DESTABILISING EFFECT OF THE LHC TRANSVERSE DAMPER

E. Métral, D. Amorim, S. Antipov, N. Biancacci, X. Buffat and K. Li

(CERN, Geneva, Switzerland)

Abstract

Motivation

(i) why a chromaticity Q’ ~ 0 seems more critical in the CERN LHC than predicted?

(ii) why simulations with Q’ ~ 0 reveal a more critical situation with transverse damper than without?

New Vlasov solver (called GALACTIC) developed => New instability mechanism: “ISR (for Imaginary

tune Split and Repulsion) instability” is suggested for this kind of single-bunch instability with Q’ = 0

As the LHC was operated so far below the TMCI intensity threshold (without damper), it seems that this

effect (alone) cannot explain the LHC observations with Q’ ~ 0 => Another mechanism needs to be

identified / added...

MOTIVATION

NEW INSTABILITY MECHANISM & IMPACT ON LANDAU DAMPING