Wavelength Control Server & Multi-Color Lasing
Svitozar gives a short overview on two-color lasing (see presentation) and summarizes the problems setting it up with the current controls. Lars gives an update on the state of phase shifter controls. After some discussion, we agree to further develop the wavelength control server in the following directions:
- Add support for multiple undulator groups. These groups replace the old "taper groups". Each one has an independent photon energy setting and the well-known taper settings. Each undulator cell can be assigned to one or no undulator group.
- Establish a persistent phase offset for the undulator phase shifters. So far, a gap offset can be specified and is maintained when the wavelength is changed; using a phase offset instead would make the undulator setup less wavelength dependent. Some restructuring of the server might be required to achieve this: Right now, a PLC calculates the phase shifter gap. To change the behavior, we will always have to calculate phaseshifter gaps from our own data.
- Calculate energy loss per cell (linear taper). The server should automatically calculate the electron energy loss due to resistive wakes and spontaneous emission in each cell and adapt the K values of the following cells accordingly. It should be possible to switch this calculation off and to customize the parameters used. It should still be possible to add a linear (and quadratic) taper on top of this. Corollary: Opening an upstream undulator group would have to automatically change the gap of a downstream group.
- Allow arbitrary functions for tapering (optional). As a stretch goal, we could allow user-defined functions for setting up the taper profile.