Roundness and straightness measurement of ceramic beam ducts for the 3 GeV-synchrotron of Japan-Proton Accelerator Research Complex

Cylindrical beam ducts with large aperture (∼φ200 mm) made of alumina ceramics are used in the 3 GeV-synchrotron of Japan-Proton Accelerator Research Complex (J-PARC). A longer ceramic beam duct with about 3500 mm long is indispensable to the bending magnet sections. A beam duct is manufactured in such a way that several unit ducts of which length is from 500 mm to 1000 mm are connected by metallizing and glazing. It is very important to evaluate roundness and straightness of unit ceramic ducts because we have to keep a large beam aperture and have to compensate for the contact area of unit ducts to be large. We developed an apparatus for measuring roundness and straightness using two digital micro gauges, and we completed the algorithm to evaluate roundness and straightness from measured data by use of 'Excel worksheet'. We have evaluated these form deviations of fifteen ceramic unit ducts. The unit ducts have been manufactured with sintering, the obtained roundness and straightness are several hundred microns and about 200 μm - 1000 μm respectively with no polishing. The roundness of unit ducts increases proportional to the oblateness of the ducts. (author)