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The feasibility of producing the short-lived tracers 11 c, 13N, 15o, and 18F with heavy-ion beams was investigated. Production cross sections for 15-MeV p$ 75-MeV 3He and 300-MeV 12c beams incident on H20 targets were calculated using the particle evaporation code ALICE(~). These calculations predicted substantial thick target yields of all four activities with the heavier beams. Experiments were performed with 15-MeV p and 75-MeV 3He beams to check the accuracy of the theoretical calculations. Absolute product yields were measured with Nal well counters, and chemical composition vJas determined by GC and HPLC. For several years we have been developing techniques for the production, purification and utilization of the short-lived tracer 13N (t1 = 9.96 min) in our studies biologi nitrogen transformations (J_,£). ~ Sources of 13N were typically produced by the 16o(p,4He) 13N reaction using 15-MeV protons from the Michigan State University Cyclotron to bombard natural H20 targets. This beam energy was chosen to optimize the production of 13N without significant contamination from 11 c and 150 which are produced at higher beam energies. Small amounts of 18F were produced from the 18o(p,n) 18F reaction; however, this did not interfere with our experiments. The sources varied in chemical purity containing typically about 85% No3 . d , 3 + 13Nod o ( %) with the rema1n er NH4 , 2 an small amounts of labeled N2 and N2 < 2~ . Purified sources of all these species were routinely obtained by fast chemical techniques, gas chromatography (GC) and high pressure liquid chromatography (HPLC). With the closing of the low energy accel.erator at Michigan State University and the subsequent construction of a new heavy-ion facility there, it was desirable to investigate the feasibility of producing 13N with the less optimal heavy-ion beams. Although it was anticipated that the heavyion reactions would produce substantial quantities of 11 c, 15o and 18F, we hoped that simple chemical techniques, which we had already developed, would be adequate to purify the sources. Thus, if sufficient quantities of 13N were produced by heavy-ion reactions it would be possible to continue our tracer studies with these beams. Two methods were chosen to investigate the usefulness of 13N production by heavy-ion beams. First we performed theoretical calculations of 13N yields with 15-MeV p, 75-MeV 3He, and 300-MeV 12c beams on water targets (typical MSU energies) using the particle evaporation code ALICE (l). Then we experimentally tested the accuracy of these calculations by producing 13N activity with a 75-MeV 3He beam from the Michigan State University Cycletron. This beam should produce similar reactions and experimental conditions to those expected for heavier ions of the same energy to mass ratio. Sources produced by the 3He beam were analyzed by decay half-life, HPLC and GC to determine absolute yields and chemical composition. Comparisons between this analysis of 3He induced products, previous 15-MeV p experimental results and the ALICE calculations were then made to determine both the usefulness of the calculations and the feasibility of producing experimentally useful short-lived isotopes with heavy-ion bombardments. ALICE Calculations 11 13 15 18 Cross sections for the production of c. N, 0 and F were calculated for 15-MeV p. 75-MeV 3He. and 300-MeV 12c beams incident on natural H20 targets using the particle evaporation code ALICE (l). This program was used to calculate the total p + n +a evaporation cross sections for all partial waves assuming the parabolic model (!) to determine the compound nucleus cross section and using the n,p. and a binding energies of Wapstra (.~). The thick tqrget yields for the isotopes were then calculated by integration using the ALICE cross sections and the particle range tables in Lederer et al. (~). These yields are shown in Table 1 where they are expressed in the units mCi/~A per 10 min bombardment and corrected for decay during irradiation. For 3He and 12c the calculations assume a particle beam current and not a charge current. In Figures 1-3 we have shown the calculated thick target yields of 11 c, 13N, 15o and 18F as a function of incident beam energy. Here the yields are expressed in the units mCi/~A per second. To calculate the yield for a given bombardment interval one should use the relation

The Feasibility of Producing 11C, 13N, 15O, and 18F with Heavy-Ion Beams

The Feasibility of Producing ¹¹C, ¹³N, ¹⁵O, and ¹⁸F with Heavy-Ion Beams