Detection Of X-RAYS

Photographic techniques, while much improved upon since the time of Röntgen and still extremely useful for qualitative applications, are not well-suited for more quantitative measurements of X-ray intensities and spectral content. A number of more effective detection methods have been developed.

In a Geiger-Müller tube or Geiger counter, incoming X-ray photons ionize atoms in a gas-filled volume. An applied high voltage induces further ionizations from collisions between liberated electrons and neutral atoms, creating an avalanche of charged particles and a large electrical pulse that is easily detected.

More sophisticated detection schemes based on the ionization of gas atoms can discriminate between X-rays of different energies (see radiation measurement: Proportional counters). Other common detection schemes rely on the ability of X-rays to produce visible fluorescence in crystals (see scintillation counter) and charge separation in semiconductors (radiation measurement: Semiconductor detectors).