Pulse Coupling Research Articles

Simple High Performance General Purpose Single Channel Analyser

A simple single channel analyser using standard components is described. High temperature stability (0.002% / °C) and resolution (? 100 ?V) is achieved. The two-level generator circuits described allow full DC coupling of the input pulses. The performance of these circuits is discussed in detail and experimental results presented.

Coupling of Gaussian electromagnetic pulse into a muscle-bone model of biological structure.

The effect of angle of incidence on the transmission electromagnetic pulse with Gaussion character in biological material is studied. The model assumed is a layer of soft tissue over a semi-infinite medium of boney structure governed by alpha dispersion. The numerical results demonstrate that the transmitted pulse strength is the greatest when the pulse is incident normally on the air-tissue interface. The coupling efficiency for a one microsecond pulse is three times as big as that for a ten microsecond pulse.

EMP Coupling Analysis Using the Frequency (Transfer Function) Method with the SCEPTRE Computer Program

The availability of digital computer time and scientific programming languages (such as Fortran) has, resulted in the use of the digital computer for electromagnetic pulse (EMP) coupling analyses. This report describes combining complex frequency domain analysis techniques with the SCEPTRE computer program to evaluate the time response of the current induced on a thin-wire scatterer when the scatterer has been excited by an arbitrary shaped electromagnetic pulse. The method is illustrated by performing an analysis for the current which would be induced by a fast rise time EMP (unit step) and a relatively slow rise time EMP (waveshape similar to that produced by a lightning stroke).

Plasma production from solid targets by nanosecond prepulses

A model of the laser-plasma-solid system is developed to study the dynamics of the laser prepulse interaction with initially solid slabs. Experiments are conducted using aluminum wires and fast-rise ruby lasers and the results are used to verify the theoretical model. The results of numerical experiments are used to investigate the dependence of plasma formation on the prepulse parameters and to find those parameters which lead to efficient coupling of a subsequent giant heating pulse with the target material.

Role of turbulence in the coupling of a magnetic pulse to a collisionless plasma

The coupling of a magnetic pulse to an initially magnetized collisionless plasma is studied experimentally using a high voltage theta pinch. The plasma parameters studied include: the turbulent electric fields, particle heating, magnetic and electric field profiles, and the plasma resistivity. The results indicate that the interaction of the plasma with the magnetic pulse can be understood using a fluid model which includes anomalous resistivity and particle heating. The source of the anomalous resistivity is investigated based on the presently available instability theories.

SIMULTANEOUS MODE LOCKING AND PULSE COUPLING OF THE CO2 LASER

Simultaneous mode locking and pulse coupling of a CO2 laser has been achieved using a single internal GaAs element with electrodes on both the (001) and (110) faces. Coupling of pulses from the laser did not affect the stability of the mode-locked pulse train. Possible application of the technique to pulse-code modulation of the CO2 laser is discussed.

Subnanosecond pulse coupling of an He-Ne laser

A 0.5ns rise time 2.5kV coaxial krytron pulse generator is described, which, together with an electro-optic modulator, comprises a laser intracavity coupler an order of magnitude faster than any yet reported. Iterative round-trip energy coupling has been demonstrated in accordance with theoretical predictions.

Coupling of high peak power pulses from He-Ne lasers

Coupling of high peak power pulses from He-Ne lasers

New Ultrasonic Liquid Level Gauge

A new ultrasonic liquid level gauge without moving parts is described in which two wire helices are employed as acoustic waveguides, transmitting sound energy from the top of the tank to the liquid surface and back. The directional propagation in the receiving wire is controlled by the sense of the helix and synchronous reinforcement of pulse coupling between the wires by the side-by-side juxtaposition of the two helices is achieved, resulting in a high signal-to-noise ratio of the device.

Reliability Improvement in Pulse Transformers

As part of the NASA Orbiting Geophysical Observatory (OGO) program, an investigation was made of failure mechanisms in miniature pulse transformers, a type commonly used for drive pulse coupling in low-power digital circuitry. The resulting corrective action methods are useful for reliability improvement in other similar magnetic devices and components. Failures were traced to breaks in small diameter magnet wire. Examination showed two possible causes of failure: (1) mechanical stressing of material during assembly and (2) metallurgical stressing of the fine copper wire during soldering. Preventive action was taken to eliminate accidental mechanical stress. To avoid metallurgical changes during soldering, a process specification was developed to prevent gross solution of the solder. This was accomplished by close control of soldering temperature, wider distribution of heat at the joint, and control of the time material is held at soldering temperature. Tests verified the effectiveness of these process improvements. No failures have been experienced in subsequent manufacturing.

A High Temperature Remote Pulse Preamplifier System for Reactor Startup Channels

Source and startup-range pulse instrumentation for large reactor plants in general impose severe environmental conditions on the design of preamplifiers and pulse coupling networks. Space or size limitations electrical noise fields, high ambient temperatures, and lack of accessibility for maintenance all adversely affect signal-to-noise ratio and reliability. An additional problem was present in the design of the startup preamplifier system for the Hallam Nuclear Power Facility (HNPF) because the detector was located in a high gamma field, making some special precautions necessary to prevent small-signal pileup. This paper describes the design of a preamplifier system which overcomes these problems and yields high stability and long term, maintenance-free service at ambient temperatures up to 100°C. The installed system shows at least a 35 db improvement in signal-to-noise ratio over conventional instruments in the same application. Remote location of the preamplifier (up to about 100 feet) from the detector is possible so that the preamplifier itself is out of both the radiation field and the highest temperature locations. The system consists of the chamber and transformer coupling network (between chamber and preamplifier,) and a reliable, high stability preamplifier.