of up to 1 MHz, with bunches rapidly switched between two FEL undulators. It is desirable to provide peak current (i.e., pulse length) control in each FEL independently by varying the RF phase (chirp) prior to the first bunch compressor. However, the high-Q, SCRF, with its 1-ms fill-time, cannot be changed within one bunch spacing (1 us). So to provide a small chirp adjustment from bunch to bunch, we propose a short CW copper RF accelerating cavity, located just after the injector, with < 250-ns fill-time designed to adjust the beam chirp at zero-crossing phase. We examined RF cavity designs spanning RF frequencies from L-band to X-band. We considered both SW and TW structures. We found an optimal solution with 2 cm iris diameter, SW RF cavity, operating at C-band with input power of only 10 kW. If one can afford to operate with smaller diameter, from a wakefield point of view, then similar structure at X-band may require only 500 W with 5 mm iris diameter.

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reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPOW030

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THPOR044

mm-Wave Standing-Wave Accelerating Structures for High-Gradient Tests

3884

E.A. Nanni, M. Dal Forno, V.A. Dolgashev, J. Neilson, S.G. Tantawi
SLAC, Menlo Park, California, USA
S.C. Schaub
MIT, Cambridge, Massachusetts, USA
R.J. Temkin
MIT/PSFC, Cambridge, Massachusetts, USA

We present the design and parameters of single-cell accelerating structures for high-gradient testing at 110 GHz. The purpose of this work is to study the basic physics of ultrahigh vacuum RF breakdown in high-gradient RF accelerators. The accelerating structures consist of pi-mode standing-wave cavities fed with TM01 circular waveguide mode. The geometry and field shape of these accelerating structures is as close as practical to single-cell standing-wave X-band accelerating structures, more than 40 of which were tested at SLAC. This wealth of X-band data will serve as a baseline for these 110 GHz tests. The structures will be powered from a pulsed MW gyrotron oscillator. One MW of RF power from the gyrotron may allow us to reach a peak accelerating gradient of 400 MeV/m.

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reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPOR044

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