HB2018 - List of Authors (Antipov, S. A.)

Paper

Title

Page

Simulation and Measurement of the TMCI Threshold in the LHC

43

D. Amorim, S. A. Antipov, N. Biancacci, X. Buffat, L.R. Carver, E. Métral
CERN, Geneva, Switzerland

The transverse mode coupling instability occurs in individual bunches when two transverse oscillation modes couple at high intensity. Simulations predict an instability threshold in the LHC at a single bunch intensity of 3*10¹¹ protons. The TMCI threshold can be inferred by measuring the tune shift as a function of intensity. This measurement was performed in the LHC for different machine impedances and bunch intensities. The impedance was changed by varying the primary and secondary collimators gaps to increase their contribution to the resistive wall impedance. The experiment also allowed to assess the validity of the LHC impedance model in the single bunch case.

Slides MOP2WA05 [4.729 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-HB2018-MOP2WA05

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THA1WE01

New Electron Cloud Instability Mechanism and its Detection and Suppression

V.A. Lebedev
Fermilab, Batavia, Illinois, USA
S. A. Antipov
CERN, Geneva, Switzerland

Fast transverse instability was observed in Recycler proton storage ring (RR). The instability develops within 100 turns and may lead to beam loss. The fast rise suggested that the instability is driven by electron cloud. That was later supported by microwave transmission measurements. In difference to RR the instability was not observed in similar conditions in Main Injector (MI). RR is based on combined function dipoles while MI uses pure dipoles. This difference plays a key role in instability development. The instability dynamics was studied experimentally and with numerical simulations. An analytical model predicts that electrons are trapped in RR dipoles. Numerical simulations show that up to 1% of particles can be trapped. The cloud build-up is exponential with its density limited by space charge. That results in the cloud intensity orders of magnitude greater than in MI. A growth rate of about 30 turns and mode frequency of 0.4 MHz are consistent for observations and PEI simulations. The high intensity batch can be stabilized by low intensity clearing bunch injected behind batch which destroys the trapped electron cloud and prevents its multi-turn accumulation.

Slides THA1WE01 [7.328 MB]

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

Paper	Title	Page
MOP2WA05	Simulation and Measurement of the TMCI Threshold in the LHC	43
	D. Amorim, S. A. Antipov, N. Biancacci, X. Buffat, L.R. Carver, E. Métral CERN, Geneva, Switzerland
	The transverse mode coupling instability occurs in individual bunches when two transverse oscillation modes couple at high intensity. Simulations predict an instability threshold in the LHC at a single bunch intensity of 3*10¹¹ protons. The TMCI threshold can be inferred by measuring the tune shift as a function of intensity. This measurement was performed in the LHC for different machine impedances and bunch intensities. The impedance was changed by varying the primary and secondary collimators gaps to increase their contribution to the resistive wall impedance. The experiment also allowed to assess the validity of the LHC impedance model in the single bunch case.
	Slides MOP2WA05 [4.729 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-HB2018-MOP2WA05
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THA1WE01	New Electron Cloud Instability Mechanism and its Detection and Suppression
	V.A. Lebedev Fermilab, Batavia, Illinois, USA S. A. Antipov CERN, Geneva, Switzerland
	Fast transverse instability was observed in Recycler proton storage ring (RR). The instability develops within 100 turns and may lead to beam loss. The fast rise suggested that the instability is driven by electron cloud. That was later supported by microwave transmission measurements. In difference to RR the instability was not observed in similar conditions in Main Injector (MI). RR is based on combined function dipoles while MI uses pure dipoles. This difference plays a key role in instability development. The instability dynamics was studied experimentally and with numerical simulations. An analytical model predicts that electrons are trapped in RR dipoles. Numerical simulations show that up to 1% of particles can be trapped. The cloud build-up is exponential with its density limited by space charge. That results in the cloud intensity orders of magnitude greater than in MI. A growth rate of about 30 turns and mode frequency of 0.4 MHz are consistent for observations and PEI simulations. The high intensity batch can be stabilized by low intensity clearing bunch injected behind batch which destroys the trapped electron cloud and prevents its multi-turn accumulation.
	Slides THA1WE01 [7.328 MB]
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)