Though potentially harmful, X-ray remains a valuable diagnostic tool.
X-ray is a form of electromagnetic radiation, much like visible light. Due to its short wavelength, it is capable of being transmitted through body tissues. In short, an x-ray machine transforms the kinetic (movement) energy of electrons into electromagnetic energy and thermal energy (heat). The production of X-ray is essentially unchanged since its discovery in 1895.
Requirements
X-rays are produced in a vacuum diode tube that is supplied with very high voltage electricity. The X-ray tube must be able to withstand very high temperatures and is typically made of Pyrex glass. Because the production of X-ray results in significant heat generation, the tube must be cooled with circulating water or oil during and after production. A high-voltage transformer is required to supply the tube with energy sufficient to produce X-rays, typically between 30 to 150 kilovolts (thousand volts).
Production
The cathode (negative diode) of the X-ray tube is electrified, causing thermionic emission. During thermionic emission, the cathode--a thin coil of metal such as tungsten or molybdenum--is heated, and electrons are "boiled-off". The anode (positive diode) is given a high positive charge, causing a strong electrostatic attraction between the electrons emitted by the cathode and the anode. The electrons travel across the vacuum tube and slam into the anode. The high kinetic (movement) energy of the electrons is abruptly transformed into electromagnetic (X-rays) and thermal (heat) energy.
Controlling the Quantity and Penetrating Power of X-ray
X-ray quantity and penetrating power are controlled by manipulating the electrical supply to the X-ray tube. The X-ray machine operator selects the amperage (rate of electron flow in the circuit), which ultimately determines the number of electrons boiled off the cathode during thermionic emission. As thermionic emission is increased, the quantity of X-rays produced in the tube is increased. The penetrating power of the X-rays is controlled by using a variable transformer to determine the positive charge of the anode. As the anode's charge is increased, the electrostatic attraction between the electrons and the anode is increased. Electrons strike the anode with higher kinetic energy and their energy is transformed into electromagnetic energy with higher penetrating power.
Tags: thermionic emission, into electromagnetic, X-ray tube, attraction between, attraction between electrons, between electrons