| 摘要 |
PROBLEM TO BE SOLVED: To provide an ionization chamber giving no influence to a signal supplied to a power supply lead wire to a measurement field electrode, without being reproduced in a radiogram. SOLUTION: This ionization chamber is separately placed on a board 120, and contains plural measurement field electrodes 131 provided with a power supply lead wire 134 and at least one electrode 180 which is separated from the board, placed opposite to the board and emits a change carrier under the influence of X-rays. Electrical insulating layers 140, 190 provided on the power supply lead wire 134 side and/or the electrode 180 side prevents a signal from the ionization chamber from being changed by the charge carrier entering into the power supply lead wire. The electrical insulating layer has so high X-ray transmittance that it is not practically reproduced in a radiogram.
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