Cyclotron produced ⁴⁴gSc from natural calcium

Abstract

(44g)Sc was produced by 16MeV proton irradiation of unenriched calcium metal with radionuclidic purity greater than 95%. The thick target yield at saturation for (44g)Sc was 213 MBq/μA, dwarfing the yields of contaminants (43)Sc,(44 m)Sc, (47)Sc and (48)Sc for practical bombardment times of 1-2h. Scandium was isolated from the dissolved calcium target by filtration, and reconstituted in small volumes of dilute HCl. Reactions with the chelate 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) indicated a reactivity of 54 ± 14 Gbq/μmol at end-of-bombardment.

Figure 1

Estimated thick target EOSB yields for production of ^44gSc, ^44mSc and ⁴³Sc as a function of proton bombardment energy. This represents yields from an unenriched natural calcium metal target with the isotopic ratios listed in Table 2. The values curves were calculated using the cross-section data from Levkovskij (1991) and proton ranges from SRIM (Ziegler, 1985). Note: This graph shows saturation yields. When estimating a production yield, irradiation time must be considered.

Figure 2

The average elution profile of ^44gSc from the membrane filter. Elution is performed with hot 0.1 M HCl, roughly 150μl at a time.

Figure 3

Representative results of DOTA-Sc titrations with two di3erent grades of calcium target, along with the expected curve for carrier-free ^44gSc. The reactivity of each measured sample is listed next to the curve, corrected to EOB. The carrier-free curve assumes log k = −26 and 75 μCi ^44gSc in 200 μl bu3er.

Figure 4

Radionuclidic purity of ^44gSc as a function of time after start of irradiation. The bold line represents the radionuclidic purity as a function of irradiation time, and the dashed lines show the purity of decaying samples after 1 hour and 4 hour irradiations.

Figure 5

Activity balance of scandium radioisotopes as a function of time after a 1 hour irradiation of a thick target at 16 MeV.