Upgrades to the digital receiver-based low-intensity beam diagnostics for CERN AD

The CERN AD low-intensity beam multidiagnostics (LIMD) has been upgraded as planned since 2001 by adding tune measurements during ramps and plateaus, based on the beam transfer function (BTF) method. This relies on transversally exciting the beam by a deflector and deriving the BTF and coherence function from FFTs of excitation and beam response recorded by digital receivers (DRX). These, continuously tuned to a betatron sideband, pass data to a digital signal processor (DSP) on the DRX board for data processing. The upgrades discussed also include increased longitudinal frequency range, noise reduction measures and digital flags for setup of data acquisition (DAQ) and processing parameters.