IPAC2012 - List of Authors (Li, K.S.B.)

Paper	Title	Page
MOPPC075	A Generic Data Model for HeadTail: Design and Implementation with Examples	307
	K.S.B. Li, G. Rumolo CERN, Geneva, Switzerland
	HeadTail has been developed in 2002 for the efficient simulation of instabilities and collective effects in large circular accelerators. Since then, the capabilities of the code have been continuously extended and the output data has become increasingly complex and large-scale ranging from the statistical description of single bunches to the statistical description of all slices within bunches up to the dynamics of the full 6D phase space over several thousands of turns. Processing this data in an effective manner and endowing it with a structure that provides a physical concept calls for new and optimised data formats. To meet state-of-the-art standards, the hierarchical data format (HDF5) has been selected as native output data format together with H5Part and XDMF as native data structures. We describe the implementation of the H5Part and the XDMF data structures into HeadTail and show some illustrative examples for data processing.

WEPPR068	Mitigation of Electron Cloud Instabilities in the LHC Using Sextupoles and Octupoles	3084
	K.S.B. Li, G. Rumolo CERN, Geneva, Switzerland
	Coherent electron cloud instabilities pose a serious limitation for luminosity upgrades in the Large Hadron Collider (LHC) at CERN. In particular, when bunch spacings reach below 50 ns, electron cloud formation is enhanced which in turn drives beam instabilities. The beam can be stabilised by shifting the tune and by increasing the tune spread using sextupoles or octupoles, respectively. The resulting values for the chromaticity and the detuning parameters must be selected with care, however, in order not to run into head-tail instabilities or to considerably reduce the dynamic aperture. A simulation study has been launched to estimate the parameters necessary for stabilisation of the beam under the influence of electron clouds.

WEPPR073	Effects of an Asymmetric Chamber on the Beam Coupling Impedance	3099
	C. Zannini, K.S.B. Li, G. Rumolo CERN, Geneva, Switzerland C. Zannini EPFL, Lausanne, Switzerland
	The wake function of an accelerator device appears to have a constant term if the geometry of the device is asymmetric or when the beam passes off axis in a symmetric geometry. Its contribution can be significant and has to be taken into account. In this paper a generalized definition of the impedance/wake is presented to take into account also this constant term. An example of a device where the constant term appears is analyzed. Moreover, the impact of a constant wake on the beam dynamics is discussed and illustrated by a HEADTAIL simulation.

WEPPR091	Multi-Particle Simulation Codes Implementation to Include Models of a Novel Single-bunch Feedback System and Intra-beam Scattering	3147
	M.T.F. Pivi, A. Chao, C.H. Rivetta SLAC, Menlo Park, California, USA F. Antoniou, K.S.B. Li, Y. Papaphilippou CERN, Geneva, Switzerland M. Boscolo, T. Demma INFN/LNF, Frascati (Roma), Italy K.G. Sonnad CLASSE, Ithaca, New York, USA
	Funding: Work supported by the U.S. Department of Energy under contract DE-AC02-76SF00515 and the US LHC Accelerator Research Program (LARP). The beam tracking codes C-MAD and HEAD-TAIL have been enhanced to include a detailed model of a single-bunch feedback system. Such a system is under development to mitigate the electron cloud and the transverse mode coupling instability (TMCI) in the SPS and LHC at CERN. This paper presents the model of the feedback sub-systems: receiver, processing channel, filter, amplifier and kicker, which takes into account the frequency response, noise, mismatching and technological limits. With a realistic model of the hardware, it is possible to study the prototypes installed in the SPS and design a novel feedback system. The C-MAD code, which is parallel and optimized for speed, now also includes radiation damping and quantum excitation and a detailed model of Intra-Beam Scattering (IBS) based on the Zenkevich-Bolshakov algorithm, to investigate the IBS during damping and its effect on the beam distribution, especially the beam tails, that analytical methods cannot investigate. Intra-beam scattering is a limiting factor for ultra-low emittance rings such as CLIC and Super-B.

Paper

Title

Page

A Generic Data Model for HeadTail: Design and Implementation with Examples

307

K.S.B. Li, G. Rumolo
CERN, Geneva, Switzerland

HeadTail has been developed in 2002 for the efficient simulation of instabilities and collective effects in large circular accelerators. Since then, the capabilities of the code have been continuously extended and the output data has become increasingly complex and large-scale ranging from the statistical description of single bunches to the statistical description of all slices within bunches up to the dynamics of the full 6D phase space over several thousands of turns. Processing this data in an effective manner and endowing it with a structure that provides a physical concept calls for new and optimised data formats. To meet state-of-the-art standards, the hierarchical data format (HDF5) has been selected as native output data format together with H5Part and XDMF as native data structures. We describe the implementation of the H5Part and the XDMF data structures into HeadTail and show some illustrative examples for data processing.

WEPPR068

Mitigation of Electron Cloud Instabilities in the LHC Using Sextupoles and Octupoles

3084

K.S.B. Li, G. Rumolo
CERN, Geneva, Switzerland

Coherent electron cloud instabilities pose a serious limitation for luminosity upgrades in the Large Hadron Collider (LHC) at CERN. In particular, when bunch spacings reach below 50 ns, electron cloud formation is enhanced which in turn drives beam instabilities. The beam can be stabilised by shifting the tune and by increasing the tune spread using sextupoles or octupoles, respectively. The resulting values for the chromaticity and the detuning parameters must be selected with care, however, in order not to run into head-tail instabilities or to considerably reduce the dynamic aperture. A simulation study has been launched to estimate the parameters necessary for stabilisation of the beam under the influence of electron clouds.

WEPPR073

Effects of an Asymmetric Chamber on the Beam Coupling Impedance

3099

C. Zannini, K.S.B. Li, G. Rumolo
CERN, Geneva, Switzerland
C. Zannini
EPFL, Lausanne, Switzerland

The wake function of an accelerator device appears to have a constant term if the geometry of the device is asymmetric or when the beam passes off axis in a symmetric geometry. Its contribution can be significant and has to be taken into account. In this paper a generalized definition of the impedance/wake is presented to take into account also this constant term. An example of a device where the constant term appears is analyzed. Moreover, the impact of a constant wake on the beam dynamics is discussed and illustrated by a HEADTAIL simulation.

WEPPR091

Multi-Particle Simulation Codes Implementation to Include Models of a Novel Single-bunch Feedback System and Intra-beam Scattering

3147

M.T.F. Pivi, A. Chao, C.H. Rivetta
SLAC, Menlo Park, California, USA
F. Antoniou, K.S.B. Li, Y. Papaphilippou
CERN, Geneva, Switzerland
M. Boscolo, T. Demma
INFN/LNF, Frascati (Roma), Italy
K.G. Sonnad
CLASSE, Ithaca, New York, USA

Funding: Work supported by the U.S. Department of Energy under contract DE-AC02-76SF00515 and the US LHC Accelerator Research Program (LARP).
The beam tracking codes C-MAD and HEAD-TAIL have been enhanced to include a detailed model of a single-bunch feedback system. Such a system is under development to mitigate the electron cloud and the transverse mode coupling instability (TMCI) in the SPS and LHC at CERN. This paper presents the model of the feedback sub-systems: receiver, processing channel, filter, amplifier and kicker, which takes into account the frequency response, noise, mismatching and technological limits. With a realistic model of the hardware, it is possible to study the prototypes installed in the SPS and design a novel feedback system. The C-MAD code, which is parallel and optimized for speed, now also includes radiation damping and quantum excitation and a detailed model of Intra-Beam Scattering (IBS) based on the Zenkevich-Bolshakov algorithm, to investigate the IBS during damping and its effect on the beam distribution, especially the beam tails, that analytical methods cannot investigate. Intra-beam scattering is a limiting factor for ultra-low emittance rings such as CLIC and Super-B.