Patent ID: 9523776
Filing Date: 2016-12-20
CPC Classification: G01T

Claim Text:
1. A radiation detector comprising: a light collecting member that can collect observation light based on light emission of gas caused by alpha rays; a photo detector that can receive light collected by the light collecting member and count number of photons; a wavelength selector that is disposed on an optical path at an upstream side of the photo detector and can selectively transmit light based on the light emission of gas caused by alpha rays by selectively transmitting light of a wavelength in a specific range; a counting unit that is configured to calculate an alpha dose based on a difference subtracting a number of noise photons at the photo detector under a first condition where the light emission of gas caused by alpha rays is not collected to the photo detector, from the number of photons detected at the photo detector under a second condition where light emission of gas caused by alpha rays is collected to the photo detector; and a polarization selecting element that is disposed on an optical path at an upstream side of the light collecting member and reduces incidence of light other than the light based on light emission of gas caused by alpha rays that enters the photo detector depending on a polarization direction, by selecting a direction of the light that has been linearly polarized in which noise light is weakest so as to reduce noise light included in the observation light.