A capillary array includes a capillary region, including capillaries of a first glass, which are disposed in an axis-parallel manner. A low refractive index layer is disposed on an inner wall of each of the capillaries, the refractive index of each low refractive index layer being less than a refractive index of a liquid scintillator. A second glass material is disposed between adjacent capillaries. A softening point of the first glass is T.sub.1, a softening point of second glass is T.sub.2, and a value of T.sub.1 minus T.sub.2 is in a range from 30 C. to 50 C. A thermal expansion coefficient of the first glass is .sub.1. An edge covering region is disposed on an outer side of the capillary region and makes contact with an outer side face of the capillary region, wherein a material of the edge covering region is a third glass.

A capillary array includes a capillary region, including capillaries of a first glass, which are disposed in an axis-parallel manner. A low refractive index layer is disposed on an inner wall of each of the capillaries, the refractive index of each low refractive index layer being less than a refractive index of a liquid scintillator. A second glass material is disposed between adjacent capillaries. A softening point of the first glass is T.sub.1, a softening point of second glass is T.sub.2, and a value of T.sub.1 minus T.sub.2 is in a range from 30 C. to 50 C. A thermal expansion coefficient of the first glass is .sub.1. An edge covering region is disposed on an outer side of the capillary region and makes contact with an outer side face of the capillary region, wherein a material of the edge covering region is a third glass.