HB2016 - List of Keywords (coupling)

Paper	Title	Other Keywords	Page
MOPR010	Machine Element Contribution to the Longitudinal Impedance Model of the CERN SPS	impedance, simulation, resonance, pick-up	71
	T. Kaltenbacher, F. Caspers, C. Vollinger CERN, Geneva, Switzerland
	This contribution describes the current longitudinal impedance model of the SPS and studies carried out in order to improve, extend and update it. Specifically, new sources of impedances have been identified, evaluated and included in the model. One finding are low Q and low-frequency (LF; here below 1 GHz) resonances which occur due to enamelled flanges in combination with external cabling e.g. ground loops. These resonances couple to the beam through the gap with enamel coating which creates an open resonator. Since this impedance is important for beam stability in the CERN Proton Synchrotron (PS), RF by-passes were installed on the enamelled flanges, and their significance for the SPS beam is currently under investigation. Simulations, bench and beam measurements were used to deduce model parameters for beam dynamic simulations.
Export •	reference for this paper to ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

MOPR024	General Formula to Deduce the Space Charge Tune Spread From a Quadrupolar Pick-Up Measurement	space-charge, resonance, pick-up, kicker	120
	E. Métral CERN, Geneva, Switzerland
	In 1966, W. Hardt derived the oscillation frequencies obtained in the presence of space charge forces and gradients errors for elliptical beams. Since then, a simple formula is usually used to relate the shift of the quadrupolar mode (obtained from the quadrupolar pick-up) and the space charge tune spread, depending only on the ratio between the two transverse equilibrium beam sizes. However, this formula is not always valid, in particular for machines running close to the coupling resonance Qx = Qy with almost round beams. A new general formula is presented, giving the space charge tune spread as a function of i) the measured shift of the quadrupolar mode, ii) the ratio between the two transverse equilibrium beam sizes and iii) the distance between the two transverse tunes.
Export •	reference for this paper to ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUAM2X01	Measurement and Interpretation of Transverse Beam Instabilities in the CERN Large Hadron Collider (LHC) and Extrapolations to HL-LHC	octupole, simulation, electron, injection	254
	E. Métral, G. Arduini, N. Biancacci, X. Buffat, L.R. Carver, G. Iadarola, K.S.B. Li, T. Pieloni, A. Romano, G. Rumolo, B. Salvant, M. Schenk, C. Tambasco CERN, Geneva, Switzerland J. Barranco EPFL, Lausanne, Switzerland
	Since the first transverse instability observed in 2010, many studies have been performed on both measurement and simulation sides and several lessons have been learned. In a machine like the LHC, not only all the mechanisms have to be understood separately, but the possible interplays between the different phenomena need to be analyzed in detail, including the beam-coupling impedance (with in particular all the necessary collimators to protect the machine but also new equipment such as crab cavities for HL-LHC), linear and nonlinear chromaticity, Landau octupoles (and other intrinsic nonlinearities), transverse damper, space charge, beam-beam (long-range and head-on), electron cloud, linear coupling strength, tune separation between the transverse planes, tune split between the two beams, transverse beam separation between the two beams, etc. This paper reviews all the transverse beam instabilities observed and simulated so far, the mitigation measures which have been put in place, the remaining questions and challenges and some recommendations for the future.
	Slides TUAM2X01 [36.385 MB]
Export •	reference for this paper to ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUPM9Y01	Observations of Coupling During Accumulation Using a Non-Destructive Electron Scanner in the Spallation Neutron Source Accumulator Ring	electron, experiment, accumulation, quadrupole	351
	R.E. Potts ORNL RAD, Oak Ridge, Tennessee, USA W. Blokland, S.M. Cousineau, J.A. Holmes ORNL, Oak Ridge, Tennessee, USA
	An electron scanner has been installed in the accumulator ring of the Spallation Neutron Source (SNS). The non-destructive device permits turn-by-turn measurements of the horizontal and vertical profiles of the proton beam during accumulation with fine longitudinal resolution. In this study the device is used to identify the source of transverse coupling in the SNS ring and to understand the impact of space charge on the evolution of the coupled beam. We present experimental observations of coupling dependent on tune, injected intensity, and accumulated intensity for a simplified accumulation scenario with no RF and no injection painting. We also investigate the effects of varying the skew quadrupoles and tune for beams with the SNS production-style ring injection and ring RF patterns.
	Slides TUPM9Y01 [3.849 MB]
Export •	reference for this paper to ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEAM1Y01	A Coupled RFQ-IH-DTL Cavity for FRANZ: A Challenge for RF Technology and Beam Dynamics	rfq, DTL, cavity, neutron	404
	R. Tiede, O. Meusel, H. Podlech, U. Ratzinger, A. Schempp, M. Schwarz IAP, Frankfurt am Main, Germany M. Heilmann GSI, Darmstadt, Germany D. Mäder BEVATECH, Frankfurt, Germany
	For the 'Frankfurt Neutron Source at the Stern-Gerlach-Zentrum' (FRANZ) facility an inductively coupled combination of a 4-rod radio-frequency-quadrupole (RFQ) and an 8 gap interdigital H-type (IH-DTL) structure will provide the main acceleration of an intense proton beam from 120 keV to 2.0 MeV. The RFQ-IH combination with a total length of about 2.3 m will be operated at 175 MHz in cw mode. The expected total power need is around 200 kW. Due to the internal inductive coupling only one RF amplifier is needed, which significantly reduces the investment costs. At present the RFQ is installed separately in the beam line for conditioning up to the design rf power and for measuring the beam quality behind the RFQ. In parallel, the IH-DTL is rf tuned together with a dummy RFQ outside the FRANZ cave. This paper will present the status of the project with emphasis on key questions like beam dynamics constraints, rf tuning issues and technological challenges resulting from the high thermal load in cw operation.
	Slides WEAM1Y01 [3.756 MB]
Export •	reference for this paper to ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPM10X01	Stripline Beam Position Monitors With Improved Frequency Response and Their Coupling Impedances	impedance, simulation, network, electron	523
	Y. Shobuda JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan Y.H. Chin, K. Takata KEK, Ibaraki, Japan K.G. Nakamura Kyoto University, Kyoto, Japan T. Toyama J-PARC, KEK & JAEA, Ibaraki-ken, Japan
	In J-PARC Main Ring, transverse intra-bunch oscillations have been observed during the injection and at the onset of acceleration. Up to now, the beam instability is suppressed by the intra-bunch feedback system, where the stripline beam position monitors operate at 10⁸.8 MHz. However, there is a concern that electron cloud instabilities may appear and limit the beam current at future higher power operations. For the case, we have developed a wider-band (several GHz) beam position monitor by deforming the electrode shapes. The modification of the electrode can be done not to enhance the beam coupling impedance. For the typical electrode shapes, we show the coupling impedances as well as the frequency responses of the electrodes.
	Slides THPM10X01 [5.240 MB]
Export •	reference for this paper to ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

Paper

Title

Other Keywords

Page

MOPR010

Machine Element Contribution to the Longitudinal Impedance Model of the CERN SPS

impedance, simulation, resonance, pick-up

71

T. Kaltenbacher, F. Caspers, C. Vollinger
CERN, Geneva, Switzerland

This contribution describes the current longitudinal impedance model of the SPS and studies carried out in order to improve, extend and update it. Specifically, new sources of impedances have been identified, evaluated and included in the model. One finding are low Q and low-frequency (LF; here below 1 GHz) resonances which occur due to enamelled flanges in combination with external cabling e.g. ground loops. These resonances couple to the beam through the gap with enamel coating which creates an open resonator. Since this impedance is important for beam stability in the CERN Proton Synchrotron (PS), RF by-passes were installed on the enamelled flanges, and their significance for the SPS beam is currently under investigation. Simulations, bench and beam measurements were used to deduce model parameters for beam dynamic simulations.

Export •

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

MOPR024

General Formula to Deduce the Space Charge Tune Spread From a Quadrupolar Pick-Up Measurement

space-charge, resonance, pick-up, kicker

120

E. Métral
CERN, Geneva, Switzerland

In 1966, W. Hardt derived the oscillation frequencies obtained in the presence of space charge forces and gradients errors for elliptical beams. Since then, a simple formula is usually used to relate the shift of the quadrupolar mode (obtained from the quadrupolar pick-up) and the space charge tune spread, depending only on the ratio between the two transverse equilibrium beam sizes. However, this formula is not always valid, in particular for machines running close to the coupling resonance Qx = Qy with almost round beams. A new general formula is presented, giving the space charge tune spread as a function of i) the measured shift of the quadrupolar mode, ii) the ratio between the two transverse equilibrium beam sizes and iii) the distance between the two transverse tunes.

Export •

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

TUAM2X01

Measurement and Interpretation of Transverse Beam Instabilities in the CERN Large Hadron Collider (LHC) and Extrapolations to HL-LHC

octupole, simulation, electron, injection

254

E. Métral, G. Arduini, N. Biancacci, X. Buffat, L.R. Carver, G. Iadarola, K.S.B. Li, T. Pieloni, A. Romano, G. Rumolo, B. Salvant, M. Schenk, C. Tambasco
CERN, Geneva, Switzerland
J. Barranco
EPFL, Lausanne, Switzerland

Since the first transverse instability observed in 2010, many studies have been performed on both measurement and simulation sides and several lessons have been learned. In a machine like the LHC, not only all the mechanisms have to be understood separately, but the possible interplays between the different phenomena need to be analyzed in detail, including the beam-coupling impedance (with in particular all the necessary collimators to protect the machine but also new equipment such as crab cavities for HL-LHC), linear and nonlinear chromaticity, Landau octupoles (and other intrinsic nonlinearities), transverse damper, space charge, beam-beam (long-range and head-on), electron cloud, linear coupling strength, tune separation between the transverse planes, tune split between the two beams, transverse beam separation between the two beams, etc. This paper reviews all the transverse beam instabilities observed and simulated so far, the mitigation measures which have been put in place, the remaining questions and challenges and some recommendations for the future.

Slides TUAM2X01 [36.385 MB]

Export •

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

TUPM9Y01

Observations of Coupling During Accumulation Using a Non-Destructive Electron Scanner in the Spallation Neutron Source Accumulator Ring

electron, experiment, accumulation, quadrupole

351

R.E. Potts
ORNL RAD, Oak Ridge, Tennessee, USA
W. Blokland, S.M. Cousineau, J.A. Holmes
ORNL, Oak Ridge, Tennessee, USA

An electron scanner has been installed in the accumulator ring of the Spallation Neutron Source (SNS). The non-destructive device permits turn-by-turn measurements of the horizontal and vertical profiles of the proton beam during accumulation with fine longitudinal resolution. In this study the device is used to identify the source of transverse coupling in the SNS ring and to understand the impact of space charge on the evolution of the coupled beam. We present experimental observations of coupling dependent on tune, injected intensity, and accumulated intensity for a simplified accumulation scenario with no RF and no injection painting. We also investigate the effects of varying the skew quadrupoles and tune for beams with the SNS production-style ring injection and ring RF patterns.

Slides TUPM9Y01 [3.849 MB]

Export •

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

WEAM1Y01

A Coupled RFQ-IH-DTL Cavity for FRANZ: A Challenge for RF Technology and Beam Dynamics

rfq, DTL, cavity, neutron

404

R. Tiede, O. Meusel, H. Podlech, U. Ratzinger, A. Schempp, M. Schwarz
IAP, Frankfurt am Main, Germany
M. Heilmann
GSI, Darmstadt, Germany
D. Mäder
BEVATECH, Frankfurt, Germany

For the 'Frankfurt Neutron Source at the Stern-Gerlach-Zentrum' (FRANZ) facility an inductively coupled combination of a 4-rod radio-frequency-quadrupole (RFQ) and an 8 gap interdigital H-type (IH-DTL) structure will provide the main acceleration of an intense proton beam from 120 keV to 2.0 MeV. The RFQ-IH combination with a total length of about 2.3 m will be operated at 175 MHz in cw mode. The expected total power need is around 200 kW. Due to the internal inductive coupling only one RF amplifier is needed, which significantly reduces the investment costs. At present the RFQ is installed separately in the beam line for conditioning up to the design rf power and for measuring the beam quality behind the RFQ. In parallel, the IH-DTL is rf tuned together with a dummy RFQ outside the FRANZ cave. This paper will present the status of the project with emphasis on key questions like beam dynamics constraints, rf tuning issues and technological challenges resulting from the high thermal load in cw operation.

Slides WEAM1Y01 [3.756 MB]

Export •

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

THPM10X01

Stripline Beam Position Monitors With Improved Frequency Response and Their Coupling Impedances

impedance, simulation, network, electron

523

Y. Shobuda
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan
Y.H. Chin, K. Takata
KEK, Ibaraki, Japan
K.G. Nakamura
Kyoto University, Kyoto, Japan
T. Toyama
J-PARC, KEK & JAEA, Ibaraki-ken, Japan

In J-PARC Main Ring, transverse intra-bunch oscillations have been observed during the injection and at the onset of acceleration. Up to now, the beam instability is suppressed by the intra-bunch feedback system, where the stripline beam position monitors operate at 10⁸.8 MHz. However, there is a concern that electron cloud instabilities may appear and limit the beam current at future higher power operations. For the case, we have developed a wider-band (several GHz) beam position monitor by deforming the electrode shapes. The modification of the electrode can be done not to enhance the beam coupling impedance. For the typical electrode shapes, we show the coupling impedances as well as the frequency responses of the electrodes.

Slides THPM10X01 [5.240 MB]

Export •

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