HB2016 - List of Keywords (impedance)

Paper	Title	Other Keywords	Page
MOPR007	Cold and High Power Test of Large Size Magnetic Alloy Core for XiPAF's Synchrotron	cavity, experiment, synchrotron, proton	59
	G.R. Li, X. Guan, W.-H. Huang, X.W. Wang, Z. Yang, H.J. Yao, H.J. Zeng, S.X. Zheng TUB, Beijing, People's Republic of China
	A compact magnetic alloy (MA) loaded cavity is under development for XiPAF's synchrotron. The cavity contains 6 large size MA cores, each is independently coupled with solid state power amplifier. Two types of MA core are proposed for the project. We have developed a single core model cavity to verify the impedance model and to test the properties of MA cores under high power state. The high power test results are presented and discussed.
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MOPR010	Machine Element Contribution to the Longitudinal Impedance Model of the CERN SPS	simulation, resonance, coupling, 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.
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MOPR011	The SPS 200 MHz TWC Impedance after the LIU Upgrade	cavity, HOM, simulation, pick-up	76
	T. Roggen, R. Calaga, F. Caspers, T. Kaltenbacher, C. Vollinger CERN, Geneva, Switzerland
	Funding: Fellowship co-funded by the European Union as a Marie Curie action (Grant agreement PCOFUND-GA-2010-267194) within the Seventh Framework Programme for Research and Technological Development. As a part of the LHC Injectors Upgrade project (LIU) the 200 MHz Travelling Wave Cavities (TWC) of the Super Proton Synchrotron (SPS) will be upgraded. The two existing five-section cavities will be rearranged into four three-section cavities (using two existing spare sections), thereby increasing the total voltage from 7 MV (I_RF = 1.5 A) to 10 MV (I_RF = 3.0 A). Projections of the HL-LHC (High Luminosity Large Hadron Collider) era are conceived by the macro-particle simulation code BLonD, that makes use of an impedance model of the SPS, developed from a thorough survey of machine elements. This paper analyses the impedance contribution of the 200 MHz cavities in the two configurations, using electromagnetic simulations. Measurements of the existing cavities in the SPS and a single-section prototype are also presented.
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MOPR028	CERN PS Booster Longitudinal Dynamics Simulations for the Post-LS2 Scenario	emittance, space-charge, injection, simulation	140
	D. Quartullo, S.C.P. Albright, E.N. Shaposhnikova, H. Timko CERN, Geneva, Switzerland
	The CERN PS Booster is the first synchrotron in the LHC proton injection chain, it currently accelerates particles from 50 MeV to 1.4 GeV kinetic energy. Several upgrades foreseen by the LHC Injectors Upgrade Program will allow the beam to be accelerated from 160 MeV to 2 GeV after Long Shutdown 2 in 2021. The present RF systems will be replaced by a new one, based on Finemet technology. These and other improvements will help to increase the LHC luminosity by a factor of ten. In order to study beam stability in the longitudinal plane simulations have been performed with the CERN BLonD code, using an accurate longitudinal impedance model and a reliable estimation of the longitudinal space charge. Particular attention has been dedicated to the three main features that currently let the beam go stably through the ramp: Double RF operation in bunch-lengthening mode to reduce the transverse space charge tune spread, exploitation of feedback loops to damp dipole oscillations, and controlled longitudinal emittance blow-up. RF phase noise injection has been considered to study if it could complement or substitute the currently used method based on sinusoidal phase modulation.
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MOPR031	Development of Physics Models of the ISIS Head-Tail Instability	simulation, space-charge, synchrotron, acceleration	155
	R.E. Williamson, B. Jones, C.M. Warsop STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom
	ISIS is the pulsed spallation neutron and muon source at the Rutherford Appleton Laboratory in the UK. Operation centres on a rapid cycling proton synchrotron which accelerates 3·10¹³ protons per pulse (ppp) from 70 MeV to 800 MeV at 50 Hz, delivering a mean beam power of 0.2 MW. As a high intensity, loss-limited machine, research and development at ISIS is focused on understanding loss mechanisms with a view to improving operational performance and guiding possible upgrade routes. The head-tail instability observed on ISIS is of particular interest as it is currently a main limitation on beam intensity. Good models of impedance are essential for understanding instabilities and to this end, recent beam-based measurements of the effective transverse impedance of the ISIS synchrotron are presented. This paper also presents developments of a new, in-house code to simulate the head-tail instability observed and includes benchmarks against theory and comparisons with experimental results.
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MOPR033	Beam Acceleration and Transition Crossing in the Fermilab Booster	simulation, booster, emittance, timing	160
	V.A. Lebedev, C.M. Bhat, J.-F. Ostiguy Fermilab, Batavia, Illinois, USA
	To suppress eddy currents, the Fermilab rapid cycling Booster synchrotron has no beam pipe; rather, its combined function dipoles are evacuated, exposing the beam directly to the magnet laminations. This arrangement significantly increases the resistive wall impedance of the dipoles and, in combination with the space charge impedance, substantially complicates longitudinal dynamics at transition. Voltage and accelerating phase profiles in the vicinity of transition are typically empirically optimized to minimize beam loss and emittance growth. In this contribution, we present results of experimental studies of beam acceleration near transition. Using comparisons between observed beam parameters and simulations, we obtain accurate calibrations for the RF program and extract quantitative information about parameters of relevance to the Booster laminated magnets longitudinal impedance model. The results are used to analyze transition crossing in the context of a future 50% increase in beam intensity planned for PIP-II, an upgrade of the Fermilab accelerating complex.
	Poster MOPR033 [0.231 MB]
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TUAM3X01	Identification and Reduction of the CERN SPS Impedance	emittance, flattop, vacuum, simulation	260
	E.N. Shaposhnikova, T. Argyropoulos, T. Bohl, A. Lasheen, J. Repond, H. Timko CERN, Geneva, Switzerland
	The first SPS impedance reduction programme has been completed in 2001, preparing the ring for its role as an injector of the LHC. This action has eliminated microwave instability on the SPS flat bottom and later nominal beam could be delivered to the LHC. The High Luminosity (HL-) LHC project is based on beam with twice higher intensity than the nominal one. One of the important SPS intensity limitations are longitudinal instabilities with minimum threshold reached on the 450 GeV flat top. In this paper the work which was carried on to identify the impedance sources driving these instabilities is described together with the next campaign of the SPS impedance reduction planned by the LHC Injector Upgrade (LIU) project. The present knowledge of the SPS transverse impedance is also presented.
	Slides TUAM3X01 [6.457 MB]
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THPM10X01	Stripline Beam Position Monitors With Improved Frequency Response and Their Coupling Impedances	simulation, coupling, 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]
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Paper

Title

Other Keywords

Page

MOPR007

Cold and High Power Test of Large Size Magnetic Alloy Core for XiPAF's Synchrotron

cavity, experiment, synchrotron, proton

59

G.R. Li, X. Guan, W.-H. Huang, X.W. Wang, Z. Yang, H.J. Yao, H.J. Zeng, S.X. Zheng
TUB, Beijing, People's Republic of China

A compact magnetic alloy (MA) loaded cavity is under development for XiPAF's synchrotron. The cavity contains 6 large size MA cores, each is independently coupled with solid state power amplifier. Two types of MA core are proposed for the project. We have developed a single core model cavity to verify the impedance model and to test the properties of MA cores under high power state. The high power test results are presented and discussed.

Export •

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

MOPR010

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

simulation, resonance, coupling, 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)

MOPR011

The SPS 200 MHz TWC Impedance after the LIU Upgrade

cavity, HOM, simulation, pick-up

76

T. Roggen, R. Calaga, F. Caspers, T. Kaltenbacher, C. Vollinger
CERN, Geneva, Switzerland

Funding: Fellowship co-funded by the European Union as a Marie Curie action (Grant agreement PCOFUND-GA-2010-267194) within the Seventh Framework Programme for Research and Technological Development.
As a part of the LHC Injectors Upgrade project (LIU) the 200 MHz Travelling Wave Cavities (TWC) of the Super Proton Synchrotron (SPS) will be upgraded. The two existing five-section cavities will be rearranged into four three-section cavities (using two existing spare sections), thereby increasing the total voltage from 7 MV (I_RF = 1.5 A) to 10 MV (I_RF = 3.0 A). Projections of the HL-LHC (High Luminosity Large Hadron Collider) era are conceived by the macro-particle simulation code BLonD, that makes use of an impedance model of the SPS, developed from a thorough survey of machine elements. This paper analyses the impedance contribution of the 200 MHz cavities in the two configurations, using electromagnetic simulations. Measurements of the existing cavities in the SPS and a single-section prototype are also presented.

Export •

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

MOPR028

CERN PS Booster Longitudinal Dynamics Simulations for the Post-LS2 Scenario

emittance, space-charge, injection, simulation

140

D. Quartullo, S.C.P. Albright, E.N. Shaposhnikova, H. Timko
CERN, Geneva, Switzerland

The CERN PS Booster is the first synchrotron in the LHC proton injection chain, it currently accelerates particles from 50 MeV to 1.4 GeV kinetic energy. Several upgrades foreseen by the LHC Injectors Upgrade Program will allow the beam to be accelerated from 160 MeV to 2 GeV after Long Shutdown 2 in 2021. The present RF systems will be replaced by a new one, based on Finemet technology. These and other improvements will help to increase the LHC luminosity by a factor of ten. In order to study beam stability in the longitudinal plane simulations have been performed with the CERN BLonD code, using an accurate longitudinal impedance model and a reliable estimation of the longitudinal space charge. Particular attention has been dedicated to the three main features that currently let the beam go stably through the ramp: Double RF operation in bunch-lengthening mode to reduce the transverse space charge tune spread, exploitation of feedback loops to damp dipole oscillations, and controlled longitudinal emittance blow-up. RF phase noise injection has been considered to study if it could complement or substitute the currently used method based on sinusoidal phase modulation.

Export •

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

MOPR031

Development of Physics Models of the ISIS Head-Tail Instability

simulation, space-charge, synchrotron, acceleration

155

R.E. Williamson, B. Jones, C.M. Warsop
STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom

ISIS is the pulsed spallation neutron and muon source at the Rutherford Appleton Laboratory in the UK. Operation centres on a rapid cycling proton synchrotron which accelerates 3·10¹³ protons per pulse (ppp) from 70 MeV to 800 MeV at 50 Hz, delivering a mean beam power of 0.2 MW. As a high intensity, loss-limited machine, research and development at ISIS is focused on understanding loss mechanisms with a view to improving operational performance and guiding possible upgrade routes. The head-tail instability observed on ISIS is of particular interest as it is currently a main limitation on beam intensity. Good models of impedance are essential for understanding instabilities and to this end, recent beam-based measurements of the effective transverse impedance of the ISIS synchrotron are presented. This paper also presents developments of a new, in-house code to simulate the head-tail instability observed and includes benchmarks against theory and comparisons with experimental results.

Export •

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

MOPR033

Beam Acceleration and Transition Crossing in the Fermilab Booster

simulation, booster, emittance, timing

160

V.A. Lebedev, C.M. Bhat, J.-F. Ostiguy
Fermilab, Batavia, Illinois, USA

To suppress eddy currents, the Fermilab rapid cycling Booster synchrotron has no beam pipe; rather, its combined function dipoles are evacuated, exposing the beam directly to the magnet laminations. This arrangement significantly increases the resistive wall impedance of the dipoles and, in combination with the space charge impedance, substantially complicates longitudinal dynamics at transition. Voltage and accelerating phase profiles in the vicinity of transition are typically empirically optimized to minimize beam loss and emittance growth. In this contribution, we present results of experimental studies of beam acceleration near transition. Using comparisons between observed beam parameters and simulations, we obtain accurate calibrations for the RF program and extract quantitative information about parameters of relevance to the Booster laminated magnets longitudinal impedance model. The results are used to analyze transition crossing in the context of a future 50% increase in beam intensity planned for PIP-II, an upgrade of the Fermilab accelerating complex.

Poster MOPR033 [0.231 MB]

Export •

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

TUAM3X01

Identification and Reduction of the CERN SPS Impedance

emittance, flattop, vacuum, simulation

260

E.N. Shaposhnikova, T. Argyropoulos, T. Bohl, A. Lasheen, J. Repond, H. Timko
CERN, Geneva, Switzerland

The first SPS impedance reduction programme has been completed in 2001, preparing the ring for its role as an injector of the LHC. This action has eliminated microwave instability on the SPS flat bottom and later nominal beam could be delivered to the LHC. The High Luminosity (HL-) LHC project is based on beam with twice higher intensity than the nominal one. One of the important SPS intensity limitations are longitudinal instabilities with minimum threshold reached on the 450 GeV flat top. In this paper the work which was carried on to identify the impedance sources driving these instabilities is described together with the next campaign of the SPS impedance reduction planned by the LHC Injector Upgrade (LIU) project. The present knowledge of the SPS transverse impedance is also presented.

Slides TUAM3X01 [6.457 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

simulation, coupling, 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)