Exposure Rate from X-ray Equipment

The following resource provide the output of various x-ray tubes at a given potential - measured in R/mA at a fixed distance from the target. We have included conversion factors to SI units where appropriate. Use with caution! Wherever possible you should use the data that comes with a specific x-ray tube, or even better have the output dose rate measured. Use this resource for historical interest or as a sanity check / comparison for other data you may have.

  • X-ray equipment: Pulsating potential 5-50 KV: Fig 3.2 (1)
  • X-ray equipment: Constant potential 5-50 KV: Fig 3.2 (2)
  • X-ray equipment: Constant potential 50-200 KV: Fig 3.2 (3)
  • X-ray equipment: Constant potential 200-500 KV: Fig 3.2 (4)
  • X-ray equipment Constant potential 0.5-3 MV Fig 3.2 (5)
  • X-ray equipment Constant potential 2-30 MV Fig 3.2 (6)

X-ray equipment: Pulsating potential 5-50 KV: Fig 3.2 (1)

X-ray equipment: Pulsating potential 5-50 KV: Fig 3.2 (1)
X-ray equipment: Pulsating potential 5-50 KV: Fig 3.2 (1)

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 3.33564×1010 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).

X-ray equipment: Constant potential 5-50 KV: Fig 3.2 (2)

X-ray equipment: Constant potential 5-50 KV: Fig 3.2 (2)
X-ray equipment: Constant potential 5-50 KV: Fig 3.2 (2)

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 3.33564×1010 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).

X-ray equipment: Constant potential 50-200 KV: Fig 3.2 (3)

X-ray equipment: Constant potential 50-200 KV: Fig 3.2 (3)
X-ray equipment: Constant potential 50-200 KV: Fig 3.2 (3)

If you take the y-axis value and multiply by 600, this will give you a figure of mGy/ mA h at 1m. Note how exposure rate is significantly affected by filtration.

The handbook suggests that for half wave generators, the output is about 1/3 to 1/2 of that plotted.

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. 1Gy is a good approximation).

X-ray equipment: Constant potential 200-500 KV: Fig 3.2 (4)

X-ray equipment: Constant potential 200-500 KV: Fig 3.2 (4)
X-ray equipment: Constant potential 200-500 KV: Fig 3.2 (4)

If you take the y-axis value and multiply by 600, this will give you a figure of mGy/ mA h at 1m. Note how exposure rate is significantly affected by filtration.

The handbook suggests that for half wave generators, the output is about 1/3 to 1/2 of that plotted.

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. 1Gy is a good approximation).

X-ray equipment Constant potential 0.5-3 MV Fig 3.2 (5)

X-ray equipment Constant potential 0.5-3 MV Fig 3.2 (5)
X-ray equipment Constant potential 0.5-3 MV Fig 3.2 (5)

If you take the y-axis value and multiply by 600, this will give you a figure of mGy/ mA h at 1m. Note how exposure rate is significantly affected by filtration.

The handbook suggests that for half wave generators, the output is about 1/3 to 1/2 of that plotted.

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. 1Gy is a good approximation).

X-ray equipment Constant potential 2-30 MV Fig 3.2 (6)

X-ray equipment Constant potential 2-30 MV Fig 3.2 (6)
X-ray equipment Constant potential 2-30 MV Fig 3.2 (6)

If you take the y-axis value and multiply by 600, this will give you a figure of mGy/ mA h at 1m. Note how exposure rate is significantly affected by filtration.

1 esu = 3.3 x 10-10 coulombs = 2 x 109 ion pairs/cm3 of air. Equivalent to 2.58 x 10-4C/kg air (0.0087 J/kg of air). 1R is approximately 10 mGy (good enough for radiation protection purposes).