X-ray Production. kVp KINETIC ENERGY OF ELECTRONS. CATHODE --------. MADE OF TUNGSTEN + 1%-3% THORIUM. TUNGSTEN. Z # 74 MELTING POINT- 3,410 DEG. CELSIUS. THORIUM. Z # 90. THERMIONIC EMISSION. CATHODE HEATED UP TO AT LEAST 2,200 DEG. CELSIUS. ANODE +++++. TUNGSTEN
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kVp KINETIC ENERGY OF ELECTRONS
MADE OF TUNGSTEN+ 1%-3% THORIUM
Z # 74
MELTING POINT- 3,410 DEG. CELSIUS
Z # 90
CATHODE HEATED UP TO AT LEAST 2,200 DEG. CELSIUS
HIGH Z# - 74------EFFICIENCY OF X-RAY PRODUCTION
HIGH MELTING POINT –3,410 ° C– TARGET HEATED TO 2,000° C
If an incoming free electron gets close to the nucleus of a target atom, the strong electric field of the nucleus will attract the electron, thus changing direction and speed of the electron. The Electron looses energy which will be emitted as an X-ray photon. The energy of this photon will depend on the degree of interaction between nucleus and electron, i.e. the passing distance. Several subsequent interactions between one and the same electron and different nuclei are possible. X-rays originating from this process are called bremsstrahlung. Bemsstrahlung is a German word directly describing the process: "Strahlung" means "radiation", and "Bremse" means "brake
90% OF X-RAYS ARE PRODUCED THROUGH BREMS
INTERACTIONS WHEN 80-100 KVP APPLIED
The high energy electron can also cause an electron close to the nucleus in a metal atom to be knocked out from its place. This vacancy is filled by an electron further out from the nucleus. The well defined difference in binding energy, characteristic of the material, is emitted as a monoenergetic photon. When detected this X-ray photon gives rise to a characteristic X-ray line in the energy spectrum.
KE OF PROJECTILE ELECTRON > BINDING ENERGYORBITAL ELECTRON
OF DIFFERENT SHELL ELECTRONS
70-12 = 58 keV
70-3 = 67 keV
12-3 = 9 keV
HEAT PRODUCTION !
THERE ARE MANY
PRODUCED IN ONE ATOM
IS ALSO POLYENERGETIC !
99.4% HEAT 0.6% X-RAYS
% EFFICIENCY= K * Z * kVp
K = 1 * 10-4