Measurement of electron trapping in the Cornell Electron Storage Ring

Billing, M.; Conway, Joseph; Cowan, E. E.; Crittenden, J.; Hartung, W.; Lanzoni, J.; Li, Y.; Shill, C. S.; Sikora, J.; Sonnad, K.

doi:10.1103/physrevstab.18.041001

Cited by 12 publications

(11 citation statements)

References 16 publications

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“…Conversely in the quadrupole magnets, which constitute about 7% of the LHC ring, simulations were initialized using the electron distribution as produced by the buildup code. In fact, due to the trapping effects from the magnetic field gradient [26], the EC pinch dynamics is very sensitive to the initial phase space distribution of electrons. More details can be found in [27].…”

Section: Simulation Resultsmentioning

confidence: 99%

Electron cloud buildup driving spontaneous vertical instabilities of stored beams in the Large Hadron Collider

Romano

Buffat

Iadarola

et al. 2018

Phys. Rev. Accel. Beams

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At the beginning of the 2016 run, an anomalous beam instability was systematically observed at the CERN Large Hadron Collider (LHC). Its main characteristic was that it spontaneously appeared after beams had been stored for several hours in collision at 6.5 TeV to provide data for the experiments, despite large chromaticity values and high strength of the Landau-damping octupole magnet. The instability exhibited several features characteristic of those induced by the electron cloud (EC). Indeed, when LHC operates with 25 ns bunch spacing, an EC builds up in a large fraction of the beam chambers, as revealed by several independent indicators. Numerical simulations have been carried out in order to investigate the role of the EC in the observed instabilities. It has been found that the beam intensity decay is unfavorable for the beam stability when LHC operates in a strong EC regime.

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Section: Simulation Resultsmentioning

confidence: 99%

Electron cloud buildup driving spontaneous vertical instabilities of stored beams in the Large Hadron Collider

Romano

Buffat

Iadarola

et al. 2018

Phys. Rev. Accel. Beams

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“…[5] • The study of the effects on the stored positron beam due to electron clouds (EC), produced by synchrotron radiation-induced photoelectrons. The goal is to 1) characterize and quantify the production mechanisms, 2) compare these with computer simulations, 3) develop methods to mitigate the EC effects, [6][7][8] and 4) study the related beam dynamics and instabilities. [9] • The measurement and characterization of the intra-beam beam scattering effects as they lead to emittance enlargement.…”

Section: Introduction and Overviewmentioning

confidence: 99%

Instrumentation for the study of low emittance tuning and beam dynamics at CESR

et al. 2017

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A: The Cornell Electron-positron Storage Ring (CESR) has been converted from a High Energy Physics electron-positron collider to operate as a dedicated synchrotron light source for the Cornell High Energy Synchrotron Source (CHESS) and to conduct accelerator physics research as a test accelerator, capable of studying topics relevant to future damping rings, colliders and light sources. Some of the specific topics that were targeted for the initial phase of operation of the storage ring in this mode for CESR as a Test Accelerator (CesrTA) included 1) tuning techniques to produce low emittance beams, 2) the study of electron cloud development in a storage ring and 3) intra-beam scattering effects. The complete conversion of CESR to CesrTA occurred over a several year period, described elsewhere [1][2][3]. In addition to instrumentation for the storage ring, which was created for CesrTA, existing instrumentation was modified to facilitate the entire range of investigations to support these studies. Procedures were developed, often requiring coordinated measurements among different instruments [4]. This paper describes the instruments utilized for the study of beam dynamics during the operation of CesrTA. The treatment of these instruments will remain fairly general in this paper as it focusses on an overview of the instruments themselves. Their interaction and inter-relationships during sequences of observations is found in a companion paper describing the associated measurement techniques. More detailed descriptions and detailed operational performance for some of the instrumentation may be found elsewhere and these will be referenced in the related sections of this paper.

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“…The secondary electrons, created in the process, will eventually reach the vacuum chamber and be absorbed. This clearing bunch can be used to indicate the presence of the electron cloud [8] or to bring the electron cloud density below the threshold, stabilizing the beam.…”

Section: Electron Cloud Trappingmentioning

confidence: 99%

“…We used a clearing bunch technique, similar to that used at Cornell [8], to check whether the instability is caused by a trapped electron cloud. If a trapped electron cloud is present in the machine, a single bunch of high enough charge following the main batch will kick it and clear the aperture.…”

Section: Witness Bunch Experimentsmentioning

confidence: 99%

Fast instability caused by electron cloud in combined function magnets

Antipov

Adamson

Burov

et al. 2017

Phys. Rev. Accel. Beams

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One of the factors which may limit the intensity in the Fermilab Recycler is a fast transverse instability. It develops within a hundred turns and, in certain conditions, may lead to a beam loss. The high rate of the instability suggests that its cause is electron cloud. We studied the phenomena by observing the dynamics of stable and unstable beams, simulating numerically the buildup of the electron cloud, and developed an analytical model of an electron cloud driven instability with the electrons trapped in combined function dipoles. We found that beam motion can be stabilized by a clearing bunch, which confirms the electron cloud nature of the instability. The clearing suggest electron cloud trapping in Recycler combined function magnets. Numerical simulations show that up to 1% of the particles can be trapped by the magnetic field. Since the process of electron cloud buildup is exponential, once trapped this amount of electrons significantly increases the density of the cloud on the next revolution. In a Recycler combined function dipole this multiturn accumulation allows the electron cloud to reach final intensities orders of magnitude greater than in a pure dipole. The estimated resulting instability growth time of about 30 revolutions and the mode frequency of 0.4 MHz are consistent with experimental observations and agree with the simulation in the PEI code. The created instability model allows investigating the beam stability for the future intensity upgrades.

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Measurement of electron trapping in the Cornell Electron Storage Ring

Cited by 12 publications

References 16 publications

Electron cloud buildup driving spontaneous vertical instabilities of stored beams in the Large Hadron Collider

Electron cloud buildup driving spontaneous vertical instabilities of stored beams in the Large Hadron Collider

Instrumentation for the study of low emittance tuning and beam dynamics at CESR

Fast instability caused by electron cloud in combined function magnets

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