SOFB Results

Fig. 2 documents the performance of the SOFB over 12 hours of user operation. After accumulating a current of 320 mA, the top-up mode is entered [5,6]. During 9 hours of top-up operation the SOFB stabilizes the orbit to rms values of $\approx$ 1 $\mu$m with respect to the ``Golden Orbit'' in both planes. The RF frequency is corrected by df whenever $\vert$df$\vert$ exceeds 5 Hz corresponding to dP/P $\approx$ 2$\cdot$10$^{-5}$. In this particular case a frequency correction is performed every $\approx$ 45 min. Please note that the horizontal rms value increases (see ``saw tooth'' in Fig. 2) while df is not applied.

Figure: Screenshot depicting rms values of the horizontal (`` x RMS'') and vertical (`` y RMS'') deviations from the ``Golden Orbit'' of $\approx$ 1 $\mu$m during a 9 hour ``top-up'' run at 320 mA. The proposed frequency correction df is applied when passing a threshold of 5 Hz corresponding to an energy deviation dP/P  $\approx$ 2 $\cdot$10 $^{-5}$

Fig. 3 shows the variation of the orbit position at the location of ID U24 over 13 hours of top-up operation. The values are extrapolated from the readings of the adjacent BPM upstream. The deviations from the ``Golden Orbit'' are well fitted by Gaussian distributions with 2nd moments of $\sigma _x$ = 0.5 $\mu$m and $\sigma _y$ = 0.7 $\mu$m, respectively. The long term energy stability of the storage ring, characterized by the dP/P change proposed by the SOFB, is shown in Fig. 4 which was recorded over 14 days of nearly continuous SOFB operation at a rate of 1 Sample/min. During this period rms orbit deviations of 1 $\mu$m could be maintained.

Figure: Scatter-plot a) of the projected orbit position at the location of ID U24 taken at a sampling rate of 1 Hz over a 13 hour top-up run and corresponding histograms for the horizontal b) and vertical c) beam motion. The 2nd moments of the Gaussian distributions are fitted to be $\sigma _x$ = 0.5 $\mu$m and $\sigma _y$ = 0.7 $\mu$m, respectively

Figure 4: Energy stability (dP/P change by SOFB) over 14 days (1 Sample/min) of SOFB operation. The 2nd moment of the Gaussian distribution is fitted to be $\sigma$(dP/P) $\approx$ 10$^{-5}$