Effects on rating of x ray tube?

Question

What is the effect of length of exposure, profile of the voltage supply as a function of time and previous use of the tube on the rating of an x-ray tube

Answer 1

Here's a short discussion that can perhaps help the interpretation of x-ray tube specs

There are four basic limiting factors in a medical x-ray tube:

(1) the focal track -- this is right where the x-rays are created and it can reach 2400 C near max ratings. The temperature is principally affected by the focal spot size, the exposure power and duration, and the rotation speed of the anode.

(2) the anode as a whole -- this is measured by anode heat storage. This temperature typically ranges from around 100 C (zero % heat storage) to 1100 C (100% heat storage). The anode stores the energy from creating the previous x-ray exposures and transfers it to the cooling fluid via thermal radiation. This (average) temperature is principally affected by the energy (not the power) and timing of prior exposures.

(3) the tube housing -- measured by housing heat storage or temperature, and typically ranges from 25 C (cold) to around 80 C (hottest). This temperature is also affected by the prior exposures, and the cooling system in place (fans, heat exchanger, water chiller, etc)

(4) the filament current. Like the filament in a light bulb, run it hotter and the tube lifetime is reduced.

The ratings are not usually sensitive to a well-running high voltage power supply except in the case of older single-phase supplies (tube track ratings need to be derated), or if the power supply is particularly sensitive to minor tube instabilities as the max ratings are approached.  

The reference below is of a CT tube FYI