1. Production of x-ray
DR / OMAR HASHIM

2. X-ray discover by Roentgen in 1895 while studding cathode rays
X –ray tube ;-
The tube consist of galas envelope that has been evacuated to high vacu
-cathode ;- -ve electrode
-anode ;- + ve electrode both of same in the tube .
The cathode is a tungsten filament that when heated emits electrons .
(thermionic emission ) . The anode consists of a thick copper rod at the
Which is placed a small piece of tungesten target .
When a high voltage is applied between the anode & cathode , electron
Emitted from the filament are accelerated toward the anode and achieve
High velocities before striking the target . The x-ray are produced by the
Sudden deflection or acceleration of the electron caused by the attractive
Force of the tungsten
The anode;- the choice of tungsten as target due to ;-
• the target must have high atomic number Z =74
• high melting point 3,370

3. the remove of the heat from the target is an important for the anode
And this achieved by ;-
1) in some tubes by conduction of heat through a thick copper anode
Out side where cooled by oil , water or air
2)rotating anode have also used in the diagnosis x-ray .
3)the function of the oil bath surrounding an x-ray tube is to insulate
The tube housing from high voltage applied to the tube as well as
Absorb heat from the anode .
Some stationary anode are hooded by a copper and tungsten shield
To prevent stray electrons from striking & non target component .
Stray electron are 2ry electron produced from target when it is being
Bombarded by the 1ry beam .
The copper of the hood absorb electron where as tungsten absorb
The x-ray produced in the copper

4. Focal spot ;- is area in the target with optimum size . Is the area from which
X ray are emitted . Should be as small as possible for producing sharp images
In the therapy tube relatively larger focal spot are acceptable .
The apparent size of the focal spot = sin 0 + A .
In the diagnosis radiology the target angles are quite small ( 6—17 ) to produce
Apparent focal spot size ( 0.1 x 0.1 m m ) to 2 x2 mm .
In most therapy tube however the target angle is large ( 30 degree ) & apparen
Focal spot 5 x5 ---- 7 x 7 m m .
Heel effect ;- is the variation across x-ray beam , due to variation in the x-ray
Coming from different depth . This problem can be minimized by using acom-
Pensating filter .
The cathode ;- consists of a wire filament . Circuit ,& negatively charge focusing
Cup . The function of the cathode cup is to direct the electrons toward the anod
So as to strike in a will defined area ( focal spot ) . The material of the filament
Is the tungsten ( high matlingpoint )
Basic x ray circuit ;-
in simplified diagram the circuit is consist of two parts 1) high voltage
Circuit to provide the accelerating potential for the electron 2 ) low voltag
Circuit to supply heating current to the filament .
The filament supply for electron emission usually consists of 10 v at 6 a
Can be cheeve by using step down transformer .
High voltage to the x ray tube is supplied by the step up transformer

5. Voltage rectification ;-
The disadvantage of the self rectified circuit is that ;-
1) No x ray are generated during the inverse voltage cycle , where ( where
The anode is negative - ve relative to the cathode So the out put of
The machine is low
2)When the target gets hot and emits electrons by the process of thermion
Emission . During the inverse voltage cycle , these electron will flow from th
Anode to the cathode .
The problem of tube coduction during inverse voltage can be solved by us
Voltage rectifiers , which prevent the tube from conducting during the invers
voltage cycle is called half wave rectification placed in high voltage part
of the circuit .
High voltage rectifiers are either valve or sold .
The valve rectifier is similar principle to the x ray , has cathode & anode
Sold rectifier these rectifiers consist of conductors coated by selenium ,
Silicon &germanium . They conduct electron in one direction only .

6. Full wave rectification ;- this is achieved by arranging 4 rectifiers in the high v
part of the circuit , so that the cathode remain -ve & anode +ve during both
Half so x ray produce during both half .

7. PHYSICS OF X RAY PRODUCTION ;-
There are two different mechanism by which x-ray are produced one give
Rise to bremsstrahlung x ray & other characteristic x ray
A) Bremsstrahlung ;-
AL so called braking radiation . Is the result of radiative interaction between
A high speed electron and nucleus . The electron while passing near
May be deflected from it is path by the action of coulomb forces of
Attraction & loss energy as bremsstrahlung [Max well general theory ] Energ
Propagated through space By electromagnetic field , which is part of it o
Of it is dissociated from it & propagates as electromagnetic radiation .
Since electron may have one or more bremsstrahlung interaction .
The direction of emission of bremsstrahlung photon depends on the energy
Of the incident electron ,
Below 100kev x ray are emitted more or less in all direction equally.
As the kinetic energy of the electrons increase , the direction of x-ray emiss
Becomes forward .
Transmission – type targets are used in megavoltage x-ray tube in which th
Electron bombard the target from one side & the x ray beam is obtained o
The other side .

8. Low voltage x ray tube , it is technically advantageous to obtain the x ray beam
On the same side of the target [at 90 degree with respect to the electron beam
Direction ] .
The probability of bremsstrahlung production varies with the Z or the target
material. -10
X ray efficiency = 9 x 10 zv .
V = Tube voltage .
Characteristic x ray ;-
The mechanism of their production ;- an electron with kinetic energy E0 may
Interact with the atoms of the target by ejection an orbital electron, such as a K,
L OR M electron , leaving the atom ionized .
The original electron will recede with energy = E0 –A E , where AE is the energy
Given to the orbital electron . Apart of the AE energy is spent in overcoming
The binding energy of the electron & the rest is carried by ejected electron .
When a vacancy is created in an orbit, an outer orbital electron will fall down to
Fill that vacancy . In so doing , the energy is radiated in the form of electromagn
Radiation , which called characteristic radiation ( characteristic of the atoms of the
Target ) . It is un like bremsstrahlung , characteristic radiation or x ray are emitted a
Discrete energies

9. Cyclotron ;- deuterons