Post date: Jun 27, 2014 3:23:27 AM
This morning the team have been using a real time spectrum analyser to look at the frequency spectrum and finding sidebands using a mixed-in RF perturbation (rather than the 'horizontal perturbator') on the flat triangle plate monitor. From the time-based spectrum we can see that not all of the beam is captured and accelerated, so the main frequency spectrum has a double peak - one for the accelerated flat-topped beam and one for the 'lost' beam. However the sidebands around the accelerated beam frequency peak are measurable.
We expect from prior experience that using this method we can measure tunes up to about 8msec in the acceleration cycle as the rigidity at the point is high enough that the mixed in RF perturbation does not have much effect (this is not quite one third of the way through the acceleration cycle and only corresponds to about 35 MeV energy...).
To make sure we are really seeing the horizontal sidebands and not the vertical ones we will repeat the measurements taking the frequency from S7 up (which is not sensitive to horizontal oscillations) - if the two frequencies are different we can be confident that the frequencies from the triangle plate monitor are really the horizontal tunes. This will then give us some data to compare when we try the new setup later (Monday?) with Sakamoto-san's double triangle monitor and the new perturbator hardware which will be installed when we break vacuum later today.