Fermilab, Batavia
ORNL, Oak Ridge, Tennessee
In present circular machines the beam intensity is often limited by the following phenomena: machine resonances, various tune shifts (and spreads), and instabilities. In this paper we will propose a path toward alleviating these phenomena by making accelerators nonlinear as well as integrable.
EPFL, Lausanne
CERN, Geneva
Crossing transition energy in the CERN PS is critical for the stability of high intensity beams, even with the use of a second order gamma transition jump scheme. The intense single bunch beam used for the neutron Time-of-Flight facility (n-ToF) needs a controlled longitudinal emittance blow-up at the flat bottom to prevent a fast single-bunch vertical instability from developing near transition. This instability is believed to be a Transverse Mode Coupling (TMCI) type. A series of measurements performed in 2009 and 2010 aims at using this TMCI observed on the ToF beam at transition, as a tool for estimating the transverse global impedance of the PS. For this purpose, we compare the measurement results with the predictions of the HEADTAIL code and find the matching parameters. This will allow predicting the stability of the high brightness LHC beam near transition. The final goal is to study the feasability of a possible cure to the fast vertical instability measured on the ToF beam by applying an improved gamma transition jump scheme instead of compromising the longitudinal density.
GSI, Darmstadt
At GSI and for the FAIR project short heavy-ion bunches are required for the production and storage of exotic fragment beams as well as for plasma physics applications. In the SIS-18 and in the projected SIS-100 synchrotron longitudinal compression via fast bunch rotation is performed directly before extraction. In order to arrive at the required bunch length the rf cycle has to be optimized for high intensities to avoid the blowup of the occupied longitudinal phase space area. We will discuss experimental and simulation results of the rf capture at injection energy, the rebunching process at the final energy and the subsequent bunch rotation.