Proton Beam Based Production of Positron Emitters by Exploiting the 27al(p,x)22na Reaction

Positron annihilation experiments on an laboratory scale depend on the supplyand the availability of β^+ emitters. Here we present the production ofpositron sources based on the ^27Al(p,x)^22Na reaction by irradiationof Al with a 68 MeV proton beam. We simulated the energy loss, range andradial scattering of the protons in Al in order to design a simple targetconsisting of a stack of Al discs. Our approach allows (i) the direct use ofthe Al discs as positron emitters that inherently avoids wet chemical processesas usually applied in commercial production of carrier-free ^22Na, (ii) theproduction of multiple positron sources at once, and (iii) the simplemeasurement of the depth and lateral distribution of ^22Na. We preciselydetermined the cross section of the ^27Al(p,x)^22Na reaction which wasfound to differ from literature values particularly for proton energies between27 and 40 MeV. The activity of all nuclides produced (apart from ^22Na)was shown to be negligible 15 days after irradiation. The production ofradionuclides such as ^48Sc, ^54Mn and ^56Co can be prevented byusing Al of a higher purity. The concept presented here can easily be adaptedfor the production of stronger ^22Na sources by increasing the protoncurrent or/and the irradiation time.