IPAC2017 - List of Authors (Nanni, E.A.)

Paper	Title	Page
MOPIK004	Demonstration of an All-Optically Driven Sub-keV THz Gun	503
	W.R. Huang, K.-H. Hong, F.X. Kärtner, E.A. Nanni, KR. Ravi MIT, Cambridge, Massachusetts, USA A-L. Calendron, H. Cankaya, A. Fallahi, F.X. Kärtner, X. Wu CFEL, Hamburg, Germany D. Zhang DESY, Hamburg, Germany
	Funding: European Research Council under the European Union Seventh Framework Program (FP/2007-2013)/ERC Grant Agreement no. 609920 Intense ultrashort THz and optical pulses with single-cycle pulse duration became possible after the recent advances in ultrafast technologies. Using such ultrashort pulses for electron acceleration offers advantages in terms of higher thresholds for material breakdown which opens up a promising path towards increased acceleration gradients. In addition, using optically generated THz pulses enable inherently synchronized acceleration schemes, since accelerating field and particle injecting field are excited by a single seed laser. In this contribution, we present the first experimental demonstration of laser-driven THz acceleration of electrons initially at rest. It is shown that strong-field, single-cycle THz fields accelerate electrons with peak energies of up to 0.8 keV in an ultracompact THz gun with bunch charge of 40 fC. The achieved energy spreads are as low as 5.8%.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPIK004
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MOPAB150	Imaging the Spatial Modulation of a Relativistic Electron Beam	480
	C. Zhang, W.S. Graves, L.E. Malin, J. Spence Arizona State University, Tempe, USA D.B. Cesar, J.M. Maxson, P. Musumeci, A. Urbanowicz UCLA, Los Angeles, USA C. Limborg, E.A. Nanni SLAC, Menlo Park, California, USA
	Funding: Work supported by NSF awards 1632780, 1415583, 1231306 and DOE award de-sc0009914 We describe Bragg diffraction of relativistic electron beams through a patterned Si crystal consisting of alternating thick and thin strips to produce nanometer scale electron density modulations. Multi-slice simulations show that a two-beam situation can be set up where, for a particular thickness of Si, nearly 100% of the electron beam is diffracted. Plans are underway to carry out experiments showing this effect in UCLA's ultrafast electron microscopy lab with 3.5 MeV electrons. We will select either the diffracted beam or the primary beam with a small aperture in the diffraction plane of a magnetic lens, and so record either the dark or bright field magnified image of the strips. Our first goal is to observe the nanopatterned beam at the image plane. We will then investigate various crystal thickness and sample orientations to maximize the contrast in the pattern and explore tuning the period of the modulation through varying magnification.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPAB150
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TUPAB139	Design of an X-Band Photoinjector Operating at 1 kHz	1659
	W.S. Graves, A.C. Goodrich, M.R. Holl, N.J. O'Brien Arizona State University, Tempe, USA V. Bharadwaj, P. Borchard Tibaray Inc., Stanford, USA V.A. Dolgashev, E.A. Nanni SLAC, Menlo Park, California, USA
	A kHz repetition rate RF photoinjector with novel features has been designed for the ASU CXLS project. The photoinjector consists of a 9.3 GHz 4.5 cell standing-wave RF cavity that is constructed from 2 halves. The halves are brazed together, with the braze joint bisecting the irises and cells, greatly simplifying its construction. The cathode is brazed onto this assembly. RF power is coupled into the cavity through inline circular waveguide using a demountable TM01 mode launcher. The mode launcher feeds the power through 4 ports distributed azimuthally to eliminate both dipole and quadrupole field distortions. The brazed-in cathode and absence of complex power coupler result in a very inexpensive yet high performance device. The clean design allows the RF cavity to sit entirely within the solenoid assembly. The cathode gradient is 120 MV/m at 3 MW of input power. The cathode cell is just 0.17 RF wavelength so that laser arrival phase for peak acceleration is 70 degrees from zero crossing resulting in exit energy of 4 MeV. The photoinjector will operate with 1μs pulses at 1 kHz, dissipating 3 kW of heat. Details of the design are presented.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-TUPAB139
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WEPAB138	Prototyping High-Gradient mm-Wave Accelerating Structures	2902
	E.A. Nanni, V.A. Dolgashev, A.A. Haase, J. Neilson, S.G. Tantawi SLAC, Menlo Park, California, USA S.C. Schaub MIT, Cambridge, Massachusetts, USA B. Spataro INFN/LNF, Frascati (Roma), Italy R.J. Temkin MIT/PSFC, Cambridge, Massachusetts, USA
	We present single-cell accelerating structures designed 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 are pi-mode standing-wave cavities fed with a TM01 circular waveguide. The structures are fabricated using precision milling out of two metal blocks, and the blocks are joined with diffusion bonding and brazing. The impact of fabrication and joining techniques on the cell geometry and RF performance will be discussed. First prototypes had a measured Qo of 2800, approaching the theoretical design value of 3300. The geometry of these accelerating structures are 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 with short pulses from a MW gyrotron oscillator. RF power of 1 MW may allow us to reach an accelerating gradient of 400 MeV/m.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPAB138
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THPAB079	Terahertz Chirper for the Bunch Compression of Ultra-Low Emittance Beams	3899
	A.R. Vrielink, A. Marinelli, E.A. Nanni SLAC, Menlo Park, California, USA
	Recent efforts have demonstrated the possibility of achieving ultralow transverse emittance beams for high brightness light sources and free electron lasers. While these lower emittances should translate to improved lasing efficiency and higher peak brightness in FELs, these beams are commensurately more vulnerable to coherent synchrotron radiation (CSR) for the selfsame reasons. Conserving these ultralow emittances through the bunch compressors in an FEL given their increased propensity to emit CSR is particularly challenging. We investigate the possibility of imposing a large energy chirp at terahertz wavelengths to reduce the required magnetic fields in the compressor, counteracting the ultralow emittance in the generation of CSR. A second, higher frequency THz chirper would then be used to dechirp the beam after the chicane. Operation at THz as opposed to conventional radiofrequencies offers significantly larger chirp at similar input powers, yet still with wavelengths greater than typical FEL bunch lengths (several femtoseconds). Potential experimental schemes will be suggested in the context of LCLS and their feasibility evaluated. S. Bettoni, M. Pedrozzi and S. Reiche, Phys. Rev. ST Accel. Beams. 18, 123403 (December, 2015).
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPAB079
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THPAB088	Comparison of Theory, Simulation, and Experiment for Dynamical Extinction of Relativistic Electron Beams Diffracted Through a Si Crystal Membrane	3924
SUSPSIK064	use link to see paper's listing under its alternate paper code
	L.E. Malin, W.S. Graves, J. Spence, C. Zhang Arizona State University, Tempe, USA R.K. Li, C. Limborg, E.A. Nanni, X. Shen, S.P. Weathersby SLAC, Menlo Park, California, USA
	Diffraction in the transmission geometry through a single-crystal silicon slab is exploited to control the intensity of a relativistic electron beam. The choice of crystal thickness and incidence angle can extinguish or maximize the transmitted beam intensity via coherent multiple Bragg scattering; thus, the crystal acts as a dynamical beam stop through the Pendel'sung effect, a well-known phenomenon in X-ray and electron diffraction. In an initial experiment, we have measured the ability of this method to transmit or extinguish the primary beam and diffract into a single Bragg peak. Using lithographic etching of patterns in the crystal we intend to use this method to nanopattern an electron beam for production of coherent x-rays. We compare the experimental results with simulations using the multislice method to model the diffraction pattern from a perfect silicon crystal of uniform thickness, considering multiple scattering, crystallographic orientation, temperature effects, and partial coherence from the momentum spread of the beam. The simulations are compared to data collected at the ASTA UED facility at SLAC for a 340 nm thick Si(100) wafer with a beam energy of 2.35 MeV.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPAB088
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THPIK126	Design of a Field-Emission X-Band Gun Driven by Solid-State RF Source	4399
	E.A. Nanni, V.A. Dolgashev, J. Neilson, S.G. Tantawi SLAC, Menlo Park, California, USA B.E. Carlsten, J.W. Lewellen, D.C. Nguyen LANL, Los Alamos, New Mexico, USA M. Othman UCI, Irvine, California, USA
	We present the design of a field-emission X-band gun designed to be powered using a solid-state RF source. The source of the electron beam is a field emission nano-tip array. The RF gun is intended to be a beam source for 1 MeV solid-state driven linac for deployment on a satellite to map magnetic fields in the magnetosphere. The gun has to satisfy strict requirements on both average and peak power consumption, as well as rapid turn on time. In order to achieve low power consumption, the RF gun operates at relatively low accelerating gradient of 2 MeV/m. The beam exit energy is ~20 keV for an RF power 1.5 kW. Each cell of the RF gun is separately powered by commercially available, GaN high electron mobility transistors. In proof of principle experiments we successfully powered a 9.3 GHz accelerating cavity with a 100 W transistor and a 1% duty cycle.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPIK126
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Paper

Title

Page

Demonstration of an All-Optically Driven Sub-keV THz Gun

503

W.R. Huang, K.-H. Hong, F.X. Kärtner, E.A. Nanni, KR. Ravi
MIT, Cambridge, Massachusetts, USA
A-L. Calendron, H. Cankaya, A. Fallahi, F.X. Kärtner, X. Wu
CFEL, Hamburg, Germany
D. Zhang
DESY, Hamburg, Germany

Funding: European Research Council under the European Union Seventh Framework Program (FP/2007-2013)/ERC Grant Agreement no. 609920
Intense ultrashort THz and optical pulses with single-cycle pulse duration became possible after the recent advances in ultrafast technologies. Using such ultrashort pulses for electron acceleration offers advantages in terms of higher thresholds for material breakdown which opens up a promising path towards increased acceleration gradients. In addition, using optically generated THz pulses enable inherently synchronized acceleration schemes, since accelerating field and particle injecting field are excited by a single seed laser. In this contribution, we present the first experimental demonstration of laser-driven THz acceleration of electrons initially at rest. It is shown that strong-field, single-cycle THz fields accelerate electrons with peak energies of up to 0.8 keV in an ultracompact THz gun with bunch charge of 40 fC. The achieved energy spreads are as low as 5.8%.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPIK004

Export •

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

MOPAB150

Imaging the Spatial Modulation of a Relativistic Electron Beam

480

C. Zhang, W.S. Graves, L.E. Malin, J. Spence
Arizona State University, Tempe, USA
D.B. Cesar, J.M. Maxson, P. Musumeci, A. Urbanowicz
UCLA, Los Angeles, USA
C. Limborg, E.A. Nanni
SLAC, Menlo Park, California, USA

Funding: Work supported by NSF awards 1632780, 1415583, 1231306 and DOE award de-sc0009914
We describe Bragg diffraction of relativistic electron beams through a patterned Si crystal consisting of alternating thick and thin strips to produce nanometer scale electron density modulations. Multi-slice simulations show that a two-beam situation can be set up where, for a particular thickness of Si, nearly 100% of the electron beam is diffracted. Plans are underway to carry out experiments showing this effect in UCLA's ultrafast electron microscopy lab with 3.5 MeV electrons. We will select either the diffracted beam or the primary beam with a small aperture in the diffraction plane of a magnetic lens, and so record either the dark or bright field magnified image of the strips. Our first goal is to observe the nanopatterned beam at the image plane. We will then investigate various crystal thickness and sample orientations to maximize the contrast in the pattern and explore tuning the period of the modulation through varying magnification.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPAB150

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

TUPAB139

Design of an X-Band Photoinjector Operating at 1 kHz

1659

W.S. Graves, A.C. Goodrich, M.R. Holl, N.J. O'Brien
Arizona State University, Tempe, USA
V. Bharadwaj, P. Borchard
Tibaray Inc., Stanford, USA
V.A. Dolgashev, E.A. Nanni
SLAC, Menlo Park, California, USA

A kHz repetition rate RF photoinjector with novel features has been designed for the ASU CXLS project. The photoinjector consists of a 9.3 GHz 4.5 cell standing-wave RF cavity that is constructed from 2 halves. The halves are brazed together, with the braze joint bisecting the irises and cells, greatly simplifying its construction. The cathode is brazed onto this assembly. RF power is coupled into the cavity through inline circular waveguide using a demountable TM01 mode launcher. The mode launcher feeds the power through 4 ports distributed azimuthally to eliminate both dipole and quadrupole field distortions. The brazed-in cathode and absence of complex power coupler result in a very inexpensive yet high performance device. The clean design allows the RF cavity to sit entirely within the solenoid assembly. The cathode gradient is 120 MV/m at 3 MW of input power. The cathode cell is just 0.17 RF wavelength so that laser arrival phase for peak acceleration is 70 degrees from zero crossing resulting in exit energy of 4 MeV. The photoinjector will operate with 1μs pulses at 1 kHz, dissipating 3 kW of heat. Details of the design are presented.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-TUPAB139

Export •

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

WEPAB138

Prototyping High-Gradient mm-Wave Accelerating Structures

2902

E.A. Nanni, V.A. Dolgashev, A.A. Haase, J. Neilson, S.G. Tantawi
SLAC, Menlo Park, California, USA
S.C. Schaub
MIT, Cambridge, Massachusetts, USA
B. Spataro
INFN/LNF, Frascati (Roma), Italy
R.J. Temkin
MIT/PSFC, Cambridge, Massachusetts, USA

We present single-cell accelerating structures designed 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 are pi-mode standing-wave cavities fed with a TM01 circular waveguide. The structures are fabricated using precision milling out of two metal blocks, and the blocks are joined with diffusion bonding and brazing. The impact of fabrication and joining techniques on the cell geometry and RF performance will be discussed. First prototypes had a measured Qo of 2800, approaching the theoretical design value of 3300. The geometry of these accelerating structures are 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 with short pulses from a MW gyrotron oscillator. RF power of 1 MW may allow us to reach an accelerating gradient of 400 MeV/m.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPAB138

Export •

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

THPAB079

Terahertz Chirper for the Bunch Compression of Ultra-Low Emittance Beams

3899

A.R. Vrielink, A. Marinelli, E.A. Nanni
SLAC, Menlo Park, California, USA

Recent efforts have demonstrated the possibility of achieving ultralow transverse emittance beams for high brightness light sources and free electron lasers*. While these lower emittances should translate to improved lasing efficiency and higher peak brightness in FELs, these beams are commensurately more vulnerable to coherent synchrotron radiation (CSR) for the selfsame reasons. Conserving these ultralow emittances through the bunch compressors in an FEL given their increased propensity to emit CSR is particularly challenging. We investigate the possibility of imposing a large energy chirp at terahertz wavelengths to reduce the required magnetic fields in the compressor, counteracting the ultralow emittance in the generation of CSR. A second, higher frequency THz chirper would then be used to dechirp the beam after the chicane. Operation at THz as opposed to conventional radiofrequencies offers significantly larger chirp at similar input powers, yet still with wavelengths greater than typical FEL bunch lengths (several femtoseconds). Potential experimental schemes will be suggested in the context of LCLS and their feasibility evaluated.
* S. Bettoni, M. Pedrozzi and S. Reiche, Phys. Rev. ST Accel. Beams. 18, 123403 (December, 2015).

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPAB079

Export •

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

THPAB088

Comparison of Theory, Simulation, and Experiment for Dynamical Extinction of Relativistic Electron Beams Diffracted Through a Si Crystal Membrane

3924

SUSPSIK064

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

L.E. Malin, W.S. Graves, J. Spence, C. Zhang
Arizona State University, Tempe, USA
R.K. Li, C. Limborg, E.A. Nanni, X. Shen, S.P. Weathersby
SLAC, Menlo Park, California, USA

Diffraction in the transmission geometry through a single-crystal silicon slab is exploited to control the intensity of a relativistic electron beam. The choice of crystal thickness and incidence angle can extinguish or maximize the transmitted beam intensity via coherent multiple Bragg scattering; thus, the crystal acts as a dynamical beam stop through the Pendel'sung effect, a well-known phenomenon in X-ray and electron diffraction. In an initial experiment, we have measured the ability of this method to transmit or extinguish the primary beam and diffract into a single Bragg peak. Using lithographic etching of patterns in the crystal we intend to use this method to nanopattern an electron beam for production of coherent x-rays. We compare the experimental results with simulations using the multislice method to model the diffraction pattern from a perfect silicon crystal of uniform thickness, considering multiple scattering, crystallographic orientation, temperature effects, and partial coherence from the momentum spread of the beam. The simulations are compared to data collected at the ASTA UED facility at SLAC for a 340 nm thick Si(100) wafer with a beam energy of 2.35 MeV.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPAB088

Export •

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

THPIK126

Design of a Field-Emission X-Band Gun Driven by Solid-State RF Source

4399

E.A. Nanni, V.A. Dolgashev, J. Neilson, S.G. Tantawi
SLAC, Menlo Park, California, USA
B.E. Carlsten, J.W. Lewellen, D.C. Nguyen
LANL, Los Alamos, New Mexico, USA
M. Othman
UCI, Irvine, California, USA

We present the design of a field-emission X-band gun designed to be powered using a solid-state RF source. The source of the electron beam is a field emission nano-tip array. The RF gun is intended to be a beam source for 1 MeV solid-state driven linac for deployment on a satellite to map magnetic fields in the magnetosphere. The gun has to satisfy strict requirements on both average and peak power consumption, as well as rapid turn on time. In order to achieve low power consumption, the RF gun operates at relatively low accelerating gradient of 2 MeV/m. The beam exit energy is ~20 keV for an RF power 1.5 kW. Each cell of the RF gun is separately powered by commercially available, GaN high electron mobility transistors. In proof of principle experiments we successfully powered a 9.3 GHz accelerating cavity with a 100 W transistor and a 1% duty cycle.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPIK126

Export •

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