LINAC2014 - List of Keywords (wakefield)

Paper	Title	Other Keywords	Page
MOIOB03	Generation and Acceleration of Low-Emittance, High-Current Electron Beams for SuperKEKB	emittance, gun, laser, electron	21
	M. Yoshida, N. Iida, S. Kazama, T. Natsui, Y. Ogawa, S. Ohsawa, L. Zang, X. Zhou KEK, Ibaraki, Japan
	KEK e⁻/e⁺ linac is now in a final stage of upgrade for SuperKEKB. One of the key issues is to stably generate and accelerate a low-emittance, high charge electron beam for SuperKEKB (a couple of single-bunched beams with a charge of 5 nC and a normalized emittance of 20 mm-mmrad each).
	Slides MOIOB03 [3.981 MB]

MOPP030	CALIFES: A Multi-Purpose Electron Beam for Accelerator Technology Tests	electron, acceleration, quadrupole, laser	121
	J.L. Navarro Quirante, R. Corsini, W. Farabolini, D. Gamba, A. Grudiev, M.A. Khan, T. Lefèvre, S. Mazzoni, R. Pan, F. Peauger, F. Tecker, N. Vitoratou, K. Yaqub CERN, Geneva, Switzerland W. Farabolini, F. Peauger CEA/DSM/IRFU, France D. Gamba JAI, Oxford, United Kingdom M.A. Khan, K. Yaqub PINSTECH, Islamabad, Pakistan J. Ögren, R.J.M.Y. Ruber Uppsala University, Uppsala, Sweden N. Vitoratou Thessaloniki University, Thessaloniki, Greece
	The Compact Linear Collider (CLIC) project aims to accelerate and collide electrons and positrons up to 3 TeV center-of-mass energy using a novel two-beam acceleration concept. To prove the feasibility of this technology the CLIC Test Facility CTF3 has been operated during the last years. CALIFES (Concept d’Accélérateur Linéaire pour Faisceau d’Electron Sonde) is an electron linac hosted in the CTF3 complex, which provides a flexible electron beam and the necessary equipment to probe both the two-beam acceleration concept and novel instrumentation to be used in the future CLIC collider. In this paper we describe the CALIFES Linac and its beam characteristics, present recent test results, outline its future program on two-beam module testing and finally discuss about possible future applications as a multi-purpose accelerator technology test facility.

MOPP127	Wakefield Effects of the Bypass Line in LCLS-II	dipole, undulator, operation, acceleration	355
	K.L.F. Bane, T.O. Raubenheimer SLAC, Menlo Park, California, USA
	Funding: Work supported by Department of Energy contract DE–AC02–76SF00515. In LCLS-II, after acceleration and compression and just before entering the undulator, the beam passes through roughly 2.5 km of 24.5 mm (radius) stainless steel pipe. The bunch that passes through the pipe is extremely short with an rms of 8 um for the nominal 100 pC case. Thus, even though the pipe has a large aperture, the wake that applies is the short-range resistive wall wakefield. It turns out that the wake supplies needed dechirping to the LCLS-II beam before it enters the undulator. The LCLS-II bunch distribution is approximately uniform, and therefore the wake induced voltage is characterized by a rather linear voltage chirp for short bunches. However for bunches longer than 25 um (300 pC at 1 kA) the wake starts to become nonlinear, effectively limiting the maximum charge with which the LCLS-II can operate. In this note we calculate the wake, discuss the confidence in the calculation, and investigate how to improve the induced chirp linearity and/or strength. Finally, we also study the strength and effects of the transverse (dipole) resistive wall wakefield.

TUPP072	Studies on Wake Field in Annular Coupled Structure	impedance, cavity, linac, acceleration	593
	Y. Liu, T. Maruta KEK/JAEA, Ibaraki-Ken, Japan K. Futatsukawa KEK, Ibaraki, Japan A. Miura JAEA/J-PARC, Tokai-mura, Japan
	LINAC injector of J-PARC (Japan Proton Accelerator Research Complex) was recently successfully upgraded from 181 MeV to 400 MeV, applying a type of coupled cavity linac (CCL) structure ACS (Annular Coupled Structure). It was warmly discussed since very beginning on the wake field in the ACS cavities, where there are CCL modes with the same number as that of cells within ~50 MHz, possibly resonating with high intensity proton/H⁻ beams. One of the most important effects from the wake field is the influence on the ACS phase scan. Analytical and simulation studies, as well as the countermeasures were prepared before the energy upgrade. Fortunately we found that detuning of the ACS was unnecessary, which helped to save much work in the commissioning. In addition we got chance to make experiment studies. It was also discussed why the wake field is not so serious as we expected at the very beginning.

TUPP122	Roughness Tolerances in the Undulator Vacuum Chamber of LCLS-II	impedance, undulator, vacuum, FEL	708
	K.L.F. Bane, G.V. Stupakov SLAC, Menlo Park, California, USA
	Funding: Work supported by Department of Energy contract DE–AC02–76SF00515. In LCLS-II, after acceleration and compression and just before entering the undulator, the beam passes through roughly 2.5 km of 24.5 mm (radius) stainless steel pipe. The bunch that passes through the pipe is extremely short with an rms of 8 um for the nominal 100 pC case. Thus, even though the pipe has a large aperture, the wake that applies is the short-range resistive wall wakefield. It turns out that the wake supplies needed dechirping to the LCLS-II beam before it enters the undulator. The LCLS-II bunch distribution is approximately uniform, and therefore the wake induced voltage is characterized by a rather linear voltage chirp for short bunches. However for bunches longer than 25 um (300 pC at 1 kA) the wake starts to become nonlinear, effectively limiting the maximum charge with which the LCLS-II can operate. In this note we calculate the wake, discuss the confidence in the calculation, and investigate how to improve the induced chirp linearity and/or strength. Finally, we also study the strength and effects of the transverse (dipole) resistive wall wakefield.

TUPP127	R&D of X-band Accelerating Structure for Compact XFEL at SINAP	FEL, linac, simulation, radiation	715
	W. Fang, Q. Gu, M. Zhang, Z.T. Zhao SINAP, Shanghai, People's Republic of China A.A. Aksoy, O. Yavaş Ankara University, Accelerator Technologies Institute, Golbasi / Ankara, Turkey D. Angal-Kalinin, J.A. Clarke Cockcroft Institute, Warrington, Cheshire, United Kingdom C.J. Bocchetta, A.I. Wawrzyniak Solaris, Kraków, Poland M.J. Boland SLSA, Clayton, Australia G. D'Auria, S. Di Mitri, C. Serpico Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy T.J.C. Ekelöf, R.J.M.Y. Ruber, V.G. Ziemann Uppsala University, Uppsala, Sweden E.N. Gazis National Technical University of Athens, Athens, Greece A. Grudiev, A. Latina, D. Schulte, S. Stapnes, W. Wuensch CERN, Geneva, Switzerland
	One compact hard X-ray FEL facility is being planned at SINAP, and X-band high gradient accelerating structure is the most competetive scheme for this plan. X-band accelerating structure is designed to switch between 60MV/m and 80MV/m, and carries out 6GeV and 8GeV by 130 meters linac respectively. In this paper, brief layout of compact XFEL will be introduced, and in particular the prototype design of dedicated X-band acceleration RF system is also presented.

TUPP140	Observation of >GV/m Decelerating Fields in Dielectric Lined Waveguides	radiation, vacuum, experiment, electron	743
	B.D. O'Shea, G. Andonian, K.L. Fitzmorris, S. Hakimi, J. Harrison, J.B. Rosenzweig, O. Williams UCLA, Los Angeles, California, USA M.J. Hogan, V. Yakimenko SLAC, Menlo Park, California, USA
	Recent experimental measurements of the energy lost to wakefields in a dielectric lined waveguide are presented. These measurements demonstrate average decelerating gradients on the order of >1 GV/m, for two different structures. The measurements were made at the Facility for Advanced aCcelerator Experimental Tests (FACET) at SLAC National Laboratory using sub-millimeter diameter fifteen-centimeter long quartz fibers of annular cross section. The unique extremely short, high charge, ultra relativistic beam at FACET (200 fs, 3 nC, 20 GeV) allows the use of dielectric wakefield structures of unprecedented size and length. In addition to experimental results, we support conclusions with simulation and theoretical work. This measurement builds on a large body of work previously performed using dielectric wakefield structures in an effort to provide high gradient accelerating structures for tomorrows linear colliders.

THPP034	Toolbox for Applying Beam-Based Alignment to Linacs	linac, emittance, interface, controls	916
	A. Latina, D. Pellegrini, J. Pfingstner, D. Schulte CERN, Geneva, Switzerland E. Adli University of Oslo, Oslo, Norway
	Tests of Beam-Based Alignment have been performed at FACET, at SLAC in the USA, and at Fermi, at Elettra in Trieste, Italy, with very promising results. Dispersion-Free Steering and Wakefield-free steering have been successfully applied to both machines. In order to make the correction process as automatic as possible, a set of robust tools has been developed, which allowed to span a large set of parameters. These tools and some of the experimental results performed at both machines are presented in this paper.

THPP124	Wakefields in the Superconducting RF Cavities of LCLS-II	cavity, linac, electron, niobium	1147
	K.L.F. Bane, T.O. Raubenheimer SLAC, Menlo Park, California, USA A. Romanenko, V.P. Yakovlev Fermilab, Batavia, Illinois, USA
	Funding: Work supported by Department of Energy contract DE–AC02–76SF00515. The superconducting cavities in the linacs of LCLS-II are designed to operate at 2K, where cooling costs are very expensive. In addition to an unavoidable static load and the dynamic load of the fundamental 1.3 GHz accelerating rf, there will be higher order mode (HOM) power deposited by the beam. Due to the very short bunch length the LCLS-II beam spectrum extends into the THz range. Ceramic absorbers, cooled to 70K and located between cryomodules, are meant to absorb much of this power; understanding their effectiveness, however, is a challenging task. In this report we calculate the amount of power radiated by the beam in the different portions of the linac as the bunch length is changed by the bunch compressors. We consider both the steady state radiation as well as transients that arise at the beginning of the linac structures. In addition, transitions due to changes in the vacuum chamber aperture at the ends of the linacs are also considered. Finally, under the assumption that all the wake power ends up in the SRF cavity walls, we estimate the wall heating and the possibility of breaking the Cooper pairs and quenching the cavities.

Paper

Title

Other Keywords

Page

MOIOB03

Generation and Acceleration of Low-Emittance, High-Current Electron Beams for SuperKEKB

emittance, gun, laser, electron

21

M. Yoshida, N. Iida, S. Kazama, T. Natsui, Y. Ogawa, S. Ohsawa, L. Zang, X. Zhou
KEK, Ibaraki, Japan

KEK e⁻/e⁺ linac is now in a final stage of upgrade for SuperKEKB. One of the key issues is to stably generate and accelerate a low-emittance, high charge electron beam for SuperKEKB (a couple of single-bunched beams with a charge of 5 nC and a normalized emittance of 20 mm-mmrad each).

Slides MOIOB03 [3.981 MB]

MOPP030

CALIFES: A Multi-Purpose Electron Beam for Accelerator Technology Tests

electron, acceleration, quadrupole, laser

121

J.L. Navarro Quirante, R. Corsini, W. Farabolini, D. Gamba, A. Grudiev, M.A. Khan, T. Lefèvre, S. Mazzoni, R. Pan, F. Peauger, F. Tecker, N. Vitoratou, K. Yaqub
CERN, Geneva, Switzerland
W. Farabolini, F. Peauger
CEA/DSM/IRFU, France
D. Gamba
JAI, Oxford, United Kingdom
M.A. Khan, K. Yaqub
PINSTECH, Islamabad, Pakistan
J. Ögren, R.J.M.Y. Ruber
Uppsala University, Uppsala, Sweden
N. Vitoratou
Thessaloniki University, Thessaloniki, Greece

The Compact Linear Collider (CLIC) project aims to accelerate and collide electrons and positrons up to 3 TeV center-of-mass energy using a novel two-beam acceleration concept. To prove the feasibility of this technology the CLIC Test Facility CTF3 has been operated during the last years. CALIFES (Concept d’Accélérateur Linéaire pour Faisceau d’Electron Sonde) is an electron linac hosted in the CTF3 complex, which provides a flexible electron beam and the necessary equipment to probe both the two-beam acceleration concept and novel instrumentation to be used in the future CLIC collider. In this paper we describe the CALIFES Linac and its beam characteristics, present recent test results, outline its future program on two-beam module testing and finally discuss about possible future applications as a multi-purpose accelerator technology test facility.

MOPP127

Wakefield Effects of the Bypass Line in LCLS-II

dipole, undulator, operation, acceleration

355

K.L.F. Bane, T.O. Raubenheimer
SLAC, Menlo Park, California, USA

Funding: Work supported by Department of Energy contract DE–AC02–76SF00515.
In LCLS-II, after acceleration and compression and just before entering the undulator, the beam passes through roughly 2.5 km of 24.5 mm (radius) stainless steel pipe. The bunch that passes through the pipe is extremely short with an rms of 8 um for the nominal 100 pC case. Thus, even though the pipe has a large aperture, the wake that applies is the short-range resistive wall wakefield. It turns out that the wake supplies needed dechirping to the LCLS-II beam before it enters the undulator. The LCLS-II bunch distribution is approximately uniform, and therefore the wake induced voltage is characterized by a rather linear voltage chirp for short bunches. However for bunches longer than 25 um (300 pC at 1 kA) the wake starts to become nonlinear, effectively limiting the maximum charge with which the LCLS-II can operate. In this note we calculate the wake, discuss the confidence in the calculation, and investigate how to improve the induced chirp linearity and/or strength. Finally, we also study the strength and effects of the transverse (dipole) resistive wall wakefield.

TUPP072

Studies on Wake Field in Annular Coupled Structure

impedance, cavity, linac, acceleration

593

Y. Liu, T. Maruta
KEK/JAEA, Ibaraki-Ken, Japan
K. Futatsukawa
KEK, Ibaraki, Japan
A. Miura
JAEA/J-PARC, Tokai-mura, Japan

LINAC injector of J-PARC (Japan Proton Accelerator Research Complex) was recently successfully upgraded from 181 MeV to 400 MeV, applying a type of coupled cavity linac (CCL) structure ACS (Annular Coupled Structure). It was warmly discussed since very beginning on the wake field in the ACS cavities, where there are CCL modes with the same number as that of cells within ~50 MHz, possibly resonating with high intensity proton/H⁻ beams. One of the most important effects from the wake field is the influence on the ACS phase scan. Analytical and simulation studies, as well as the countermeasures were prepared before the energy upgrade. Fortunately we found that detuning of the ACS was unnecessary, which helped to save much work in the commissioning. In addition we got chance to make experiment studies. It was also discussed why the wake field is not so serious as we expected at the very beginning.

TUPP122

Roughness Tolerances in the Undulator Vacuum Chamber of LCLS-II

impedance, undulator, vacuum, FEL

708

K.L.F. Bane, G.V. Stupakov
SLAC, Menlo Park, California, USA

Funding: Work supported by Department of Energy contract DE–AC02–76SF00515.
In LCLS-II, after acceleration and compression and just before entering the undulator, the beam passes through roughly 2.5 km of 24.5 mm (radius) stainless steel pipe. The bunch that passes through the pipe is extremely short with an rms of 8 um for the nominal 100 pC case. Thus, even though the pipe has a large aperture, the wake that applies is the short-range resistive wall wakefield. It turns out that the wake supplies needed dechirping to the LCLS-II beam before it enters the undulator. The LCLS-II bunch distribution is approximately uniform, and therefore the wake induced voltage is characterized by a rather linear voltage chirp for short bunches. However for bunches longer than 25 um (300 pC at 1 kA) the wake starts to become nonlinear, effectively limiting the maximum charge with which the LCLS-II can operate. In this note we calculate the wake, discuss the confidence in the calculation, and investigate how to improve the induced chirp linearity and/or strength. Finally, we also study the strength and effects of the transverse (dipole) resistive wall wakefield.

TUPP127

R&D of X-band Accelerating Structure for Compact XFEL at SINAP

FEL, linac, simulation, radiation

715

W. Fang, Q. Gu, M. Zhang, Z.T. Zhao
SINAP, Shanghai, People's Republic of China
A.A. Aksoy, O. Yavaş
Ankara University, Accelerator Technologies Institute, Golbasi / Ankara, Turkey
D. Angal-Kalinin, J.A. Clarke
Cockcroft Institute, Warrington, Cheshire, United Kingdom
C.J. Bocchetta, A.I. Wawrzyniak
Solaris, Kraków, Poland
M.J. Boland
SLSA, Clayton, Australia
G. D'Auria, S. Di Mitri, C. Serpico
Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
T.J.C. Ekelöf, R.J.M.Y. Ruber, V.G. Ziemann
Uppsala University, Uppsala, Sweden
E.N. Gazis
National Technical University of Athens, Athens, Greece
A. Grudiev, A. Latina, D. Schulte, S. Stapnes, W. Wuensch
CERN, Geneva, Switzerland

One compact hard X-ray FEL facility is being planned at SINAP, and X-band high gradient accelerating structure is the most competetive scheme for this plan. X-band accelerating structure is designed to switch between 60MV/m and 80MV/m, and carries out 6GeV and 8GeV by 130 meters linac respectively. In this paper, brief layout of compact XFEL will be introduced, and in particular the prototype design of dedicated X-band acceleration RF system is also presented.

TUPP140

Observation of >GV/m Decelerating Fields in Dielectric Lined Waveguides

radiation, vacuum, experiment, electron

743

B.D. O'Shea, G. Andonian, K.L. Fitzmorris, S. Hakimi, J. Harrison, J.B. Rosenzweig, O. Williams
UCLA, Los Angeles, California, USA
M.J. Hogan, V. Yakimenko
SLAC, Menlo Park, California, USA

Recent experimental measurements of the energy lost to wakefields in a dielectric lined waveguide are presented. These measurements demonstrate average decelerating gradients on the order of >1 GV/m, for two different structures. The measurements were made at the Facility for Advanced aCcelerator Experimental Tests (FACET) at SLAC National Laboratory using sub-millimeter diameter fifteen-centimeter long quartz fibers of annular cross section. The unique extremely short, high charge, ultra relativistic beam at FACET (200 fs, 3 nC, 20 GeV) allows the use of dielectric wakefield structures of unprecedented size and length. In addition to experimental results, we support conclusions with simulation and theoretical work. This measurement builds on a large body of work previously performed using dielectric wakefield structures in an effort to provide high gradient accelerating structures for tomorrows linear colliders.

THPP034

Toolbox for Applying Beam-Based Alignment to Linacs

linac, emittance, interface, controls

916

A. Latina, D. Pellegrini, J. Pfingstner, D. Schulte
CERN, Geneva, Switzerland
E. Adli
University of Oslo, Oslo, Norway

Tests of Beam-Based Alignment have been performed at FACET, at SLAC in the USA, and at Fermi, at Elettra in Trieste, Italy, with very promising results. Dispersion-Free Steering and Wakefield-free steering have been successfully applied to both machines. In order to make the correction process as automatic as possible, a set of robust tools has been developed, which allowed to span a large set of parameters. These tools and some of the experimental results performed at both machines are presented in this paper.

THPP124

Wakefields in the Superconducting RF Cavities of LCLS-II

cavity, linac, electron, niobium

1147

K.L.F. Bane, T.O. Raubenheimer
SLAC, Menlo Park, California, USA
A. Romanenko, V.P. Yakovlev
Fermilab, Batavia, Illinois, USA

Funding: Work supported by Department of Energy contract DE–AC02–76SF00515.
The superconducting cavities in the linacs of LCLS-II are designed to operate at 2K, where cooling costs are very expensive. In addition to an unavoidable static load and the dynamic load of the fundamental 1.3 GHz accelerating rf, there will be higher order mode (HOM) power deposited by the beam. Due to the very short bunch length the LCLS-II beam spectrum extends into the THz range. Ceramic absorbers, cooled to 70K and located between cryomodules, are meant to absorb much of this power; understanding their effectiveness, however, is a challenging task. In this report we calculate the amount of power radiated by the beam in the different portions of the linac as the bunch length is changed by the bunch compressors. We consider both the steady state radiation as well as transients that arise at the beginning of the linac structures. In addition, transitions due to changes in the vacuum chamber aperture at the ends of the linacs are also considered. Finally, under the assumption that all the wake power ends up in the SRF cavity walls, we estimate the wall heating and the possibility of breaking the Cooper pairs and quenching the cavities.