Showing papers on "Beam (structure) published in 1972"

Coupled‐Wave Analysis of Holographic Storage in LiNbO3

Abstract: This paper considers two effects for directly studying thick‐phase holograms: (a) coupling between the two laser beams used to record a hologram and (b) interference between a readout beam and the diffracted beam within the hologram. Both effects were observed in experiments using single crystals of undoped LiNbO3. The results demonstrate that the holograms arise from electric field patterns caused by either diffusion or drift of photogenerated free electrons.

Mutual coherence function of a finite cross section optical beam propagating in a turbulent medium.

Abstract: On the basis of the extended Huygens-Fresnel principle, a general expression is derived for the mutual coherence function (MCF) of a finite optical beam propagating in a weakly inhomogeneous medium. The results obtained here for the beam MCF are valid both in the near and far field of the laser transmitting aperture and for an arbitrary complex disturbance in the exit pupil of the aperture. A general expression is also derived for the propagation distance z(B) such that for distances much less (greater) than z(B), the MCF is well approximated by the plane (spherical) wave results. An analytic expression is pre-sented for a Gaussian beam such that a numerical error in previous results is corrected. Finally, some comments regarding higher order statistical moments of the field are given.

Banding correction system for film recording apparatus

Abstract: The disclosure pertains to an apparatus for recording an image on a film in a scanned horizontal line pattern with a light beam, the scanned pattern being achieved by reflecting the light beam from a moving surface such as an optical spinner. There is disclosed a subsystem for improving the vertical registration of successive lines in the pattern. Means are provided for sensing the beam position at the beginning of a scanline and for developing a position-indicative signal which varies in accordance with the relative vertical position of the beam. The position-indicative signal is compared to a predetermined reference signal which is a function of the desired position of the beam and there is generated a correction signal which depends on the comparison. Further means are provided for vertically deflecting the beam in accordance with the correction signal.

Backscattering of 0·5-10 keV electrons from solid targets

Abstract: Measurements have been made of electron backscattering in a range of incident beam energy from 05 to 10 keV. The variation of backscattering coefficient η with energy and angle of incidence, and the energy spectrum of backscattered electrons at incidence and take-off angles of 45°, have been measured. Results from carbon, aluminium-silicon, copper and silver were obtained at a pressure of approximately 10−8 Torr to make the effects of contamination under the electron beam negligible. Various simple theories of the backscattering phenomenon which have been used successfully at higher energies are examined in an attempt to understand the processes producing the observed results. Although the theory of elastic scattering of electrons by atoms at low energies is complicated, it is found that a simple theory based on largeangle elastic collisions may explain the experimentally observed rise in η with fall in beam energy, when an accurate range-energy relationship is used. The variation of η with angle of beam incidence can be explained for low atomic number elements on a diffusion theory, but this explanation does not wholly explain the results for copper at low energies. The energy spectra cannot be predicted by any existing simple theory.

Investigation of Gas Solid Reactions by Modulated Molecular Beam Mass Spectrometry

Abstract: An apparatus for the study of gas-solid reactions which produce gaseous reaction products is described. The reactant gas contacts the solid as a molecular beam travelling in vacuum. Gaseous reaction products are monitored by a mass spectrometer as they are emitted from the surface. The technique relies heavily upon modulation of the molecular beam to improve the signal-to-noise ratio. In addition, chopping of the reactant beam induces modulation at the same frequency in the reaction products and the phase differences between these two signals contains important kinetic information. Methods of comparing theoretical models of the surface processes with the phase and amplitude information provided by the experiment are presented.

Theory and simulation of the beam cyclotron instability.

Abstract: A theory of plasma beam cyclotron instability is developed on the basis of computer simulation experiments. The theory holds that at certain turbulence levels, electron cross-field diffusion which supresses the electron gyroresonances is created by turbulent wave-particle interactions in a plasma beam after a period of quasi-linear exponential development of turbulence. The stabilizing effect of Landau ion damping is noted. The behavior of cold and hot ions is discussed.

In-line electron gun

Abstract: The three co-planar beams of an in-line gun are converged near the screen of a cathode ray tube by means of two plate-like grids transverse to the beam paths and having corresponding apertures for the three beams. The three beam apertures of the first grid are aligned with the three beam paths. The two outer beam apertures of the second grid are offset outwardly relative to the beam paths to produce the desired convergence. The three sets of apertures also provide separate focusing fields for the three beams. The second plate-like grid is formed with a barrel shape, concave toward the first grid, to minimize elliptical distortion of beam spots on the screen due to crowding of the adjacent focusing fields. Each of the two outer beams is partially shielded from the magnetic flux of the deflecting yoke by means of a magnetic ring surrounding the beam path in the deflection zone, to equalize the size of the rasters scanned on the screen by the middle and outer beams. Other magnetic pieces are positioned on opposite sides of the path of the middle beam, to enhance one deflection field while reducing the transverse deflection field for that beam.

On non-linear theory of instability of a mono-energetic electron beam in plasma"

Abstract: The excitation of a monochromatic plasma wave by a 'cold' electron beam is investigated. The solution obtained describes the transition from the exponential growth of the wave amplitude in the linear stage to the amplitude oscillations associated with trapping of the beam in the potential well created by the wave. The maximum amplitude and its oscillation period are found. Both non-relativistic and relativistic beams are investigated.

Laser device particularly useful as surgical scalpel

Abstract: A laser beam manipulator device, particularly useful as a surgical scalpel, comprises a tube connectable at one end to a movable conduit down which a laser beam propagates and a beam targeting member carried by the tube at its opposite end The manipulator device includes a lens that focuses the laser beam to a point in a plane substantially passing through the tip of the beam targeting member at right angles to the longitudinal axis of the tube To permit viewing of the working area at the focal point of the laser beam while the device is being manipulated, at least a portion of the tip of the beam targeting member either is removed or is made of a transparent material

Thermal blooming of laser beams in fluids.

Abstract: Thermal blooming of laser beams in liquids and gases has been studied using geometrical optics The intensity profiles, light rays, and fluid density changes are determined as functions of time and of the initial beam profile Short and long time behavior are derived The effects of thermal conduction and viscosity are included Special beam profiles such as a uniformly illuminated aperture, a parabolic profile, and a Gaussian beam are treated The on-axis beam intensity as given by the theory is compared to the data proved by Kenemuth et al and is shown to fit within the experimental error

Transverse Vibrations of Double‐Tapered Cantilever Beams

Abstract: The differential equation is developed from the Bernoulli‐Euler equation for the free vibrations of a double‐tapered cantilever beam. The beam tapers linearly in the horizontal and in the vertical planes simultaneously. From a computer solution of this equation, a table has been developed from which the fundamental frequency, second, third, fourth, and fifth harmonic can easily be obtained for various taper ratios. Charts are plotted for selected taper ratios in the vertical plane to show the effect of taper ratios on frequency.

Stability of a beam on an elastic foundation subjected to a follower force.

Abstract: Discussion of a new aspect in the behavior of a cantilevered beam on an elastic foundation subjected to a follower force at its free end. The critical load for flutter is found to be independent of the foundation modulus which characterizes the Winkler-type elastic imbedding. The frequency of vibration of the beam increases with increasing foundation modulus, but the magnitude of the critical load is not affected. This result is valid for any 'tangency coefficient' value.

Convergence of consistently derived Timoshenko beam finite elements

Abstract: The accuracy and convergence properties of two new Timoshenko beam finite elements are compared to those now widely used. Both of the new elements are consistently derived from a variational principle written in terms of the transverse beam deflection and normal rotation. The deflection is expanded as a cubic and the rotation as a quadratic in the axial co-ordinate of the beam, giving rise to a seven degrees of freedom element. The first element, called TIM7, includes all the degrees of freedom while the second, called TIM4, reduces this number to four through a constraint introduced by Egle. Both elements display monotonic covergence for beam natural frequencies as a function of the number of degrees of freedom and both will give the analyst some measure of confidence in response calculations for beams excited at high frequencies.

Molecular Beam Study of the K+CH3I Reaction: Energy Dependence of the Detailed Differential Reactive Cross Section

Abstract: A molecular beam study has been carried out on the reaction of a velocity‐selected K beam with a crossed beam of CH3I (from a glass capillary‐array source). Velocity analysis of the angular distribution of the reactively scattered KI has yielded detailed differential cross sections at three incident relative kinetic energies Ē= 1.77, 2.80, and 3.71 kcal/mole. The center‐of‐mass (c.m.) differential cross sections were obtained from the lab data by a least‐squares computer ``inversion'' program providing for deconvolution of beam velocity distributions. The c.m. cross section is ``backward'' peaked (KI recoiling opposite to the incident K, in accord with the literature) with a very sharp (30%–40% FWHM) recoil velocity distribution which maximizes at 80% of the energetically allowed KI recoil velocity. This distribution shifts systematically to higher velocities with increasing incident collision energy. Averaging over all angles yields an overall product c.m. translational energy distribution which shifts u...

Microminiature ganged threshold accelerometers compatible with integrated circuit technology

Abstract: The device described permits threshold acceleration detection in a wide range from a few ten's of g's up to maybe 100 000 g's. It is a threshold sensing device with an extremely high on-to-off resistance ratio. The device consists of a flexible metal beam and an associated contact pad, which is activated by the force of the beam's inertial mass when being accelerated in a direction normal to the contact plane. The mechanical and electrical operation of the accelerometer is analyzed and expressions are given for the relationship between beam deflection, acceleration detection level, and various required beam dimensions. A batch fabrication procedure is demonstrated and acceleration test results up to 8000 g's are reported for multiple ganged accelerometers.

Measurement of the radius of a high-power laser beam near the focus of a lens

Abstract: The flux-time waveform from a mechanically chopped laser beam is used to find a Gaussian pattern approximating to the distribution of energy in the beam. The technique, which is insensitive to errors in locating the beam centre, has been used to measure the minimum radius of a carbon dioxide laser beam having a continuous power of 2 kW focused into a region less than 2 mm in diameter.

Electric Resonance Spectroscopy of Hypersonic Molecular Beams

Abstract: A hypersonic nozzle beam (Mach 19) of HCN molecules was studied by electric resonance spectroscopy. Translational temperatures of 4°K and rotational temperatures of 64± 30°K were found from a 283°K nozzle source. The monoenergetic character of the beam and the rotational cooling lead to an order of magnitude increase in signal‐to‐noise ratios. The absence of an appreciable velocity dispersion and a homogeneous radiation field allowed a critical comparison with theoretical two‐level resonance lineshapes. An SF6 diluent was used to reduce the beam velocity by one‐half and increase spectral resolution over a thermal (effusive) source. SF6 vibrational relaxation was observed. Chemically interesting species can be formed: ArXe, XeHCl, (HCl)2, (HCN)x, and (HF)x.

Stimulated emission of radiation in periodically deflected electron beam

Abstract: A tunable generator or amplifier of coherent radiation in the infrared, optical, ultraviolet and X-ray regions with the capability for operation at power levels in excess of a megawatt with high efficiency A relativistic electron beam is periodically deflected by a transverse magnetic field defined by a linear array of magnets, adjacent magnets having opposing polarities Each time the electron is deflected it emits a burst of radiation The combination of the individual bursts yields a beam of radiation of comparatively small angular divergence and small spread in frequency Due to the difference in the electrons' recoil during emission and absorption, the frequency at which absorption occurs for radiation in the electron beam is slightly higher than that for emission and gain is available due to the stimulated emission of radiation for operation at frequencies on the low frequency side of the spontaneously emitted radiation spectrum

Interaction of a Highly Energetic Electron Beam with a Dense Plasma.

Abstract: The interaction of an electron beam with a relatively dense background plasma was examined through numerical experiments, where the beam velocity is much greater than the thermal velocities It is shown that the initial growth of the unstable waves is described by the two‐stream instability and that the phenomena can be separated into two regions, (high and low density) depending on whether or not merging of space‐averaged velocity distributions occurs during the growth of the initially most unstable wave The occurrence of these regions is shown to follow from energy and momentum considerations The long‐time behavior of the low‐density regime, where the merging does not take place during the initial growth of the instability is shown to be described quite well by quasilinear theory

E×B Mass‐Separator Design

Abstract: The equations of motion are developed and solved for ion trajectories inside an E×B type mass separator Curves are presented which illustrate the focusing of the undeflected ion beam, the trajectories along which ions of different mass species disperse inside the separator channel, and the exit slopes of mass species leaving the separator, as functions of a separator strength parameter For strong separators, beam focusing is significant and is shown to be nonaxisymmetric when the electric and magnetic fields are uniform and orthogonal A method of correcting the astigmatism by tilting the magnetic pole pieces is presented

Radiation Resistance of a Baffled Beam

Abstract: The radiation resistance of a beam is theoretically determined from the total acoustic power radiated into the farfield. The beam is supported in an infinite baffle, with both hinged and clamped supports considered. Asymptotic solutions are derived for frequencies well below the critical frequency. Curves, covering the entire frequency range between the low‐ and high‐frequency asymptotic solutions, are obtained through numerical integration for the first ten modes of beams with various width‐to‐length ratios. For frequencies well below the critical frequency, the ratio of the radiation resistance of a beam clamped at each end to that of a beam hinged at each end is 0.851 for the first mode, 0.711 for the second mode, and asymptotically approaches 2 as the mode number tends to infinity. For both hinged and clamped supports, the radiation resistance of all modes increases with the beam width‐to‐length ratio.

Parametric Acoustic Transmitting Arrays

Abstract: A numerical solution of Westervelt's inhomogeneous wave equation is obtained to describe the pressure field of sum and difference frequency radiations created by the nonlinear interaction of two monochromatic carriers in the farfield of a circular piston source. Experimental results are presented on the propagation and beam patterns of sum and difference frequency radiations resulting from the interaction of 418‐ and 482‐kHz carriers emitted by a 3‐in.‐diam piston located in a fresh water lake. These results support the numerical methods. Several approximations commonly made to obtain dosed‐form solutions are then evaluated with the numerical solution.

Beam-Foil Study of Nitrogen in the Vacuum Ultraviolet

Abstract: The beam-foil spectrum of nitrogen has been studied between 300 and 1250 A at beam energies of 0.5–2 MeV. Some newly observed lines have been identified and the lifetimes of some excited levels of N ii, N iii, N iv, and N v have been measured.

Process for laser scribing beam lead semiconductor wafers

Abstract: Microelectronic circuits are produced in semiconductor wafers with beam leads having adhering and non-adhering portions. The non-adhering portions comprise the projecting part of the beam lead. The wafer is divided into chips having beam leads by partially cutting the wafer from the reverse side with a laser beam. The wafer is initially positioned for the laser cutting using an infrared light and a vacuum for securing the wafer at the correct position prior to the laser scribing. The uncut portion of the wafer is broken and the semiconductor chips are separated. During the separation, the non-adhering portions of the beam leads become separated from adjacent chips.