X-ray equipment: Constant potential 5-50 KV: Fig 3.2 (2)
Published: Sep 29, 2021

If you take the y-axis value and multiply by 6, this will give you a figure of mGy/ mA h at 1m. Note how exposure rate is significantly affected by filtration.
A note on units
In SI units, R has the units of charge divided by unit mass (C/kg). C (coulomb) is the amount of electric charge transported by a current of 1 ampere during 1 second.
1 R is the amount of radiation required to liberate positive and negative charges of one electrostatic unit of charge (about 3.33564×10−10 C) in 1 cm³ of air at standard temperature and pressure (STP).
In air, 1 R = 2.58×10−4 C/kg. 100 R is 0.933Gy at STP in air (i.e. 1 Gy is a good approximation).