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Three types of rays emits continuously from a radium material. These rays are known as alpha rays (a rays), Beta
rays (p rays) and gamma rays (x rays). Gamma rays also know as xrays.
The frequency of xrays
as approximately
1020 Hz and its wave length is approximately 10"10 meter. Xrays
are electromagnetic wave which are widely used
in medical field and industries for inspection of human body or any other thing.
Production of Xrays
Xrays
can be produced with the help of high vacuum tube with a heater, cathode and anode. Vacuum tube is
operate at very high voltage. A special electron tube (vacuum tube) is shown in Fig No 11 which is used for
production of xrays.
Such a tube has a hot filament cathode an anode made a very heave metal. Electron flow from
the cathode to anode as in any diode tube. However a large DC voltage is used between cathode and anode of xrays tube. .
When heater is on and very high anode to cathode voltage is applied the electron emits from cathode and travel
toward the anode with very high Velocity, as clear from fig No11, this beam of electron strike the metal anode such
speed that new rays are made from the slanting surface of the anode these xrays
seem to bounce sideways ad out
thought the well of the tube. As the DC voltage (anodetocathode
of the xrays
tube) is increased, the wave length of
xrays
decreases. Same tubes now operate at more than a million volts.
Block Diagram of XRays
Machine
Operation/Working of XRay
Machine
High voltage source and high voltage transformer
High voltage source is responsible for providing high voltage to the H.V transformer for a decided time. The H.V
transformer produces 20 KV to 200 KV at the O/P. These voltages are used to determine the contrast of the image.
High voltages have higher contrast.
High voltage rectifier
This rectifier rectifies the high voltage produced by the H.V.T and supplies them to the anode of the Xray
tube.
Thermal overload detector
The heat of the Xray
tube (should not be increase by a specified range). If the heat is exceed from a specified value,
and then the thermal over load detector is used to turn off system.
Rotor control
Most of the Xray
tube anodes are rotated by an induction motor, in order to limit beam power at any spot and helps
to cool the anode.
Pulse duration timer