ICAP2012 - List of Authors (Rumolo, G.)

Paper

Title

Page

Electron Cloud Simulations with PyECLOUD

138

G. Iadarola
Naples University Federico II, Science and Technology Pole, Napoli, Italy
G. Rumolo
CERN, Geneva, Switzerland

PyECLOUD is a newly developed code for the simulation of the electron cloud (EC) build-up in particle accelerators. Almost entirely written in Python, it is mostly based on the physical models already used in the ECLOUD code but, thanks to the implementation of new optimized algorithms, it exhibits a significantly improved performance in accuracy, speed, reliability and flexibility. PyECLOUD simulations have been already broadly employed for benchmarking the EC observations in the Large Hadron Collider (LHC). Thanks to the new feature of running EC simulations with bunch-by-bunch length and intensity data from machine measurements, the “scrubbing” process of the LHC beam pipes could be reconstructed from heat load measurements in the cryogenic dipoles. In addition, PyECLOUD simulations also provide the estimation of the bunch-by-bunch energy loss, which can be compared with the measurements of the stable phase shift. They can also provide the correct EC distribution data for beam dynamics simulations with the HEADTAIL code.

Slides WESAI4 [3.466 MB]

WESCI1

EM Simulations in Beam Coupling Impedance Studies: Some Examples of Application

190

C. Zannini, G. Rumolo
CERN, Geneva, Switzerland
C. Zannini
EPFL, Lausanne, Switzerland

In the frame of the SPS upgrade an accurate impedance model is needed in order to predict the instability threshold and if necessary to start a campaign of impedance reduction. Analytical models, 3-D simulations and bench measurements are used to estimate the impedance contribution of the different devices along the machine. Special attention is devoted to the estimation of the impedance contribution of the kicker magnets that are suspected to be the most important impedance source in SPS. In particular a numerical study is carried out to analyze the effect of the serigraphy in the SPS extraction kicker. An important part of the devices simulations are the ferrite model. For this reason a numerical based method to measure the electromagnetic properties of the material has been developed to measure the ferrite properties. A simulation technique, in order to account for external cable is developed. The simulation results were benchmarked with analytical models and observations with beam. A numerical study was also performed to investigate the limits of the wire method for beam coupling impedance measurements.

Slides WESCI1 [1.571 MB]

WESCI3

Electromagnetic Characterization of Materials for the CLIC Damping Rings

198

E. Koukovini-Platia, G. De Michele, G. Rumolo
CERN, Geneva, Switzerland
C. Zannini
EPFL, Lausanne, Switzerland

The performance of the Compact Linear Collider (CLIC) damping rings (DR) is likely to be limited by collective effects due to the unprecedented brilliance of the beams. Coating will be used in both electron (EDR) and positron damping rings (PDR) to suppress effects like electron cloud formation or ion instabilities. The impedance modeling of the chambers, necessary for the instabilities studies which will ensure safe operation under nominal conditions, must include the contribution from the coating materials applied for electron cloud mitigation and/or ultra-low vacuum pressure. This advocates for a correct characterization of this impedance in a high frequency range, which is still widely unexplored. The electrical conductivity of the materials in the frequency range of few GHz is determined with the waveguide method, based on a combination of experimental measurements of the complex transmission coefficient S21 and CST 3D electromagnetic (EM) simulations.

Slides WESCI3 [2.488 MB]

THSDI2

Simulation of Multibunch Instabilities with the HEADTAIL Code

262

N. Mounet, E. Métral, G. Rumolo
CERN, Geneva, Switzerland

Multibunch instabilities due to beam-coupling impedance can be a critical limitation for synchrotrons operating with many bunches. To study these instabilities, the HEADTAIL code has been extended to simulate the motion of many bunches under the action of wake fields. All the features already present in the single-bunch version of the code have remained available, in particular synchrotron motion, chromaticity, amplitude detuning due to octupoles and the ability to load any kind of wake fields through tables. The code has been then parallelized in order to track thousands of bunches in a reasonable amount of time, showing a linear scaling with the number of processors used. We show benchmarks against Laclare's theory in simple cases, obtaining a good agreement. Results for bunch trains in the LHC and comparison with beam-based measurements are also exhibited.

Slides THSDI2 [7.278 MB]

Paper	Title	Page
WESAI4	Electron Cloud Simulations with PyECLOUD	138
	G. Iadarola Naples University Federico II, Science and Technology Pole, Napoli, Italy G. Rumolo CERN, Geneva, Switzerland
	PyECLOUD is a newly developed code for the simulation of the electron cloud (EC) build-up in particle accelerators. Almost entirely written in Python, it is mostly based on the physical models already used in the ECLOUD code but, thanks to the implementation of new optimized algorithms, it exhibits a significantly improved performance in accuracy, speed, reliability and flexibility. PyECLOUD simulations have been already broadly employed for benchmarking the EC observations in the Large Hadron Collider (LHC). Thanks to the new feature of running EC simulations with bunch-by-bunch length and intensity data from machine measurements, the “scrubbing” process of the LHC beam pipes could be reconstructed from heat load measurements in the cryogenic dipoles. In addition, PyECLOUD simulations also provide the estimation of the bunch-by-bunch energy loss, which can be compared with the measurements of the stable phase shift. They can also provide the correct EC distribution data for beam dynamics simulations with the HEADTAIL code.
	Slides WESAI4 [3.466 MB]

WESCI1	EM Simulations in Beam Coupling Impedance Studies: Some Examples of Application	190
	C. Zannini, G. Rumolo CERN, Geneva, Switzerland C. Zannini EPFL, Lausanne, Switzerland
	In the frame of the SPS upgrade an accurate impedance model is needed in order to predict the instability threshold and if necessary to start a campaign of impedance reduction. Analytical models, 3-D simulations and bench measurements are used to estimate the impedance contribution of the different devices along the machine. Special attention is devoted to the estimation of the impedance contribution of the kicker magnets that are suspected to be the most important impedance source in SPS. In particular a numerical study is carried out to analyze the effect of the serigraphy in the SPS extraction kicker. An important part of the devices simulations are the ferrite model. For this reason a numerical based method to measure the electromagnetic properties of the material has been developed to measure the ferrite properties. A simulation technique, in order to account for external cable is developed. The simulation results were benchmarked with analytical models and observations with beam. A numerical study was also performed to investigate the limits of the wire method for beam coupling impedance measurements.
	Slides WESCI1 [1.571 MB]

WESCI3	Electromagnetic Characterization of Materials for the CLIC Damping Rings	198
	E. Koukovini-Platia, G. De Michele, G. Rumolo CERN, Geneva, Switzerland C. Zannini EPFL, Lausanne, Switzerland
	The performance of the Compact Linear Collider (CLIC) damping rings (DR) is likely to be limited by collective effects due to the unprecedented brilliance of the beams. Coating will be used in both electron (EDR) and positron damping rings (PDR) to suppress effects like electron cloud formation or ion instabilities. The impedance modeling of the chambers, necessary for the instabilities studies which will ensure safe operation under nominal conditions, must include the contribution from the coating materials applied for electron cloud mitigation and/or ultra-low vacuum pressure. This advocates for a correct characterization of this impedance in a high frequency range, which is still widely unexplored. The electrical conductivity of the materials in the frequency range of few GHz is determined with the waveguide method, based on a combination of experimental measurements of the complex transmission coefficient S21 and CST 3D electromagnetic (EM) simulations.
	Slides WESCI3 [2.488 MB]

THSDI2	Simulation of Multibunch Instabilities with the HEADTAIL Code	262
	N. Mounet, E. Métral, G. Rumolo CERN, Geneva, Switzerland
	Multibunch instabilities due to beam-coupling impedance can be a critical limitation for synchrotrons operating with many bunches. To study these instabilities, the HEADTAIL code has been extended to simulate the motion of many bunches under the action of wake fields. All the features already present in the single-bunch version of the code have remained available, in particular synchrotron motion, chromaticity, amplitude detuning due to octupoles and the ability to load any kind of wake fields through tables. The code has been then parallelized in order to track thousands of bunches in a reasonable amount of time, showing a linear scaling with the number of processors used. We show benchmarks against Laclare's theory in simple cases, obtaining a good agreement. Results for bunch trains in the LHC and comparison with beam-based measurements are also exhibited.
	Slides THSDI2 [7.278 MB]