Three types of rays emits continuously from a radium material. These rays are known as alpha rays (a rays), Beta rays (p rays) and gamma rays (x rays). Gamma rays also know as x-rays. The frequency of x-rays as approximately 1020 Hz and its wave length is approximately 10"10 meter. X-rays are electromagnetic wave which are widely used in medical field and industries for inspection of human body or any other thing.
X-rays can be produced with the help of high vacuum tube with a heater, cathode and anode. Vacuum tube is operate at very high voltage. A special electron tube (vacuum tube) is shown in Fig No 11 which is used for production of x-rays. Such a tube has a hot filament cathode an anode made a very heave metal. Electron flow from the cathode to anode as in any diode tube. However a large DC voltage is used between cathode and anode of x-rays tube. .
When heater is on and very high anode to cathode voltage is applied the electron emits from cathode and travel toward the anode with very high Velocity, as clear from fig No11, this beam of electron strike the metal anode such speed that new rays are made from the slanting surface of the anode these x-rays seem to bounce sideways ad out thought the well of the tube. As the DC voltage (anode-to-cathode of the x-rays tube) is increased, the wave length of x-rays decreases. Same tubes now operate at more than a million volts.
Block Diagram of X-Rays machine
High voltage source is responsible for providing high voltage to the H.V transformer for a decided time. The H.V transformer produces 20 KV to 200 KV at the O/P. These voltages are used to determine the contrast of the image. High voltages have higher contrast.
This rectifier rectifies the high voltage produced by the H.V.T and supplies them to the anode of the X-ray tube.
The heat of the X-ray tube (should not be increase by a specified range). If the heat is exceed from a specified value, and then the thermal over load detector is used to turn off system.
Most of the X-ray tube anodes are rotated by an induction motor, in order to limit beam power at any spot and helps to cool the anode.
Pulse duration timer
The duration of the time must be very small so that
The X-ray beam used in the medical field which contains a broad band of frequencies.(1) The unwanted frequencies in the x-ray based create side effects e.g extra dose for patient causing tumor also reduce the contrast in the image. These are called soft x-ray. To eliminate these effects Aluminum filter is used.
Another mean to reduce the dose of patient is to confine the x-ray beam only on the region of interest on the body of patient. An external collimator placed between patient and filter does this.
X-rays inside the patient create x-ray scattering, which tends to burned the image to absorb the scattered x-rays and eliminate the burning of an image a lead grid is used which is called diaphragm.
The x-rays passed from the desired region of the patient body are made to strike on the film where they produce an image of the body soft and hard parts. A lead shield is use to collect the x-rays after striking on film.
The H.V. source produces high voltage supply, which are rectified by rectifier and applied to anode of the x-ray tube. Filament supply is also provided. As a result x-rays tube producing an x-ray beam which is passed through the body and produces image of body and the film, which is examined in laboratory.
X-rays plays an important role for the inspection of diseases. X-ray machine was invented by Henry Backral of Germany. X-Rays are, no doubt used extensively in modern medicine for detection of fracture in bones, presence of Tumour, infection of lungs, kidneys and other organs of body. X-rays are also used for treatment of tumours and abnormal condition in the body.
The uses of X-Ray in industries are as follows:
Industrial radiography is the process of inspection of interior of objects by x-Rays and photographic film the atomic arrangement within the object. Thus the material object may be identified X-Rays passing through tie objects under inspection fall on the photographic film. The shadow so formed on the film gives information regarding non-uniformity, change of material etc, in the interior of the object. Fluoroscopy in similar to industrial radiography but for the difference that the X-Ray image instead of being photographed, is projected on a fluorescent screen. Fluoroscopy is widely used in industry for reading inspection of manufactured articles before final approval. Thus it is used for inspection of fruits before packing, canned foods, transmitting tubes and other assembled articles. Radiography, on the other hand, is usually employed for inspection of larger and relatively costly objects such as metal casting, welded assemblies etc.
These are extensively used in rolling mills for measuring thickness of metal. This is done by passing x-rays through the metal sheet and measuring with the help of an electrical transducer, the intensity of X-Rays on emergence from the sheet, lonization chambers and Geiger tubes may be used for this measurement.
When as X-Rays beam falls on a thin substance major portion of the beam gets, passing through the substance but at the same time a small portion gets scattered. The angular distribution of scattered energy is not uniform but depends upon the atomic arrangement of the substance in the sample.. If the objects under study are completely surrounded by a sphere of photographic film to record the diffracted rays, then this film shows lines of maximum intensity arranged according to the object may be identified.
Different techniques may be employed for obtaining x-ray diffraction patterns for objects of different types. Thus for an object in the form of a thin section, the photographic film for recording the x-ray diffraction pattern is mounted on the same side opposite from the x-ray source. In the case of object, in the form of fine powder placed in a container. In the case of solids of relatively greater thickness, the photographic film is mounted on the same side of the samples as x-rays source. In this case the film records the scattered radiation which is mostly reflected from the object under study.