Radioactive Pollution

2002 ◽  
Keyword(s):  
Atomic Number ◽  
Electromagnetic Waves ◽  
Neutron Radiation ◽  
Atomic Weight ◽  
Atomic Mass Unit ◽  
X Rays ◽  
Orbital Electron ◽  
Γ Rays ◽  
The Difference ◽  
A Charge

Radiation that, on passage through matter, produces ions by knocking electrons out of their orbits is called ionizing radiation. This radiation is produced through decomposition of unstable, naturally occurring or synthetic elements referred to as radionuclides. The four types of radiation are ∝-particles, β-particles, γ-rays, and neutrons. The ∝-particles have a mass of two protons and two neutrons and a charge of +2; β -particles are electrons with a mass of 0.00055 atomic mass unit (amu) and a charge of –1; γ -rays and X-rays are high-frequency electromagnetic waves with no mass and no charge. The difference between γ -rays and X-rays is that γ -rays occur naturally, whereas X-rays are generated. In addition, γ -rays are of higher frequency than X-rays. Release of an ∝ -particle leads to the formation of a daughter element with an atomic number 2 units lower and an atomic weight 4 units lower than that of the parent nuclide. Similarly, release of a β -particle from the nucleus causes conversion of a neutron to a proton, producing a daughter element with the same atomic weight as the parent nuclide but with its atomic number increased by 1 unit. Neutron radiation does not occur naturally and is released only from synthetic radionuclides. Neutrons, which have no charge, are formed from protons. This conversion is accompanied by the release of an orbital electron from the atom. Neutrons produce ions indirectly, by collisions with hydrogen atoms. The impact knocks out protons, which in turn produce ions on passage through matter. Capture of a neutron forms an isotope of the parent nuclide with its atomic weight increased by 1 unit. The mode of action of particles (∝ and β ) varies from that of photons (γ - and X-rays). When ∝- or β -particles travel through matter, their electric charges (positive or negative) cause ionization of the atoms in the matter. This is called a direct effect. Whereas the track of ∝- particles is short and straight, β -particles scatter, frequently producing a wavy track. Gamma- and X-rays act indirectly.

scholarly journals The sensitivity of atomic analysis by X-rays

1932 ◽  
Vol 135 (828) ◽  
pp. 637-656 ◽  
Keyword(s):  
Atomic Number ◽  
Target Material ◽  
High Sensitivity ◽  
Major Constituent ◽  
X Rays ◽  
Depth Of Penetration ◽  
X Ray ◽  
Constituent Element ◽  
The Difference ◽  
Atomic Analysis

In a previous paper it was shown that 0·0007 per cent, of 29 Cu and 0·0003 per cent, of 26 Fe could be detected in 30 Zn by atomic analysis by X-ray spectroscopy. This sensitivity is greater than that which was claimed by Noddack, Tacke, and Berg, who set the limit at about 0·1 per cent, for non-metals, and by Hevesy, who stated it to be about 0·01 per cent, for an element present in an alloy. It was later suggested by Hevesy that the high value of the sensitivity which we found might result from the fact that some of the alloys we had used were composed of elements of almost equal atomic number, and that the sensitivity would be smaller for a constituent of low atomic number mixed with a major constituent of high atomic number. To elucidate these disagreements we have made further observations of the sensitivity with elements of different atomic number and have investigated the conditions which can influence the sensitivity. The Factors Determining Sensitivity . The detection of one element in a mixture of elements depends upon the identification of its K or L lines in the general spectrum emitted by the mixture under examination. The intensity with which these lines are excited in the target (“excited intensity”) is proportional to the number of atoms of the constituent element excited, i. e ., to its concentration and to the volume of the target in which the cathode ray energy is absorbed. The depth of penetration of the cathode rays is determined by the density of the target material and by their velocity ( i. e ., by the voltage applied to the X-ray tube). Schonland has shown that the range of homogeneous cathode rays in different elements, expressed as a mass per unit area, is approximately constant and is independent of the atomic number of the absorbing element. When their velocity is increased, the cathode rays will penetrate to a greater depth, and therefore a greater number of atoms of all constituents will be ionised. This will increase the “excited intensity” of the lines due to the particular constituent sought equally with those lines of the other elements present. The intensity of a line further depends upon the difference between the voltage applied to the X-ray tube and that necessary to excite the series. For these reasons, a high applied voltage is required for a high sensitivity.

Charles Glover Barkla, 1877-1944

1947 ◽  
Vol 5 (15) ◽  
pp. 341-366 ◽  
Keyword(s):  
Electromagnetic Wave ◽  
Atomic Number ◽  
Chemical Element ◽  
Three Dimensional ◽  
Atomic Weight ◽  
New Method ◽  
X Rays

The name of Barkla will always be distinguished on account of his fundamental researches on Rontgen rays. In 1905 he made the discovery that scattered X-rays are polarized, but only to a certain degree. He also established the fact that each chemical element can radiate Röntgen rays having properties characteristic of that element, and in this way he anticipated the assignment to each element of an ‘atomic number’, the number being, in general, about one-half the atomic weight. For these discoveries he was admitted a Fellow of the Society in 1912, his investigations having resulted in the most important additions to our knowledge of the Röntgen rays since their discovery. Barkla consistently adopted the electromagnetic wave or pulse theory of the nature of the rays. At the end of the year 1912, von Laue put forward his theory of the diffraction of X-rays by transmission through a crystal regarded as a three-dimensional grating, thus introducing an entirely new’ method of investigation.

scholarly journals The absorption in lead of the γ-rays emitted by radium and radium C

1915 ◽  
Vol 91 (630) ◽  
pp. 396-404 ◽  
Keyword(s):  
Atomic Weight ◽  
Great Accuracy ◽  
Complete Analysis ◽  
Characteristic Radiation ◽  
Anomalous Effect ◽  
Γ Radiation ◽  
Additional Information ◽  
Absorbing Material ◽  
Γ Rays ◽  
The Difference

In a previous paper by Rutherford and the author attention has been drawn to the fact that the two types of γ-radiation emitted by radium B and radium c which are exponentially absorbed by aluminium both show irregular absorption curves when lead is used as the absorbing material. The curve obtained for pure radium C was observed to fall far more rapidly than was to be expected only after traversing a thickness of 1·5cm of lead. The absorption curve in lead of the γ-rays from radium B was obtained by taking the difference between the radium (B+C) and the radium C curves. The results so obtained were not determined with very great accuracy, but they served to show that in this case, to, the absorption is not exponential , and that the absorption coefficient rapidly diminished from about μ =11(cm. -1 ) to μ =2(cm -1 ). The accuracy of the curves did not, however, permit of their complete analysis as in the case of those previously obtained for aluminium. During the course of his work on characteristic radiations Barkla has Pointed out and investigated the anomalous effect on the absorption of a characteristic radiation by an element whose atomic weight is near to that of the element which emits the radiation. His experiments were, however, confined to elements of comparatively low atomic weight. As the atomic weights of radium B and radium C can only differ by a small amount, and as they have atomic numbers differing only by unity, viz., radium B=82 and radium C=83, it seemed of importance to determine accurately the absorption curves in lead, and to examine whether any additional information can be obtained which may indicate whether the radiations emitted by radium B and radium C are characteristic of these elements and fall into the series given by Barkla.

scholarly journals The Application of Thick Hydrogenated Amorphous Silicon Layers to Charged Particle and X-Ray Detection

1989 ◽  
Vol 149 ◽  
Author(s):  
V. Perez-Mendez ◽  
G. Cho ◽  
I. Fujieda ◽  
S. N. Kaplan ◽  
S. Qureshi ◽  
...  
Keyword(s):  
Amorphous Silicon ◽  
Radiation Effects ◽  
Neutron Radiation ◽  
Signal Amplitude ◽  
X Rays ◽  
Noise Sources ◽  
Leakage Currents ◽  
Γ Rays ◽  
Neutron Radiation Effects ◽  
Position Sensitive Detectors

ABSTRACTWe outline the characteristics of thick hydrogdenated amorphous silicon layers which are optimized for the detection of charged particles, x-rays and γ-rays. Signal amplitude as a function of the linear energy transfer of various particles are given. Noise sources generated by the detector material and by the thin film electronics - a-Si:H or polysilicon proposed for pixel position sensitive detectors readout are described, and their relative amplitudes are calculated. Temperature and neutron radiation effects on leakage currents and the corresponding noise changes are presented.

scholarly journals Energy relations in the β-ray type of radioactive disintegration

1933 ◽  
Vol 141 (845) ◽  
pp. 502-511 ◽  
Keyword(s):  
Energy Difference ◽  
Atomic Weight ◽  
Maximum Energy ◽  
Excess Energy ◽  
Binding Energies ◽  
Upper Limit ◽  
Γ Rays ◽  
The Difference ◽  
Band Spectra ◽  
Energy Relations

The difficulties connected with the continuous β-disintegration are well known. The fact that a given isotope of any element has a definite atomic weight suggests that the energy of the normal state of any nucleus is quantized ; further evidence is afforded by the alternating intensities in band spectra. Evidence from the fine structure of α -rays and from the γ-rays, proves that nuclei are capable of existing in quantized excited states. In fact, in all transformations where α -particles, γ-radiation or protons are ejected from nuclei, the evidence suggests, (i) that the nuclear energy is quantized, and (ii) that energy is conserved. On the other hand, when a nucleus P transforms itself into a nucleus Q by emission of a β-particle, the β-particle has all energies between zero and a definite upper limit. One may either conclude that the energy either of P or of Q is not quantized, or that energy is not conserved in the transition. Since the a-transitions leading up to P , and starting from Q , show no sign of any indefiniteness in the energy, it is difficult to accept the former alternative ; and it is thus usual to suppose that energy is not conserved. In this paper we make the suggestion that the sharp upper limit of the β-rav spectrum is a significant parameter with which to classify a β-disintegration. We suggest the following hypotheses : two elements P , Q , such that P -> Q is a β-disintegration, both possess definite atomic weights, and hence definite binding energies. Following Heisenberg* we assume that β-disintegration can only take place if the energy E P of the nucleus P is higher than the energy E q of the nucleus Q. We make the new assumption that the energy difference E P — E q is equal to the upper limit of the i. e., to the maximum energy with which a β-particle can be expelled. According to our assumption, the β-particle may be expelled with less energy than the difference of the energies E P — E q , of the two nuclei, but not with more energy . We do not wish in this paper to dwell on what happens to the excess energy in those disintegrations in which the electron is emitted with less than the maximum energy. We may, however, point out that if the energy merely disappears, implying a breakdown of the principle of energy conservation, then in a β-ray decay energy is not even statistically conserved. Our hypothesis is, of course, also consistent with the suggestion of Pauli that the excess energy is carried off by particles of great penetrating power such as neutrons of electronic mass.

scholarly journals The absolute energies of the groups in magnetic β-ray spectra

1924 ◽  
Vol 105 (729) ◽  
pp. 60-69 ◽  
Keyword(s):  
Magnetic Field ◽  
Wave Length ◽  
X Rays ◽  
Homogeneous Groups ◽  
Absorption Energy ◽  
Length Measurements ◽  
Γ Rays ◽  
Γ Ray ◽  
The Absolute ◽  
The Difference

Most β-ray bodies emit several homogeneous groups of β-rays, and the energies of the electrons forming these groups may be found from the deflection they suffer in a magnetic field. Various experiments have shown that these groups are due to the conversion, according to the quantum relation, of γ-rays in the different electronic levels of the atom. In fact, the energy of any group is of the form E 1 = hv — (absorption energy of level). Two β-ray groups due to the conversion of a γ-ray of definite frequency in the K and L levels of the atom will differ in energy by the difference in energy between the K and L absorption energies. Both in testing this equation, and in using it to deduce frequencies of the γ-rays, it is necessary to compare energies of β-rays determined in terms of a magnetic field, with absorption energies deduced from wave-length measurements of X-rays. It is thus important to obtain values of the absolute β-ray energies as accurate as possible. The most accurate previous values were those of Rutherford and Robinson.

scholarly journals Comparison of Rhenium and Iodine as Contrast Agents in X-Ray Imaging

2021 ◽  
Vol 2021 ◽  
pp. 1-15
Author(s):  
José Carlos De La Vega ◽  
Pedro Luis Esquinas ◽  
Jovan Kaur Gill ◽  
Selin Jessa ◽  
Bradford Gill ◽  
...  
Keyword(s):  
Contrast Agents ◽  
Atomic Number ◽  
Imaging Techniques ◽  
Absorbed Dose ◽  
X Rays ◽  
Micro Computed Tomography ◽  
Low Contrast ◽  
X Ray ◽  
X Ray Imaging ◽  
The Difference

Purpose. The majority of X-ray contrast agents (XCA) are made with iodine, but iodine-based XCA (I-XCA) exhibit low contrast in high kVp X-rays due to iodine’s low atomic number (Z = 53) and K-edge (33.1 keV). While rhenium is a transition metal with a high atomic number (Z = 75) and K-edge (71.7 keV), the utilization of rhenium-based XCA (Re-XCA) in X-ray imaging techniques has not been studied in depth. Our study had two objectives: (1) to compare both the image quality and the absorbed dose of I- and Re-XCA and (2) to prepare and image a rhenium-doped scaffold. Procedures. I- and Re-XCA were prepared and imaged from 50 to 120 kVp by Micro-computed tomography (µCT) and digital radiography and from 120 to 220 kVp by planar X-ray imaging. The scans were repeated using 0.1 to 1.6 mm thick copper filters to harden the X-ray beam. A rhenium-doped scaffold was prepared via electrospinning, used to coat catheters, and imaged at 90 kVp by µCT. Results. I-XCA have a greater contrast-to-noise ratio (CNR) at 50 and 80 kVp, but Re-XCA have a greater CNR at >120 kVp. The difference in CNR is increased as the thickness of the copper filters is increased. For instance, the percent CNR improvement of rhenium over iodine is 14.2% with a 0.6 mm thick copper filter, but it is 59.1% with a 1.6 mm thick copper filter, as shown at 120 kVp by µCT. Upon coating them with a rhenium-doped scaffold, the catheters became radiopaque. Conclusions. Using Monte Carlo simulations, we showed that it is possible to reduce the absorbed dose of high kVp X-rays while allowing the acquisition of high-quality images. Furthermore, radiopaque catheters have the potential of enhancing the contrast during catheterizations and helping physicians to place catheters inside patients more rapidly and precisely.

scholarly journals Absorption of hard γ-rays by elements

1924 ◽  
Vol 105 (733) ◽  
pp. 507-519 ◽  
Keyword(s):  
Atomic Number ◽  
High Frequency ◽  
Accurate Determination ◽  
Simple Relation ◽  
Balance Method ◽  
X Rays ◽  
True Absorption ◽  
Relative Absorption ◽  
Mutual Comparison ◽  
Γ Rays

In this paper an account will be given of an accurate determination by a balance method of the relative absorption in a large number of elements of γ -radiation from Ra B + C filtered through 1 cm. of lead. The object of these experiments was to find out whether there is a simple relation between the absorption in an element and its atomic number, and also whether the nuclear electrons make a sensible contribution. As a result of these measurements, it will be shown that the laws of absorption of γ -rays of high frequency can be linked up with the corresponding laws known for X-rays of much lower frequency. A mutual comparison will also throw some light on the relative part played by scattering and true absorption in the passage of penetrating radiation through matter. An account of earlier work on the absorption of γ -rays by matter will be found in the standard works on radioactivity— e. g. , by Rutherford (1913) and by Meyer and Schweidler (1916). It is, however, necessary to mention briefly some results of the later work relevant to the present experiments.

The Photoelectric Absorption of Gamma Rays

1931 ◽  
Vol 27 (1) ◽  
pp. 103-112 ◽  
Author(s):  
L. H. Gray
Keyword(s):  
Absorption Coefficient ◽  
Atomic Number ◽  
Gamma Rays ◽  
Wave Length ◽  
X Rays ◽  
Photoelectric Absorption ◽  
Empirical Law ◽  
Γ Rays ◽  
Image Position

No satisfactory formula has so far been derived theoretically for the photoelectric absorption of X-rays and γ-rays. The empirical lawhas hitherto been generally accepted as giving approximately the variation of the photoelectric absorption coefficient per electron, with atomic numberZand wave length λ for X-rays of wave length greater than 100 X.U., and the validity of this law has often been assumed for γ-rays also.

Contribution of x-ray total reflection to the background intensity in EPMA

1990 ◽  
Vol 48 (2) ◽  
pp. 202-203
Author(s):  
Werner P. Rehbach ◽  
Peter Karduck
Keyword(s):  
Atomic Number ◽  
Target Material ◽  
Total Reflection ◽  
Background Intensity ◽  
X Rays ◽  
Characteristic Radiation ◽  
X Ray

In the EPMA of soft x rays anomalies in the background are found for several elements. In the literature extremely high backgrounds in the region of the OKα line are reported for C, Al, Si, Mo, and Zr. We found the same effect also for Boron (Fig. 1). For small glancing angles θ, the background measured using a LdSte crystal is significantly higher for B compared with BN and C, although the latter are of higher atomic number. It would be expected, that , characteristic radiation missing, the background IB (bremsstrahlung) is proportional Zn by variation of the atomic number of the target material. According to Kramers n has the value of unity, whereas Rao-Sahib and Wittry proposed values between 1.12 and 1.38 , depending on Z, E and Eo. In all cases IB should increase with increasing atomic number Z. The measured values are in discrepancy with the expected ones.

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