  The build up of electron clouds inside a particle accelerator vacuum chamber
can produce strong transverse and longitudinal beam instabilities which in turn
can lead to high levels of beam loss often requiring the accelerator to be run
below its design specification. To study the behaviour of electron clouds at
the ISIS Proton Synchrotron, a Micro-Channel Plate (MCP) based electron cloud
detector has been developed. The detector is based on the Retarding Field
Analyser (RFA) design and consists of a retarding grid, which allows energy
analysis of the electron signal, and a MCP assembly placed in front of the
collector plate. The MCP assembly provides a current gain over the range 300 to
25K, thereby increasing the signal to noise ratio and dynamic range of the
measurements. This paper presents the first electron cloud observations at the
ISIS Proton Synchrotron. These results are compared against signals from a beam
position monitor and a fast beam loss monitor installed at the same location.
