Production of X- RAY and their properties

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INTRODUCTION

X-ray is produced by an X-ray tube, the three main parts of an x-ray tube are the anode, cathode, and filament

When the filament is heated through the power supply, electrons are ejected from its surface, a high voltage between the cathode and the anode, the force of electrons accelerate towards the cathode to anode, the electrons hitting the anode tungsten target, produce bremsstrahlung radiation only 1 % X-ray produce and 99% electron energy is converted into heat.

• The x-ray beam energies pass through a thin glass window in the tube envelope, in some tube thin glass beryllium window.

1.X-ray tube envelope is generally made of Borosilicate glass (pyrex)

2. The Cathode design – The cathode in a modern x-ray tube (Invented in 1913, W.D.Coolidge ) consists of wire filament to provide current .and negatively charge (-) focusing cup.

• The function of focusing cup is to direct the electron towards the anode, so that it strikes the target in a well define area called the focal spot.
• The size of the focal spot depends on the filament size.
• The diagnostic tube usually has two separate filaments to provide a double focal name one small and large focal.
• Large focal is 2×2 mm may be used for taking high-speed radiograph where large current anode  500 MA and short exposure time required.
• Small focal 1×1 mm is used in fluoroscopy where low current 100 to 200 MA at large exposure time is required through viewing the final detail of the anatomical structure.
• The material of filament is tungsten is chosen because of its high melting point.

    3. The Anode design – Target anode is positively charge (+), made of tungsten 90%,rhenium 10% alley because of high atomic number, high melting point, high conductivity & heat capacity that can intense heat produced in the target by electron bombardment.

• Coating layer molybdenum and graphite base because of lightweight resistance to aging, greater heat store capacity, less roughing the target area, and avoiding the crest in the anode.

Properties of X-rays–

1.X- rays are high penetrating power.

2.X -rays are electrically neutral and can not be deflected by electric & magnetic field.

3.X-rays can produce fluorescence effects in certain crystals.

4.X-rays effect photographic film & produce a latent image which can be developed chemically.

5.X- rays produce biological & chemical changes.

6 .X-rays travel at the speed of light 3×10⁸m/s.

7.X-rays have ionization power.

8.X-ray, liberate minute amount of heat on passing through matter.

Important fact –

ICRP (60) 1991 recommendation for effective dose –

International commercial radiation protection (ICRP)

• Occupational  effective dose 20 mili sv/year    (msv)
• (Average cover period of 5 years should not exceed in 30msv/years.)
• Trainees – 6 msv/ year
• Public 1 msv/year
• Lens of eye – 150 msv/year
• Trainees – 50 msv/year
• Skin/hands /feet -500 msv/years
• Trainees – 150 msv/years
• Pregnant lady – 2 msv/years
•  Effective dose unite –Sv (sievert)      ( earlier REM)
• Absorbed dose unite – gray

• 1 gray=100 rad
• Energy unite- jule
• 1ci (curie)=3.7×10¹⁰ becquerel.
•  1 Becquerel =2.7×10^-11ci (curie)
• Radio Activity unite – becquerel
• 1ev -1.6×10^-19jule
• Radiation is the process by which energy transfer takes place without any  medium
• Radiation unite –c/kg
• Ionization radiation – 2.5×10^-4c/kg
• KeV- kilo energy volt
• mAs-  Milli Ampere Second
  • read more..collection all data through books and google search

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