Integration of an electron beam ion trap source into an electrostatic accelerator for pre-clinical cancer research

A commercial electron beam ion trap (EBIT) source has been integrated into the 5.0 MV Singletron accelerator at the Radiological Research Accelerator Facility (RARAF). Generally used as an injector for particle accelerators, it is the first integration of an EBIT source into a single-ended electrostatic accelerator, for cancer heavy-ion radiotherapy (HIRT) research. The EBIT source generates highly charged ions (B⁵⁺, C⁶⁺, etc.) in addition to light ions (protons, deuterons, and helium ions) produced by the standard High Voltage Engineering Europe (HVEE) configuration of the RARAF accelerator, i.e., using a radiofrequency ion source. Meeting the requirements for the operation of the EBIT source inside the pressure vessel of the accelerator required some structural, electrical, and vacuum modifications. With unconventional source materials for EBIT like propane (for carbon ions) and trimethyl borate (for hydrogen and boron ions), the integrated system delivers a series of mono-linear-energy-transfer beams that provide exposures to a cell monolayer for radiological work at RARAF. We discuss the methodology for integrating the EBIT source into an HVEE Singletron and optimizing ions of particular interest in HIRT.