Measurements of Activation Products Associated with Havar Foils from a GE PETtrace Medical Cyclotron Using High Resolution Gamma Spectroscopy

Abstract

Havar foils are specially engineered for beam-line windows used in the General Electric (GE) PETtrace medical cyclotron that can withstand the high pressure differentials and also temperatures developed near the target with proton bombardment. These foils effectively separate components along the beam line of the cyclotron. Various activation products are produced in the foils from the primary proton beam and other secondary radiations. An accurate estimate of the activation products is necessary for the disposal of these foils. The foils were assayed using two High Purity Germanium (HPGe) detectors calibrated over a wide energy range. These were positioned at different distances (0.10 m, 0.24 m, and 1.74 m) away from the detector faces to accommodate their high activities. A summary of the anticipated relative abundance of each activation product and a scatter plot of the average exposure rate per unit charge incident on the foil vs. time post-activation are provided. A detailed spectral analysis of the foils in the energy ranges between 12 keV to 300 keV and 12 keV through 2,500 keV revealed the residual activation products ⁵⁶Co, ⁵⁷Co, ⁵⁸Co, ⁵⁴Mn, and ¹⁸³Re at 264 d post-irradiation. Spectral examinations of the different foils removed between 2003 and 2005 show the same activation products regardless of the irradiation time or foil position in the target assembly. The information presented in this paper can be used along with the integrated charge incident on the foils in estimating the activity of Havar foils for the purpose of disposal.