A porous hexagonal boron nitride powder compact for the production and release of radioactive 11C

Abstract A porous pre-sintered hexagonal boron nitride powder compact was recently developed as target for the production of intense 11 C beams for Positron Emission Tomography-aided hadron therapy. In a previous study, this target has been characterized regarding its operational limitations. In this work, microstructural characterization with respect to the target's grain size, porosity and pore structure, and a dedicated fractional release study from activated targets, i.e. how much 11 C is extracted by a short heat treatment, is presented. Corresponding results include an average grain size of approximately 1.7 ( 1 ) μ m , total and open porosity of 40 ( 5 ) and 21 ( 7 ) % , respectively, which is mostly composed of pores with sizes ranging from 120 to 470 nm . From the measured release fraction the order of magnitude of carbon's diffusion coefficient D ( 1500 ° C ) = 10 − 15 − 10 − 14 cm 2 s − 1 in porous boron nitride, and a 11 C extraction efficiency of about 10 % at 1500 ° C target temperature were estimated.