High voltage current measurement

@embed12 This is all nonsense.
You have asked a question without giving any information that would help us give rational answers.
40mA 40kV

is by my reckoning 1.6kW of RF matched to a 1M load.

You cant use a resistive divider to measure RF, you need to account for the capacitance and inductance also.

So its NOT AC?

This starts to make a LITTLE more sense.
@Koepel gave you the answer in this post:

if you need more help, please read

and