Pasta – an RF Phase Scan and Tuning Application

To assist the beam commissioning in the Spallation Neutron Source (SNS) linac, a general purpose Radio Frequency (RF) tuning application has been written to help set RF phase and amplitude. The method involves varying an Rf cavity amplitude and phase settings over a fairly large range and comparing the measured downstream beam phase response “signatures” to model predictions. The model input for cavity phase, cavity amplitude, and the beam energy are varied to best match observations. This scheme has advantages over other RF tuning techniques of not requiring intercepting devices (e.g. Faraday Cups), and not being restricted to a small linear response regime near the design values. The application developed here is general and can be applied to different RF structure types in the SNS linac. Example application for the SNS Drift Tube Linac (DTL) and Coupled Cavity Linac (CCL) structures will be shown