Diagnostic for electron clouds trapped in quadrupoles

Simulations have indicated that electron clouds generated by beam-induced multipactor can be trapped in the mirror-like fields of magnetic quadrupoles and thereby contribute significantly to the electron cloud buildup in high intensity accelerators and storage rings. This could be a very important source of electrons driving the two-stream (e-p) instability at the Los Alamos Proton Storage Ring (PSR) and may also play a significant role in electron cloud effects at some of the new high intensity accelerator projects. We describe the physics design and optimization of an electron-sweeping detector designed to measure the trapped electrons at various times after the beam pulse has passed. The instrument can also serve as an electro-magnetically shielded detector which provides a signal obtained from electrons striking the wall during the passage of beam bunches.