Development of micro-optics for high-resolution IL spectroscopy with a proton microbeam probe

Kada, Wataru; Sato, Takahiro; Yokoyama, Akihito; Koka, Masashi; Kamiya, Tomihiro

Combined techniques of PIXE and IL are currently investigated with proton microbeam for the precise analysis and imaging of microscopic targets. Spectroscopy of IL is able to characterize the chemical composition of the irradiation targets while the wavelength of the IL photons is strongly affected by the chemical-state of the elements. However, IL was not well obtained from the targets with size of micrometers comparing to the PIXE analysis because of the sensitivity and the S/N ratio of IL detection. In this study, we have developed a new optics for the IL measurement using confocal micro lens optics. Anti-reflection-coated convex lens was installed in a microbeam line of 3 MV single ended accelerator for in-air micro-PIXE analysis system. The focal points of the lens were set on the irradiation target and input terminal of optical fiber. The effective focus area on the target was approximately 800 800 um considering chromatic aberration of the IL photons ranging 300 to 950 nm. Electrically-cooled back-thin CCD spectrometer was used for the spectroscopic analysis of IL with a wavelength resolution of 0.5 nm in the range of 200 to 950 nm. The IL spectrum was clearly observed. The spectral analysis of IL was also applicable to the other natural mineral target and also particulate target like aerosols with different elemental and chemical compositions.