Post date: Mar 27, 2014 2:39:00 AM
Shinji showed us the results from yesterdays measurements.
First he showed the vertical tune measurement with F-mag -5%. It turns out we need to actually increase the D-mag strength by about 10% to get the same tune (due to field interactions in magnet).
Beam profile was also shown as integrated first proton peak normalised to H- peak area as a function of foil position. Malek's simulations show we should have dispersion about 0.5m at foil position. We have 15mm shift with 5% change in excitation current. We will need to check how much the field really varies when you change the excitation current using TOSCA.
Time of flight as function of foil position. TOF has changed about 1.1% but may not be consisted with what we expected and we need to look at it more (analysis was very quick...)
If possible it would be good to measure another point or two of dispersion with equivalent momentum. We will also re-measure a few points at nominal settings now that we have the horizontal triangle plate monitor as well (so then we can extract horizontal tune to see if that changes at all to satisfy ourselves that the equiv. momentum method is reliable).
David also presented a few plots of his analysis of the same data, using peak height and FWHM area. There was a discussion about the area of the first turn compared to the area of the H- peak.
Kuriyama-san showed some results on integrating the signals from the first turns from S7 bunch monitor. Even with baselining it is very difficult to properly do the integration as the tails can be quite long and run into the next peak.
We discussed about how to measure the dispersion in the ring. We concluded we should actually be able to use the COD measurement data with the RF programme setting to convert time to momentum and get a value for the dispersion in the centre of the F magnet that way. Suzie will look at the existing data for this.
Now we are setting up to do COD measurements at 400A, 550A and 700A to see the effect of correction. We would also like to do more dispersion matching this afternoon.