Application of Moments Method to Dynamics of Muon Cooling System

This report talks about Application of Moments Method to Dynamics of Muon Cooling Syste

Transfer matrix for a high energy cooling system

A transfer matrix for a high-energy electron cooling system, which describes the linear incoherent effects, is derived. Knowing this matrix we can treat an electron cooling section in the ring as an additional focusing element deforming the beam optic functions due to space charge forces This matrix can be implemented in different codes (MAD, MIRKO, SixTrack et al.) for precise calculation of the beam optic and dynamic aperture in storage rings, where a high energy electron cooling system is planed to install. As an example, an optic of the high-energy storage ring [6] calculated by MAD code with derived matrix is given.Виводиться матриця переходу для високоенергетичної системи електронного охолодження, яка описує лiнiйнi некогерентнi ефекти. Така матриця дозволяє розглядати секцію електронного охолодження у кiльцi, як додатковий фокусуючий елемент, який спотворює оптичнi функцii внаслiдок сил просторового заряду. Отримана матриця може використовуватися у рiзних програмах (MAD, MIRKO, SixTrac та iнших) для проведення прецизiйних розрахункiв оптики пучка та динамiчної апертури нагромаджувальних кiлець, де планується планується установка высокоенергетичних систем электронного охлаждения. Як приклад наведено розрахунок оптики високоенергетичного нагромаджувального кiльця [6], виконаний за допомогою програми MAD та виведеної матрицi.Выводится матрица перехода для высокоэнергетической системы электронного охлаждения, которая описывает линейные некогерентные эффекты. Такая матрица позволяет рассматривать секцию электронного охлаждения в кольце, как дополнительный фокусирующий элемент, искажающий оптические функции вследствие сил пространственного заряда. Полученная матрица может использоваться в различных программах (MAD, MIRKO, SixTrac и др.) для проведения прецизионных расчетов оптики пучка и динамической апертуры в накопительных кольцах, где планируется установка высокоэнергетических систем электронного охлаждения. В качестве примера приведен расчет оптики высокоэнергетического накопительного кольца [6], выполненный с помощью программы MAD и выведенной матрицы

Properties of silicon dioxide layers with embedded metal nanocrystals produced by oxidation of Si:Me mixture

A two-dimensional layers of metal (Me) nanocrystals embedded in SiO2 were produced by pulsed laser deposition of uniformly mixed Si:Me film followed by its furnace oxidation and rapid thermal annealing. The kinetics of the film oxidation and the structural properties of the prepared samples were investigated by Rutherford backscattering spectrometry, and transmission electron microscopy, respectively. The electrical properties of the selected SiO2:Me nanocomposite films were evaluated by measuring C-V and I-V characteristics on a metal-oxide-semiconductor stack. It is found that Me segregation induced by Si:Me mixture oxidation results in the formation of a high density of Me and silicide nanocrystals in thin film SiO2 matrix. Strong evidence of oxidation temperature as well as impurity type effect on the charge storage in crystalline Me-nanodot layer is demonstrated by the hysteresis behavior of the high-frequency C-V curves

Radiationless intermolecular energy transfer with participation of acceptor excited triplet states

Radiationless energy transfer between like and unlike molecules has been experimentally studied under conditions where acceptor molecules have been excited to the triplet state. Homogeneous singlet—triplet—triplet migration has been discovered in higbly concentrated chlorophyll “a” and pheophytin “a” solutions in castor oil at 183 K by measuring the variation of pigment relative quantum yields of fluorescence and triplet state formation as a function of exciting pulse intensity. Heterogeneous singlet—triplet—triplet energy transfer has been observed in solid solutions of different complex organic molecules (perylene +phenanthrene, Na-fluorescein +chlorophyll “a”, pyrene+ Mg-phthalocyanine) as the fluorescent donor state quenching in the presence of acceptor triplet-excited molecules. Primary emphasis is placed on a direct observation of the effect of energy transfer on the excited-state lifetime of the donor. The benzophenone phosphorescence quenching (shortening of phosphorescence lifetime) in the presence of Mg-mesoporphyrin triplet molecules has been found to be caused by the heterogeneous triplet—triplet—triplet energy transfer. Good agreement of the theoretical and experimental results permits us to conclude that all types of observed transfer processes are described by the Förster—Galanin theory for dipole—dipole radiationless energy transfer with no additional assumptions

Influence of Single Dye Molecules on Temperature and Time Dependent Optical Properties of CdSe/ZnS Quantum Dots: Ensemble and Single Nanoassembly Detection

Optical spectroscopy on ensembles and single CdSe/ZnS semiconductor quantum dots (QDs) demonstrates a competition of trap and near band edge photoluminescence (PL). This competition can be markedly influenced by a few surface attached pyridyl functionalized dye molecules (porphyrins or perylene diimides) forming nanoassemblies with well defined geometries. Temperature variation and related changes in absorption and emission reveal sharp changes of the ligand shell structure in a narrow temperature range for organic (TOPO and amine) surfactants (phase transition). The effects on QD PL at this transition become considerably pronounced upon attachment of only a few dye molecules to QD surface. Moreover, under ambient conditions amine capped QDs are photodegraded in the course of time. This process is enhanced by attached dye molecules both on the ensemble and single particle/dye level. This investigation elaborates the importance of (switchable) surface states for the characterization of the PL of QDs. © 2012 Elsevier B.V. All rights reserved