Simulation results for the electron cloud at the PSR (original) (raw)

Electron Cloud Updated Simulation Results for the PSR, and Recent Results for the SNS

2002

We present recent simulation results for the main features of the electron cloud in the storage ring of the Spallation Neutron Source (SNS) at Oak Ridge, and updated results for the Proton Storage Ring (PSR) at Los Alamos. In particular, a complete refined model for the secondary emission process including the so called true secondary, rediffused and backscattered electrons has been included in the simulation code.

Electron-cloud simulation results for the PSR and SNS

Lawrence Berkeley National Laboratory, 2002

A preliminary comparative study of the electron-cloud effect for the PSR, ISIS, and the ESS

2003

We present preliminary electron-cloud simulation results for the Proton Storage Ring (PSR) at LANL, the ISIS synchrotron at RAL, and the European Spallation Source (ESS). For each machine, we simulate the build-up and dissipation of the electron cloud (EC) in a representative field-free section of the vacuum chamber. For all three cases, we choose the same residual gas temperature, secondary emission yield (SEY), and secondary emission spectrum. Other variables such as proton loss rate, bunch profile, intensity and energy, residual gas pressure and chamber geometry, are set at the corresponding values for each machine. Under these assumptions, we conclude that, of the three machines, the PSR is the most severely affected by the electron cloud effect (ECE), followed by the ESS, with ISIS in third place. We illustrate a strong sensitivity of the ECE to the longitudinal bunch profile by choosing two different shapes for the case of the PSR, and a weak sensitivity to residual gas pressure and proton loss rate. This preliminary study does not address the ECE in other regions of the machine, nor the beam instability that might arise from the EC.

Electron cloud development in the Proton Storage Ring and in the Spallation Neutron Source

Physical Review Special Topics - Accelerators and Beams, 2003

We have applied our simulation code POSINST to evaluate the contribution to the growth rate of the electron cloud instability in proton storage rings. In particular, we present here recent simulation results for the main features of the electron cloud in the storage ring of the Spallation Neutron Source at Oak Ridge, and updated results for the Proton Storage Ring at Los Alamos. A key ingredient in our model is a detailed description of the secondary electron emission process, including a refined model for the emitted energy spectrum, and for the three main components of the secondary yield, namely, the true secondary, rediffused and backscattered components.

Electron-cloud Build-up Simulations in the Proposed PS2: Status Report

2010

A replacement for the PS storage ring is being considered, in the context of the future LHC accelerator complex upgrade, that would likely place the new machine (the PS2) in a regime where the electron-cloud (EC) effect might be an operational limitation. We report here our present understanding of the ECE build-up based on simulations. We focus our attention on the bending magnets and the field-free regions, and consider both proposed bunch spacings of 25 and 50 ns. The primary model parameters exercised are the peak secondary emission yield (SEY) delta_{m}ax, and the electron-wall impact energy at which SEY peaks, E_{m}ax. By choosing reasonable values for such quantities, and exploring variations around them, we estimate the range for the EC density n_{e} to be expected in nominal operation. We present most of our results as a function of bunch intensity N_{b}, and we provide a tentative explanation for a curious non-monotonic behavior of n_{e} as a function of N_{b}. We explore ...

Electron-cloud simulation results for the SPS and recent results for the LHC

Lawrence Berkeley National Laboratory, 2002

We present an update of computer simulation results for some features of the electron cloud at the Large Hadron Collider (LHC) and recent simulation results for the Super Proton Synchrotron (SPS). We focus on the sensitivity of the power deposition on the LHC beam screen to the emitted electron spectrum, which we study by means of a refined secondary electron (SE) emission model recently included in our simulation code.

ELECTRON CLOUD STUDIES FOR THE UPGRADE OF THE CERN PS

The observation of a significant dynamic pressure rise as well as measurements with dedicated detectors indicate that an electron cloud develops in the CERN PS during the last stages of the RF manipulations for the production of LHC type beams, especially with 25 ns bunch spacing. Although presently these beams are not degraded by the interaction with the electron cloud, which develops only during few milliseconds before extraction, the question if this effect could degrade the future high intensity and high brightness beams foreseen by the LHC Injectors Upgrade project is still open. Therefore several studies are being carried out employing both simulations and measurements with the electron cloud detectors in the machine. The aim is to develop a reliable electron cloud model of the PS vacuum chambers in order to identify possible future limitations and find suitable countermeasures.

Electron-cloud measurements and simulations for the APS

PACS2001. Proceedings of the 2001 Particle Accelerator Conference (Cat. No.01CH37268)

We compare experimental results with simulations of the electron cloud effect induced by a positron beam at the APS synchrotron light source at ANL, where the electron cloud effect has been observed and measured with dedicated probes. We find good agreement between simulations and measurements for reasonable values of certain secondary electron yield (SEY) parameters, most of which were extracted from recent bench measurements at SLAC.

Head-Tail Instability Caused by Electron Clouds in Positron Storage Rings

Physical Review Letters, 2000

In positron or proton storage rings with many closely spaced bunches, an electron cloud can build up in the vacuum chamber due to photoemission or secondary emission. We discuss the possibility of a single-bunch two-stream instability driven by this electron cloud. Depending on the strength of the beam-electron interaction, the chromaticity and the synchrotron oscillation frequency, this instability either resembles a linac beam breakup or a head-tail instability. We present computer simulations of the instabilities, and compare the simulation results with analytical estimates.

Electron cloud effects in the CERN PS

PACS2001. Proceedings of the 2001 Particle Accelerator Conference (Cat. No.01CH37268), 2001

The beam-induced electron cloud build-up is one of the major concerns for the SPS and the design of the future LHC. Recently, this effect has been observed also in the PS with the nominal LHC-type beam, consisting of a batch of 72 bunches of 1.110 11 p/b spaced by 25 ns. The electron cloud induces baseline distortion in electrostatic pickup signals that is observed, both in the last turns of the PS when the full bunch length is reduced to less than 4 ns, and in the transfer line between the PS and the SPS rings. Experimental observations are presented and compared to simulation results and predictions from theory. Furthermore, possible cures, such as variation of the bunch spacing, inserting gaps in the bunch train and applying weak solenoidal fields, are also discussed.

Summary of CERN-GSI Workshop on Electron Cloud

The bilateral CERN-GSI Electron Cloud Workshop was organized with the main goal to review the status of CERN and GSI electron cloud studies in order to find synergies between the two laboratories and to define a common strategy for future developments in terms of simulation tools, diagnostics and mitigation techniques. The workshop took place on 7–8 March 2011 at CERN (BE Auditorium) and welcomed 30 registered participants coming from CERN, GSI, INFN-LNF, KEK, CELLS, CINVESTAV, TUD, and several other institutes. It was supported by CERN and GSI, and sponsored by the European Commission under the FP7 “Research Infrastructures” project EuCARD (grant agreement no.227579), work package “Accelerator Science Networks” (AccNet).

Simulations of Electron Cloud Build Up and Saturation in the APS

2002

In studies with positron beams in the Advanced Photon Source, a dramatic amplification was observed in the electron cloud for certain bunch current and bunch spacings. In modeling presented previously, we found qualitative agreement with the observed beam-induced multipacting condition, provided reasonable values were chosen for the secondary electron yield parameters, including the energy distribution. In this paper, we model and discuss the build-up and saturation process observed over long bunch trains at the resonance condition. Understanding this saturation mechanism in more detail may have implications for predicting electron cloud amplification, multipacting, and instabilities in future rings.

Simulation of Head-Tail Instability Caused by Electron Cloud in the Positron Ring at PEP-II

2002

The head-tail instability caused by an electron cloud in positron storage rings is studied numerically using a simple model. In the model, the positron beam is longitudinally divided into many slices that have a fixed transverse size. The centroid of each slice evolves dynamically according to the interaction with a two-dimensional electron cloud at a given azimuthal location in the ring and a six-dimensional lattice map. A sudden and huge increase of the projected beam size and the mode coupling in the dipole spectrum are observed in the simulation at the threshold of the instability. Even below the threshold, the vertical beam size increases along a bunch train that has 8.5 ns bunch spacing. Above the threshold, a positive chromaticity can damp down the centroid motion but has very little effect on the blowup of the beam size. The results of the simulation are consistent with many observations at PEP-II.

SPARC experiments at the high-energy storage ring

Physica Scripta, 2013

The physics program of the SPARC collaboration at the Facility for Antiproton and Ion Research (FAIR) focuses on the study of collision phenomena in strong and even extreme electromagnetic fields and on the fundamental interactions between electrons and heavy nuclei up to bare uranium. Here we give a short overview on the challenging physics opportunities of the high-energy storage ring at FAIR for future experiments with heavy-ion beams at relativistic energies with particular emphasis on the basic beam properties to be expected.

Experimental Investigations of the Electron Cloud Key Parameters

1999

Motivated by a potential electron cloud instability and the possible existence of electron mulitpacting in the LHC vacuum system, that may result in additional gas desorption and unmanageable heat loads on the cryogenic system, an extensive experimental research program is underway at CERN to quantify the key parameters driving these phenomena. Parameters, such as: photoelectron yield, photon reflectivity, secondary electron

Atomic physics at the Heidelberg Test Storage Ring (TSR)

Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 1987

A brief description of the Heavy-Ion Test Storage Ring (TSR) presently being built at the Max-Planck Institut in Heidelberg is given. It will be able to store ions injected from the tandem postaccelerator combination up to-30 MeV/nucleon for a charge to mass ratio of 0.5. One of the main purposes of the TSR will be the study of electron cooling. Some atomic physics experiments are discussed using the electron cooling device which provides an electron-ion collision facility with good energy resolution and ion beams of high currents and low emittances. Here the possibilities for measurements of spontaneous and laser-induced radiative recombination and dielectronic recombination in the electron cooling section are discussed.

Electron cloud buildup and instability: Numerical simulations for the CERN Proton Synchrotron

Physical Review Special Topics - Accelerators and Beams, 2003

Experimental observations on the electron cloud have been collected at the CERN Proton Synchrotron machine throughout the last two years. At the same time, an intense campaign of simulations has been carried out to understand the observed electron cloud buildup and the related instability. In this paper, the results of the numerical simulations are presented and discussed.

Investigation into electron cloud effects in the International Linear Collider positron damping ring

Physical Review Special Topics - Accelerators and Beams, 2014

We report modeling results for electron cloud buildup and instability in the International Linear Collider positron damping ring. Updated optics, wiggler magnets, and vacuum chamber designs have recently been developed for the 5 GeV, 3.2-km racetrack layout. An analysis of the synchrotron radiation profile around the ring has been performed, including the effects of diffuse and specular photon scattering on the interior surfaces of the vacuum chamber. The results provide input to the cloud buildup simulations for the various magnetic field regions of the ring. The modeled cloud densities thus obtained are used in the instability threshold calculations. We conclude that the mitigation techniques employed in this model will suffice to allow operation of the damping ring at the design operational specifications.