Design of apparatus for precise x-ray dose chamber calibrations

An apparatus for precision calibration of ion chambers in the x-ray region from 16 to 320 kV is described. The development of a fast-acting shutter with "opening" and "closing" times of less than 3-ms eliminates the requirement for operating time corrections. Controls from outside the radiation room permit changing x-ray filters and alternately positioning both test and standard ion chambers in the x-ray beam. Thus, the remote controls eliminate the need to enter the x-ray room in the course of a series of calibrations. The potential advantages resulting from the capabilities of this apparatus are described in this Technical Report.