Post date: Mar 26, 2014 2:56:05 AM
Suzie went through the analysis by her & David on the COD correction data from yesterday.
The results from yesterday show that the D1 correction coil scheme doesn't seem to be very effective at the moment, but we were very limited in terms of excitation current. It may be possible to use a different power supply to increase the excitation current but this would take min. 1 day to install. It will probably not be able to fit into this experimental run.
Suzie checked whether or not the COD was the same this time as in November (18/11/13). There is a small discrepancy in the size of the COD. In November we used a 400A main corrector coil current for the COD measurement (18/11/13) and the average offset between the 3 probes was 21cm. For 550A it was 14.7cm which was a good improvement. From yesterdays data, the COD offset from the mean of the 3 probes was 21cm even though the main corrector coil current was 468A. We expected it to be slightly better than this.
The 468A value was chosen as this optimises extraction efficiency, but since we are not extracting for these measurements maybe we can achieve better COD correction with the main corrector coil for now. It is possible to increase the main corrector coil current higher (up to possible 700A limited by heat) so we will attempt a quick measurement varying the corrector coil current to see if we can achieve an even better correction at fixed energy.
Shinji discussed his more detailed plan for the dispersion matching using the equivalent momentum method. He also showed some tracking results from Malek who had sent them overnight, which shows the effect of dispersion at the foil position.
For Shinji's dispersion matching method we will rely on a measurement of the vertical tune to make sure that the F/D ratio is the same when the excitation currents are varied. More detail is in Shinji's slides from today.
Our plan for today:
Before lunch we will do some quick test runs towards Shinji's dispersion method to check if it is feasible.
After lunch we will look at the dispersion measurement test data, then do the COD correction measurement with a few values of the corrector coil. If we get time we will do more on Shinji's dispersion method.