In anodes for physical strength and stability. Why are arcing and tube failure no longer major problems in modern x-ray tube design? Pass an electric current to heat a conductor and cause outer-shell electrons to be released from the conductor.
What addition to the filament material prolongs tube life? What is the reason for the filament to be embedded in the focusing cup? Is the anode or the cathode the negative side of the x-ray tube? What are the three functions the anode serves in and x-ray tube? X-ray tube target, electrical conductor, mechanical support, and thermal radiator.
How do atomic number, thermal conductivity, and melting point affect the selection of anode target material? How does the anode rotate inside a glass enclosure with no mechanical connections to the outside? Induction motor stator has electrical connections on the outside of the tube; the rotor inside the tube needs no connections.
Define the heel effect and describe how it can be used advantageously. Higher x-ray intensity on cathode side, which should be positioned to thicker anatomy. X-ray tube current is limited by the cloud of electrons surrounding the cathode.
An increase in kVp will remove the space charge. Radiation emitted through the x-ray tube housing other than the primary beam. Shroud inside the x-ray tube surrounding the cathode to concentrate the electrons on the target focal spot.
X-ray tube capable of high-speed switching. Zaira Khan. Sunil Naresh. Ochefio Owunebe. Show More. Views Total views. Actions Shares. No notes for slide. X-ray Tube Cathode 1. Negative Electrode 2. Source of electron heated by an electric current 3. Mounted within a negatively charged focusing cup 4. Made from tungsten wire of 0.
This collection of negatively charged electrons forms space charge. On long term use, tungsten vaporizes and form thin coat on inner surface of glass wall of x-ray tube. This alters the electric potential of the tube, allowing tube current to stray and interact with the glass envelope; the result is arcing and tube failure 2.
If tube becomes glassy, x-ray production will fall off and tube will fail 3. A failing vacuum, resulting from leakage or degassing of the materials, causes increased ionization of the gas molecules, which slows down the electrons. They insulate high voltage parts of x-ray tube from metal envelope.
It is due to electron back scatter from anode interacting with metal other than the focal track and striking anode a second time to produce X-rays. Decreased by : 1. Placing collimator 2. Lead diaphragm as close to X-ray tube as possible. Using a metal enclosure — attracts off focus radiation to the grounded metal tube. Due to time allowed for rotor to accelerate to designed rpm; filament current increases to get correct x-ray tube current 2.
What happens when the exposure switch is first pressed? Why is there a small delay when the rad tech pushes the exposure button of the imager? Phase 1 Some of the electricity is diverted to the induction motor of the x-ray tube to bring the rotor up to speed. Filaments are usually made of thoriated tungsten.
Because tungsten provides for higher thermionic emission than other metals. The filament is embedded in a metal cup called the focusing cup. Because all the electrons accelerated from cathode to anode are electrically negative, the electron beam tends to spread out owing to electrostatic repulsion. The focusing cup is negatively charged so that it electrostatically confines the electron beam to a small area of the anode.
When the x-ray imaging system is first turned on, a low current passes through the filament to warm it and prepare it for the thermal jolt necessary for x-ray production.
At low filament current, there is no tube current because the filament does not get hot enough for thermionic emission. Once the filament current is high enough for thermionic emission, a small rise in filament current results in a large rise in tube current. Most diagnostic x-ray tube have two focal spot, one large and the other is small. The small focal spot is used when better spatial resolution is required.
The large focal spot is used when large body parts are imaged and when other techniques that produced high heat are required. Normally, either filament can be used with the lower mA station, approximately mA or less.
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