Aluminum foil paper does not escape X-ray. Airport security X-ray inspection equipment penetration can reach 30-34mm thick steel plate, wire resolution 40AWG, that is, the diameter of 0.08mm wire. So the tinfoil package is not shielded from X-rays, the structure of the package will be clear, in addition to the diameter of 0.08mm wire can be distinguished, such as laptops, such objects are required to be taken out separately to check.
One is because the ray may not penetrate or the image is not clear, two is because of its electronic device structure will interfere with the judgment of other items. Security screeners look at it based on density and thickness; tinfoil can't completely block X-rays from passing through, and tinfoil and steel have different densities and different thicknesses.
Technology of the security check:
1, baggage items X-ray security machine technology used: X-ray transmission imaging technology
X-ray transmission imaging technology measures the number of X-rays passing through the object being detected, the X is absorbed by the chances of reflecting the density of the material being detected information. The transmissive method of detection is carried out by staff interpretation of the shape and density information of the substance to be detected.
The X-ray imaging products now used in airports are basically dual-energy X-ray imaging technology, multi-view X-ray technology, and CT-ray imaging technology. Compared with the monoenergetic X-ray inspection system, the use of dual-energy X-rays can obtain the effective atomic number information of the inspected object, which improves the system's ability to distinguish substances.
CT technology can form a three-dimensional image of the item, determine the thickness of the substance, while being able to distinguish explosives and other low atomic number of similar substances.
2, check the trace detection of explosives technology: ion mobility technology
In the case of the higher level of security checks, the use of "rubbing paper" on the person or carry a parcel for trace detection of explosives. The principle of the technology is: in the atmosphere or migrating gas will be measured in the ionization of the sample to form ions, and then in the applied electric field drift. Due to the different samples of different mobility, the different components of the sample in the migration tube to separate, generally heavier molecules than the light molecules go slower.
In this way, the composition of the sample can be known from the measured migration time. Ion mobility spectrometry is now widely used in the fields of drug detection, explosives detection, chemical warfare agent detection, atmosphere, water organic pollution detection, factory toxic gas monitoring, food detection, wood species detection.
3, the current airport use of human imaging technology: backscatter imaging technology
Backscatter technology is a class of Compton backscattering based on the detected substances to analyze the method. The principle of this method is to measure the Compton scattering X-rays scattered from the detected material to image the object in two or three dimensions. It gives information about the distribution of the electron density inside the detected substance. The backscattering technique is suitable for detecting low Z organic materials.
4, currently used in airports, human imaging technology: millimeter wave imaging technology
Millimeter wave is generally defined as the frequency from 30GHz to 300GHz band, which is between infrared and microwave in the spectrum. This spectrum
Compared with visible and infrared light, millimeter waves have some penetration into most non-metallic objects, and at the same time have a resolution that microwaves do not have.
There are two main types of millimeter-wave imaging modalities: passive and active. Passive imaging equipment is the use of human radiation millimeter wave
gathering imaging device. Since the amount of millimeter-wave rays radiated by objects depends on their physical properties and temperature. The human body radiates more millimeter waves than metals, ceramics, plastic explosives, powdered explosives and clothing, insulation materials.
And millimeter waves can penetrate any insulating material, all clothing fabrics and most building materials. Most of the millimeter-wave imaging equipment used in the market today is active, which is more accurate than passive.
In front of the millimeter wave imaging equipment, the clothes on the person is gone, in the human body contours of the reflection, the person on the coins, buttons, pens, keys and other things clearly visible. If hiding pistols, bombs, drugs and other prohibited substances, is more visible.
5, used to check the suspected hazardous liquids, explosive solid powder, drug technology: laser Raman technology
Laser Raman technology is based on the use of lasers as a source of Raman scattering and the establishment of analytical methods. When a molecule of a substance is irradiated by optical radiation,
the irradiated light is absorbed and re-scattered due to the vibration of the molecule or the jump of the rotational energy level.
The wavelength of Raman scattering is related to the structure of the material, which can be used as the basis for qualitative analysis, and the intensity of Raman scattering can be used as the basis for quantitative analysis. Laser Raman technology in security, environmental protection, food, medicine and other fields have a wide range of applications
.
6, used to check the suspicious liquid technology: dielectric constant measurement technology (microwave detection)
Relative dielectric constant represents the degree of polarization of the medium under the action of the external electric field of physical quantities, and the material molecular polarity. Molecular polarity refers to the unevenness of charge distribution within the molecule. According to the liquid article dielectric constant characteristics, can be to some extent the lower dielectric constant flammable class of hazardous liquids and other liquid articles to distinguish.
7, used to check the person carrying metal technology: metal detection technology
Common products are metal security gates and handheld metal detectors. Security gate can pass through the metal object alarm, is due to the two sides of the door plate is equipped with sensors that can emit and receive alternating electromagnetic fields. Metal conductive body by the alternating electromagnetic field excitation, in the metal conductive body to produce eddy current, and the current and the original magnetic field emitted a magnetic field of the same frequency but in the opposite direction.
Metal detector is through the detection of the eddy current signal to find the presence of metal objects nearby. By the transmitter emitted by the excitation of electromagnetic waves, by the receiving sensor to receive the signal of the metal object, the receiving sensor to detect the eddy current signal detected, and then through a series of circuit amplification, when the signal reaches the set value that is, in the form of acoustic and visual alarms.