IPAC2017 - Classification: 05 Beam Dynamics and Electromagnetic Fields / D06 Coherent and Incoherent Instabilities

Paper	Title	Page
THYA1	New Scenarios of Microbunching Instability Control in Electron Linacs and Free Electron Lasers	3642
	E. Roussel, E. Allaria, M.B. Danailov, S. Di Mitri, E. Ferrari, D. Gauthier, L. Giannessi, G. Penco, M. Veronese Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
	Laser-heater systems are essential tools to control and optimize high-gain free-electron lasers (FELs) working in the x-ray wavelength range. Indeed, these systems induce a controllable increase of the energy spread of the electron bunch. The heating suppresses longitudinal microbunching instability which otherwise would limit the FEL performance. We demonstrate that, through the action of the microbunching instability, a long-wavelength modulation of the electron beam induced by the laser heater at low energy can persist until the beam entrance into the undulators. This coherent longitudinal modulation is exploited to control the FEL spectral properties, in particular, multicolor extreme-ultraviolet FEL pulses can be generated through a frequency mixing of the modulations produced by the laser heater and the seed laser in the electron beam. We present an experimental demonstration of this novel configuration carried out at the FERMI FEL. *E. Roussel et al., Phys. Rev. Lett. 115, 214801 (2015)
	Slides THYA1 [14.837 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THYA1
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THOBA1	Studies of the Micro-Bunching Instability in Multi-Bunch Operation at the ANKA Storage Ring	3645
SUSPSIK058	use link to see paper's listing under its alternate paper code
	M. Brosi, E. Blomley, E. Bründermann, M. Caselle, B. Kehrer, A. Kopmann, A.-S. Müller, L. Rota, M. Schedler, M. Schuh, M. Schwarz, P. Schönfeldt, J.L. Steinmann, M. Weber KIT, Eggenstein-Leopoldshafen, Germany
	Funding: Supported by the German Federal Ministry of Education and Research (05K13VKA & 05K16VKA), the Helmholtz Association (VH-NG-320) and the Helmholtz International Research School for Teratronics (HIRST) The test facility and synchrotron light source ANKA at the Karlsruhe Institute of Technology (KIT) operates in the energy range from 0.5 to 2.5 GeV and can generate brilliant coherent synchrotron radiation (CSR) in the THz range employing a dedicated bunch length-reducing optic at 1.3 GeV beam energy. The high degree of spatial compression leads to complex longitudinal dynamics and to time evolving sub-structures in the longitudinal phase space of the electron bunches. The results of the micro-bunching instability are time-dependent fluctuations and strong bursts in the radiated THz power. To study these fluctuations in the emitted THz radiation simultaneously for each individual bunch in a multi-bunch environment, fast THz detectors are combined with KAPTURE, the dedicated KArlsruhe Pulse Taking and Ultrafast Readout Electronics system, developed at KIT. In this contribution we present measurements conducted to study possible multi-bunch effects on the characteristic bursting behavior of the micro-bunch instability.
	Slides THOBA1 [12.910 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THOBA1
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THPAB022	Ion Instability in SuperKEKB Phase I Commissioning	3741
	K. Ohmi, H. Fukuma, Y. Suetsugu, M. Tobiyama KEK, Ibaraki, Japan
	Ion instability has been observed in SuperKEKB phase I commissioning. Unstable modes, their growth rates, tune shift were measured. Frequency of the unstable modes is slower than theoretical prediction and the growth rate is also slower. We discuss possible model to explain the measurements.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPAB022
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THPVA012	Transverse Impedance Measurement in SuperKEKB	4442
	N. Kuroo UTTAC, Tsukuba, Ibaraki, Japan T. Ishibashi, T. Mimashi, K. Ohmi, Y. Ohnishi, K. Shibata, Y. Suetsugu, S. Terui, M. Tobiyama, D. Zhou KEK, Ibaraki, Japan
	In KEK(Japan), SuperKEKB project is progressing toward upgrade. This project aims improvement luminosity (8×10³⁵ cm^-2s- 1) which is 40 times of the performance of the KEKB accelerator. In Phase 1 of this project, a performance test as storage ring was carried out. Understanding of ring Impedance/wake is an important subject in phase I. Measurement of Head Tail Damping using Turn by Turn monitor was performed to evaluate impedance/wake. Betatron motion is excited by kicker and its damping is measured for several parameters sets of bunch current and chromaticity in both HER and LER. The wake field was calculated from the decrement of betatron amplitude. We present the wake field which is cross-checked with tune shift based on the current dependence.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPVA012
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THPVA017	Integer Spin Resonance Crossing With Preserving Beam Polarization on VEPP-4M	4451
	A.K. Barladyan, A.Yu. Barnyakov, S.A. Glukhov, S.E. Karnaev, E.B. Levichev, S.A. Nikitin, I.B. Nikolaev, I.N. Okunev, P.A. Piminov, A.G. Shamov, A.N. Zhuravlev BINP SB RAS, Novosibirsk, Russia
	The method to preserve the electron beam polarization on the VEPP-4M storage ring during acceleration with crossing the integer spin resonance energy E=1763 MeV is described. It is based on the use of the non-compensated longitudinal magnetic field of the KEDR detector. This method has been successfully applied for the needs of the R measurement experiment.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPVA017
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THPVA026	Practical Stabilisation of Transverse Collective Instabilities with Second Order Chromaticity in the LHC	4477
SUSPSIK059	use link to see paper's listing under its alternate paper code
	M. Schenk, D. Amorim, N. Biancacci, X. Buffat, L.R. Carver, R. De Maria, K.S.B. Li, E. Métral, B. Salvant CERN, Geneva, Switzerland
	The study reports on dedicated measurements made with a single nominal bunch in the LHC at 6.5 TeV. First, we show that a significant amount of second order chromaticity Q'' can be introduced in the machine in a well-controlled manner. Second, we demonstrate that the incoherent betatron tune spread from Q'' can provide beam stability through the Landau damping mechanism. This is a first step in the development of a Q'' knob to be potentially applied during regular physics operation in the LHC.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPVA026
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THPVA028	Multi-Bunch Instabilities Measurement and Analysis at the Diamond Light Source	4485
	R. Bartolini, R.T. Fielder, E. Koukovini-Platia, G. Rehm DLS, Oxfordshire, United Kingdom
	The characterisation of the multi-bunch dynamics at the Diamond light source is performed with an advanced TMBF system that is capable of operating fast grow damp experiments thus allowing the exploration of many machine conditions. We report here the latest results of the measurement campaign, the implication on the machine impedance model and some of the intricacies of the analysis and interpretation of the experimental data.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPVA028
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THPVA029	Study of Single Bunch Instabilities with Transverse Feedback at Diamond	4489
	E. Koukovini-Platia, R. Bartolini, A.F.D. Morgan, G. Rehm DLS, Oxfordshire, United Kingdom R. Bartolini JAI, Oxford, United Kingdom
	Single bunch instability studies have been carried out at Diamond with and without the transverse multi-bunch feedback (TMBF) system. Single bunch instability thresholds were measured for zero, positive and negative chromaticity values by increasing the current till the instability onset. The bunch-by-bunch feedback system was then used to suppress the motion of the bunch centroid and the new thresholds were measured in all chromaticity regimes. The feedback loop phase of the TMBF was changed from resistive to reactive as well as intermediate to find the optimal feedback settings that maximize the single bunch instability thresholds.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPVA029
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THPVA030	Collective Effects Studies of the Double-Double Bend Achromat Cell at Diamond	4493
	E. Koukovini-Platia, R. Bartolini, L.M. Bobb, R.T. Fielder DLS, Oxfordshire, United Kingdom R. Bartolini JAI, Oxford, United Kingdom
	One cell of the Diamond storage ring has been converted from a double bend achromat to a double-double bend achromat (DDBA). After the successful installation and beam commissioning in November 2016, beam-based studies were done to assess the effect of the new cell on the single bunch and multi-bunch instabilities both in transverse and longitudinal planes. These are compared with the impedance estimate carried out both numerically and analytically.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPVA030
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THPVA031	Beam Tests of Diamond-Like Carbon Coating for Mitigation of Electron Cloud	4497
	J.S. Eldred, M. Backfish, C.-Y. Tan, R.M. Zwaska Fermilab, Batavia, Illinois, USA S. Kato KEK, Ibaraki, Japan
	Electron cloud beam instabilities are an important consideration in virtually all high-energy particle accelerators and could pose a formidable challenge to forthcoming high-intensity accelerator upgrades. Our results evaluate the efficacy of a diamond-like carbon (DLC) coating for the mitigation of electron in the Fermilab Main Injector. The interior surface of the beampipe conditions in response to electron bombardment from the electron cloud and we track the change in electron cloud flux over time in the DLC coated beampipe and uncoated stainless steel beampipe. The electron flux is measured by retarding field analyzers placed in a field-free region of the Main Injector. We find the DLC coating reduces the electron cloud signal to roughly 2\% of that measured in the uncoated stainless steel beampipe.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPVA031
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THPVA034	Comparison of the Coupling of Dipole Motion From Bunch to Bunch in an Electron Beam Caused by Electron Clouds at CesrTA Due to Variations in Bunch Length and Chromaticity	4509
	M.G. Billing, L.Y. Bartnik, J.A. Crittenden, M.J. Forster, N.T. Rider, J.P. Shanks, M.B. Spiegel, S. Wang Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA R. Holtzapple CalPoly, San Luis Obispo, California, USA E.C. Runburg University of Notre Dame, Indiana, USA
	Earlier experiments at the Cornell Electron-Positron Storage Ring Test Accelerator (CesrTA) have probed the interaction of the electron cloud (EC) with a 2.1 GeV stored positron beam. Since a very low EC density is expected with the electron bunches, these results characterize the dependence of beam-vacuum chamber impedance interactions, which are common to both positron and electron beams. The experiments were performed on a 30-bunch electron train with a 14 ns spacing, at a fixed current of 0.75mA/bunch, at two different vertical chromaticity settings and for four different bunch lengths (or synchrotron tunes.) The beam dynamics of the stored beam, in the presence of the electron cloud, was quantified using: 20 turn-by-turn beam position monitors in CESR to measure the correlated bunch-by-bunch dipole motion and an x-ray beam size monitor to record the bunch-by-bunch, turn-by-turn vertical size of each bunch within the trains. In this paper we report on the analysis of the observations from these experiments and compare them with effects of the EC on the positron beam's dipole motion and coupling of the motion from each bunch to its succeeding bunches.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPVA034
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THPVA035	Dependence of the Coupling of Dipole Motion From Bunch to Bunch Caused by Electron Clouds at CesrTA Due to Variations in Bunch Length and Chromaticity	4512
	M.G. Billing, L.Y. Bartnik, J.A. Crittenden, M.J. Forster, N.T. Rider, J.P. Shanks, M.B. Spiegel, S. Wang Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA R. Holtzapple CalPoly, San Luis Obispo, California, USA E.C. Runburg University of Notre Dame, Indiana, USA
	The Cornell Electron-Positron Storage Ring Test Accelerator (CesrTA) has conducted experiments to probe the interaction of the electron cloud (EC) with a 2.1 GeV stored positron beam. These experiments investigate the dependence of beam'electron cloud interactions vs. bunch length (or synchrotron tune) at two values of the vertical chromaticity. The experiments utilized a 30-bunch positron train with a 14 ns spacing, at a fixed current of 0.75mA/bunch. The beam dynamics of the stored beam, in the presence of the electron cloud, was quantified using: 20 turn-by-turn beam position monitors in CESR to measure the correlated bunch-by-bunch dipole motion and an x-ray beam size monitor to record the bunch-by-bunch, turn-by-turn vertical size of each bunch within the trains. In this paper we report on the observations from these experiments and a more detailed analysis for the coupling of dipole motion via the EC from each bunch to succeeding bunches in the train.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPVA035
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Paper

Title

Page

New Scenarios of Microbunching Instability Control in Electron Linacs and Free Electron Lasers

3642

E. Roussel, E. Allaria, M.B. Danailov, S. Di Mitri, E. Ferrari, D. Gauthier, L. Giannessi, G. Penco, M. Veronese
Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy

Laser-heater systems are essential tools to control and optimize high-gain free-electron lasers (FELs) working in the x-ray wavelength range. Indeed, these systems induce a controllable increase of the energy spread of the electron bunch. The heating suppresses longitudinal microbunching instability which otherwise would limit the FEL performance. We demonstrate that, through the action of the microbunching instability, a long-wavelength modulation of the electron beam induced by the laser heater at low energy can persist until the beam entrance into the undulators. This coherent longitudinal modulation is exploited to control the FEL spectral properties, in particular, multicolor extreme-ultraviolet FEL pulses can be generated through a frequency mixing of the modulations produced by the laser heater and the seed laser in the electron beam. We present an experimental demonstration of this novel configuration carried out at the FERMI FEL.
*E. Roussel et al., Phys. Rev. Lett. 115, 214801 (2015)

Slides THYA1 [14.837 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THYA1

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THOBA1

Studies of the Micro-Bunching Instability in Multi-Bunch Operation at the ANKA Storage Ring

3645

SUSPSIK058

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

M. Brosi, E. Blomley, E. Bründermann, M. Caselle, B. Kehrer, A. Kopmann, A.-S. Müller, L. Rota, M. Schedler, M. Schuh, M. Schwarz, P. Schönfeldt, J.L. Steinmann, M. Weber
KIT, Eggenstein-Leopoldshafen, Germany

Funding: Supported by the German Federal Ministry of Education and Research (05K13VKA & 05K16VKA), the Helmholtz Association (VH-NG-320) and the Helmholtz International Research School for Teratronics (HIRST)
The test facility and synchrotron light source ANKA at the Karlsruhe Institute of Technology (KIT) operates in the energy range from 0.5 to 2.5 GeV and can generate brilliant coherent synchrotron radiation (CSR) in the THz range employing a dedicated bunch length-reducing optic at 1.3 GeV beam energy. The high degree of spatial compression leads to complex longitudinal dynamics and to time evolving sub-structures in the longitudinal phase space of the electron bunches. The results of the micro-bunching instability are time-dependent fluctuations and strong bursts in the radiated THz power. To study these fluctuations in the emitted THz radiation simultaneously for each individual bunch in a multi-bunch environment, fast THz detectors are combined with KAPTURE, the dedicated KArlsruhe Pulse Taking and Ultrafast Readout Electronics system, developed at KIT. In this contribution we present measurements conducted to study possible multi-bunch effects on the characteristic bursting behavior of the micro-bunch instability.

Slides THOBA1 [12.910 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THOBA1

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THPAB022

Ion Instability in SuperKEKB Phase I Commissioning

3741

K. Ohmi, H. Fukuma, Y. Suetsugu, M. Tobiyama
KEK, Ibaraki, Japan

Ion instability has been observed in SuperKEKB phase I commissioning. Unstable modes, their growth rates, tune shift were measured. Frequency of the unstable modes is slower than theoretical prediction and the growth rate is also slower. We discuss possible model to explain the measurements.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPAB022

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THPVA012

Transverse Impedance Measurement in SuperKEKB

4442

N. Kuroo
UTTAC, Tsukuba, Ibaraki, Japan
T. Ishibashi, T. Mimashi, K. Ohmi, Y. Ohnishi, K. Shibata, Y. Suetsugu, S. Terui, M. Tobiyama, D. Zhou
KEK, Ibaraki, Japan

In KEK(Japan), SuperKEKB project is progressing toward upgrade. This project aims improvement luminosity (8×10³⁵ cm^-2s- 1) which is 40 times of the performance of the KEKB accelerator. In Phase 1 of this project, a performance test as storage ring was carried out. Understanding of ring Impedance/wake is an important subject in phase I. Measurement of Head Tail Damping using Turn by Turn monitor was performed to evaluate impedance/wake. Betatron motion is excited by kicker and its damping is measured for several parameters sets of bunch current and chromaticity in both HER and LER. The wake field was calculated from the decrement of betatron amplitude. We present the wake field which is cross-checked with tune shift based on the current dependence.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPVA012

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THPVA017

Integer Spin Resonance Crossing With Preserving Beam Polarization on VEPP-4M

4451

A.K. Barladyan, A.Yu. Barnyakov, S.A. Glukhov, S.E. Karnaev, E.B. Levichev, S.A. Nikitin, I.B. Nikolaev, I.N. Okunev, P.A. Piminov, A.G. Shamov, A.N. Zhuravlev
BINP SB RAS, Novosibirsk, Russia

The method to preserve the electron beam polarization on the VEPP-4M storage ring during acceleration with crossing the integer spin resonance energy E=1763 MeV is described. It is based on the use of the non-compensated longitudinal magnetic field of the KEDR detector. This method has been successfully applied for the needs of the R measurement experiment.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPVA017

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THPVA026

Practical Stabilisation of Transverse Collective Instabilities with Second Order Chromaticity in the LHC

4477

SUSPSIK059

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

M. Schenk, D. Amorim, N. Biancacci, X. Buffat, L.R. Carver, R. De Maria, K.S.B. Li, E. Métral, B. Salvant
CERN, Geneva, Switzerland

The study reports on dedicated measurements made with a single nominal bunch in the LHC at 6.5 TeV. First, we show that a significant amount of second order chromaticity Q'' can be introduced in the machine in a well-controlled manner. Second, we demonstrate that the incoherent betatron tune spread from Q'' can provide beam stability through the Landau damping mechanism. This is a first step in the development of a Q'' knob to be potentially applied during regular physics operation in the LHC.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPVA026

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THPVA028

Multi-Bunch Instabilities Measurement and Analysis at the Diamond Light Source

4485

R. Bartolini, R.T. Fielder, E. Koukovini-Platia, G. Rehm
DLS, Oxfordshire, United Kingdom

The characterisation of the multi-bunch dynamics at the Diamond light source is performed with an advanced TMBF system that is capable of operating fast grow damp experiments thus allowing the exploration of many machine conditions. We report here the latest results of the measurement campaign, the implication on the machine impedance model and some of the intricacies of the analysis and interpretation of the experimental data.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPVA028

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THPVA029

Study of Single Bunch Instabilities with Transverse Feedback at Diamond

4489

E. Koukovini-Platia, R. Bartolini, A.F.D. Morgan, G. Rehm
DLS, Oxfordshire, United Kingdom
R. Bartolini
JAI, Oxford, United Kingdom

Single bunch instability studies have been carried out at Diamond with and without the transverse multi-bunch feedback (TMBF) system. Single bunch instability thresholds were measured for zero, positive and negative chromaticity values by increasing the current till the instability onset. The bunch-by-bunch feedback system was then used to suppress the motion of the bunch centroid and the new thresholds were measured in all chromaticity regimes. The feedback loop phase of the TMBF was changed from resistive to reactive as well as intermediate to find the optimal feedback settings that maximize the single bunch instability thresholds.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPVA029

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THPVA030

Collective Effects Studies of the Double-Double Bend Achromat Cell at Diamond

4493

E. Koukovini-Platia, R. Bartolini, L.M. Bobb, R.T. Fielder
DLS, Oxfordshire, United Kingdom
R. Bartolini
JAI, Oxford, United Kingdom

One cell of the Diamond storage ring has been converted from a double bend achromat to a double-double bend achromat (DDBA). After the successful installation and beam commissioning in November 2016, beam-based studies were done to assess the effect of the new cell on the single bunch and multi-bunch instabilities both in transverse and longitudinal planes. These are compared with the impedance estimate carried out both numerically and analytically.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPVA030

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THPVA031

Beam Tests of Diamond-Like Carbon Coating for Mitigation of Electron Cloud

4497

J.S. Eldred, M. Backfish, C.-Y. Tan, R.M. Zwaska
Fermilab, Batavia, Illinois, USA
S. Kato
KEK, Ibaraki, Japan

Electron cloud beam instabilities are an important consideration in virtually all high-energy particle accelerators and could pose a formidable challenge to forthcoming high-intensity accelerator upgrades. Our results evaluate the efficacy of a diamond-like carbon (DLC) coating for the mitigation of electron in the Fermilab Main Injector. The interior surface of the beampipe conditions in response to electron bombardment from the electron cloud and we track the change in electron cloud flux over time in the DLC coated beampipe and uncoated stainless steel beampipe. The electron flux is measured by retarding field analyzers placed in a field-free region of the Main Injector. We find the DLC coating reduces the electron cloud signal to roughly 2\% of that measured in the uncoated stainless steel beampipe.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPVA031

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THPVA034

Comparison of the Coupling of Dipole Motion From Bunch to Bunch in an Electron Beam Caused by Electron Clouds at CesrTA Due to Variations in Bunch Length and Chromaticity

4509

M.G. Billing, L.Y. Bartnik, J.A. Crittenden, M.J. Forster, N.T. Rider, J.P. Shanks, M.B. Spiegel, S. Wang
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
R. Holtzapple
CalPoly, San Luis Obispo, California, USA
E.C. Runburg
University of Notre Dame, Indiana, USA

Earlier experiments at the Cornell Electron-Positron Storage Ring Test Accelerator (CesrTA) have probed the interaction of the electron cloud (EC) with a 2.1 GeV stored positron beam. Since a very low EC density is expected with the electron bunches, these results characterize the dependence of beam-vacuum chamber impedance interactions, which are common to both positron and electron beams. The experiments were performed on a 30-bunch electron train with a 14 ns spacing, at a fixed current of 0.75mA/bunch, at two different vertical chromaticity settings and for four different bunch lengths (or synchrotron tunes.) The beam dynamics of the stored beam, in the presence of the electron cloud, was quantified using: 20 turn-by-turn beam position monitors in CESR to measure the correlated bunch-by-bunch dipole motion and an x-ray beam size monitor to record the bunch-by-bunch, turn-by-turn vertical size of each bunch within the trains. In this paper we report on the analysis of the observations from these experiments and compare them with effects of the EC on the positron beam's dipole motion and coupling of the motion from each bunch to its succeeding bunches.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPVA034

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

THPVA035

Dependence of the Coupling of Dipole Motion From Bunch to Bunch Caused by Electron Clouds at CesrTA Due to Variations in Bunch Length and Chromaticity

4512

M.G. Billing, L.Y. Bartnik, J.A. Crittenden, M.J. Forster, N.T. Rider, J.P. Shanks, M.B. Spiegel, S. Wang
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
R. Holtzapple
CalPoly, San Luis Obispo, California, USA
E.C. Runburg
University of Notre Dame, Indiana, USA

The Cornell Electron-Positron Storage Ring Test Accelerator (CesrTA) has conducted experiments to probe the interaction of the electron cloud (EC) with a 2.1 GeV stored positron beam. These experiments investigate the dependence of beam'electron cloud interactions vs. bunch length (or synchrotron tune) at two values of the vertical chromaticity. The experiments utilized a 30-bunch positron train with a 14 ns spacing, at a fixed current of 0.75mA/bunch. The beam dynamics of the stored beam, in the presence of the electron cloud, was quantified using: 20 turn-by-turn beam position monitors in CESR to measure the correlated bunch-by-bunch dipole motion and an x-ray beam size monitor to record the bunch-by-bunch, turn-by-turn vertical size of each bunch within the trains. In this paper we report on the observations from these experiments and a more detailed analysis for the coupling of dipole motion via the EC from each bunch to succeeding bunches in the train.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPVA035

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