Frank C. Young

Diagnostics for intense pulsed ion beams

Diagnostic methods pertinent to the probing of intense pulsed ion beams are described. Special emphasis is given to the measurement of delayed radioactivity from nuclear reactions induced in a target by the ions. This nuclear activation analysis provides the most precise, unambiguous means of determining the number of ions per pulse that is presently available. A compilation of yields and cross sections for several nuclear reactions is given. Included among the nuclear techniques is the measurement of prompt radiation such as γ rays and neutrons from ion‐induced reactions. In addition, a scintillator–photodiode detector is described which has proven to be useful for the measurement of time of flight and which may be used to observe the relative pulse shape. Biased ion collectors and difficulties associated with their use are also discussed.

Neutron Diagnostics for Pulsed Plasma Sources

Neutron detectors have been developed and applied to a variety of pulsed plasma sources with intensities ranging from 102 to 1012 neutrons/pulse. For yields as small as 102 neutrons, a 6Li-glass-scintillator detector is used. A rhodium-activation counter has been developed for yields greater than 106 neutrons. These detectors are used for total yield and angular distribution measurements. Neutron energies are determined primarily by the time-of-flight technique. Limitations on this technique for neutron yield and energy measurements are discussed. Improved methods are needed to measure the spatial extent of these neutron sources.

Intense proton beam current measurement via prompt gamma rays from nuclear reactions.

The current of an intense, pulsed proton beam is experimentally determined by monitoring prompt gamma rays from nuclear reactions induced in a suitable target. Relevant data are given on the reactions employed including (7)Li(p,gamma) (8)Be, (19)F(p,alphagamma) (16)O, and (12)C(p,gamma) (13)N so that absolute currents can be determined. This method avoids the complication of target blowoff and the need for attenuating screens when applied to high current density beams.

Calibration of a Mn‐activation detector for intense pulsed energetic neutron sources

A simple Mn‐activation detector for pulsed MeV neutron sources with intensities exceeding 1011 neutrons/pulse is described. Absolute calibration of the detector using neutrons from the 7Li(p,n)7Be reaction is determined as a function of the distance from the source.