Fast Orbit FeedBack

One of the necessary improvements of Alba is the top up system. With this, the beam accumulated in the storage ring can be restored under a continuous re-injection precisely on the buckets here it bunch is losing charge. Recovering an old snapshot of the machine status:

This is an example where the stored beam had decay from 60mA to a bit more than 30 in around 6 hours (this was a year a go, by now we are having more current and a longer beam live time). This lost of current requires re-injections like what is in the middle of the red plot.

This re-injection, afaik, produces perturbations on the beam orbit that at the end means drifts in the x-ray beam in the beamlines. This re-injection, due to radiation safety reason have to be done with the frontends closed. That is with the beamlines in a standby, without light and waiting  that this re-injection finishes. This re-injection causes an interruption on the experiments, and the longest experiment you can do is the one that can be performed between re-injections. You can imagine the consequences if the most insignificant thing fails in the middle of an experiment.under this conditions.

Well, to make this re-injection possible with the frontends open, the orbit of the beam must be very static. The beam has to be thine characterised and its oscillations below some microns.

How the orbit is corrected? In the sextupoles, there are the coils for each of the poles, but it is also another pair of thinner coils that sets the corrector component. I imagine it like a tiny little bending (they have like 3 orders less of magnitude in terms of current).

Those correctors can change its current very fast for a small modifications. That can be, in the order of the hundreds of miliamps can change it with a 10kHz frequency.

With this, together with a beam position monitoring at this speed, and if you can process all this data, the orbit perturbations can be controlled good enough to allow to re-inject with the necessary safeness to implement the top up system and have the plot of the current as an straight horizontal line (negligible ripple).

Main issue: with in a ring of around 400m of perimeter share between 88 beam position monitors all their sets of data, plus the sniffers we have to take this data to calculate those corrections, and stablish the new setpoints to another 88 corrector power supplies. All this at 10kHz: read, calculate, write: simple operations.