YIELDS AND ANGULAR DISTRIBUTIONS OF FAST PHOTOPROTONS

1963 ◽  
Vol 41 (6) ◽  
pp. 871-880 ◽  
Author(s):  
O. M. Mracek Mitchell ◽  
K. G. McNeill
Keyword(s):  
Maximum Energy ◽  
Angular Distributions ◽  
Bremsstrahlung Spectrum

Measurements are described on the angular distributions of fast photoprotons (Ep > 8 Mev) ejected from 16 elements of [Formula: see text] by a bremsstrahlung spectrum of 22-Mev maximum energy. Some shell features are observed which, together with results of other authors, are discussed in terms of the Wilkinson model of photodisintegration.

scholarly journals CROSS-SECTIONS FOR PHOTONUCLEAR REACTIONS 93Nb(γ,n)92mNb AND 93Nb(γ,n)92tNb IN THE END-POINT BREMSSTRAHLUNG ENERGIES 36...91 MeV

2020 ◽  
pp. 148-153
Author(s):  
A.N. Vodin ◽  
O.S. Deiev ◽  
I.S. Timchenko ◽  
S.N. Olejnik ◽  
A.S. Kachan ◽  
...  
Keyword(s):  
Energy Range ◽  
Cross Sections ◽  
Maximum Energy ◽  
Reaction Cross ◽  
Bremsstrahlung Spectrum ◽  
Photonuclear Reactions ◽  
End Point ◽  
Γ Ray ◽  
First Time ◽  
Good Agreement

The flux-weighted averaged over the energy range of bremsstrahlung spectrum from reaction threshold up to the maximum energy of γ-ray cross-sections <σ(E)> of the 93Nb(γ,n)92mNb and 93Nb(γ,n)92tNb photonuclear reactions were determined by the gamma-activation method within the end-point bremsstrahlung energies Еmax = 36…91 MeV. Activation of 93Nb targets has been done by a bremsstrahlung flux using an electron beam at the linear accelerator LUE-40 at RDC "Accelerator" NSC KIPT. The γ-ray spectra of irradiated targets were registered using the HPGe detector with an energy resolution of 1.8 keV for the 1332 keV line 60Co. To control the bremsstrahlung flux we used natMo witness-targets and a reaction cross-section of 100Mo(γ,n)99Mo. Obtained experimental cross-sections <σ(E)> of the studied reactions are in good agreement with the theoretical values calculated within TALYS 1.9 code and the results of other authors. The averaged cross-sections <σ(E)> of the 93Nb(γ,n)92mNb and 93Nb(γ,n)92tNb reactions in the energy range 35...45 MeV and > 70 MeV were obtained for the first time.

The nuclear alinement of promethium isotopes and the decay scheme of 149 Pm

1960 ◽  
Vol 259 (1298) ◽  
pp. 377-385 ◽  
Keyword(s):  
Excited State ◽  
Low Temperature ◽  
Decay Scheme ◽  
Maximum Energy ◽  
Angular Distributions ◽  
Ionic State

Nuclear alinement of the isotopes 149 Pm and 151 Pm has been obtained in the ethyl sulphate and double nitrate lattices by the low-temperature alinement method. The anisotropic γ -ray angular distributions were used to detect this alinement. The results suggest that in the double-nitrate lattice the lowest ionic state of Pm 3+ is a singlet and that alinement arises through a ‘pseudo-quadrupole’ mechanism. Beta and γ -spectroscopy measurementsshow that the 285 keV γ -ray in the decay of 149 Pm is associated with a weak (1.8 ± 0.3 %) β -group of maximum energy 0.77 ± 0.05 MeV. The alinement measurements are consistent with this 285 keV γ -ray being principally M 1 with the spin of the excited state being 5/2 or 9/2.

The Ratio between Absorbed Dose, Kerma and Ionization Kerma for Small-size Fields

2019 ◽  
pp. 74-77
Author(s):  
В. Климанов ◽  
V. Klimanov ◽  
Ж. Галяутдинова ◽  
Zh. Galyautdinova ◽  
М. Колыванова ◽  
...  
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Circular Cross Section ◽  
Absorbed Dose ◽  
Maximum Energy ◽  
Bremsstrahlung Spectrum ◽  
Cross Sectional ◽  
The Monte Carlo Method ◽  
Small Fields ◽  
The Relationship

Purpose: Research of the relationships between spatial distributions in water of the main dosimetric values, namely the absorbed dose, kerma and ionization kerma, for small-size fields with a circular cross section created by divergent beams of bremsstrahlung spectrum with a maximum energy of 6 MeV. Material and methods: Using the Monte-Carlo method with the codes EGSnrc and MCNP4C2, calculations were carried out for these distributions in a water phantom for beam radii on the phantom surface from 0.1 to 3.0 cm and for depths up to 40 cm. The ratio at depths up to 5 cm, where there is a so-called build-up area, is studied in particular detail. Results: The results of calculations show that the ratio of ionization kerma to kerma for such beams at depths up to 40 cm is practically constant and equal to 0.9930 ± 0.0005. The ratio of the absorbed dose to the ionization kerma, in contrast to conventional square beams with a cross-sectional area  20 cm2, is much less than unity at radii of 1 cm at all the depths considered. Conclusion: The data obtained show that the relationship between absorbed dose, kerma and ionization kerma for photon fields produced by beams of small cross sections is very different from that for traditional beams. This circumstance should be taken into account when conducting dosimetry of small fields.

EM of rapidly solidified permanent magnets

1992 ◽  
Vol 50 (1) ◽  
pp. 198-199
Author(s):  
Raja K. Mishra
Keyword(s):  
Melt Spinning ◽  
Permanent Magnets ◽  
Dark Field Image ◽  
Dark Field ◽  
Maximum Energy ◽  
Quench Rate ◽  
Maximum Energy Product ◽  
Energy Product ◽  
Annular Dark Field ◽  
Rapidly Solidified

The discovery of a new class of permanent magnets based on Nd2Fe14B phase in the last decade has led to intense research and development efforts aimed at commercial exploitation of the new alloy. The material can be prepared either by rapid solidification or by powder metallurgy techniques and the resulting microstructures are very different. This paper details the microstructure of Nd-Fe-B magnets produced by melt-spinning.In melt spinning, quench rate can be varied easily by changing the rate of rotation of the quench wheel. There is an optimum quench rate when the material shows maximum magnetic hardening. For faster or slower quench rates, both coercivity and maximum energy product of the material fall off. These results can be directly related to the changes in the microstructure of the melt-spun ribbon as a function of quench rate. Figure 1 shows the microstructure of (a) an overquenched and (b) an optimally quenched ribbon. In Fig. 1(a), the material is nearly amorphous, with small nuclei of Nd2Fe14B grains visible and in Fig. 1(b) the microstructure consists of equiaxed Nd2Fe14B grains surrounded by a thin noncrystalline Nd-rich phase. Fig. 1(c) shows an annular dark field image of the intergranular phase. Nd enrichment in this phase is shown in the EDX spectra in Fig. 2.

Parallel Detection of Electron Energy Loss Spectra in Direct Mode

1990 ◽  
Vol 48 (2) ◽  
pp. 82-83
Author(s):  
Eckhard Quandt ◽  
Stephan laBarré ◽  
Andreas Hartmann ◽  
Heinz Niedrig
Keyword(s):  
Energy Loss ◽  
Electron Energy ◽  
Energy Resolution ◽  
Large Angle ◽  
Maximum Energy ◽  
Semiconductor Detectors ◽  
Parallel Detection ◽  
Photodiode Arrays ◽  
Electron Energy Loss ◽  
Electron Energy Loss Spectra

Due to the development of semiconductor detectors with high spatial resolution -- e.g. charge coupled devices (CCDs) or photodiode arrays (PDAs) -- the parallel detection of electron energy loss spectra (EELS) has become an important alternative to serial registration. Using parallel detection for recording of energy spectroscopic large angle convergent beam patterns (LACBPs) special selected scattering vectors and small detection apertures lead to very low intensities. Therefore the very sensitive direct irradiation of a cooled linear PDA instead of the common combination of scintillator, fibre optic, and semiconductor has been investigated. In order to obtain a sufficient energy resolution the spectra are optionally magnified by a quadrupole-lens system.The detector used is a Hamamatsu S2304-512Q linear PDA with 512 diodes and removed quartz-glas window. The sensor size is 13 μm ∗ 2.5 mm with an element spacing of 25 μm. Along with the dispersion of 3.5 μm/eV at 40 keV the maximum energy resolution is limited to about 7 eV, so that a magnification system should be attached for experiments requiring a better resolution.

Spectral and Topographic Microstructure of Brain Alpha Activity During Drowsiness at Sleep Onset and REM Sleep

2000 ◽  
Vol 14 (3) ◽  
pp. 151-158 ◽  
Author(s):  
José Luis Cantero ◽  
Mercedes Atienza
Keyword(s):  
Rem Sleep ◽  
Spectral Component ◽  
Sleep Onset ◽  
Quantitative Information ◽  
Maximum Energy ◽  
Alpha Activity ◽  
The Other ◽  
Classification Algorithms ◽  
Microstructural Properties ◽  
Brain States

Abstract High-resolution frequency methods were used to describe the spectral and topographic microstructure of human spontaneous alpha activity in the drowsiness (DR) period at sleep onset and during REM sleep. Electroencephalographic (EEG), electrooculographic (EOG), and electromyographic (EMG) measurements were obtained during sleep in 10 healthy volunteer subjects. Spectral microstructure of alpha activity during DR showed a significant maximum power with respect to REM-alpha bursts for the components in the 9.7-10.9 Hz range, whereas REM-alpha bursts reached their maximum statistical differentiation from the sleep onset alpha activity at the components between 7.8 and 8.6 Hz. Furthermore, the maximum energy over occipital regions appeared in a different spectral component in each brain activation state, namely, 10.1 Hz in drowsiness and 8.6 Hz in REM sleep. These results provide quantitative information for differentiating the drowsiness alpha activity and REM-alpha by studying their microstructural properties. On the other hand, these data suggest that the spectral microstructure of alpha activity during sleep onset and REM sleep could be a useful index to implement in automatic classification algorithms in order to improve the differentiation between the two brain states.

ANALYSIS OF STAND RESEARCH RESULTS OF AXIAL DYNAMIC FORCE IN DRILLING BY THREE ROLLER CONE BIT

2019 ◽  
pp. 81-93
Author(s):  
В. М. Мойсишин ◽  
M. V. Lyskanych ◽  
R. A. Zhovniruk ◽  
Ye. P. Majkovych
Keyword(s):  
Low Frequency ◽  
Maximum Energy ◽  
Dynamic Force ◽  
Low Frequency Oscillation ◽  
Drilling Tool ◽  
Rock Destruction ◽  
Frequency Components ◽  
Harmonic Components ◽  
Experimental Values ◽  
Harmful Effects

The purpose of the proposed article is to establish the causes of oscillations of drilling tool and the basic laws of the distribution of the total energy of the process of changing the axial dynamic force over frequencies of spectrum. Variable factors during experiments on the classical plan were the rigidity of drilling tool and the hardness of the rock. According to the results of research, the main power of the process of change of axial dynamic force during drilling of three roller cone bits is in the frequency range 0-32 Hz in which three harmonic frequency components are allocated which correspond to the theoretical values of low-frequency and gear oscillations of the chisel and proper oscillations of the bit. The experimental values of frequencies of harmonic components of energy and normalized spectrum as well as the magnitude of the dispersion of the axial dynamic force and its normalized values at these frequencies are presented. It has been found that with decreasing rigidity of the drilling tool maximum energy of axial dynamic force moves from the low-frequency oscillation region to the tooth oscillation area, intensifying the process of rock destruction and, at the same time, protecting the tool from the harmful effects of the vibrations of the bit. Reducing the rigidity of the drilling tool protects the bit from the harmful effects of the vibrations generated by the stand. The energy reductions in these fluctuations range from 47 to 77%.

scholarly journals Anomaly in photoelectron angular distributions

2007 ◽  
Vol 76 (1) ◽  
Author(s):  
Jingtao Zhang ◽  
L. D. van Woerkom ◽  
Dong-Sheng Guo ◽  
R. R. Freeman
Keyword(s):  
Angular Distributions ◽  
Photoelectron Angular Distributions
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