Photoproduction of ${99}^mTc$ with Laser-Compton Scattering Gamma-ray

Abstract

This paper is concerned with new methods for producing the medical isotope $^{99}mTc$ using laser-Compton-scattering (LCS) photons. First, we investigate the processes and basic principles of $^{99}mTc$ photoproduction based on the giant dipole resonance (GDR) (γ, n) and nuclear resonance fluorescence (NRF) (γ, γ`) reactions. The GDR reaction produces $^{99}mTc$ by way of a (γ, n) reaction with the $^{100}Mo$ target. The GDR cross sections for relevant Mo isotopes are reported and discussed. In the case of the NRF reaction, $^{99}mTc$ is generated directly from the excitation of ground state $^{99}Tc$ and subsequent decay from unstable energy states to the isomeric state of $^{99}mTc$. The NRF cross-section of 99Tc was evaluated using the PHITS code and the probability of the decay to $^{99}mTc$ from various energy levels was determined using the ENSDF data. The paper then reviews and summarizes the principles of generating LCS gamma rays used in $^{99}mTc$ photoproduction along with the related reaction characteristics. After this review, the LCS gamma ray production is optimized for $^{99}mTc$ production using the so-called Energy Recovery LINAC (ERL) system as the baseline facility for the generation of LCS gamma rays. The spectrum of the LCS gamma-ray was optimized for the GDR cross-section and the NRF cross-section. In the case of the GDR reaction, the maximum energy of the LCS gamma-ray was optimized to about 16.5 MeV. In the case of NRF reaction, the maximum energy of the gamma ray was adjusted to the range of 1 to 2 MeV. This energy range includes the excited states contributing to the generation of $^{99}mTc$. In this paper, we also confirm the practicability of the NRF concept by evaluating the amount of ground state $^{99}Tc$ discarded from existing Tc generators. Through this study, it is confirmed that LCS gammas can be used effectively to produce $^{99}mTc$ by way of the photoproduction through the GDR reaction with $^{100}Mo$ and the NRF reaction with the $^{99}Tc$ present in radioactive waste from existing Tc generators.