Outlook

The carried out experiments have allowed to measure the SLS storage ring beam energy with very high precision. They have however also shown how tedious and time consuming this method is. It is also very sensitive to perturbations of all kind including gap size changes, tune shifts and orbit drifts. Therefore this method is not a priori suitable for day-to-day parasitic measurements in order to monitor the current beam energy.

Nevertheless it is possible that in the future when SLS operates without frequent shutdown periods and therefore acquires an immanent stability this measurement could be carried out in a short time frame between user shifts allowing an independent check of the beam energy. Such measurements could be used to perform studies on beam stability during typical beam lifetimes and beam drifts during longer run periods. In the long term these studies could help better understanding properties of the SLS storage ring.

Today the high precision of the energy calibration method already allows for a more precise calculation of the momentum compaction factor and its non-linearity (equation 52). Up to now all calculations of this non-linearity were restricted by the precision of the beam energy. In addition the performed energy measurements have shown that the maximum precision has not yet been reached. By lowering the kicker strength and the sweep dwell the depolarizing resonance can be made sharper, thus leading to less uncertainty of the energy calibration. It is expected that future applications of this measurement method at SLS will lead to knowledge of beam energy with a precision of $\frac{\Delta E}{E}=10^{-5}$. Such uncertainties are much smaller than those obtained by measurement of the dipole magnet fields with Hall probes.

Another suggested consequence of these energy measurements is to investigate if the injection from booster to storage ring can be enhanced by matching the energies of the two rings. It has been mentioned that possibly a mismatch between booster and storage ring energy is limiting the injection rates. If the booster injects at design energy and the stored beam in the storage ring has an energy that lies over one percent higher, this could in fact cause injection efficiency to suffer. Investigation of this problem will follow soon.

Apart from the suggested experiments to follow this calibration the original problem has to be solved as well: Why is the beam energy in the SLS storage ring so much higher than the design energy? The currents measured during dipole field measurements are in agreement with the magnet calibration. This leads to the presumption that the dipole magnet measurements have rendered wrong calibration constants between applied current and generated magnetic field for a given hysteresis cycle. As a consequence the dipole fields will be measured again with Hall probes in the near future.