production of X rays by the X-ray tube located in the
current from the power source to 2,000-cycle,
head. The unit also contains a heat exchanger and
single-phase current. It also circulates a coolant
through the X-ray tube head (views B and C) by means
X-ray tube parts. The head is charged with an insulating
of a radiator, water pump, and interconnecting hose.
gas (sulfur hexafluoride) to prevent electrical leakage.
The tube that actually produces the X rays is a vacuum
tube containing a negative and a positive terminal. The
The master control (fig. 11-1, view A), when
negative terminal is a filament that provides a source of
properly set up with the power supply and tube head
electrons. The positive terminal is a target at which the
(fig. 11-2), provides the means for energizing and
stream of electrons is focused. A high voltage applied
adjusting the kilovoltage and milliamperage of the tube
to the tube drives electrons from the cathode, or
head. A timer automatically indicates the elapsed
negative terminal, to the anode, or positive terminal.
exposure time, and de-energizes the tube at the
The higher the voltage, the greater the speed of the
completion of the exposure. Indicating instruments
electrons; resulting in a higher range of radiation.
show the kilovoltage and milliamperage of the X-ray
beam emerging from the X-ray tube window.
PRINCIPLES OF X-RAY GENERATION
The principle of X-ray generation is illustrated in
figure 11-3. Heat and X rays are generated when
rapidly moving, negatively charged particles
low voltage to the kilovoltage required for the
Figure 11-2.--Connections for portable X-ray machine.