A proposed new architecture for solid-state radiation detectors using a three-dimensional array of electrodes that penetrate into the detector bulk is described. Proposed fabrication steps are listed. Collection distances and calculated collection times are about one order of magnitude less than those of planar technology strip and pixel detectors with electrodes confined to the detector surface, and depletion voltages are about two orders of magnitude lower. Maximum substrate thickness, often an important consideration for X-ray and gamma-ray detection, is constrained by the electrode length rather than by material purity or depletion-depth limitations due to voltage breakdown. Maximum drift distance should no longer be a significant limitation for GaAs detectors fabricated with this technology, and collection times could be much less than one nanosecond. The ability of silicon detectors to operate in the presence of the severe bulk radiation damage expected at high-intensity colliders should also be greatly increased.

/pdf/3d-a-proposed-new-architecture-for-solid-state-radiation-464u5pqos7.pdf

3D — A proposed new architecture for solid-state radiation detectors

Motivated by technological advances in power electronics and signal processing, and by the interest in using direct drives for robot manipulators, we investigate the control problem of high-performance drives for switched reluctance motors (SRM's). SRM's are quite simple, low cost, and reliable motors as compared to the widely used dc motors. However, the SRM presents a coupled nonlinear multivariable control structure which calls for complex nonlinear control design in order to achieve high dynamic performances. We first develop a detailed nonlinear model which matches experimental data and establish an electronic commutation strategy. Then, on the basis of recent nonlinear control techniques, we design a state feedback control algorithm which compensates for all the nonlinearities and decouples the effect of stator phase currents in the torque production. The position dependent logic of the electronic commutator assigns control authority to one phase, which controls the motion, while the remaining phase currents are forced to decay to zero. Simulations for a direct drive, single link manipulator with the SRM are reported, which show the control performance of the algorithm we propose in nominal conditions and test its robustness versus the most critical parameter uncertainties of payload mass and stator resistance.

Feedback linearizing control of switched reluctance motors

Nanoscaled interdigitated electrode arrays were made with deep UV lithography. Electrode widths and spacings from 500 down to 250 nm were achieved on large active areas (0.5×1 mm). These electrodes allow for the detection of affinity binding of biomolecular structures (e.g. antigens, DNA) by impedimetric measurements. Such a sensor with Pd electrodes on SiO 2 is developed and theoretically analysed. It was experimentally characterised in KCl solutions demonstrating its bulk-insensitive behaviour and the immobilisation of glucose oxidase (GOD) could be monitored by measuring the double layer impedance.

Nanoscaled interdigitated electrode arrays for biochemical sensors

A new type of doubly salient machine is presented in which the field excitation is provided by a nonrotating permanent magnet (PM). This doubly salient PM (DSPM) motor is shown to be kindred to square waveform PM brushless DC motors. Linear and nonlinear analysis has been performed to investigate the characteristics of this new type of PM motors. A prototype DSPM motor has been designed, and a comparison has been made between this new type of motor and the induction motor. It is shown that, by fully exploiting modern high-energy PM material and the doubly salient structure, the DSPM motor can offer superior performance over existing motors in terms of efficiency, torque density, torque-to-current ratio, and torque-to-inertia ratio, while retaining a simple structure amenable to automatic manufacture. >

A novel permanent magnet motor with doubly salient structure

In this article we review the recent advances in iterative learning control (ILC) for nonlinear dynamic systems. In the research field of ILC, two categories of system nonlinearities are considered, namely, the global Lipschitz continuous (GLC) functions and local Lipschitz continuous (LLC) functions. ILC for GLC systems is widely studied and analysed using contraction mapping approach, and the focus of recent exploration moves to application problems, though a number of theoretical issues remain open. ILC for LLC systems is currently a hot area and the recent research focuses on ILC design and analysis by means of Lyapunov approach. The objectives of this article are to introduce recent development and advances in nonlinear ILC schemes, highlight their effectiveness and limitations, as well as discuss the directions for further exploration of nonlinear ILC.

A survey on iterative learning control for nonlinear systems

The paper explores the theory and potential of a family of doubly salient electronically-switched reluctance motors. It is demonstrated that the machine provides the basis for fully-controllable variable-speed systems, which are shown to be superior to conventional systems in many respects. The motor retains all the advantages normally associated with induction motors and brings significant economy in the drive electronics. The basic modes of operation, analysis, design considerations and experimental results from a range of prototype motors up to 15 kW at 750 rev/min are described. The most recent prototype has achieved a continuous rating which is 1.4 times that of the equivalent induction motor.

Variable-speed switched reluctance motors

Basic Field Theory. Images. The Solution of Laplace's Equation by Separation of the Variables. Fields with Distributed Currents: Poisson and Diffusion Equations. Conformal Transformation: Basic Ideas. Polygonal Boundaries. General Considerations. Computational Modeling--Basic Methods. Two-Dimensional Static Linear Problems. Non-Linear Effects in Two-Dimensional Fields. Two-Dimensional Time-Dependent Fields. Three-Dimensional Problems. Electromagnetic Software Environment. Appendices. Bibliography. Index.

The Analytical and Numerical Solution of Electric and Magnetic Fields

Analysis and computation of electric and magnetic field problems

A new type of reluctance machine is described in which, briefly, the radial poles of a conventional machine are replaced by circumferential segments. Working from the flux distribution in the air gap, general equations for the synchronous performance of reluctance machines are developed. These are used in a comparison of the new and conventional machines, and it is shown that the new machine has torque and power-factor characteristics which are superior to those of the conventional one.The air-gap flux distribution in the new machine exhibits unusual characteristics, and to discuss them precisely the ideas of m.m.f. have to be abandoned, those of magnetic potential being employed instead. Expressions are developed for the direct- and quadrature-axis reactances, and values computed from these are found to be in good agreement with values measured for a range of experimental machines.Though attention is devoted chiefly to fixed, normal-frequency operation, consideration is also given to machine performance under varying-frequency and direct-current conditions. In particular, it is shown that, under d.c. or low-frequency conditions, the output torque is directly proportional to the difference between the direct- and quadrature-axis reactances.Additionally a new method for the experimental determination of the axis reactances of salient-pole machines is described. This is based upon the theory of the impedance and current circle diagrams of reluctance machines which are also developed.

Theory and performance of polyphase reluctance machines

Switched reluctance (SR) drives offer the advantages of simple and robust motor construction, high speeds, high overall efficiencies over a wide operating range of torque and speed, simple power converter circuits with a reduced number of switches, and excellent controllability. The basis of these claims is explained. The history of the SR system, in particular the extensive research at Nottingham and Leeds Universities, and the basic operating principles and design considerations for motors and power converters are reviewed. Alternative configurations are discussed. The difficulties of establishing a simple mathematical model for the motor and of calculating torque and inverter VA requirements are examined. A comparison of the VA requirements for SR and pulsewidth modulation (PWM) is given for a 7.85-kW system. Measured drive performance is discussed in terms of efficiency over an operating envelope, specific output, controllability, and power converter ratings. Earlier traction drives, incorporating a constant power range and including regeneration, are reported together with the constant torque industrial drives and more recent traction extensions. The long-term potential of the drive is discussed for a wide range of applications. A comprehensive list of references is provided.

P.J. Lawrenson

Papers

Variable-speed switched reluctance motors

The Analytical and Numerical Solution of Electric and Magnetic Fields

Analysis and computation of electric and magnetic field problems

Theory and performance of polyphase reluctance machines

High-Performance Switched Reluctance Brushless Drives