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.