Dependence of single beam lifetime on bunch length

Heat load on beam screens, collimators and injector kickers can limit the maximum beam intensity in the LHC. Longer bunches reduce this effect and can give other benefits (e.g. for e-cloud). However, an increase in particle losses could also be expected. The goal of this MD was to determine a correlation between losses and bunch length on the LHC flat top. We injected 8 bunches per ring with nominal emittance (0.5 eVs) and nominal intensity (1.15x10^11 pp) and accelerated them to 3.5 TeV, where a controlled longitudinal emittance blow-up was applied, giving a spread in bunch lengths (measured by BQM) in the range 1.15-1.65 ns. Then, bunches were observed for one hour at flat top and correlation between losses and bunch length is presented. At the end of the study, voltage was reduced to further increase bunch lengths. Phase measurements were also acquired in parallel and described here.