Coulomb singularity effects in tunnelling spectroscopy of individual impurities

Non-equilibrium Coulomb effects in resonant tunnelling processes through deep impurity states are analyzed. It is shown that Coulomb vertex corrections to the tunnelling transfer amplitude lead to a power-law singularity in current- voltage characteristicsComment: 7 pages, 2 figure

СРЕДСТВА РЕГИСТРАЦИИ ИМПУЛЬСНОГО ВИДИМОГО ИЗЛУЧЕНИЯ МАЛОЙ ИНТЕНСИВНОСТИ. ЧАСТЬ 1. ОСОБЕННОСТИ И ВОЗМОЖНОСТИ МНОГОКАНАЛЬНЫХ ФОТОПРИЕМНИКОВ С ВНУТРЕННИМ УСИЛЕНИЕМ. ОБЗОР

The main types of the modern photo detectors applied to single photon registration are analyzed. It is offered to use silicon photomultipliers for production of multi-channel optoelectronic systems with the single photon resolution.Проанализированы основные типы современных фотоприемников, применяемых для регистрации импульсного оптического излучения видимой области спектра. Сделан вывод о том, что для создания многоканальных оптико-электронных систем с однофотонным разрешением целесообразно использовать кремниевые фотоэлектронные умножители

СРЕДСТВА РЕГИСТРАЦИИ ИМПУЛЬСНОГО ВИДИМОГО ИЗЛУЧЕНИЯ МАЛОЙ ИНТЕНСИВНОСТИ. Часть 2. ПРЕДВАРИТЕЛЬНАЯ ОБРАБОТКА СИГНАЛОВ КРЕМНИЕВЫХ ФОТОЭЛЕКТРОННЫХ УМНОЖИТЕЛЕЙ. ОБЗОР

Bias circuits, output signals and readout electronics of silicon photomultipliers are considered. Requirements to analog IC for SiPM signal preliminary processing are formulated. According to requirements the set of radiation hardened analog ICs including the comparator and transresistance amplifiers with different gain and speed is produced.Рассмотрены схемы включения, выходные сигналы и считывающая электроника кремниевых фотоэлектронных умножителей. Сформулированы требования к аналоговым устройствам для предварительной обработки их сигналов, в соответствии с которыми создана серия радиационно-стойких аналоговых микросхем, включающая компаратор напряжения и трансрезистивные усилители с разным коэффициентом преобразования и быстродействием

МАЛОШУМЯЩИЙ ЭЛЕКТРОННЫЙ МОДУЛЬ ОБРАБОТКИ СИГНАЛОВ ЛАВИННЫХ ФОТОДИОДОВ

Schematic and design of electronics module for avalanche photodiode signal′s readout based on the pair of specialized analog ICs, are considered. Main specifications including input noise charge vs signal source capacity are presented.Рассмотрен электронный модуль обработки сигналов лавинных фотодиодов, созданный на базе двух специализированных аналоговых микросхем. Приведены результаты измерений основных характеристик и уровня шумов электронного модуля в зависимости от емкости источника сигнала (фотодиода)

ОБЕСПЕЧЕНИЕ РАДИАЦИОННОЙ СТОЙКОСТИ АНАЛОГОВЫХ ИНТЕГРАЛЬНЫХ СХЕМ

Influence of gamma radiation Co60 on static and dynamic characteristics of the transresistance amplifier and the comparator realized on the master slice array «ABMK 1-3» is considered taking into account formulated design rule. At absorbed dose D = 5 Mrad the comparator input current has increased on 25 %, other IC parameters (gain, impulse response of the transresistance amplifier, propagation delay, transition time, output current of the comparator) have changed slightly.Рассмотрено влияние гамма-излучения Co60 на статические и динамические характеристики трансрезистивного усилителя и компаратора напряжения, реализованных на базовом матричном кристалле типа «АБМК 1-3» с учетом сформулированных правил проектирования радиационно-стойких аналоговых интегральных схем (ИС). При поглощенной дозе D = 5 Мрад входной ток компаратора возрос на 25%, остальные параметры ИС (коэффициент преобразования, длительность фронта нарастания и спада трансрезистивного усилителя, задержка переключения, длительность фронта нарастания и спада, выходной ток компаратора) изменились незначительно

Parquet solution for a flat Fermi surface

We study instabilities occurring in the electron system whose Fermi surface has flat regions on its opposite sides. Such a Fermi surface resembles Fermi surfaces of some high-$T_c$ superconductors. In the framework of the parquet approximation, we classify possible instabilities and derive renormalization-group equations that determine the evolution of corresponding susceptibilities with decreasing temperature. Numerical solutions of the parquet equations are found to be in qualitative agreement with a ladder approximation. For the repulsive Hubbard interaction, the antiferromagnetic (spin-density-wave) instability dominates, but when the Fermi surface is not perfectly flat, the $d$-wave superconducting instability takes over.Comment: REVTeX, 36 pages, 20 ps figures inserted via psfig. Submitted to Phys. Rev.

Parquet Graph Resummation Method for Vortex Liquids

We present in detail a nonperturbative method for vortex liquid systems. This method is based on the resummation of an infinite subset of Feynman diagrams, the so-called parquet graphs, contributing to the four-point vertex function of the Ginzburg-Landau model for a superconductor in a magnetic field. We derive a set of coupled integral equations, the parquet equations, governing the structure factor of the two-dimensional vortex liquid system with and without random impurities and the three-dimensional system in the absence of disorder. For the pure two-dimensional system, we simplify the parquet equations considerably and obtain one simple equation for the structure factor. In two dimensions, we solve the parquet equations numerically and find growing translational order characterized by a length scale $R_c$ as the temperature is lowered. The temperature dependence of $R_c$ is obtained in both pure and weakly disordered cases. The effect of disorder appears as a smooth decrease of $R_c$ as the strength of disorder increases.Comment: 15 pages, 12 PostScript figures, uses multicols.sty and epsf.st

Asymmetric and symmetric fission of excited nuclei of 180,190Hg and 184,192,202Pb formed in the reactions with 36Ar and 40,48Ca ions

Background: Observation of asymmetric fission of 180Hg has led to intensive theoretical and experimental studies of fission of neutron-deficient nuclei in the lead region. Purpose: The study of asymmetric and symmetric fission modes of 180,190Hg and 184,192,202Pb nuclei. Methods: Mass-energy distributions of fission fragments of 180,190Hg and 184Pb formed in the 36Ar+144,154Sm and 40Ca+144Sm reactions, respectively, at energies near the Coulomb barrier have been measured using the double-arm time-of-flight spectrometer CORSET and compared with previously measured 192,202Pb isotopes produced in the 48Ca+144,154Sm reactions. The mass distributions for 180,190Hg and 184,192,202Pb together with old data for 187Ir, 195Au, 198Hg, 201Tl, 205,207Bi, 210Po, and 213At [J. Nucl. Phys. 53, 1225 (1991)] have been decomposed into symmetric and asymmetric fission modes. The total kinetic-energy distributions for different fission fragment mass regions have been analyzed for 180,190Hg and 184Pb. Results: The stabilization role of proton numbers at Z≈36, 38, Z≈45, 46, and Z=28/50 in asymmetric fission of excited preactinide nuclei has been observed. The high (≈145−MeV) and the low (≈128−MeV) energy components have been found in the total kinetic-energy distributions of 180,190Hg fission fragments corresponding to the fragments with proton numbers near Z≈46 and Z≈36, respectively. In the case of fission of 184Pb only the low-energy component (≈135MeV) for the fragments with masses corresponding to the proton numbers Z≈36 and 46 has been found. Conclusions: The studied properties of asymmetric fission of 180,190Hg and 184,192,202Pb nuclei point out the existence of well deformed proton shell at Z≈36 and less deformed proton shell at Z≈46.peerReviewe