Performance and Progress of the Daresbury Photon Beam Tungsten Vane Monitor System

The tungsten vane monitors (TVMs) on the SRS at Daresbury are used operationally to monitor the photon beam position and angle on user beamlines. On many of these lines the TVM output is used to perform automatic feedback correction and it is therefore crucial to optimise the TVM precision and stability. Recent changes to TVM bias voltages and amplifier gain are reported which have improved the signal-to-noise ratio and the stability of the calibration. A new procedure, mapping out the vane currents as a function of beam position in two dimensions, has proved a powerful technique for the diagnosis of TVM misalignment and shadowing. Investigation of the stability of the TVM output as a function of the SRS electron beam current are also discussed.