To obtain a harder energy spectrum and increase the photon flux and brightness of synchrotron radiation of the Synchrotron Radiation Facility—Siberian Circular Photon Source “SKlF” synchrotron light ...source, it is planned to use multipole superconducting insertion devices—radiation generators (wigglers and undulators). Having a short period and large amplitude of the magnetic field, such devices have a serious impact on the optics and dynamics of the electron beam. In the proposed work, we consider various aspects of this influence (changes in radiation parameters, distortion of optical functions, and a reduction in dynamic aperture) and discuss possible options for correcting the undesirable consequences of installing wigglers and undulators in the SKIF storage ring.
Photosensitive memristor structures based on graphene oxide reduced under hydrothermal conditions are studied. The wavelength of light absorption in such structures was controlled by carbon ...nanoparticles deposited on the surface of a graphene oxide film. The obtained structures exhibited photomemristive states that were controlled by light of different wavelengths and bias voltages.
Using the MADX options, the stages of orbit correction and then optics correction were simulated, taking into account the specified tolerances for the positioning of magnetic elements and girders in ...the Siberian Circular Photon Source (SKIF, the Russian acronym). Numerical modeling of hte effect of residual perturbations of the guide field on the vertical emittance and vertical size of the beam has been carried out. A generalized method of skew-quadrupole coupling correction in SKIF has been developed and verified by simulation, which allows simulteneously minimizing the vertical dispersion and compensating for the linear difference coupling resonance.
The methods of high-frequency electron paramagnetic resonance (EPR), electron spin echo (ESE) and optically detected magnetic resonance (ODMR) are used to study the unique properties of ...nitrogen-vacancy (NV) defects in diamond in strong magnetic fields. It is shown that in strong magnetic fields (∼3–5 T) there occurs an effective optically induced alignment of populations of spin levels resulting in filling the level
M
S
= 0 and emptying of the levels
M
S
= ±1, that makes it possible to record ODMR using the change in the intensity of photoluminescence which reaches 10% at resonance. It is demonstrated that the efficiency of the alignment has the same order as in zero and low magnetic fields. The samples were preliminary studied by the ODMR method in zero magnetic fields that allowed accurate determination of the main parameters of the fine structure and hyperfine interactions with nitrogen nuclei, as well as dipole-dipole interactions between the NV center and deep nitrogen donors in the form of a nitrogen atom replacing carbon, N
0
. Hyperfine interactions with the nearest carbon atoms (isotope
13
C) were observed in the high-frequency ODMR spectra, that opens up opportunities for measuring the processes of dynamic polarization of carbon nuclei in strong magnetic fields using optical methods. It is assumed that narrow ODMR lines in strong magnetic fields can be used to measure these fields with submicron spatial resolution. A new method for recording ODMR of NV centers with microwave frequency modulation has been developed, which simplifies the technique of measuring high magnetic fields. A significant increase in the intensity of the ODMR signal was demonstrated when a strong magnetic field was oriented along the symmetry axis of the NV center.
We propose an experiment to search for a new gauge boson A' in e+e− annihilation by means of a positron beam incident on a gas hydrogen target internal to the bypass at the VEPP-3 storage ring. The ...search method is based on a missing mass spectrum in the reaction e+e−→γA'. It allows observation of the A' signal independently of its decay modes and life time. The projected result of this experiment corresponds to an upper limit on the square of the coupling constant ϵ2=3ċ10−8 with a signal-to-noise ratio of two to one at an A' mass of 5–20 MeV .
In yttrium aluminum garnet (YAG) crystals containing terbium and cerium impurities, along with the main EPR signals of Tb
3+
and Се
3+
ions located in the dodecahedral sites of the YAG lattice in a ...regular environment, EPR lines with a lower (several percent) intensity were observed. They also belong to the paramagnetic centers of terbium and cerium, but are characterized by slightly altered parameters—the initial level splitting for non-Kramers Tb
3+
ions and g-factors for Се
3+
ions. It is shown that the nature of such centers and their number can be explained by the presence of Y
Al
antisite defects, i.e. yttrium ions in the octahedral aluminum positions, in the environment of Tb
3+
and Се
3+
.
Electron paramagnetic resonance (EPR) spectra of Ce
3+
, Yb
3+
, Cr
3+
, and Gd
3+
impurity ions in yttrium aluminum garnet Y
3
Al
5
O
12
(YAG) ceramics were detected and identified at frequency of ...94 GHz. The advantage of measuring the EPR spectra in the high-frequency range compared to the standard EPR technique is shown, which makes it possible to separate the EPR spectra characterized by different anisotropic
g
-factors and also to isolate the EPR signals due to the splitting of the fine structure for centers with high-spin states. In ceramics with a high content of magnetic Gd
3+
ions, EPR and electron spin echo (ESE) spectra of multi-ionic gadolinium complexes were observed, and EPR spectra of complexes with the maximum number of exchange-coupled gadolinium ions are seen at low temperatures. The temperature dependences of the EPR spectra indicates ferromagnetic ordering of exchange-coupled complexes of gadolinium.
The work is aimed at solving the problem of creating in laboratory conditions hypersonic high-enthalpy gas flows that parameters are kept constant for 5-10 seconds. For this purpose the test section ...of the MHD channel with water-cooled electrodes and side walls was under investigation at the set up with a magnetohydrodynamic accelerator in TsAGI. A new series of runs was performed in which the MHD-acceleration stage was successively increased to 5 seconds. It was determined that the electrical and gas-dynamic characteristics of the MHD accelerator did not depend on the duration of the run. It was first demonstrated that the use of a magnetic field special shaped along the axis of the channel made it possible to avoid catastrophic damage to the side walls of the channel at the entrance and exit of the MHD accelerator, which increased the service life of the installation.
The behavior of carbon in reactions of the synthesis of mixed nitrides of uranium and plutonium is determined not only by its excess content against stoichiometry, but also by the active influence of ...hydrogen and nitrogen as components of technological gas. It is also necessary to account for the impact of products of thermolysis of the binder. The results of a thermodynamic analysis of possible reactions during synthesis indicate the special behavior of phase UC
1.91
in the process and bring up additional questions on the mechanism of removal of excess carbon under temperatures of synthesis.
Pulsed electron paramagnetic resonance (EPR) and pulsed electron‐nuclear double resonance (ENDOR) techniques have been applied to study the environment of luminescent Ce3+ ions in garnet based ...scintillator powders and ceramics. The presence of aluminum and gallium isotopes with large nuclear magnetic and quadrupole moments in the nearest neighborhood of the Ce3+ ion allows for the use of the hyperfine and quadrupole interactions with these ions for determination of the unpaired electron spatial distribution and the definition of the electric field gradient at the aluminum and gallium sites. Pulsed EPR and ENDOR techniques made it possible to study the coherent properties of the Ce3+ spin system in garnet powders and ceramics, which is important for spin manipulation on Ce3+ centers.
PDF
