Non-linear beam dynamics tests in the LHC: measurement of intensity decay for probing dynamic aperture at injection

For a second year in a row dynamic aperture experiments have been performed at the LHC. These studies have been carried out by two teams following alternative techniques: On Beam 1 a novel approach has been tested which heats the beam until the emittance becomes large, and derives the dynamic aperture from beam losses assuming an inverse logarithm model for the time-dependence of the intensity. On Beam 2, the traditional approach of sampling the dynamic aperture with large amplitude kicks has been pursued [1]. In 2011, considerable progress was made and impressive results have been reported. In 2012 a further Machine Development (MD) session was scheduled during which both teams have benefited from an improved availability of the beams and more optimal performance of the instrumentation. Observations and analysis are presented as two MD reports of the LHC dynamic aperture experiment MD. This note describes the observations made on Beam 1, when the strength of the spool pieces have been varied. The key quantity is the intensity evolution. Clear differences have been recorded and a preliminary analysis is reported in this note. The considerable set of data will be analysed in details later on.