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We present results from a numerical solution of a resonant tunneling diode structure, using a time‐independent Schrodinger equation without considering scattering. Intrinsic circuit parameters such as conductance, capacitance, and inductance are extracted from the numerical results and compared with experimental data obtained from dc and microwave characterization of GaAs/AlGaAs devices. A study of the influence of different lightly doped spacer layer thicknesses on the emitter side reveals the relationship between spacer layer thickness and the circuit parameters. From these results, we provide explanations for the behavior of the biased diode circuit parameters. The simulated data show good qualitative agreement with experimental results; possible explanations for deviations between experimental values and simulated data, including inelastic scattering and series resistance effects, are discussed.

The theory of bipolar pulse conductivity detection has been successfully applied to the pressure‐jump (P‐jump) method of relaxation kinetics. This method has distinct advantages over ac bridge detection, including the elimination of capacitance effects which make current balancing significantly easier, the ability to study low‐conductance solutions at higher signal‐to‐noise ratio, and reduction of power input into the cell solutions which decreases heating effects. The P‐jump instrument is described, and the electronic circuits for both methods are given. The bipolar pulse circuit diagram is presented and described in detail. Example relaxation curves are shown for single phase and diphasic systems. A signal‐to‐noise improvement of a factor of 2 is observed for bipolar pulse detection over that observed for the optimal ac bridge detection.

A voltage control unit for a spherical sector analyzer used in the energy analysis of scattered ions is described. Three modes of operation, namely, automatic, manual, and computer control is possible. The unit is directly calibrated in terms of the scattered energies which is displayed on a liquid crystal unit. The scanning time in the auto mode is adjustable from 1 to 999 s in 1‐s steps for any selected energy range. A 0–10‐V recorder output is available regardless of the energy window selected. The basic operation and the functioning of the various components are explained with the help of block diagrams and a final evaluation of the system is given. Complete circuit diagrams are available from the Physics Auxiliary Publication Service (PAPS) of the American Institute of Physics.

The layout and construction of a readout electronics for rf superconducting quantum interference devices (SQUIDs) with bias frequencies of 3 GHz are described. The electronics uses standard electronic components and can be aligned using a spectrum analyzer. Differences between a conventional 20‐MHz electronics and this microwave readout are explained. Each individual circuit block is described and circuit diagrams as well as information for pc‐board layout is given. A brief description of thin‐film rf‐SQUIDs used for experiments with this readout electronics is also included.

We describe a simple marginal oscillator that operates at ultralow power dissipation (≥20 μW at 750 MHz) for use in ultrasensitive low noise magnetic resonance detection at very low temperatures. We have operated the circuit down to 0.6 K with the sample maintained below 20 mK and in magnetic fields up to 4.0 T. The samples are maintained at mK temperatures by physically separating the sample from the rf coil.

A lumped circuit model for the two‐dimensional (2D) to 2D tunneling transistor is proposed. A new concept of virtual separation of nodes is introduced to distinguish the energy of the subband edges and the Fermi energy of the quantum wells in the circuit diagram. The two virtually separated nodes are connected by the quantum capacitance due to the quantum confinement of the electrons in each well. This concept provides a simple and accurate representation of the device operation by the geometrical capacitances, the quantum capacitances, and the voltage dependent tunneling resistance.

The hysteresis (extrinsic) and current‐voltage (I‐V) characteristics of the multiwell, vertically integrated, resonant‐tunneling diode are analyzed. Our analysis shows that hysteresis in the vertically integrated diode I‐V can result from interchanging the order in which the devices switch, depending if the bias is increasing or decreasing. Experimental results are presented that support this analysis.

This paper describes the design and operation of a prototype high-voltage full-floating high-frequency square-wave generator which is an improved version of the generator developed by Bernius and Chutjian (1989). The present design overcomes possible momentary simultaneous ON states in the MOSFET configuration and is less susceptible to deleterious effects caused by the component aging and replacements with nonidentical parts. The circuit performs well over a wide voltage and frequency range, until a limit is imposed by the operating characteristics of the active MOSFET elements. Circuit diagrams are presented.

The development of a low-noise variable-temperature preamplifier for self-sensing piezoelectric tuning fork force sensors is presented. The preamplifier utilizes a pair of commercially available GaAs field effect transistors to achieve high impedance and low noise over a wide range of temperatures. Using a standard 32 kHz quartz tuning fork, the base noise level achieved is 20 dB below the thermal noise resonance at room temperature and at 4.2 K. The circuit diagram, biasing points, and noise specifications are presented, and the application for variable temperature scanning probe microscopy is discussed.

This paper proposes a systematic methodology for creating multifolded torus chaotic attractors from a simple three-dimensional piecewise-linear system. Theoretical analysis shows that the multifolded torus chaotic attractors can be generated via alternative switchings between two basic linear systems. The theoretical design principle and the underlying dynamic mechanism are then further investigated by analyzing the emerging bifurcation and the stable and unstable subspaces of the two basic linear systems. A novel block circuit diagram is also designed for hardware implementation of 3-, 5-, 7-, 9-folded torus chaotic attractors via switching the corresponding switches. This is the first time a 9-folded torus chaotic attractor generated by an analog circuit has been verified experimentally. Furthermore, some recursive formulas of system parameters are rigorously derived, which is useful for improving hardware implementation.

The circuit diagram and design principles of a high-stability chopper wheel motor driver are presented. Experimental results show that this unit can be interfaced to molecular-beam machines to generate supersonic beams with extremely stable root-mean-square and peak velocities fluctuating on a day-to-day basis by less than 0.2%.

The simulation of a superconducting flux counting analog‐to‐digital (A/D) converter for advanced high‐speed signal processing systems is performed to investigate its performance and sensitivity. This report describes the algorithms and the results associated with simulating the whole sequence (count‐store‐readout‐reset‐count). Parameter sensitivities are also checked and optimized.

The capabilities of the pulsed Langmuir probe technique have been expanded to operate in charged particle environments having spatial and temporal variations in plasma or reference–electrode potentials. This practice is implemented by logic circuitry which tracks local floating potentials and adjusts automatically the sweep center voltage to guarantee a complete current–voltage characteristic with minimum sweep voltage excursion.

A number of ion cyclotron resonance applications have arisen in the past few years which require a frequency‐scanned detection system. Since the traditional marginal oscillator detector has always been a fixed‐frequency detector, alternative detection techniques such as bridge circuit detectors have become widely used. In this paper we present an alternative to the bridge detector, namely, a frequency‐scanning marginal oscillator. Requirements and modifications necessary to convert a marginal oscillator to frequency scanning operation are discussed in detail and the necessary circuit diagrams presented. Finally, a theoretical comparison is made between bridge circuit and marginal oscillator sensitivities.

Particle sizing interferometer (PSI) signal characteristics, including visibility, peak intensity, number of Doppler signal cycles, and pedestal intensity, are examined for simultaneous use in particle sizing. Requirements are defined for circuitry which can simultaneously measure these characteristics and can be implemented in an existing PSI signal processor. The circuitry was implemented and tested using a rotating wheel and latex spheres. The experimental results confirm circuit reliability.

A high‐performance frequency‐swept capacitance bridge detector for ion cyclotron resonance (ICR) spectrometry has been constructed in our laboratory. Although the basic design of the system is similar to that of previously reported bridge circuits, careful design, layout, construction, and component selection have resulted in excellent frequency‐swept performance over a bandwidth of 15 kHz to 1 MHz. At a magnetic field strength of 1.0 T, this corresponds to a mass range of 15–1000 Daltons. Problems with base‐line drift and frequency‐dependent signal distortion common to many other designs have been significantly reduced. Circuit diagrams are included for all parts of the detector and frequency response curves have been included where appropriate. In addition, several simple circuit diagrams for support devices have also been included.

An electron emission control circuit of the switching regulator type operating at 100 kHz has been developed which maintains a constant emission current within 0.1% for a cathode power demand variation of approximately 100%. The power output stage has an efficiency of 67%, and the overall efficiency is 45% when driving a thoria-coated iridium cathode having a nominal resistance at operating temperature of 2.5 ohms. Under optimum conditions, the bus power demand is 1.75 W. The circuit is useful in controlling the electron emission current of ion sources in applications which involve a substantial variation of the cathode work function, such as oxygen partial pressure measurements over a large dynamic range.

The problem of monochromator–microcomputer interfacing is discussed. As an example, a 0.5M Ebert monochromator is coupled to a PET microcomputer to provide photon counting (15‐MHz max), wavelength readout (0.004‐nm resolution), and scan control. Detailed circuit diagrams and supporting software are presented. Suggestions for adaptation to other monochromator–computer combinations are given.

The present measurement techniques, adapted to the transient hot‐wire method for absolute thermal conductivity determination, allow the realization of a simple apparatus giving automatically precise digital data. It can be connected to a printer or, better, to a computer unit. This device has been tested with a liquid cell and satisfactory agreement with published values was obtained.

The HP 4274A and HP 4275A LCR meters are widely used in the fields of semiconductor device characterization and component test. A bias voltage can be applied to the test samples either from an external power supply or from the built-in HP-IB controllable voltage source. The total series resistance of the bias filtering circuit should be in the range of about 100 Omega (HP 4275A). Detailed measurements and checking the measuring circuit diagrams revealed that the effective series resistance can be much higher, depending on the measuring range of the bridge. Therefore, admittance measurements on low-ohmic samples, especially Schottky or pn junctions under heavy forward bias conditions, are seriously affected by bias voltage reduction between the front HI/LOW terminals. Thus, e.g., a reduced apparent capacitance is measured. Consequently, the doping concentration near the pn junction will be determined erroneously. To avoid the effects, a bias regulating circuit is inserted into the LCR meters to guarantee the feedthrough of the bias voltage without any attenuation. Examples of admittance vs. frequency and doping profiles near the pn junction of quaternary (Ga0.046In0.954As0.1P0.9) diodes are given for explanation.

A new kind of digital correlation device is described which resembles a 3‐level by 3‐level correlator. The product transition correlator consists of a multiplier followed by an accumulator which counts transitions of products from one state to another ranter than the products themselves. Although this approach slightly reduces the signal‐to‐noise ratio of the accumulated product, it results in a simpler design. Consequently the product transition correlator can operate at much faster sample rates than the conventional 3‐level correlators.

The design of a flashlamp triggering and driving circuit is described for the short pulse pumping of a Nd3+ YAlO crystal suitable for Q‐switched operation. The special features of this system were a prepulse circuit for pulsing the flashlamp immediately before the main pulse, and a new method of flashlamp triggering based upon a saturable choke. An increase in laser efficiency and pulse reproducibility was obtained when the prepulse mode of operation was used.

A semi‐automatic recording spectrometer system finds the loci of magnetic field orientations, relative to a single crystal sample, for which an unsplit component occurs in the Zeeman spectrum of chlorine nuclear quadrupole resonances from the sample. The system operates continuously without attention, except for approximately daily resetting, for up to several weeks to obtain the data for crystals with weak spectra. Circuit diagrams are given for the system components, and the analysis of the data is discussed.

The complete constructional details for a 180° Dempster type mass spectrometer are given. The ions have a radius of curvature of 15 cm, and are accelerated through a potential of 2000 volts. Circuit diagrams for the voltage stabilizers and magnet current stabilizer are included.

The design and details of construction of a proportional counter for use in counting gammarays in the high proportional region are described. The circuit diagrams for the preamplifier, the main video amplifier, and the stabilized high voltage supply are included. The counter is operated with pure argon, or with argon plus a little air, at 50‐cm pressure and about 1750 volts. When used with a coincidence circuit, employing blocking oscillators for sharpening the pulses, a resolving time of 4×10−8 second is obtained.

A detailed description of a Stark‐modulation (see reference 1) microwave spectrograph which has been designed and constructed in this laboratory is given. Circuit diagrams and values of the components are given for all the custom‐built equipment. The frequency range is from 17 to 28 kmc/s. Peak Stark‐modulation voltages up to 1500 volts sine wave and 800 volts square wave are used. The sensitivity is better than 1×10−8 cm−1. The absorption lines are about 300 kc wide at half‐power and the practical limit of resolution is between ½ and 1 mc. Frequencies may be measured to better than ±0.08 mc.

The construction of a new zero‐field paramagnetic resonance (ZFPMR) spectrometer is discussed. Spectrometer organization and construction details are presented for both resonant cavities and broadband traveling‐wave helices as sample holders. A new circuit diagram for a square wave magnetic field modulator with fast rise time is given. The performance of each kind of spectrometer is discussed with particular emphasis on investigation of paramagnetic rare earth ions with zero‐field splittings in diamagnetic host lattices.

A simple tunnel diode circuit capable of accurately timing the zero crossing point of bipolar pulses is described. The combination of a fast tunnel diode and a nonlinear load line results in a circuit that can detect the zero crossing of a wide range of input waveshapes. This technique has been utilized in the design of a versatile, fast zero crossing discriminator. This instrument, which is compatible with existing logic systems, exhibits time slewing of less than 200 psec for an input amplitude range of at least 1 to 70 times threshold. Direct coupling and extremely short recovery time enable the instrument to function well at rates as high as 50 MHz.

A cathode‐ray oscillograph using a sealed‐off Braun tube is described with which writing speeds up to twenty inches per microsecond are attainable. The circuit diagrams and description of the instrument are given in some detail in order to facilitate the construction and use of the instrument by others.

A spin echo apparatus is described which can measure nuclear relaxation effects for narrow resonances, convection and diffusion effects, and in some cases, chemical splittings in liquids. This apparatus is assembled mostly from commercial equipment. Commercial units used are identified, and circuit diagrams are given for specially constructed apparatus. Sufficient design information is given to make possible substitutions and improvements to suit the needs of particular projects. Necessary adjustment procedures are described and the relations of instabilities in the apparatus to instabilities in its components are treated.

A pneumatic and an electronic regulator for helium bath temperature are described. The pneumatic regulator, an automatic pressure regulating valve with large throughput, gives a simple controller suitable for regulation to a millidegree for temperatures above 1.4°K. The electronic control uses a carbon resistor for the thermometer and a heater inside the bath for the control element. Its regulation is an order of magnitude better, and it is usable at all achievable temperatures. Its theoretical analysis, circuit diagram, construction and operating details, and performance are described. Included are some general remarks and results concerning temperature regulation in He‐I and at the lambda point.

Automatic inspection of large optical components for the presence of microscopic metallic inclusions in the parts‐per‐quadrillion concentration range is performed by a simple device in which a Q‐switched YAG laser is focused on a continuously scanned sample. Plasma emissions from inclusions are detected by a photomultiplier tube, whose output is monitored by a computer, which then generates an inclusion map. Rapid and reliable inspection of the large optical components required for a variety of high‐energy systems is now possible.

An electronic device is described which generates a delayed pulse, where the delay is increased in a step-like manner. This device finds application in the measurement of kinetic decays, particularly when laser-induced fluorescent (LIF) detection of the decaying species is used. The circuit uses 15 low-power Schottky TTL chips and is contained within a dual width NIM module.

The construction of a new double probe circuit using wide band optically isolated electronic elements is described. The circuit is adaptable to measuring plasma characteristics generted by pulsed discharges. The entire system is powered by a high performance dc/dc converter. The probe and ramp generator circuits are at floating potential and possess an over‐all capacity relative to ground

A new design of a Q‐spoiler, a constant reference load, is introduced and evaluated. The device is useful in the calibration of a marginal oscillator’s relative sensitivity variations with frequency. In a capacitive divider design, the loading of the marginal oscillator with respect to frequency is largely dependent on the choice of components. The new design uses a large resistance and compensates for the resistor’s capacitance by switching between the resistor and another leg of the circuit that has a matched capacitance.

The aim of this investigation was to measure the sensitivity improvement reached on a commercial homodyne X‐band ESR spectrometer by installing a microwave GaAs–FET type preamplifier (8.5–9.6 GHz). Up to a power level of 1 mW a factor of 3 was obtained in signal improvement. Saturation occurred near 30 mW. Both theoretical and experimental results were described and discussed. In addition, a circuit diagram for easy installation of the microwave preamplifier was given.

We have achieved long-term stability in producing high-power single-axial-mode CO2 laser pulses with a hybrid oscillator (TEA laser + low-pressure section) by using a novel digital feedback system that electronically adjusts cavity length.

Two voltage sources are described which can be used with electrostatic analyzers in automated ion–atom collision experiments. One is a 0 to −6 kV supply; the other is a dual (±) 0 to 300 V supply. Circuit diagrams are provided and accuracies discussed.

>The vibrating-plate capacitor used in r-f spectrometers to obtain frequency sweep is replaced with a voltagevariable capacitor, which is essentially a semiconductor diode with a moderately large capacitance. A circuit diagram is given for a superregenerative spectrometer incorporating a diode modulator for chlorine resonances at 20 to 38 Mc. Circuit modifications for lower frequency applications, e.g., for nitrogen resonances, are described. (D.L.C.)

Preamplifier-discriminator-gate generator in printed circuit for use with photomultipliers, noting pulse sensitivity and cost

Wide range pulse height discriminator with milliwatt power drain for use in nuclear experiments on scientific satellites

A blocking oscillator is described that has been used as the discriminator of a 16-nsec resolving time coincidence circuit. It produces 2-v pulses into a 100-ohm load and has a sharp, stable threshold. The time jitter for marginal pulses is approximately 7 nsec. The dead time is approximately 25 nsec. Circuit diagrams are given for both the blocking oscillator and the coincidence circuit. (B.O.G.)

Construction parameters are given for coils to produce field gradients for use in NMR spin‐echo diffusion studies. The coils are shaped to give the greatest field gradient homogeneity in the region of the sample, taking into account image currents in the magnet pole faces. A circuit diagram of the current supply is given, including a transistor switch for pulsing the current.

Air spark gap to switch stored charge in LC circuit, using auxiliary triggering circuit to clamp magnetic flux

A circuit is described which will adapt a laser Doppler velocimeter using real‐time spectrum analysis for automatic velocity tracking. The circuit provides an analog voltage which is proportional to velocity by tracking the position of crossing of a selected intensity level on the spectrum analyzer output. Examples of applications to the study of protoplasmic streaming and simulated hemodynamics are presented.

Current mode amplifier circuit used with carbon resistors for measuring low flow rates of liquid hydrogen from small containers