IPAC2016 - List of Authors (Guetg, M.W.)

Paper	Title	Page
MOPOW040	High Efficiency, High Brightness X-ray Free Electron Lasers via Fresh Bunch Self-Seeding	805
	C. Emma, C. Pellegrini UCLA, Los Angeles, California, USA M.W. Guetg, A.A. Lutman, A. Marinelli, C. Pellegrini, J. Wu SLAC, Menlo Park, California, USA
	High efficiency, terawatt peak power X-ray Free Electron Lasers are a promising tool for enabling single molecule imaging and nonlinear science using X-rays. Increasing the efficiency of XFELs while achieving good longitudinal coherence can be achieved via self-seeding and undulator tapering. The efficiency of self-seeded XFELs is limited by two factors: the ratio of seed power to beam energy spread and the ratio of seed power to shot noise power. We present a method to overcome these limitations by producing a strong X-ray seed and amplifying it with a small energy spread beam. This is achieved by selectively suppressing lasing for part of the bunch in the SASE section. In this manner we can saturate with the seeding electrons and amplify the strong seed with 'fresh' electrons downstream of the monochromator. Simulations of this scenario are presented for two systems, an optimal superconducting undulator design and the LCLS. In the case of the LCLS we examine how betatron oscillations leading to selective suppression are induced by using the transverse wakefield of a parallel plate dechirper. We also discuss extending the selective suppression scheme to chirped electron bunches.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPOW040
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MOPOW044	Commissioning of the RadiaBeam / SLAC Dechirper	809
	M.W. Guetg, K.L.F. Bane, A. Brachmann, A.S. Fisher, Z. Huang, R.H. Iverson, P. Krejcik, A.A. Lutman, T.J. Maxwell, A. Novokhatski, G. Stupakov, J. Zemella, Z. Zhang SLAC, Menlo Park, California, USA M.A. Harrison, M. Ruelas RadiaBeam Systems, Santa Monica, California, USA J. Zemella DESY, Hamburg, Germany Z. Zhang TUB, Beijing, People's Republic of China
	We present results on the commissioning of the two-module RadiaBeam / SLAC dechirper system at LCLS. This is the first installation and measurement of a corrugated dechirper at high energy (4.4 - 13.3 GeV), short pulses (< 200 fs) and while observing its effect on an operational FEL. Both the transverse and longitudinal wakefields allow more flexible electron beam tailoring. We verify that, for a single module at a given gap, the strength of the longitudinal wake on axis and the dipole near the axis agree well with the theoretical values. Using direct longitudinal phase space mapping and X-ray FEL spectrum measurements we demonstrate the energy chirp control capabilities.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPOW044
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MOPOW045	Measurement of Advanced Dispersion-based Beam-tilt Correction	813
	M.W. Guetg, F.-J. Decker, Y. Ding, P. Emma, Z. Huang, T.J. Maxwell SLAC, Menlo Park, California, USA
	Funding: DOE contract \#DE-AC02-76SF00515 Free electron lasers in the X-ray regime require a good slice alignment along the electron bunch to achieve their best performance. A transverse beam slice shift reduces this alignment and spoils projected emittance and optics matching. Coherent synchrotron radiation, specifically for over-compression going through full compression, and transverse wakefields are major contributors to this. In the case of the large-bandwidth operation, with a strong energy chirp on the bunch, this misalignments furthermore reduce the spectral bandwidth of the FEL pulse. Well-defined manipulation of dispersion allows to compensate for this slice centroid shifts, therefore enhancing lasing power and in case of the large bandwidth mode, spectral bandwidth. This work shows the first application of this correction on an X-ray FEL resulting in increase in beam-power and bandwidth.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPOW045
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MOPOW046	RadiaBeam/SLAC Dechirper as a Passive Deflector	817
	A. Novokhatski, A. Brachmann, M. Dal Forno, V.A. Dolgashev, A.S. Fisher, M.W. Guetg, Z. Huang, R.H. Iverson, P. Krejcik, A.A. Lutman, T.J. Maxwell SLAC, Menlo Park, California, USA J. Zemella DESY, Hamburg, Germany
	Funding: This work was supported by Department of Energy Contract No. DE-AC02-76SF00515. We discuss the possibility of using the RadiBeam/SLAC dechirper recently installed at LCLS for measuring the bunch length of very short bunches, less than 1 fs perhaps as short as 100 atto second. When a bunch travels close to one of the jaws the particles of the bunch get a transverse kick depends upon the position of a particle in a bunch. The tail particles get more kick. The transverse force also gets a nonlinear dependence on the transverse position. The stretched bunch can be measured at the YAG screen that is 100 m downstream the dechirper. The most important aspect of this measurement is that that no synchronization is needed. The Green's function for the transverse kick was evaluated based on the precise wake field calculations of the dechirper corrugated structure. Using this function we can restore the longitudinal shape of the bunch. This may also help to see if a bunch has any micro-bunch structure. A. Noovokhatski "Wakefield potentials of corrugated structures",Phys. Rev. ST Accel. Beams 18, 104402 (2015)
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPOW046
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THPMY043	Collimation System Design for LCLS-II	3755
	M.W. Guetg, P. Emma, M. Santana-Leitner, J.J. Welch, F. Zhou SLAC, Menlo Park, California, USA
	Funding: DOE contract \#DE-AC02-76SF00515 The planned LCLS-II FEL has an average beam power of up to 1.2 MW and a repetition rate of up to 1 MHz, both of which entail serious challenges for beam halo collimation. This paper summarizes the efforts to assess the proposed collimation system. The undulator section is specifically focused on due to its high loss sensitivity (maximal 12 mW). This proceedings concentrate on field emissions of the gun. Different dark current distribution, linac configurations and simulation programs were used to increase assurance of the results. Filled phase-space tracking further supplemented an independent prove of the collimation system effectiveness and expands to include beam-halo originating from different sources than the gun.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPMY043
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Paper

Title

Page

High Efficiency, High Brightness X-ray Free Electron Lasers via Fresh Bunch Self-Seeding

805

C. Emma, C. Pellegrini
UCLA, Los Angeles, California, USA
M.W. Guetg, A.A. Lutman, A. Marinelli, C. Pellegrini, J. Wu
SLAC, Menlo Park, California, USA

High efficiency, terawatt peak power X-ray Free Electron Lasers are a promising tool for enabling single molecule imaging and nonlinear science using X-rays. Increasing the efficiency of XFELs while achieving good longitudinal coherence can be achieved via self-seeding and undulator tapering. The efficiency of self-seeded XFELs is limited by two factors: the ratio of seed power to beam energy spread and the ratio of seed power to shot noise power. We present a method to overcome these limitations by producing a strong X-ray seed and amplifying it with a small energy spread beam. This is achieved by selectively suppressing lasing for part of the bunch in the SASE section. In this manner we can saturate with the seeding electrons and amplify the strong seed with 'fresh' electrons downstream of the monochromator. Simulations of this scenario are presented for two systems, an optimal superconducting undulator design and the LCLS. In the case of the LCLS we examine how betatron oscillations leading to selective suppression are induced by using the transverse wakefield of a parallel plate dechirper. We also discuss extending the selective suppression scheme to chirped electron bunches.

DOI •

reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPOW040

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MOPOW044

Commissioning of the RadiaBeam / SLAC Dechirper

809

M.W. Guetg, K.L.F. Bane, A. Brachmann, A.S. Fisher, Z. Huang, R.H. Iverson, P. Krejcik, A.A. Lutman, T.J. Maxwell, A. Novokhatski, G. Stupakov, J. Zemella, Z. Zhang
SLAC, Menlo Park, California, USA
M.A. Harrison, M. Ruelas
RadiaBeam Systems, Santa Monica, California, USA
J. Zemella
DESY, Hamburg, Germany
Z. Zhang
TUB, Beijing, People's Republic of China

We present results on the commissioning of the two-module RadiaBeam / SLAC dechirper system at LCLS. This is the first installation and measurement of a corrugated dechirper at high energy (4.4 - 13.3 GeV), short pulses (< 200 fs) and while observing its effect on an operational FEL. Both the transverse and longitudinal wakefields allow more flexible electron beam tailoring. We verify that, for a single module at a given gap, the strength of the longitudinal wake on axis and the dipole near the axis agree well with the theoretical values. Using direct longitudinal phase space mapping and X-ray FEL spectrum measurements we demonstrate the energy chirp control capabilities.

DOI •

reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPOW044

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

MOPOW045

Measurement of Advanced Dispersion-based Beam-tilt Correction

813

M.W. Guetg, F.-J. Decker, Y. Ding, P. Emma, Z. Huang, T.J. Maxwell
SLAC, Menlo Park, California, USA

Funding: DOE contract \#DE-AC02-76SF00515
Free electron lasers in the X-ray regime require a good slice alignment along the electron bunch to achieve their best performance. A transverse beam slice shift reduces this alignment and spoils projected emittance and optics matching. Coherent synchrotron radiation, specifically for over-compression going through full compression, and transverse wakefields are major contributors to this. In the case of the large-bandwidth operation, with a strong energy chirp on the bunch, this misalignments furthermore reduce the spectral bandwidth of the FEL pulse. Well-defined manipulation of dispersion allows to compensate for this slice centroid shifts, therefore enhancing lasing power and in case of the large bandwidth mode, spectral bandwidth. This work shows the first application of this correction on an X-ray FEL resulting in increase in beam-power and bandwidth.

DOI •

reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPOW045

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MOPOW046

RadiaBeam/SLAC Dechirper as a Passive Deflector

817

A. Novokhatski, A. Brachmann, M. Dal Forno, V.A. Dolgashev, A.S. Fisher, M.W. Guetg, Z. Huang, R.H. Iverson, P. Krejcik, A.A. Lutman, T.J. Maxwell
SLAC, Menlo Park, California, USA
J. Zemella
DESY, Hamburg, Germany

Funding: This work was supported by Department of Energy Contract No. DE-AC02-76SF00515.
We discuss the possibility of using the RadiBeam/SLAC dechirper recently installed at LCLS for measuring the bunch length of very short bunches, less than 1 fs perhaps as short as 100 atto second. When a bunch travels close to one of the jaws the particles of the bunch get a transverse kick depends upon the position of a particle in a bunch. The tail particles get more kick. The transverse force also gets a nonlinear dependence on the transverse position. The stretched bunch can be measured at the YAG screen that is 100 m downstream the dechirper. The most important aspect of this measurement is that that no synchronization is needed. The Green's function for the transverse kick was evaluated based on the precise wake field calculations of the dechirper corrugated structure*. Using this function we can restore the longitudinal shape of the bunch. This may also help to see if a bunch has any micro-bunch structure.
* A. Noovokhatski "Wakefield potentials of corrugated structures",Phys. Rev. ST Accel. Beams 18, 104402 (2015)

DOI •

reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPOW046

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THPMY043

Collimation System Design for LCLS-II

3755

M.W. Guetg, P. Emma, M. Santana-Leitner, J.J. Welch, F. Zhou
SLAC, Menlo Park, California, USA

Funding: DOE contract \#DE-AC02-76SF00515
The planned LCLS-II FEL has an average beam power of up to 1.2 MW and a repetition rate of up to 1 MHz, both of which entail serious challenges for beam halo collimation. This paper summarizes the efforts to assess the proposed collimation system. The undulator section is specifically focused on due to its high loss sensitivity (maximal 12 mW). This proceedings concentrate on field emissions of the gun. Different dark current distribution, linac configurations and simulation programs were used to increase assurance of the results. Filled phase-space tracking further supplemented an independent prove of the collimation system effectiveness and expands to include beam-halo originating from different sources than the gun.

DOI •

reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPMY043

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