New in-air micro-PIXE system for biological applications

Two unique apparatuses have been installed at in-air micro-PIXE system at JAERI Takasaki. One is a multiple X-ray detection system that consists of three X-ray detectors. The efficiency below 2 keV is greatly improved by a new high energy resolution Si(Li) detector, on the other hand higher energy region above 6 keV is covered by a backward X-ray detector that is set just behind a sample. The X-ray detection efficiency is drastically improved by the system. Another improvement is a sample cooling system that blows cryogenic gas (∼100 K) from liquid nitrogen onto the sample. This technique enables elemental mapping of a frozen raw biological specimen without serious irradiation damage. These improvements are very useful especially in biological applications.