# X-ray production and ionization energy

Homework Statement:
what's the minimum kvp and kep required to generate x-ray?
Relevant Equations:
nothing
I am confused with the Kvp and Kep.
I know that In the x-ray tube, after heating the filament and the electron cloud if formed, then the step-up transformer is going to increase the voltage and reduce the current to produce a high potential difference to that electrons will accelerate from the cathode to the anode. now, here comes the issue. the one that will determine the highest voltage is the Kvp (Kvp= kilovolt peak) with the help of the autotransformer. in our x-ray machine, the kvp is fixed and that is 65 kv. but isn't this not enough to cause ionization of the anode (tungsten). I searched about the k-shell (innermost) electron binding energy for the tungsten and it was 69.4. and I learned that for causing ionization of the innermost electron, the energy of the electron that will hit the tungsten should be either =or> than the electron binding energy. so, the hitting electrons should obtain either 69.4 or above kv. how come our x-ray machine works with kvp=65 kv.
I have a doubt that the kvp is not representative for the energy. if this is the case, then what is the unit or the concept that refers to the energy of the accelerating electrons? is it the kep?