Showing papers by "Raytheon published in 1973"

Multiphonon Relaxation of Rare-Earth Ions in Yttrium Orthoaluminate

Abstract: Nonradiative relaxation by multiple-phonon emission was investigated for excited electronic states of rare-earth ions in YAl${\mathrm{O}}_{3}$. Ions studied included ${\mathrm{Nd}}^{3+}$, ${\mathrm{Eu}}^{3+}$, ${\mathrm{Ho}}^{3+}$, ${\mathrm{Er}}^{3+}$, and ${\mathrm{Tm}}^{3+}$. Rates of multiphonon emission were determined from the difference of measured excited-state lifetimes and calculated radiative lifetimes. Electric dipole transition probabilities were computed using Judd-Ofelt intensity parameters for rare earths in YAl${\mathrm{O}}_{3}$. Multiphonon decay rates, measured for seventeen different levels with energies to the next-lower level ranging from 1400 to 4700 ${\mathrm{cm}}^{\ensuremath{-}1}$, exhibited an approximately exponential dependence on energy gap $\ensuremath{\Delta}E$ given by $W(0){e}^{\ensuremath{-}\ensuremath{\alpha}\ensuremath{\Delta}E}$, where $W(0)=5\ifmmode\times\else\texttimes\fi{}{10}^{9}$ ${\mathrm{sec}}^{\ensuremath{-}1}$ and $\ensuremath{\alpha}=4.6\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}3}$ cm. Exceptions to the exponential law occur only when selection rules severely restrict the number of terms in the ion-lattice interaction active in inducing transitions. The phonon frequency distribution and ion-phonon coupling in YAl${\mathrm{O}}_{3}$ were examined from infrared, Raman, and vibronic spectra. Although phonon energies range up to 750 ${\mathrm{cm}}^{\ensuremath{-}1}$, measurements of the temperature dependence of multiphonon emission indicate that phonons of energies $\ensuremath{\sim}550\ensuremath{-}600$ ${\mathrm{cm}}^{\ensuremath{-}1}$ make the dominant contribution to the relaxation at temperatures 77-700 \ifmmode^\circ\else\textdegree\fi{}K.

Optical Intensities of Rare-Earth Ions in Yttrium Orthoaluminate

Abstract: Optical absorption and emission intensities are investigated for trivalent rare earths in YAl${\mathrm{O}}_{3}$. Ions examined included Pr, Nd, Eu, Tb, Ho, Er, Tm, and Yb. Oscillation strengths of $f\ensuremath{\rightarrow}f$ transitions between $J$ manifolds were measured at room temperature and compared with calculated electric and magnetic dipole oscillator strengths. The Judd-Ofelt approach and phenomenological parameters for each ion were used to derive the electric dipole intensities. The intensity parameters, which were obtained for a least-square-fitting procedure, exhibited a general decrease with increasing number of $4f$ electrons throughout most of the series. The intensities for Pr and Tb were not satisfactorily accounted for in the present theory; some reasons for this are presented.

Fresnel zone plate imaging of gamma rays; theory

Abstract: The use of a Fresnel zone plate as a coded aperture for imaging incoherent radiation such as gamma rays has been previously reported. The coded image is in many respects similar to a hologram and can be decoded or reconstructed with a coherent optical system. In this paper, the general theory of coded-aperture imaging is presented, first for an arbitrary code and then for an on-axis zone plate, an off-axis zone plate, and a one-dimensional zone plate (or linear chirp). With the on-axis plate, a matched imaging condition is suggested as a guide to optimizing image contrast. With the off-axis zone plate and the linear chirp, it is necessary to use a half-tone screen to spatially heterodyne the object spectrum into the passband of the aperture. In all three cases, expressions for the resolution, depth of field, field of view, and relative efficiency are derived. A simplified noise analysis is presented, and some practical system constraints are discussed.

Pipeline signal processor

Abstract: A signal processor including a programmable arithmetic controller and a pipeline arithmetic unit controlled by such controller is disclosed. The arithmetic unit includes a plurality of serially coupled processing levels. The arithmetic controller includes a corresponding plurality of serially coupled control levels, each one of such control levels being coupled to a corresponding one of the processing levels. Each one of the processing levels passes digital data applied thereto in accordance with a control instruction applied to such processing level by the arithmetic controller. As data passes through the various processing levels, the control instruction associated with such data passes through the corresponding control level so that such control instruction ''''follows'''' such data as both data and control instruction pass through the processor. In this way the processor is adapted to start a new process concurrently as such processor completes a prior process.

Inertially stabilized gimbal platform

Abstract: An inertially stabilized gimbal platform is disclosed wherein the gyros used in such system operate about their mechanical null positions and control the gimbal drive means through an electronic control section. The electronic control section includes a control signal which is combined with the gyro output to provide a drive signal for the gimbal drive means. The control signal is proportional to the offset between the electrical null position and the mechanical null position of the gyro. The control signal may be modified in accordance with platform command signals to orient the platform in a desired attitude.

Deep submergence transducer

Abstract: A transducer assembly providing a conversion between the electrical and sonic energy, the transducer assembly being adapted for operating submerged at great depths in ocean waters. The transducer assembly is formed by a front and back plate which are affixed in one embodiment to the ends of a first mechanically distributed impedance member, a second mechanically distributed impedance member located between the front and the back plate and a transducer of electroacoustical material mechanically coupling the first and second members for imparting sonic vibrations to these members. In a preferred embodiment, the transducer is bonded at one end thereof to the back plate and at the other end thereof to the second member. External hydrostatic pressure present at the front and back plates does not compress the electroacoustical material.

Confirmation of an Electron Avalanche Causing Laser-induced Bulk Damage at 1.06 microm.

Abstract: Measurements have been made on intrinsic optical bulk breakdown in ten alkali halides at 1.06 μm and in one at 0.69 μm. By comparing the results to previously reported experiments conducted at 10.6 μm and at direct current, it has been possible to identify the damage mechanism as electron avalanche breakdown. Self-focusing has been controlled by restricting the probe powers to well below the critical powers for catastrophic self-focusing, and damage from inclusions has been distinguished from intrinsic damage. Implications of this work for surface damage studies are explored.

Laser-Induced Damage Probability at 1.06 μm and 0.69 μm

Abstract: The first directly comparable measurements of the laser-induced surface damage process at both ruby and Nd:YAG laser wavelengths are reported. The most striking feature of the data is that all the materials studied are harder to damage at 0.69 μm than at 1.06 μm. The probabilistic nature of the laser-induced damage process at 1.06 μm was explored further by measuring the distribution of breakdown starting times with an image-converter streak camera. The observed distribution is described by the compound probability that breakdown occurs at a particular time, given that it has not occurred before that time. In addition, several connections between the probabilistic and thresholdlike interpretations of laser-induced damage are discussed. It is shown that these points of view are not totally incompatible.

Twist reflector design using E-type and H-type modes

Abstract: A complete solution of plane wave scattering from a twist reflector of infinite extent for arbitrary incidence is presented. The solution is accomplished through the use of an E -and H -type modal representation of the fields in the twister and free space regions. The equivalent circuits for strip and parallel plate twister gratings are derived by transforming E and H mode results [5] to appropriate type mode parameters. The modal reflection coefficients \Gamma' and \Gamma'' are determined from these equivalent circuit parameters and together with the use of a type mode description of the incident and reflected fields lead to two simple conditions for an optimum design; one geometric, namely \tan \phi = \sec \theta and one electrical, \Gamma"/\Gamma' = - 1 . The computed performance of this optimum twist reflector in terms of a cross-polarized suppression ratio versus incidence angle for various planes of incidence represents the best that can be done with any physical structure. A design procedure including design formulas and curves is given from which twist reflector dimensions can be determined. Experimental verification for two specific implementations, parallel plates and parallel strips twist reflectors, is described.

Remotely powered transponder having a dipole antenna array

Abstract: A transponder having a novel circuit for the extraction of power from an incident interrogating beam of electromagnetic energy, the extracted power being utilized to operate a digital coding circuit. The transponder further comprises an oscillator circuit for developing a train of pulses of electromagnetic energy with successive pulses occurring in a coded format in accordance with a digital code imparted by the digital coding circuit. The transponder is of sufficiently small size to be affixed in the form of a tag to automobiles, personnel, containers and other objects to be identified. An interrogation system for utilizing the electronic tag is also disclosed.

Statistical properties of two sine waves in Gaussian noise

Abstract: A detailed study is presented of some statistical properties of the stochastic process, that consists of the sum of two sine waves of unknown relative phase and a normal process. Since none of the statistics investigated seem to yield a closed-form expression, all the derivations are cast in a form that is particularly suitable for machine computation. Specifically, results are presented for the probability density function (pdf) of the envelope and the instantaneous value, the moments of these distributions, and the relative cumulative density function (cdf). The analysis hinges on expanding the functions of interest in a way that allows computation by means of recursive relations. Specifically, all the expansions are expressed in terms of sums of products of Gaussian hypergeometric functions and Laguerre polynomials. Computer results obtained on a CDC 6600 are presented. If a and b are the amplitudes of the two sine waves, normalized to the rms noise level, the expansions presented are useful up to values of a,b of about 17 dB, in double precision on the CDC 6600. A different approximation is also given for the case of very high SNR.

Closely spaced orthogonal dipole array

Abstract: A broadband phased array antenna is shown wherein pairs of mutually orthogonal printed radiating elements, each one of such elements having a flared notch formed therein, are adapted to transmit or receive radio frequency energy having any one of a variety of polarizations.

Microwave power divider

Abstract: A stripline power divider is disclosed wherein three center conductors are joined at a common junction and the ground planes have slots formed therein adjacent to the common junction Reflections resulting from mismatched impedances terminating a pair of the center conductors radiate through the slots A load material is disposed over the slots to absorb any such radiating reflections

Clear air turbulence detector

Abstract: A system to be employed by an aircraft for the detection of clear air turbulance (C.A.T.) in which a pulse laser light beam is directed ahead of the flight path of the aircraft and the portion of this light reflected back to the aircraft by atmospheric aerosol is detected and analyzed for doppler shift and thus the velocity and intensity of the turbulence is determined.

Bus controller for digital computer system

Abstract: An arrangement is shown for controlling transmission of blocks of information to and from a plurality of major components of a digital computer system interconnected by common buses. The disclosed arrangement operates so that any component of the system may normally seize, on a nonpriority basis, one of the buses at the beginning of any time slot defined by two successive clock pulses generated by a single source and applied to all components simultaneously; however, if a special instruction is encountered during execution of a program, any component may retain a bus for more than one time slot. The disclosed arrangement also permits error checking of transmitted information from a given major component without interfering with transmission from any other major component and automatically causes retransmission of any block of information found to be improperly transmitted originally. Still further, the disclosed arrangement permits buses to be dedicated during execution of a program or, if desired, any complete major component to be replaced without affecting any other major component.

The continuous-cathode (emitting-sole) crossed-field amplifier

Abstract: The crossed-field amplifier (CFA) is an outgrowth of the magnetron. Several varieties exist including the forward-wave/ backward-wave types, and the injected-beam continuous-cathode (emitting-sole) types. Of these, the continuous-cathode type has found the most usage and has been established in many systems. Emphasis is placed upon this type. The CFA interaction process has similarities to a synchronous generator. From this, many of the characteristic features can be deduced or understood. The size, efficiency, range of performance, phase stability, and operating parameters are a feature of the crossed-field interaction process which distinguishes the CFA from other microwave tubes. Its greatest usage is in light-weight transportable radar systens, although not restricted to these. Its future lies in the extension of its gain capability and in the incorporation of technological advances such as new materials.

Monitoring and control means for evaluating the performance of vibratory-type devices

Abstract: Apparatus and method for determining the operative effectiveness of a vibrating means coupled to a non-linear load, said apparatus comprising a vibrating means operatively connected to a source of vibratory energy and having coupling means for connecting to a non-linear load, vibration sensing means electrically connected to a harmonic analyzing means having an output electrically connected to an indicator means which may include a display means and a control means.

Format insensitive digital computer

Abstract: A digital computer wherein data words representing different data types, such as fixed point numbers, floating point numbers of logical statements, are retrieved from memory in any order required during execution of a program and, after conversion to a predetermined format, are applied to an arithmetic unit for processing. To accomplish the conversion, logic circuitry is provided to identify, during execution of a program, the data type of each retrieved data word and to change the format of each such word to the predetermined format for processing in the arithmetic unit. Additional logic circuitry is provided to respond to each data word out of the arithmetic unit to reconvert each such word back into a format for storage in memory.

Extended monochromatic x-ray source

Abstract: An extended radiating aperture for X-rays is provided by means of a stationary target of a heavy metal positioned for uniform illumination by high speed electrons emanating from a cathode and accelerating through a difference of potential between the cathode and the target. The target is in the form of a relatively thin film which can be deposited on a substrate transparent to X-radiation. A layer of fluorescent material is placed adjacent the substrate on the opposite side thereof from the target so that X-rays generated within the target material pass through the target material and impinge on the fluorescent layer. The fluorescent material enhances the monochromaticity of the X-ray spectrum by emitting fluorescent X-radiation while substantially absorbing incident X-radiation having energies above the fluorescent radiation spectrum. A zone plate is positioned adjacent the fluorescent layer to spatially modulate the radiation of the radiating aperture to provide this radiation with a spatial frequency spectrum suitable for obtaining high resolution roentgenograms. The zone plate provides a coding on the roentgenogram which is then decoded by an optical processor to form a visible image of an object being X-rayed. Alternative embodiments of the invention include the use of an inclined transmissive target, a transmissive target having serrations, and the use of a moire pattern mask between the target and the fluorescent material to augment fluorescent radiation from the target and to inhibit the passage of X-radiation normal to the layer of fluorescent material.

The mutual information principle and applications

Abstract: A general theory of prior probability models is presented, valid for both discrete and continuous random variables, even when the prior information about them has been obtained with errors. An example is included as an illustration.

Mine rescue system

Abstract: A mine rescue system for locating trapped miners following a mine disaster. A transmitting device deployed by the trapped miners transmits a signal at a frequency below 3 kHz. The phase of the signal received on the surface is measured with respect to the signal received at an arbitrary reference point and the position on the surface is found where the phase lead is maximized over the reference thus locating the point below which the miners are trapped. The system may be extended to provide for two-way communications between the surface and the mine. Also, the invention encompasses means to guide a rescue drill bit.

Adapting Microwave Techniques to Help Solve Future Energy Problems

Abstract: The relationship between microwave techniques and the growing concern for future sources of energy is reviewed. The relationship is specifically explored in the use of a microwave beam to efficiently transport power from an array of solar photovoltaic cells in space to the Earth's surface. Recent advances in power conversion technology and experimental results on overall efficiency of free-space power transmission are reviewed.

Fresnel Zone Plate Imaging in Radiology and Nuclear Medicine

Abstract: X-ray tubes and gamma ray cameras have traditionally involved trade-offs between spatial resolution and radiation flux. Recently we have shown that the use of a Fresnel zone plate as a spatially-coded source or aperture can avoid this trade-off. In radiology, this technique can eliminate the need for a rotating anode and give higher resolution, while in nuclear medicine it can be used either to decrease patient dose or exposure time, or to increase resolution and greatly simplify the apparatus. With a coded source or aperture, the image is also coded, like a hologram and can be reconstructed optically. The system is tomographic with information about all planes contained in a single film.

Microwave heating and vapor condensing apparatus

Abstract: Microwave apparatus together with an intergral vapor condensation collection system is disclosed for any heating and/or drying application. The oven enclosure walls include means for the circulation of a fluid medium to condense substantially all vapors released by the treated material. The condensed fluids are collected in the lower section of the apparatus by gravity and are either recirculated or removed. The microwave energy generator means is suitably isolated by energy permeable means, as well as, a warm air circulation system to minimize attenuation of the energy by the condensed vapors. Perforated partition means are provided in the collector region to substantially inhibit the escape of microwave energy from the oven enclosure.

Microwave heating apparatus for rotatable articles

Abstract: An applicator is provided in combination with a microwave nonradiant energy source having means for automatically sensing and maintaining a predetermined distance with respect to the article being heated. In one embodiment a tire having a nonuniform cross-sectional contour is continuously rotated and axially displaced while the sensor means contact the outer surfaces of the tread to track the disposition of the tire relative to an energy applicator such as a horn radiator mounted on a motorized cart. Electromechanical actuators and limiters are incorporated with the sensor means to generate electrical data to control the movement of the energy radiator in a forward and backward direction. Another embodiment comprises a motorized cart arrangement with a sloped track bearing the sensor and energy radiator means utilizing the force of gravity to maintain contact.

Surface acoustic wave filter

Abstract: An acoustic wave filter is disclosed in which a number of input/output transducers are mounted on a piezoelectric substrate upon which surface waves may propagate in a continuous manner. The substrate may consist of either a continuous surface where the surface waves can circulate or a planar substrate with reflectors at either end of the substrate so that the waves will reflect back and forth from end to end. With such a device, using a single input transducer and a plurality of output transducers or alternatively a plurality of input transducers and a single output transducer, a narrow-band filter may be realized. In the preferred embodiment, the input or output transducers may be switched in and out thereby switching in and out different frequency response peaks. The device may be embodied as a switchable frequency selection device in a multichannel transceiver.

Surface acoustic wave phase control device

Abstract: A surface acoustic wave device in which a phase or velocity shifting electrically conductive layer is located between the receiving and transmitting transducers. In one embodiment as a filter, the phase shift may be varied as a function of frequency over a broad range of frequencies by varying the shape of the conductive layer thereby permitting a desired phase response to be achieved.