Abstract: An ionization chamber radiation detector includes an outer shell, an inner well electrically connected to the outer shell to define an ionization chamber sensitive volume between them, and an ionization electrode that extends upwardly from a base into the space between the side walls of the well and shell. The shell and the walls of the well are grounded while the ionization electrode, which is electrically insulated from the shell, has a high voltage applied thereto. A guard electrode at the same voltage prevents electrical leakage. A sample positioner includes a thin walled guide tube which extends from a top cap down to a spacing disc. The spacing disc has an outer periphery which closely matches the interior of the well so that when the positioner is inserted into the wall the guide tube will be held at a desired position, preferably at the central axis of the well.

Abstract: An ion chamber for use with analysis and alignment of radiation therapy equipment is disclosed which includes a one millimeter deep ion chamber formed by a cavity in the front of a core member which is closed at its upper end by a thin electrode stretched and held in place over the cavity. A guard ring around the collecting electrode is maintained by a coated layer formed on the surface of the core inside of the cavity. Suitable conductive layers applied to the core connect to the various conductors of a triaxial cable so that the front electrode, the ion collecting electrode, and the guard ring electrode, can all be relatively easily connected to the single triaxial cable connected to the ion chamber. Components of the ion chamber are all, with the exception of the front electrode and the ion collecting electrode, fabricated of a single uniform material having known and defined radiation transmission properties so that radiation field discontinuities and perturbations are not generated within the instrument.

Abstract: A probe (10) employs a scintillator (18) as a detector for high-energy beam dosimetry. The scintillator (18) is positioned in an ionizing radiation beam (52) which creates a light output that is proportional to the radiation dose-rate incident upon the scintillator (18). The light is conducted from the scintillator (18) through a light pipe (16) to a photomultiplier tube (28), which converts the light to an electric current. The scintillator (18), the light pipe (16), the photomultiplier (28), and associated optical connections have opaque coverings or sheaths to prevent extraneous light from being introduced into the probe (10). The electric current produced by the photomultiplier tube (28) is proportional to the radiation dose-rate incident upon the scintillator (18). The radiation dose-rate may then be displayed or recorded by a measurement of the electric current.