Non-destructive testing by stimulated electron emission capture

Method for measuring the mass density of a test specimen, said method comprising the steps of:

• sandwiching said test specimen and a calibration specimen, said calibration specimen having a known mass density, between an electron source fabricated of a material having a high atomic number and a capture film sensitive to incident electrons in such a way that the test specimen and calibration specimen are not stacked with respect to each other;
• bombarding the specimens, electron source, and film with medium-to-high-energy photons;
• recording, on the film, densities of exposure attributable to trapped electrons originating from the source and stimulated into emission as a result of the photon bombardment, said stimulated electrons having passed through the specimens and exposed the film;
• subtracting, from the recorded film densities of the previous step, densities attributable to X-ray and chemical fog darkening of the film, so as to obtain net film densities corresponding to each of the test specimen and the calibration specimen;
• and
• measuring the mass density of the test specimen on the basis of its being substantially equal to the net film density corresponding to the calibration specimen multiplied by the mass density of the calibration specimen divided by the net film density corresponding to the test specimen.

A method for comparing the mass density distributions of first and second test specimens, said method comprising the steps of:

• sandwiching each test specimen between an electron source fabricated of a material having a high atomic number and a capture film sensitive to incident electrons in such a way that the test specimens are not stacked with respect to each other;
• bombarding the specimens, electron source, and film(s) with medium-to-high-energy photons;
• recording, on the film(s), densities of exposure attributable to trapped electrons originating from the source and stimulated into emission as a result of the photon bombardment, said stimulated electrons having passed through the specimens and exposed the film(s);
• subtracting, from the two recorded fiml densities of the previous step, film densities attributable to X-ray and chemical fog darkening of the film(s), so as to obtain two net film densities;
• and
• comparing the mass density distributions of the specimens on the basis of their being substantially inversely proportional to said two net film densities of the previous step.

Apparatus for measuring the thickness of a test specimen, said apparatus comprising:

• means for emitting a medium-to-high-energy beam of photons;
• an electron source disposed to receive the photon beam and to generate in response thereto a stimulated beam of emergent electrons generally oriented to interrogate said test specimen;
• and
• a capture film disposed to record electrons transmitted by said test specimen;
• wherein
• the test specimen is sandwiched between the electron source and the capture film, and absorbs and scatters some of the electrons in the emergent electron beam, wherein the electrons not absorbed and not widely scattered by the test specimen ionize the capture film in relation to the thickness of said specimen acting to absorb and widely scatter electrons which may otherwise be transmitted to expose said capture film;
• said apparatus further comprising a calibration specimen in the form of a step tablet of known material and having a series of graded thickness layers transcending the range of electrons emergent from said electron source;
• wherein
• the calibration specimen is sandwiched between the electron source and the capture film but is not stacked with respect to the test specimen, and absorbs and scatters some of the electrons in the beam, such that electrons not absorbed and not widely scattered by the calibration specimen ionize the capture film in relation to the thickness of said graded thickness layers, for comparison to the response of said capture film to the test specimen.

A method for measuring the thickness of a test specimen, said method comprising the steps of:

• sandwiching a test specimen and a calibration specimen, the calibration specimen having a known thickness and the same mass density as the test specimen, between an electron source fabricated of a material having a high atomic number and a capture film sensitive to incident electrons in such a way that the test specimen and calibration specimen are not stacked with respect to each other;
• bombarding the specimens, electron source, and film with medium-to-high-energy photons;
• recording, on the film, densities of exposure attributable to trapped electrons originating from the source and stimulated into emission as a result of the photon bombardment, said stimulated electrons having passed though the specimens and exposed the film;
• subtracting, from the recorded film densities of the previous step, densities attributable to X-ray and chemical fog darkening of the film, so as to obtain net film densities corresponding to each of the test specimen and calibration specimen;
• and
• measuring the thickness of the test specimen on the basis of its being substantially equal to the known thickness of the calibration specimen multiplied by the net film density corresponding to the calibration specimen divided by the net film density corresponding to the test specimen.