Wednesday 25th June 2014

Post date: Jun 25, 2014 8:57:27 AM

Today we started investigating the dispersion control measurement using the equivalent momentum method. Our first approach was to use the new (small) faraday cup on an actuated rod in the foil region (with foil removed) to directly measure the beam intensity as a function of radial position (rather than moving the foil & using S7 bunch monitor as was used by Shinji in March.)

To start with we tested this method for the nominal magnet settings, and observed some slightly unexpected results. Firstly, the signal from the faraday cup is positive (not negative as expected). Secondly, the beam distribution looks asymmetric (We decided to run a calibration test of the faraday cup method vs the stripping foil method used before. (Result will be uploaded). Because we felt the faraday cup method was not yet reliable enough, we decided to press on with dispersion measurements using the stripping foil method as before.

Using Ludovic's injection line model it is predicted that Q8 (one of 3 main quads in injection line) seems to have the main control over the dispersion function (the 'coarsest' control).

We will do measurements with 0%, -5%, -2%, +2% F strength as in March/April

For Q8 settings of nominal, +10% strength and -10% strength.