Preliminary Results of the Beam Control and Detection of the Kirams Electron Microbeam System

The use of microbeam techniques in radiobiology dates back to the 1920’s with the work of Tschachotin who irradiated the spawn of sea urchins and frogs with X-ray and ultraviolet light. In 1953, Zirkle and Bloom designed and constructed a microbeam facility [1] that utilized a 2 MeV proton beam of 2.5 m in diameter. Their facility, however, did not allow counting the radiation particles that entered individual target cells. Since then, various facilities utilizing protons, alpha particles, and heavy ions have been developed and improved through the technical advancements of optical lenses, particle delivery systems, beam focusing and detection systems, cell imaging systems, and computer controls. New techniques of assaying individual cellular response have further enhanced the biological research work performed in microbeam facilities. The microbeam irradiation device for single cell targeting was devised originally to remove the statistical uncertainty regarding individual cells being hit by radiation in a low-dose environment [2]. The microbeam facilities developed in 1990’s [3-5] have been used to study the cellular response to single cell targeting with protons, alpha particles, and X-rays. To date, the bystander effect [6] and genomic instability [7] have been the major observations of microbeam experiments. Utilizing an electron beam for microbeam experiments has been of interest in recent years [8-11], though any significant results have not been reported so far. The Korea Institute of Radiological and Medical Sciences (KIRAMS) electron microbeam system is designed to enable the target cells in vitro to be selectively irradiated with low-energy, low-current electrons [9]. Though the basic scheme of the KIRAMS electron microbeam system is similar to that of other charged-particle microbeam systems, it must overcome additional difficulties, such as controlling an electron path under the influence of the environmental magnetic field, delivering low-energy electrons to the target cells through a scattering medium, and maintaining a stable, low-current electron beam. This paper describes the prototype components of the KIRAMS electron microbeam system and presents the preliminary results of the performance test on the beam control and detection.