An intense proton beam diagnostic using the [sup 7]Li([ital p],[gamma])[sup 8]Be [r arrow][sup 141]Pr([gamma],[ital n])[sup 140]Pr([beta][sup +]) nuclear reaction sequence

An indirect nuclear activation diagnostic was developed to measure the proton fluence onto a thick target of lithium metal located in the diode region of pulsed power accelerators. This diagnostic uses the nuclear reaction sequence [sup 7]Li([ital p],[gamma])[sup 8]Be[r arrow][sup 141]Pr([gamma],[ital n])[sup 140]Pr([beta][sup +]) to relate the proton fluence to induced [sup 140]Pr activity. This diagnostic was calibrated using a Van de Graaff accelerator. Energetic protons were focused onto a thick lithium target driving the [sup 7]Li([ital p],[gamma])[sup 8]Be reaction. The resulting prompt gamma rays activated a secondary [sup 141]Pr target via the reaction [sup 141]Pr([gamma],[ital n])[sup 140]Pr([beta][sup +]). A NaI gamma-gamma coincidence detector system was used to measure the induced [sup 140]Pr activity as a function of proton energy and proton fluence. These data yielded a calibration curve for proton energies ranging from 2 to 12 MeV. Since deuterium impurities can interfere with this diagnostic by driving the reaction sequence [sup 7]Li([ital d],[ital n])[sup 8]Be[r arrow][sup 141]Pr([ital n],2[ital n])[sup 140]Pr, a similar calibration experiment was conducted using deuterium ions. These data yielded a correction factor that can be used to determine the deuterium contribution to the [sup 140]Pr activity, providing that the deuterium beam fraction is known.