AN ELECTRON-PROBE AS A STORED BEAM DIAGNOSTIC

A device is described which employs a weak electron probe beam to meas ure moments of the distribution of a coasting charged particle beam in a storage ring through the beam-beam electromagnetic interaction. The electron beam is confined by a longitudinal magnetic field in a solen oid and guided by electrostatic steering elements. Displacement of the probe beam is observed with a position-sensing collector. The results of initial tests are reported. The stored beam intensity can be monit ored with a sensitivity of a few muA, approaching that of commercial d c transformers, or the position can be determined to a precision of be tter than 0.3 mm. By placement in a ring region having large dispersio n, the device also serves as a useful beam momentum monitor. With a fu rther reduction of probe beam diameter, this device may become useful as a monitor of changes in cooled beam emittance.