Design and Tests of a New Rest Gas Ionisation Profile Monitor Installed in the SPS as a Prototype for the LHC

Based on the encouraging results obtained with a Rest Gas Ionization Profile Monitor of a first generation, a new monitor was designed and then installed in the SPS at the beginning of 2002. Its design fulfills all the requirements for a future installation in the LHC where four such monitors are foreseen. After the initial tests performed during the run of 2002, a few upgrading steps appeared necessary mainly in order to cope with the nominal LHC beam characteristics. They were implemented during the subsequent winter stop and the operation of the monitor was resumed in 2003 under various conditions of beam, ranging from a LHC pilot bunch up to beams having in the SPS nominal distributions in bunch number, intensity and energy for injection into the LHC. After a description of the monitor design, the measurements performed with the instrument during these last two years are discussed with the difficulties encountered and the corresponding implemented cures. Data acquired in 2003 on the whole spectrum of LHC beam characteristics are presented and the modifications made to prepare the 2004 campaign in a view to still improve the performance are also discussed.