| abstract |
A polycrystalline scintillator for detecting soft X-rays contains Ce as a light-emitting element, and at least Y, Gd, Al, Ga and O, has a garnet crystal structure, and has a composition represented by the following general formula: (Y 1-x-z Gd x Ce z ) 3+a (Al 1-u Ga u ) 5-a O 12 (wherein 0 ≤ a ≤ 0.1, 0.15 ≤ x ≤ 0.3, 0.002 ≤ z ≤ 0.015, and 0.35 ≤ u ≤ 0.55) The Fe content is 0.05 to 1 ppm by mass exclusively; the Si content is 0.5 to 10 ppm by mass exclusively; the μ 50 /μ 100 ratio of the absorption coefficient of a 50 KeV X-ray (μ 50 ) to the absorption coefficient of a 100 KeV X-ray (μ 100 ) is at least 3; and the afterglow 3 ms after the X-rays have stopped is not more than 800 ppm. |