IPAC2011 - List of Authors (Diop, M.D.)

Paper	Title	Page
MOPS049	Study of Ion-induced Instabilities and Transverse Feedback Performance at SOLEIL	712
	R. Nagaoka, L. Cassinari, M.D. Diop, J.-M. Filhol, M.-P. Level, A. Loulergue, P. Marchand, R. Sreedharan SOLEIL, Gif-sur-Yvette, France
	Experimental studies indicate that the SOLEIL storage ring at its maximum designed current of 500 mA is under a large influence of ions, potentially capable of inducing the so called fast beam-ion instability. To avoid it, the following three conditions have been empirically found effective: A reduced RF voltage, uniform filling and a large vertical chromaticity. While the choice of uniform filling appears contradictory to raising the ion instability threshold, it goes well with lowering of the RF voltage if outgassing due to beam-induced heating of the vacuum components is the primary source of ions. Additional difficulties associated are frequent occurrence of sudden beam blowups despite the presence of transverse feedback, which are large enough to trigger machine interlocks leading to complete beam losses. These blow ups may even take place horizontally inside in-vacuum insertion devices. The present paper reports on the results and findings obtained through experimental and simulation studies carried out on the collective beam dynamics and the transverse feedback performance, which are deeply interlinked, in order to clarify the mechanism of the encountered phenomena.

Paper

Title

Page

Study of Ion-induced Instabilities and Transverse Feedback Performance at SOLEIL

712

R. Nagaoka, L. Cassinari, M.D. Diop, J.-M. Filhol, M.-P. Level, A. Loulergue, P. Marchand, R. Sreedharan
SOLEIL, Gif-sur-Yvette, France

Experimental studies indicate that the SOLEIL storage ring at its maximum designed current of 500 mA is under a large influence of ions, potentially capable of inducing the so called fast beam-ion instability. To avoid it, the following three conditions have been empirically found effective: A reduced RF voltage, uniform filling and a large vertical chromaticity. While the choice of uniform filling appears contradictory to raising the ion instability threshold, it goes well with lowering of the RF voltage if outgassing due to beam-induced heating of the vacuum components is the primary source of ions. Additional difficulties associated are frequent occurrence of sudden beam blowups despite the presence of transverse feedback, which are large enough to trigger machine interlocks leading to complete beam losses. These blow ups may even take place horizontally inside in-vacuum insertion devices. The present paper reports on the results and findings obtained through experimental and simulation studies carried out on the collective beam dynamics and the transverse feedback performance, which are deeply interlinked, in order to clarify the mechanism of the encountered phenomena.