Developments on Intra-bunch instability control - Recent Results from the Demonstration System at the CERN SPS

概要

The Hl-LHC upgrade plans increased luminosity through several methods, including increased beam currents. These increased currents may excite intra-bunch transverse instabilities via TMCI and Ecloud mechanisms in the SPS (penultimate injector) and the HL-LHC . There are several possible options to mitigate these instabilities, including machine optics and RF configurations, the Ecloud mechanisms can be addressed via special attention to vacuum surface treatments to reduce photoelectron yield. An interesting option is to use very wideband transverse feedback to add damping within a 1.8 ns long bunch. The feedback can address both TMCI and Ecloud mechanisms, but is technically very challenging due to the required bandwidth. A wideband feedback demonstration system has been operated at the SPS to explore this technology, it implements a 1 GHz closed loop bandwidth with a digital sampling rate of 4 GHz. Recent results of beam tests, with highlights of the signal processing and kicker technologies, are presented. The scaling of these ideas to the future HL-LHC conditions is also estimated.