Showing papers on "Beam (structure) published in 1980"

Generating of coherent radiation by a relativistic electron beam in an ondulator

Abstract: A detailed study of the self-modulation of a relativistic electron beam in an ondulator in the single-pass regime is carried out. Beam-parameter conditions are obtained under which the radiative instability in question occurs. The possibility of constructing a source of coherent radiation based on this principle is discussed. The radiation spec­ ifications of such a source are analyzed. Control the mass of longitudinal motion with the help of an additional longitudinal magnetic field introduced in the ondulator is discussed. Numerical examples are given for sources of submillimeter and infrared-range radiation.

Computation of mode properties in optical fiber waveguides by a propagating beam method

Abstract: Propagating beam solutions for optical waveguides can be made to generate such mode-related properties as propagation constants, relative mode powers, and group delays with high precision and considerable flexibility. These quantities are needed in the analysis of optical fiber dispersion. The technique requires the generation of correlation functions from the numerical solutions of a wave equation. These correlation functions are in turn Fourier-transformed with respect to axial distance z. The resulting spectra display sharp resonances corresponding to mode groups, and the positions and heights of these resonances determine the previously mentioned mode properties. The spectral analysis is made highly accurate by the use of line-shape fitting techniques. With this method, mode group delays can be determined to a precision of +/-0.12 psec/km using a computation covering a 5-cm propagation path.

Spot scanning system for proton radiotherapy

Abstract: In order to provide a uniform and desirable dose distribution over a large radiation field, spot beam scanning is one of the most useful methods. A new spot beam scanning system was constructed for a 70 MeV proton beam. The lateral dose distribution was uniform with +/- 2.5% for an 18 cm square field. It was possible to control the dose at each point in the radiation field by this spot scanning method. This system has been confirmed to be satisfactory for delivering a proton beam in the desired field shape and dose level.

Method of crystallizing amorphous material with a moving energy beam

Abstract: An improved method for crystallizing amorphous material with a moving beam of energy is disclosed. In this method, the energy beam is scanned in a manner to provide controlled, continuous motion of the crystallization front.

Intense pulsed ion beams for fusion applications

Abstract: The subject of this review is the field of intense pulsed ion beam generation and its potential application to fusion research Considerable progress has been made in the past six years Power levels of the order of 1000 MW/cm2 have been obtained for pulse-lengths from 10−8 to 10−6 s Light-ion beams with currents approaching 1 MA and energies exceeding 1 MeV have been produced The first half of the paper treats the physics and technology of beam generation Following a unified discussion of the theory of ion injectors, experimental work since 1973 is reviewed Diagnostic techniques appropriate to high-flux ion beams are summarized The general problem of high-current ion beam transport in vacuum and through plasmas is also considered The second part of the paper is devoted to applications to fusion research Applications in both magnetic confinement and inertial confinement fusion are considered Intense ion beams have a number of features which make them ideally suited as inertial fusion drivers Discussions are given of the physics of inertial fusion targets, options for ion beam production, experiments on light-ion beam focusing, and high-current multi-stage accelerators

Control for laser hemangioma treatment system

Abstract: A laser for directing a nominally 5 micron wavelength beam at a hemangioma or other variegated lesion. A fiber optic bundle for intercepting radiation reflected from the lesion at an intensity corresponding with the color intensity of the region at which the beam is directed. The output beam from the fiber optic bundle modulates a photodetector stage whose amplified output drives a galvanometer. The galvanometer shaft is coupled to the shaft of a potentiometer which is adjustable to regulate the laser power supply and, hence, the laser output energy level so laser beam energy is reduced when high absorption regions in the lesion are being scanned by the beam and increased as low absorption regions are being scanned.

The effect of reverse currents on the dynamics of nonthermal electron beams in solar flares and on their emitted X-ray bremsstrahlung

Abstract: Recognizing the possible importance of reverse current ohmic energy losses from beams of electrons injected into the solar atmosphere during flares, we solve the equations governing the dynamics of such beams, taking into account energy and momentum losses of the beam particles by both collisional and ohmic heating processes. it is found that for injected fluxes compatible with hard X-ray burst observations of fairly large flares, the inclusion of ohmic terms results in a substantial modification of the variation of electron energy and pitch angle with depth in the target. The chromospheric energy deposition due to the beam, and X-ray bremsstrahlung emitted by the beam, are also evaluated for a variety of empirical flare model atmospheres, and it is found that, although both these quantities decreases as the injected electron flux increases, their ratio is insensitive to the parameters of the problem. Further, the emitted nonthermal X-ray flux is found to be bounded by a limiting value only marginally consistent with observations, thus suggesting that a significant portion of the X-ray flux is thermal in origin. The dependence of the results obtained on the model atmosphere used in the calculations is discussed.

Computation of mode eigenfunctions in graded-index optical fibers by the propagating beam method.

Abstract: The propagating beam method utilizes discrete Fourier transforms for generating configuration-space solutions to optical waveguide problems without reference to modes. The propagating beam method can also give a complete description of the field in terms of modes by a Fourier analysis with respect to axial distance of the computed fields. Earlier work dealt with the accurate determination of mode propagation constants and group delays. In this paper the method is extended to the computation of mode eigenfunctions. The method is efficient, allowing generation of a large number of eigenfunctions from a single propagation run. Computations for parabolic-index profiles show excellent agreement between analytic and numerically generated eigenfunctions.

Development of a supersonic O(3PJ), O(1D2) atomic oxygen nozzle beam source

Abstract: A high pressure, radio frequency discharge nozzle beam source has been developed for the production of very intense (⩾1018 atoms sr−1 s−1) supersonic beams of oxygen atoms. An efficient impedance matching scheme has been devised for coupling the radio frequency power to oxygen–rare gas mixtures as a function of gas pressure, temperature, and composition. Techniques for localizing the discharge directly behind the orifice of a specially designed quartz nozzle have also been developed. The above combine to yield a beam source which reliably produces a high degree of molecular dissociation in oxygen–rare gas mixtures at pressures up to 350 Torr. Atomic oxygen mean translational energies from 0.14–0.50 eV have been achieved using the seeded beams technique with Mach numbers up to 10 being realized. When helium is used as the carrier gas both O(3PJ) and O(1D2) atoms are present in the beam, while only ground state atoms appear to be present in argon seeded mixtures. This paper describes the design, constructi...

Multipurpose exercising machine

Abstract: An exercising apparatus for developing selected muscles of the body comprises a rigid upright support having a first beam pivoted on a horizontal axis near the top of the support and a second beam similarly pivoted below the first beam. The two beams are connected by a telescopic adjustable link so that they move together at selected distances from one another. Handles and shoulder pads are provided for lifting the first beam and a weight holding rod is located on the outer end of the second beam for receiving a selected number of weights to be lifted. The rate of movement of the bars during lifting of the weights is maintained substantially constant by an isokinetic device connected between the structure and one of the beams. The combination of the two beams and the adjustable link facilitates the use of the apparatus for a wide range of sizes of people and a wide range of different exercises.

Beam shaping optical system

Abstract: This specification discloses a beam shaping optical system for treating the diverging beam emitted from the exit surface of a semiconductor laser. The beam from the semiconductor laser has different angles of divergence and different origins of divergence in directions orthogonal to each other. Such a beam may be collimated or efficiently treated into a circular spot light by the beam shaping optical system.

Beam models for SS 433.

Abstract: We analyze the energetics of models for SS 433 which derive the large oscillatory Doppler shifts from the 164 day precession of a pair of oppositely directed beams. We propose that the beams power the emission lines (both shifted and unshifted), the compact X-ray source, and the radio source by dissipating a small fraction of their kinetic energy as they sweep through an ambient gaseous medium. An X-ray photoionization model fits the data well. The beams are also responsible for the elongated shape and filled-in structure of the extended radio source W50. From these two manifestations, we infer that the luminosity in kinetic energy in each beam exceeds 10/sup 40/ ergs s/sup -1/, five orders of magnitude greater than the H..cap alpha.. luminosity.

Position measuring system

Abstract: A position measuring system comprising a transmitter (5, 19) mounted on one body and arranged to direct a flashing beam of radiation onto an area sensor (11) which is mounted on the other body and forms part of a receiver arranged to produce an output indicative of the position of impingement of the beam on the sensor from samples of the radiation impinging on the sensor when the beam is on and off, the receiver including a second sensor (31) responsive to the radiation beam whose output synchronizes the operation of the receiver to the flashing beam The requirement for a physical connection between receiver and transmitter to synchronize the receiver with the flashing beam is thereby avoided

The anisotropic interaction potential of D2Ne from state‐to‐state differential cross sections for rotational excitation

Abstract: Differential cross sections for the rotational excitation from j=0 to j=2 of D2 scattered by Ne have been measured at an energy of E=84.9 meV. The experiments have been performed in a crossed nozzle beam apparatus with time‐of‐flight analysis of the scattered particles using the pseudorandom chopper method. A detailed analysis of the experimental data which are peaked in the backward direction showed that they are mainly sensitive to the repulsive part of the pure anisotropic potential. From a combined analysis of the state‐to‐state differential cross sections of the j=0 to j=0 and the j=0 to j=2 transition of D2+Ne and the j=0 to j=1 transition of HD+Ne previously measured, the complete potential energy surface for the hydrogen–neon system is obtained using the coupled states method. The anisotropic contribution varies from 37% of the isotropic part in the repulsive region (2.4 A) to 12% in the attractive region (3.5 A). The results differ from the other potential models derived for this system from calc...

Topographic display of evoked potentials: clinical applications of brain electrical activity mapping (beam)*

Abstract: It is widely agreed that long-latency sensory evoked potentials (EPs) are sensitive not only to stimulus parameters, but to variations of brain state. On this basis, one might predict that such EPs would achieve widespread clinical use paralleling that of the EEG. With a few exceptions, this has not been the case. We do not believe that this results from an inherent insensitivity of E P to cerebral pathophysiology. On the contrary, we propose that such measures of brain electrical activity represent not too little, but too much clinical information to be easily appreciated by unaided inspection or measurement. To assist clinical appraisal of such data, we have recently developed a system for the topographic mapping and computerized display of scalp-recorded signals referred to as brain electrical activity mapping or BEAM.’ As routinely used in our laboratory, BEAM images are constructed from data gathered from 20 scalp electrodes placed in the standard 10-20 EEG format (FIGURE 1). Resultant topographic images are displayed on a computer-driven color video monitor using a colored “grey” scale. For E P data, we visualize the dynamic change of electrical activity with time by sequential display of images; the display technique produces an animation effect highlighting the spread of E P activity over the scalp. These methods condense and summarize the spatiotemporal information obtained from multielectrode recordings to facilitate analysis by visual inspection. BEAM is now a routine clinical neurophysiological test in the Seizure Unit a t Childrens Hospital Medical Center, Boston. Clinical referrals over the last 12 months blanket a wide spectrum of neuropathology including epilepsy (21%), learning disability (22%), emotional disturbance and dementia (14%), headache (lo%), and unknown neurological disease (33%). BEAM appears to be most applicable to cases where the CT scan is either normal or noncontributory to the clinical question a t hand. Two refinements of the BEAM methodology have improved its applicability as a clinical instrument: (1) Significance probability mapping, a procedure for statistically delineating abnormal regions; and (2) Grid sector analysis, a procedure for quantifying the degree of overall and/or focal abnormality in BEAM images. In the following

Apparatus and method for neutralizing the beam in an ion implanter

Abstract: An ion implanter apparatus is described with provision for neutralizing the space charge potential of the ionic beam with a closed loop feedback system responding to the electrical charges that tend to accumulate on a target specimen. Neutralization is provided by a controllable electron source surrounding the beam. Flow of electrons to a plate radially outward of the electron source is used to derive a signal proportional to the beam ion current when the space charge potential of the beam is neutralized. The beam current signal can be used (1) to provide a read-out display for the operator; (2) to control the magnitude of the ion beam; (3) to be integrated to determine the total positive charge that enters the Faraday cage of the implanter for use to control the ion beam shutter; or (4) to effect relative movement of the specimen and the beam.

Integrated circuit chip package with improved cooling means

Abstract: An integrated circuit package in which an integrated circuit chip having flexible beam leads, the inner lead bonding sites of which are bonded to input and output terminals on the active face of the chip, is mounted active face down on the top surface of a substrate. The top surface of the substrate is provided with a chip pad on which the integrated circuit chip is mounted and outer lead pads. The back surface of the substrate has a heat sink pad which is positioned substantially opposite the chip pad. A plurality of thermal passages is formed through the substrate interconnecting the chip pad and the heat sink pad. A good thermally conductive material fills the passages. A preform comprising a segment of fiber glass web coated with a thermosetting and thermally conductive plastic is positioned on each chip pad between the chip pad and the active face of the integrated circuit chip. The plastic material of the preform encapsulates the active face of the chip, including a portion of each of the leads proximate the chip and secures the chip to the chip pad. The outer lead bonding sites of the leads are bonded to outer lead pads of the substrate with exposed portions of the leads between the outer lead pads and the encapsulated portions being bent away from the substrate and under compression. A heat sink is bonded to the heat sink pad. The plastic material of the preform, the chip pad and the thermally conductive material filling the thermal passages provide a low impedance thermal path between the integrated circuit chip and the heat sink.

Backward Compton scattering of laser light against high-energy electrons: the LADON photon beam at Frascati

Abstract: In the present paper we present the experimental results obtained for the backscattering of laser light against the high-energy electrons stored in Adone with the laser cavity dumping technique. The characteristics of the obtained photon beam (LADON beam) are discussed and compared with the theoretical previsions given by the usual storage ring theory.

On the Nonlinear Deformation Geometry of Euler-Bernoulli Beams.

Abstract: Nonlinear expressions are developed to relate the orientation of the deformed beam cross section, torsion, local components of bending curvature, angular velocity, and virtual rotation to deformation variables. The deformed beam kinematic quantities are proven to be equivalent to those derived from various rotation sequences by identifying appropriate changes of variable based on fundamental uniqueness properties of the deformed beam geometry. The torsion variable used is shown to be mathematically analogous to an axial deflection variable commonly used in the literature. Rigorous applicability of Hamilton's principle to systems described by a class of quasi-coordinates that includes these variables is formally established.

Glued-Laminated Beam Strength: A Model

Abstract: A model for the prediction of bending and tensile strength of glued-laminated beams is developed. The model accounts for effect of size, lamination thickness effect, E-rating, and proof-loading of the individual laminations, and it can be used in computer simulations to estimate the distribution of beam strength. Eight types of beams, differing in size as well as in lamination lay-up, were tested. The experimental results are compared with the model’s simulations and the agreement is found to be satisfactory.