Design of a low background mass spectromenter for a high sensitive analytical ion microscope

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The design of a double fousing mass spcectrometer has been attempted as a part of a highly sensitive analytical ion microscope for the isotope analysis of solid samplesd. It has the follwoing capabilities; (1) high mass resolbing power of about 3200, (2) high sensitivity with a wide dynamic range of 5 orders of magnitude and (3) high accuracy of measurement of about (+-)0.5%. We calcuated the ion optical parameters of the mass spectrometer using "the program for a personal computer" by Matsuda (1983) in the journal of Mass Spectroscopy. The results of the calculation is as follows; electric field: 75゜ in deflection angle and 40cm in rafidus, magnetic field: 90゜ in deflection angle and 20cm in radius and mass resolving power: 3400 2( 100um width of a collector slit. Based on this design, An analyzer chamber, an electro-matnet, a momwntum analyzer and its chamber wete constructed. A controlling circuit for evacuation system has been designed and consttucted, this can be connected to a personal computer through an interface and relays.These were tested for vaclum and the ultimate pressure of the system ha benn attained to be about 1 X 10^<-7> Torr without any baking of the chambe. As for an electro-magnet, magnetic field at the cenger of of pole pieces was found to be able to sweep over the trange 0-5000 Gauss. This range corresponds to the mass range of 0-250 at an ion accelecrating voltage of 2kV.Therfore, this double focusing mass spectrometer can be used as a detector of a highly sensitive analytical ion microscope.