| 摘要 |
<p>A radiation detector includes wavelength-shifting optical fibres which are selected and arranged to capture a greater percentage of visible photons through the use of two or more different colour stages of wavelength-shifting fibres. A primary set of optical fibres (50) contains a first wavelength-shifting optical fibre tuned to absorb photons emitted by the detector crystal (12) and to re-emit photons at a longer wavelength. At least some of the re-emitted photons from the primary set of optical fibres are captured and transmitted down the first wavelength-shifting optical fibre. A secondary set of optical fibres (54) contains a second wavelength-shifting optical fibre tuned to absorb photons emitted by the primary set of optical fibres and to re-emit photons at a still lower frequency. In this way at least some of the photons emitted by the primary set of optical fibres and not transmitted down the first optical fibre are captured and transmitted down the secondary optical fibre. An electro-optical device such as a PMT or photodiode is positioned to detect photons received from at least one end of the first or second wavelength-shifting optical fibres and to generate an electrical signal in response. <IMAGE></p> |
