IPAC2015 - List of Authors (Wu, Z.)

Paper	Title	Page
TUPMA030	Narrowband Continuously Tunable Radiation in the 5 to 10 Terahertz Range by Inverse Compton Scattering	1901
	Z. Wu, K. Fang, M.-H. Wang, J. Wu SLAC, Menlo Park, California, USA
	Funding: Work supported by U.S. Department of Energy under Grants DE-AC02-76SF00515, DE-FG02-13ER41970 and by DARPA Grant N66001-11-1-4199. 5 to 10 THz has recently become the frontier of THz radiation sources development, pushed by the growing interests of spectroscopy and pump-probe material study in this frequency range. This spectrum “Gap” lies in between the several THz range covered by Electro-Optical crystal based THz generation, and the tens of THz range covered by the difference frequency generation method. The state-of-the-art EO crystal THz source using tilted pulse front technique has been able to reach ~ 100 MV/m peak field strength, large enough to be used in an inverse Compton scattering process to push these low energy photons to shorter wavelengths of the desired 5-10 THz range. The required electron beam energy is within 1~2 MeV, therefore a compact footprint of the whole system. The process would occur coherently granted the electron beam is bunched to a fraction of the radiation wavelengths (several microns). A system operating at KHz or even MHz repetition rate is possible given the low electron energy and thus low RF acceleration gradient required. This work will explore the scheme with design parameters and simulation results.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-TUPMA030
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TUPMA031	Dispersive Property of the Pulse Front Tilt of a Short Pulse Optical Undulator	1904
	M.-H. Wang, J. Wu, Z. Wu SLAC, Menlo Park, California, USA
	Funding: Work supported by the US DOE No. DE-AC02-76SF00515. A short pulse laser can be used as an optical undulator to achieve a high-gain and high-brightness X-ray free electron laser (FEL) [1]. To extend the interaction duration of electron and laser field, the electron and the laser will propagate toward each other with an small angle. In addition, to maintain the FEL lasing resonant condition, the laser pulse shape need be flattened and the pulse front will be titled. Due to the short pulse duration, the laser pulse has a broad bandwidth. In this paper, we will first describe the method of generalized Gaussian beam propagation using ray matrix. By applying the Gaussian beam ray matrix, we can study the dispersive property after the pulse front of the short laser is tilted. The results of the optics design for the proposal of SLAC Compton scattering FEL are shown as an example in this paper. [1] C. Chang, et al.,“High-brightness X-ray free-electron laser with an optical undulator by pulse shaping”. Optics Express, Vol. 21, Issue 26, pp. 32013-32018 (2013).
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-TUPMA031
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WEPWA053	First Acceleration in a Resonant Optical-Scale Laser-Powered Structure	2624
	R.B. Yoder Goucher College, Baltimore, Maryland, USA R.J. England, Z. Wu SLAC, Menlo Park, California, USA K.S. Hazra, B. Matthews, J.C. McNeur, E.B. Sozer, G. Travish UCLA, Los Angeles, California, USA E.A. Peralta, K. Soong Stanford University, Stanford, California, USA
	Funding: U.S. DTRA grant HDTRA1-09-1-0043 The Micro-Accelerator Platform (MAP), an optical-scale dielectric laser accelerator (DLA) based on a planar resonant structure that was developed at UCLA, has been tested experimentally. Successful acceleration was observed after a series of experimental runs at SLAC’s NLCTA facility, in which the input laser power was well below the predicted breakdown limit. Though acceleration gradients were modest (<50 MeV/m), these are the first proof-of-principle results for a resonant DLA structure. We present more detailed results and some implications for future work.
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WEPJE012	Design and Optimisation of Dielectric Laser Deflecting Structures	2698
	K.P. Wootton, R.J. England, I.V. Makasyuk, Z. Wu SLAC, Menlo Park, California, USA R.L. Byer, E.A. Peralta Stanford University, Stanford, California, USA A.D. Tafel Friedrich-Alexander Universität Erlangen-Nuernberg, University Erlangen-Nuernberg LFTE, Erlangen, Germany
	Funding: This work was supported by the U.S. Department of Energy under Grants DE-AC02-76SF00515, and DE-FG02-13ER41970. Recent experimental demonstrations of dielectric laser-driven accelerator structures offer a path to the miniaturisation of accelerators. In order to accelerate particles to higher energies using a staged sequence of accelerating structures, integrating compatible micrometre-scale transverse deflecting structures into these accelerators is necessary. Using simulations, the present work outlines the design and optimisation of a fused-silica laser-driven grating deflecting structure for relativistic electron beams. Implications for device fabrication and experiments are outlined.
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WEPJE013	A New Accelerating Mode in a Silicon Woodpile Structure and Its High-efficiency Power Coupler Design	2702
	Z. Wu, R.J. England, C. Lee, C.-K. Ng, K.P. Wootton SLAC, Menlo Park, California, USA
	Funding: Work supported by U.S. Department of Energy under Grants DE-AC02-76SF00515, DE-FG02-13ER41970 and by DARPA Grant N66001-11-1-4199. Silicon woodpile photonic crystals provide a base structure that can be used to build a three-dimensional dielectric waveguide system for high-gradient laser-driven acceleration. A new woodpile waveguide design that hosts a phase synchronous, centrally confined accelerating mode with ideal Gaussian transverse profile is proposed. Comparing with previously discovered silicon woodpile accelerating modes, this mode shows advantages in better beam loading and higher achievable acceleration gradient. Several travelling-wave coupler design schemes developed for multi-cell RF cavity accelerators are adapted to the woodpile accelerator coupler design based on this new accelerating mode. A forward-wave-coupled, highly efficient silicon woodpile accelerator is achieved. Simulation shows high efficiency of over 70% of the drive laser power coupled to this fundamental woodpile accelerating mode, with less than 15% backward wave excitation. The estimated acceleration gradient, when the coupler structure is driven at the damage threshold fluence of silicon at its operating 1.506 um wavelength, can reach roughly 185 MV/m.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPJE013
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WEPJE021	Fabrication and Demonstration of a Silicon Buried Grating Accelerator	2717
	A.C. Ceballos, R.L. Byer, K.J. Leedle, E.A. Peralta, O. Solgaard, K. Soong Stanford University, Stanford, California, USA R.J. England, I.V. Makasyuk, K.P. Wootton, Z. Wu SLAC, Menlo Park, California, USA A. Hanuka Technion, Haifa, Israel A.D. Tafel Friedrich-Alexander Universität Erlangen-Nuernberg, University Erlangen-Nuernberg LFTE, Erlangen, Germany
	Funding: Work supported by the U.S. Department of Energy under Grants DE-AC02-76SF00515, DE-FG06-97ER41276. Using optical electromagnetic fields in dielectric microstructures, we can realize higher-energy accelerator systems in a more compact, low-cost form than the current state-of-the-art. Dielectric, laser-driven accelerators (DLA) have recently been demonstrated using fused silica structures to achieve about an order-of-magnitude increase in accelerating gradient over conventional RF structures.* We leverage higher damage thresholds of silicon over metals and extensive micromachining capability to fabricate structures capable of electron acceleration. Our monolithic structure, the buried grating, consists of a grating formed on either side of a long channel via a deep reactive ion etch (DRIE).** The grating imposes a phase profile on an incoming laser pulse such that an electron experiences a net change in energy over the course of each optical cycle. This results in acceleration (or deceleration) as electrons travel down the channel. We have designed and fabricated such structures and begun testing at the SLAC National Accelerator Laboratory. We report on the progress toward demonstration of acceleration in these structures driven at 2um wavelength. * E.A. Peralta et al., Nature 503 (2013) ** C.M. Chang and O. Solgaard, Appl. Phys. Lett. 104 (2014)
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPJE021
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Paper

Title

Page

Narrowband Continuously Tunable Radiation in the 5 to 10 Terahertz Range by Inverse Compton Scattering

1901

Z. Wu, K. Fang, M.-H. Wang, J. Wu
SLAC, Menlo Park, California, USA

Funding: Work supported by U.S. Department of Energy under Grants DE-AC02-76SF00515, DE-FG02-13ER41970 and by DARPA Grant N66001-11-1-4199.
5 to 10 THz has recently become the frontier of THz radiation sources development, pushed by the growing interests of spectroscopy and pump-probe material study in this frequency range. This spectrum “Gap” lies in between the several THz range covered by Electro-Optical crystal based THz generation, and the tens of THz range covered by the difference frequency generation method. The state-of-the-art EO crystal THz source using tilted pulse front technique has been able to reach ~ 100 MV/m peak field strength, large enough to be used in an inverse Compton scattering process to push these low energy photons to shorter wavelengths of the desired 5-10 THz range. The required electron beam energy is within 1~2 MeV, therefore a compact footprint of the whole system. The process would occur coherently granted the electron beam is bunched to a fraction of the radiation wavelengths (several microns). A system operating at KHz or even MHz repetition rate is possible given the low electron energy and thus low RF acceleration gradient required. This work will explore the scheme with design parameters and simulation results.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-TUPMA030

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TUPMA031

Dispersive Property of the Pulse Front Tilt of a Short Pulse Optical Undulator

1904

M.-H. Wang, J. Wu, Z. Wu
SLAC, Menlo Park, California, USA

Funding: Work supported by the US DOE No. DE-AC02-76SF00515.
A short pulse laser can be used as an optical undulator to achieve a high-gain and high-brightness X-ray free electron laser (FEL) [1]. To extend the interaction duration of electron and laser field, the electron and the laser will propagate toward each other with an small angle. In addition, to maintain the FEL lasing resonant condition, the laser pulse shape need be flattened and the pulse front will be titled. Due to the short pulse duration, the laser pulse has a broad bandwidth. In this paper, we will first describe the method of generalized Gaussian beam propagation using ray matrix. By applying the Gaussian beam ray matrix, we can study the dispersive property after the pulse front of the short laser is tilted. The results of the optics design for the proposal of SLAC Compton scattering FEL are shown as an example in this paper.
[1] C. Chang, et al.,“High-brightness X-ray free-electron laser with an optical undulator by pulse shaping”. Optics Express, Vol. 21, Issue 26, pp. 32013-32018 (2013).

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-TUPMA031

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WEPWA053

First Acceleration in a Resonant Optical-Scale Laser-Powered Structure

2624

R.B. Yoder
Goucher College, Baltimore, Maryland, USA
R.J. England, Z. Wu
SLAC, Menlo Park, California, USA
K.S. Hazra, B. Matthews, J.C. McNeur, E.B. Sozer, G. Travish
UCLA, Los Angeles, California, USA
E.A. Peralta, K. Soong
Stanford University, Stanford, California, USA

Funding: U.S. DTRA grant HDTRA1-09-1-0043
The Micro-Accelerator Platform (MAP), an optical-scale dielectric laser accelerator (DLA) based on a planar resonant structure that was developed at UCLA, has been tested experimentally. Successful acceleration was observed after a series of experimental runs at SLAC’s NLCTA facility, in which the input laser power was well below the predicted breakdown limit. Though acceleration gradients were modest (<50 MeV/m), these are the first proof-of-principle results for a resonant DLA structure. We present more detailed results and some implications for future work.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPWA053

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WEPJE012

Design and Optimisation of Dielectric Laser Deflecting Structures

2698

K.P. Wootton, R.J. England, I.V. Makasyuk, Z. Wu
SLAC, Menlo Park, California, USA
R.L. Byer, E.A. Peralta
Stanford University, Stanford, California, USA
A.D. Tafel
Friedrich-Alexander Universität Erlangen-Nuernberg, University Erlangen-Nuernberg LFTE, Erlangen, Germany

Funding: This work was supported by the U.S. Department of Energy under Grants DE-AC02-76SF00515, and DE-FG02-13ER41970.
Recent experimental demonstrations of dielectric laser-driven accelerator structures offer a path to the miniaturisation of accelerators. In order to accelerate particles to higher energies using a staged sequence of accelerating structures, integrating compatible micrometre-scale transverse deflecting structures into these accelerators is necessary. Using simulations, the present work outlines the design and optimisation of a fused-silica laser-driven grating deflecting structure for relativistic electron beams. Implications for device fabrication and experiments are outlined.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPJE012

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WEPJE013

A New Accelerating Mode in a Silicon Woodpile Structure and Its High-efficiency Power Coupler Design

2702

Z. Wu, R.J. England, C. Lee, C.-K. Ng, K.P. Wootton
SLAC, Menlo Park, California, USA

Funding: Work supported by U.S. Department of Energy under Grants DE-AC02-76SF00515, DE-FG02-13ER41970 and by DARPA Grant N66001-11-1-4199.
Silicon woodpile photonic crystals provide a base structure that can be used to build a three-dimensional dielectric waveguide system for high-gradient laser-driven acceleration. A new woodpile waveguide design that hosts a phase synchronous, centrally confined accelerating mode with ideal Gaussian transverse profile is proposed. Comparing with previously discovered silicon woodpile accelerating modes, this mode shows advantages in better beam loading and higher achievable acceleration gradient. Several travelling-wave coupler design schemes developed for multi-cell RF cavity accelerators are adapted to the woodpile accelerator coupler design based on this new accelerating mode. A forward-wave-coupled, highly efficient silicon woodpile accelerator is achieved. Simulation shows high efficiency of over 70% of the drive laser power coupled to this fundamental woodpile accelerating mode, with less than 15% backward wave excitation. The estimated acceleration gradient, when the coupler structure is driven at the damage threshold fluence of silicon at its operating 1.506 um wavelength, can reach roughly 185 MV/m.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPJE013

Export •

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

WEPJE021

Fabrication and Demonstration of a Silicon Buried Grating Accelerator

2717

A.C. Ceballos, R.L. Byer, K.J. Leedle, E.A. Peralta, O. Solgaard, K. Soong
Stanford University, Stanford, California, USA
R.J. England, I.V. Makasyuk, K.P. Wootton, Z. Wu
SLAC, Menlo Park, California, USA
A. Hanuka
Technion, Haifa, Israel
A.D. Tafel
Friedrich-Alexander Universität Erlangen-Nuernberg, University Erlangen-Nuernberg LFTE, Erlangen, Germany

Funding: Work supported by the U.S. Department of Energy under Grants DE-AC02-76SF00515, DE-FG06-97ER41276.
Using optical electromagnetic fields in dielectric microstructures, we can realize higher-energy accelerator systems in a more compact, low-cost form than the current state-of-the-art. Dielectric, laser-driven accelerators (DLA) have recently been demonstrated using fused silica structures to achieve about an order-of-magnitude increase in accelerating gradient over conventional RF structures.* We leverage higher damage thresholds of silicon over metals and extensive micromachining capability to fabricate structures capable of electron acceleration. Our monolithic structure, the buried grating, consists of a grating formed on either side of a long channel via a deep reactive ion etch (DRIE).** The grating imposes a phase profile on an incoming laser pulse such that an electron experiences a net change in energy over the course of each optical cycle. This results in acceleration (or deceleration) as electrons travel down the channel. We have designed and fabricated such structures and begun testing at the SLAC National Accelerator Laboratory. We report on the progress toward demonstration of acceleration in these structures driven at 2um wavelength.
* E.A. Peralta et al., Nature 503 (2013)
** C.M. Chang and O. Solgaard, Appl. Phys. Lett. 104 (2014)

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPJE021

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