Up to last run the orbit was corrected every 3 seconds. In that case, distortions in the orbit faster than 3 seconds (or 0.3 Hz) were not corrected. The residual orbit had an rms value of 0.4 um in both planes. Residual orbit refers to the difference between the measured orbit and the defined design orbit.
With the new system, the orbit is corrected up to frequencies of 200 Hz and the rms value of the residual orbit has decreased almost by one order of magnitude. Now it is 0.08 um in the horizontal and 0.04 in the vertical plane respectively.
By sampling the beam position data at 10 kHz, the integrated power spectral density (PSD) has been calculated in both planes. Figure 1a compares the PSD in the horizontal plane with and without the FOFB ON and figure 1b does the same for the vertical plane.
One can notice that the FOFB completely dumps the 3 Hz noise of the booster, when injection is on. The signal at 3 Hz is, together with the 50 Hz signal, the largest source of noise on the measured spectrum when the FOFB is off. The distortion at 50 Hz does not disappear completely but it is damped by a factor of 2.
Fig 1a - Integrated spectra for the horizontal plane. Up to 200 Hz the integrated noise is below 1 um when the FOFB is running. The colours correspond to spectra taken under different working conditions.
- Blue: FOFB off, injection off;
- Green: FOFB on, injection off.
- Red: FOFB on, injection on;
- Lightblue: FOFB off, injection on;
Fig 1b - PSD for the vertical plane. Up to 200 Hz the integrated noise is below 0.3 um when the FOFB is running. The colours correspond to spectra taken under different working conditions.
- Blue: FOFB off, injection off;
- Green: FOFB on, injection off.
- Red: FOFB on, injection on;
- Lightblue: FOFB off, injection on;
