Types of x-ray tube.
The x-ray tube is a component of x-ray imaging system.It is evacuated tube which are produced x-ray by energy conversion when a fast moving stream of electrons suddenly decelerated in the target of anode. The x-ray is made of pyrex glass which contains two electrode. The elections are produced at cathode side and they strick at anode side and the x-ray are produced.
There are two types of x-ray tube.
A) Crooke’s x-ray tube or gas x-ray tube.
B) Coolidge X-ray tube.
A) Crooke’s x-ray tube :- The Crooke’s X-ray tube invented by sir William Crooke’s in 1875. It’s also called gas tube because the some amount of air are present in this tube. In beginning the gas Field x-ray tube were used to produce x-ray. The Crooke’s x-ray tube consists of two electrodes, one is cathode and other is anode. The cathode and anode are covered by a glass envelope and the both electrodes are kept in opposite site in each other.
The cathode is aluminum concave disk. The anode or target is made up of tungsten or platinum backed with copper. The target is put on 45° angle with axis of cathode neck.
In a Crooke’s or gas tube, A small amount of air is always left in this tube. During the exposure time, when a high voltage is applied between the cathode and anode, the air inside the tube gets ionized and electrons are produced. These electrons move at high speed at anode side and produce an avalanche of electrons by collision with air molecules. When the electron stream strikes the target, the the x-ray are emitted.
B) Coolidge x-ray tube:-
This new x-ray tube was designed by sir Coolidge in 1913. It was recognized as far superior to the Crooke’s tube. The Coolidge x-ray tube was vacuum tube, that allowed x-ray intensity and energy to be selected separately and great accuracy .
The Coolidge x-ray tube worked by thermionic emission principle. It was also known as hot cathode or electron tube. This was fully evacuated x-ray tube so there is no needed to production of x-ray to ionization. The filament used in tungsten. The cathode and anode are placed opposite to the cathode as like Crooke’s tube.
when the high voltage is applied between the cathode and the anode. The filament get heated and the electrons are emitted, that electrons are traveling from cathode to anode. 99% of photons energy conversion in to heat and only 1% of photons energy produced x-ray.