IPAC2016 - Classification: 05 Beam Dynamics and Electromagnetic Fields / D10 Beam-beam Effects - Theory, Simulations, Measurements, Code Developments

Paper	Title	Page
MOZA01	Simulated Beam-beam Limits for Circular Lepton and Hadron Colliders	27
	K. Ohmi KEK, Ibaraki, Japan
	The beam-beam limit is one of the most important collider parameters. For lepton colliders the empirical tune shift limits are higher than for hadron colliders, which has been attributed to strong radiation damping. The beam-beam limit in hadron colliders, like the LHC, can be affected by noise. For future higher-energy colliders, like FCC-hh or SppC, the limit can be higher or lower, in the presence of still rather weak synchrotron radiation. For circular lepton colliders, like DAΦNE, SuperKEKB, FCC-ee or CepC, the effect of large Piwinski angle, and crab waist, as well as the dependence of the beam-beam limit on the number of interaction points are important questions. This presentation reviews the state of the art in weak-strong, quasi-strong-strong and strong-strong beam-beam simulations and reports the various dependencies of the simulated beam-beam limit on the aforementioned parameters.
	Slides MOZA01 [4.453 MB]
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WEPOY024	Beam Dynamics Simulations of the Thomx Linac	3036
	L. Garolfi, C. Bruni, M. El Khaldi, P. Lepercq, C. Vallerand LAL, Orsay, France N. Faure PMB-ALCEN, PEYNIER, France
	ThomX Compton light source is designed to maximise the average X-ray flux providing a compact and tunable machine which can operate in hospitals or in museums. These constraints impose the choice of a high collision rate which is based on S-band Linac whose energy is 50-70 MeV combined to an electron storage ring. As most of the performances of the electron beam at the interaction point depend on the beam quality at the ring entrance, the linear accelerator must be carefully designed and especially the photo-injector. Simulations have been carried out in order to optimise the emittance for the ring entrance. Indeed, for a bunch charge of 1 nC, space charge effects usually dominate the total beam emittance. The latter can be minimized at the end of the Linac by means of emittance compensation. The best configuration across all the parameters will be presented.
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WEPOY025	High Power RF Generation From a W-Band Corrugated Structure Excited by a Train of Electron Bunches	3040
SUPSS062	use link to see paper's listing under its alternate paper code
	D. Wang, C.-X. Tang TUB, Beijing, People's Republic of China S.P. Antipov, C.-J. Jing, J.Q. Qiu Euclid TechLabs, LLC, Solon, Ohio, USA M.E. Conde, D.S. Doran, W. Gai, G. Ha, G. Ha, W. Liu, J.G. Power, E.E. Wisniewski ANL, Argonne, Illinois, USA V.A. Dolgashev SLAC, Menlo Park, California, USA
	We report on the generation of multi-megawatt peak RF power at 91textGHz, using an ultrarelativistic electron bunch train to excite electromagnetic fields in a high-impedance metallic corrugated structure. This device can be used as a power source for high gradient acceleration of electrons. To achieve precise control of the wakefield phase, a long range wakefield interferometry method was developed in which the RF energy due to the interference of the wakefields from two bunches was measured as a function of the bunch separation.
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WEPOY028	Laser Heater System Test at PAL-XFEL ITF	3048
	J. H. Lee POSTECH, Pohang, Kyungbuk, Republic of Korea J.H. Han, J.H. Hong, C.H. Kim, I.S. Ko, S.J. Lee PAL, Pohang, Kyungbuk, Republic of Korea
	Coherent x-ray photons are generated by a free electron laser (FEL). In PAL-XFEL, a photon beam with a 0.1 nm wavelength is generated from an electron bunch based on self-amplified spontaneous emission (SASE). An electron bunch with an uncorrelated energy spread in a level of 3 keV, which is generated from the photocathode RF gun, may be sensitive to longitudinal micro-bunching instability. The energy spread of an electron bunch can be increased to suppress the instability by Landau damping. In order to control the uncorrelated energy spread, a laser heater system, which has a chicane with four dipoles chicane and a 0.5 m long undulator, was installed in the injector test facility (ITF) of PAL. In this paper, we introduce the parameters of the laser heater and heating effect on the electron bunch.
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WEPOY030	First BTF Measurements at the Large Hadron Collider	3051
SUPSS061	use link to see paper's listing under its alternate paper code
	C. Tambasco, A. Boccardi, X. Buffat, K. Fuchsberger, M. Gąsior, R. Giachino, T. Lefèvre, T.E. Levens, T. Pieloni, M. Pojer, B. Salvachua, M. Solfaroli Camillocci CERN, Geneva, Switzerland J. Barranco, C. Tambasco EPFL, Lausanne, Switzerland
	During the Run I in 2012, several instabilities have been observed at the Large Hadron Collider (LHC) during the Betatron squeeze. The predictions of instability thresholds are based on the computation of the beam Landau damping by calculating the Stability Diagrams (SD). These instabilities could be explained by a deterioration of the SD due to beam-beam resonance excitation which could change the particle distributions. Beam Transfer Functions (BTF) provide a measurement of the Stability Diagram. The BTFs are sensitive to the particle detuning with amplitude as well as to the particle distributions therefore they represent a powerful tool to understand experimentally the stability of beams during the LHC operational cycle. First BTF measurements at the LHC are presented for different machine configurations and settings and compared to predictions.
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WEPOY056	Beam-beam Simulations with Realistic Crab Crossing for the eRhic Ring-Ring Electron Beam	3123
	C. Montag BNL, Upton, Long Island, New York, USA
	Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy. The 15mrad beam crossing angle in the eRHIC ring-ring interaction region requires crab crossing of the 250GeV proton beam to restore the luminosity. Since the product of the RF voltage and the RF frequency of the crab cavities is constant for a given crossing angle, higher frequencies are preferred in order to limit the require voltage. However, the 20cm RMS proton bunch length provides an upper limit of the useable frequencies due to the significant curvature of the RF waveform over this bunch length. To study the effectof realistic crab cavities with a finite wavelength on electron beam-beamdynamics and to determine the potential need for higher harmonic crab cavities to linearize the kick a simulation code has been developed.
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Paper

Title

Page

Simulated Beam-beam Limits for Circular Lepton and Hadron Colliders

27

K. Ohmi
KEK, Ibaraki, Japan

The beam-beam limit is one of the most important collider parameters. For lepton colliders the empirical tune shift limits are higher than for hadron colliders, which has been attributed to strong radiation damping. The beam-beam limit in hadron colliders, like the LHC, can be affected by noise. For future higher-energy colliders, like FCC-hh or SppC, the limit can be higher or lower, in the presence of still rather weak synchrotron radiation. For circular lepton colliders, like DAΦNE, SuperKEKB, FCC-ee or CepC, the effect of large Piwinski angle, and crab waist, as well as the dependence of the beam-beam limit on the number of interaction points are important questions. This presentation reviews the state of the art in weak-strong, quasi-strong-strong and strong-strong beam-beam simulations and reports the various dependencies of the simulated beam-beam limit on the aforementioned parameters.

Slides MOZA01 [4.453 MB]

Export •

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

WEPOY024

Beam Dynamics Simulations of the Thomx Linac

3036

L. Garolfi, C. Bruni, M. El Khaldi, P. Lepercq, C. Vallerand
LAL, Orsay, France
N. Faure
PMB-ALCEN, PEYNIER, France

ThomX Compton light source is designed to maximise the average X-ray flux providing a compact and tunable machine which can operate in hospitals or in museums. These constraints impose the choice of a high collision rate which is based on S-band Linac whose energy is 50-70 MeV combined to an electron storage ring. As most of the performances of the electron beam at the interaction point depend on the beam quality at the ring entrance, the linear accelerator must be carefully designed and especially the photo-injector. Simulations have been carried out in order to optimise the emittance for the ring entrance. Indeed, for a bunch charge of 1 nC, space charge effects usually dominate the total beam emittance. The latter can be minimized at the end of the Linac by means of emittance compensation. The best configuration across all the parameters will be presented.

Export •

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

WEPOY025

High Power RF Generation From a W-Band Corrugated Structure Excited by a Train of Electron Bunches

3040

SUPSS062

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

D. Wang, C.-X. Tang
TUB, Beijing, People's Republic of China
S.P. Antipov, C.-J. Jing, J.Q. Qiu
Euclid TechLabs, LLC, Solon, Ohio, USA
M.E. Conde, D.S. Doran, W. Gai, G. Ha, G. Ha, W. Liu, J.G. Power, E.E. Wisniewski
ANL, Argonne, Illinois, USA
V.A. Dolgashev
SLAC, Menlo Park, California, USA

We report on the generation of multi-megawatt peak RF power at 91textGHz, using an ultrarelativistic electron bunch train to excite electromagnetic fields in a high-impedance metallic corrugated structure. This device can be used as a power source for high gradient acceleration of electrons. To achieve precise control of the wakefield phase, a long range wakefield interferometry method was developed in which the RF energy due to the interference of the wakefields from two bunches was measured as a function of the bunch separation.

Export •

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

WEPOY028

Laser Heater System Test at PAL-XFEL ITF

3048

J. H. Lee
POSTECH, Pohang, Kyungbuk, Republic of Korea
J.H. Han, J.H. Hong, C.H. Kim, I.S. Ko, S.J. Lee
PAL, Pohang, Kyungbuk, Republic of Korea

Coherent x-ray photons are generated by a free electron laser (FEL). In PAL-XFEL, a photon beam with a 0.1 nm wavelength is generated from an electron bunch based on self-amplified spontaneous emission (SASE). An electron bunch with an uncorrelated energy spread in a level of 3 keV, which is generated from the photocathode RF gun, may be sensitive to longitudinal micro-bunching instability. The energy spread of an electron bunch can be increased to suppress the instability by Landau damping. In order to control the uncorrelated energy spread, a laser heater system, which has a chicane with four dipoles chicane and a 0.5 m long undulator, was installed in the injector test facility (ITF) of PAL. In this paper, we introduce the parameters of the laser heater and heating effect on the electron bunch.

Export •

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

WEPOY030

First BTF Measurements at the Large Hadron Collider

3051

SUPSS061

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

C. Tambasco, A. Boccardi, X. Buffat, K. Fuchsberger, M. Gąsior, R. Giachino, T. Lefèvre, T.E. Levens, T. Pieloni, M. Pojer, B. Salvachua, M. Solfaroli Camillocci
CERN, Geneva, Switzerland
J. Barranco, C. Tambasco
EPFL, Lausanne, Switzerland

During the Run I in 2012, several instabilities have been observed at the Large Hadron Collider (LHC) during the Betatron squeeze. The predictions of instability thresholds are based on the computation of the beam Landau damping by calculating the Stability Diagrams (SD). These instabilities could be explained by a deterioration of the SD due to beam-beam resonance excitation which could change the particle distributions. Beam Transfer Functions (BTF) provide a measurement of the Stability Diagram. The BTFs are sensitive to the particle detuning with amplitude as well as to the particle distributions therefore they represent a powerful tool to understand experimentally the stability of beams during the LHC operational cycle. First BTF measurements at the LHC are presented for different machine configurations and settings and compared to predictions.

Export •

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

WEPOY056

Beam-beam Simulations with Realistic Crab Crossing for the eRhic Ring-Ring Electron Beam

3123

C. Montag
BNL, Upton, Long Island, New York, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
The 15mrad beam crossing angle in the eRHIC ring-ring interaction region requires crab crossing of the 250GeV proton beam to restore the luminosity. Since the product of the RF voltage and the RF frequency of the crab cavities is constant for a given crossing angle, higher frequencies are preferred in order to limit the require voltage. However, the 20cm RMS proton bunch length provides an upper limit of the useable frequencies due to the significant curvature of the RF waveform over this bunch length. To study the effectof realistic crab cavities with a finite wavelength on electron beam-beamdynamics and to determine the potential need for higher harmonic crab cavities to linearize the kick a simulation code has been developed.

Export •

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