Miguel Furman - Academia.edu (original) (raw)
Papers by Miguel Furman
A replacement for the PS storage ring is being considered, in the context of the future LHC accel... more 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 ...
In studies with positron beams in the Advanced Photon Source, a dramatic amplification was observ... more 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.
We present recent simulation results for the main features of the electron cloud in the storage r... more 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.
Proceedings of the 2005 Particle Accelerator Conference
We present initial results for the self-consistent beamcloud dynamics simulations for a sample LH... more We present initial results for the self-consistent beamcloud dynamics simulations for a sample LHC beam, using a newly developed set of modeling capability based on a merge [1] of the three-dimensional parallel Particle-In-Cell (PIC) accelerator code WARP [2] and the electron-cloud code POSINST . Although the storage ring model we use as a test bed to contain the beam is much simpler and shorter than the LHC, its lattice elements are realistically modeled, as is the beam and the electron cloud dynamics. The simulated mechanisms for generation and absorption of the electrons at the walls are based on previously validated models available in POSINST .
Lawrence Berkeley National Laboratory, Jun 19, 2002
We present an update of computer simulation results for some features of the electron cloud at th... more 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.
Lawrence Berkeley National Laboratory, Jul 8, 2002
We present recent simulation results for the main features of the electron cloud in the storage r... more 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.
Lawrence Berkeley National Laboratory, 1998
We have applied our simulation code "POSINST" to evaluate, in linear approximation, the contribut... more We have applied our simulation code "POSINST" to evaluate, in linear approximation, the contribution to the growth rate of the electron-cloud instability (ECI) from the pumping sections and the dipole bending magnets in the arcs of the PEP-II positron ring. A key ingredient in our model is a detailed description of the secondary emission process off the TiN-coated chambers. Another important element is the analytic computation of the electric field produced by the beam, including the effects from surface charges. Space-charge forces of the electron cloud upon itself are also included, although these forces are negligible under nominal conditions. Bunch-length effects are optionally included by slicing the bunch into several kicks. We conclude that the growth rate is dominated by the pumping sections and scales linearly with the photoelectric yield Y . For Y = 1, our present estimate is in the range ∼ 1000 -1300 s -1 , depending upon the value of the photon reflectivity R. This is in the range controllable by the transverse feedback system. The contributions to the growth rate from other magnets and from other sections of the ring remain to be evaluated.
One of the options considered for future upgrades of the LHC injector complex entails the replace... more One of the options considered for future upgrades of the LHC injector complex entails the replacement of the PS with the PS2, a longer circumference and higher energy synchrotron. Electron cloud effects represent an important potential limitation to the achievement of the upgrade goals. We report the results of numerical studies aiming at estimating the e-cloud density thresholds for the occurrence of single bunch instabilities.
Electron clouds impose limitations on current accelera-tors that may be more severe for future ma... more Electron clouds impose limitations on current accelera-tors that may be more severe for future machines, unless adequate measures of mitigation are taken. Recently, it has been proposed to use feedback systems operating at high frequency (in the GHz range) to damp single-bunch trans-verse coherent oscillations that may otherwise be ampli-fied during the interaction of the beam with ambient elec-tron clouds. We have used the simulation package WARP-POSINST and the code Headtail to study the growth rate and frequency patterns in space-time of the electron cloud driven beam breakup instability in the CERN SPS accel-erator with, or without, an idealized feedback model for damping the instability.
We report a previously unknown resonance for electron cloud dynamics. The 2D simulation code"... more We report a previously unknown resonance for electron cloud dynamics. The 2D simulation code"POSINST" was used to study the electron cloud buildup at different z positions in the International Linear Collider positron damping ring wiggler. An electron equilibrium density enhancement of up to a factor of 3 was found at magnetic field values for which the bunch frequency is an
At PAC05[1] and PAC07[2], we presented the package WARP-POSINST for the modeling of the effect of... more At PAC05[1] and PAC07[2], we presented the package WARP-POSINST for the modeling of the effect of electron clouds on high-energy beams. We present here the latest developments in the package. Three new modes of operations were implemented: (1) a build-up mode where, similarly to POSINST (LBNL) or ECLOUD (CERN), the build-up of electron clouds driven by a legislated bunch train
Proceedings of the 2003 Bipolar/BiCMOS Circuits and Technology Meeting (IEEE Cat. No.03CH37440), 2003
We have augmented the code POSINST to include solenoid fields, and used it to simulate the build ... more We have augmented the code POSINST to include solenoid fields, and used it to simulate the build up of electron cloud due to electron multipacting in the PEP-II positron ring. We find that the distribution of electrons is strongly affected by the resonances associated with the cyclotron period and bunch spacing. In addition, we discover a threshold beyond which the electron density grows exponentially until it reaches the space charge limit. The threshold does not depend on the bunch spacing but does depend on the positron bunch population.
PACS2001. Proceedings of the 2001 Particle Accelerator Conference (Cat. No.01CH37268)
We present a first set of computer simulations for the main features of the electron cloud at the... more We present a first set of computer simulations for the main features of the electron cloud at the Proton Storage Ring (PSR), particularly its energy spectrum. We compare our results with recent measurements, which have been obtained by means of dedicated probes.
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 positr... more 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.
We present preliminary electron-cloud simulation results for the Proton Storage Ring (PSR) at LAN... more 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.
A one-dimensional model was considered to study the effects of the beam-beam force on the coheren... more A one-dimensional model was considered to study the effects of the beam-beam force on the coherent dynamics of colliding beams. The key ingredient is a linearized beam-beam kick. Only the quadrupole modes were studied, with the dynamical variables being the 2nd-order moments of the canonical variables q, p. The model is self-consistent in the sense that no higher order moments
The simulation package WARP-POSINST was recently upgraded for handling multiple bunches and model... more The simulation package WARP-POSINST was recently upgraded for handling multiple bunches and modeling concurrently the electron cloud buildup and its effect on the beam, allowing for direct self-consistent simulation of bunch trains generating, and interacting with, electron clouds. We have used the WARP-POSINST package on massively parallel supercomputers to study the buildup and interaction of electron clouds with a proton bunch train in the CERN SPS accelerator. Results suggest that a positive feedback mechanism exists between the electron buildup and the e-cloud driven transverse instability, leading to a net increase in predicted electron density. Electron clouds have been shown to trigger fast growing instabilities on proton beams circulating in the SPS and other accelerators. So far, simulations of electron cloud buildup and their effects on beam dynamics have been performed separately. This is a consequence of the large computational cost of the combined calculation due to la...
Physical Review Special Topics - Accelerators and Beams, 2003
Physical Review Special Topics - Accelerators and Beams, 2006
Physical Review Special Topics - Accelerators and Beams, 2004
We have augmented the code POSINST to include solenoid fields, and used it to simulate the build ... more We have augmented the code POSINST to include solenoid fields, and used it to simulate the build up of electron cloud due in the PEP-II positron ring. We find that the distribution of electrons is strongly affected by the resonances associated with the cyclotron period and bunch spacing. In addition, we discover a threshold beyond which the electron density grows exponentially until it reaches the space charge limit. The threshold does not depend on the bunch spacing but does depend on the positron bunch population.
A replacement for the PS storage ring is being considered, in the context of the future LHC accel... more 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 ...
In studies with positron beams in the Advanced Photon Source, a dramatic amplification was observ... more 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.
We present recent simulation results for the main features of the electron cloud in the storage r... more 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.
Proceedings of the 2005 Particle Accelerator Conference
We present initial results for the self-consistent beamcloud dynamics simulations for a sample LH... more We present initial results for the self-consistent beamcloud dynamics simulations for a sample LHC beam, using a newly developed set of modeling capability based on a merge [1] of the three-dimensional parallel Particle-In-Cell (PIC) accelerator code WARP [2] and the electron-cloud code POSINST . Although the storage ring model we use as a test bed to contain the beam is much simpler and shorter than the LHC, its lattice elements are realistically modeled, as is the beam and the electron cloud dynamics. The simulated mechanisms for generation and absorption of the electrons at the walls are based on previously validated models available in POSINST .
Lawrence Berkeley National Laboratory, Jun 19, 2002
We present an update of computer simulation results for some features of the electron cloud at th... more 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.
Lawrence Berkeley National Laboratory, Jul 8, 2002
We present recent simulation results for the main features of the electron cloud in the storage r... more 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.
Lawrence Berkeley National Laboratory, 1998
We have applied our simulation code "POSINST" to evaluate, in linear approximation, the contribut... more We have applied our simulation code "POSINST" to evaluate, in linear approximation, the contribution to the growth rate of the electron-cloud instability (ECI) from the pumping sections and the dipole bending magnets in the arcs of the PEP-II positron ring. A key ingredient in our model is a detailed description of the secondary emission process off the TiN-coated chambers. Another important element is the analytic computation of the electric field produced by the beam, including the effects from surface charges. Space-charge forces of the electron cloud upon itself are also included, although these forces are negligible under nominal conditions. Bunch-length effects are optionally included by slicing the bunch into several kicks. We conclude that the growth rate is dominated by the pumping sections and scales linearly with the photoelectric yield Y . For Y = 1, our present estimate is in the range ∼ 1000 -1300 s -1 , depending upon the value of the photon reflectivity R. This is in the range controllable by the transverse feedback system. The contributions to the growth rate from other magnets and from other sections of the ring remain to be evaluated.
One of the options considered for future upgrades of the LHC injector complex entails the replace... more One of the options considered for future upgrades of the LHC injector complex entails the replacement of the PS with the PS2, a longer circumference and higher energy synchrotron. Electron cloud effects represent an important potential limitation to the achievement of the upgrade goals. We report the results of numerical studies aiming at estimating the e-cloud density thresholds for the occurrence of single bunch instabilities.
Electron clouds impose limitations on current accelera-tors that may be more severe for future ma... more Electron clouds impose limitations on current accelera-tors that may be more severe for future machines, unless adequate measures of mitigation are taken. Recently, it has been proposed to use feedback systems operating at high frequency (in the GHz range) to damp single-bunch trans-verse coherent oscillations that may otherwise be ampli-fied during the interaction of the beam with ambient elec-tron clouds. We have used the simulation package WARP-POSINST and the code Headtail to study the growth rate and frequency patterns in space-time of the electron cloud driven beam breakup instability in the CERN SPS accel-erator with, or without, an idealized feedback model for damping the instability.
We report a previously unknown resonance for electron cloud dynamics. The 2D simulation code"... more We report a previously unknown resonance for electron cloud dynamics. The 2D simulation code"POSINST" was used to study the electron cloud buildup at different z positions in the International Linear Collider positron damping ring wiggler. An electron equilibrium density enhancement of up to a factor of 3 was found at magnetic field values for which the bunch frequency is an
At PAC05[1] and PAC07[2], we presented the package WARP-POSINST for the modeling of the effect of... more At PAC05[1] and PAC07[2], we presented the package WARP-POSINST for the modeling of the effect of electron clouds on high-energy beams. We present here the latest developments in the package. Three new modes of operations were implemented: (1) a build-up mode where, similarly to POSINST (LBNL) or ECLOUD (CERN), the build-up of electron clouds driven by a legislated bunch train
Proceedings of the 2003 Bipolar/BiCMOS Circuits and Technology Meeting (IEEE Cat. No.03CH37440), 2003
We have augmented the code POSINST to include solenoid fields, and used it to simulate the build ... more We have augmented the code POSINST to include solenoid fields, and used it to simulate the build up of electron cloud due to electron multipacting in the PEP-II positron ring. We find that the distribution of electrons is strongly affected by the resonances associated with the cyclotron period and bunch spacing. In addition, we discover a threshold beyond which the electron density grows exponentially until it reaches the space charge limit. The threshold does not depend on the bunch spacing but does depend on the positron bunch population.
PACS2001. Proceedings of the 2001 Particle Accelerator Conference (Cat. No.01CH37268)
We present a first set of computer simulations for the main features of the electron cloud at the... more We present a first set of computer simulations for the main features of the electron cloud at the Proton Storage Ring (PSR), particularly its energy spectrum. We compare our results with recent measurements, which have been obtained by means of dedicated probes.
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 positr... more 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.
We present preliminary electron-cloud simulation results for the Proton Storage Ring (PSR) at LAN... more 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.
A one-dimensional model was considered to study the effects of the beam-beam force on the coheren... more A one-dimensional model was considered to study the effects of the beam-beam force on the coherent dynamics of colliding beams. The key ingredient is a linearized beam-beam kick. Only the quadrupole modes were studied, with the dynamical variables being the 2nd-order moments of the canonical variables q, p. The model is self-consistent in the sense that no higher order moments
The simulation package WARP-POSINST was recently upgraded for handling multiple bunches and model... more The simulation package WARP-POSINST was recently upgraded for handling multiple bunches and modeling concurrently the electron cloud buildup and its effect on the beam, allowing for direct self-consistent simulation of bunch trains generating, and interacting with, electron clouds. We have used the WARP-POSINST package on massively parallel supercomputers to study the buildup and interaction of electron clouds with a proton bunch train in the CERN SPS accelerator. Results suggest that a positive feedback mechanism exists between the electron buildup and the e-cloud driven transverse instability, leading to a net increase in predicted electron density. Electron clouds have been shown to trigger fast growing instabilities on proton beams circulating in the SPS and other accelerators. So far, simulations of electron cloud buildup and their effects on beam dynamics have been performed separately. This is a consequence of the large computational cost of the combined calculation due to la...
Physical Review Special Topics - Accelerators and Beams, 2003
Physical Review Special Topics - Accelerators and Beams, 2006
Physical Review Special Topics - Accelerators and Beams, 2004
We have augmented the code POSINST to include solenoid fields, and used it to simulate the build ... more We have augmented the code POSINST to include solenoid fields, and used it to simulate the build up of electron cloud due in the PEP-II positron ring. We find that the distribution of electrons is strongly affected by the resonances associated with the cyclotron period and bunch spacing. In addition, we discover a threshold beyond which the electron density grows exponentially until it reaches the space charge limit. The threshold does not depend on the bunch spacing but does depend on the positron bunch population.