Safety · X-Ray Production
X-ray emission spectrum: bremsstrahlung, characteristic peaks & technique
The x-ray emission spectrum shows which photon energies leave the tube. Most of the beam is bremsstrahlung (a continuous curve). Above ~70 kVp with a tungsten target, discrete K-characteristic peaks appear near 69 keV. This diagram shows what kVp, mAs, and filtration each change—and what they cannot.
Bremsstrahlung (the continuous spectrum)
Projectile electrons decelerate in the target and emit a range of x-ray energies. The curve’s shape and area respond to technique factors; this is the majority of a diagnostic beam.
Characteristic peaks (tungsten ~69 keV)
When kVp is high enough to eject tungsten K-shell electrons, discrete K-characteristic x-rays appear (commonly drawn near 69 keV). Only changing target material moves that line—kVp, mAs, and filtration do not shift the characteristic energy itself.
What kVp, mAs, and filtration change
kVp
Raises maximum photon energy and changes the bremsstrahlung distribution.
mAs
Scales quantity without changing the energy limit the way kVp does.
Filtration
Removes low-energy photons, hardening the beam.
Frequently asked questions
What is the difference between bremsstrahlung and characteristic radiation?
Bremsstrahlung is a continuous spectrum from electron deceleration in the target. Characteristic radiation is discrete peaks from electron shell transitions (for tungsten K-characteristic, near 69 keV once kVp is high enough).
Does increasing mAs change the maximum x-ray energy?
No. mAs changes quantity (how many photons). Maximum energy is set by kVp (and target/filtration shape the spectrum).
Why does the characteristic peak sit near 69 keV for tungsten?
It reflects tungsten K-shell transitions. Technique can make the peaks appear (enough kVp) or change their relative contribution, but it does not move that characteristic energy the way changing target material would.
Interactive diagram
Free layer covers bremsstrahlung vs characteristic and what each technique factor changes. Unlock full access to scrub kVp/mAs/filtration and linked practice.