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Nauki ścisłe priorytetem społeczeostwa opartego na wiedzy
Artykuły na platformę CMS
Slawomir Wronka
Application of methods of nuclear physics and high physics of high energy in the
protection of borders
Introduction
This paper familiarizes students with the practical application of research methods and
devices developed for physics experiments. In the field of high energy physics there are mainly
particle accelerators and detectors of radiation. One of the actively developing application is to
protect the borders, in particular the detection of smuggling illegal goods and hazardous materials.
The contents of this article can support interest in science, particularly physics.
Preface
Modern nuclear physics and high energy physics relie heavily on experiments carried out with
the use of particle accelerators.
The world's largest complex of accelerators at CERN (European Organization for Nuclear Research,
Geneva, Figure 1) uses accelerated proton beams for experiments in the field of high energy. The
LHC accelerator (Large Hadron Collider), thanks to which Higgs particle was discovered [1], is
planning to obtain energy of 7 TeV.
Projekt współfinansowany przez Unię Europejską
w ramach Europejskiego Funduszu Społecznego
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Figure 1. Diagram of CERN's accelerator complex [2].
The accelerated particle beams are collided in the opposite directions or hit into a stationary
target with carefully selected materials. As a result of collisions of high-energy beams (protons, but
also of other ions, electrons or positrons) a very short-lived particles whose behavior or interaction
mechanisms allow us to verify and expand our knowledge of the universe are produced. In terms of
the structure of matter, this knowledge is described by the so-called standard model [3]. It describes
known today the basic components of matter: quarks and leptons. For example, commonly known
elements forming nuclei: protons and neutrons are made of three quarks, but the electron is the
lightest of the three leptons.
For acceleration of devices called accelerators are used. Usually these are linear accelerators in
which the acceleration takes place in a straight line and synchrotrons, in which the particles are
accelerated in a circle of constant radius. In practical applications rather cyclotron (circular
accelerators of particles spiral track) are commonly used. Charged particles are accelerated by the
electric field. Modern technology of accelerating fields of high-frequency allows to obtain intensity
field of tens of MV / m using the electrical component of the electromagnetic field.
Magnetic fields are used for curving beams, keeping on track and their focusing
If you are interested in the subject you can read more in [4].
The results of collisions are recorded by electronic detectors.
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Historically used films or emulsions recording tracks / paths of particles are replaced by advanced
computer-controlled equipment. Thanks to the detectors flight paths of the particles, the designation
of the place of their origin, momentum and energy can be reconstructed. The example of ATLAS
detector which observed Higgs particle is shown in Figure 2
Figure 2. The design of the ATLAS detector. Adapted from [5].
Technologies developed for experimental physics are used in practical applications. One of them is
to protect the borders. This article introduces the reader to the issue of the application of radiation
sources and detectors in this field.
X-rays and radiographic examinations
The discovery of X-rays by William Conrad Roentgen in 1895 enabled the development of many
important scientific areas, research techniques and applications.
X-ray beam is essentially a continuous spectrum of photons capable of penetrating even the
materials of considerable thickness (depending on the density and atomic number Z).
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One of the applications of X-ray is the observation of ‘shadow’, which creates an object in the beam
of X-rays. In medicine we call it ‘X-ray examination’ or X-ray. The non-medical applications often
use the term ‘radiography’.
The typical medical X-ray (part of the spine) is shown in Figure 3. In
properly selected energy there is a significant difference in weakening /
absorption of X-rays by bone and soft tissue, which is the physical basis
for obtaining good image quality with the right contrast.
Figure 1. Classical medical picture RTG.
Radiography is used as a method of screening cargo, baggage and people, developed primarily for
border guard and customs services. Radiography allows assessment of the type, quantity and value
of goods transported in order to verify the customs declarations. Another important objective is to
detect the smuggling of illegal items, including weapons, explosives, drugs, or strategic materials
(including nuclear).
Probably the first known example of the application in the history of radiation in cargo inspection
was to verify the content of cotton reels sent to Germany during World War I [6].
Research cars and containers
In order to illustrate large objects, such as sea containers or trucks a high penetration of
radiation is required. That is why it is used a higher energy than the standard range of X-ray tubes,
usually in the range from 4 MeV to 9 MeV. Beam of photons of these energies are produced in
electron accelerators. The accelerated electrons strike the metal plate (called disc conversion), in
which the production of photons happens. This is called breaking radiation effect [7]. You can also
find simpler systems that use radioactive isotopes [8], such as Co-60.
Container or truck move between the radiation source and detector. Fan-shaped beam of
photons ‘x-rays’ controlled load, and the vertical line of sensors reads the signals and converts them
into the resulting image on the computer. This image is formed as a composite of the following
vertical x-ray ‘strips’ into one picture.
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Figure 4. View of the device to control the truck. Adapted from [9]
The examples of the device (scanner) to control the truck shown in Figure 4, and the result of such
X-ray is shown in Figure 5
Figure 2. The result of the X-ray inspection of the truck. Adapted from [Błąd! Nie zdefiniowano zakładki.].
This image is essentially monochromatic, the color can be chosen according to the operator
(depending on the available features of software visualization).
Weakening / scattering of radiation by the material depends on the energy of radiation and the
atomic number Z. It appears that the use of two energy for radiographic examination can provide
new information. In addition to standard visualization of the inside of the car or container it is also
made the calculation of the ratio of radiation dose measured at each point of the image of the X-ray
beam with less energy and a beam of photons with more energy. The dose ratio depends on the
atomic number of the overexposed substance. This information is presented in an image using color,
which greatly improves image quality and helps to identify overexposed charges. An example of
such an X-ray result is shown in Figure 6.
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Figure 6. The result from the use of two x-ray energy. The color helps to identify the carried goods. Adapted from [10].
If the image is created by using the signals from the detectors located on the other side of the
controlled load - we use the broadcasting’ method (see Figure 7). It is possible, however, the
location of the detectors on the same side as the radiation source (see Figure 8). The observation of
‘reflected’ radiation can provide other information, also valuable in this application. ‘Reflected’
radiation arises from the so-called Compton’s backscattering [11], i.e. photon scattering with the
angle of ~ 180 degrees (so called backscattering). Exemplary results using the back-scattering
method are shown in Figure 9.
detektor
Obi
kt badany
Wiązka
promieniowan
aX
akcelerator
Figure 7. Schematically presented the rule of the transmission method of load control.
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Obiekt badany
Wiązki promieniowania X
rozproszone wstecznie
detektor
Wiązka padająca
promieniowania X
detektor
akcelerator
Fig.
presented
control
method
with the
usage
the backscatter
incident phonos
Fig. 8.
8.Schematically
Schematically
presented
control
method
with
theof
usage
of the backscatter
incident
photons
Figure 9. Detection of illegal attempts to carry packs of cigarettes hidden in a car tire on a trailer. Taken
from [9].
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Summation
Technologies developed for the experimental nuclear physics and high energy physics,
especially in the field of accelerators and detectors of radiation are used to visualize the large size –
trucks, shipping containers and carried freight through the border. As a source of radiation linear
electron accelerators are commonly used, and a set of detectors located - in the case of transmission
methods - in a vertical line on the opposite side of the controlled object it provides the following
‘lines’ of the resulting image. The ‘reflection’ or backscatter method uses the phenomenon of
backscattering radiation in the test object. In this case, the image is created in the detectors located
on the same side of the test object as the radiation source.
The methods described in this article are an example of the practical application of high technology,
which, thanks to the cooperation of physicists, engineers, mechanics and electronics, and software
developers significantly increases the level of border controls when it comes to the safety but also
economy (customs revenues to the state budget).
Bibliography
[1] Leon Lederman, Dick Teresi: Devine particle: if the universe is the answer, what's the
question?, ISBN 83-86868-10-4. , ISBN 83-86868-10-4.
[2] http://en-dep.web.cern.ch/en-dep/Groups/MEF/Sections/INJ/, taken 17.04.2013
[3] http://www.ncbj.gov.pl/node/1697, http://efizyka.win.pl/przygoda/frameless/standard_model.html,
odnośniki z 17.04.2013r.
[4] Waldemar Scharf, Biomedical accelerators, Warszawa : Editor PWN, 1994, ISBN
9788301113087.
[5] http://www.physik.unizh.ch/lectures/MC2009/cd/exercises/keyhole/pl/accelerators/LHC.htm,
taken 17.04.2013r.
[6] Edwin J. Clapp: Economic Aspects of the War, by Yale University Press, First printed August,
1915, page 141.
[7] Jerzy Massalski: Detection of nuclear. Warszawa: Państwowe Wydawnictwo Naukowe, 1959.
[8] http://www.mbtelecom.ro/Products, taken from 17.04.2013r.
[9] Customs News, nr 2/2011, available In the Finance Ministry: www.mf.gov.pl, 17.04.2013r.
[10] Ogorodnikov, S.; Petrunin, V. (2002). "Processing of interlaced images in 4-10 MeV dual energy
customs system for material recognition" Physical Review Special Topics – Accelerators and
Beams 5, 104701, 2002
[11] Np. tu: http://www.if.pw.edu.pl/~pluta/pl/dyd/mfj/wyklad/w2/segment3/main.htm

Wersja angielska artykułu w formacie pdf

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