Speaker
Description
The modern medical method of nuclear visualization based on monoclonal antibodies, the new carriers of the radioactive label, is Immuno-PET. For its realization, it is necessary that the biological half-life of the molecule, the label carrier, coincides with the half-life of the radioactive isotope. The $^{89}$Zr isotope has optimal physical characteristics for Immuno-PET: it decays with a half-life of 78.41 hours by positron emission and electron capture to the intermediate state $^{89m}$Y, which decays to stable $^{89}$Y with half-life 15.7 s.
Traditionally, $^{89}$Zr is produced with cyclotrons in the ($p, n$)- and ($d$, 2$n$)-reactions. However, in both methods, the exclusion of $^{88}$Zr isotope impurities with a half-life of 83.4 days and its daughter $^{88}$Y isotope with a half-life of 106 days resulting from ($p$, 2$n$)- or ($d$, 3$n$)-reactions presents a significant problem.
Therefore, an urgent task is to study the $^{89}$Zr yield in various photonuclear reactions.
We irradiated a $^{94}$Mo enriched molybdenum target and a tantalum monitor target using an electron accelerator with a 20 MeV maximum electron energy.
The spectra of irradiated targets were measured by Canberra and Ortec gamma spectrometers with ultra-pure semiconductor detectors with a (15–40)% detection efficiency compared to a 3′×3″ NaI(Tl) detector. The energy resolution of the spectrometers was 1.8–2.0 keV on the 1332 keV $^{60}$Co γ-line. In the studied spectrum, γ-transitions from $^{89}$Zr decay are reliably identified. The bremsstrahlung spectrum was simulated using the Geant4 software code.
As a result, we obtained the integral cross-section for the $^{94}$Mo(γ, $n$)$^{89}$Zr reaction equal 4.5 mbn×MeV. The $^{89}$Zr yield is 5×10$^4$ Bq×μA×hour. Obtained data are discussed.
