Capability Upgrade of the Diamond Transverse Multibunch Feedback

We describe an upgrade to the Transverse MultiBunch Feedback processor used at Diamond for control of multibunch instabilities and measurement of betatron tunes. The new system will improve both feedback and diagnostic capabilities. Bunch by bunch selectable control over feedback filters, gain and excitation will allow finer control over feedback, allowing for example the single bunch in a hybrid or camshaft fill pattern to be controlled independently from the bunch train. It will also be possible to excite all bunches at a single frequency while simultaneously sweeping the excitation for tune measurement of a few selected bunches. The single frequency excitation can be used for bunch cleaning or continuous measurement of the beta-function. A simple programmable event sequencer will provide support for up to 8 steps of programmable sweeps and changes to feedback and excitation, allowing a variety of complex and precisely timed beam characterisation experiments including growdamp measurements in unstable conditions.