| 摘要 |
PURPOSE: To improve the detecting sensitivity to make high precision thickness measurements using a weak radiation source by increasing the working gas charging pressure of an ionization chamber-detector use for radiation thickness meters for measuring the thickness of paper sheets by the use ofβrays. CONSTITUTION: In order to restrict the direction of radiation incident to an ionization chamber system radiation detector, a perforated body is provided so that it can adhere to a radiation entrance window-foil 42 of the ionization chamber. A part of stress produced in the entrance window-foil 42 by the pressure of working gas charged in the ionization chamber is adapted to be allotted to the perforated body. Then, the perforated body is made up of two plate-like bodies in which the openings of the same form and of the same size are arranged at the same positions. One of the plate-like bodies is closely locked to the entrance window-foil 42 of the ionization chamber, and the other is locked through spacers 72 so that the positions of openings of the plate-like perforated bodies 62, 63 locked to the entrance window-foil are overlapped with each other.
|
