How does X-Ray dose stability relate to voltage/current stability?

When trying to understand the relationship between voltage/current stability and X-Ray dose stability, there are a couple of factor to consider. X-Ray dose is not directly proportional to the high voltage across the X-Ray tube, it is an exponential function(X²). If the High voltage across the X-Ray tube is doubled, the X-Ray dose increases by a factor of four. With regards to X-Ray tube current, it is directly proportional to X-Ray dose.