X ray baggage scanner is widely used at the airports to detect the suspicious & un-authorised items or in other way we can say the banned objects.
X Rays baggage scanner uses x rays for detection of targets, and x rays generated are the main source as well as concern for the operation & results. The volume of x rays generated, controlled and limited has great importance in target detection as well as safety. The alphabet X was added to such rays as the scientists who first found such rays did not know what rays these are hence named them as x rays. The German physicist Wilhelm Roentgen was the first to observe such radiations.
Technically x ray is an electromagnetic wave of high energy, very short wavelength, which is able to pass through many materials from opaque to the light. X-rays are used for their penetrating power in radiography, radiology, radiotherapy, and scientific research. And it finds application in baggage scanners for the same reason.
X rays in the baggage scanners can be generated by an x ray tube. The x ray tube is the vacuum tube using a very high voltage to accelerate the electrons released by a hot cathode to a high velocity. The high velocity electronics are made to collide with the metal targets called as an anode, just generating the x rays.
X ray baggage scanner involve the specific technical terms for use. It involves direction of generation of x rays, anode voltage and current. They typical voltage for anode ranges from 100–160KV with current of 0.4-1.2mA. The safety of x ray leakage is very important & technically the rate of ray leak is limited to 0.1 µGy/h, we call it as dose rate measured as Gy/h: gray per hour. The Gray is a unit of absorbed radiation equal to the dose of one joule of energy absorbed per kilogram of matter, or 100 rad.
What types of scanners are used at airports?
There are two types of baggage scanners used in airports
- Millimetre radio waver scanners, uses millimetre radio waves
- Backscatter scanners, uses low intensity x rays
How x ray baggage scanners work?
The majority of the x ray baggage scanner use two sources. One source is at the sides while as other source is at the top. Simply we can say X axis source and Y axis source. The combination of X & Y axis helps to indentify the target from two different points. The identification of the target from two sides helps in elimination of missing the hidden contrabands. The two sources are combined with the central sensor and the information generated is transmitted to the centralised computing machine. The central computing machine analyses the information using specific algorithms hence identifies the content. These algorithms calculate the Z effective number (Zeff).
Z effective number also called as the effective nuclear charge, it is the number of protons that an electron in the element effectively ‘sees’ due to screening by inner-shell electrons. The number and mass density helps in identification of the target type.