Nondestructive inspection apparatus and nondestructive inspection method for composite structure

A nondestructive inspection method for inspecting an inside of a surface layer of a composite structure using cosmic-ray muons traveling substantially in a horizontal direction while being spin polarized by a predetermined amount in a traveling direction, comprising the steps:

• (a) sampling with a discriminator, at a predetermined reference clock, a positron/electron amount reflection-emitted having a characteristic time constant in a direction opposite to an irradiation direction of the cosmic-ray muons with annihilation of two different muons, positive muons and negative muons, constituting the cosmic-ray muons stopping inside the composite structure;
• (b) removing a noise component from a sampled signal with the discriminator;
• (c) screening detection signals of the cosmic-ray muons from the signal with the noise component removed with the discriminator;
• and
• (d) processing the screened detection signals of the positive muons and the negative muons in the cosmic-ray muons with a radiography data processing means to generate radiography information,
• wherein an inside of the composite structure is inspected by obtaining the radiography information indicating a state of a second substance, different from a first substance of the surface layer, existing inside the surface layer of the composite structure, and
• the nondestructive inspection method is executed by a nondestructive inspection apparatus comprising
• positron/electron amount detecting means for detecting the positron/electron amount reflection-emitted having the characteristic time constant in a direction opposite to an incoming direction of the cosmic-ray muons by a decay of the cosmic-ray muons stopping inside the composite structure, and
• the radiography data processing means for monitoring the state of the second substance as radiography to output, from the positron/electron amount detected in the positron/electron detecting means,
• the positron/electron amount detecting means comprises
• a first detecting plate disposed on an incoming side of the cosmic-ray muons to detect a position and a path of the cosmic-ray muons to irradiate the composite structure,
• a second detecting plate disposed between the first detecting plate and the composite structure to detect the positron/electron amount produced by the decay of the stopping cosmic-ray muons in the composite structure, and
• a trigger counter disposed immediately before the composite structure to select the muons
• the positron/electron amount detecting means detects all positron/electron amounts reflection-emitted by the decay of two different muons, the positive muons and the negative muons, and
• the radiography data processing, means comprises
• the discriminator to sample an input signal from the positron/electron amount detecting predetermined reference clock to remove the noise component from the input signal and to select only the detection signals of the muons,
• a field programmable gate array (FPGA), and
• an Ethernet connector connecting a ROM circuit to process an output signal from the discriminator and a data processing means.