BETATRON (RT): A circular electron accelerator that is a source of either high energy electrons or X-rays. The
electrons are injected by periodic bursts into a region of an alternating magnetic field. After acceleration, the electrons
are brought out directly or directed against a target to produce X-rays.
BLACK LIGHT (PT, MT): The term given to electromagnetic radiation having wavelengths from 320-400 nm.
Typical units used in penetrant inspection provide an intensity of 100 to 150 foot-candles at 15 inches from the lace of
the filter and are used to excite fluorescent materials in a range visible to the eye.
BLACK LIGHT INTENSITY (PT, MT): The amount of properly filtered black light measured at the surface of the part
BLACK LIGHT FILTER (PT, MT): A filter that transmits ultraviolet light (320-400-nm wavelength) while
suppressing the transmission of visible light of the longer wavelengths.
BLEED OUT (PT): The action by which the penetrant exudes out of the discontinuities onto the surface of a
component, due primarily to capillary action and to blotting or soaking up effect of the developer.
BLISTER: A defect in metal on or near the surface, resulting from the expansion of gas in a subsurface zone. Very
small blisters are called pinheads or pepper blisters.
BLOCKING: See MASKING.
BLOCKING MEDIUM (RT): Material of appropriate radiation opacity for applying to an object, either around the
edges or as a filling for holes, to reduce the effect of scattered radiation and to shield portions of the film which would
otherwise be overexposed (e.g., radiographic putty).
BLOTTING (PT): The action of the developer in soaking up the penetrant from the surface of the discontinuity, so as to
cause maximum bleed out of the dye penetrant for increased contrast and sensitivity.
BLOWHOLE: A hole in a casting or a weld caused by gas entrapped during solidification. See POROSITY.
BLUR (RT): See unsharpness; penumbra.
BODY (PT): The term used to describe the ability of a penetrant vehicle to maintain an adequate suspension of visible
or fluorescent dye material.
BODY BURDEN: The amount of radioactive material present in the body of man or animals.
BOLTHOLE PROBE (ET): A probe coil(s) assembly used for electromagnetically inspecting the walls of fastener holes
or other small holes of limited length.
BOLTHOLE SCANNER (ET): An eddy current device designed to provide automatic, uniform inspection of walls of
BOTTOM ECHO (UT): See BACK REFLECTION.
BOUNDARY ECHO (UT): A reflection of an ultrasonic wave from an interface.
BOUNDARY WAVELENGTH (QUANTUM LIMIT) (RT): The shortest wavelength present in a continuous X-ray
spectrum. It is inversely proportional to the peak voltage applied to the X-ray tube.
BRAZING: Joining of metals and alloys by fusion of nonferrous alloys that have melting points above 800°F, but lower
than melting points of materials being joined.