Abstract: A control apparatus may include a processor for calculating a detection efficiency, which is detected by a gamma-ray detection unit, of gamma-rays emitted from a sample stuffed into a first container. A shape of the first container is a shape which surrounds at least a part of the gamma-ray detection unit that detects the gamma-rays. An area inside the first container is divided into a plurality of similar areas which is area similar in shape to each other. The gamma-ray detection unit detects the gamma-rays emitted from the sample included in each the similar areas for each of the plurality of similar areas. The processor calculates the detection efficiency as a similar-area-detection efficiency based on a result of detection performed by the gamma-ray detection unit.

Abstract: The internal refractive index distribution of an optical fiber preform is measured by providing a generally-cylindrical optical fiber preform having an uneven internal refractive index distribution. A picture image is placed at one side of the optical fiber preform, and a deflected picture of the picture image is photographed through the optical fiber preform using a photographing unit placed at the other side of the optical fiber preform. A deflection function is obtained by analyzing the deflected picture of the picture image. The internal refractive index distribution of the optical fiber preform is measured in accordance with the deflection function obtained.