RF Studies of LHC Beams in the SPS

The first dedicated MD session in 2003 was mainly used to reestablish the situation achieved at the end of last year when stable LHC beam with nominal parameters was obtained on the flat top. To stabilise the beam the 800~MHz RF system was used during the cycle in bunch shortening mode together with controlled emittance blow-up. This year emittance blow-up during the ramp was performed using excitation at the synchrotron frequency via the phase loop of the 200~MHz RF system. No beam loss was observed with this method. Some part of MD time was devoted to studies of localised (affecting only a few bunches) dipole instability seen on phase discriminator of the longitudinal damper on the flat bottom and during the ramp. This instability was not noticed last year.