scholarly journals Nuclear Excitation Processes in Astrophysical Plasmas

Astrophysics ◽  
10.5772/36670 ◽  
2012 ◽  
Author(s):  
Gilbert Gosselin ◽  
Peter Mohr ◽  
Vincent Meot ◽  
Pascal Morel
Keyword(s):  
Nuclear Excitation ◽  
Astrophysical Plasmas ◽  
Excitation Processes

scholarly journals Toward the possibility of 229Th isomeric nuclear state excitation by two-color laser field

2019 ◽  
Vol 220 ◽  
pp. 01001 ◽  
Author(s):  
Anatoli Andreev ◽  
Andrey Savel’ev ◽  
Sergey Stremoukhov ◽  
Olga Shoutova
Keyword(s):  
Energy Transport ◽  
Spin Dynamics ◽  
High Harmonic ◽  
Imaging Study ◽  
Resonance Wavelength ◽  
Nuclear State ◽  
Nuclear Excitation ◽  
Complex Molecules ◽  
Nanoscale Imaging ◽  
Excitation Processes

The process of high harmonic generation (HHG) has a wide area of different applications, in particular, in nanoscale imaging, study the nanoscale energy transport in complex molecules and solids, probe the charge and spin dynamics with the femtosecond time resolution, etc. Here we discuss a possible application of HHG effect related with the study of nuclear transition dynamics. We analyse the efficiency of excitation of the isomeric nuclear state 229mTh by the fifth harmonic of Ti: Sa laser generated in thorium by two-color femtosecond pulse consisting of the fundamental and thensecond harmonic of Ti: Sa laser (ω+2ω). It is shown that the rate of isomeric state excitation can be enhanced significantly with respect to other nucleus excitation processes in laser plasma or by an external coherent source at the resonance wavelength. This enhancement is due to the discussing process of “nonlinear laser nuclear excitation”.

The effect of a neutrino magnetic moment on nuclear excitation processes

1991 ◽  
Vol 266 (3-4) ◽  
pp. 434-438 ◽  
Author(s):  
A.C. Dodd ◽  
E. Papageorgiu ◽  
S. Ranfone
Keyword(s):  
Magnetic Moment ◽  
Nuclear Excitation ◽  
Neutrino Magnetic Moment ◽  
Excitation Processes

Valence electron energy loss spectroscopy in reflection geometry

1989 ◽  
Vol 47 ◽  
pp. 378-379
Author(s):  
J. Liu ◽  
J. M. Cowley
Keyword(s):  
Energy Loss ◽  
Valence Electron ◽  
Interband Transition ◽  
Specular Reflection ◽  
Three Dimensional ◽  
Electron Excitation ◽  
Transmission Electron ◽  
Yield Information ◽  
Valence Bands ◽  
Excitation Processes

The low energy loss region of a EELS spectrum carries information about the valence electron excitation processes (e.g., collective excitations for free electron like materials and interband transitions for insulators). The relative intensities and the positions of the interband transition energy loss peaks observed in EELS spectra are determined by the joint density of states (DOS) of the initial and final states of the excitation processes. Thus it is expected that EELS in reflection mode could yield information about the perturbation of the DOS of the conduction and valence bands of the bulk crystals caused by the termination of the three dimensional periodicity at the crystal surfaces. The experiments were performed in a Philipps 400T transmission electron microscope operated at 120 kV. The reflection EELS spectra were obtained by a Gatan 607 EELS spectrometer together with a Tracor data acquisition system and the resolution of the spectrometer was about 0.8 eV. All the reflection spectra are obtained from the specular reflection spots satisfying surface resonance conditions.

Plasma parameters in atomic-emission spectral analysis of phosphate concentrates of the fission products

2019 ◽  
Vol 85 (2) ◽  
pp. 17-22
Author(s):  
M. I. Khamdeev ◽  
E. A. Erin
Keyword(s):  
Spectral Analysis ◽  
Chemical Composition ◽  
Reference Materials ◽  
Fission Products ◽  
Atomic Emission ◽  
Electric Arc ◽  
Physical Parameters ◽  
Arc Plasma ◽  
Atomic Emission Spectral Analysis ◽  
Excitation Processes

Physical parameters of electric arc plasma as well as their time dependences are calculated when analyzing phosphate precipitates of the fission products of irradiated nuclear fuel. Phosphate concentrates of the fission products are known for their complex chemical composition and high thermal and chemical stability. Hence, direct atomic emission spectral analysis of phosphate powders without transferring them into solutions is advisable. Different conditions of sample preparation and synthesis of the reference materials determine the different chemical forms of the elements to be determined. This, in turn, affects the kinetics of their evaporation in the electrode crate and excitation processes in the plasma. The known mechanisms of those processes cannot always be transferred to specific conditions of the given method of analysis thus entailing the necessity of studying the effect of the samples chemical composition on the results of determination, proper choice of spectroscopic carriers, detailed study of spectra excitation processes in spectral analysis, and analysis of the physical parameters of the electric arc plasma. We used the lines Zn I 307.206 nm and Zn I 307.589 nm to measure the effective temperature of the central hot sections of the arc in a range of4500 - 6500 K. NaCl, BaCl2 and NaCl + T1C1 were studied to reduce the effect of the sample elemental composition on excitation conditions of the spectra and their stabilization as a spectroscopic carrier. In control experiments we used carrier-free samples. The coincidence of the values of the plasma physical parameters within the measurement error not exceeding 20%, as well as the identity of the nature of the kinetic curves for samples of phosphate precipitates and synthetic reference materials prove their correctness. The result of the study substantiate correctness of the direct atomic-emission spectral procedure in analysis of phosphate concentrates of fission when using synthetic reference materials.

scholarly journals PIC methods in astrophysics: simulations of relativistic jets and kinetic physics in astrophysical systems

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
Kenichi Nishikawa ◽  
Ioana Duţan ◽  
Christoph Köhn ◽  
Yosuke Mizuno
Keyword(s):  
Plasma Physics ◽  
Magnetic Reconnection ◽  
Laser Plasma ◽  
High Performance ◽  
Relativistic Jets ◽  
Astrophysical Plasmas ◽  
Computing Power ◽  
Particle In Cell ◽  
The Future ◽  
Pic Method

AbstractThe Particle-In-Cell (PIC) method has been developed by Oscar Buneman, Charles Birdsall, Roger W. Hockney, and John Dawson in the 1950s and, with the advances of computing power, has been further developed for several fields such as astrophysical, magnetospheric as well as solar plasmas and recently also for atmospheric and laser-plasma physics. Currently more than 15 semi-public PIC codes are available which we discuss in this review. Its applications have grown extensively with increasing computing power available on high performance computing facilities around the world. These systems allow the study of various topics of astrophysical plasmas, such as magnetic reconnection, pulsars and black hole magnetosphere, non-relativistic and relativistic shocks, relativistic jets, and laser-plasma physics. We review a plethora of astrophysical phenomena such as relativistic jets, instabilities, magnetic reconnection, pulsars, as well as PIC simulations of laser-plasma physics (until 2021) emphasizing the physics involved in the simulations. Finally, we give an outlook of the future simulations of jets associated to neutron stars, black holes and their merging and discuss the future of PIC simulations in the light of petascale and exascale computing.

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