Out of core testing of the North Carolina State University PULSTAR reactor positron beam

Out of core tests were performed on the North Carolina State University intense positron beam, prior to insertion into beamport number 6 of the PULSTAR nuclear reactor The beam optics were tested independently of the positron converter/moderator using beams of electrons and the performance of the extraction lenses was found to be in good agreement with the results of design simulations. The moderators were installed and tested by irradiating them with gamma-rays from a Na-24 source. Consequently, positrons (produced through pair production in the converter) were detected at the end of the beamline with a micro channel plate detector. By scaling the count rate obtained with the Na-24 source, to the energy dependent gamma flux in the beamport, the projected positron count rate is estimated at around 5.2 times 10⁸ e⁺/s.