The IUCF Phase Probe

A non-intercepting, charge-sensitive, sampling beam probe has been developed for use in internal beam phase measurements in the variable-energy, separated sector injector cyclotron at Indiana University. The two probe pickup plates of 10mm by 16mm are located above and below the median plane with sampling diodes in close proximity. The probe head is mounted on a movable assembly permitting continuous observation of phase history from inflection radius through extraction radius, at interval beam currents of 100 nanoamperes or greater with pulse rise times of less than one nanosecond. Over a two-year period the phase probe has proved relatively reliable and easy to use for confirming trim coil adjustments and orbit dynamical isochronization procedures. The probe display, in addition to providing data on phase group width and centroid versus radius, has on occasion shown up ion source ripple and radio frequency parasitic generation which might otherwise have been overlooked.