MeV ion beam extraction into air with a glass capillary filled with He

In order to obtain an intense ion beam, we have newly developed He-capillary optics, which is a tapered glass capillary filled with low pressure He gas to extract ion beam into atmospheric air. We have measured the energy spectra of an ion beam extracted from the He-capillary as a function of He gas pressure. We have observed that the intensity of the extracted ion beam is enhanced by using the He-capillary with He gas, although peak energy is shifted to a lower energy. Furthermore, in order to evaluate the performance of the He-capillary in detail, we have measured the intensity distribution of the ion beam via the He-capillary by using a 25 µm pinhole slit and have found that the He-capillary optics provides an intense ion beam without further spread of the extracted ion beam. Here, we discuss transmission properties of the ion beam via the He- capillary.