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X-ray photograph • x-y recorder 761
a picture made without a camera by interposing
an object (such as a part of the human body) between
an X-ray tube and photographic film.
X-ray radiation See X RADIATION.
X rays Invisible, electromagnetic radiation having
wavelengths ranging from approximately 0.01
nanometer (10 –11 meter) to 0.15 nanometer (1.5 ×
10 –10 meter). These waves are shorter than ultraviolet,
but longer than gamma rays. They can be
produced by bombarding a target of heavy metal
(such as tungsten) with a stream of high-speed
electrons in a vacuum tube. X rays have high
penetrating power, can expose photographic film,
and cause some substances to fluoresce. Also see
X-RAY DIAGNOSIS, X-RAY INSPECTION, and
X-RAY THERAPY.
X-ray spectra The continuous band of ionizing
electromagnetic radiation having wavelengths
ranging from approximately 0.01 nanometers to
0.15 nanometers.
X-ray spectrograph A spectrograph used to disperse
and measure the wavelength of X rays.
X-ray spectrometer A spectrometer with which
the diffraction angle of X rays reflected from the
surface of a crystal can be measured. The device
allows the characteristics and composition of almost
any material to be studied.
X-ray star A collapsed star that emits high-intensity
energy concentrated mainly in the X-ray region
of the electromagnetic spectrum.
X-ray system Collectively, an X-ray tube and the
associated equipment required for a specific application,
such as crystallography, irradiation, or
medical therapy.
X-ray technician 1. A professional skilled in the
operation and maintenance of X-ray systems,
who usually works under the supervision of an
engineer. 2. A professional skilled in the medical
use of X rays, who works under the supervision of
a medical doctor.
X-ray therapy The use of X rays in the treatment
of certain physiological diseases.
X-ray therapy system An X-ray system designed
for X-ray therapy.
X-ray thickness gauge An instrument used to
measure the thickness of metal, such as a continuously
moving sheet of steel. The measurement
is in terms of the amount of absorption of
an applied X-ray beam by the metal.
X-ray tube
A specialized, very-high-voltage diode in
which a high-speed electron beam bombards an
anode (target) of heavy metal, such as tungsten,
Anode
(target)
X rays
Electron
beam
X-ray tube
Cathode
causing it to emit X rays. The target is tilted to reflect
the X rays through the glass wall of the tube.
X section Abbreviation of cross section.
X sink The circuit or device into which the X lines
of a memory matrix feed. Compare Y SINK.
X T Symbol for total reactance.
xtal Abbreviation of CRYSTAL.
xtalk Abbreviation of CROSSTALK.
x unit A small unit of length, equal to approximately
10 -13 meter or 10 -4 nanometer. Now seldom
used, the x unit was once often used in the
expression of ultraviolet and X-ray wavelengths.
X wave One (the extraordinary) of the pair of components
into which an ionospheric radio wave is
divided by the earth’s magnetic field. Compare
O-WAVE.
XXX In radiotelegraphy, a signal meaning urgent.
X-Y counting A technique used with electronic
counters to determine the ratio of one frequency
(X) to another (Y). When X is the higher frequency,
the counter readout shows the number
of pulses of X producing one cycle of Y.
XY-cut crystal A piezoelectric plate cut from a
quartz crystal at such an angle that its electrical
characteristics fall between those of the X-cut
and Y-cut crystal.
x-y plotter An output device similar to the x-y
recorder. It allows a digital computer to plot
graphs. Also called data plotter.
x-y recorder An instrument that produces a permanent
record (photographic print or directly
inked paper) of a variable quantity on a chart
having Cartesian (rectangular) coordinates.