A heart of Hong

What is anode heel effect?

The anode heel effect in radiography is a well-described physical phenomenon,1,2 whereby radiation intensity varies along the anodeecathode axis of the X-ray tube, decreasing towards the anode. Photons emitted towards the tube's anode side are attenu- ated more than those emitted towards the cathode.

What is K alpha and K beta?

When an electron vacancy in the K shell is filled by an electron from the L shell, the characteristic energy/wavelength of the emitted photon is called the K-alpha (Kα) spectral line, and when the K shell vacancy is filled by an electron from the M shell, the characteristic energy/wavelength of the emitted photon is ...

Why tungsten is used as anode material?

The high atomic number of tungsten gives more efficient bremsstrahlung production compared to lower atomic number Target Materials. An alloy containing tungsten and rhenium is also used because the addition of 5-10% rhenium prevents grazing of the anode surface.

Which metal is generally used as a target anode to study protein crystallography?

Copper anode targets have been the most popular among PX labs due to its strong intensity at Kα wavelength of 1.5418 Å, matching the diffraction limits of about 2-3 Å for many protein crystals.

What is the target material for mammograms?

Molybdenum is also often used as the target material for anodes used in mammography because it has an intermediate atomic number (Z=42) and the produced characteristic x-rays are of energies suited for this purpose.

What tubes have special molybdenum targets?

Most mammography X-ray tubes have molybdenum-surface anodes. This material has an intermediate atomic number (Z=42) producing characteristic X-ray photons with energies well suited for this particular application. Molybdenum is chosen as a target material for its optimal spectrum.

Why is molybdenum used for anode stem?

Molybdenum has a higher specific heat than tungsten (table 2.4) and the heat capacity for an anode of this type would typically be 250000 J. The anode disc is mounted on a thin molybdenum stem. This reduces heat flow backwards and prevents the rotor bearings, which are made from copper, from overheating.

Why rhodium is used in mammography?

Tungsten also has a low vapour pressure at high temperatures, so it won't evaporate too quickly, and it is relatively cheap.

Why is tungsten used as cathode?

High thermal conductivity, relatively good machinability, reasonable price, high purity, good corrosion resistance. Functionally, this material is suitable for most samples. Therefore, in the aggregate of properties, copper is the best material for the anode of X-ray tubes.

Why is copper used in xrays?

Tungsten is used in electric bulb because it has high melting point and it does not oxidize. Thus tungsten filament does not melt even when a large amount of heat is produced due to passage of current through the filament (via heating effect of current).