An in-line reversal electron, high-current ionizer capable of focusing a beam of electrons to a reversal region and executing a reversal of the electrons, such that the electrons possess zero kinetic energy at the point of reversal, may be used to produce both negative and positive ions. A sample gas is introduced at the point of electron reversal for low energy electron-(sample gas) molecule attachment with high efficiency. The attachment process produces negative ions from the sample gas, which includes species present in trace (minute) amounts. These ions are extracted efficiently and directed to a mass analyzer where they may be detected and identified. The generation and detection of positive ions is accomplished in a similar fashion with minimal adjustment to potentials applied to the apparatus. NASA CSCL 14B A tunable infrared detector which employs a vanishing band gap semi-metal material provided with an induced band gap by a magnetic field to allow intrinsic semiconductor type infrared detection capabilities is disclosed. The semi-metal material may thus operate as a semiconductor type detector with a wavelength sensitivity corresponding to the induced band gap in a preferred embodiment of a diode structure. Preferred semi-metal materials include Hg(1-x)Cd(x)Te, x is less than 0.15, HgCdSe, BiSb, alpha-Sn, HgMgTe, HgMnTe, HgZnTe, HgMnSe, HgMgSe, and HgZnSe. The magnetic field induces a band gap in the semi-metal material proportional to the strength of the magnetic field allowing tunable detection cutoff wavelengths. For an applied magnetic field from 5 to 10 tesla, the wavelength detection cutoff will be in the range of 20 to 50 micrometers for Hg(1-x)Cd(x)Te alloys with x about 0.15. A similar approach may also be employed to generate infrared energy in a desired band gap and then operating the structure in a light emitting diode or semiconductor laser type of configuration. NASA N89-28797# North Carolina Univ., Chapel Hill. Dept. of Computer EXPLORING VIRTUAL WORLDS WITH HEAD-MOUNTED James C. Chung, Mark R. Harris, F. P. Brooks, Henry Fuchs, and (Contracts N00014-86-K-0680; PHS-RR-02170-05) Research has been conducted in the use of simple head mounted displays in real world applications. Such units provide the user with non-holographic true 3-D information, since the kinetic depth effect, stereoscopy, and other visual cues combine to immerse the user in a virtual world which behaves like the real world in some respects. UNC's head mounted display was built inexpensively from commercially available off-the-shelf components. Tracking of the user's head position and orientation is performed by a Polhemus Navigation Sciences' 3SPACE tracker. The host computer uses the tracking information to generate updated images corresponding to the user's new left eye and right eye views. The images are broadcast to two liquid crystal television screens (220x320 pixels) mounted on a horizontal shelf at the user's forehead. The user views these color screens through half-silvered mirrors, enabling the computer generated image to be superimposed upon the user's real physical environment. The head mounted display was incorporated into existing molecular and architectural applications being developed at UNC. In molecular structure studies, chemists are presented with a room sized molecule with which they can interact in a manner more intuitive than that provided by conventional 2-D displays and dial boxes. Walking around and through the large molecule may provide quicker understanding of its structure, and such problems as drug enzyme docking may be approached with greater insight. GRA N89-28798# Max-Planck-Inst. fuer Physik und Astrophysik, Munich (Germany, F.R.). Werner-Heisenberg Inst. fuer Physik. DEVELOPMENT OF A NOVEL SILICON DETECTOR WITH INTERNAL AMPLIFICATION Thesis Tech. Univ. Munich [ENTWICKLUNG EINES NEUARTIGEN SILIZIUMDETEKTORS MIT INTERNER VERSTAERKUNG] Karl-Friedrich Schuster Nov. 1988 66 p In GERMAN (MPI-PAE/Exp.El-197; ETN-89-94389) Copyright Avail: NTIS HC A04/MF A01 The first test versions of a new high-purity silicon radiation detector were designed and produced. The detector operation principle was aimed at applying an internal gate for a combination of a MOS field effect transistor and lateral depletion. This principle was confirmed by the tests. The energy resolution of the detectors at 300 K and 6keV is shown to be a halfwidth of 520eV and significantly better than that of the conventional uncooled detectors. The detector principle allows the realization of an addressable two-dimensional detector matrix with nondestructive readout possibility. The measured signal-to-noise ratio of the single detector is better than 400 for minimum ionizing particles. Novel fast readout procedures with good spatial resolution (about 50 micron) in high energy physics are then allowed. ESA function. Instrumental errors produced by internal sampling processes, the instrument noise and the calibration uncertainties were investigated. Aliasing is shown to be reduced by about a factor of ten due to the telescope aberrations which act as a low pass filter and to special demodulation algorithms that virtually double the sampling frequency of the optical chopper. The instrument noise can be reduced to the level of the detector noise using an improved compensation technique. The calibration accuracy in the solar channels is limited by the uncertainties of the calibration lamp. The dominant error sources in the thermal infrared channels are probably temperature fluctuations of blackbodies and baffles. ESA N89-28800# Technische Univ., Berlin (Germany, F.R.). Inst. fuer Luft- und Raumfahrt. PIEZOELECTRIC FOILS AS SENSORS IN EXPERIMENTAL Wolfgang Nitsche Oct. 1988 23 p In GERMAN Avail: NTIS HC The use of piezoelectric foils as sensors for the analysis of complex aerodynamic flow fields is discussed. The sensors consist of a thin (9 to 100 micrometer) and highly elastic thermoplastic film. It can be mounted, trouble-free, on the surface of very complex flow configurations, and is thus a completely covering array of sensors, allowing large-scale surface force determination. The piezofoil is an active signal source which only requires a suitable amplifier. Wind tunnel tests on wing profiles show that flow instabilities and the characteristics of laminar-turbulent boundary layer transition can be determined. These results were confirmed by free flight tests, which also demonstrate the possibility of on-line data evaluation. Examples of the use of piezoelectric matrix, and taster sensors for the recognition of global flow structures, are ESA given. N89-28801# Institut Franco-Allemand de Recherches, Saint-Louis (France). ON STRAIN GAGES USING THE PVF2 PIEZOELECTRIC POLYMER Progress Report [ETAT DES RECHERCHES SUR LES JAUGES DE CONTRAINTE EN POLYMERE PIEZOELECTRIQUE PVF2] F. Bauer, R. A. Graham, L. M. Lee (Ktech Corp., Albuquerque, NM.), and G. Samara (Sandia Natl. Labs, Albuquerque, NM.) 17 May 1988 12 p In FRENCH; ENGLISH summary Presented at the 2nd Congres International sur le Comportement Mecanique et Physique des Materiaux sous Sollicitations Dynamiques, Ajaccio, France, 19-23 Sep. 1988 (Contract DRET-85-193) (ISL-CO-210/88; ETN-89-94850) Avail: NTIS HC A03/MF A01 The frequency, temperature, and hydrostatic pressure dependences of the dielectric properties, molecular relaxation, and phase transition in PVF2 (polyvinyl fluoride) and a copolymer with 30 percent trifluorethylene are presented. The dynamic melting temperature shows a large increase with pressure. The electrical response of film shock gages with various degrees of polarization are studied under shock loading (35 GPa). The observed response shows good fidelity until 30 GPa. The value of the remanent polarization has a significant influence on nonlinearity and probably affects the maximum useful stress for shock gage applications. ESA N89-28803# Centre d'Etudes et de Recherches, Toulouse (France). Dept. d'Etudes et de Recherches en Mecanique et Energetique des Systemes. EXPERIMENTING CAVITATION MEASURING INSTRUMENTS Final Report [EXPERIMENTATION DE DISPOSITIFS DE MESURE DE POCHE DE CAVITATION] G. Toulouse Sep. 1988 63 p In FRENCH (Contract DRET-87-002-16) (CERT-2305; ETN-89-94868) Avail: NTIS HC A04/MF A01 A calibrating method for measuring the volume of cavitation bubbles is presented and the results of open air experiments are given. The bubbles appearing on the surface of a marine rotating propeller are measured using CCD cameras and optical procedures. Square bubble section first approximations is used. The performance of cameras equipped with light amplifiers is studied in order to use them for real bubble cross section measurements. ESA N89-28804# Institut Franco-Allemand de Recherches, Saint-Louis (France). THE PROBLEM OF VERY HIGH MAGNIFICATIONS IN HOLOGRAPHY H. Royer 22 Jun. 1988 17 P Presented at Optics-ECOOSA 88, Birmingham, United Kingdom, 24 Mar. 1988 (ISL-CO-218/88; ETN-89-95031) Avail: NTIS HC A03/MF A01 The problem of high magnification in holography is discussed. The study is focused on problems concerning the image magnification, the in-line system for Gabor's two step processes, the recording in parallel light, the gain of resolution, and the off-axis system. It is concluded that three steps processes are required to obtain optimum results the recording at a specific wave length (lambda), the magnification (g) of the hologram itself, and the reconstruction (at lambda prime = to g multiplied by lambda). The fringes must be larger than the intermolecular distance of the ESA recording material. N89-28805# Danish Space Research Inst., Lyngby. THE FLUXGATE RINGCORE SENSOR DEMAGNETISING F. Primdahl, B. Hernando, O. V. Nielsen, and J. R. Petersen A method for measuring the demagnetization of fluxgate sensors is introduced and used to evaluate the demagnetizing factors for 4 ringcore sensors having 5, 10, 15, and 20 wraps of magnetic core ribbon. The demagnetizing factor is proportional to the number of wraps, and the noise is also proportional to the number of wraps except for the more noisy 5 wrap core. The estimated internal core noise was 1 pT RMS taking into consideration the demagnetizing factor and the relative permeability of the core material. N89-28806*# Author National Aeronautics and Space Administration. Lewis Research Center, Cleveland, OH. FATIGUE TESTING APPARATUS Patent Application Robert J. Buzzard, inventor (to NASA) 21 Aug. 1989 14 p (NASA-Case-LEW-14124-1; NAS 1.71:LEW-14124-1; US-Patent-Appl-SN-396263) Avail: NTIS HC A03/MF A01 CSCL 14B An apparatus is provided for obtaining a single crack in fatigue loading which emanates from a predetermined starting notch in a test specimen. This crack propagates in a direction in line with that of the applied Mode 2 load. The loading may be performed either monotonically or in a cyclic fatigue. NASA Southampton Univ. (England). Inst. of Sound and N89-28807# Vibration Research. NEARFIELD ACOUSTIC HOLOGRAPHY: REVIEW AND PERSPECTIVES A. E. Perezmatzumoto, F. J. Fahy, and S. J. Elliott Jul. 1989 107 P (ISVR-TR-179; ETN-89-95532) Avail: NTIS HC A06/MF A01 The development of the Nearfield Acoustic Holography technique (NAH) for planar arrays is reported. A critical review shows that this technique represents an improvement over standard Acoustic Holography (AH) only for reconstructions of sources radiating at low frequencies. The possible reasons for a bad source reconstruction in NAH are investigated. The sensitive parameters for producing this distortion in a given system are detected. It is shown that the aliasing of the signal requires a formal approach or research. This formal approach is necessary for generalizing the technique, and for avoiding the subjectivity in choosing a good reconstruction. The results lead to the conclusion that prior knowledge of the source under study is required, making NAH a case-by-case method. The choosing of the true solution appears to be a time consuming technique from just a mathematical approach, or a highly subjective technique if there is not a formal approach. At the present state of development, NAH can only work in some cases. A system for industrial applications does not seem a real possibility at the present time. ESA N89-28808# Oak Ridge National Lab., TN. Michael Finley (Transylvania Univ., Lexington, KY.) Jun. 1989 16 p (Contract DE-AC05-84OR-21400) (DE89-013720; ORNL/TM-11198; CESAR-89/24) Avail: NTIS HC A03/MF A01 Segmentation and non-linear surface fitting with laser range images are attempted on a hypercube concurrent processor. Low-level software acquires range images onto the hypercube. A substantially modified existing range image edge detector works in the hypercube image analysis environment to accomplish segmentation. The Levenberg-Marquardt algorithm implements the non-linear least squares fitting of the surfaces. Problems were found with each part of the approach. The edge detection algorithm is unnecessarily complex and yields an all too cluttered edge map. The fitting routine is limited by hardware in the number of surfaces that it can process. Finally, the fitting approach requires input estimates of the parameters which do not appear to be generalized for any image, thus keeping the process from being totally automated. Other research in surface fitting on serial computers has yielded results which may be helpful additions to solve the problems of automation. DOE N89-28809# National Bureau of Standards, Boulder, CO. Time and Frequency Div. THE 12C160 LASER FREQUENCY TABLES FOR THE 34.2 TO 62.3 THz (1139 TO 2079 cm-1) REGION M. Schneider, K. M. Evenson, M. D. Vanek, D. A. Jennings, J. S. Wells, A. Stahn, and W. Urban (Bonn Univ., Germany, F.R.) Aug. (Contract W-7405-eng-36) (DE89-014023; LA-UR-89-1932; CONF-890665-30) Avail: NTIS HC A03 AURORA is a KrF laser system at Los Alamos designed to demonstrate the feasibility of optical multiplexing for KrF lasers. The first two amplifiers in the amplifier chain are the Small Aperture Module (SAM) and the Pre-Amplifier (PA). The engineering design of replacement hibachis for the SAM and PA as part of a general upgrade to increase e-beam pumping is described. Hibachi shading loss mechanisms are briefly discussed. A simple model that calculates relative shading losses between hibachis for the axial-field-free case is presented. Based on modeling results, sample hibachi slots were fabricated and foils tested to destruction to verify standard membrane stress equation. Test results were used in the design and fabrication of hibachis that were installed on the amplifiers. Relative energy deposition measurements using capacitive manometers are presented. DOE N89-28811# Los Alamos National Lab., NM. Chemical and Laser Sciences Div. CHEMICAL AND LASER SCIENCES DIVISION Annual Report, 1988 Jun. 1989 117 P (Contract W-7405-eng-36) (DE89-014385; LA-11600-PR) Avail: NTIS HC A06/MF A01 This annual report from the Chemical and Laser Sciences Division at Los Alamos contains both programmatic and technical information on the following research: KrF lasers for inertial confinement fusion; free electron lasers; neutral particle beam sensing; chemical sensing; mass spectroscopy; orbit simulations; high temperature kinetics; and microwave absorption spectrometers. N89-28812# Lawrence Livermore National Lab., CA. LINEAR THEORY OF UNCOMPENSATED THERMAL BLOOMING IN TURBULENCE DOE D. H. Chambers, T. J. Karr, J. R. Morris, P. G. Cramer, J. A. (DE89-014604; UCID-21696) Avail: NTIS HC A03/MF A01 A linearized theory of small perturbations in thermal blooming gives a surprisingly accurate description of the initial evolution of a plane wave propagating through an absorbing fluid medium. In the case of constant absorption and fluid velocity, a sinusoidal perturbation of the optical field grows quasi-exponentially at a rate determined by its Fresnel number and the accumulated OPD due to blooming. Perturbations with small transverse length scales grow more rapidly than those with large length scales. The evolution of the optical spectrum and Strehl ratio in the presence of optical turbulence is accurately described. The growth of the small scale fluctuations eventually leads to a drop in Strehl. More complicated cases with varying absorption and velocity profiles can be formally analyzed using a WKB approximation. Numerical simulations show growth suppression when the velocity varies along the optical path. These predictions from the linearized theory agree well with results from numerical simulations of the full nonlinear system and thus provides a standard for comparing different numerical codes. DOE N89-28813# Mound Lab., Miamisburg, OH. Larry R. Dosser and Carl J. Seliskar 23 Jun. 1989 20 p (DE89-013740; MLM-3590) Avail: NTIS HC A03/MF A01 The chemical aging of pentaerythritol tetranitrate (PETN) was and continues to be an important problem in producing and maintaining high energy compounds and components. The work done to date has identified several key concerns in evaluating the chemical and physical aging processes of PETN. These include the manner in which a particular type of PETN is prepared, the sample preparation procedure insofar as it can influence the adsorbed species on the solid PETN, and the methods of measurement and their influence on the quantitative determination on the gaseous decomposition products. In the work reported here, two noninvasive spectroscopic methods of measurement were chosen: laser induced fluorescence, which was used to monitor NO2, and ultraviolet spectroscopy, which was used to monitor NO. A unique sample vessel design permitted both measurements to be made on the sample, and these two species could readily be measured in the presence of one another. Adsorbed NO2, and its subsequent reaction to yield NO, was detected. Three types of PETN samples were aged at elevated temperatures, and varying amounts of NO and NO2 were detected, depending on the sample and the method of preparation. The results indicate that an in situ experiment is necessary to further DOE investigate PETN aging. N89-28814# Lawrence Livermore National Lab., CA. 14 p (DE89-014325; UCID-21734) Avail: NTIS HC A03/MF A01 A recently developed approximate theory is used to estimate the magnitude of the space-charge potentials and electric fields that could be produced within a plasma column exposed to the focussed microwave beam from the Livermore free-electron laser (FEL). The plasma, composed of electrons and singly charged high mass ions, is assumed immersed in a solenoidal magnetic field with a strong longitudinal gradient. Cyclotron resonance of the electrons in the magnetic field leads to rapid heating and an associated strong axial expelling force resulting from the interaction of the electrons' magnetic moment with the magnetic field gradient. lon inertia, together with the quasineutrality constraint, leads to the development of a flat-bottomed potential well, thereby forcing the electron loss rate to equal the inertia-dominated rate of the ions. This phenomenon, first observed experimentally in the 1960's, is made much more effective by the high power levels of the FEL. At present FEL power levels (2 GW), positive potentials of 4 MV and associated sheath electric fields approaching 1 GV/meter are predicted, with column-averaged fields of order 50 MV/meter. At projected FEL power levels, potentials of 15 MV, and sheath fields of 1.6 GV/meter are predicted. These figures are much higher than the corresponding figures for conventional RF or induction-type ion accelerators. Plasma parameters appropriate for a proof-of-principle experiment are given. DOE N89-28815# Naval Research Lab., Washington, DC. (AD-A209740; NRL-MR-6463) Avail: NTIS HC A03/MF A01 CSCL 09/3 The free electron laser (FEL) has been developed to the point where projections of its high-power capability have made it an important component of the directed-energy research program within the Strategic Defense Initiative. To achieve the desired near-visible wavelength and high intensity, stringent demands are placed on the electron beam that drives the FEL. Typical requirements are high peak current (0.2 to 2 kA) at a kinetic energy of 100 to 150 MeV, small energy spread (less than 1 percent), small diameter (less than 3mm), and low divergence (less than 0.1 mrad). Either an induction linear accelerator (linac) or an RF linac may be a suitable candidate to provide the electron beam. The technical issues and technology needed to achieve a visible light FEL driven by an RF linac are described. A recently installed RF linac at Boeing Aerospace is used as the principal illustrative example. GRA LASER-INDUCED DIODE LINKING FOR WAFER-SCALE S. S. Cohen, P. W. Wyatt, G. H. Chapman, and J. M. Canter 16 (Contract F19628-85-C-0002) (AD-A207921; TR-820; ESD-TR-88-224) Avail: NTIS HC A09/MF A01 CSCL 13/8 The use of laser beam melting of silicon for the purpose of forming electrical links between two adjacent diodes is studied. The diodes, which are formed by ion implantation and diffusion in a conventional CMOS process, are positioned such that when desired they may be used to obtain an electrical link between two otherwise separated sections of the integrated circuit. Electrical connections so obtained enable the realization of wafer-scale ICS, as demonstrated in recent applications. The theory of laser beam application to silicon is discussed, and the various beam and substrate parameters are shown to affect the properties of the diode links. Particular attention is paid to the important issue of the reflectivity from the composite system. Careful analytical examinations of the resulting molten zone properties were performed in order to fully qualify the use of laser radiation in this technology. Both scanning electron microscopy and secondary-ion Carl B. Collins Apr. 1989 69 p (Contract N00014-86-C-2488) (AD-A208071; GRL/8804) Avail: NTIS HC A04/MF A01 CSCL 09/3 Recent approaches to the problem of the gamma-ray laser have focused upon upconversion techniques in which metastable nuclei are pumped with long wave length radiation. At the nuclear level the storage of energy can approach tera-Joules 10 to the 12th power per liter for thousands of years. An approach to the gamma-ray laser that depends upon incoherent pumping is examined. This nuclear analog of the ruby laser embodies the simplest concept for a gamma-ray laser and it is not surprising that the greatest rate of achievement toward a sub-Angstrom laser has continued in this direction. Emphasis has remained upon the giant pumping resonances that enabled the dumping of populations of the only available sample of the 29 candidates, Ta 180 sub m, through a cross section that was 10,000 times more favorable than even the most optimistic estimates. The lessons taught by that major milestone were extended throughout the region of mass-180 nuclides. Reported is the success in pumping of only two of the candidates that are accidentally available, together with 17 other comparison isomers with the bremsstrahlung X-rays from a MeV linac. Previous excitations of the giant resonances pumping these materials had been made with a continum of photon energies reaching to 6 MeV and concern had lingered that the full 6 MeV of energy might have been actually needed. At such values the density of nuclear states is high and the onset of evaporation of particles from nuclei is near. Either would make the resonances useless to laser development. GRA N89-28820*# David Sarnoff Research Center, Princeton, NJ. AlGaAs PHASED ARRAY LASER FOR OPTICAL COMMUNICATIONS Final Report, 6 Aug. 1987 - 9 Jun. 1989 N. W. Carlson Sep. 1989 57 p (Contract NAS1-18525) (NASA-CR-181869; NAS 1.26:181869) Avail: NTIS HC A04/MF A01 CSCL 20E Phased locked arrays of multiple AlGaAs diode laser emitters were investigated both in edge emitting and surface emitting configurations. CSP edge emitter structures, coupled by either evanescent waves or Y-guides, could not achieve the required powers (greater than or similar to 500 mW) while maintaining a diffraction limited, single lobed output beam. Indeed, although the diffraction limit was achieved in this type of device, it was at low powers and in the double lobed radiation pattern characteristic of out-of-phase coupling. Grating surface emitting (GSE) arrays were, therefore, investigated with more promising results. The incorporation of second order gratings in distribute Bragg reflector (DBR) structures allows surface emission, and can be configured to allow injection locking and lateral coupling to populate 2-D arrays that should be able to reach power levels commensurate with the needs of high performance, free space optical communications levels. Also, a new amplitude modulation scheme was developed for GSE array operation. Author (Contract NAS1-18539) (NASA-CR-181870; NAS 1.26:181870) Avail: NTIS HC A04/MF A01 CSCL 20E A design for a monolithic narrow-linewidth InGaAsP diode laser has been developed using a multiple-quantum-well (MQW) extended-passive-cavity distributed-Bragg-reflector (DBR) laser design. Theoretical results indicate that this structure has the potential for a linewidth of 100 kHz or less. To realize this device, a number of the fabrication techniques required to integrate low-loss passive waveguides with active regions have been developed using a DBR laser structure. In addition, the MOCVD growth of InGaAs MQW laser structures has been developed, and threshold current densities as low as 1.6 kA/sq cm have been obtained from broad-stripe InGaAs/InGaAsP separate-confinement-heterostructure MQW lasers. Author (ETN-89-94425) Avail: NTIS HC A03/MF A01 The improvement of the efficiency of solid state was investigated, with emphasis on the method of the spectral adaptation of the lamp emission to the absorption band of the laser medium (Nd:YAG). Measurements to determine the technical limits of excitation lamps, taking into account their lifetime, are shown to be unsuccessful due to the production related differences in the lamp behavior. Theoretical studies and experimental tests show the realizability of metal-halide-doped excitation lamps with high brightness and long lifetime. The conversion of radiation by means of a fluorescent layer is shown to be unrealistic at the required power densities. ESA Fachbereich Physik. QUANTITATIVE INVESTIGATION OF THE KINETICS OF A Arne Kallenbach 1988 136 p In GERMAN A numerical model was developed for the description of a barium vapor which is nearly resonantly excited by laser. The atomic constants, required for the model, were experimentally elaborated since they are not at all or very inaccurately known in the literature. The data of the most important elementary processes were experimentally obtained by a systematic variation of the parameters. The adaptation of the model calculations to the measured values gives a complete set of cross sections and transition probabilities, resulting in the quantitative understanding of the essential phenomena in the vapor. The time evolution of the excitation of eleven real states, several radiation processes, and the ionization of barium were calculated, in good agreement with the experiments. ESA N89-28824 Technische Univ., Hanover (Germany, F.R.). Fachbereich Physik. INCREASE OF THE DAMAGE THRESHOLDS OF DIELECTRIC DIELEKTRISCHER SCHICHTSYSTEME FUER DEN-ND-LASER] High power layer systems were developed and optimized using the electron beam vapor deposition technique, with emphasis on the determination of the parameters which influence the interaction between dielectric layers and intense layer radiation. The |