Approximate calculation of the mean energy of electrons produced by γ-rays in an ionization chamber

Atomic Energy ◽  
1961 ◽  
Vol 9 (2) ◽  
pp. 642-645
Author(s):  
A. K. Wal'ter ◽  
M. L. Gol'din ◽  
V. I. Slavin
Keyword(s):  
Ionization Chamber ◽  
Approximate Calculation ◽  
Γ Rays ◽  
The Mean

Negative Parity Levels in 30Si

1974 ◽  
Vol 52 (16) ◽  
pp. 1485-1491 ◽  
Author(s):  
M. Wayne Greene ◽  
H. H. Grawe ◽  
J. A. Kuehner
Keyword(s):  
Gamma Ray ◽  
Negative Parity ◽  
Coincidence Measurement ◽  
Model Structure ◽  
Polarization Direction ◽  
Decay Branch ◽  
Mean Lifetime ◽  
Doppler Shift Attenuation ◽  
Γ Rays ◽  
The Mean

A polarization direction correlation measurement of γ rays from the 7.044 MeV level in 30Si results in Jπ = 5− for this level and implies a Jπ = 4− assignment for the level at 6.503 MeV. A particle gamma ray coincidence measurement establishes a new decay branch (15 ± 4%) for the 6.503 MeV level to the 5.485 MeV Jπ = 3− level. The Doppler shift attenuation method was used to measure the mean lifetime of the 7.044 MeV level as [Formula: see text]. A simple shell model structure for the low lying negative parity states is presented and shown to be consistent with experimental measurements.

An analytical method for determining rate constants using a periodical irradiation technique

1969 ◽  
Vol 47 (24) ◽  
pp. 4531-4535 ◽  
Author(s):  
W. Kawakami ◽  
H. S. Isbin
Keyword(s):  
Rate Constants ◽  
Analytical Method ◽  
Apparent Rate Constant ◽  
Chloral Hydrate ◽  
Life Time ◽  
First Order ◽  
Radical Concentration ◽  
Γ Rays ◽  
The Mean

A new analytical method is presented for the determination of rate constants using a periodical irradiation technique. This method is applicable to reactions which have both a first and a second order termination for the chain radical concentration, and is illustrated for the radiolysis of aqueous solutions of chloral hydrate by 137Cs γ rays. The apparent rate constant of first order termination, and the mean chain life time of the chain radical were determined to be 1.10 s−1, and 0.25 s for 400 rad/min, at 22 °C, respectively.

The action of γ -rays on sodium deoxyribonucleate in solution - III. Denaturation

1960 ◽  
Vol 153 (950) ◽  
pp. 103-110 ◽  
Keyword(s):  
Hydrogen Bonds ◽  
Linear Function ◽  
Radiation Dosage ◽  
Cross Linking ◽  
Base Pairs ◽  
Titration Curves ◽  
Γ Rays ◽  
The Mean

The displacement of the titration curves at 25°C of herring sperm sodium deoxyribonucleate ( DNA ) irradiated in solution by γ -rays has been confirmed. Values for the mean extent of denaturation (β - ) which have been deduced from such curves agree with those obtained from the reversible titration curves that DNA exhibits at -0∙7°C. One effect of γ -irradiation was to displace these reversible curves asymmetrically in a manner which suggested that the hydrogen bonds linking adenine and thymine were more susceptible to rupture by γ -irradiation than were those which link cytosine and guanine. The logarithm of the fraction of titratable groups in helical regions of the DNA was a decreasing linear function of radiation dosage and the significance of this observation is discussed. In the first stages of irradiation, the rupture of cross-linking hydrogen bonds is very efficient and has a G value of thirty-eight base-pairs severed per 100 eV.

scholarly journals Comparison of entrance surface air kerma measurement with MTS-N (LiF: Mg, Ti) chips with a kilovoltage X-ray source

2021 ◽  
Vol 22 (1) ◽  
pp. 20-34
Author(s):  
Akintayo Daniel Omojola ◽  
Samuel Olaolu Adeneye ◽  
Michael Onoriode Akpochafor ◽  
Isiaka Olusola Akala ◽  
Azuka Anthonio Agboje
Keyword(s):  
Ionization Chamber ◽  
Radiation Detectors ◽  
Field Size ◽  
Peak Voltage ◽  
X Ray ◽  
Air Kerma ◽  
Image Distance ◽  
The Mean ◽  
Dose Accuracy ◽  
Entrance Surface Air Kerma

Objective: Radiation detectors are key components that ensure the accuracy and performances of dosimetry equipment. The study is aimed to compare the mean entrance surface air kerma (ESAK) between a DCT-10mm ionization chamber (IC) and MTS-N (LiF: Mg, Ti) chips when both detectors are exposed to ≤ 5mGy with a 10 by 10 field size, with an X-ray source and to determine the accuracy of the Thermoluminescent (TL) chips. Also, the dose will be compared to similar studies. Materials and Methods: A functional, Digital Radiography (DR) X-ray System was used. A DCT-10mm ionization chamber (IC) and an XR Multidetector was positioned at a Source to Image Distance (SID) of 100cm on polystyrene, about 20cm thick. An X-ray spectrum generated at a Practical Peak Voltage (PPV) of 60-107kV with Half Value Layer (HVL) of 2.4-4.3mmAl and filtration > 3mmAl was used. The same setup was used for the MTS-N chips. Results: The mean doses for 1-5 mGy with the MTS-N chips were 1.07±0.07, 1.60±0.13, 2.23±0.11, 2.58±0.07 and 3.45±0.10 mGy respectively, with accuracies of 7, 20, 26, 36 and 31%. Dose accuracy at 1and 2mGy was within 25% respectively. Dose accuracies at 3, 4 and 5mGy was within >25%. The correction factor for 1-5mGy was 0.94, 1.25, 1.35, 1.55 and 1.45 respectively. Conclusion: Validation of the MTS-N chips with the reference ionization chamber to this study was within 36%. The Radiation and Nuclear Safety Authority (STUK) recommends that ESAK be within 25% for entrance surface dose. ESAK accuracy mostly increased with dose as observed in this study.

scholarly journals Scattering of slow neutrons

1937 ◽  
Vol 162 (908) ◽  
pp. 127-143 ◽  
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Ionization Chamber ◽  
Percentage Increase ◽  
Quantitative Interpretation ◽  
Total Cross Sections ◽  
Paraffin Block ◽  
Γ Rays ◽  
Absorbing Elements ◽  
Slow Neutrons

The adsorption and scattering of slow neutrons have been studied by various methods. In their first survey, Amaldi, D'Agostino, Fermi, Pontecorvo, Rasetti and Segré (1935) investigated the absorption of slow neutrons by different elements inside a paraffin block. The number of slow neutrons capture in an indicator (e. g. silver). The values for the absorption coefficients which they obtained with this arrangement can be regarded as a measure of the ''true'' absorption of slow neutrons. Later, Dunning, Pegram, Fink and Mitchell (1935) measured the "total" cross-sections, i. e. the sum of the well-defined beam of slow neutrons, and a lithium-coated ionization chamber as indicator. Recently, Griffiths and Szilard (1937) have determined the cross-section of some strongly absorbing elements using the captured γ-rays from cadmium as indicator. The scattering of slow neutrons was studied for some elements by MItchell and Murphy (1935), Mitchell, Murphy and Whitaker (1936), Budnitzky and Kurtschatow (1935) Pontecorvo and Wick (1936), and others. In these experiments, the slow neutrons issuing from a paraffin block passed through an indicator (e. g. silver), and were scattered backwards from the substance under investigation. When thin scattered are used, the percentage increase of the radioactivity produced in the indicator gives a measure of the scattering cross-section. This method has the disadvantage, even in the case of good scatters, that the increase in the radioactivity of the indicator is usually small compared with the effect due to the primary neutrons. A quantitative interpretation of the results may be further complicated by the fact that the neutrons leave the surface of the paraffin block at angles from 0 to 90°. Also, multiple scattering is not avoided.

scholarly journals The ranges of the α-particles from the radioactive emanations and “A” products and from polonium

1932 ◽  
Vol 136 (829) ◽  
pp. 349-363 ◽  
Keyword(s):  
Long Range ◽  
Point Of View ◽  
Counting Methods ◽  
Γ Rays ◽  
The Mean ◽  
High Degree ◽  
Α Particles

The analysis of groups of α-particles by new counting methods has been described in previous papers, in which details have been given of the examination of the α-particles emitted by radium-C and -C' thorium-C and -C', and actinium-C and -C', including the long range particles. The methods have the advantage that any appreciable inhomogeneity of a group of α-particles is readily detected, and moreover, the mean range of a group may be directly measured with a high degree of precision. The experiments have now been extended to an examination of the α-particles emitted by the emanations and “A” products of the three radioactive series, and by polonium. The examination of these α-ray groups is not only of great interest from the point of view of the radioactive transformations, but also for the possible connection with the emission of γ-rays.

scholarly journals Evaluation of stray radiation to the operator for five hand-held dental X-ray devices

2019 ◽  
Vol 48 (5) ◽  
pp. 20180301 ◽  
Author(s):  
Richard Smith ◽  
Richard Tremblay ◽  
Graeme M Wardlaw
Keyword(s):  
Digital Image ◽  
Protected Area ◽  
Ionization Chamber ◽  
Portable Devices ◽  
X Ray ◽  
Air Kerma ◽  
Tissue Equivalent ◽  
Stray Radiation ◽  
The Mean ◽  
Occupational Radiation

Objectives: Evaluate stray radiation to the operator, as represented by a plane within the significant zone of occupancy (SZO), produced by five models of hand-held intraoral dental X-ray devices (HIDXDs). Methods: The stray radiation for five models of HIDXDs was measured, using an anthropomorphic tissue-equivalent head phantom as a scattering object. An ionization chamber was used to measure the air kerma (μGy) at 63 positions in a 160 cm high by 60 cm wide plane that was 10 cm behind the X-ray device, identified as being within the SZO. Results: Based on the measured air kerma from stray radiation of five different HIDXDs, the estimated annual air kerma at all measured spatial positions was calculated. When calculated using a median air kerma of 0.8 mGy at the distal end of the cone, as typically required for digital image receptors, 1 the ranges for estimated annual air kerma in the SZO across the devices were 0.14–0.77 mGy for the median, 0.41–1.01 mGy for the mean, and 1.32–2.55 mGy for the maximum. Similarly, when calculated using a median air kerma of 1.6 mGy as typically required for D-speed film, 2 the ranges for estimated annual air kerma across the devices were 0.28–1.54 mGy for the median, 0.83–2.03 mGy for the mean, and 2.64–5.10 mGy for the maximum. Conclusions: From measured air kerma values of stray radiation in the SZO, estimated annual exposures to the operator for HIDXDs are expected to be greater than from conventional wall-mounted or portable devices activated from a protected area (at a distance or behind shielding). HIDXDs should therefore only be used when patient accessibility makes their use necessary and the use of a portable device on a stand or a wall-mounted device is not reasonably feasible. This approach would keep occupational radiation exposures of dental workers as low as reasonably achievable.

IMPROVEMENT OF RADIOSENSITIVE LIQUID-CORE MICROCAPSULES BY YTTRIUM POLYMERIZATION

2007 ◽  
Vol 17 (01n02) ◽  
pp. 33-40 ◽  
Author(s):  
S. HARADA ◽  
S. EHARA ◽  
K. ISHII ◽  
H. YAMAZAKI ◽  
S. MATSUYAMA ◽  
...  
Keyword(s):  
Hyaluronic Acid ◽  
Liquid Core ◽  
Acid Solutions ◽  
Alginate Solution ◽  
X Ray ◽  
The Core ◽  
Radiation Induced ◽  
Γ Rays ◽  
The Mean ◽  
Maximum Content

Microcapsules comprising alginate and hyaluronic acid that can be decomposed by radiation are under development. Previously, we observed that radiation efficiently decomposes microcapsules comprising alginate and hyaluronic acid in the ratio 2:1 by weight. In this study, Yttrium ( Y ) was added to these microcapsules to improve their decomposition by radiation. Hyaluronic acid solutions (0.1% weight/volume) were mixed into 0.2% alginate solution, and carboplatin (0.2 mmol) was added; the resultant was used for capsule preparation. Capsules were prepared by spraying the material into mixtures of 4.34% CaCl 2 solution supplemented with Y at final concentrations from 0 to 1.0 × 10−2%. These capsules were irradiated by a single dose of 0.5, 1.0, 1.5, or 2 Gy with 60Co γ-rays. Immediately after irradiation, we observed the release of the core contents of the microcapsule using a micro Particle Induced X-ray Emission (PIXE) camera. The mean diameter of the microcapsules was 37.3 ± 7.8 μm . Maximum content of radiation-induced release was observed for liquid-core microcapsules prepared by polymerization in a 4.34% CaCl 2 solution supplemented with 5.5 × 10−3% Y .

scholarly journals The action of radiations on bacteria III—γ-rays on growing and on non-proliferating bacteria

1937 ◽  
Vol 123 (830) ◽  
pp. 1-21 ◽  
Keyword(s):  
High Intensity ◽  
Nutrient Medium ◽  
Ionization Chamber ◽  
Biological Action ◽  
Average Intensity ◽  
Essential Difference ◽  
Γ Rays ◽  
Target Theory ◽  
Cylindrical Ionization Chamber ◽  
Growth Of Bacteria

The authors’ work (Lea, Haines and Coulson 1936)* on the action of ∝ -rays and β -rays on bacteria was mainly concerned with tests of the validity of the target hypothesis. Experiments using γ -rays were commenced with the object of obtaining still further evidence on this question. While no essential difference is to be anticipated in the biological action of γ -rays and β -rays, the greater penetrating power of the former makes certain experiments possible which could not be carried out with β -rays. Thus, in a disinfection experiment lasting several hours, it is convenient to be able to expose a relatively large quantity of liquid and to follow the course of disinfection by taking samples at intervals. Further, it is possible by the same method to observe the influence of radiation upon the growth of bacteria in a liquid nutrient medium. This last type of experiment seemed particularly suitable as a test of the target theory, since on that theory one would expect growth in the medium, and death produced by the radiation, to take place independently and at their normal rates, a result not to be anticipated on other theories. Actually, however, the issue was found to be complicated by the fact that the radiation, in addition to its lethal action, had the effect of causing the production of organisms many times longer than the normal. The present paper, therefore, is concerned with an investigation of these long forms. Approximately 920 mg. of radium were available in various containers; the filtration used was sufficient to ensure that only the γ -rays reached the biological material. Owing to the necessity of using the radium in containers designed for other experiments, and of working at short distances in order to obtain a sufficiently high intensity, the radiation was by no means of uniform intensity throughout the tube of liquid exposed. Mixing by convection currents, and during the process of sampling, was probably sufficient to ensure that over an extended time each organism received a dose of radiation corresponding to the average intensity over the whole volume of liquid. This average intensity was measured with the aid of a cylindrical ionization chamber of graphite, having a size approximating to that of the exposed tube. The ionization current was measured with an instrument recently described (Lea 1937).

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