Regularization of the boundary-value problem for Sturm-Liouville equations with operator-valued coefficients

A regularization method is used to find an approximate solution to the inhomogeneous boundary-value problem –y(t)+Ay(t)=y(t)+h(t), t [0, b], cos CY–sin CY= where A is a self- adjoint unbounded operator on a Hilbert space H; C is an operator on H H; H H; h(t) L ₂ (H, (0, b)); Y, Y are regularizing boundary values of y (t).Translated fromVychislitel'naya i Prikladnaya Matematika, No. 69, pp. 23–28, 1989.     

Nature of radiation resistance of LFS oxyorthosilicate crystals doped with Ce,Sc, Ca,and Y ions

Optical and luminescence characteristics of Lu_2+2ySi_1-yO_5+y (LFS) scintillation crystals are studied before and after irradiation with doses to 45 Mrad from a ⁶⁰Co source. LFS crystals were doped with Ce³⁺, Sc³⁺, Ca²⁺, and Y³⁺ ions with various concentrations. The dependence of the radiation resistance of LFS crystals on Ce ion concentration is detected. For the crystal of composition Ce:Sc:Ca:Y:LFS, it was found that its optical transmission (OT) and pulsed cathodoluminescence (PCL) spectra before irradiation do not differ from the spectra measured after irradiation with a dose of 45 Mrad within experimental error. The nature of the radiation resistance of rare-earth lutetium oxyorthosilicates (LFS) is discussed.     

New radiation resistant scintillator LFS-3 for electromagnetic calorimeters

The results of the study of optical and luminescence characteristics of new LFS-3 heavy scintillation crystals are presented. Advantages of these crystals in comparison with conventional scintillators are discussed. The radiation resistance of LFS-3 scintillation crystals is studied using an intense ⁶⁰Co radioactive source and a proton beam with an energy of 155 MeV. No changes in the optical transmission of LFS-3 crystals after their irradiation with a dose of 23 Mrad are detected.     

EPR Spectroscopy of Impurity Thulium Ions in Yttrium Orthosilicate Single Crystals

The frequency-field and orientation dependences of the electron paramagnetic resonance (EPR) spectra are measured for impurity Tm³⁺ ions in yttrium orthosilicate (Y₂SiO₅) single crystals by stationary EPR spectroscopy in the frequency range of 50–100 GHz at 4.2 K. The position of the impurity ion in the crystal lattice and its magnetic characteristics are determined. The temperature dependences of the spin–lattice and phase relaxation times are measured by pulse EPR methods in the temperature range of 5–15 K and the high efficiency of the direct single-phonon mechanism of spin–lattice relaxation is established. This greatly shortens the spin–lattice relaxation time at low temperatures and makes impurity Tm³⁺ ions in Y₂SiO₅ a promising basis for the implementation of high-speed quantum memory based on rare-earth ions in dielectric crystals.     

Growth and Study of Scintillation Properties of Orthovanadate Crystals Ca:GdVO<Subscript>4</Subscript> and Ca:YVO<Subscript>4</Subscript>

New scintillation orthovanadate crystals Ca:GdVO₄ and Ca:YVO₄ featuring intrinsic luminescence are grown. The spectra of pulsed cathodoluminescence of new scintillators and their luminescence decay time are studied. Using γ-rays with an energy of 662 keV from the ¹³⁷Cs source, total absorption spectra (so-called photopeaks) for new orthovanadate crystals are measured. It is shown that the light yield of Ca:YVO₄ and Ca:GdVO₄ crystals is 28100 photon/MeV and 14000 photon/MeV, respectively.     

Collapse and Revival of the Electron Spin Echo of Impurity Yb3+ Ions on Hidden Frequency Combs of Hyperfine Interactions in a Y2SiO5 Single Crystal

JETP Letters - The collapse and revival of Hahn electron spin echo signals excited on electron–nuclear spin levels of an impurity 173Yb3+ ion in yttrium orthosilicate Y2SiO5 have been...