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PHYSICS AND MATHEMATICS
Турабеков Ш.Ш.
Магистрант Самаркандского государственного университета
Сафаров А/F/
Доктор PhD, Самаркандского государственного университета
(Научный руководитель) DOI: 10.24412/2520-6990-2021-31118-21-24 ОСОБЕННОСТИ КВАНТОВЫХ ГАММА-СПЕКТРОМЕТРОВ И ОШИБКИ ПРИ РАБОТЕ
ДЕТЕКТОРОВ
Turabekov Sh.Sh.
Master student of Samarkand State University
Safarov A.A. PhD, Samarkand State University (Supervisor)
FEATURES OF QUANTUM GAMMA SPECTROMETERS AND ERRORS IN THE OPERATION OF
DETECTORS
Аннотация:
Для спектрометрии у-квантов малых энергий (десятки - сотни кэВ) также используются кристаллографический гамма-спектрометр, измеряющий длину волны у-квантов, и газовые пропорциональные счетчики. Для спектрометрии высокоэнергетических у-квантов используется гамма-спектрометр, основанный на регистрации черенковского излучения электронно-фотонных ливней, создаваемых у-квантами, например, в излучателях из тяжелого прозрачного вещества. свинцовое стекло. Энергия высокоэнергетического у-кванта также может быть определена в пузырьковой камере путем измерения траектории образованной им электрон-позитронной пары в магнитном поле.
Abstract:
For spectrometry of low-energy y-quanta (tens - hundreds of keV), one also uses crystal-diffraction gamma-spectrometer, which measure the wavelength of y-quantum, and gas proportional counters. For spectrometry of high-energy y-quanta, a gamma-spectrometer is used, based on the registration of Cherenkov radiation from electron-photon showers created by y-quanta in radiators made of a heavy transparent substance, for example. lead glass. The energy of a high-energy y-quantum can also be determined in a bubble chamber by measuring the trajectory of the electron-positron pair produced by it in a magnetic field.
Ключевые слова: сцинтилляционное разрешение, излучение, энергия химической связи. Keywords: scintillation resolution, radiation, chemical bond energy.
The most common types of gamma spectrometer are scintillation and semiconductor. Scintillation. The gamma spectrometer consists of a scintillator and a photomultiplier tube (PMT). In the scintillator, under the action of electrons created by y-quanta, a short-term flash of light occurs - scintillation, which is converted into an electric pulse by a photomultiplier. The pulse amplitude is proportional to the energy of the y-quantum. As scintillators, for example, solid inorganic crystals of NaJ activated by Tl are used. Scintillation resolution. Typically, gamma radiation is associated with the alpha or beta decays of isotopes in the sample that precede it. Beta and even more so alpha particles are usually absorbed before reaching the sensitive areas of the detectors. In detectors, the energies and intensities of gamma quanta are not determined directly, but with the help of secondary charged particles (electrons and positrons), which arise as a result of the interaction of the detected gamma quanta with the substance of the detector. When a gamma ray hits the detector, charged particles are produced by three processes: the photoelectric effect, the Compton effect, and the formation of electron-positron pairs.
Ee Ey Eb Er where Ey is the energy of a gamma quantum, Eb is the binding energy of an electron, and Er is the energy of the recoil nucleus, which can be neglected. The photoelectric effect is accompanied by characteristic X-rays or emission of Auger electrons. The characteristic X-ray radiation, in turn, causes the photoelectric effect. The electrons formed as a result of all these processes arise almost simultaneously, they are most often absorbed in the detector and the signals from them are summed up. Thus, almost all the energy of a gamma quantum is transferred to electrons.
EY
In the detector response function, the photoeffect corresponds to a peak - a photopeak.
As a result of Compton scattering, only part of the
energy is transferred to electrons.
Ee Ey - Ey
where Ey and Ey' are the energies of gamma quanta before and after scattering, Ee is the energy of a
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photoelectron, mc2 is the rest energy of an electron, 0 is the scattering angle of a gamma quantum. The maximum energy that, as a result of Compton scattering, can be transferred to an electron (at 0 = 180o).
In large-volume detectors, part of the scattered gamma quanta can experience one or more inelastic interactions, as a result of which all the energy of the primary gamma quantum that has entered the detector will be completely absorbed. Therefore, the photopeak is usually referred to as the total absorption peak. Figure 1 shows the experimental spectrum of 137Cs and its theoretical "idealization". The smearing of the total absorption peak and the edge of the Compton distribution is related to the energy resolution of the system.
In fig. 1
The backscatter peak is associated with Compton scattering from materials surrounding the detector at an angle close to 180 which then enter the detector and cause the photoelectric effect. Their energy is respectively equal to
In fig. 2 shows the energy dependences of the cross sections for the photoelectric effect, the Compton
effect, and pair production for germanium and silicon.
.Si
Gc/
Si/
JJJ.
A; ii1'._i_Ll
[f]OTOHOI3 (KDB)
If
Rice. 2. Dependences of the cross sections of inelastic interactions ofgamma quanta on energy for germanium
and silicon.
The shape of the measured spectrum depends on the ratio of these cross sections. Thus, at an energy of 100 keV, the cross section for the photoelectric effect in Ge is ~ 55 barn / atom, and the cross section for the Compton effect is
~ 18 barn / atom. The cross-sectional values are approximately 3: 1. Figure 3 shows the spectrum at a gamma ray energy of 100 keV. With increasing energy, the shape of the spectrum changes.
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Rice. 3. Spectrum on the HPGe detector at an energy of 100 keV. The total number of counts in the peak of
complete absorption - 3000.
Rice. 4. Spectrum on the HPGe detector at an energy of 1 MeV. The total number of counts at the peak of total absorption is 1000, in the Compton distribution - 90,000.
Thus, at an energy of 1 MeV, the ratio of the Compton cross section to the cross section of the photoelectric effect is ~ 90. In fig. 4 shows the spectrum at a gamma-ray energy of 1 MeV.
The formation of electron-positron pairs becomes possible when the energy of gamma quanta is large 2mc2 = 1022 keV. In this case, all the energy of the gamma quantum is transferred to the electron and positron. If both the electron and the positron are absorbed in the substance of the detector, then the total momentum will be proportional to the energy of the gamma
quantum and the event will be recorded at the peak of total absorption.
However, the positron can annihilate. In this case, two gamma quanta are formed, each with an energy of 511 keV. If one of these annihilation gamma quanta, without interacting, leaves the detector, then the total energy absorbed in the detector will be
Ey - 511 keV. Such events will contribute to the so-called single-flight peak (see Fig. 5). If both annihilation gamma quanta are emitted from the detector, then this event will be faxed at the peak of the double emission (Ey - 1022 keV).
Energy [KeV|
Rice. 6. Spectra of 60Co measured by three germanium detectors of different sizes. DE - double relegation peak, SE - single relegation peak. The spectrum measured with a large-volume detector also shows peaks arising from processes in the protection of the detector - characteristic X-ray and annihilation photons.
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Rice. 7. Comparison of the K-line spectra of silver from a 109Cd source, measured with a Nal (Tl) detector, a proportional counter filled with Xe and Si (Li) detectors.
When a gamma ray hits the detector, charged particles are produced by three processes: the photoelectric effect, the Compton effect, and the formation of electron-positron pairs.
References:
1. Введение в физику ядра и частиц / И.М.Капитонов // М.: УРСС. - 2004. - 383 с.
2. Zolotov, V.P., 2003. Atmospheric fallouts of 7
Be and weather phenomena. In: Proceedings of the Fifth International Conference ' 'Modern Problems of Nuclear Physics'', Samarkand, pp. 302e303.
3. Широков, Ю.М. Ядерная физика / Ю.М. Широков, Н.П. Юдин // М.: Наука. - 1980. - 783 с.
4. https://www.proquest.com/openview/8e1ee08 fb06280b14b6d1e25808f5e67/1?pq-origsite=gscholar&cbl=54011
УДК: 530.18 (УДК 53.01) ГРНТИ: 29.05.19
Яловенко С. Н.
Харьковский национальный университет радиоэлектроники DOI: 10.24412/2520-6990-2021-31118-24-28 ВЫВОД ЗАКОНА КУЛОНА.
Yalovenko S. N.
Kharkov National University of Radio Electronics THE NATURE OF THE MAGNETIC FIELD.
Аннотация.
Выводится закон Кулона из водоворотных представлений о строении частиц. Электрон - это водоворот электромагнитной волны, который обладает свойствами волны и частицы, а также массой покоя или правильнее сказать моментом вращения свёрнутой водоворотом волны, под которым мы понимаем массу покоя.
Abstract.
The Coulomb's law is derived from the whirlpool concepts of the structure of particles. An electron is a whirlpool of an electromagnetic wave, which has the properties of a wave and a particle, as well as a rest mass, or more correctly, the moment of rotation of a wave rolled up by a whirlpool, by which we mean rest mass.
Ключевые слова: Вывод закон Кулона, строение электрона.
Key words: Derivation Coulomb's law, the structure of the electron.
В современной физики, многие формулы получены экспериментально, методом последовательного приближения. Поэтому представляют интерес теории и гипотезы, в которых данные формулы (фундаментальные) выводятся из предполагаемых моделей или новых парадигм, а так же следствия следуемые из них с последующей их проверкой. На
сегодняшний день [1-4, 10-12] не существует ни одной гипотезы или теории, из которых бы выводился закон Кулона - это характеризует предел наших знаний. Существует корпускулярная теория, которая объясняет это явления за счёт вылетающих шариков- корпускул, но откуда берутся эти корпус-
