Patent Number: 
Section: claims

1. A fluorescent screen configured to convert an X-ray into visible light, comprisinga gadolinium oxysulfide phosphor activated with praseodymium and cerium,wherein the phosphor contains praseodymium having a concentration of 0.01 mass % or more and 0.3 mass % or less and cerium having a concentration of 5 ppm or more and 30 ppm or less,wherein an average particle diameter of the phosphor is 10 μm or more and 20 μm or less, andwherein a weight per unit area of the phosphor is 300 mg/cm2 or more and 380 mg/cm2 or less. 2. The screen according to claim 1, wherein the concentration of the praseodymium is 0.03 mass % or more and 0.2 mass % or less. 3. The screen according to claim 1, wherein the concentration of the cerium is 10 ppm or more and 25 ppm or less. 4. The screen according to claim 1, wherein the weight is 300 mg/cm2 or more and 350 mg/cm2 or less. 5. The screen according to claim 1, wherein the average particle diameter is 13 μm or more and 18 μm or less. 6. The screen according to claim 1, wherein a Wadell's sphericity of the phosphor is 0.8 or more and 0.96 or less. 7. An X-ray detector configured to detect a transmitted X-ray from a target, comprising the screen according to claim 1. 8. The detector according to claim 7, further comprisinga photodiode configured to convert the visible light into an electrical signal. 9. An X-ray inspection apparatus, comprising:an X-ray irradiator configured to irradiate an X-ray to a target;an X-ray detector configured to detect a transmitted X-ray through the target; anda display configured to display an image of the inside of the target in accordance with an intensity of the transmitted X-ray detected by the X-ray detector,wherein the detector includes the detector according to claim 7.