Adjusting the RF

Once a dip in lifetime has been observed the next step is to make sure that the dip is the ``real'' depolarizing resonance and not a sideband or a mirror (see chapters 3.4 and 3.5). Identifying the mirror is simple, because the RF main frequency can easily be changed as mentioned earlier; distinguishing the main resonance from its sidebands however is a bit more difficult because of the fact that the voltages of all four RF stations should be changed synchronously (and by well defined means) by a small value in order to change the total RF voltage by as little as necessary. The RF voltage of each RF station can be changed through the SLS control system; normally this is done by hand, one station after the other, but such a procedure is by no means synchronous.

Therefore another computer program was introduced which accomplishes the following tasks: In a first step it acquires the current set voltages of each RF station by querying the corresponding EPICS channels. It then calculates new values depending on a common scaling factor fed to the program as parameter. These new values are then written to the appropriate EPICS channels simultaneously, thus allowing shifts in total RF voltage by well defined means.