ISOL ion source for heavy ion cancer radiotherapy

A new singly charged ion source using electron impact ionization has been developed to realize an ISOL (Isotope Separation On-Line) system for a PET imaging simultaneously with the heavy-ion cancer therapy using radioactive ¹¹C ion beams. Because the singly charged ion source is required to have high ionization efficiency, effective flight paths of the electrons emitted from the cathode have to be extended. For that reason, magnetic field is applied in the ionization region of the ion source and its direction is set parallel to that of the ion extraction. To decide the geometric parameters of the ion source, ionization efficiency was estimated considering balance among inflow of molecules and outflow of molecules/ions from the ionization region. Based on those considerations, the electron bombardment ion source was designed and fabricated. Details of the design and experimental results showing its fundamental performances are to be presented. (author)