ALBERT

Notes: Contents An analysis has been made of the magnetic field in a permanent-magnet motor by applying the finite element method, using an adequate functional. The results obtained may be applied for analyzing the magnetic field in similar motors of a different design.

Notes: Contents A method of calculation of the current density impressed along a vertical earth electrode of finite length by drained d.c. and by d.c. leaving nearby a point earth electrode is presented. The integro-differential equation is formulated and a numerical method for the solution is derived.

Notes: Contents The paper describes a numerical method of calculating the transient electromagnetic field in magnetic circuits containing moving conducting parts. The procedure allows determining the field distribution if only the supply voltages are known. The equations of the converter's electro mechanical equilibrum have been taken into account. The procedure has been employed for an analysis of transient states in a fast-acting electromagnetic actuator.

Notes: Übersicht Viele Stromrichterantriebe werden mit Rücksicht auf den Stromrichteraufwand mit Feldschwächung betrieben.—Dies erfolgt bei dauermagneterregten Maschinen über die Ankerwicklung. Ströme mit entsprechendem zeitlichen Verlauf erzeugen in einer mehrphasigen Wicklung längsmagnetisierende Ankerstrombelagsabschnitte, die nach Größe und Vorzeichen verändert werden.—Die Wirksamkeit bezogen auf die erreichbare Aufwandsreduzierung ist bei höheren Feldstellbereichen und praxisnaher Maschinenausnutzung erheblich eingeschränkt; dabei ist der Einfluß der Ankerrückwirkung dominierend.

Notes: Contents Based on the sensitivity approach a new algorithm for optimal shape design has been presented in this paper. The Singular Value Decomposition (SVD) of the sensitivity matrix and the Least Distance Programming (LDP) [3] have been used in order to define a direction vector. —Two types of side constraints have been imposed to control the mathematical technique and to avoid undesirable shapes. — The algorithm is illustrated by its application to modify the magnetic pole contour so that a desired magnetic field distribution in the air gap is obtained.

Notes: Contents Interactive computational techniques for reliability evaluation of power systems including wind generating units are presented. The fluctuating nature of energy produced by wind generators has a different effect on the overall system reliability than conventional units. The overall power system is divided into a subsystem containing the conventional units and into several subsystems containing the wind generating units. For each of these subsystems a generation availability model is built and the obtained models are combined to evaluate the loss of load expectation index for the time period of study. The developed methodology is illustrated by the analysis of a system based on a real power distribution system existing in a Greek island. Although the paper concentrates on wind energy sources, the general configuration of the developed techniques is applicable to generation systems containing any type of intermittent sources such as solar energy sources.

Notes: Übersicht Der Aufsatz behandelt die Ausgleichsvorgänge in Antrieben mit Asynchronmaschinen mit Käfigläufer und drehelastisch gekuppelter Arbeitsmaschine beim Einschalten im Stillstand sowie beim dreipoligen und zweipoligen Klemmenkurzschluß der laufenden Maschine. Das Berechnungsverfahren für die unsymmetrischen Schaltungen wird vorgestellt im Hinblick auf die numerische Lösung der Gleichungssysteme. Für die Praxis wichtig sind insbesondere die Stoßmomente in den Wellensträngen. Die Ergebnisse der Rechnungen werden an zwei Beispielantrieben ausführlich erläutert. Es zeigt sich, daß der zweipolige Kurzschluß keineswegs immer den gefährlichsten Störungsfall darstellt.

Notes: Übersicht Ausgehend von einem Modell eines kornorientierten Silizium-Eisenbleches mit idealer Goss-Textur und einem in der Blechebene fehlorientierten Korn im Zentrum werden die Magnetisierung, die Struktur des inneren Feldes und die Flußdichte berechnet. Die Struktur des inneren Feldes und der Flußdichte wird in Abhängigkeit vom aussteuernden Feld dargestellt, so daß die Verschlechterung der Flußführung durch derartig fehlorientierte Körner sichtbar wird.

Notes: Contents The three-phase model and quadrature-phase slip-ring model for smooth-air-gap electrical machines are presented, if saturation of the main flux paths is considered. By utilizing space-vector theory, the impedance matrices for the two models are derived. A detailed analysis is performed and it is shown that due to saturation, anisotropy will arise, which leads to extra elements and coupling in both impedance matrices. Under linear magnetic conditions the newly developed equations lead to the well-known equations used in generalized electrical machine theory.

Notes: Übersicht Das Funktionsprinzip prädestiniert den FCTh (alias FTD, SITh) für das Schalten großer Ströme und Spannungen: FCThs leiten wie Dioden, werden durch Feldeffekt blockiert und benötigen nur zum Umschalten Ansteuerenergie. — Doch zwei grundlegende Innovationen waren zur Erschließung dieses Potentials erforderlich: Die Recessed-Gate-(Verigrid)-Technologie, damit Breite, Höhe, Dotierung und Kontaktierung der Steuerfinger der FCThs unabhängig voneinander optimiert werden können und eine extrem niederinduktive Ansteuerung zum schnellen und homogenen Ausschalten der FCThs.— So haben wir unter geringem technologischem Aufwand Bauelemente mit Eigenschaften realisiert, die den theoretischen Grenzen bipolarer Si-Schalter sehr nahe sind. Snubberfreie Schaltungen dürften damit auch in der höchsten Leistungsklasse in Kürze realisierbar sein.

Notes: Übersicht Für die Entwicklung einer optimalen Planar-passivierung von Halbleiterleistungsbauelementen mit Sperrspannungen von 1600 V wird ein Vergleich verschiedener Strukturen anhand zweidimensionaler numerischer Simulationen durchgeführt.

Notes: Übersicht Insbesondere für die Industrie- und Autoelektronik entwickelte Siemens die Smart SIPMOS-Technologie. Diese Technologie umfaßt SIPMOS-Transistoren und CMOS-Schaltungen für Spannungen bis 60V, monolithisch integrierbar auf einem Chip. Erste Smart SIPMOS-Bauelemente sind high side-Schalter für den Spannungsbereich 5 V bis 60 V.

Notes: Übersicht Vorgestellt werden neue abschaltbare Leistungshalbleiter (GTO, bipolare Transistoren, IGT, MOSFET, SIT und schnelle Dioden), die in den letzten Jahren die Leistungselektronik in allen Leistungsbereichen entscheidend verändert haben. Diskutiert werden das Schaltverhalten (Ein- und Ausschalten) und der sich daraus ergebende Frequenzbereich. PWM-Wechselrichter mit 20 kHz Pulsfrequenz mit verschiedenen Transistortypen werden verglichen: hier hat der IGT die besten Eigenschaften. Steuergeneratorschaltungen und Steuerleistungsbedarf werden angegeben. Für GTOs werden verlustarme Beschaltungen erörtert. Anwendungen und Entwicklungstrends werden aufgezeigt.

Notes: Übersicht Durch Protonenbestrahlung können Rekombinationszentren in Siliziumbauelementen in definierter Tiefe erzeugt werden. Dadurch ergibt sich ein neuer Freiheitsgrad für die Optimierung bipolarer Bauelemente. — Durch den Einsatz von Protonenbestrahlung können bei GTO-Thyristoren geringere Schaltverluste und bei Dioden günstigeres Kommutierungsverhalten erzielt werden. Falls die mit der Wasserstoffimplantation verbundene Bildung energetisch flacher Donatoren nicht zulässig ist, könnte stattdessen He-Bestrahlung eingesetzt werden.

Notes: Übersicht Für die Methode der Berechnung von Schaltungen der Leistungselektronik im Spektralbereich wird ein Verfahren angegeben, das zu standardisierten Systemgleichungen führt und allgemein angewendet werden kann. Das ist für Schaltungen mit vorgegebener Übersetzungsfunktion für die Ventilschaltung naheliegend. Es wird jedoch gezeigt, daß das Verfahren so erweitert werden kann, daß es sich auf alle Schaltungen der Leistungselektronik anwenden läßt. Die numerischen Eigenschaften der standardisierten Systemgleichungen, wie die Regularität, die Konvergenz und die Abbruchfehler werden auch angegeben. Die Anwendung des Verfahrens wird an einem einfachen Beispiel demonstriert.

Notes: Übersicht Für die Bestimmung der Diffusionslänge mit der Surface-Photo-Voltage (SPV)-Methode wurde ein Auswerteverfahren entwickelt, das den Einfluß der Probenstruktur und der effektiven Lichtabsorption auf das Ladungsträgerprofil berücksichtigt. Es wird gezeigt, daß sich mit diesem Verfahren bei hoher Meßgenauigkeit noch Diffusionslängen, die der Waferdicke entsprechen, mit einer Genauigkeit 〉25% auflösen lassen.

Notes: Übersicht Die Felderhöhung durch freie Ladungsträger und die dadurch ausgelöste Avalanche-Generation (dynamischer Avalanche) beim Abschalten von GTO-Thyristoren und IGBTs werden mit Hilfe eindimensionaler Simulationsrechnungen untersucht. Mit dem snubberlosen Schaltelement wird eine induktive Last geschaltet. Sowohl bei der üblichen GTO-Abschaltung als auch bei der GTO-Kaskodenabschaltung, die im inneren Funktionsablauf mit der IGBT-Abschaltung übereinstimmt, beträgt die Feldüberhöhung in den dargestellten Fällen 20 bis 30%. Dies führt zu einer Verkleinerung des sicheren Arbeitsbereichs und einer erheblichen Vergrößerung der Abschaltverluste für Strom-und Spannungswerte, die nicht weit von der SOA-Grenze entfernt liegen. Verglichen mit der Raumladung der Löcher, die sich aus deren Strom und Driftgeschwindigkeit ergibt, ist die dynamische Feldüberhöhung jedoch gering. Dies beruht auf einer weitgehenden Kompensation der Löcher in der Raumladungszone durch Elektronen, die nach Beendigung der Injektion aus demn-Emitter (bzw. dem Source) durch den dynamischen Avalanche generiert werden. Letzterer begrenzt und steuert sich auf diese Weise selbst. Der selbstkontrollierte dynamische Avalanche bestimmt weitgehend das Ausräumen der Ladungsträger und den Spannungsaufbau während der Speicherphase der GTO-Kaskodenund IGBT-Abschaltung.

Notes: Übersicht Der Wirkungsgrad einer Solarzelle aus kristallinem Silicium mitn + p-Struktur hängt im wesentlichen von der effektiven Diffusionslänge der Minoritätsladungsträger in der Basis und im Emitter, von der Rekombination in der Raumladungszone und von der effektiven Oberflächen-rekombinationsgeschwindigkeit ab. Es werden die Optimierungsmöglichkeiten dieser Gebiete aufgrund der unterschiedlichen Rekombinationseigenschaften diskutiert. Daraus resultiert ein Vorschlag für eine optimale Solarzellenstruktur.

Notes: Contents Open-circuit voltage decay (OCVD) of many monocrystalline silicon solar cells after IR optical and electrical excitation (PIVD) has been measured. From the slopes of the decay the lifetime and volume diffusion length of minority carriers have been extracted, making allowance for the geometry of the devices, especially for the thickness of the base region. The procedure uses model curves which have been obtained by solving the differential equation for diffusion of minority carriers for a cartesian 3-dimensional geometry of the samples. More realistic circuit model evaluations of the stored charge of minority carriers yield a second time constant besides minority carrier lifetime, apparent in the voltage decay and excitation dependent. Good agreement has been achieved for differently extracted diffusion length, thus confirming the validity of this approach.

Notes: Contents A method for the solution of initial-boundary-value problems of the wave equation with moving boundary conditions is presented, which transforms the wave equation for the region with moving boundary into a form-invariant wave equation for a region with fixed boundary. Two kinds of transformations are found which refer to regions (1) expanding and (2) contracting with (increasing) time. As an application, the compression of microwaves in a one-dimensional cavity 0≦x≦s(t) with fixed liner atx=0 and an inward moving liner atx=s(t) is treated analytically. It is shown that large amounts of microwave energy can be generated in the final compression stages(t)→0 with the help of a copper liner driven by explosives ( $$\left| {(\dot s(t)} \right| 〉 10^3 m/s$$ ), for times of the order of the electromagnetic diffusion time,τ D =μσd 2∼10-2s. Such microwave compressions proceed quasi-statically for non-relativistic liner velocities, $$\left| {\dot s(t)} \right| \ll c$$ .

Notes: Contents In this paper, the analysis of the commutation processes and design of the forced commutation circuit is presented for the PAM inverter with having one LC-commutation circuit only and new pulse amplitude modulation control technique are described for this inverter, which eliminate the stator current harmonics of an order lower than 17th. Based on this principle resulting in a higher stability of the machine operation in the dynamic regime.

Notes: Übersicht In der Hochspannungsmeßtechnik treten bei der Sprungantwortmessung von räumlich ausgedehnten Spannungsteilern Signalverzerrungen auf, die von der elektromagnetischen Kopplung der Teilersäule mit der Zuleitung und dem Impulsgenerator herrühren. Nach einer kurzen Übersicht über bestehende Verfahren zur Berechnung transienter elektromagnetischer Felder wird ein dreidimensionales Zeitbereichsmodell zur Nachbildung von Meßkreisen der Hochspannungstechnik vorgestellt, der Transiente Elementar Dipol TED. Als Anwendungsbeispiele werden die Berechnung des elektromagnetischen Feldes in Sprungantwortmeßkreisen, sowie die Simulation von Sprungantwortmessungen unter Berücksichtigung des transienten Strahlungsfeldes vorgestellt.

Notes: Contents General three-dimensional solutions are given for the Laplace equation and Helmholtz equation in the cylindrical co-ordinate system, for processes which remain harmonic with time. The expressions for solution which are presented, not only for the magnetic and electrical field variables, but also for the higher-order vector potential, permit an analytical solution. The interrelationships between the field variables, the vector potential, and the higher-order vector potential are discussed. Several examples of engineering applications of the analytical calculation method are given.

Notes: Übersicht Teil 1 befaßte sich mit der mathematischen Modellbildung der 2×3strängigen Synchronmaschine mit Massivläufer. Im Teil 2 wird gezeigt, wie der 12pulsige Wechselrichter nachgebildet werden kann, und wie insbesondere das Problem der Kopplung der Teilsysteme mathematisch und programmtechnisch zu lösen ist. Ein abschließender Vergleich von Meßergebnissen mit den Ergebnissen einer Simulationsrechnung zeigt eine gute Übereinstimmung. Es ist somit möglich, die bei der Stromrichterspeisung im Rotor der Synchronmaschine auftretende elektrische Wirbelströmung bei der digitalen Simulation des transienten Betriebsverhaltens zu berücksichtigen.

Notes: Übersicht Feldberechnungen bei nur stückweise homogenem Medium verlangen die Erfüllung komplizierter Feldlinienbrechungsgesetze an den Mediengrenzen. Die hier vorgeschlagene Methode löst das Problem durch Zurückführung auf viel einfachere Dirichlet- und Neumann-Randbedingungen. Dabei muß die Mediengrenze keine spezielle Form haben, so daß allgemeine Aufgaben einbezogen sind. Es werden auch die Gemeinsamkeiten und die vorzunehmenden Modifikationen erklärt, die notwendig werden, wenn statt elektrischer Felder Magnetfelder von Strömen oder Stromdichtefelder zu berechnen sind.

Notes: Übersicht Für den rotationssymmetrischen Fall werden das Magnetfeld und die magnetische Energie zweier koaxialer, mehrlagiger Zylinderspulen, welche konzentrisch um einen zylindrischen Eisenkern angeordnet und von Gleichstrom durchflossen sind, berechnet. Für den Sonderfall, daß die sekundäre Wicklung aus einer Windung besteht und axialsymmetrisch zur Induktorspule angeordnet ist, folgt aus der magnetischen Energie die Streuinduktivität von Induktionsrinnenöfen.

Notes: Contents A new high performance reactive power compensator with inductive store is proposed, which permit to obtain reactive currents with reduced content in high harmonics by addopting a 12-pulse compensation scheme. This converter presents te advantage of a simpler turning-off circuits of the main thyristors, as compared to the version presented in the former work.

Notes: Contents Calculation of the eddy-currents which occur in the grooved surfaces of turbogenerators generally leads to the problem of calculating the eddy-currents in coupled cylindrical shells. The theory can be built up and formulated by starting with the important special practical case in which the fields and currents have reached a steady-state condition.

Notes: Contents The paper presents methods of determining the parameters of induction machine models in objective, algorithmic way employing the stepwise-regression method. The experimental base for parameter-estimation are measured slip-curves of the machine. At first a singular estimation method is presented, which uses one slip-curve as the source for determining the parameters. Then multidimensional estimation methods are introduced, which take several slip-curves into account and result in one versatile set of parameters. The methods are quite general, but in this paper specific formulae are given for double-cage machines. The paper is concluded with examples of application to double-cage and deep-bar motors, and the obtained parameters are used in computations of typical transients which are compared with recorded curves.

Notes: Übersicht In der vorliegenden Arbeit werden die Auswirkungen von Steuerungsunsymmetrien auf den stationären Klemmenstrom sechspulsiger Thyristorbrücken mit der Theorie der symmetrischen Komponenten rechnerisch verfolgt. Analytische Gleichungen zur Bestimmung der Steuerungsunsymmetrie aus gemessenen Irregularitäten des Klemmenstromes werden angegeben. Des weiteren wird eine Symmetrierungsregelung HGÜ-gespeister Netze geringer Kurzschlußleistung entwickelt, die mit minimalen Zündwinkeländerungen des Wechselrichters auskommt.

Notes: Übersicht Die Eisensättigung bewirkt bei Synchronmaschinen eine magnetische Kopplung zwischen den Flußpfaden der Längs- und der Querachse. Anhand einer Reluktanzmaschine wird diese Kopplung mit der Hilfe numerischer Feldberechnung untersucht. Der Vergleich mit Meßergebnissen zeigt, daß nur mit Berücksichtigung der magnetischen Kopplung bei hohen Sättigungen brauchbare Berechnungsergebnisse erhalten werden können.

Notes: Contents In this paper an analytic method of study the dispersion characteristics of an open thick microstrip is presented. By the help of the hertzian vector it was found the integral equation for the current distribution and the transmission coefficient. From the numerical results it is shown that the attenuation constant due to the conductor loss is less in the rounded edge microstrip than in the rectangular one. For the current distribution the transverse current was at least ten times less the longitudinal one. So to study an open thick microstrip we have good approximation by using only the longitudinal current.

Notes: Contents The Boundary Element Method (BEM) designed in special way is employed in conjunction with the Finite Element Method (FEM) to calculate the magnetic field of an induction motor at no-load. The B−H characteristic of the motor laminations is taken into account.

Notes: Übersicht Es wird zunächst das magnetische Skalarpotential einer räumlichen Leiterschleife in elliptischen Zylinderkoordinaten durch Entwicklung nach MATHIEUschen Funktionen angegeben. Unter der Voraussetzung großer Eindringtiefen im Vergleich zur Dicke des Bandleiters können die induzierten Wirbelströme durch die skalare Stromfunktion beschrieben werden, für deren Lösungskoeffizienten unendliche lineare Gleichungssysteme aufgestellt und numerisch ausgewertet werden. Am Beispiel einer einfachen Leiterschleifenanordnung wird die Stromdichte im Bandleiter sowie der Verlauf der Stromlinien zu verschiedenen Zeitpunkten grafisch dargestellt.

Notes: Contents A simplified model of the gap-field of a linear induction machine is presented; the model lends itself to analysis within the framework of the Einstein-Minkowski lectrodynamics.

Notes: Contents The paper deals with a new method for the synthesis of two-dimensional magnetic fields. The proposed algorithm makes it possible to determine the optimal structure of constant-current areas by generation of the required magnetic field distribution. The main idea of this algorithm is based on the application of a modified gradient method for solving the overdetermined, nonlinear system of algebraic equations obtained by the finite element method. Numerical calculations performed in examples demonstrate the application of the proposed method for the synthesis of the uniform magnetic field.

Notes: Contents A simple method to digitally produce a sine wave-form with constant amplitude over a relatively wide band of frequencies is described. The method is based on the generation of a number of samples per cycle of the sine wave-form, using an up/down counter and a decoder, and then processing these samples in a summing amplifier and in a controlled-gain amplifier to produce a staircase approximation of the sinewave. The total harmonic distortion of the resulting waveform can be reduced substantially by inserting a low-pass filter.

Notes: Contents A procedure, based on the “Extended Sign Test Method”, is given to classify the constraints of an optimisation problem as either redundant or nonredundant. A series of LP problems is solved; for each problem the slack of a particular constraint is minimised with respect to the feasible region. With the aid of several theorems the intermediate tableaux are scanned for the identification of redundant and nonredundant constraints. The algorithm is demonstrated by applying it to the optimal power flow of a simple testsystem.

Notes: Contents The paper describes an analytical three-dimensional method which allows the determination of the propulsion force produced by air core long stator linear synchronous motors in EDS-MAGLEV transport systems, using super-conducting coils both for motor field winding and for vehicle levitation. The method, which allows to take into account the finite thickness of the coils, is based on the variation of the magnetic energy stored in the field and armature (over-lapped or non-overlapped) windings of the motor. The application of the method to an experimental Japanese prototype gives good concordance with the experimental data.

Notes: Contents The paper deals with the determination of the earthing impedance of a cylindrical electrode modelling an earthing system of a transmission tower. Assuming a soil of two layers, the effect of the eddy currents in the soil is investigated with the conductivity and the thickness of the layers varied. The solution of the Helmholtz equation given for the magnetic field intensity is obtained by a global variation method. The satisfaction of Dirichlet boundary conditions on the surface of earth and along thez-axis as well as of the continuity conditions on the interface of the layers is ensured with the aid ofR-functions.

Notes: Contents The voltage regulator and the excitation system are known to affect strongly the dynamic stability of a synchronous generator. This effect is often detrimental, sometimes leading even to dynamic instability. This paper concentrates on determining the excitation system parameter values for which the generator's dynamic stability becomes marginal. This defines a stable and an unstable region in the space of the dominant excitation system parameters, namely the transient or the steady state gain and the dominant time constant of the excitor-voltage regulator system. In the case of a first order excitation system model, the stability limits can be determined analytically in the form of an inequality constraint. A fourth order excitation system is also examined but this time the stability limits are computed using the concept of the gain margin. The determination of the stable region in the parameter space is an extremely useful tool for the proper selection of excitation system parameter settings.

Notes: Übersicht Die Behandlung der Beungung am zylindrischen Hohlspiegel (vgl. auch Sommerfeld [4]) bietet die Möglichkeit, das generell bei Zwei- oder Mehrraumproblemen auftretende “Problem der relativen Konvergenz” [1–3] analytisch zu untersuchen. Zur Lösung dieses Randwertproblems werden für die tangentialen Feldgrößen auf dem Spiegel Orthogonalansätze gemacht, die für den Fall des Vollzylinders auf die klassische Lösung führen. Die numerische Auswertung umfaßt Strom- und Fernfeldverläufe; insbesondere wird das Verhalten der Flächenstromdichte an der Kante untersucht.

Notes: Contents A conceptually simple, but general theory is proposed to explain the behaviour of aY-connected squirrel cage induction machine operating in steady state. Means for accounting for slot openings and saturation are discussed. The analysis provides an insight into how harmonics due to both magnetomotive force distribution and saturation contribute to losses. An expression for torque is derived, together with an algorithm for solution. Finally, results obtained are compared with those found on an actual machine.

Notes: Übersicht Die elektrische Kapazität eines Elektrofilters ist wegen ihrer Rückwirkung auf Impulsspannungsversorgungen, ihrer Gläuttungswirkung bei welligen Gleichspannungsversorgungen, sowie ihres Einflusses auf den Energieumsatz bei Überschlägen ein wichtiges Kriterium für die Aufteilung großer Filter in einzelne Sektionen. Mit digitalen Rechenprogrammen lassen sich zwar Kapazitäten für jeden Einzelfall berechnen, allgemeine Aussagen über den Einfluß verschiedener Parameter erfordern jedoch zahlreiche Parameterstudien. Dieser Beitrag verdeutlicht im ersten Teil die Problematik der Kapazitätsberechnung in Elektrofiltern am Beispiel paralleler Drähte. Im zweiten Teil wird eine analytische Näherung vorgestellt, die den Einfluß der unterschiedlichen Parameter wie Gassenabstand, Drahtradius und Sprühdrahtabstand zu berücksichtigen gestattet.

Notes: Contents A numerical method for computation of flux and loss distribution in transformer cores is described. Special attention has been given to the investigation of the influence of leg and yoke joint-gap connections on the distribution of losses. In comparison with results of measurements on models, numerical computation of the distribution of losses provides results that are quite accurate, provided that the magnetic characteristic of the joint-gap has been correctly taken into account.

Notes: Contents The paper presents a method of calculation of the switched reluctance motor torque on the basis of the calculated electromagnetic field distribution while the difference method in integral technique has been employed. The analysis of the electromagnetic field distribution has been performed for the model motor, with the effect of magnetic nonlinearity of the medium taken into account. The obtained SR motor torque curves gives evidence of the torque as a function of the rotor position.

Notes: Übersicht Aus einem vergleichenden Überblick über die wesentlichen Streufeldquellen eines M-Schnitt-Bleches aus kornorientiertem Silizium-Eisen folgt, daß nur das Luftspaltfeld einen merklichen Anteil zur Streufeldkopplung liefern kann. Der Einfluß dieses Luftspalt-Streufeldes auf die Magnetisierungsstruktur und den Ummagnetisierungsvorgang in einer benachbarten Blechlage wird untersucht. Aus einer Diskussion der abschirmenden Wirkung des benachbarten Bleches in Abhängigkeit von der Aussteuerung folgen Aussagen über den Einfluß der Streufeldkopplung auf die Energieverluste und den Wirkungsgrad des kompletten Transformatorkernes aus mehreren Blechlagen und Vorschläge zur Verbesserung des Wirkungsgrades bei der Spannungswandlung.

Notes: Übersicht Komplexe Größen haben sich für die Beschreibung von gewissen physikalisch-technischen Zusammenhängen in der Elektrotechnik als besonders nützlich erwiesen. Der gemeinsame mathematische Formalismus verleitet jedoch zur Mißachtung der inhaltlichen Unterschiede in den einzelnen Anwendungsgebieten und zur Einführung von zahlreichen unzutreffenden Bezeichnungen. Es wird nun der Versuch gemacht, die einzelnen Anwendungsmöglichkeiten der komplexen Größen physikalisch zu definieren und mit entsprechenden Namen zu versehen.

Notes: Übersicht Die Zusatzverluste von asynchronen Käfigläufermotoren können durch Vergrößerung der Luftspaltweite beträchtlich vermindert werden. Es wird ein Berechnungsverfahren zur Bestimmung der luftspaltabhängigen Verluste vorgestellt. Die Ergebnisse wurden durch Messungen an drei verschiedenen Motoren im Leistungsbereich zwischen 10 und 50 kW überprüft. Bei Betrieb mit erhöhter Ständerfrequenz wird eine Reduzierung der Gesamtverluste um bis zu 32% erzielt. Dies gilt bei Betrieb der Motoren mit sinusförmiger Spannung. Bei Speisung über Frequenzumrichter mit nichtsinusförmigen Ausgangsgrößen reduzieren sich die Gesamtverluste um den gleichen absoluten Betrag.

Notes: Contents A method for synthesis of antenna arrays with a given number of sidelobes and sidelobe levels is discussed. The pattern is given as a multiplication of a Chebyshev polynomial of nth degree with the one of first degree. The radiation pattern of a wire antenna in a form similar to that of an array with point sources is also given by the method of moments. So the synthesis procedure can be reduced. Several examples show the applicability of the method.

Notes: Contents A practical 8th-order single-input multiple-output (SIMO) time-invariant linear model of a synchronous machine with first order conventional exciter, supplying power to the power system through a transformer and a transmission line has been developed. The criterion for the effective contribution of each system state to the total energy response at the output is used to obtain an adequate reduced 4th-order model in which the most important states and eigenvalues of the original model are retained. An efficient algebraic pole—placement method, using output feedback has been used to design the 8th and 4th-order models, physically realisable linear excitation controllers (with easily measurable state variables) for the purpose of substantially enhancing the dynamic stability characteristics and voltage control of a synchronous machine. The controller designed for the 4th-order model has also been tested on the 8th order model to demonstrate the validity of implementing reduced order formulations without degrading the performance of the control. A procedure for implementing the control strategies is presented in this study, and attention is drawn to the wider implications of implementing practical designs on large turbogenerators currently in use.

Notes: Contents The analysis of thermal field and stresses field in the slot part of the bar of an induction motor in the course of starting have been presented in the paper. The changes of the bar parameters resulting from the temperature changes and the heat flow from the bar into the surroundings have been considered. The finite element method has been used in the calculations.

Notes: A unique apparatus is described for generating submicron particles of metals over a narrow-size distribution range. Coarse particles of the metal were injected into the tail flame of an argon rf-induction plasma torch, where they were vaporized. The vapor was gas quenched, producing a metallic smoke of fine spheroidal particles. The system collection units separated the fine particles (∼0.3-μm diameter) from the heavier particles (≥1-μm diameter) while the material was finely dispersed and moving in the gas stream.

Notes: Fast infrared scanning technique (FIRST), in which a laser beam focused to a line is used for heating and the temperature rise is detected with an IR scanner, is applied to the nondestructive inspection of plasma-sprayed coatings. The surface temperature profiles are computed numerically for faultless and defective coatings, and the functionality of the technique is demonstrated using a sample with artificial defects.

Notes: Synchrotron radiation obtained from the 6-T vertical-wiggler source at the Photon Factory has been used to study dynamical x-ray diffraction in a nearly perfect germanium crystal under total external reflection conditions. A specially designed goniometer has allowed independent control of the glancing angle and the deviation angle from exact Bragg incidence. The rocking-curve profiles observed from slightly asymmetric Bragg planes as a function of glancing angle were found to be quite different for both the diffracted and specular beams. These profiles show unusual features arising from the excitation or de-excitation of the wave fields in shallow surface layers of the bulk crystal. Furthermore, GeK fluorescence signals measured during the Bragg reflection showed characteristic modulations, demonstrating the feasibility of new standing-wave experiments for determination of interface structures.

Notes: The new powder diffractometer installed on the beamline B2 at HASYLAB/DESY is described. It features a new design with a blocked double circle plus a third single circle which can be translated towards one another. The wide space between the two circle units conveniently holds complicated and spacious attachments and makes the instrument especially suitable for measurements under controlled environment conditions.

Notes: X-ray powder diffraction measurements using synchrotron radiation are currently being carried out on three experimental stations on the SRS at Daresbury Laboratory. Station 9.1 contains a general purpose powder diffractometer for angular dispersive measurements. The instrument is sited on the wiggler beamline, which provides radiation with a critical energy of 12 keV. A Si(111) water-cooled, channel-cut monochromator gives useful flux over an energy range from 6 to 30 keV. A cryostat and furnace are available for experiments requiring special environments, while a curved position sensitive detector can be used for time-resolved measurements. The wiggler white beam is employed on Station 9.7 for energy dispersive powder diffraction experiments. Various sample stages for kinetic experiments are in use on this station, and examples are shown of recent high-pressure work. A new high resolution powder diffractometer has been built and commissioned on Station 8.3, using bending magnet radiation. The diffractometer is based on the Parrish and Hart design, in which long, parallel foils are used to define the angular divergence accepted by the detector. In this way, large synchrotron beam cross sections can be employed while maintaining high angular resolution.

Notes: A new powder diffractometer for the Photon Factory was designed and constructed in 1986. Its performance has been confirmed as follows: (1) it is capable of determining the wavelength of the Cu K edge as 1.380619±0.000012 A using NBS standard Si powder 640b, while the reported one is 1.38059 A; (2) the accuracy of monitoring the incident beam intensity was ±0.2%, which was estimated by the normalized integrated intensity; (3) the angle resolution of diffraction lines was comparable with that of SSRL; and (4) the sum of three Gaussians was the best profile function fitted for lines from NBS standard Si powder 640b.

Notes: A beamline (BL 6A) for x-ray crystallography mainly utilizing photographic methods was designed and constructed at the Photon Factory. A focusing mirror was installed at the beamline in order to obtain a beam with high photon flux while eliminating higher energy x rays in the beam. The mirror chamber located at 11.8 m from the source point is maintained in a high vacuum so as to keep the mirror surface clean. It accommodates a 1.3-m-long steel holder on which a mirror block is mounted. Two types of mirror blocks, plane and cylindrical ones of fused quartz, are prepared for alternative use. A radiation shielding hutch placed at around 15 m from the source is sufficiently large for installing a monochromator and various types of cameras. When the plane mirror was bent vertically, the size of the focused beam at 15.3 m was reduced to about 0.18 mm in the vertical direction. By the use of focused x rays, preliminary Laue diffraction experiments were carried out on protein crystals. Good quality diffraction patterns recorded on imaging plates were obtained by exposure of several milliseconds.

Notes: A triple-axis spectrometer for high-energy ((approximately-greater-than)150 keV) synchrotron radiation has been constructed and characterized. The reciprocal space resolution function of this instrument has been measured using perfect silicon crystals as monochromator, sample, and analyzer. It was found to have dimensions of 1.0×10−5 A(ring)−1 and 2.3×10−4 A(ring)−1 in the directions perpendicular and parallel to the momentum transfer Q, respectively, comparable to those achievable using standard 8-keV triple-axis instruments. The large penetration depths of high-energy x-ray photons, combined with the high instrumental resolution, opens new possibilities in the study of truly bulk condensed matter systems.

Notes: A system for a very high precision absolute lattice spacing measurement has been developed. It employs, in principle, a bond method using a highly collimated and a very narrow bandwidth beam available from a monolithic (+, +) monochromator. Owing to the temperature stabilization of the hutch, where the equipment is installed, it has routinely achieved a precision of 2 parts in 106 in lattice spacing measurements.

Notes: It has been an earnest desire of protein crystallographers to collect fast, accurate, high resolution diffraction data from protein crystals, preferably with exposure time as short as possible. In order to meet this challenge, a new type of Weissenberg camera has been developed for the recording of diffraction intensity from protein crystals using synchrotron radiation. The BL6A2 line has a plane-bending mirror designed by Y. Sato. The optical bench with triangular tilt-cut Si crystal monochromator was designed by N. Kamiya and was installed in the BL6A2 hutch. The Weissenberg camera was set on the 2θ arm of the optical bench. This camera can be used with Fuji Imaging Plate (IP) as an x-ray detector, and the reading out of the image from the IP is carried out by using BA100. The characterization of this system was carried out using the native crystal of chicken gizzard G-actin DNase I complex and its Yb3+, PCMB, indium, and FMA derivatives. Since these crystals are very sensitive for x rays, the resolution limit of the diffraction was 5 A(ring) with a 4-circle diffractometer on a rotating anode x-ray generator (N. Sakabe et al., J. Biochem. 95, 887. This complex was crystallized in space group P2,2,2, with a=42.0, b=225.3, and c=77.4 A(ring). The data were collected with this system with the 430-mm radius cassette when Photon Factory was operated at 2.5 GeV and 270 mA and the wavelength λ=1.004 A(ring) was chosen. In order to avoid overlapping of diffraction spots, oscillation angle range and coupling constant (degree/mm) were settled on the basis of simulation patterns of diffraction spots up to the maximum resolution to be measured considering the direction of the crystal axes, wavelength, radius of the camera, and mosaicness of the crystal. When the oscillation axis was a axis, the oscillation angle range was selected at either 10° (1°/mm) or 5° (0.5°/mm) depending on the density of reciprocal lattice points along the incident beam, and typical exposure time in each IP was 50 and 25 s, respectively. The exposure was stopped after 10 times oscillation. The total range of 117.5° was recorded on 16 sheets of IP with an overlapping range 0.5°.The data processing was carried out using program weis coded by T. Higashi. Two complete data sets along the a and c axes were collected using two crystals, independently, and the merge R(F2) for native crystal was 0.068. In order to know the feasibility of the data (F+−F−), Patterson maps were calculated with data of each derivative, and heavy atom vectors clearly appeared as prominent peaks in the Harker sections of the Patterson maps of both Yb3+ and PCMB derivatives. The heavy atom positions were obtained from the combinations of different Patterson and different Fourier maps, and were refined by using least-squares techniques. The final figure of merit up to 2.5 A(ring) resolution was 0.61 with 22 700 reflections. The assignment of DNase I part on the electron density maps is progressing using the Nicholson molecular model referring to its structure reported by C. Oefner and D. Suck [J. Mol. Biol. 192, 605 (1986)]. In addition to promising results of ω-aminoacid pyruvate aminotransferase [N. Watanabe et al., Book of abstracts of second Japan-China Bilateral Symposium on Biophysics, p. 83 (1988)], these results support that this data collection system consisting of a new type of Weissenberg camera using SR, Fuji Imaging Plate, BA100, and program weis is one of the fastest and most accurate systems for protein crystallography in use today. We thank the Education Ministry and the Foundations of Yamada, Naito and Toray for the financial support of this project. We are grateful to Dr. K. Namba of ERATO for our use of BA100.

Notes: Results are given concerning the two-dimensional scanning microanalysis of microsections of metallographic specimens of rocks. The monochromatized or white SR beam from a wiggler magnet installed at the electron storage ring VEPP-3 (2 GeV, 20 kG, 100–200 mA) was used for fluorescence excitation. The working energies ranged from 8 to 35 keV. Without focusing x-ray optics, the spatial resolution was 60 μm with the monochromatic beam and 30 μm with the white SR beam. The minimum detectable concentration of the elements (within the Fe-Sr region) is 10 ppm for 1–3 s exposures per point.

Notes: A set of highly bent crystal monochromators made from formed pyrolytic graphite has been tested using synchrotron-radiation beams from the storage ring VEPP-3. These crystals were used in the following devices: short-focus wide-band monochromator and cylindrical dispersion filter of secondary (fluorescent) radiation.

Notes: A scanning transmission x-ray microscope has been used to form images with 380-eV x rays on the undulator beamline at the Daresbury synchrotron radiation source. A resolution of 80 nm has been achieved using Fresnel zone-plate focusing optics and images with reasonable signal-to-noise ratios can be acquired in less than 30 min.

Notes: This article describes a high-resolution three-dimensional CT system which has been tested on the new wiggler beamline X-2 at the Stanford Synchrotron Radiation Laboratory. The present system is a rotate-only design which uses a virtual phase CCD array camera optically coupled to a high-resolution phosphor screen. The spatial resolution of this system is presently somewhat better than 10 μm (50 line pairs/mm at 20% contrast). This resolution is limited by the optical elements in the detector, and we are undertaking an effort to improve this resolution to 1 μm. Nevertheless, the spatial resolution offered by this design is sufficient to begin many studies of interest to materials research, such as, supported catalysts, composite materials, and crack growth and propagation.

Notes: Employing asymmetric Bragg reflection at the monochromator we obtain a wide and practically parallel synchrotron-radiation beam which, when combined with the use of a CCD detector, enables us to perform chemically specific, high-speed and high-resolution tomography. We present recent results obtained with this new method. The actual resolution achieved was determined from the measured line-spread function of the complete detection system which includes the CCD, the fluorescent screen, and the lens used for optical magnification. The modulation-transfer function (MTF) calculated from the line-spread function shows that with only twofold magnification and at 3% contrast detectability about 28 line pairs per mm are resolved. Extrapolating from this result we find that with an optical magnification of 7:1 about 100 line pairs per mm should be resolved. Ways to optimize the method further are discussed.

Notes: Recent developments of a high-precision diffractometer for multiple crystal arrangement at the Photon Factory is described. New x-ray optics for topography using this diffractometer are shown, including plane-wave topography, ultraplane wave topography and equilattice-spacing mapping topography.

Notes: In many cases the fluorescence EXAFS signal is contaminated with fluorescence from nearby elements. If this fluorescence is of lower energy than the element of interest, x-ray filters are not effective. One method for dealing with this problem is the double fluorescence method described by Wong and Rao. This paper describes an improved version of this double fluorescence scheme that greatly improves its efficiency. Data are presented for a sample of 1/2% Hf in Ni3 Al, and 1.6% CuO in NiO. When standard fluorescence is used, both signals are almost completely obscured by the (approximately-equal-to)100× larger Ni K fluorescence signal. With the double fluorescence detector the Hf L3 and Cu K-edge signals are clearly observed, and good spectra can be obtained in about an hour.

Notes: An absorption spectrum containing both the XANES and the EXAFS region can be recorded in several seconds if x-ray monochromators at synchrotron beamlines are scanned continuously. The experimental setups are described in detail. The accuracy of the method up to photon energies of 19 keV is demonstrated. Due to its advantages, the proposed approach may be used as an alternative to the energy dispersive EXAFS method, especially in the case of XANES spectroscopy.

Notes: A versatile instrument for glancing-angle x-ray absorption spectroscopy (XAS) and x-ray reflectivity in routine use on the Daresbury Synchrotron Radiation Source is described. This facility can be used for XAS measurements in both reflectivity and fluorescence modes as well as for qualitative studies of angular dependent x-ray reflectivity. Reflectivity and XAS data obtained with this instrument on the oxidized surfaces of Cu thin films are presented.

Notes: An erbium laser (λ=1.5 μm) with a pulse energy of 2 J delivered in 2 ms was used for rapid heating to investigate the kinetics and structural mechanism of the thermotropic phase transitions of a phospholipid/water system by fast x-ray small-angle powder diffraction. The phase transitions were induced by a single laser pulse, leading to a T jump of about 10 °C and the structural relaxations following the T jump were detected in 1-ms resolution. The results show that the transition at 29 °C (Lβ-Lα) is at least as fast as the heating time (2 ms) and that the lamellar/hexagonal transition around 57 °C (Lα-HII) is considerably slower with a half-time of the order of 100 ms.

Notes: Luminescence excitation spectra in barium fluorohalides have been studied using synchrotron radiation of the SIBERIA-I electron storage ring in the energy range from 4 to 35 eV. The energy position of edge and core exciton formation as well as that of the electronic excitation multiplication threshold have been established. These luminophors find their practical application in the novel image-plate technique.

Notes: Fluorescence detection is often used to obtain the extended x-ray absorption fine structure (EXAFS) of dilute samples and thin films. As the samples become concentrated and the films become thick, significant errors can be introduced in the EXAFS amplitudes. With detailed calculations we determine the reduction in the coordination numbers (N) and the deviation in the mean-squared relative displacements (σ2) as determined by fluorescence detection. Experimental results on Cu, Ni, Fe, and Nb samples support the predictions of the calculation. We suggest corrections to obtain the correct coordination numbers and σ2 values for studies of concentrated samples by fluorescence EXAFS detection when other methods are not feasible.

Notes: We report the development of a novel radio frequency electron-spin-resonance spectrometer designed to provide measurements with high molar sensitivity and resolution in vivo. Radio frequency (250 MHz) is chosen to obtain good penetration in animal tissue and large aqueous samples with modest sacrifice of sensitivity. The spectrometer has a lumped component resonator and operates in continuous-wave mode. The spectrometer is capable of two-dimensional imaging, and with a modest addition should be capable of three-dimensional imaging. We demonstrate 3-mm spatial resolution for DPPH samples. For 10-ml samples of aqueous nitroxide, we demonstrate sensitivity (normalized to spectral width of 1 G) to 3×10−8-M concentrations and spectral resolution of 0.1 G. Spectra from nitroxide spin label injected into a live mouse are shown.

Notes: A new class of focusing, condensing, and collimating devices for x rays, γ rays, and neutrons is described which is based on the use of microchannel plates (MCPs) or configurations of holes. As well as providing a simple collimating action due to the absorption of severely divergent rays in the channel walls, the microchannel-plate-type structures are capable of providing a focusing and collimating action arising from the reflection of near-grazing-incidence rays at the channel walls. The focusing action is in principle controllable by mechanical bending or slump forming of the channel plates or by appropriate shaping of the channel walls and is remarkably insensitive to source location, device alignment, and wavelength. Theoretical predictions for the performance of such devices are presented via both simple model calculations and Monte Carlo simulations. These suggest that some simple scaling relations hold between key parameters, and provide a guide to the optimum performance levels achievable with such devices for a wide range of geometries. Some experimental observations of the focusing action of MCPs for 0.071-nm x rays are presented. A wide variety of x-ray and neutron optical applications is possible.

Notes: Multilayer mirrors have been designed, fabricated and tested for use as a wavelength-selective filter of ∼100 eV for photo-CVD experiments at the beamline 12C of Photon Factory, KEK. Mo/Si and Rh/Si multilayers were selected in accordance with new simple optical criteria and fabricated on super-polished CVD-SiC substrates by means of ion-beam sputtering. Both mirrors showed a reflectance of over 40% at around the designed angle of incidence of 45°.

Notes: We have designed and built a high-efficiency time-of-flight electron spectrometer which has the potential to record accurately the angular distribution of the photoemitted electrons. This analyzer uses an electrostatic analog of an optical parabolic mirror to collimate, in an isochronic fashion, half of the electrons emitted from an isotropic point source and measure each electron's energy by time-of-flight. Results are presented which demonstrate that the spectrometer operates near its design collection efficiency and energy resolution.

Notes: A spectrometer designed to study electrons which are scattered at 180° with respect to the direction of the incident beam from a gas or a solid surface target, has been constructed and tested. The instrument is capable of operating at very low impact energies (0.05–15 eV) with an absolute energy resolution of 18 meV full width at half-maximum (FWHM). The performance of this apparatus is demonstrated with vibrational energy-loss spectra of H2O and C6H6 molecules condensed on a polycrystalline platinum substrate held near a temperature of 80 K.

Notes: This article presents a new structure of monopole field on the basis of the method for obtaining ideal quadrupole fields within closed boundaries to which is applied a continuously varied potential with position. Further optimum design is made according to a large number of computations of boundary potentials by using the finite element method, and three sets of structures, termed as A-1, B-1, and B-2 type, respectively, are proposed. The agreement of the results obtained by a field-plotting method with those of the analysis is satisfactory.

Notes: The design of a new sample cell for a large-scale secondary ion mass spectrometer is described. Unique to this new source chamber is the incorporation of large piezoelectric translator stages capable of 20 cm×20 cm movement with high resolution. In addition, the source chamber is designed so that interchangeable detector assemblies can be fitted to the chamber.

Notes: Supersonic free jet expansions are often used to produce beams of cold molecules and clusters. They are an essential part of laser vaporization cluster sources, where small particles of a material are seeded within a helium carrier gas during the expansion. These sources accelerate the clusters to the thermal velocity of the helium gas used in the generation process. By tilting the acceleration grids in a time-of-flight spectrometer, the initial velocities of molecular clusters transverse to the flight path can be selectively reduced to zero, allowing for a less off-axis flight path and permitting detection of higher mass clusters than is possible with conventional post-acceleration deflection schemes. Mass-resolved spectra of ions larger than 27 000 amu have been obtained using this scheme.

Notes: A simplified homodyne small-angle scattering technique for plasma fluctuation measurements is described. The local oscillator is produced by a beam splitter which lies just behind the scattering area in the main laser beam. The scattered radiation is reflected from the beam splitter and directed onto the detector. Meanwhile, the transmitted portion of the beam is reflected back to the same beam splitter and superimposed with the scattered light so as to act as a local oscillator. The proposed method has several advantages. No separate local oscillator path is necessary, and the alignment and selection of different scattering angles is easily done by two microprocessor-controlled step motors. With a variable attenuator the local oscillator power is adjustable to any desired value. Heterodyning is possible by adding an acousto-optic modulator which shifts the LO frequency. First results of measurements on microturbulences in a plasma are presented.

Notes: A frequency-stabilized single-mode cw 118.8-μm CH3OH waveguide laser was newly developed for polari-interferometry on the JT-60 tokamak. Interferometric plasma diagnostics on large fusion devices requires a mode purity of a source laser for the long-distance propagation and frequency stability to obtain an adequate fringe resolution. The accomplished performances are Δf/f〈1×10−8, power stability 〈0.03%, and single EH11 mode to yield a Gaussian-shaped profile in the far field. Homogeneous pumping of laser media with a Ge étalon beam coupler and feedback stability control are the keys to the source far-infrared laser performances required for large tokamak diagnostics. The developed laser was totally adjustment free for more than 2 weeks and reliably in operation for 2 years, including the real-time electron density feed-back control on the JT-60 tokamak.

Notes: We describe an image-processing equipment designed and built to meet the specific requirements of an astrophysical experiment, but having probably useful applications in other fields of science and technology. It locates and makes the inventory of specified micrometer-sized holes in thin metallic films. The data acquisition is made by a CCD camera looking at the film through an optical microscope. The information goes to a microcomputer through a special interface. The program and the electronics were designed for optimum acquisition speed, automatic operation, and minimum need for human intervention.

Notes: We report on the response of three scientific charge-coupled devices (CCD), the RCA SID501, the Tektronix TK512M, and the Texas Instruments 4849, to direct electron bombardment. A scanning electron microscope is used to provide a temporally gated, focused electron source of precise energy and current. Both the detection efficiency and the line-spread response of the CCDs have been measured at incident electron energies in the range of 0.3–30 keV. Simple models for the detection process are discussed.

Notes: We have evaluated the performance of the first RANICON to be processed with a GaAs photocathode. We discuss the design characteristics of this prototype detector and present experimental results showing an overall detector resolution of 76 μm FWHM, yielding a value for VR , the radial emission energy of a photoelectron, of 0.09 eV for the GaAs photocathode. On the basis of these figures, we discuss techniques for optimizing and improving the spatial resolution of GaAs-photocathode RANICONs.

Notes: Single photon avalanche diodes (SPADs) are avalanche photodiodes specifically designed for reverse bias operation above the breakdown voltage and used for detecting single optical photons. A new silicon epitaxial device structure was designed to give improved timing performance with respect to previous SPADs. Extensive tests were carried out in order to establish the timing resolution of the device in time correlated photon counting (TCPC). The timing resolution of the SPAD in terms of its full-width at half-maximum (FWHM) contribution to the overall instrumental response width is 20 ps with the detector cooled to −65 °C, and 28 ps at room temperature. This is the highest resolution so far reported for solid-state single-photon detectors. In vacuum tubes, comparable results are obtained only with special microchannel-plate photomultipliers (MCP-PMT). Results from time-resolved photoluminescence measurements in GaAs demonstrate the power of the TCPC technique when used with the new SPAD detector. With the excellent timing resolution of the SPAD and the well-known advantages of TCPC systems (high sensitivity, linearity, etc.), various applications are foreseen in areas so far dominated by streak cameras.

Notes: The speed of torsional stress waves transmitted in solid waveguides submerged in a liquid depends, among other things, on the liquid's density and viscosity and the waveguides' cross-sectional geometry. By measuring the speed of torsional stress waves in two waveguides of different cross-sectional geometries, one can obtain both the liquid's density and viscosity. An on-line, real-time sensor for the simultaneous measurement of density and viscosity is described. The article details the sensor's principles of operation and reports experimental results conducted using viscosity standard calibration liquids with well-known thermophysical properties. For fluids with density ρf 〉1×103 kg/m3, it is estimated that the instrument can measure density with a precision better than 0.5%. For fluids with the product shear viscosity (μ) and density, ρfμ〉100 kg2/(m4 s), it can measure the shear viscosity with a precision better than 1%.

Notes: A new high-resolution ac calorimetric technique is described for measuring the absolute heat capacity of extremely small samples. The method uses a thermocouple as the weak link to the bath and modulates the temperature of the bath sinusoidally in time. This eliminates the need for a separate thermometer and heater on the sample while retaining the ability to make absolute measurements with minimal addenda. Results for a 2.9 μg sample of the superconductor Ba0.6K0.4BiO3 in a magnetic field of 60 kOe show a jump at Tc=21 K, which is above the noise level of ∼2 parts in 104.

Notes: A high-sensitivity high-spatial-resolution eddy-current apparatus has been set up for contactless conductivity measurements on Si and HgCdTe. The inductive sensitivity limit has been demonstrated, on Si slices, to a very low σt (product of conductivity and thickness) of 0.0004 Ω−1 and the spatial resolution was shown to be about 4 mm, both a threefold improvement over past published results. HgCdTe bulk slices and epitaxial films have been measured over a wide range of σt from 0.001 to 1 Ω−1 at 77 K. The conductivity mapping measurements on HgCdTe material were also demonstrated for the first time. The sensitivity of eddy-current probes consisting of miniature commercial rf coils were shown to be not only temperature independent, but also very stable after repeated thermal cyclings between 300 and 77 K. This feature makes the eddy-current method an ideal technique for routine contactless conductivity measurements on HgCdTe material at 77 K. We also show that both the sensitivity and the spatial resolution of eddy-current probes can be explained quantitatively by a simple theory which treats coils as magnetic dipoles.

Notes: An apparatus has been constructed for determining the integrated cavity emissivity of blackbody furnace simulators near 500 K and for calibrating infrared detectors. A difference-ratio method is described for measuring the radiant emission characteristics of the simulator by using a high-quality heat-pipe blackbody as a standard radiant source operated at 500 K and a water-immersed cavity as a reference source operated at a lower temperature. It is verified that the total uncertainties of the method are less than 0.6% for determining the integrated cavity emissivity and 0.5% for determining irradiance from the 500-K standard blackbody on the detectors.

Notes: Multiparticle coincidence events in the scattering volume of the forward-scattering spectrometer probe (FSSP) cause the instrument to bias the measurement of the particle size distribution of atmospheric aerosols toward large diameters. We employ a probabilistic model based on Poisson statistics to determine the average diameter and rms width of the actual size distribution as functions of the average diameter and rms width of the measured distribution. We compare our predictions to a Monte Carlo simulation of the FSSP operation

Notes: A correction factor to the number density measured by the Forward Scattering Spectrometer Probe (FSSP) which compensates for dead time and coincidence errors was determined by calculating the probabilities of and the average number of particles in the six possible types of dead time and coincidence events. These probabilities and averages were calculated by means of a probabilistic model based on Poisson statistics. A Monte Carlo computer simulation of the FSSP operation was also carried out and the number density correction factor was compared with the Monte Carlo data. For an actual number density of 2000/cm3, it was found that the measured number density was of the order of 300/cm3.

Notes: An electrically heated wire-mesh apparatus for pyrolysis studies has been developed which uses computer-driven feedback control for the heating system and thus can apply virtually any time-temperature history to the sample. Internal components are water cooled to prevent heat buildup during long runs. Using this system, coal pyrolysis has been studied at heating rates from 0.1 to about 5000 K/s and temperatures up to 1000 °C. Alternating current is used for heating; this allows the thermocouples to be attached directly to the sample holder and also makes power regulation relatively simple. For atmospheric-pressure experiments, a gas sweep can be forced through the sample holder to remove products from the heated zone and also to concentrate them in a trap which can be removed from the apparatus and weighed to establish tar yields directly. Although the design is optimized for atmospheric-pressure operation, relatively simple modifications allow operation under vacuum or at pressures of up to 160 bars in inert gas or hydrogen. The apparatus has been used to investigate a number of phenomena in coal pyrolysis and, most significantly, has demonstrated the existence of a heating-rate effect which is independent of reactor geometry.

Notes: The design of a sample transfer device for ultrahigh vacuum experiments is presented. In this device, the mobile sample holder has a wedge shape and can be attached to its place using a magnetic rod without delicate alignment. This device operates from close to nitrogen temperature to a temperature on the order of 700–800 °C.

Notes: We report how an induction cooker for household use can be modified for heating substrate or heating gases to high temperature in a chemical vapor deposition system. Only minor changes of the cooker are necessary. Stable substrate temperature as high as 900 °C was achieved with input power of about 1150 W.

Notes: An ultrahigh-vacuum apparatus is described that enables the study of molecular adsorbates on well-defined single crystals at controlled temperatures from 14 to 900 K. Sample cooling is achieved with a closed-cycle helium refrigerator coupled to the sample holder via a flexible copper cable. This configuration maintains a 3-K temperature differential from the 11-K cryocold head to the sample and damps vibrations from the cyrocold head. The cyrogenic sample manipulator allows X, Y, Z translations, tilt, and rotation of an arm holding the sample through an arc of 270° about the vertical central axis of the vacuum chamber. The sample, mounted 12.7 cm from the central axis, may also be rotated 90° about a vertical axis through the sample. Rotation of the sample about a working circle radius of 12.7 cm allows the sample to be accessed for surface cleaning, characterization, and study by instrumentation whose physical size does not allow access by sample rotation about the chamber central axis alone. In our application, unenhanced surface Raman spectroscopy, low-energy electron diffraction, and Auger spectroscopy are carried out while maintaining a controlled sample temperature. Laser entry ports at two incident angles permit the sutdy of substrates with differing optical properties. Unenhanced surface Raman spectra of nitrogen physisorbed on a silver (111) surface are presented.

Notes: A reactive ion-beam deposition (RIBD) and cleaning (RIBC) system using low-temperature crystalline film growth and substrate cleaning is described. The RIBD and RIBC methods use low-energy-controlled ionized species produced from electron-cyclotron-resonance (ECR) plasma of reactive gases. The basic system comprises an ECR-type ion source allowing precise energy control of ionized species in the region of less than 500 eV and a high-vacuum cleaning and growth chamber evacuated at less than 3×10−7 Pa. Employing this system, Si substrate cleaning and high-crystalline-quality homoepitaxial film growth with superstructures on the substrates can be reliably performed at the low temperature of 650 °C.