Are there different sizes and/or different types of x-ray sources?
X-ray sources are rated by power and by focal spot size. The power is the product of the beam current and the cathode to anode voltage. It determines the maximum x-ray energy (kVp) and the maximum x-ray flux (i.e. dose rate) you can obtain from the tube. The focal spot is the region of the anode that emits the x-rays. The spot size depends on the target material and the power dissipated by the tube. In general, higher tube power requires a larger spot size. Sources have power ratings ranging from a few watts to many kilowatts. No hard fast definition exists, but a few rules of thumb are used to loosely describe ranges of source types. Tubes with spot sizes larger than 1 x 1 mm are referred to as conventional x-ray sources. Tubes with 0.5 x 0.5 mm down to 50 micron diameter are referred to as fine-focus tubes. Sources with spot sizes of 50 micron diameter or less are called micro-focus tubes. Tubes with spot sizes smaller than 1 micron are beginning to appear and they are called nano-fo
