Activation technique was employed to determine the252Cf spectrum averaged cross section of the99Tc(n,n)99mTc reaction. Two different -spectrometric methods were applied. One of the measurements was relative to that of the cross-section value of115In (n,n)115mIn reaction, while the other one was absolute. The measured values are 179±49 mb and 195±43 mb for the relative and absolute measurement, respectively.
Authors:T. Sekine, K. Yoshihara, J. Sáfár, L. Lakosi, and Á. Veres
The99Tc (, 3n)96Tc and99Tc (, 4n)95Tc reactions were studied by irradiation of target99Tc with bremsstrahlung from the linear electron accelerator of Tohoku University, up to 50 MeV -energy. The resulting96Tc (4.3 d) and95Tc (20 h) activities were determined by -spectrometry. The -flux was monitored by the99Tc (,
)99mTc reaction. Metallic copper and gold foils were used as additional flux monitors in front of and behind the samples. Their measured radioactivity was utilized for normalizing bremsstrahlung flux calculations, in order to determine reaction cross sections. Cross sections were also determined theoretically, performing calculations in the framework of a neutron cascade evaporation model. Above the (, 3n) and (, 4n) threshold energies the neutron emission channel was supposed to be the only open channel for deexcitation following photoabsorption. The preeguilibrium contribution was considered negligible. The experimental results obtained for the integrated cross section at 30 and 50 MeV fit reasonably well the calculated curves.
Authors:J. Sáfár, L. Lakosi, I. Pavlicsek, A. Veres, T. Sekine, and K. Yoshihara
99mTc production was studied with the aid of photoexcitation by a 4 MeV endpoint energy bremsstrahlung from the LINAC of the Institute of Isotopes, Budapest. The intensity of the -flux was monitored by disc-shaped natural indium plates, placed in front of and behind the small cylindrical aluminium holders containing TcO2 samples in a powder form. Isomeric activities were measured through the 140 keV -line by a Ge spectrometer. The integral cross section at 4 MeV was found to be 63.3±7.1 bMeV, which can be considered reasonable compared to the corresponding value of 55.3 bMeV established for the115In (,
)115mIn reaction. We also attempted the photoexcitation of99mTc by irradiation with -rays from a 1.5×1015 Bq60Co source, but no isomeric activity could be observed. This places the first activation level between 1.33 and 4 MeV.