Science.gov

Sample records for 315mj 2-micrometers double-pulsed

  1. Laser Energy Monitor for Double-Pulsed 2-Micrometer IPDA Lidar Application

    NASA Technical Reports Server (NTRS)

    Refaat, Tamer F.; Petros, Mulugeta; Remus, Ruben; Yu, Jirong; Singh, Upendra N.

    2014-01-01

    Integrated path differential absorption (IPDA) lidar is a remote sensing technique for monitoring different atmospheric species. The technique relies on wavelength differentiation between strong and weak absorbing features normalized to the transmitted energy. 2-micron double-pulsed IPDA lidar is best suited for atmospheric carbon dioxide measurements. In such case, the transmitter produces two successive laser pulses separated by short interval (200 microseconds), with low repetition rate (10Hz). Conventional laser energy monitors, based on thermal detectors, are suitable for low repetition rate single pulse lasers. Due to the short pulse interval in double-pulsed lasers, thermal energy monitors underestimate the total transmitted energy. This leads to measurement biases and errors in double-pulsed IPDA technique. The design and calibration of a 2-micron double-pulse laser energy monitor is presented. The design is based on a high-speed, extended range InGaAs pin quantum detectors suitable for separating the two pulse events. Pulse integration is applied for converting the detected pulse power into energy. Results are compared to a photo-electro-magnetic (PEM) detector for impulse response verification. Calibration included comparing the three detection technologies in single-pulsed mode, then comparing the pin and PEM detectors in double-pulsed mode. Energy monitor linearity will be addressed.

  2. Double-Pulsed 2-Micrometer Lidar Validation for Atmospheric CO2 Measurements

    NASA Technical Reports Server (NTRS)

    Singh, Upendra N.; Refaat, Tamer F.; Yu, Jirong; Petros, Mulugeta; Remus, Ruben

    2015-01-01

    A double-pulsed, 2-micron Integrated Path Differential Absorption (IPDA) lidar instrument for atmospheric carbon dioxide (CO2) measurements is successfully developed at NASA Langley Research Center (LaRC). Based on direct detection technique, the instrument can be operated on ground or onboard a small aircraft. Key features of this compact, rugged and reliable IPDA lidar includes high transmitted laser energy, wavelength tuning, switching and locking, and sensitive detection. As a proof of concept, the IPDA ground and airborne CO2 measurement and validation will be presented. IPDA lidar CO2 measurements ground validation were conducted at NASA LaRC using hard targets and a calibrated in-situ sensor. Airborne validation, conducted onboard the NASA B-200 aircraft, included CO2 plum detection from power stations incinerators, comparison to in-flight CO2 in-situ sensor and comparison to air sampling at different altitude conducted by NOAA at the same site. Airborne measurements, spanning for 20 hours, were obtained from different target conditions. Ground targets included soil, vegetation, sand, snow and ocean. In addition, cloud slicing was examined over the ocean. These flight validations were conducted at different altitudes, up to 7 km, with different wavelength controlled weighing functions. CO2 measurement results agree with modeling conducted through the different sensors, as will be discussed.

  3. 315mJ, 2-micrometers Double-Pulsed Coherent Differential Absorption Lidar Transmitter for Atmospheric CO2 Sensing

    NASA Technical Reports Server (NTRS)

    Yu, Jirong; Trieu, Bo; Bai, Yingxin; Koch, Grady; Chen, Songsheng; Petzar, Paul; Singh, Upendra N.; Kavaya, Michael J.; Beyon, Jeffrey

    2010-01-01

    The design of a double pulsed, injection seeded, 2-micrometer compact coherent Differential absorption Lidar (DIAL) transmitter for CO2 sensing is presented. This system is hardened for ground and airborne applications. The design architecture includes three continuous wave lasers which provide controlled on and off line seeding, injection seeded power oscillator and a single amplifier operating in double pass configuration. As the derivative a coherent Doppler wind lidar, this instrument has the added benefit of providing wind information. The active laser material used for this application is a Ho: Tm:YLF crystal operates at the eye-safe wavelength. The 3-meter long folded ring resonator produces energy of 130-mJ (90/40) with a temporal pulse length around 220 nanoseconds and 530 nanosecond pulses for on and off lines respectively. The separation between the two pulses is on the order of 200 microseconds. The line width is in the order of 2.5MHz and the beam quality has an M(sup 2) of 1.1 times diffraction limited beam. A final output energy for a pair of both on and off pulses as high as 315 mJ (190/125) at a repetition rate of 10 Hz is achieved. The operating temperature is set around 20 C for the pump diode lasers and 10 C for the rod. Since the laser design has to meet high-energy as well as high beam quality requirements, close attention is paid to the laser head design to avoid thermal distortion in the rod. A side-pumped configuration is used and heat is removed uniformly by passing coolant through a tube slightly larger than the rod to reduce thermal gradient. This paper also discusses the advantage of using a long upper laser level life time laser crystal for DIAL application. In addition issues related to injection seeding with two different frequencies to achieve a transform limited line width will be presented.

  4. High Energy Double-Pulsed Ho:Tm:YLF Laser Amplifier

    NASA Technical Reports Server (NTRS)

    Yu, Jirong; Braud, Alain; Petros, Mulugeta; Singh, Upendra N.

    2002-01-01

    A high energy double-pulsed Ho:Tm:YLF 2-micrometer laser amplifier has been demonstrated. 600 mJ per pulse pair under Q-switch operation is achieved with the gain of 4.4. This solid-state laser source can be used as lidar transmitter for multiple lidar applications such as coherent wind and carbon dioxide measurements.

  5. Column CO2 Measurement From an Airborne Solid-State Double-Pulsed 2-Micron Integrated Path Differential Absorption Lidar

    NASA Technical Reports Server (NTRS)

    Singh, U. N.; Yu, J.; Petros, M.; Refaat, T. F.; Remus, R.; Fay, J.; Reithmaier, K.

    2014-01-01

    NASA LaRC is developing and integrating a double-Pulsed 2-micron direct detection IPDA lidar for CO2 column measurement from an airborne platform. The presentation will describe the development of the 2-micrometers IPDA lidar system and present the airborne measurement of column CO2 and will compare to in-situ measurement for various ground target of different reflectivity.

  6. BLOCKING OSCILLATOR DOUBLE PULSE GENERATOR CIRCUIT

    DOEpatents

    Haase, J.A.

    1961-01-24

    A double-pulse generator, particuiarly a double-pulse generator comprising a blocking oscillator utilizing a feedback circuit to provide means for producing a second pulse within the recovery time of the blocking oscillator, is described. The invention utilized a passive network which permits adjustment of the spacing between the original pulses derived from the blocking oscillator and further utilizes the original pulses to trigger a circuit from which other pulses are initiated. These other pulses are delayed and then applied to the input of the blocking oscillator, with the result that the output from the oscillator circuit contains twice the number of pulses originally initiated by the blocking oscillator itself.

  7. Double pulse Thomson scattering system at RTP

    SciTech Connect

    Beurskens, M.N.; Barth, C.J.; Chu, C.C.; Donne, A.J.; Herranz, J.A.; Lopes Cardozo, N.J.; van der Meiden, H.J.; Pijper, F.J.

    1997-01-01

    In this article a double pulse multiposition Thomson scattering diagnostic, under construction at RTP, is discussed. Light from a double pulsed ruby laser (pulse separation: 10{endash}800 {mu}s, max. 2{times}12.5 J) is scattered by the free electrons of the tokamak plasma and relayed to a Littrow polychromator for spectral analysis. The spectrally resolved light is recorded by two ICCD detectors. Simulations show that the system sensitivity will be such that electron temperatures in the range of 100 eV{endash}7 keV can be determined with an accuracy as good as 2{percent}{endash}3{percent} for electron densities of 10{sup 20} m{sup {minus}3}, with a spatial resolution down to 2.6 mm. With this diagnostic the dynamics of small scale structures in the electron temperature profile will be studied. {copyright} {ital 1997 American Institute of Physics.}

  8. High-Energy 2-Micrometers Doppler Lidar for Wind Measurements

    NASA Technical Reports Server (NTRS)

    Koch, Grady J.; Beyon, Jeffrey Y.; Barnes, Bruce W.; Petros, Mulugeta; Yu, Jirong; Amzajerdian, Farzin; Kavaya, Michael J.; Singh, Upendra N.

    2006-01-01

    High-energy 2-micrometer wavelength lasers have been incorporated in a prototype coherent Doppler lidar to test component technologies and explore applications for remote sensing of the atmosphere. Design of the lidar is presented including aspects in the laser transmitter, receiver, photodetector, and signal processing. Calibration tests and sample atmospheric data are presented on wind and aerosol profiling.

  9. 2 Micrometers InAsSb Quantum-dot Lasers

    NASA Technical Reports Server (NTRS)

    Qiu, Yueming; Uhl, David; Keo, Sam

    2004-01-01

    InAsSb quantum-dot lasers near 2 micrometers were demonstrated in cw operation at room temperature with a threshold current density of 733 A,/cm(sup 2), output power of 3 mW/facet and a differential quantum efficiency of 13%.

  10. Effective desynchronization by means of double-pulse phase resetting

    NASA Astrophysics Data System (ADS)

    Tass, P. A.

    2001-01-01

    A double-pulse stimulation technique is presented here for the first time which makes it possible to effectively desynchronize a synchronized cluster of globally coupled phase oscillators in the presence of noise. The first, stronger pulse of the double pulse restarts the cluster independently of its initial dynamic state. The second, weaker pulse desynchronizes the cluster by hitting it in a vulnerable state. After the desynchronization the cluster tends to resynchronize since the incoherent state is unstable. Nevertheless, repeated administration of double pulses blocks the cluster's resynchronization. This approach can directly be applied to real data. Accordingly, a demand-controlled deep-brain double-pulse stimulation technique is suggested for the therapy of patients suffering from Parkinson's disease or essential tremor.

  11. Mean velocities measured with the double pulse technique

    NASA Astrophysics Data System (ADS)

    Nielsen, E.

    2004-10-01

    It was recently observed that double-pulse measurements of the mean velocities of a wide asymmetric spectrum are a function of the time lag between the pulses (Uspensky et al., 2004). Here we demonstrate that the observed relationship probably is influenced by the measurement technique in a way that is consistent with theoretical prediction. It is further shown that for small time lags the double pulse velocity is a good approximation to the mean Doppler velo-city.

  12. Effective desynchronization with bipolar double-pulse stimulation

    NASA Astrophysics Data System (ADS)

    Tass, Peter A.

    2002-09-01

    This paper is devoted to the desynchronizing effects of bipolar stimuli on a synchronized cluster of globally coupled phase oscillators. The bipolar pulses considered here are symmetrical and consist of a positive and a negative monopolar pulse. A bipolar single pulse with the right intensity and duration desynchronizes a synchronized cluster provided the stimulus is administered at a vulnerable initial phase of the cluster's order parameter. A considerably more effective desynchronization is achieved with a bipolar double pulse consisting of two qualitatively different bipolar pulses. The first bipolar pulse is stronger and resets the cluster, so that the second bipolar pulse, which follows after a constant delay, hits the cluster in a vulnerable state and desynchronizes it. A bipolar double pulse desynchronizes the cluster independently of the cluster's dynamical state at the beginning of the stimulation. The dynamics of the order parameter during a bipolar single pulse or a bipolar double pulse is different from the dynamics during a monopolar single pulse or a monopolar double pulse. Nevertheless, concerning their desynchronizing effects the monopolar and the bipolar stimuli are comparable, respectively. This is significant for applications where bipolar stimulation is required. For example, in medicine and physiology charge-balanced stimulation is typically necessary in order to avoid tissue damage. Based on the results presented here, demand-controlled bipolar double-pulse stimulation is suggested as a milder and more efficient therapy compared to the standard permanent high-frequency deep brain stimulation in neurological patients.

  13. Nucleosome organization of the yeast 2-micrometer DNA plasmid: a eukaryotic minichromosome.

    PubMed Central

    Nelson, R G; Fangman, W L

    1979-01-01

    The eukaryotic microorganism Saccharomyces cerevisiae contains 50-100 copies per cell of a circular plasmid called 2-micrometer DNA. The intracellular structure of these molecules, which represent about 4% of the total DNA, was examined by digestion of total cellular chromatin with micrococcal nuclease (nucleate 3'-oligonucleotidohydrolase, EC 3.1.31.1). Nuclease-resistant DNA fragments were fractionated by gel electrophoresis and 2-micrometer DNA sequences were detected by hybridization. The 2-micrometer and chromosomal DNA digestion patterns were very similar indicating that both types of DNA are condensed into nucleosomes. An analysis of these digestion patterns showed that the kinetics of digestion of 2-micrometer chromatin and total chromatin are similar and that both have the same nucleosome repeat length of about 165 base pairs. Native 2-micrometer plasmids were examined by zone sedimentation in sucrose gradients containing 0.15 M NaCl and were found to have a sedimentation constant of 75 S, about 3 times the sedimentation constant of protein-free 2-micrometer DNA. This sedimentation property is what would be expected for a 2-micrometer DNA minichromosome. We conclude that within the cell 2-micrometer DNA molecules are organized in a chromatin structure very similar to that of the yeast chromosomes. Images PMID:392520

  14. Physics of Double Pulse Irradiation of Targets For Proton Acceleration

    NASA Astrophysics Data System (ADS)

    Kerr, S.; Mo, M.; Masud, R.; Manzoor, L.; Tiedje, H.; Tsui, Y.; Fedosejevs, R.; Link, A.; Patel, P.; McLean, H.; Hazi, A.; Chen, H.; Ceurvorst, L.; Norreys, P.

    2016-10-01

    Experiments have been carried out on double-pulse irradiation of um-scale foil targets with varying preplasma conditions. Our experiment at the Titan Laser facility utilized two 700 fs, 1054 nm pulses, separated by 1 to 5 ps with a total energy of 100 J, and with 5-20% of the total energy contained within the first pulse. The proton spectra were measured with radiochromic film stacks and magnetic spectrometers. The prepulse energy was on the order of 10 mJ, which appears to have a moderating effect on the double pulse enhancement of proton beam. We have performed LSP PIC simulations to understand the double pulse enhancement mechanism, as well as the role of preplasma in modifying the interaction. A 1D parameter study was done to isolate various aspects of the interaction, while 2D simulations provide more detailed physical insight and a better comparison with experimental data. Work by the Univ. of Alberta was supported by the Natural Sciences and Engineering Research Council of Canada. Work by LLNL was performed under the auspices of U.S. DOE under contract DE-AC52-07NA27344.

  15. Characterizations of double pulsing in neutron multiplicity and coincidence counting systems

    NASA Astrophysics Data System (ADS)

    Koehler, Katrina E.; Henzl, Vladimir; Croft, Stephen S.; Henzlova, Daniela; Santi, Peter A.

    2016-10-01

    Passive neutron coincidence/multiplicity counters are subject to non-ideal behavior, such as double pulsing and dead time. It has been shown in the past that double-pulsing exhibits a distinct signature in a Rossi-alpha distribution, which is not readily noticed using traditional Multiplicity Shift Register analysis. However, it has been assumed that the use of a pre-delay in shift register analysis removes any effects of double pulsing. In this work, we use high-fidelity simulations accompanied by experimental measurements to study the effects of double pulsing on multiplicity rates. By exploiting the information from the double pulsing signature peak observable in the Rossi-alpha distribution, the double pulsing fraction can be determined. Algebraic correction factors for the multiplicity rates in terms of the double pulsing fraction have been developed. We discuss the role of these corrections across a range of scenarios.

  16. Double-pulse digital speckle pattern interferometry for vibration analysis

    NASA Astrophysics Data System (ADS)

    Zhang, Dazhi; Xue, Jingfeng; Chen, Lu; Wen, Juying; Wang, Jingjing

    2014-12-01

    The double-pulse Digital Speckle Pattern Interferometry (DSPI) in the laboratory is established. Two good performances have been achieved at the same time, which is uniform distribution of laser beam energy by space filter and recording two successive pictures by a CCD camera successfully. Then two-dimensional discrete orthogonal wavelet transform method is used for the process of filtering method. By using the DSPI, speckle pattern of a vibrated object is obtained with interval of (2~800)μs, and 3D plot of the transient vibration is achieved. Moreover, good agreements of the mode shapes and displacement are obtained by comparing with Laser Doppler Vibrometer (LDV) .

  17. Physics constraints on double-pulse LIA engineering

    SciTech Connect

    Ekdahl, Carl August Jr.

    2015-05-20

    The options for advanced-radiography double-pulse linear induction accelerators (LIA) under consideration naturally fall into three categories that differ by the number of cells required. Since the two major physics issues, beam breakup (BBU) and corkscrew, are also dependent on the number of cells, it may be useful for the decision process to review the engineering consequences of beam physics constraints for each class. The LIAs can be categorized three different ways, and this report compares the different categories based upon the physics of their beams.

  18. Status of the LIA-2. Double-pulse mode

    NASA Astrophysics Data System (ADS)

    Starostenko, D. A.; Akimov, A. V.; Bak, P. A.; Batazova, M. A.; Batrakov, A. M.; Boimelshtein, Yu. M.; Bolkhovityanov, D. Yu.; Eliseev, A. A.; Korepanov, A. A.; Kuznetsov, G. I.; Kulenko, Ya. V.; Logatchev, P. V.; Ottmar, A. V.; Pavlenko, A. V.; Pavlov, O. A.; Panov, A. N.; Pachkov, A. A.; Fatkin, G. A.; Akhmetov, A. R.; Kolesnikov, P. A.; Nikitin, O. A.; Petrov, D. V.

    2016-12-01

    The LIA-2 linear induction accelerator has been designed in the Budker Institute of Nuclear Physics as an electron-beam injector for a promising 20-MeV induction accelerator intended for tomography. Owing to the results of the first tests, it was decided to use the injector as an independent X-ray installation [1]. In 2014, the high-voltage power supply system of the LIA-2 was upgraded and tuned. The accelerator operates stably in the one-pulse mode at energies of up to 1.7 MeV; in the double-pulse mode it operates at energies of up to 1.5 MeV. The inhomogeneity in energy in each pulse does not exceed ±0.5%.

  19. Efficient Single-Frequency Thulium Doped Fiber Laser Near 2-micrometers

    NASA Technical Reports Server (NTRS)

    Geng, Jihong; Wu, Jianfeng; Jiang, Shibin; Yu, Jirong

    2007-01-01

    We demonstrate highly efficient diode-pumped single-frequency fiber laser with 35% slope efficiency and 50mW output power operating near 2 micrometers, which generated from a 2-cm long piece of highly Tm(3+)-doped germanate glass fiber pumped at 800nm.

  20. Investigation of phase explosion in aluminum induced by nanosecond double pulse technique

    NASA Astrophysics Data System (ADS)

    Jafarabadi, Marzieh Akbari; Mahdieh, Mohammad Hossein

    2015-08-01

    In this paper, the influence of double pulse technique on phase explosion threshold in laser ablation of an aluminum target is investigated. Single and double pulse laser ablation of aluminum target was performed by a high power Nd:YAG laser beam in ambient air. In the double pulse excitation, the two pulses were from a single laser source which separated by a delay time in the range of 5-20 ns. Measuring ablation depth and rate, the phase explosion threshold was estimated in double pulse configuration as well as in the single pulse regime. The results show that in comparison between single and double pulse regimes, the phase explosion threshold fluence is decreased in double pulse configuration. The lowest phase explosion threshold fluence of 0.9 J/cm2 was obtained at 5 ns delay time. The results also show that plasma shielding effect reduced crater depth at a laser fluence which depended on the laser ablation configuration (single pulse or double pulse). The reduction of crater depth occurs at lower laser fluences for double pulse regime.

  1. Ultrafast double-pulse ablation of fused silica

    SciTech Connect

    Chowdhury, Ihtesham H.; Xu Xianfan; Weiner, Andrew M.

    2005-04-11

    Ultrafast pump-probe experiments were used to study high-intensity ultrafast pulse-ablation dynamics in fused silica. Two laser pulses with varied time delay and pulse energy were used to irradiate fused silica samples and observe the transient reflectivity and transmissivity of the probe pulse. It was seen that the probe reflectivity initially increased due to the formation of free-electron plasma and then dropped to a low value within a period of about 10 ps caused by a rapid structural change at the surface. The time-resolved measurements of reflectivity and transmissivity were also related to atomic force microscopy measurements of the depth of the laser-ablated hole. It was seen that the depth peaked at zero delay between the pulses and decreased within a period of about 1 ps as the temporal separation between the pulses was increased caused by the screening by the plasma produced by the first pulse. When the temporal separation is about 100 ps or longer, evidence for melting and resolidification during double-pulse ablation was also observed in the form of ridges at the circumference of the ablated holes.

  2. Analysis of femtosecond quantum control mechanisms with colored double pulses

    SciTech Connect

    Vogt, Gerhard; Nuernberger, Patrick; Selle, Reimer; Dimler, Frank; Brixner, Tobias; Gerber, Gustav

    2006-09-15

    Fitness landscapes based on a limited number of laser pulse shape parameters can elucidate reaction pathways and can help to find the underlying control mechanism of optimal pulses determined by adaptive femtosecond quantum control. In a first experiment, we employ colored double pulses and systematically scan both the temporal subpulse separation and the relative amplitude of the two subpulses to acquire fitness landscapes. Comparison with results obtained from a closed-loop experiment demonstrates the capability of fitness landscapes for the revelation of possible control mechanisms. In a second experiment, using transient absorption spectroscopy, we investigate and compare the dependence of the excitation efficiency of the solvated dye molecule 5,5{sup '}-dichloro-11-diphenylamino-3,3{sup '}-diethyl-10,12-ethylene thiatricarbocyanine perchlorate (IR140) on selected pulse shapes in two parametrizations. The results show that very different pulse profiles can be equivalently adequate to maximize a given control objective. Fitness landscapes thus provide valuable information about different pathways along which a molecular system can be controlled with shaped laser pulses.

  3. Single And Double Pulse Irradiation And Comparison With Experimental Results

    SciTech Connect

    Fornarini, L.; Fantoni, R.; Colao, F.; Santagata, A.; Teghil, R.

    2009-09-27

    A theoretical model of laser ablation has been previously developed and applied to Laser Induced Breakdown Spectroscopy (LIBS) analysis of bronzes with the aim to improve quantitative results and to focus on problems arising in the interpretation of experimental data. The model describes laser-solid matter interaction, plume expansion, plasma formation and laser-plasma interaction. A two temperature approach has been also introduced to take into account the initial temperature dynamics of the alloy surface upon ultra-short laser irradiation. We examined various target compositions, typical of archaeological artworks, and different laser characteristics such as wavelength (355 nm, 530 nm, 1064 nm) and pulse duration (8 ns, 250 fs). In this work, the model has been extended to simulate double pulse LIBS configuration in order to clarify the mechanism involved in the process and for better interpreting the experimental data. Plasma composition, relevant parameters (temperature, electron density) and their kinetic evolutions have been measured. Results have been compared with the simulation obtained using the same irradiation conditions and set of targets.

  4. Proposal and simulation of differential double-pulse pair Brillouin optical time-domain analysis

    NASA Astrophysics Data System (ADS)

    Tang, Jianguan; Luo, Wenping; Chen, Beiqing; Guo, Huiyong; Zhang, Cui

    2013-09-01

    A differential double-pulse pair Brillouin optical time-domain analysis (DDP-BOTDA) combined with the double-pulsed technique and the differential pulse-width pair technique is proposed and simulated to detect small temperature and strain changes. Using a symmetrical double-pulse pair, the system can detect small Brillouin shift with high spatial resolution and large dynamic range. Sub-meter spatial resolution is decided by the difference between the pulse-width and the peak and valley of the spectrum which is derived from differential pump depletion signals, and detectable Brillouin shift is less than 1 MHz.

  5. Drilling of aluminum and copper films with femtosecond double-pulse laser

    NASA Astrophysics Data System (ADS)

    Wang, Qinxin; Luo, Sizuo; Chen, Zhou; Qi, Hongxia; Deng, Jiannan; Hu, Zhan

    2016-06-01

    Aluminum and copper films are drilled with femtosecond double-pulse laser. The double-pulse delay is scanned from -75 ps to 90 ps. The drilling process is monitored by recording the light transmitted through the sample, and the morphology of the drilled holes is analyzed by optical microscopy. It is found that, the breakthrough time, the hole evolution during drilling, the redeposited material, the diameters of the redeposited area and the hole, change as functions of double-pulse delay, and are different for the two metals. Along the double-pulse delay axis, three different time constants are observed, a slow one of a few tens of picoseconds, a fast one of a few picoseconds, and an oscillation pattern. Results are discussed based on the mechanisms of plasma shielding, electron-phonon coupling, strong coupling of laser with liquid phase, oxidation of aluminum, laser induced temperature and pressure oscillations, and the atomization of plume particles.

  6. Airborne Double Pulsed 2-Micron IPDA Lidar for Atmospheric CO2 Measurement

    NASA Technical Reports Server (NTRS)

    Yu, Jirong; Petros, Mulugeta; Refaat, Tamer; Singh, Upendra

    2015-01-01

    We have developed an airborne 2-micron Integrated Path Differential Absorption (IPDA) lidar for atmospheric CO2 measurements. The double pulsed, high pulse energy lidar instrument can provide high-precision CO2 column density measurements.

  7. Conductivity depth imaging of Airborne Electromagnetic data with double pulse transmitting current based on model fusion

    NASA Astrophysics Data System (ADS)

    Li, Jing; Dou, Mei; Lu, Yiming; Peng, Cong; Yu, Zining; Zhu, Kaiguang

    2017-01-01

    The airborne electromagnetic (AEM) systems have been used traditionally in mineral exploration. Typically the system transmits a single pulse waveform to detect conductive anomaly. Conductivity-depth imaging (CDI) of data is generally applied in identifying conductive targets. A CDI algorithm with double-pulse transmitting current based on model fusion is developed. The double-pulse is made up of a half-sine pulse of high power and a trapezoid pulse of low power. This CDI algorithm presents more shallow information than traditional CDI with a single pulse. The electromagnetic response with double-pulse transmitting current is calculated by linear convolution based on forward modeling. The CDI results with half-sine and trapezoid pulse are obtained by look-up table method, and the two results are fused to form a double-pulse conductivity-depth imaging result. This makes it possible to obtain accurate conductivity and depth. Tests on synthetic data demonstrate that CDI algorithm with double-pulse transmitting current based on model fusion maps a wider range of conductivities and does a better job compared with CDI with a single pulse transmitting current in reflecting the whole geological conductivity changes.

  8. Laser energy monitor for double-pulsed 2-μm IPDA lidar application

    NASA Astrophysics Data System (ADS)

    Refaat, Tamer F.; Petros, Mulugeta; Remus, Ruben; Yu, Jirong; Singh, Upendra N.

    2014-10-01

    Integrated path differential absorption (IPDA) lidar is a remote sensing technique for monitoring different atmospheric species. The technique relies on wavelength differentiation between strong and weak absorbing features normalized to the transmitted energy. 2-μm double-pulsed IPDA lidar is best suited for atmospheric carbon dioxide measurements. In such case, the transmitter produces two successive laser pulses separated by short interval (200 μs), with low repetition rate (10Hz). Conventional laser energy monitors, based on thermal detectors, are suitable for low repetition rate single pulse lasers. Due to the short pulse interval in double-pulsed lasers, thermal energy monitors underestimate the total transmitted energy. This leads to measurement biases and errors in double-pulsed IPDA technique. The design and calibration of a 2-μm double-pulse laser energy monitor is presented. The design is based on a highspeed, extended range InGaAs pin quantum detectors suitable for separating the two pulse events. Pulse integration is applied for converting the detected pulse power into energy. Results are compared to a photo-electro-magnetic (PEM) detector for impulse response verification. Calibration included comparing the three detection technologies in singlepulsed mode, then comparing the pin and PEM detectors in double-pulsed mode. Energy monitor linearity will be addressed.

  9. Double-pulse standoff laser-induced breakdown spectroscopy for versatile hazardous materials detection

    NASA Astrophysics Data System (ADS)

    Gottfried, Jennifer L.; De Lucia, Frank C.; Munson, Chase A.; Miziolek, Andrzej W.

    2007-12-01

    We have developed a double-pulse standoff laser-induced breakdown spectroscopy (ST-LIBS) system capable of detecting a variety of hazardous materials at tens of meters. The use of a double-pulse laser improves the sensitivity and selectivity of ST-LIBS, especially for the detection of energetic materials. In addition to various metallic and plastic materials, the system has been used to detect bulk explosives RDX and Composition-B, explosive residues, biological species such as the anthrax surrogate Bacillus subtilis, and chemical warfare simulants at 20 m. We have also demonstrated the discrimination of explosive residues from various interferents on an aluminum substrate.

  10. Effect of frequency-doubling pulse Nd:YAG laser on microbial mutation

    NASA Astrophysics Data System (ADS)

    Zhao, Yansheng; Wang, Luyan; Zheng, Heng; Yin, Hongping; Chen, Xiangdong; Tan, Zheng; Wu, Wutong

    1999-09-01

    We are going to report the mutagenic effect of frequency-doubling pulse Nd:YAG laser (532 nm) on microbe. After irradiation with pulse laser, mutants of abscisic acid producing strains and erythromycin producing strains were obtained, one of which could produce 62.1% and 57% more products than control, respectively. In the study of mutagenization of Spirulina platensis caused by pulse laser, we selected a high photosynthetic strains, with improved productivity of protein and exocellular ploysaccharides of 12% and 246%, respectively. The experimental results indicate that frequency-doubling pulse laser (532 nm) is a potential new type of physical mutagenic factor.

  11. Optimally enhanced optical emission in laser-induced air plasma by femtosecond double-pulse

    SciTech Connect

    Chen, Anmin; Li, Suyu; Li, Shuchang; Jiang, Yuanfei; Ding, Dajun; Shao, Junfeng; Wang, Tingfeng; Huang, Xuri; Jin, Mingxing

    2013-10-15

    In laser-induced breakdown spectroscopy, a femtosecond double-pulse laser was used to induce air plasma. The plasma spectroscopy was observed to lead to significant increase of the intensity and reproducibility of the optical emission signal compared to femtosecond single-pulse laser. In particular, the optical emission intensity can be optimized by adjusting the delay time of femtosecond double-pulse. An appropriate pulse-to-pulse delay was selected, that was typically about 50 ps. This effect can be especially advantageous in the context of femtosecond laser-induced breakdown spectroscopy, plasma channel, and so on.

  12. Double-Pulsed 2-micron Laser Transmitter for Multiple Lidar Applications

    NASA Technical Reports Server (NTRS)

    Singh, Upendra N.; Yu, Jirong

    2002-01-01

    A high energy double-pulsed Ho:Tm:YLF 2-micron laser amplifier has been demonstrated. 600 mJ per pulse pair under Q-switch operation is achieved with the gain of 4.4. This solid-state laser source can be used as lidar transmitter for multiple lidar applications such as coherent wind and carbon dioxide measurements.

  13. Airborne 2-Micron Double Pulsed Direct Detection IPDA Lidar for Atmospheric CO2 Measurement

    NASA Technical Reports Server (NTRS)

    Yu, Jirong; Petros, Mulugeta; Refaat, Tamer F.; Reithmaier, Karl; Remus, Ruben; Singh, Upendra; Johnson, Will; Boyer, Charlie; Fay, James; Johnston, Susan; Murchison, Luke

    2015-01-01

    An airborne 2-micron double-pulsed Integrated Path Differential Absorption (IPDA) lidar has been developed for atmospheric CO2 measurements. This new 2-miron pulsed IPDA lidar has been flown in spring of 2014 for total ten flights with 27 flight hours. It provides high precision measurement capability by unambiguously eliminating contamination from aerosols and clouds that can bias the IPDA measurement.

  14. Addition of HCl to the double-pulse copper chloride laser

    NASA Technical Reports Server (NTRS)

    Vetter, A. A.; Nerheim, N. M.

    1977-01-01

    Addition of small amounts of hydrogen chloride to the buffer gas of a double-pulse CuCl laser causes an increase in the production of copper atoms in the ground state. A maximum laser energy increase of 15% was observed and the span of delay times for which laser action occurred increased.

  15. Airborne 2-Micron Double Pulsed Direct Detection IPDA Lidar for Atmospheric CO2 Measurement

    NASA Astrophysics Data System (ADS)

    Yu, Jirong; Petros, Mulugeta; Refaat, Tamer; Reithmaier, Karl; Remus, Ruben; Singh, Upendra; Johnson, Will; Boyer, Charlie; Fay, James; Johnston, Susan; Murchison, Luke

    2016-06-01

    An airborne 2-micron double-pulsed Integrated Path Differential Absorption (IPDA) lidar has been developed for atmospheric CO2 measurements. This new instrument has been flown in spring of 2014 for a total of ten flights with 27 flight hours. This IPDA lidar provides high precision measurement capability by unambiguously eliminating contamination from aerosols and clouds that can bias the results.

  16. Experimental study on double-pulse laser ablation of steel upon multiple parallel-polarized ultrashort-pulse irradiations

    NASA Astrophysics Data System (ADS)

    Schille, Joerg; Schneider, Lutz; Kraft, Sebastian; Hartwig, Lars; Loeschner, Udo

    2016-07-01

    In this paper, double-pulse laser processing is experimentally studied with the aim to explore the influence of ultrashort pulses with very short time intervals on ablation efficiency and quality. For this, sequences of 50 double pulses of varied energy and inter-pulse delay, as adjusted between 400 fs and 18 ns by splitting the laser beam into two optical paths of different length, were irradiated to technical-grade stainless steel. The depth and the volume of the craters produced were measured in order to evaluate the efficiency of the ablation process; the crater quality was analyzed by SEM micrographs. The results obtained were compared with craters produced with sequences of 50 single pulses and energies equal to the double pulse. It is demonstrated that double-pulse processing cannot exceed the ablation efficiency of single pulses of optimal fluence, but the ablation crater surface formed smoother if inter-pulse delay was in the range between 10 ns and 18 ns. In addition, the influence of pulse duration and energy distribution between the individual pulses of the double pulse on ablation was studied. For very short inter-pulse delay, no significant effect of energy variation within the double pulse on removal rate was found, indicating that the double pulse acts as a big single pulse of equal energy. Further, the higher removal efficiency was achieved when double-pulse processing using femtosecond pulses instead of picosecond pulses.

  17. Gain property on supersonic flow TEA-CO2 laser in double-pulse operation

    NASA Astrophysics Data System (ADS)

    Imada, Go; Tateishi, Motoki; Suzuki, Masataro; Masuda, Wataru

    2012-01-01

    In order to contribute toward the development of a highly-repetitive TEA-CO2 laser, small-signal gains are measured for a double-pulse operation of a laser medium in a supersonic flow at a Mach number of 2. It is found that the time interval of the double-pulse operation should be longer than 60 μs in order to have the gain of the subsequent pulse comparable to that of the preceding one. It is also found that the gain is enhanced with a low-temperature laser medium owing to the concentration of excited CO2 molecules in the state of a specific rotational quantum number. The results suggest the possibility that the output power of a TEA-CO2 laser device can be increased by utilizing the supersonic flow.

  18. Modeling double pulsing of ion beams for HEDP target heating experiments

    NASA Astrophysics Data System (ADS)

    Veitzer, Seth; Barnard, John; Stoltz, Peter; Henestroza, Enrique

    2008-04-01

    Recent research on direct drive targets using heavy ion beams suggests optimal coupling will occur when the energy of the ions increases over the course of the pulse. In order to experimentally explore issues involving the interaction of the beam with the outflowing blowoff from the target, double pulse experiments have been proposed whereby a first pulse heats a planar target producing an outflow of material, and a second pulse (˜10 ns later) of higher ion energy (and hence larger projected range) interacts with this outflow before reaching and further heating the target. We report here results for simulations of double pulsing experiments using HYDRA for beam and target parameters relevant to the proposed Neutralized Drift Compression Experiment (NDCX) II at LBNL.

  19. Airborne 2-Micron Double-Pulsed Integrated Path Differential Absorption Lidar for Column CO2 Measurement

    NASA Technical Reports Server (NTRS)

    Singh, Upendra N.; Yu, Jirong; Petros, Mulugeta; Refaat, Tamer F.; Remus, Ruben G.; Fay, James J.; Reithmaier, Karl

    2014-01-01

    Double-pulse 2-micron lasers have been demonstrated with energy as high as 600 millijouls and up to 10 Hz repetition rate. The two laser pulses are separated by 200 microseconds and can be tuned and locked separately. Applying double-pulse laser in DIAL system enhances the CO2 measurement capability by increasing the overlap of the sampled volume between the on-line and off-line. To avoid detection complicity, integrated path differential absorption (IPDA) lidar provides higher signal-to-noise ratio measurement compared to conventional range-resolved DIAL. Rather than weak atmospheric scattering returns, IPDA rely on the much stronger hard target returns that is best suited for airborne platforms. In addition, the IPDA technique measures the total integrated column content from the instrument to the hard target but with weighting that can be tuned by the transmitter. Therefore, the transmitter could be tuned to weight the column measurement to the surface for optimum CO2 interaction studies or up to the free troposphere for optimum transport studies. Currently, NASA LaRC is developing and integrating a double-Pulsed 2-micron direct detection IPDA lidar for CO2 column measurement from an airborne platform. The presentation will describe the development of the 2-micron IPDA lidar system and present the airborne measurement of column CO2 and will compare to in-situ measurement for various ground target of different reflectivity.

  20. Airborne 2-micron double-pulsed integrated path differential absorption lidar for column CO2 measurement

    NASA Astrophysics Data System (ADS)

    Singh, Upendra N.; Yu, Jirong; Petros, Mulugeta; Refaat, Tamer F.; Remus, Ruben G.; Fay, James J.; Reithmaier, Karl

    2014-10-01

    Double-pulse 2-micron lasers have been demonstrated with energy as high as 600 mJ and up to 10 Hz repetition rate. The two laser pulses are separated by 200 µs and can be tuned and locked separately. Applying double-pulse laser in DIAL system enhances the CO2 measurement capability by increasing the overlap of the sampled volume between the on-line and off-line. To avoid detection complicity, integrated path differential absorption (IPDA) lidar provides higher signal-to-noise ratio measurement compared to conventional range-resolved DIAL. Rather than weak atmospheric scattering returns, IPDA rely on the much stronger hard target returns that is best suited for airborne platforms. In addition, the IPDA technique measures the total integrated column content from the instrument to the hard target but with weighting that can be tuned by the transmitter. Therefore, the transmitter could be tuned to weight the column measurement to the surface for optimum CO2 interaction studies or up to the free troposphere for optimum transport studies. Currently, NASA LaRC is developing and integrating a double-Pulsed 2-µm direct detection IPDA lidar for CO2 column measurement from an airborne platform. The presentation will describe the development of the 2-μm IPDA lidar system and present the airborne measurement of column CO2 and will compare to in-situ measurement for various ground target of different reflectivity.

  1. Double-Pulse Two-Micron IPDA Lidar Simulation for Airborne Carbon Dioxide Measurements

    NASA Technical Reports Server (NTRS)

    Refaat, Tamer F.; Singh, Upendra N.; Yu, Jirong; Petros, Mulugeta

    2015-01-01

    An advanced double-pulsed 2-micron integrated path differential absorption lidar has been developed at NASA Langley Research Center for measuring atmospheric carbon dioxide. The instrument utilizes a state-of-the-art 2-micron laser transmitter with tunable on-line wavelength and advanced receiver. Instrument modeling and airborne simulations are presented in this paper. Focusing on random errors, results demonstrate instrument capabilities of performing precise carbon dioxide differential optical depth measurement with less than 3% random error for single-shot operation from up to 11 km altitude. This study is useful for defining CO2 measurement weighting, instrument setting, validation and sensitivity trade-offs.

  2. Double-pulse induced harmonic generation in laser-produced plasmas

    NASA Astrophysics Data System (ADS)

    Ganeev, Rashid A.; Suzuki, Masayuki; Yoneya, Shin; Kuroda, Hiroto

    2015-12-01

    We report the studies of the metals, non-metals, powders, and nanoparticles as the targets for laser ablation induced high-order harmonic generation of ultrashort pulses using the double-pulse technique. The proposed technique demonstrates the attractiveness as the method for the studies of the high-order nonlinear optical properties of various materials. The comparative analysis of the harmonic generation using different targets showed that the species allowing easier ablation (powders, nanoparticles) produce stronger harmonic yield in the extreme ultraviolet range.

  3. Opacity and atomic analysis of double pulse laser ablated Li plasma

    NASA Astrophysics Data System (ADS)

    Sivakumaran, V.; Joshi, H. C.; Kumar, Ajai

    2014-09-01

    Opacity effects for neutral and ionic emission lines of lithium have been investigated by Atomic Data Analysis Structure (ADAS). Line ratios and opacity corrected photon emissivity coefficients are calculated over a wide range of electron temperatures and densities. The experimentally measured temporal evolution of the line profiles of the over dense Li plasma formed in the double pulse laser ablation experiment have been explained using the ADAS analysis and the plasma parameters of the plasma plume under consideration have been estimated. These results could be projected as a diagnostic tool to estimate plasma parameters of an over dense lithium plasma.

  4. A compact field-portable double-pulse laser system to enhance laser induced breakdown spectroscopy

    NASA Astrophysics Data System (ADS)

    Li, Shuo; Liu, Lei; Yan, Aidong; Huang, Sheng; Huang, Xi; Chen, Rongzhang; Lu, Yongfeng; Chen, Kevin

    2017-02-01

    This paper reports the development of a compact double-pulse laser system to enhance laser induced breakdown spectroscopy (LIBS) for field applications. Pumped by high-power vertical-surface emitting lasers, the laser system that produces 16 ns pulse at 12 mJ/pulse with total weight less than 10 kg is developed. The inter-pulse delay can be adjusted from 0 μ s with 0.5 μ s increment. Several LIBS experiments were carried out on NIST standard aluminum alloy samples. Comparing with the single-pulse LIBS, up to 9 times enhancement in atomic emission line was achieved with continuum background emission reduced by 70%. This has led to up to 10 times improvement in the limit of detection. Signal stability was also improved by 128% indicating that a more robust and accurate LIBS measurement can be achieved using a compact double-pulse laser system. This paper presents a viable and field deployable laser tool to dramatically improve the sensitivity and applicability of LIBS for a wide array of applications.

  5. Direct surface engineering of silicon nanoparticles prepared by collinear double-pulse ns laser ablation

    NASA Astrophysics Data System (ADS)

    Mahdieh, M. H.; Momeni, A.

    2017-01-01

    In this paper we study the photoluminescence properties of colloidal silicon nanoparticles (Si NPs) in distilled water, with the aim of clarifying the role of surface characteristics on the emission properties. We will show that double-pulse ns laser ablation (DPLA) of a silicon target in water with different inter-pulse delay times of i.e. 5 and 10 ns can result in production of colloidal Si NPs with different PL emission intensities at the visible spectral range of 550-650 nm. The results reveal that DPLA process at the different delay times can induce different oxide related surface characteristics on the Si NPs through the direct surface engineering of the nanoparticles. A detailed analysis of the PL emissions using the stochastic quantum confinement model explained that the different emission behaviors of the colloids are associated with the oxide-related surface states which are contributed as radiative centers in the PL process.

  6. A comparative study of single and double pulse of laser induced breakdown spectroscopy of silver

    SciTech Connect

    Rashid, Babar; Ahmed, Rizwan; Ali, Raheel; Baig, M. A.

    2011-07-15

    We present a comparative study of the collinear and orthogonal pre-ablation dual pulse configurations of laser induced breakdown spectroscopy (LIBS) of silver using Nd:YAG lasers. The effect of the inter-pulse delay and the ratio of the laser pulse energies on the signal intensity enhancement for both the dual pulse configurations have been investigated. Using the first laser at 532 nm and second laser at 1064 nm delayed by 5 {mu}s, we achieved nearly 2 times signal enhancement in the collinear double-pulsed configuration and nearly 12 times in the pre-ablation orthogonal configuration as compared to SP LIBS. It is ascertained that at the optimized value of the inter-pulse delay between the two lasers, the intensity ratio of the neutral silver lines follows the local thermo dynamical equilibrium (LTE) condition and it is also in excellent agreement with that of the relative transitions probabilities ratio listed in the NIST data base.

  7. Double-Pulse Two-micron LPDA Lidar Simulation for Airborne Carbon Dioxide Measurements

    NASA Astrophysics Data System (ADS)

    Refaat, Tamer F.; Singh, Upendra N.; Yu, Jirong; Petros, Mulugeta

    2016-06-01

    An advanced double-pulse 2-μm integrated path differential absorption lidar has been developed at NASA Langley Research Center for measuring atmospheric carbon dioxide. The instrument utilizes a state-of-the-art 2-μm laser transmitter with tunable on-line wavelength and advanced receiver. Instrument modeling and airborne simulations are presented in this paper. Focusing on random errors, results demonstrate instrument capabilities of performing precise carbon dioxide differential optical depth measurement with less than 3% random error for single-shot operation up to 11 km altitude. This study is useful for defining CO2 measurement weighting function for adaptive targeting, instrument setting, validation and sensitivity trade-offs.

  8. Development of double-pulse lasers ablation system for generating gold ion source under applying an electric field

    NASA Astrophysics Data System (ADS)

    Khalil, A. A. I.

    2015-12-01

    Double-pulse lasers ablation (DPLA) technique was developed to generate gold (Au) ion source and produce high current under applying an electric potential in an argon ambient gas environment. Two Q-switched Nd:YAG lasers operating at 1064 and 266 nm wavelengths are combined in an unconventional orthogonal (crossed-beam) double-pulse configuration with 45° angle to focus on a gold target along with a spectrometer for spectral analysis of gold plasma. The properties of gold plasma produced under double-pulse lasers excitation were studied. The velocity distribution function (VDF) of the emitted plasma was studied using a dedicated Faraday-cup ion probe (FCIP) under argon gas discharge. The experimental parameters were optimized to attain the best signal to noise (S/N) ratio. The results depicted that the VDF and current signals depend on the discharge applied voltage, laser intensity, laser wavelength and ambient argon gas pressure. A seven-fold increases in the current signal by increasing the discharge applied voltage and ion velocity under applying double-pulse lasers field. The plasma parameters (electron temperature and density) were also studied and their dependence on the delay (times between the excitation laser pulse and the opening of camera shutter) was investigated as well. This study could provide significant reference data for the optimization and design of DPLA systems engaged in laser induced plasma deposition thin films and facing components diagnostics.

  9. Double-pulse laser-induced breakdown spectroscopy for trace element analysis in sintered iron oxide ceramics

    NASA Astrophysics Data System (ADS)

    Heilbrunner, H.; Huber, N.; Wolfmeir, H.; Arenholz, E.; Pedarnig, J. D.; Heitz, J.

    2012-01-01

    Double-pulse laser-induced breakdown spectroscopy (LIBS) is an emerging technique for accurate compositional analysis of many different materials. We present a systematic study of collinear double-pulse LIBS for analysis of the trace and side elements boron, manganese, copper, aluminum, titanium, silicon, chromium, nickel, potassium, and calcium in sintered iron oxide targets. The samples were ablated in air by single-pulse and double-pulse Nd:YAG laser radiation (6 ns pulse duration, laser wavelength of 532 nm) and spectra were recorded with an Echelle spectrometer equipped with an ICCD camera. We investigated the evolution of atomic and ionic line emission intensities for different interpulse delay times between the laser pulses (from 100 ns to 50 μs) and gate delays after the second laser pulse. We also varied the energy partition between the first and second laser pulse and the size of the irradiated spot at the sample surface. For the trace and side elements, we observed double-pulse LIBS signals that were enhanced as compared to single-pulse measurements depending on the interpulse delay time, the energy partition between the pulses, and the spot size. For the elements boron, copper, aluminum, titanium, chromium, potassium, and calcium limits of detection below 10 ppm were achieved.

  10. Organic Scintillators in Nonproliferation Applications With a Hybridized Double-Pulse Rejection Technique

    NASA Astrophysics Data System (ADS)

    Bourne, Mark Mitchell

    Alternative detection technologies are crucial to meeting demand for neutron detectors, for the current production of He-3, which has been the classical neutron choice, is insufficient. Organic scintillators are a strong candidate as a He-3 alternative due to their high efficiency, fast timing properties, and capabilities for separately identifying gamma-rays and neutrons through pulse shape discrimination (PSD). However, the use of organic scintillators in environments with numerous gamma rays can be limited because overlapping gamma-ray events can be misclassified as neutron events during PSD. To solve this problem, a new, hybridized double-pulse cleaning technique, consisting of three separate cleaning algorithms, was developed. The technique removes gamma-ray double pulses while preserving as many neutron pulses as possible. This technique was applied to separate experiments of Cf-252 and a gamma-ray source when measuring at a 100-kHz count rate and a field of 1000 incident gamma rays per incident neutron. It was found that stilbene scintillators were capable of intrinsic neutron efficiencies between 15-19% when measuring bare Cf-252 and 13-17% when exposed to the gamma-ray field. Misclassification rates ranged from 10-6-10-5, a factor-of-5 better than both the EJ-309 liquid and BB3-5 plastic. Next, plutonium experiments were performed with stilbene to determine which cleaning algorithm was best for each sample. A clear correlation was found that related the correct method of cleaning to the measured gamma ray-to-neutron ratio. When the measured gamma ray-to-neutron ratio is 10 or below, the template cleaning algorithm is preferred, while the fractional and hybrid cleaning algorithms are preferred when the gamma ray-to-neutron ratio is 100 or greater. Discriminating neutron sources such as Cf-252 or AmLi from SNM samples such as plutonium is a top priority in nonproliferation. We demonstrate that time-correlated experiments, utilizing both PSD-capable plastic

  11. Measurements of deuterium retention and surface elemental composition with double pulse laser induced breakdown spectroscopy

    NASA Astrophysics Data System (ADS)

    Almaviva, Salvatore; Caneve, Luisa; Colao, Francesco; Maddaluno, Giorgio; Krawczyk, Natalia; Czarnecka, Agata; Gasior, Pawel; Kubkowska, Monica; Lepek, Michal

    2016-02-01

    Estimating the tritium amount retained in the plasma facing components and their surface layer composition is of crucial importance for ITER. Laser-induced breakdown spectroscopy (LIBS) is an analytical technique suitable for in situ measurements of both these quantities. For improving its sensitivity, the double pulse (DP) variant can be used, instead of the standard single pulse (SP). In this work Mo samples coated with 1.5-1.8 μm thick W-Al (as a proxy for Be) mixed layer, with co-deposited deuterium were analyzed under vacuum (˜5 × 10-5 mbar) by SP and DP LIBS, showing enhancement of the spectral intensity for the latter. Calibration free method was applied to the LIBS data for getting the elemental concentration of W and Al. Results are in satisfactory agreement with those obtained from preliminary, ion beam analysis measurements. Deuterium concentration was tentatively estimated by accounting for the intensity ratio between Dα and nearby WI lines.

  12. Characterization and mechanism of glass microwelding by double-pulse ultrafast laser irradiation.

    PubMed

    Wu, Sizhu; Wu, Dong; Xu, Jian; Hanada, Yasutaka; Suganuma, Ryo; Wang, Haiyu; Makimura, Testuya; Sugioka, Koji; Midorikawa, Katsumi

    2012-12-17

    We investigated the physical mechanism of high-efficiency glass microwelding by double-pulse ultrafast laser irradiation by measuring the dependences of the size of the heat-affected zone and the bonding strength on the delay time between the two pulses for delay time up to 80 ns. The size of the heat-affected zone increases rapidly when the delay time is increased from 0 to 12.5 ps. It then decreases dramatically when the delay time is further increased to 30 ps. It has a small peak around 100 ps. For delay time up to 40 ns, the size of the heat-affected zone exceeds that for a delay time of 0 ps, whereas for delay time over 60 ps, it becomes smaller than that for a delay time of 0 ps. The bonding strength exhibits the same tendency. The underlying physical mechanism is discussed in terms of initial electron excitation by the first pulse and subsequent excitation by the second pulse: specifically, the first pulse induces multiphoton ionization or tunneling ionization, while the second pulse induces electron heating or avalanche ionization or the second pulse is absorbed by the localized state. Transient absorption of glass induced by the ultrafast laser pulse was analyzed by an ultrafast pump-probe technique. We found that the optimum pulse energy ratio is unity. These results provide new insights into high-efficiency ultrafast laser microwelding of glass and suggest new possibilities for further development of other ultrafast laser processing techniques.

  13. STARE velocities: 3. Double-pulse and multi-pulse measurements

    NASA Astrophysics Data System (ADS)

    Uspensky, M.; Koustov, A.; Sofieva, V.; Amm, O.; Kauristie, K.; Schmidt, W.; Nielsen, E.; Pulkkinen, T.; Pellinen, R.; Pirjola, R.

    The STARE coherent radars are a powerfull instrument for studying the auroral zone electrodynamics, first of all with respect to plasma convection. For decades, the radars have been using the double-pulse (DP) technique to measure the velocity. Recently, the multi-pulse (MP) scheme has been implemented. The detailed comparisons (Uspensky et al., 2003, 2004) between EISCAT and STARE MP measurements showed a good performance of the MP scheme for convection estimates, contrary to the known difficulties of the DP method. In the present study we consider differences in the velocity estimates by the MP and DP schemes in order to evaluate the uncertainties of the convection predictions by the DP scheme. We confirm previous warnings by Schlegel et al. (1986) and Schlegel and Thomas (1988) that the STARE DP scheme with fixed pulse separation can give a systematic error in the velocity estimate. We show that the DP velocities are typically smaller than the MP velocities, especially for large flow angle observations in the afternoon/evening sector. We also report occasional cases of small DP velocity overestimations. It is argued that the observed differences between DP and MP velocities originate from a minor, but not negligible, correlation between the signals coming from the main and aliasing volumes of the DP scheme particularly under the condition of broad backscatter spectra.

  14. Signal enhancement in collinear double-pulse laser-induced breakdown spectroscopy applied to different soils

    NASA Astrophysics Data System (ADS)

    Nicolodelli, Gustavo; Senesi, Giorgio Saverio; Romano, Renan Arnon; de Oliveira Perazzoli, Ivan Luiz; Milori, Débora Marcondes Bastos Pereira

    2015-09-01

    Laser-induced breakdown spectroscopy (LIBS) is a well-known consolidated analytical technique employed successfully for the qualitative and quantitative analysis of solid, liquid, gaseous and aerosol samples of very different nature and origin. Several techniques, such as dual-pulse excitation setup, have been used in order to improve LIBS's sensitivity. The purpose of this paper was to optimize the key parameters as excitation wavelength, delay time and interpulse, that influence the double pulse (DP) LIBS technique in the collinear beam geometry when applied to the analysis at atmospheric air pressure of soil samples of different origin and texture from extreme regions of Brazil. Additionally, a comparative study between conventional single pulse (SP) LIBS and DP LIBS was performed. An optimization of DP LIBS system, choosing the correct delay time between the two pulses, was performed allowing its use for different soil types and the use of different emission lines. In general, the collinear DP LIBS system improved the analytical performances of the technique by enhancing the intensity of emission lines of some elements up to about 5 times, when compared with conventional SP-LIBS, and reduced the continuum emission. Further, the IR laser provided the best performance in re-heating the plasma.

  15. Linear track estimation using double pulse sources for near-field underwater moving target

    NASA Astrophysics Data System (ADS)

    Chen, Zhifei; Hou, Hong; Yang, Jianhua; Sun, Jincai; Wang, Qian

    2013-06-01

    The double pulse sources (DPS) method is presented for linear track estimation in this work. In the field of noise identification of underwater moving target, the Doppler will distort the frequency and amplitude of the radiated noise. To eliminate this, the track estimation is necessary. In the DPS method, we first estimate bearings of two sinusoidal pulse sources installed in the moving target through baseline positioning method. Meanwhile, the emitted and recorded time of each pulse are also acquired. Then the linear track parameters will be achieved based on the geometry pattern with the help of double sources spacing. The simulated results confirm that the DPS improves the performance of the previous double source spacing method. The simulated experiments were carried out using a moving battery car to further evaluate its performance. When the target is 40-60m away, the experiment results show that biases of track azimuth and abeam distance of DPS are under 0.6o and 3.4m, respectively. And the average deviation of estimated velocity is around 0.25m/s.

  16. Double-pulse laser-induced breakdown spectroscopy analysis of scales from petroleum pipelines

    NASA Astrophysics Data System (ADS)

    Cavalcanti, G. H.; Rocha, A. A.; Damasceno, R. N.; Legnaioli, S.; Lorenzetti, G.; Pardini, L.; Palleschi, V.

    2013-09-01

    Pipeline scales from the Campos Bay Petroleum Field near Rio de Janeiro, Brazil have been analyzed by both Raman spectroscopy and by laser-induced breakdown spectroscopy (LIBS) using a double-pulse, calibration-free approach. Elements that are characteristic of petroleum (e.g. C, H, N, O, Mg, Na, Fe and V) were detected, in addition to the Ca, Al, and Si which form the matrix of the scale. The LIBS results were compared with the results of micro-Raman spectroscopy, which confirmed the nature of the incrustations inferred by the LIBS analysis. Results of this preliminary study suggest that diffusion of pipe material into the pipeline intake column plays an important role in the growth of scale. Thanks to the simplicity and relative low cost of equipment and to the fact that no special chemical pre-treatment of the samples is needed, LIBS can offer very fast acquisition of data and the possibility of in situ measurements. LIBS could thus represent an alternative or complementary method for the chemical characterization of the scales by comparison to conventional analytical techniques, such as X-ray diffraction or X-ray fluorescence.

  17. Explosive-Emission Plasma Dynamics in Ion Diode in Double-Pulse Mode

    NASA Astrophysics Data System (ADS)

    Alexander, I. Pushkarev; Yulia, I. Isakova

    2011-12-01

    The results of an experimental investigation of explosive-emission plasma dynamics in an ion diode with self-magnetic insulation are presented. The investigations were accomplished at the TEMP-4M accelerator set in a mode of double pulse formation. Plasma behaviour in the anode-cathode gap was analyzed according to both the current-voltage characteristics of the diode (time resolution of 0.5 ns) and thermal imprints on a target (spatial resolution of 0.8 mm). It was shown that when plasma formation at the potential electrode was complete, and up until the second (positive) pulse, the explosive-emission plasma expanded across the anode-cathode gap with a speed of 1.3±0.2 cm/μs. After the voltage polarity at the potential electrode was reversed (second pulse), the plasma erosion in the anode-cathode gap (similar to the effect of a plasma opening switch) occurred. During the generation of an ion beam the size of the anode-cathode gap spacing was determined by the thickness of the plasma layer on the potential electrode and the layer thickness of the electrons drifting along the grounded electrode.

  18. Three-dimensional compositional mapping using double-pulse micro-laser-induced breakdown spectroscopy technique

    NASA Astrophysics Data System (ADS)

    Grassi, R.; Grifoni, E.; Gufoni, S.; Legnaioli, S.; Lorenzetti, G.; Macro, N.; Menichetti, L.; Pagnotta, S.; Poggialini, F.; Schiavo, C.; Palleschi, V.

    2017-01-01

    In this communication, we present the development of the first double-pulse micro-LIBS (DP-μLIBS) instrument for three-dimensional compositional mapping of materials. The system allows for high-resolution three-dimensional scanning of materials; its advantages with respect to conventional single-pulse micro-LIBS systems are described and discussed. As a test example, we analyzed three Euro coins to show the performances of the system on homogeneous samples (20 Eurocents), heterogeneous samples (1 Euro) and layered samples (5 Eurocents). DP-μLIBS cannot provide isotopic information and has, typically, limits of detection for the elements of interest much higher with respect to Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry (LA-ICP-MS). However, when the isotopic information and the extreme sensitivity to trace elements is not be necessary, the results obtained show that DP-μLIBS can be a viable alternative to LA-ICP-MS for the acquisition of high resolution three-dimensional compositional maps.

  19. Characterization of MeV proton acceleration from double pulse irradiation of foil targets

    NASA Astrophysics Data System (ADS)

    Kerr, S.; Mo, M. Z.; Masud, R.; Tiedje, H. F.; Tsui, Y.; Fedosejevs, R.; Link, A.; Patel, P.; McLean, H. S.; Hazi, A.; Chen, H.; Ceurvorst, L.; Norreys, P.

    2014-10-01

    We report on the experimental characterization of proton acceleration from double-pulse irradiation of um-scale foil targets. Temporally separated sub-picosecond pulses have been shown to increase the conversion efficiency of laser energy to MeV protons. Here, two 700 fs, 1 ω pulses were separated by 1 to 5 ps; total beam energy was 100 J, with 5-20% of the total energy contained within the first pulse. In contrast to the ultraclean beams used in previous experiments, prepulse energies on the order of 10 mJ were present in the current experiments which appear to have a moderating effect on the enhancement. Proton beam measurements were made with radiochromic film stacks, as well as magnetic spectrometers. The effect on electron generation was measured using Kα emission from buried Cu tracer layers, while specular light diagnostics (FROG, reflection spectralon) indicated the laser coupling efficiency into the target. The results obtained will be presented and compared to PIC simulations. Work by LLNL was performed under the auspices of U.S. DOE under contract DE-AC52-07NA27344.

  20. High-resolution three-dimensional compositional imaging by double-pulse laser-induced breakdown spectroscopy

    NASA Astrophysics Data System (ADS)

    Schiavo, C.; Menichetti, L.; Grifoni, E.; Legnaioli, S.; Lorenzetti, G.; Poggialini, F.; Pagnotta, S.; Palleschi, V.

    2016-08-01

    In this paper we present a new instrument specifically realized for high-resolution three-dimensional compositional analysis and mapping of materials. The instrument is based on the coupling of a Double-Pulse Laser-Induced Breakdown Spectroscopy (LIBS) instrument with an optical microscope. The compositional mapping of the samples is obtained by scanning the laser beam across the surface of the sample, while the in depth analysis is performed by sending multiple laser pulses on the same point. Depths of analysis of several tens of microns can be obtained. The instrument presented has definite advantages with respect to Laser Ablation-ICP Mass Spectrometry in many applications related to material analysis, biomedicine and environmental diagnostics. An application to the diagnostics of industrial ceramics is presented, demonstrating the feasibility of Double-Pulse LIBS Imaging and its advantages with respect to conventional single-pulse LIBS imaging.

  1. Experimental investigation on colloidal alumina nanoparticles produced by collinear nanosecond double-pulse laser ablation in liquid

    NASA Astrophysics Data System (ADS)

    Mahdieh, M. H.; Fattahi, B.; Akbari Jafarabadi, M.

    2017-01-01

    In this research, we investigated the effect of inter-pulse delay times on production of colloidal alumina nanoparticles by collinear double pulse laser ablation. In comparison to single pulse laser ablation, collinear double pulse laser ablation with inter-pulse delay times of 5, 10, 15 and 20 ns results in production of colloidal nanoparticles with smaller mean size and lower variance size distribution. In the case of 5 ns inter-pulse delay time, the highest concentration of nanoparticles was obtained due to more rapid cooling time of the plasma as a result of higher rate of nuclei generation than particle growth. The results also showed that the main pulse and the pre-pulse with 5 ns delay time have significant overlap and consequently such condition leads to maximum influence on the ablation.

  2. Femtosecond double-pulse fabrication of hierarchical nanostructures based on electron dynamics control for high surface-enhanced Raman scattering.

    PubMed

    Zhang, Ning; Li, Xin; Jiang, Lan; Shi, Xuesong; Li, Cong; Lu, Yongfeng

    2013-09-15

    This Letter presents a simple, efficient approach for high surface-enhanced Raman scattering by one-step controllable fabrication of hierarchical structures (nanoparticles+subwavelength ripples) on silicon substrates in silver nitrate solutions using femtosecond double pulses based on nanoscale electron dynamics control. As the delays of the double pulses increase from 0 fs to 1 ps, the hierarchical structures can be controlled with (1) nanoparticles--the number of nanoparticles in the range of 40-100 nm reaches the maximum at 800 fs and (2) ripples--the subwavelength ripples become intermittent with decreased ablation depths. The redistributed nanoparticles and the modified ripple structures contribute to the maximum enhancement factor of 2.2×10(8) (measured by 10(-6)  M rhodamine 6G solution) at the pulse delay of 800 fs.

  3. Effect of atmosphere on collinear double-pulse laser-induced breakdown spectroscopy

    SciTech Connect

    Andrew J. Effenberger, Jr.; Jill R. Scott

    2010-09-01

    Double pulse laser induced breakdown spectroscopy (DP-LIBS) has been shown to enhance LIBS spectra. Several researches have reported significant increases in signal-to-noise and or spectral intensity [1-4]. In addition to DP-LIBS, atmospheric conditions can also increase spectra intensity. For example, Iida [5] found that He and Ar both increase LIBS intensity compared to air at one 1 atm. It was also found that as the pressure was decreased to 100 Torr, LIBS intensity increased in Ar and air for single pulse (SP) LIBS. In this study, a collinear DP-LIBS scheme is used along with manipulation of the atmospheric conditions. The DP-LIBS scheme consists of a 355 nm ablative pulse fired into a sample contained in a vacuum chamber. A second analytical 1064 nm pulse is then fired 100 ns to 10 µs after and along the same path of the first pulse. Ar, He and air at pressures ranging from atmospheric pressure (630 Torr at elevation) to 10-5 Torr are introduced during DP-LIBS and SP-LIBS experiments. For a brass sample, a significant increase in spectral intensity of Cu and Zn lines were observed in DP-LIBS under Ar compared to DP-LIBS in air (Figure 1). It was also found that Cu and Zn lines acquired with SP-LIBS in Ar are nearly as intense as DP-LIBS in air. Signal-to-noise for lines from various samples will be reported for both DP-LIBS and SP-LIBS in Ar, He, and air at pressures ranging from 630 Torr to 10-5 Torr.

  4. Hydrogen isotope detection in metal matrix using double-pulse laser-induced breakdown-spectroscopy

    NASA Astrophysics Data System (ADS)

    Fantoni, Roberta; Almaviva, Salvatore; Caneve, Luisa; Colao, Francesco; Maddaluno, Giorgio; Gasior, Pawel; Kubkowska, Monika

    2017-03-01

    The amount of hydrogen isotopes retained in plasma facing components (PFCs) and the determination of their surface layer composition are among the most critical issues for the next generation fusion device, ITER, under construction in Cadarache (France). Laser Induced Breakdown Spectroscopy (LIBS) is currently under evaluation as a technique suitable for quantitative, in situ, non-invasive measurements of these quantities. In order to detect traces of contaminant in metallic samples and improve its limit of detection (LOD), the Double Pulse LIBS (DP-LIBS) variant can be used instead of the standard Single Pulse LIBS (SP-LIBS), as it has been proven by several authors that DP-LIBS can considerably raise the analytical performances of the technique. In this work Mo samples coated with a 1.5-1.8 μm thick W-Al mixed layer, contaminated with co-deposited deuterium (D) were measured by SP- and DP-LIBS under vacuum (p 5 × 10- 5 mbar), with an experimental set-up simulating conditions that can be found in a real fusion device between plasma discharges. A partial Calibration Free procedure (pCF) was applied to the LIBS data in order to retrieve the relative concentration of W and Al in the mixed layer. The amount of deuterium was then inferred by using tungsten as internal standard, accounting for the intensity ratio between the Dα line and nearby W I lines. The results are in satisfactory agreement with those obtained from preliminary Ion Beam Analysis measurements performed immediately after the specimen's realization.

  5. 2-micron Double Pulsed IPDA Lidar for Atmospheric CO2 Measurement

    NASA Astrophysics Data System (ADS)

    Yu, Jirong; Petros, Mulugeta; Refaat, Tamer; Reithmaier, Karl; Remus, Ruben; Singh, Upendra; Johnson, Will; Boyer, Charlie; Fay, James; Johnston, Susan; Murchison, Luke; Scola, Tory

    2015-04-01

    We have developed a high energy pulsed 2-micron IPDA lidar instrument to measure the atmospheric CO2 column density. The IPDA lidar is operated on the long wavelength wing of R(30) CO2 line at 2050.967 nm (4875.749 cm-1) in the side-line operation mode. The R(30) line is an excellent absorption line for the measurements of CO2 in 2µm wavelength region with regard to the strength of the absorption lines, low susceptibility to atmospheric temperature variability, and freedom from problematic interference with other absorption lines. The Ho:Tm:YLF laser transmitter is designed to be operated in a unique double pulse format that can produce two-pulse pair in 10 Hz operation. Typically, the output energies of the laser transmitter are 100mJ and 45mJ for the first pulse and the second pulse, respectively. We injection seed the first pulse with on-line frequency and the second pulse with off-line frequency. The IPDA lidar instrument size, weight and power consumption were restricted to small research aircraft payload requirements. The airborne IPDA lidar instrument measures the total integrated column content of CO2 from the instrument to the ground but with weighting that can be tuned by controlling the transmitted wavelengths. Therefore, the transmitter could be tuned to weight the column measurement to the surface for optimum CO2 interaction studies or up to the free troposphere for optimum transport studies. The 2-μm CO2 IPDA lidar airborne demonstration was conducted during March 20, 2014 through April 10, 2014. IPDA lidar airborne flights included various operating and environmental conditions. Environmental conditions included different flight altitude up to 8.3 km, different ground target conditions such as vegetation, soil, ocean, snow and sand and different cloud conditions. Besides, some flights targeted power plant incinerators for investigating the IPDA sensitivity to CO2 plums. The lidar instrument is robust during all of the flights. This paper describes

  6. Minimization of thermomechanical side effects in IR ablation by use of Q-switched double pulses

    NASA Astrophysics Data System (ADS)

    Vogel, Alfred; Schmidt, Peter; Flucke, Barbara

    2001-07-01

    Holmium laser pulses (λ= 2.1 m) are often used for medical laser applications inside the human body, because they can be transmitted through low-OH quartz fibers, and they are relatively well absorbed in water and biological tissues. However, large thermal damage zones were observed after application of free-running holmium laser pulses for arthroscopic surgery. The aim of our study is to reduce thermal damage without introducing additional mechanical damage and without impairing the hemostatic action of the laser radiation. For that purpose we use double pulses from a custom-made acousto-optically Q- switched thulium laser (λ = 2.0 μm) that can emit pulses with energies of up to 150 mJ. The penetration depth of the thulium laser radiation (170 μm) as well as the thermal damage zone are only half as large as that of the holmium laser. The use of Q-switched pulses creates stress confinement conditions leading to a more efficient ablation than with free running pulses. For a given ablation depth, the residual heat deposited in the tissue is therefore smaller than with free running pulses and, hence, also the thermal damage zone. This reduction of thermal damage is possible even though the free-running pulses already fulfil the condition for thermal confinement. The thermal damage zone was only 100 μm for the Q-switched thulium pulses but 200 μm for the free-running pulses. The degree of thermal damage was, in addition, much more severe for the free-running pulses. Q-switched pulses lead to an explosive ablation of the target material. In a liquid environment, this gives rise to the formation of cavitation effects, we release a pre-pulse with small energy (40 mJ) before each ablation pulse of up to 150 mJ. The pre-pulse produces a small cavity that is then filled by the ablation products of the main pulse. The ablation pulse is emitted about 100 μs after the pre-pulse when the bubble is maximally expanded. This way, no additional cavitation effects are induced

  7. Investigation of the osteitis deformans phases in snake vertebrae by double-pulse laser-induced breakdown spectroscopy.

    PubMed

    Galiová, M; Kaiser, J; Novotný, K; Ivanov, M; Nývltová Fisáková, M; Mancini, L; Tromba, G; Vaculovic, T; Liska, M; Kanický, V

    2010-09-01

    Double-pulse laser-induced breakdown spectroscopy (DP-LIBS) was optimized for microspatial analyses of fossil and recent snake vertebrae. As complimentary techniques, solution analysis by inductively coupled plasma mass spectrometry and synchrotron radiation X-ray microtomography was utilized in order to determine the overall concentration of the selected elements in the samples and to visualize nondestructively the fossil sample microstructure, respectively. Elemental mapping of pathological bony tissue by DP-LIBS has been proven as a powerful tool for considering the osteitis deformans phases in fossil vertebrae.

  8. Strain event detection using a double-pulse technique of a Brillouin scattering-based distributed optical fiber sensor.

    PubMed

    Cho, Seok-Beom; Lee, Jung-Ju; Kwon, Il-Bum

    2004-09-06

    Stimulated Brillouin scattering in optical fibers can be used to measure strain or temperature in a distributed manner. Brillouin optical time domain analysis (BOTDA) is the most common sensor system based on the Brillouin scattering. To improve the spatial resolution of these measurements, shorter pulses must be used, resulting in reduced signal powers causing a decrease of the dynamic range. In this paper, a doublepulse technique was proposed to enhance the spatial resolution of BOTDA. Experimental results showed that the ability to resolve two adjacent events could be enhanced, about twice, by using a double-pulsed pump light without decreases in the dynamic range.

  9. Laser-induced periodic surface structures on zinc oxide crystals upon two-colour femtosecond double-pulse irradiation

    NASA Astrophysics Data System (ADS)

    Höhm, S.; Rosenfeld, A.; Krüger, J.; Bonse, J.

    2017-03-01

    In order to study the temporally distributed energy deposition in the formation of laser-induced periodic surface structures (LIPSS) on single-crystalline zinc oxide (ZnO), two-colour double-fs-pulse experiments were performed. Parallel or cross-polarised double-pulse sequences at 400 and 800 nm wavelength were generated by a Mach–Zehnder interferometer, exhibiting inter-pulse delays up to a few picoseconds between the sub-ablation 50-fs-pulses. Twenty two-colour double-pulse sequences were collinearly focused by a spherical mirror to the sample surface. The resulting LIPSS periods and areas were analysed by scanning electron microscopy. The delay-dependence of these LIPSS characteristics shows a dissimilar behaviour when compared to the semiconductor silicon, the dielectric fused silica, or the metal titanium. A wavelength-dependent plasmonic mechanism is proposed to explain the delay-dependence of the LIPSS on ZnO when considering multi-photon excitation processes. Our results support the involvement of nonlinear processes for temporally overlapping pulses. These experiments extend previous two-colour studies on the indirect semiconductor silicon towards the direct wide band-gap semiconductor ZnO and further manifest the relevance of the ultrafast energy deposition for LIPSS formation.

  10. Spatially-offset double-pulse laser-induced breakdown spectroscopy: A novel technique for analysis of thin deposited layers

    NASA Astrophysics Data System (ADS)

    Nishijima, D.; Hollmann, E. M.; Doerner, R. P.

    2016-10-01

    A novel technique, spatially-offset double-pulse laser-induced breakdown spectroscopy (SODP-LIBS), is invented for analysis of thin layers. In this technique, two laser spots are spatially offset by a few mm, while there is no spatial gap for the standard collinear DP-LIBS. It is demonstrated from analysis of thin W layers (∼30-250 nm thickness) deposited on Mo substrates at a reduced ambient pressure of ∼ 5 × 10-3 Torr that (1) the W I signal intensity is enhanced with SODP-LIBS and (2) a clearer transition between W and Mo is obtained with SODP-LIBS, compared to the standard DP-LIBS.

  11. Re-Heating Effect on the Enhancement of Plasma Emission Generated from Fe Under Femtosecond Double-Pulse Laser Irradiation

    NASA Astrophysics Data System (ADS)

    Wang, Ying; Chen, Anmin; Li, Suyu; Sui, Laizhi; Liu, Dunli; Li, Shuchang; Li, He; Jiang, Yuanfei; Jin, Mingxing

    2016-12-01

    In this paper, we present a study on the effect of inter-pulse delay using femtosecond double-pulse laser-induced breakdown spectroscopy in a collinear geometry. The temporal evolution of spectral intensity is performed for the lines of Fe I 423.60 nm, Fe I 425.08 nm and Fe I 427.18 nm. It is found that, by selecting appropriate inter-pulse delay, the signal enhancement can be significantly increased compared with the single-pulse case. A three-fold enhancement in the current experiment is obtained. The plasma temperature and electron density are also investigated based on the theory of Boltzmann plot and Stark broadening. We attribute the main mechanism for emission enhancement to the plasma re-heating effect. supported by the National Basic Research Program of China (No. 2013CB922200), the China Postdoctoral Science Foundation (No. 2014M551169), National Natural Science Foundation of China (Nos. 11674128, 11474129 and 11504129)

  12. Testing of a Two-Micron Double-Pulse IPDA Lidar Instrument for Airborne Atmospheric Carbon Dioxide Measurement

    NASA Astrophysics Data System (ADS)

    Yu, J.; Petros, M.; Refaat, T. F.; Remus, R.; Singh, U. N.

    2015-12-01

    Utilizing a tunable two-micron double-pulse laser transmitter, an airborne IPDA lidar system has been developed at NASA Langley Research Center for atmospheric carbon dioxide column measurements. The instrument comprises a receiver with 0.4 m telescope and InGaAs pin detectors coupled to 12-bit, 200 MS/s waveform digitizers. For on-site ground testing, the 2-μm CO2 IPDA lidar was installed inside a trailer located where meteorological data and CO2 mixing ratio profiles were obtained from CAPABLE and LiCoR in-suite sampling, respectively. IPDA horizontal ground testing with 860 m target distance indicated CO2 sensitivity of 2.24 ppm with -0.43 ppm offset, while operating at 3 GHz on-line position from the R30 line center. Then, the IPDA lidar was integrated inside the NASA B-200 aircraft, with supporting instrumentation, for airborne testing and validation. Supporting instruments included in-situ LiCoR sensor, GPS and video recorder for target identification. Besides, aircraft built-in sensors provided altitude, pressure, temperature and relative humidity sampling during flights. The 2-mm CO2 IPDA lidar airborne testing was conducted through ten daytime flights (27 hours flight time). Airborne testing included different operating and environmental conditions for flight altitude up to 7 km, different ground target conditions such as vegetation, soil, ocean, snow and sand and different cloud conditions. Some flights targeted power plant incinerators for investigating IPDA sensitivity to CO2 plums. Relying on independent CO2 in-situ sampling, conducted through NOAA, airborne IPDA CO2 sensitivity of 4.15 ppm with 1.14 ppm offset were observed at 6 km altitude and 4 GHz on-line offset frequency. This validates the 2-μm double-pulse IPDA lidar for atmospheric CO2 measurement.

  13. Effect of inter-pulse delay time on production and size properties of colloidal nanoparticles prepared by collinear double-pulse laser ablation in liquid

    NASA Astrophysics Data System (ADS)

    Fattahi, Behzad; Mahdieh, Mohammah Hossein

    2016-08-01

    The influence of inter-pulse delay times (0-20 ns) between two collinear sequential nanosecond pulses on the production and size properties (mean size and size distribution) of colloidal nanoparticles prepared by pulsed laser ablation of a silver target in a distilled water medium has been studied. Various laser fluences at different inter-pulse delay times between two collinear pulses were used. Furthermore, for a better understanding of the effect of the double-pulse and single-pulse mode, experiments were performed. The characterization of the synthesized colloidal nanoparticles was investigated using scanning electron microscopy (SEM) and UV-vis absorption spectroscopy. Our results showed that 5 ns time-delayed double-pulse laser ablation results in the production of nanoparticles with the highest concentration among the other time-delayed ablation experiments and even more than single-pulse-mode experiments. It also found that using a double-pulse approach with inter-pulse delay times in the range of 0-20 ns leads to the production of nanoparticles with smaller mean sizes and narrower size distributions in comparison to single-pulse-mode laser ablation. The effect of time overlapping between two pulses in the case of double-pulse ablation was analyzed.

  14. Self-Calibration and Laser Energy Monitor Validations for a Double-Pulsed 2-Micron CO2 Integrated Path Differential Absorption Lidar Application

    NASA Technical Reports Server (NTRS)

    Refaat, Tamer F.; Singh, Upendra N.; Petros, Mulugeta; Remus, Ruben; Yu, Jirong

    2015-01-01

    Double-pulsed 2-micron integrated path differential absorption (IPDA) lidar is well suited for atmospheric CO2 remote sensing. The IPDA lidar technique relies on wavelength differentiation between strong and weak absorbing features of the gas normalized to the transmitted energy. In the double-pulse case, each shot of the transmitter produces two successive laser pulses separated by a short interval. Calibration of the transmitted pulse energies is required for accurate CO2 measurement. Design and calibration of a 2-micron double-pulse laser energy monitor is presented. The design is based on an InGaAs pin quantum detector. A high-speed photo-electromagnetic quantum detector was used for laser-pulse profile verification. Both quantum detectors were calibrated using a reference pyroelectric thermal detector. Calibration included comparing the three detection technologies in the single-pulsed mode, then comparing the quantum detectors in the double-pulsed mode. In addition, a self-calibration feature of the 2-micron IPDA lidar is presented. This feature allows one to monitor the transmitted laser energy, through residual scattering, with a single detection channel. This reduces the CO2 measurement uncertainty. IPDA lidar ground validation for CO2 measurement is presented for both calibrated energy monitor and self-calibration options. The calibrated energy monitor resulted in a lower CO2 measurement bias, while self-calibration resulted in a better CO2 temporal profiling when compared to the in situ sensor.

  15. Optical time of flight studies of lithium plasma in double pulse laser ablation: Evidence of inverse Bremsstrahlung absorption

    SciTech Connect

    Sivakumaran, V.; Joshi, H. C.; Singh, R. K.; Kumar, Ajai

    2014-06-15

    The early stage of formation of lithium plasma in a collinear—double pulse laser ablation mode has been studied using optical time of flight (OTOF) spectroscopy as a function of inter-pulse delay time, the distance from the target surface and the fluence of the ablation lasers. The experimental TOF measurements were carried out for lithium neutral (670.8 nm and 610.3 nm), and ionic (548.4 nm and 478.8 nm) lines. These experimental observations have been compared with that for single pulse laser ablation mode. It is found that depending on the fluence and laser pulse shape of the first pre-ablation laser and the second main ablation laser, the plasma plume formation and its characteristic features can be described in terms of plume-plume or laser-plume interaction processes. Moreover, the enhancement in the intensity of Li neutral and ionic lines is observed when the laser-plume interaction is the dominant process. Here, we see the evidence of the role of inverse Bremsstrahlung absorption process in the initial stage of formation of lithium plasma in this case.

  16. Double pulse laser induced breakdown spectroscopy: Experimental study of lead emission intensity dependence on the wavelengths and sample matrix

    NASA Astrophysics Data System (ADS)

    Piscitelli S, V.; Martínez L., M. A.; Fernández C., A. J.; González, J. J.; Mao, X. L.; Russo, R. E.

    2009-02-01

    Lead (Pb) emission intensity (atomic line 405.78 nm) dependence on the sample matrix (metal alloy) was studied by means of collinear double pulse (DP)-laser induced breakdown spectroscopy (LIBS). The measurement of the emission intensity produced by three different wavelength combinations (i.e. I:532 nm-II:1064 nm, I:532 nm-II:532 nm, and I:532 nm-II:355 nm) from three series of standard reference materials showed that the lead atomic line 405.78 nm emission intensity was dependent on the sample matrix for all the combination of wavelengths, however reduced dependency was found for the wavelength combination I:532 nm-II:355 nm. Two series of standard reference materials from the National Institute of Standards and Technology (NIST) and one series from the British Chemical Standards (BCS) were used for these experiments. Calibration curves for lead ablated from NIST 626-630 ("Zn 95Al 4Cu 1") provided higher sensitivity (slope) than those calibration curves produced from NIST 1737-1741 ("Zn 99.5Al 0.5") and with the series BCS 551-556 ("Cu 87Sn 11"). Similar trends between lead emission intensity (calibration curve sensitivities) and reported variations in plasma temperatures caused by the differing ionization potentials of the major and minor elements in these samples were established.

  17. Self-calibration and laser energy monitor validations for a double-pulsed 2-μm CO2 integrated path differential absorption lidar application.

    PubMed

    Refaat, Tamer F; Singh, Upendra N; Petros, Mulugeta; Remus, Ruben; Yu, Jirong

    2015-08-20

    Double-pulsed 2-μm integrated path differential absorption (IPDA) lidar is well suited for atmospheric CO2 remote sensing. The IPDA lidar technique relies on wavelength differentiation between strong and weak absorbing features of the gas normalized to the transmitted energy. In the double-pulse case, each shot of the transmitter produces two successive laser pulses separated by a short interval. Calibration of the transmitted pulse energies is required for accurate CO2 measurement. Design and calibration of a 2-μm double-pulse laser energy monitor is presented. The design is based on an InGaAs pin quantum detector. A high-speed photoelectromagnetic quantum detector was used for laser-pulse profile verification. Both quantum detectors were calibrated using a reference pyroelectric thermal detector. Calibration included comparing the three detection technologies in the single-pulsed mode, then comparing the quantum detectors in the double-pulsed mode. In addition, a self-calibration feature of the 2-μm IPDA lidar is presented. This feature allows one to monitor the transmitted laser energy, through residual scattering, with a single detection channel. This reduces the CO2 measurement uncertainty. IPDA lidar ground validation for CO2 measurement is presented for both calibrated energy monitor and self-calibration options. The calibrated energy monitor resulted in a lower CO2 measurement bias, while self-calibration resulted in a better CO2 temporal profiling when compared to the in situ sensor.

  18. Determination of chlorine, sulfur and carbon in reinforced concrete structures by double-pulse laser-induced breakdown spectroscopy

    NASA Astrophysics Data System (ADS)

    Labutin, Timur A.; Popov, Andrey M.; Zaytsev, Sergey M.; Zorov, Nikita B.; Belkov, Mikhail V.; Kiris, Vasilii V.; Raikov, Sergey N.

    2014-09-01

    Accurate and reliable quantitative determination of non-metal corrosion agents in concrete is still an actual task of analytical use of LIBS. Two double-pulse LIBS systems were tested as a tool for the determination of chlorine, sulfur and carbon in concretes. Both systems had collinear configuration; a laboratory setup was equipped with an ICCD and two lasers (355/532 nm + 540 nm), but a CCD was a detector for a mobile system with one laser (1064 nm). Analytical lines of Cl I at 837.59 nm, S I at 921 nm and C I at 247.86 nm were used to plot calibration curves. Optimal interpulse delays for the laboratory setup were 4 μs for chlorine and 2.8 μs for carbon, while an interpulse delay of 2 μs was optimal for chlorine and sulfur determination with the mobile system. We suggested the normalization of the Cl I line at 837.59 nm to the Mg II line at 279.08 nm (visible at 837.23 nm in the third order) to compensate for pulse-to-pulse fluctuations of chlorine lines. It provided the decrease of the detection limit of chlorine from 400 ppm to 50 ppm. Therefore, we reported that LIBS can be used to determine main corrosive active substances under ambient conditions in concrete below critical threshold values. Moreover, the application of the mobile system for in-situ qualitative assessment of corrosion way of a steel cage of a swimming pool dome was also demonstrated. It was found that chloride corrosion due to the disinfection of water was the main way for corrosion of the open part steel and the steel rebar inside the concrete.

  19. Double-pulse 2-μm integrated path differential absorption lidar airborne validation for atmospheric carbon dioxide measurement.

    PubMed

    Refaat, Tamer F; Singh, Upendra N; Yu, Jirong; Petros, Mulugeta; Remus, Ruben; Ismail, Syed

    2016-05-20

    Field experiments were conducted to test and evaluate the initial atmospheric carbon dioxide (CO2) measurement capability of airborne, high-energy, double-pulsed, 2-μm integrated path differential absorption (IPDA) lidar. This IPDA was designed, integrated, and operated at the NASA Langley Research Center on-board the NASA B-200 aircraft. The IPDA was tuned to the CO2 strong absorption line at 2050.9670 nm, which is the optimum for lower tropospheric weighted column measurements. Flights were conducted over land and ocean under different conditions. The first validation experiments of the IPDA for atmospheric CO2 remote sensing, focusing on low surface reflectivity oceanic surface returns during full day background conditions, are presented. In these experiments, the IPDA measurements were validated by comparison to airborne flask air-sampling measurements conducted by the NOAA Earth System Research Laboratory. IPDA performance modeling was conducted to evaluate measurement sensitivity and bias errors. The IPDA signals and their variation with altitude compare well with predicted model results. In addition, off-off-line testing was conducted, with fixed instrument settings, to evaluate the IPDA systematic and random errors. Analysis shows an altitude-independent differential optical depth offset of 0.0769. Optical depth measurement uncertainty of 0.0918 compares well with the predicted value of 0.0761. IPDA CO2 column measurement compares well with model-driven, near-simultaneous air-sampling measurements from the NOAA aircraft at different altitudes. With a 10-s shot average, CO2 differential optical depth measurement of 1.0054±0.0103 was retrieved from a 6-km altitude and a 4-GHz on-line operation. As compared to CO2 weighted-average column dry-air volume mixing ratio of 404.08 ppm, derived from air sampling, IPDA measurement resulted in a value of 405.22±4.15  ppm with 1.02% uncertainty and

  20. New narrow infrared absorption features in the spectrum of Io between 3600 and 3100 cm (2.8-3.2 micrometers)

    NASA Technical Reports Server (NTRS)

    Sandford, Scott A.; Geballe, Thomas R.; Salama, Farid; Goorvitch, David

    1994-01-01

    We report the discovery of a series of infrared absorption bands between 3600 and 3100/cm (2.8-3.2 micrometers) in the spectrum of Io. Individual narrow bands are detected at 3553, 3514.5, 3438, 3423, 3411.5, and 3401/cm (2.815, 2.845, 2.909, 2.921, 2.931, and 2.940 micrometers, respectively). The positions and relative strengths of these bands, and the difference of their absolute strengths between the leading and trailing faces of Io, indicate that they are due to SO2. The band at 3438/cm (2.909 micrometers) could potentially have a contribution from an additional molecular species. The existence of these bands in the spectrum of Io indicates that a substantial fraction of the SO2 on Io must reside in transparent ices having relatively large crystal sizes. The decrease in the continuum observed at the high frequency ends of the spectra is probably due to the low frequency side of the recently detected, strong 3590/cm (2.79 micrometer) feature. This band is likely due to the combination of a moderately strong SO2 band and an additional absorption from another molecular species, perhaps H2O isolated in SO2 at low concentrations. A broad (FWHM approximately = 40-60/cm), weak band is seen near 3160/cm (3.16 micrometers) and is consistent with the presence of small quantities of H2O isolated in SO2-rich ices. There is no evidence in the spectra for the presence of H2O vapor on Io. Thus, the spectra presented here neither provide unequivocal evidence for the presence of H2O on Io nor preclude it at the low concentrations suggested by past studies.

  1. Potential of M-Wave Elicited by Double Pulse for Muscle Fatigue Evaluation in Intermittent Muscle Activation by Functional Electrical Stimulation for Motor Rehabilitation

    PubMed Central

    Miura, Naoto; Watanabe, Takashi

    2016-01-01

    Clinical studies on application of functional electrical stimulation (FES) to motor rehabilitation have been increasing. However, muscle fatigue appears early in the course of repetitive movement production training by FES. Although M-wave variables were suggested to be reliable indices of muscle fatigue in long lasting constant electrical stimulation under the isometric condition, the ability of M-wave needs more studies under intermittent stimulation condition, because the intervals between electrical stimulations help recovery of muscle activation level. In this paper, M-waves elicited by double pulses were examined in muscle fatigue evaluation during repetitive movements considering rehabilitation training with surface electrical stimulation. M-waves were measured under the two conditions of repetitive stimulation: knee extension force production under the isometric condition and the dynamic movement condition by knee joint angle control. Amplitude of M-wave elicited by the 2nd pulse of a double pulse decreased during muscle fatigue in both measurement conditions, while the change in M-waves elicited by single pulses in a stimulation burst was not relevant to muscle fatigue in repeated activation with stimulation interval of 1 s. Fatigue index obtained from M-waves elicited by 2nd pulses was suggested to provide good estimation of muscle fatigue during repetitive movements with FES. PMID:27110556

  2. Potential of M-Wave Elicited by Double Pulse for Muscle Fatigue Evaluation in Intermittent Muscle Activation by Functional Electrical Stimulation for Motor Rehabilitation.

    PubMed

    Miura, Naoto; Watanabe, Takashi

    2016-01-01

    Clinical studies on application of functional electrical stimulation (FES) to motor rehabilitation have been increasing. However, muscle fatigue appears early in the course of repetitive movement production training by FES. Although M-wave variables were suggested to be reliable indices of muscle fatigue in long lasting constant electrical stimulation under the isometric condition, the ability of M-wave needs more studies under intermittent stimulation condition, because the intervals between electrical stimulations help recovery of muscle activation level. In this paper, M-waves elicited by double pulses were examined in muscle fatigue evaluation during repetitive movements considering rehabilitation training with surface electrical stimulation. M-waves were measured under the two conditions of repetitive stimulation: knee extension force production under the isometric condition and the dynamic movement condition by knee joint angle control. Amplitude of M-wave elicited by the 2nd pulse of a double pulse decreased during muscle fatigue in both measurement conditions, while the change in M-waves elicited by single pulses in a stimulation burst was not relevant to muscle fatigue in repeated activation with stimulation interval of 1 s. Fatigue index obtained from M-waves elicited by 2nd pulses was suggested to provide good estimation of muscle fatigue during repetitive movements with FES.

  3. A Comparative Study of Single-pulse and Double-pulse Laser-Induced Breakdown Spectroscopy with Uranium-containing Samples.

    PubMed

    Skrodzki, Patrick J; Becker, Jason R; Diwakar, Prasoon K; Harilal, Sivanandan S; Hassanein, Ahmed

    2016-03-01

    Laser-induced breakdown spectroscopy (LIBS) holds potential advantages in special nuclear material (SNM) sensing and nuclear forensics, which require rapid analysis, minimal sample preparation, and stand-off distance capability. SNM, such as U, however, result in crowded emission spectra with LIBS, and characteristic emission lines are challenging to discern. It is well-known that double-pulse LIBS (DPLIBS) improves the signal intensity for analytes over conventional single-pulse LIBS (SPLIBS). This study investigates the U signal in a glass matrix using DPLIBS and compares it to signal obtained using SPLIBS. Double-pulse LIBS involves sequential firing of a 1.06 µm Nd:YAG pre-pulse and 10.6 µm TEA CO2 heating pulse in a near collinear geometry. Optimization of experimental parameters including inter-pulse delay and energy follows identification of characteristic lines for the bulk analyte Ca and the minor constituent analyte U for both DPLIBS and SPLIBS. Spatial and temporal coupling of the two pulses in the proposed DPLIBS technique yields improvements in analytical merits with a negligible increase in damage to the sample compared to SPLIBS. Subsequently, the study discusses optimum plasma emission conditions of U lines and relative figures of merit in both SPLIBS and DPLIBS. Investigation into plasma characteristics also addresses plausible mechanisms related to the observed U analyte signal variation between SPLIBS and DPLIBS.

  4. Effects of temporal laser profile on the emission spectra for underwater laser-induced breakdown spectroscopy: Study by short-interval double pulses with different pulse durations

    SciTech Connect

    Tamura, Ayaka Matsumoto, Ayumu; Nishi, Naoya; Sakka, Tetsuo; Nakajima, Takashi; Ogata, Yukio H.; Fukami, Kazuhiro

    2015-01-14

    We investigate the effects of temporal laser profile on the emission spectra of laser ablation plasma in water. We use short-interval (76 ns) double pulses with different pulse durations of the composing two pulses for the irradiation of underwater target. Narrow atomic spectral lines in emission spectra are obtained by the irradiation, where the two pulses are wide enough to be merged into a single-pulse-like temporal profile, while deformed spectra are obtained when the two pulses are fully separated. The behavior of the atomic spectral lines for the different pulse durations is consistent with that of the temporal profiles of the optical emission intensities of the plasma. All these results suggest that continuous excitation of the plasma during the laser irradiation for ∼100 ns is a key to obtain narrow emission spectral lines.

  5. Double-pulse laser induced breakdown spectroscopy with ambient gas in the vacuum ultraviolet: Optimization of parameters for detection of carbon and sulfur in steel

    NASA Astrophysics Data System (ADS)

    Jiang, X.; Hayden, P.; Costello, J. T.; Kennedy, E. T.

    2014-11-01

    Laser induced breakdown spectroscopy (LIBS) in the vacuum ultraviolet (VUV) has been applied to calibrated steel samples for the low concentration level detection of the light elements, carbon and sulfur in steel. Experimental optimization parameters, aimed at enhancing the sensitivity of the technique, included short wavelength spectral detection, double-pulse (DP) operation, variable focusing conditions and different ambient environments in terms of gas type and pressure. Two lasers were employed respectively as an ablation laser (Spectron: 1.06 μm/200 mJ/15 ns) and a reheating laser (Surelite: 1.06 μm/665 mJ/6 ns) in a collinear geometry. The results include insight into the most salient experimental variables and limits of detection in the parts per million range.

  6. Simulation of ablation and plume dynamics under femtosecond double-pulse laser irradiation of aluminum: Comparison of atomistic and continual approaches

    NASA Astrophysics Data System (ADS)

    Fokin, Vladimir B.; Povarnitsyn, Mikhail E.; Levashov, Pavel R.

    2017-02-01

    We elaborated two numerical methods, two-temperature hydrodynamics and hybrid two-temperature molecular dynamics, which take into account basic mechanisms of a metal target response to ultrashort laser irradiation. The model used for the description of the electronic subsystem is identical for both approaches, while the ionic part is defined by an equation of state in hydrodynamics and by an interatomic potential in molecular dynamics. Since the phase diagram of the equation of state and corresponding potential match reasonably well, the dynamics of laser ablation obtained by both methods is quite similar. This correspondence can be considered as a first step towards the development of a self-consistent combined model. Two important processes are highlighted in simulations of double-pulse ablation: (1) the crater depth decrease as a result of recoil flux formation in the nascent plume when the delay between the pulses increases; (2) the plume reheating by the second pulse that gives rise to two- three-fold growth of the electron temperature with the delay varying from 0 to 200 ps.

  7. A Comparative Study of Single-pulse and Double-pulse Laser-Induced Breakdown Spectroscopy with Uranium-containing Samples

    SciTech Connect

    Skrodzki, P. J.; Becker, J. R.; Diwakar, P. K.; Harilal, S. S.; Hassanein, A.

    2016-01-25

    Laser-induced breakdown spectroscopy (LIBS) holds potential advantages in special nuclear material (SNM) sensing and nuclear forensics which require rapid analysis, minimal sample preparation and stand-off distance capability. SNM, such as U, however, result in crowded emission spectra with LIBS, and characteristic emission lines are challenging to discern. It is well-known that double-pulse LIBS (DPLIBS) improves the signal intensity for analytes over conventional single-pulse LIBS (SPLIBS). This study investigates U signal in a glass matrix using DPLIBS and compares to signal features obtained using SPLIBS. DPLIBS involves sequential firing of 1.06 µm Nd:YAG pre-pulse and 10.6 µm TEA CO2 heating pulse in near collinear geometry. Optimization of experimental parameters including inter-pulse delay and energy follows identification of characteristic lines and signals for bulk analyte Ca and minor constituent analyte U for both DPLIBS and SPLIBS. Spatial and temporal coupling of the two pulses in the proposed DPLIBS technique yields improvements in analytical merits with negligible further damage to the sample compared to SPLIBS. Subsequently, the study discusses optimum plasma emission conditions of U lines and relative figures of merit in both SPLIBS and DPLIBS. Investigation into plasma characteristics also addresses plausible mechanisms related to observed U analyte signal variation between SPLIBS and DPLIBS.

  8. Analysis of Ti in textile stippled by TiO2 nanoparticle sol using double-pulse LIBS and ED XRF spectrometry

    NASA Astrophysics Data System (ADS)

    Pouzar, M.; Průšová, M.; Černohorský, T.; Wiener, J.; Kratochvil, T.

    2011-11-01

    Double-pulse LIBS and ED XRF usabilities for quantitative analysis of Ti in samples of cotton, wool, and viscose fabrics were compared to each other. The analyzed samples were prepared by stippling a particular fabric with TiO2 nanoparticle sol (particle size 100 nm). Both spectrometers were calibrated with the aid of the same sets of authentic fabric samples previously analyzed by ICP OES after the microwave digestion. Average values of the Ti concentration calculated from five repeated measurements of the same sample obtained by LIBS and ED XRF were comparable for all types of the tested materials (100•(CTi-LIBS/CTi-ED XRF)) ≅ 96-109%), but the precision of analysis expressed as RSD (relative standard deviation) was usually better for ED XRF (RSDLIBS from 9 to 25%, RSDED XRF from 3 to 17%). Poor RSD values of LIBS measurements were observed mainly in the case of samples with lower areal weights. Limits of detection calculated as a triple standard deviation of five repeated measurements of Ti in a sample with the low concentration of the analyte were comparable for both methods (LODLIBS = from 15 to 97, and LODED XRF = from 21 to 64, all in mg/kg).

  9. Double pulse laser induced breakdown spectroscopy: A potential tool for the analysis of contaminants and macro/micronutrients in organic mineral fertilizers.

    PubMed

    Nicolodelli, Gustavo; Senesi, Giorgio Saverio; de Oliveira Perazzoli, Ivan Luiz; Marangoni, Bruno Spolon; De Melo Benites, Vinícius; Milori, Débora Marcondes Bastos Pereira

    2016-09-15

    Organic fertilizers are obtained from waste of plant or animal origin. One of the advantages of organic fertilizers is that, from the composting, it recycles waste-organic of urban and agriculture origin, whose disposal would cause environmental impacts. Fast and accurate analysis of both major and minor/trace elements contained in organic mineral and inorganic fertilizers of new generation have promoted the application of modern analytical techniques. In particular, laser induced breakdown spectroscopy (LIBS) is showing to be a very promising, quick and practical technique to detect and measure contaminants and nutrients in fertilizers. Although, this technique presents some limitations, such as a low sensitivity, if compared to other spectroscopic techniques, the use of double pulse (DP) LIBS is an alternative to the conventional LIBS in single pulse (SP). The macronutrients (Ca, Mg, K, P), micronutrients (Cu, Fe, Na, Mn, Zn) and contaminant (Cr) in fertilizer using LIBS in SP and DP configurations were evaluated. A comparative study for both configurations was performed using optimized key parameters for improving LIBS performance. The limit of detection (LOD) values obtained by DP LIBS increased up to seven times as compared to SP LIBS. In general, the marked improvement obtained when using DP system in the simultaneous LIBS quantitative determination for fertilizers analysis could be ascribed to the larger ablated mass of the sample. The results presented in this study show the promising potential of the DP LIBS technique for a qualitative analysis in fertilizers, without requiring sample preparation with chemical reagents.

  10. Multivariate approach to the chemical mapping of uranium in sandstone-hosted uranium ores analyzed using double pulse Laser-Induced Breakdown Spectroscopy

    NASA Astrophysics Data System (ADS)

    Klus, Jakub; Mikysek, Petr; Prochazka, David; Pořízka, Pavel; Prochazková, Petra; Novotný, Jan; Trojek, Tomáš; Novotný, Karel; Slobodník, Marek; Kaiser, Jozef

    2016-09-01

    The goal of this work is to provide high resolution mapping of uranium in sandstone-hosted uranium ores using Laser-Induced Breakdown Spectroscopy (LIBS) technique. In order to obtain chemical image with highest possible spatial resolution, LIBS system in orthogonal double pulse (DP LIBS) arrangement was employed. Owing to this experimental arrangement the spot size of 50 μm in diameter resulting in lateral resolution of 100 μm was reached. Despite the increase in signal intensity in DP LIBS modification, the detection of uranium is challenging. The main cause is the high density of uranium spectral lines, which together with broadening of LIBS spectral lines overreaches the resolution of commonly used spectrometers. It results in increased overall background radiation with only few distinguishable uranium lines. Three different approaches in the LIBS data treatment for the uranium detection were utilized: i) spectral line intensity, ii) region of apparent background and iii) multivariate data analysis. By utilizing multivariate statistical methods, a specific specimen features (in our case uranium content) were revealed by processing complete spectral information obtained from broadband echelle spectrograph. Our results are in a good agreement with conventional approaches such as line fitting and show new possibilities of processing spectral data in mapping. As a reference technique to LIBS was employed X-ray Fluorescence (XRF). The XRF chemical images used in this paper have lower resolution (approximately 1-2 mm per image point), nevertheless the elemental distribution is apparent and corresponds to presented LIBS experiments.

  11. Stimulated crystallization of melt-quenched Ge{sub 2}Sb{sub 2}Te{sub 5} films employing femtosecond laser double pulses

    SciTech Connect

    Cotton, Rebecca L.; Siegel, Jan

    2012-12-15

    The phase transformation of Ge{sub 2}Sb{sub 2}Te{sub 5} films from the melt-quenched amorphous phase into the crystalline phase induced by 800 nm, 100 fs laser pulses has been studied. For partly amorphized films, progressive crystallization could be induced by single pulses, which can be explained by growth of already existing crystalline embryos. For completely amorphized films, it was not possible to induce crystallization with one or two consecutive pulses; three pulses being the threshold for the onset of crystallization. By employing a fs laser double pulse with an adjustable inter-pulse delay, partial crystallization could be triggered for a delay range of 200 fs-100 ps, while for longer delays no crystallization was possible. The time window for stimulated crystallization can be related to the relaxation dynamics of free electrons excited by the first pulse, which are further excited by the second pulse still remaining in the excited state. Our results indicate that the lifetime of excited electrons in melt-quenched amorphous Ge{sub 2}Sb{sub 2}Te{sub 5} is Almost-Equal-To 100 ps.

  12. Direct electron-impact mechanism of excitation of mercury monobromide in a double-pulse dielectric-barrier-discharge HgBr lamp

    NASA Astrophysics Data System (ADS)

    Datsyuk, V. V.; Izmailov, I. A.; Naumov, V. V.; Kochelap, V. A.

    2016-08-01

    In a nonequlibrium plasma of a gas-discharge HgBr lamp, the terminal electronic state of the HgBr(B-X) radiative transition with a peak wavelength of 502 nm remains populated for a relatively long time and is repeatedly excited to the B state in collisions with plasma electrons. This transfer of the HgBr molecules from the ground state X to the excited state B is the main mechanism of formation of the light-emitting molecules especially when the lamp is excited by double current pulses. According to our simulations, due to the electron-induced transitions between HgBr(X) and HgBr(B), the output characteristics of the DBD lamp operating in a double-pulse regime are better than those of the lamp operating in a single-pulse regime. In the considered case, the peak power is calculated to increase by a factor of about 2 and the lamp efficiency increases by about 50%.

  13. Enhancement of Photoinduced Charge-Order Melting via Anisotropy Control by Double-Pulse Excitation in Perovskite Manganites: Pr_{0.6}Ca_{0.4}MnO_{3}.

    PubMed

    Yada, H; Ijiri, Y; Uemura, H; Tomioka, Y; Okamoto, H

    2016-02-19

    To control the efficiency of photoinduced charge-order melting in perovskite manganites, we performed femtosecond pump-probe spectroscopy using double-pulse excitation on Pr_{0.6}Ca_{0.4}MnO_{3}. The results revealed that the transfer of the spectral weight from the near-infrared to infrared region by the second pump pulse is considerably enhanced by the first pump pulse and that the suppression of crystal anisotropy, that is, the decrease of long-range lattice deformations due to the charge order by the first pump pulse is a key factor to enhance the charge-order melting. This double-pulse excitation method can be applied to various photoinduced transitions in complex materials with electronic and structural instabilities.

  14. Three-dimensional flow visualization of shock wave using double-pulsed holographic interferometry. II - Flow visualization for three-dimensional shock structures in rotating aeroengine fan blade rows

    NASA Astrophysics Data System (ADS)

    Yasu, Shohachi; Tamaki, Teiichi; Nagano, Susumu; Kashiwagi, Takao

    1990-09-01

    The growing demand for more fuel-efficient aero gas turbine engines has led to the need for a detailed understanding of the aerodynamic behavior of components. The optical technique of holography has recently achieved importance as a means of providing the experimental data necessary for the development and validation of relevant design calculation methods. This paper describes the double-pulsed holographic flow visualization technique which has been developed at IHI and provides information on 3-dimensional shock structures of the transonic flow region between the blades and shock/casing wall boundary layer interaction in rotating aeroengine fan at various rotor speeds and throttling conditions.

  15. INTERACTION OF LASER RADIATION WITH MATTER. LASER PLASMA: Change in the ionisation state of a near-surface laser-produced aluminium plasma in double-pulse ablation modes

    NASA Astrophysics Data System (ADS)

    Burakov, V. S.; Bokhonov, A. F.; Nedel'ko, M. I.; Tarasenko, N. V.

    2003-12-01

    The near-surface plasma produced upon irradiation of an aluminium target by two successive laser pulses with nonresonance and resonance wavelengths is studied by the spectroscopic and probe-assisted methods. The feasibility of increasing the ion fraction in the laser-produced plasma in double-pulse ablation modes is demonstrated. The conditions are determined under which processes on the surface as well as selective excitation and ionisation in the plasma have a determining effect on the formation of its ionisation state.

  16. First 2.2 micrometer results from the iota interferometer

    NASA Technical Reports Server (NTRS)

    Dyck, H. M.; Benson, J. A.; Carlton, N. P.; Coldwell, C.; Lacasse, M. G.; Nisenson, P.; Panasyuk, A.; Papaliolios, C.; Pearlman, R. D.; Reasenberg, R. D.

    1995-01-01

    We present the first infrared fringe visibility measurements made with the Infrared Optical Telescope Array on Mt. Hopkins. Effective temperatures are derived for RX Boo, RS Cnc, and Beta Peg. RX Boo is the coolest small-amplitude variable giant star to have an effective temperature determination. We compare the size of its photosphere at infrared wavelengths with the sizes of its SiO and H20 radio emission regions. We also discuss initial performance parameters for the interferometer.

  17. Scaling relationship and optimization of double-pulse electroporation.

    PubMed

    Sadik, Mohamed M; Yu, Miao; Zheng, Mingde; Zahn, Jeffrey D; Shan, Jerry W; Shreiber, David I; Lin, Hao

    2014-02-18

    The efficacy of electroporation is known to vary significantly across a wide variety of biological research and clinical applications, but as of this writing, a generalized approach to simultaneously improve efficiency and maintain viability has not been available in the literature. To address that discrepancy, we here outline an approach that is based on the mapping of the scaling relationships among electroporation-mediated molecular delivery, cellular viability, and electric pulse parameters. The delivery of Fluorescein-Dextran into 3T3 mouse fibroblast cells was used as a model system. The pulse was rationally split into two sequential phases: a first precursor for permeabilization, followed by a second one for molecular delivery. Extensive data in the parameter space of the second pulse strength and duration were collected and analyzed with flow cytometry. The fluorescence intensity correlated linearly with the second pulse duration, confirming the dominant role of electrophoresis in delivery. The delivery efficiency exhibited a characteristic sigmoidal dependence on the field strength. An examination of short-term cell death using 7-Aminoactinomycin D demonstrated a convincing linear correlation with respect to the electrical energy. Based on these scaling relationships, an optimal field strength becomes identifiable. A model study was also performed, and the results were compared with the experimental data to elucidate underlying mechanisms. The comparison reveals the existence of a critical transmembrane potential above which delivery with the second pulse becomes effective. Together, these efforts establish a general route to enhance the functionality of electroporation.

  18. Structural Analysis Using Phase-Stepped, Double Pulsed ESPI

    NASA Astrophysics Data System (ADS)

    Tyrer, John R.

    1990-04-01

    Optical whole-field testing techniques have been carrots dangled in front of engineers' noses for a considerable period of time. The promise of acquiring meaningful data without upsetting the component nor its environment, has significant attractions. ESPI technology has been modified and pursued with these goals in mind. This paper presents some of the recent work containing several developments which now make the engineering realisations a near term possibility. An overview of the correlation imaging mechanism is presented with a discussion on how this principle type of optical interferometer can be configured to provide the data necessary for analytical use. Attempts to produce instrumentation able to function outside the laboratory have required replacement of continuous wave lasers with Nd.YAG pulsed lasers. The new pulsed lasers are able to be combined with the computer based fringe pattern analysis which has been produced to suit the requirements of the engineer. Experimental results using such equipment are presented and further work is included which demonstrates the ability for speckle interferometry to produce three-dimensional analysis with the data being presented in conventional cartesian form.

  19. Recent Development of Component Technologies for 2 micrometer LIDAR at JPL

    NASA Technical Reports Server (NTRS)

    Forouhar, Siamak; Briggs, Ryan; Frez, Clifford; Bagheri, Mahmood; Ksendzov, Alexander; Menzies, Robert; Hyon, Jason

    2012-01-01

    Objective::Global-scale atmospheric measurements of Carbon Dioxide (CO2) and other Green House Gases with full diurnal, full latitude, all season coverage capability. Implementation: Use of the laser- based Integrated Path Differential Absorption (IPDA) method at 1.57 and 2.05 microns. Airborne lasers are needed to demonstrate instrument capabilities, risk reduction and satellite measurement validation.

  20. Sub-kHz Linewidth GaSb Semiconductor Diode Lasers Operating Near 2 Micrometers

    NASA Technical Reports Server (NTRS)

    Bagheri, Mahmood; Briggs, Ryan M.; Frez, Clifford; Ksendzov, Alexander; Forouhar, Siamak

    2012-01-01

    We report on the phase noise properties of DFB lasers operating near 2.0 microns. Measured noise spectra indicate intrinsic laser linewidths below 1 kHz. An effective linewidth of less than 200 kHz for 5 ms measurement times is estimated.

  1. Tunable cw Single-Frequency Source for Injection Seeding 2-micrometer Lasers

    DTIC Science & Technology

    1990-06-01

    CW DROs. Output frequency distributions -5- were measured with a 300-MHz-free- spectral -range scanning interferometer and a one- meter grating...monochromator. The pulsed DRO was remarkable constant both temporally and spectrally from shot to shot at 320 kHz repetition rate, but did have a tendency to...Earlier analyses 15.1 are extended to provide a quantitative description of spectral hops between adjacent axial modes and the larger discontinuous

  2. 2.5 MHz Line-Width High-energy, 2 Micrometer Coherent Wind Lidar Transmitter

    NASA Technical Reports Server (NTRS)

    Petros, Mulugeta; Yu, Jirong; Trieu, Bo; Bai, Yingxin; Petzar, Paul; Singh, Upendra N.; Reithmaier, Karl

    2007-01-01

    2 micron solid-state lasers are the primary choice for coherent Doppler wind detection. As wind lidars, they are used for wake vortex and clear air turbulence detection providing air transport safety. In addition, 2 micron lasers are one of the candidates for CO2 detection lidars. The rich CO2 absorption line around 2 micron, combined with the long upper state life of time, has made Ho based 2 micron lasers a viable candidate for CO2 sensing DIAL instrument. The design and fabrication of a compact coherent laser radar transmitter for Troposphere wind sensing is under way. This system is hardened for ground as well as airborne applications. As a transmitter for a coherent wind lidar, this laser has stringent spectral line width and beam quality requirements. Although the absolute wavelength does not have to be fixed for wind detection, to maximize return signal, the output wavelength should avoid atmospheric CO2 and H2O absorption lines. The base line laser material is Ho:Tm:LuLF which is an isomorph of Ho:Tm:YLF. LuLF produces 20% more output power than Ho:Tm:YLF. In these materials the Tm absorption cross-section, the Ho emission cross-section, the Tm to Ho energy transfer parameters and the Ho (sup 5) I (sub 7) radiative life time are all identical. However, the improved performance of the LuLF is attributed to the lower thermal population in the (sup 5) I (sub 8) manifold. It also provides higher normal mode to Q-switch conversion than YLF at high pump energy indicating a lower up-conversion. The laser architecture is composed of a seed laser, a ring oscillator, and a double pass amplifier. The seed laser is a single longitudinal mode with a line width of 13 KHz. The 100mJ class oscillator is stretched to 3 meters to accommodate the line-width requirement without compromising the range resolution of the instrument. The amplifier is double passed to produce greater than 300mJ energy.

  3. Thulium-doped fibre broadband source for spectral region near 2 micrometers

    NASA Astrophysics Data System (ADS)

    Písařík, M.; Peterka, P.; Aubrecht, J.; Cajzl, J.; Benda, A.; Mareš, D.; Todorov, F.; Podrazký, O.; Honzátko, P.; Kašík, I.

    2016-12-01

    We demonstrated two methods of increasing the bandwidth of a broadband light source based on amplified spontaneous emission in thulium-doped fibres. Firstly, we have shown by means of a comprehensive numerical model that the full-width at half maximum of the thulium-doped fibre based broadband source can be more than doubled by using specially tailored spectral filter placed in front of the mirror in a double-pass configuration of the amplified spontaneous emission source. The broadening can be achieved with only a small expense of the output power. Secondly, we report results of the experimental thulium-doped fibre broadband source, including fibre characteristics and performance of the thulium-doped fibre in a ring laser setup. The spectrum broadening was achieved by balancing the backward amplified spontaneous emission with back-reflected forward emission.

  4. A Novel Triple-Pulsed 2-micrometer Lidar for Simultaneous and Independent CO2 and H2O Column Measurement

    NASA Technical Reports Server (NTRS)

    Yu, Jirong; Singh, Upendra; Petros, Mulugeta; Refaat, Tamer

    2015-01-01

    The study of global warming needs precisely and accurately measuring greenhouse gases concentrations in the atmosphere. CO2 and H2O are important greenhouse gases that significantly contribute to the carbon cycle and global radiation budget on Earth. NRC Decadal Survey recommends a mission for Active Sensing of Carbon Dioxide (CO2) over Nights, Days and Seasons (ASCENDS). 2 micron laser is a viable IPDA transmitter to measure CO2 and H2O column density from space. The objective is to demonstrate a first airborne direct detection 2 micron IPDA lidar for CO2 and H2O measurements.

  5. Efficient Tm:Fiber Pumped Solid-State Ho:YLF 2-micrometer Laser for Remote Sensing Applications

    NASA Technical Reports Server (NTRS)

    Singh, Upendra N.; Bai, Yingxin; Yu, Jirong; Petros, Mulugeta

    2012-01-01

    An efficient 19 W, TEM(sub 00) mode, Ho:YLF laser pumped by continuous wave Tm:fiber laser has been demonstrated at the room temperature. The slope efficiency and optical-to-optical efficiency are 65% and 55%, respectively.

  6. The 0.5 micrometer-2.2 micrometer Scattered Light Spectrum of the Disk Around TW Hya

    NASA Technical Reports Server (NTRS)

    Debes, John H.; Jang-Condell, Hannah; Weinberger, Alycia J.; Roberg, Aki; Schneider, Glenn

    2012-01-01

    We present a 0.5-2.2micron scattered light spectrum of the circumstellar disk around TW Hya from a combination of spatially resolved HST STIS spectroscopy and NICMOS coronagraphic images of the disk. \\Ve investigate the morphology at the disk at distances> 40 AU over this wide range of wavelengths. We measure the surface brightness, azimuthal symmetry, and spectral character of the disk as a function of radius. We find that the scattering efficiency of the dust is largely neutral to blue over the observed wavelengths. We find a good fit to the data over a wide range of distances from the star if we use a model disk with a partial gap of 30% depth at 80 AU and with steep disk truncation exterior to 100 AU. If the gap is caused by a planetary companion in the process of accreting disk gas, it must be less than 20 Solar mass.

  7. Atmospheric-water absorption features near 2.2 micrometers and their importance in high spectral resolution remote sensing

    NASA Technical Reports Server (NTRS)

    Kruse, F. A.; Clark, R. N.

    1986-01-01

    Selective absorption of electromagnetic radiation by atmospheric gases and water vapor is an accepted fact in terrestrial remote sensing. Until recently, only a general knowledge of atmospheric effects was required for analysis of remote sensing data; however, with the advent of high spectral resolution imaging devices, detailed knowledge of atmospheric absorption bands has become increasingly important for accurate analysis. Detailed study of high spectral resolution aircraft data at the U.S. Geological Survey has disclosed narrow absorption features centered at approximately 2.17 and 2.20 micrometers not caused by surface mineralogy. Published atmospheric transmission spectra and atmospheric spectra derived using the LOWTRAN-5 computer model indicate that these absorption features are probably water vapor. Spectral modeling indicates that the effects of atmospheric absorption in this region are most pronounced in spectrally flat materials with only weak absorption bands. Without correction and detailed knowledge of the atmospheric effects, accurate mapping of surface mineralogy (particularly at low mineral concentrations) is not possible.

  8. High-intensity double-pulse X-ray free-electron laser

    DOE PAGES

    Marinelli, A.; Ratner, D.; Lutman, A. A.; ...

    2015-03-06

    The X-ray free-electron laser has opened a new era for photon science, improving the X-ray brightness by ten orders of magnitude over previously available sources. Similar to an optical laser, the spectral and temporal structure of the radiation pulses can be tailored to the specific needs of many experiments by accurately manipulating the lasing medium, that is, the electron beam. Here we report the generation of mJ-level two-colour hard X-ray pulses of few femtoseconds duration with an XFEL driven by twin electron bunches at the Linac Coherent Light Source. This performance represents an improvement of over an order of magnitudemore » in peak power over state-of-the-art two-colour XFELs. The unprecedented intensity and temporal coherence of this new two-colour X-ray free-electron laser enable an entirely new set of scientific applications, ranging from X-ray pump/X-ray probe experiments to the imaging of complex biological samples with multiple wavelength anomalous dispersion.« less

  9. Velocity Interferometer blanking due to preheating in a double pulse planar experiment

    SciTech Connect

    Laffite, S.; Combis, P.; Clerouin, J.; Recoules, V.; Rousseaux, C.; Videau, L.; Baton, S. D.; Koenig, M.

    2014-08-15

    Optical diagnostics, such as VISAR (Velocity Interferometer System for Any Reflector) or SOP (Streaked Optical Pyrometry), have become essential in shock timing experiments. Their high precision allows for accurate measurements of shock velocities, chronometry, and brightness temperature. However, in some instances, these measurements can be compromised. In planar shock coalescence experiments recently performed at the LULI facility [Baton et al., Phys. Rev. Lett. 108, 195002 (2012)], VISAR signal loss was observed. In these experiments, a strong shock launched by a high-intensity spike catches up with a previously shock launched by an earlier, low-intensity beam. The disappearance of the VISAR signal is attributed to a preheating of the coronal plasma by x-rays generated by the high intensity spike. The signal does not disappear if the high-intensity spike starts after VISAR probe beam begins to reflect off of the first shock. The VISAR diagnostic, modeled using an assessment of the optical index in quartz, compares favorably to experimental results. This provides evidence that x-ray preheating can cause blanking of the VISAR signal in quartz.

  10. High-intensity double-pulse X-ray free-electron laser

    SciTech Connect

    Marinelli, A.; Ratner, D.; Lutman, A. A.; Turner, J.; Welch, J.; Decker, F. J.; Loos, H.; Behrens, C.; Gilevich, S.; Miahnahri, A. A.; Vetter, S.; Maxwell, T. J.; Ding, Y.; Coffee, R.; Wakatsuki, S.; Huang, Z.

    2015-03-06

    The X-ray free-electron laser has opened a new era for photon science, improving the X-ray brightness by ten orders of magnitude over previously available sources. Similar to an optical laser, the spectral and temporal structure of the radiation pulses can be tailored to the specific needs of many experiments by accurately manipulating the lasing medium, that is, the electron beam. Here we report the generation of mJ-level two-colour hard X-ray pulses of few femtoseconds duration with an XFEL driven by twin electron bunches at the Linac Coherent Light Source. This performance represents an improvement of over an order of magnitude in peak power over state-of-the-art two-colour XFELs. The unprecedented intensity and temporal coherence of this new two-colour X-ray free-electron laser enable an entirely new set of scientific applications, ranging from X-ray pump/X-ray probe experiments to the imaging of complex biological samples with multiple wavelength anomalous dispersion.

  11. Velocity Interferometer blanking due to preheating in a double pulse planar experiment

    NASA Astrophysics Data System (ADS)

    Laffite, S.; Baton, S. D.; Combis, P.; Clerouin, J.; Koenig, M.; Recoules, V.; Rousseaux, C.; Videau, L.

    2014-08-01

    Optical diagnostics, such as VISAR (Velocity Interferometer System for Any Reflector) or SOP (Streaked Optical Pyrometry), have become essential in shock timing experiments. Their high precision allows for accurate measurements of shock velocities, chronometry, and brightness temperature. However, in some instances, these measurements can be compromised. In planar shock coalescence experiments recently performed at the LULI facility [Baton et al., Phys. Rev. Lett. 108, 195002 (2012)], VISAR signal loss was observed. In these experiments, a strong shock launched by a high-intensity spike catches up with a previously shock launched by an earlier, low-intensity beam. The disappearance of the VISAR signal is attributed to a preheating of the coronal plasma by x-rays generated by the high intensity spike. The signal does not disappear if the high-intensity spike starts after VISAR probe beam begins to reflect off of the first shock. The VISAR diagnostic, modeled using an assessment of the optical index in quartz, compares favorably to experimental results. This provides evidence that x-ray preheating can cause blanking of the VISAR signal in quartz.

  12. Charge accumulation at the interface of polymer/fullerene studied by double-pulse photocurrent responses

    NASA Astrophysics Data System (ADS)

    Jin, Hui; Hou, Yan-Bing; Meng, Xian-Guo; Teng, Feng

    2008-12-01

    Transport mechanism of photogenerated carriers in composite films based on Poly [2-methoxy,5-(2'-ethylhexyloxy)-1,4,-phenylene-vinylene] (MEH-PPV) doped with fullerene (C 60) is investigated by double-light-pulse induced photocurrent responses. Charge accumulation is found in low concentration ranges of C 60, while at high C 60 concentration (50 wt%), the same feature is completely absent. Charge accumulation at the interface between MEH-PPV and C 60 directly reduces the external quantum efficiency of composite devices.

  13. Optimization of A 2-Micron Laser Frequency Stabilization System for a Double-Pulse CO2 Differential Absorption Lidar

    NASA Technical Reports Server (NTRS)

    Chen, Songsheng; Yu, Jirong; Bai, Yingsin; Koch, Grady; Petros, Mulugeta; Trieu, Bo; Petzar, Paul; Singh, Upendra N.; Kavaya, Michael J.; Beyon, Jeffrey

    2010-01-01

    A carbon dioxide (CO2) Differential Absorption Lidar (DIAL) for accurate CO2 concentration measurement requires a frequency locking system to achieve high frequency locking precision and stability. We describe the frequency locking system utilizing Frequency Modulation (FM), Phase Sensitive Detection (PSD), and Proportional Integration Derivative (PID) feedback servo loop, and report the optimization of the sensitivity of the system for the feed back loop based on the characteristics of a variable path-length CO2 gas cell. The CO2 gas cell is characterized with HITRAN database (2004). The method can be applied for any other frequency locking systems referring to gas absorption line.

  14. Atomic Processes in Emission Characteristics of a Lithium Plasma Plume Formed by Double-Pulse Laser Ablation

    NASA Astrophysics Data System (ADS)

    Sivakumaran, V.; Ajai, Kumar; K. Singh, R.; Prahlad, V.; C. Joshi, H.

    2013-03-01

    High resolution spectral analysis of lithium plasma formed by single and double laser ablation has been undertaken to understand the plume-laser interaction, especially at the early stages of the plasma plume. In order to identify different atomic processes in evolving plasma, time resolved spectral emission studies at different inter-pulse delays have been performed for ionic and neutral lithium lines emitting from different levels. Along with the enhancement in emission intensity, a large line broadening and spectral shift, especially in the case of excited state transition Li I 610.3 nm have been observed in the presence of the second pulse. This broadening and shift gradually decrease with increasing time delay. Another interesting feature is the appearance of a multi-component structure in the ionic line at 548.4 nm and these components change conversely into a single structure at the later stages of the plasma. The multi-component structures are correlated with the presence of different velocity (temperature) distributions in non-LTE conditions. Atomic analyses by computing photon emissivity coefficients with an ADAS code have been used to identify the above processes.

  15. Enhanced X-ray emission from laser-produced gold plasma by double pulses irradiation of nano-porous targets

    NASA Astrophysics Data System (ADS)

    Fazeli, R.

    2017-02-01

    Enhancement of the soft X-ray emission including free-free, free-bound and bound-bound emissions from Au nano-porous targets irradiated by single and double laser pulses is studied through numerical simulations. Laser pulses of duration 2 ns are used in calculations considering different prepulse intensities and a fixed intensity of 1013 Wcm-2 for the main pulse. The effects of prepulse intensity and time separation between laser pulses are studied for targets of different porosities. Results show that the X-ray yield can be enhanced significantly by a nano-porous target having optimum initial density. Such enhancement can be more improved when double laser pulses with appropriate delay time and intensities irradiate nano-porous targets. It is shown that the enhancement will be reduced when the prepulse intensity is greater than a specific value.

  16. High efficiency 2 micrometer laser utilizing wing-pumped Tm{sup 3+} and a laser diode array end-pumping architecture

    DOEpatents

    Beach, R.J.

    1997-11-18

    Wing pumping a Tm{sup 3+} doped, end pumped solid state laser generates 2 {micro}m laser radiation at high average powers with high efficiency. Using laser diode arrays to end-pump the laser rod or slab in the wing of the Tm{sup 3+} absorption band near 785 nm results in 2-for-1 quantum efficiency in Tm{sup 3+} because high Tm{sup 3+} concentrations can be used. Wing pumping allows the thermal power generated in the rod or slab to be distributed over a large enough volume to make thermal management practical in the laser gain medium even at high average power operation. The approach is applicable to CW, Q-switched, and rep-pulsed free-laser operation. 7 figs.

  17. High efficiency 2 micrometer laser utilizing wing-pumped Tm.sup.3+ and a laser diode array end-pumping architecture

    DOEpatents

    Beach, Raymond J.

    1997-01-01

    Wing pumping a Tm.sup.3+ doped, end pumped solid state laser generates 2 .mu.m laser radiation at high average powers with high efficiency. Using laser diode arrays to end-pump the laser rod or slab in the wing of the Tm.sup.3+ absorption band near 785 nm results in 2-for-1 quantum efficiency in Tm.sup.3+ because high Tm.sup.3+ concentrations can be used. Wing pumping allows the thermal power generated in the rod or slab to be distributed over a large enough volume to make thermal management practical in the laser gain medium even at high average power operation. The approach is applicable to CW, Q-switched, and rep-pulsed free-laser operation.

  18. Growth and Optimization of 2 Micrometers InGaSb/AlGaSb Quantum-Well-Based VECSELs on GaAs/AlGaAs DBRs

    DTIC Science & Technology

    2013-08-01

    also address the issue of nonreproducible relaxation in the antimonide buffer . If the antimonide buffer does not relax reproducibly, then the in-plane...lattice constant of the buffer will be changed from growth to growth, also affecting the QW strain between growths. Such issues lead to performance...variation in the gain peak is much more catastrophic. Thus, any metamorphic buffer -based approach has to result in two con- ditions in the active region: 1

  19. Photoconductivity of CdTe Nanocrystal-Based Thin Films. Te2- Ligands Lead To Charge Carrier Diffusion Lengths Over 2 Micrometers

    SciTech Connect

    Crisp, Ryan W.; Callahan, Rebecca; Reid, Obadiah G.; Dolzhnikov, Dmitriy S.; Talapin, Dmitri V.; Rumbles, Garry; Luther, Joseph M.; Kopidakis, Nikos

    2015-11-16

    We report on photoconductivity of films of CdTe nanocrystals (NCs) using time-resolved microwave photoconductivity (TRMC). Spherical and tetrapodal CdTe NCs with tunable size-dependent properties are studied as a function of surface ligand (including inorganic molecular chalcogenide species) and annealing temperature. Relatively high carrier mobility is measured for films of sintered tetrapod NCs (4 cm2/(V s)). Our TRMC findings show that Te2- capped CdTe NCs show a marked improvement in carrier mobility (11 cm2/(V s)), indicating that NC surface termination can be altered to play a crucial role in charge-carrier mobility even after the NC solids are sintered into bulk films.

  20. An in vitro Corneal Model with a Laser Damage Threshold at 2 Micrometers That is Similar to That in the Rabbit

    DTIC Science & Technology

    2007-11-01

    data in the literature. 15. SUBJECT TERMS corneal organotypic culture, laser, threshold, thermography , Probit 16. SECURITY CLASSIFICATION OF...literature. Keywords: corneal organotypic culture, laser, threshold, thermography , Probit 1. INTRODUCTION Use of lasers has become commonplace...temperature increases from exposure to the 2-µm laser were measured using the IR camera during laser exposure to membranes that were dry , wetted from

  1. Spectral modification of the laser emission of a terahertz quantum cascade laser induced by broad-band double pulse injection seeding

    SciTech Connect

    Markmann, Sergej Nong, Hanond Hekmat, Negar; Jukam, Nathan; Pal, Shovon; Scholz, Sven; Kukharchyk, Nadezhda; Ludwig, Arne; Wieck, Andreas D.; Dhillon, Sukhdeep; Tignon, Jérôme; Marcadet, Xavier; Bock, Claudia; Kunze, Ulrich

    2015-09-14

    We demonstrate by injection seeding that the spectral emission of a terahertz (THz) quantum cascade laser (QCL) can be modified with broad-band THz pulses whose bandwidths are greater than the QCL bandwidth. Two broad-band THz pulses delayed in time imprint a modulation on the single THz pulse spectrum. The resulting spectrum is used to injection seed the THz QCL. By varying the time delay between the THz pulses, the amplitude distribution of the QCL longitudinal modes is modified. By applying this approach, the QCL emission is reversibly switched from multi-mode to single mode emission.

  2. Continuous Registration of Membrane Input Resistances of Small Plant Cells Using a Double-Pulse Current Clamp Technique for Single-Electrode Impalements 12

    PubMed Central

    Schefczik, Kurt; Simonis, Wilhelm; Schiebe, Michael

    1983-01-01

    To measure the cell input resistance in Elodea leaf cells, a new single-microelectrode method was explored by comparing the results with conventional two-microelectrode experiments. The new method takes advantage of the difference in the frequency response curves between electrode and cell impedances. By application of electrical stimuli, which contain specific frequency bands, the different impedances can be analyzed separately. To get a distinct separation in the frequency response of cell and electrode, respectively, the electrode capacitance has to be compensated during the impalement. Different time constants of the cell membrane can be accounted for by adjustment of the stimulus length. It is shown that both the single- and the double-electrode method yield the same results, even if the cell input resistances change considerably during the course of the experiment. This demonstrates the usefulness of the new single-electrode method for continuous measurements of cell membrane resistances, especially in cells so small that the double-electrode method is no longer applicable. Images Fig. 4 Fig. 2 PMID:16663008

  3. Characterization of Transducer Performance and Narrowband Transient Ultrasonic Fields in Metals by Rayleigh-Sommerfeld Backpropagation of Compression Acoustic Waves Measured with Double-Pulsed Tv Holography

    NASA Astrophysics Data System (ADS)

    Trillo, Cristina; Doval, Ángel F.; Fernández, José L.; Rodríguez-Gómez, Pablo; López-Vázquez, J. Carlos

    2014-10-01

    This article presents a method aimed at the characterization of the narrowband transient acoustic field radiated by an ultrasonic plane transducer into a homogeneous, isotropic and optically opaque prismatic solid, and the assessment of the performance of the acoustic source. The method relies on a previous technique based on the full-field optical measurement of an acoustic wavepacket at the surface of a solid and its subsequent numerical backpropagation within the material. The experimental results show that quantitative transversal and axial profiles of the complex amplitude of the beam can be obtained at any plane between the measurement and excitation surfaces. The reconstruction of the acoustic field at the transducer face, carried out on a defective transducer model, shows that the method could also be suitable for the nondestructive testing of the performance of ultrasonic sources. In all cases, the measurements were performed with the transducer working under realistic loading conditions.

  4. Corticomotor control of lumbar multifidus muscles is impaired in chronic low back pain: concurrent evidence from ultrasound imaging and double-pulse transcranial magnetic stimulation.

    PubMed

    Massé-Alarie, Hugo; Beaulieu, Louis-David; Preuss, Richard; Schneider, Cyril

    2016-04-01

    Chronic low back pain (CLBP) is often associated with impaired control of deep trunk muscles and reorganization of the primary motor areas (M1). Precisely, functional changes of the lumbar multifidus muscles (MF) involved in spine stability may be of special interest in rehabilitation. Therefore, we tested MF corticomotor control using double transcranial magnetic stimulation (TMS) paradigms for the first time in this muscle and examined its link with MF volitional activation. Eleven individuals with lateralized CLBP and 13 pain-free participants were recruited. Ultrasound imaging enabled measurement of MF volitional isometric contraction in prone lying. TMS of MF M1 area was used to test hemispheric excitability and mechanisms in relation to motor programming, i.e., active motor threshold (AMT), amplitude of motor-evoked potentials and short-interval intracortical inhibition (SICI) and facilitation (SICF). In CLBP, SICI level was lower in the left hemisphere and MF volitional contraction was not related to AMT (M1 excitability), conversely to what was observed in the pain-free group. No other between-group difference was detected. These original findings support a plasticity of cortical maps controlling paravertebral muscles and likely including a different motor strategy for the control of MF. Changes of M1 function may thus underlie impaired motor control of lumbopelvic spine and pain persistence in CLBP.

  5. Quantitative analysis of deuterium in zircaloy using double-pulse laser-induced breakdown spectrometry (LIBS) and helium gas plasma without a sample chamber.

    PubMed

    Suyanto, H; Lie, Z S; Niki, H; Kagawa, K; Fukumoto, K; Rinda, Hedwig; Abdulmadjid, S N; Marpaung, A M; Pardede, M; Suliyanti, M M; Hidayah, A N; Jobiliong, E; Lie, T J; Tjia, M O; Kurniawan, K H

    2012-03-06

    A crucial safety measure to be strictly observed in the operation of heavy-water nuclear power plants is the mandatory regular inspection of the concentration of deuterium penetrated into the zircaloy fuel vessels. The existing standard method requires a tedious, destructive, and costly sample preparation process involving the removal of the remaining fuel in the vessel and melting away part of the zircaloy pipe. An alternative method of orthogonal dual-pulse laser-induced breakdown spectrometry (LIBS) is proposed by employing flowing atmospheric helium gas without the use of a sample chamber. The special setup of ps and ns laser systems, operated for the separate ablation of the sample target and the generation of helium gas plasma, respectively, with properly controlled relative timing, has succeeded in producing the desired sharp D I 656.10 nm emission line with effective suppression of the interfering H I 656.28 nm emission by operating the ps ablation laser at very low output energy of 26 mJ and 1 μs ahead of the helium plasma generation. Under this optimal experimental condition, a linear calibration line is attained with practically zero intercept and a 20 μg/g detection limit for D analysis of zircaloy sample while creating a crater only 10 μm in diameter. Therefore, this method promises its potential application for the practical, in situ, and virtually nondestructive quantitative microarea analysis of D, thereby supporting the more-efficient operation and maintenance of heavy-water nuclear power plants. Furthermore, it will also meet the anticipated needs of future nuclear fusion power plants, as well as other important fields of application in the foreseeable future.

  6. Fringe localization requirements for three-dimensional flow visualization of shock waves in diffuse-illumination double-pulse holographic interferometry

    NASA Technical Reports Server (NTRS)

    Decker, A. J.

    1982-01-01

    A theory of fringe localization in rapid-double-exposure, diffuse-illumination holographic interferometry was developed. The theory was then applied to compare holographic measurements with laser anemometer measurements of shock locations in a transonic axial-flow compressor rotor. The computed fringe localization error was found to agree well with the measured localization error. It is shown how the view orientation and the curvature and positional variation of the strength of a shock wave are used to determine the localization error and to minimize it. In particular, it is suggested that the view direction not deviate from tangency at the shock surface by more than 30 degrees.

  7. Double nanosecond pulses generation in ytterbium fiber laser

    NASA Astrophysics Data System (ADS)

    Veiko, V. P.; Lednev, V. N.; Pershin, S. M.; Samokhvalov, A. A.; Yakovlev, E. B.; Zhitenev, I. Yu.; Kliushin, A. N.

    2016-06-01

    Double pulse generation mode for nanosecond ytterbium fiber laser was developed. Two sequential 60-200 ns laser pulses with variable delay between them were generated by acousto-optic modulator opening with continuous diode pumping. A custom radio frequency generator was developed to produce two sequential "opening" radio pulses with a delay of 0.2-1 μs. It was demonstrated that double pulse generation did not decrease the average laser power while providing the control over the laser pulse power profile. Surprisingly, a greater peak power in the double pulse mode was observed for the second laser pulse. Laser crater studies and plasma emission measurements revealed an improved efficiency of laser ablation in the double pulse mode.

  8. Single and double long pulse laser ablation of aluminum induced in air and water ambient

    NASA Astrophysics Data System (ADS)

    Akbari Jafarabadi, Marzieh; Mahdieh, Mohammad Hossein

    2017-02-01

    In this paper, single pulse and double pulse laser ablation of an aluminum target in two interaction ambient was investigated experimentally. The interaction was performed by nanosecond Nd:YAG laser beam in air and four depths (i.e. 9, 13, 17, and 21 mm) of distilled water ambient. The irradiation was carried out in single and collinear double pulse configurations in both air and liquid ambient. Crater geometry (depth and diameter) was measured by an optical microscope. The results indicated that the crater geometry strongly depends on both single pulse and double pulse configurations and interaction ambient. In single pulse regime, the crater diameter is higher for all water depths compared to that of air. However, the crater depth, depend on water depth, is higher or lower than the crater depth in air. In double pulse laser ablation, there are greater values for both crater diameters and crater depths in the water.

  9. Excitability in a quantum dot semiconductor laser with optical injection.

    PubMed

    Goulding, D; Hegarty, S P; Rasskazov, O; Melnik, S; Hartnett, M; Greene, G; McInerney, J G; Rachinskii, D; Huyet, G

    2007-04-13

    We experimentally analyze the dynamics of a quantum dot semiconductor laser operating under optical injection. We observe the appearance of single- and double-pulse excitability at one boundary of the locking region. Theoretical considerations show that these pulses are related to a saddle-node bifurcation on a limit cycle as in the Adler equation. The double pulses are related to a period-doubling bifurcation and occur on the same homoclinic curve as the single pulses.

  10. Measurement and Generation of Ultra-High Power Fiber Laser Pulses by Coherent Combination

    DTIC Science & Technology

    2010-06-01

    through a Michelson interferometer and generated a double pulse as shown in Figure 10. Figure 10. Experimental setup for testing and calibrating...Measuring the Free Spectral Range of the VIPA etalons Using the spectral fringes generated by the Michelson interferometer , we can quantify the spectral...Testing the FROG To test the FROG, we again used use the double pulse from a Michelson interferometer , which yields a FROG trace unlikely to occur by

  11. Development of Mini-LIA and Primary Experiments

    NASA Astrophysics Data System (ADS)

    Cheng, Cheng; Liao, Shu-Qing; Zheng, Shu-Xin; Lin, Yu-Zheng; Tang, Chuan-Xiang; Jing, Xiao-Bing; Mu, Fan; Pan, Hai-Feng; Zhang, Kai-Zhi; Shi, Jin-Shui; Deng, Jian-Jun

    2009-09-01

    Mini-LIA is a miniature of a linear induction accelerator developed by China Academy of Engineering Physics and Tsinghua University in 2007. It has been constructed with a thermionic cathode in an electron injector and a metglas core in the induction accelerator cavities. A double-pulsed electron beam was produced for the first time in China on the Mini-LIA with a thermionic cathode in the electron gun and a metglas core in the induction accelerator cavities. A double-pulsed beam current of more than 1.1 A was obtained on condition of 80 kV double-pulsed high voltage produced by pulsed power system supplying to the injector and accelerating modules. Some primary experiments for measuring the parameters of Mini-LIA has been performed, and some beam characterizations of Mini-LIA are presented. Further improvement is underway.

  12. Femtosecond laser high-efficiency drilling of high-aspect-ratio microholes based on free-electron-density adjustments.

    PubMed

    Jiang, Lan; Fang, Juqiang; Cao, Qiang; Zhang, Kaihu; Wang, Peng; Yu, Yanwu; Huang, Qiang; Lu, Yongfeng

    2014-11-01

    We studied the micromachining of high-aspect-ratio holes in poly(methylmethacrylate) using a visible double-pulse femtosecond laser based on free-electron-density adjustments. Hole depth and aspect ratio increased simultaneously upon decreasing the wavelength in the visible-light zone. When the pulse energy reached a high level, the free-electron density was adjusted by using a double-pulse laser, which induced fewer free electrons, a lower reflectivity plasma plume, and more pulse energy deposition in the solid bottom. Thus, the aspect ratio of the hole was improved considerably. At a moderate pulse energy level, a 1.3-1.4 times enhancement of both the ablation depth and the aspect ratio was observed when the double-pulse delay was set between 100 and 300 fs, probably due to an enhanced photon-electron coupling effect through adjusting the free-electron density. At a lower pulse energy level, this effect also induced the generation of a submicrometer string. In addition, the ablation rate was improved significantly by using visible double pulses.

  13. Ultrastable reference pulser for high-resolution spectrometers

    NASA Technical Reports Server (NTRS)

    Brenner, R.; Lenkszus, F. R.; Sifter, L. L.; Strauss, M. G.

    1970-01-01

    Solid-state double-pulse generator for a high resolution semiconductor detector meets specific requirements for resolution /0.05 percent/, amplitude range /0.1-13 MeV/, and repetition rate /0.1-1000 pulses per second/. A tag pulse is generated in coincidence with each reference pulse.

  14. Holographic cinematography and its applications

    NASA Astrophysics Data System (ADS)

    Smigielski, P.; Fagot, H.; Albe, F.

    1986-08-01

    Recording of single-exposure cineholograms of living bodies on 126-mm films, at a repetition rate of 25 holograms per second with the help of a frequency-doubled pulse YAG-laser; and recording of double-exposure cineholograms of reflecting moving objects for medical and industrial applications are reported. Limitations of 3D movies are described.

  15. Vibrational Schroedinger Cats

    NASA Technical Reports Server (NTRS)

    Kis, Z.; Janszky, J.; Vinogradov, An. V.; Kobayashi, T.

    1996-01-01

    The optical Schroedinger cat states are simple realizations of quantum states having nonclassical features. It is shown that vibrational analogues of such states can be realized in an experiment of double pulse excitation of vibrionic transitions. To track the evolution of the vibrational wave packet we derive a non-unitary time evolution operator so that calculations are made in a quasi Heisenberg picture.

  16. LGB neutron detector

    NASA Astrophysics Data System (ADS)

    Quist, Nicole

    2012-10-01

    The double pulse signature of the Gadolinium Lithium Borate Cerium doped plastic detector suggests its effectiveness for analyzing neutrons while providing gamma ray insensitivity. To better understand this detector, a californium gamma/neutron time of flight facility was constructed in our lab. Reported here are efforts to understand the properties and applications of the LGB detector with regards to neutron spectroscopy.

  17. Application of 2-um wavelength holmium lasers for treatment of skin diseases

    NASA Astrophysics Data System (ADS)

    Shcherbakov, Ivan A.; Klimov, Igor V.; Tsvetkov, Vladimir B.; Nerobeev, Alexander I.; Sadovnikova, Lija B.; Eliseenko, Vladimir I.

    1994-09-01

    Theoretical and experimental analysis of the efficiency of application of 2 micrometers pulsed holmium laser for cosmetic and plastic surgery and dermatology is carried out. Preliminary experiments were carried out on rats. Solid state 2 micrometers pulsed laser was allowed to operate in free running mode with pulse energy up to 1.5 J and pulse repetition rate up to 5 Hz. To deliver emission to the object a flexible quartz fiber without further focusing of 2.5 m in length and 400 micrometers of the core diameter was used. The effect of the different power density emission on the skin was studied. The second stage was the study of the influence of 2 micrometers emission on human skin. The results of the removal of hemangioma, papilloma, telangiectasia, nevus, nevus acantholytic, xanthelasma palpebral, verruca, chloasma, pigmental spots, tattoos, etc. are presented. Precision, simplicity, efficiency, and the high cosmetic effect of these operations is noted.

  18. ISO observations of Titan with SWS/grating

    NASA Technical Reports Server (NTRS)

    Coustenis, A.; Encrenaz, T.; Salama, A.; Lellouch, E.; Gautier, D.; Kessler, M. F.; deGraauw, T.; Samuelson, R. E.; Bjoraker, G.; Orton, G.

    1997-01-01

    The observations of Titan performed by the Infrared Space Observatory (ISO) short wavelength spectrometer (SWS), in the 2 micrometer to 45 micrometer region using the grating mode, are reported on. Special attention is given to data from Titan concerning 7 micrometer to 45 micrometer spectral resolution. Future work for improving Titan's spectra investigation is suggested.

  19. DIFFERENTIAL PULMONARY INFLAMMATION AND IN VITRO CYTOTOXICITY BY SIZE-FRACTIONATED FLY ASH PARTICLES FROM PULVERIZED COAL COMBUSTION

    EPA Science Inventory

    The paper presents results of research on the adverse health effects associated with exposure to airborne particulate matter. Pulmonary inflammatory responses were examined in CDI mice after intratracheal instillation of 25 or 100 micrograms of ultrafine (<0.2 micrometers), fine ...

  20. Can We Detect Carbonate and Sulfate Minerals on the Surface of Mars by Raman Spectroscopy?

    NASA Technical Reports Server (NTRS)

    Kuebler, K. E.; Wang, A.; Abbott, K.; Haskin, L. A.

    2001-01-01

    Raman spectra of micrometer-sized grains of calcite, epsomite, quartz, and olivine show no peak shift relative to larger crystals and no peak broadening at least down to 2 micrometers, which bodes well for the Raman analysis of martian soils. Additional information is contained in the original extended abstract.

  1. Holographic flow visualization at the Langley Expansion Tube

    NASA Astrophysics Data System (ADS)

    Goad, W. K.; Burner, A. W.

    1981-06-01

    A holographic system used for flow visualization at the Langley Expansion Tube is described. A ruby laser which can be singly or doubly pulsed during the short run time of less than 300 microns is used as the light source. With holography, sensitivity adjustments can be optimized after a run instead of before a run as with conventional flow visualization techniques. This results in an increased reliability of the flow visualization available for the study of real-gas effects on flow about models. Holographic techniques such as single-plate schlieren and shadowgraph, two plate interferometry, double pulse interferometry for perfect infinite-fringe interferograms, and double-pulse interferometry used to examine changes in the flow over a short time period are described and examples presented.

  2. Dynamics of optical breakdown in air induced by single and double nanosecond laser pulses

    SciTech Connect

    Mahdieh, Mohammad Hossein Akbari Jafarabadi, Marzieh

    2015-12-15

    In this paper, an optical breakdown in air induced by single and double nanosecond laser pulses was studied. A high power Nd:YAG laser beam was used for producing optical breakdown plasma in the air. The dynamics of breakdown plasma were studied using an optical probe beam. A portion of the laser beam was used, as the probe beam and was aligned to propagate (perpendicular to the pump beam) through the breakdown region. The transmission of the probe beam (through the breakdown region) was temporally measured for both single and double pulse irradiations. The results were used to describe the evolution of the induced plasma in both conditions. These results show that the plasma formation time and its absorptivity are strongly dependent on the single or double pulse configurations.

  3. Comparative LIBS Analysis Of Calcified Tissues

    SciTech Connect

    Abdel-Salam, Z. A.; Harith, M. A.

    2008-09-23

    Signal enhancement, limits of detection, and relevance to environmental concentration for element in calcified tissues using LIBS with single and double laser pulses will be presented. These measurements were performed on three calcified tissues representing different matrices, namely enamel of human teeth, shells and eggshells. This method depends on the role of the laser induced shock wave on the ionization rate of the ablated target material atoms. The effect of the laser single and double pulse on the ionic to atomic ratio of calcium and magnesium spectral emission lines, CaII/CaI and MgII/MgI, will be presented and compared with the previous results and its relevance to the target material hardness. The results show that in case of single pulse the intensity ratios in calcium are higher than the double pulse while there is no appreciable difference between both in case of magnesium.

  4. Numerical Simulations of a 2.05 μm Q-switched Ho:YLF Laser for CO2 IPDA Space Remote Sensing

    NASA Astrophysics Data System (ADS)

    Barrientos Pellegrino, Jessica; Edouart, Dimitri; Gibert, Fabien; Cenac, Claire

    2016-06-01

    We report on numerical simulations of the performances of a 2.05 μm double pulse Q-switched Ho:YLF laser for the monitoring of CO2 from space. A Q-switched Holmium laser set-up based on a MOPA configuration is proposed to fulfill the requirements of a IPDA space-borne measurement. Double pulse operation is considered to obtain a 250 μs delay time between the ON and OFF pulse emissions. Numerical simulations results show that up to 40 mJ ON pulse can be extracted from the Ho:YLF laser at a repetition rate of 350 Hz with an optical efficiency of 17 %.

  5. High-performance laser processing using manipulated ultrafast laser pulses

    NASA Astrophysics Data System (ADS)

    Sugioka, Koji; Cheng, Ya; Xu, Zhizhan; Hanada, Yasutaka; Midorikawa, Katsumi

    2012-07-01

    We employ manipulated ultrafast laser pulses to realize microprocessing with high-performance. Efficient microwelding of glass substrates by irradiation by a double-pulse train of ultrafast laser pulses is demonstrated. The bonding strength of two photostructurable glass substrates welded by double-pulse irradiation was evaluated to be 22.9 MPa, which is approximately 22% greater than that of a sample prepared by conventional irradiation by a single pulse train. Additionally, the fabrication of hollow microfluidic channels with a circular cross-sectional shape embedded in fused silica is realized by spatiotemporally focusing the ultrafast laser beam. We show both theoretically and experimentally that the spatiotemporal focusing of ultrafast laser beam allows for the creation of a three-dimensionally symmetric spherical peak intensity distribution at the focal spot.

  6. High-power 2-μm diode-pumped Tm:YAG laser

    NASA Astrophysics Data System (ADS)

    Beach, Raymond J.; Sutton, Steven B.; Honea, Eric C.; Skidmore, Jay A.; Emanuel, Mark A.

    1996-03-01

    Using a scalable diode end-pumping technology developed at Lawrence Livermore National Laboratory we have demonstrated a compact Tm:YAG laser capable of generating greater than 50 W of cw 2 micrometer laser output power. The design and operational characteristics of this laser, which was built originally for use in assessing laser surgical techniques, are discussed. The 2 micrometer radiation produced by the 3F4 - 3H6 transition of Tm3+ has many practical applications because it is strongly absorbed by water and also because it is an 'eye-safe' wavelength. The strong absorption of 2 micrometer radiation by water makes this transition a very attractive candidate for performing laser surgical procedures as most tissue types are predominately composed of liquid water. The fact that 2 micrometer radiation is considered 'eye-safe' makes this transition attractive for laser range finding and remote sensing applications where other laser wavelengths could pose a safety hazard. At sufficiently high doping densities, Tm3+ exhibits a beneficial two-for-one quantum pump efficiency enabling well developed AlGaAs laser diode arrays to be used as efficient excitation sources. Many applications requiring 2 micrometer laser radiation such as remote sensing, laser radar, anti sensor, sensor spoofing, and OPO pumping have driven the development of diode pumped all solid state TM3+ laser systems because of their potential for efficiency, compactness, and ruggedness. Here we focus on Tm3+:YAG and the scalable diode end-pumping technology developed at LLNL which enables higher average power operation of diode pumped Tm3+ laser systems than has previously been possible. To date we have demonstrated cw operation of this laser to power levels of 51 W. The end-pumping technology used is the same as was previously used to demonstrate a 100 mJ Q-switched Nd:YLF laser. (Truncated.)

  7. A compact high current pulsed electron gun with subnanosecond electron pulse widths

    NASA Technical Reports Server (NTRS)

    Khakoo, M. A.; Srivastava, S. K.

    1984-01-01

    A magnetically-collimated, double-pulsed electron gun capable of generating electron pulses with a peak instantaneous current of approximately 70 microamps and a temporal width of 0.35 ns (FWHM) has been developed. Calibration is accomplished by measuring the lifetime of the well known 2(1P)-to-1(1S) transition in helium (58.4nm) at a near-threshold electron-impact energy by use of the delayed-coincidence technique.

  8. Flexible control of femtosecond pulse duration and separation using an emittance-spoiling foil in x-ray free-electron lasers

    SciTech Connect

    Ding, Y.; Behrens, C.; Coffee, R.; Decker, F. -J.; Emma, P.; Field, C.; Helml, W.; Huang, Z.; Krejcik, P.; Krzywinski, J.; Loos, H.; Lutman, A.; Marinelli, A.; Maxwell, T. J.; Turner, J.

    2015-06-22

    We report experimental studies of generating and controlling femtosecond x-ray pulses in free-electron lasers (FELs) using an emittance spoiling foil. By selectivity spoiling the transverse emittance of the electron beam, the output pulse duration or double-pulse separation is adjusted with a variable size single or double slotted foil. Measurements were performed with an X-band transverse deflector located downstream of the FEL undulator, from which both the FEL lasing and emittance spoiling effects are observed directly.

  9. Holographic Cinematography And Its Applications

    NASA Astrophysics Data System (ADS)

    Smigielski, Paul

    1987-09-01

    We describe several applications of cineholography to objects scattering light by reflection: single-exposure cineholograms on 126-mm films at a repetition rate of 25 holograms per second for 3-D movies and for flight simulators applications, double-exposure cineholograms for medical and industrial applications (NDT). Limitations of cineholography are also described. The light source used for cineholograms recording is a frequency-doubled pulse YAG-laser.

  10. Holographic Cinematography And Its Applications

    NASA Astrophysics Data System (ADS)

    Smigielski, P.; Fagot, H.; Albe, F.

    1988-01-01

    Important progresses were achieved for the first time: 1) recording of single-exposure cineholograms of living bodies on 126-mm films, at a repetition rate of 25 holograms per second with the help of a frequency-doubled pulse YAG-laser; 2) recording of double-exposure cineholograms of reflecting moving objects for medical and industrial applications. Limitations of 3-D movies are described.

  11. Detection of Energetic Materials and Explosive Residues With Laser-Induced Breakdown Spectroscopy: 1. Laboratory Measurements

    DTIC Science & Technology

    2007-09-01

    oil] M-43 (propellant) 76% RDX, 4% nitrocellulose, 12% cellulose acetate / butyrate , 8% plasticizer, ə% additives LX-14 (propellant) 95.5% HMX, 4.5... gas and double pulse LIBS, have been investigated with laboratory and field-portable instruments. We present results demonstrating the ability of... separation Δt=2 μs and total energy=320 mJ). (Twenty spectra of the aluminum and RDX residue samples in air and under an argon flow were acquired with

  12. Science and society test IX: Technical means of verification

    SciTech Connect

    Hafemeister, D.

    1986-08-01

    Technical means of monitoring are used to verify compliance to arms control treaties. Numerical estimates are developed in order to quantify some aspects of (1) nuclear testing (signatures, optical double pulse calibration, decoupling in cavities, and high-frequency components in seismic signals), (2) optical reconnaissance (films versus CCDs, air turbulence, adaptive optics, and digital image processing), (3) infrared (resolution and detection sensitivity), and (4) radar (synthetic aperture and missile coefficient).

  13. Holographic flow visualization at NASA Langley

    NASA Technical Reports Server (NTRS)

    Burner, A. W.; Goad, W. K.

    1979-01-01

    Holographic flow visualization systems at two NASA Langley facilities, a hypersonic blow-down tunnel using CF4 gas and an expansion tube with very short test time, are described. A pulsed ruby laser is used at a CF4 tunnel for single pulse holography, double pulse with several minutes between exposures, and dual plate holographic interferometry. Shadowgraph, schlieren, and interferograms are reconstructed from the holograms in a separate reconstruction lab. At the expansion tube the short run time of 200 microseconds requires precise triggering of its double pulsed ruby laser. With double pulse capability of 20 to 1200 microseconds pulse separation, one pulse can occur before and one later after flow is established to obtain fringe free background interferograms (perfect infinite fringe) or both pulses can occur during flow in order to study flow instabilities. Holograms are reconstructed at the expansion tube with an in-place setup which makes use of a high power CW Argon laser and common optics for both recording and reconstructing the holograms. The holographic systems at the CF4 tunnel and expansion tube are operated routinely for flow visualization by tunnel technicians. Typical flow visualization photographs from both facilities are presented.

  14. A multiple work mode YAG laser in derma surgery

    NASA Astrophysics Data System (ADS)

    Sa, Yu; Zhang, Guizhong; Ye, Zhisheng; Yu, Lin

    2006-06-01

    It has been very common that a pulse laser is used in derma surgery based on the theory of "Selective Photothermolysis". This method has also been accepted as the best way to treat the pigments by the medical textbook. A kind of double-pulsed laser which gets the name by two pulse output at one pumping process is developed for derma surgery lately, and this kind of laser has been proved more effective and safe than single-pulse laser. We also develop a multiple work mode YAG laser including two double-pulsed modes at 1064nm and 532nm, two single-pulsed modes at 1064nm and 532nm, and one free-running mode at 1064nm. Considering availability, security and reliability of the laser as a surgery machine, some important subsystems of the laser are optimized carefully, such as Q-switch driver, wavelength-switching system, power supply, and control system etc. At last we get a prototype laser which can run for longer than 30 minutes continuously, and output Max10 pulse per second (pps) with Max800mJ energy at 1064nm double Q-Switch mode, or Max400mJ at 532nm. Using double pulse mode of the laser we do some removal experiments of tattoos and other pigments, and obtain good effect.

  15. Characteristics of excitation discharge of an excimer laser in gas density depletion

    NASA Astrophysics Data System (ADS)

    Imada, Go; Masuda, Wataru; Yatsui, Kiyoshi

    1998-12-01

    The influences of gas density depletion on the highly- repetitive, high-pressure, pulsed glow discharge for excitation of excimer laser have been investigated eliminating the other instabilities, such as shock waves, residual ions, discharge products and electrode heating. The gas density depletion is simulated by utilizing a subsonic flow between the curved electrodes. The comparison has been made on the discharge occurred in the presence of the gas density depletion with the second discharge on the double-pulse experiment. We have found that the big gas density non uniformity, (Delta) (rho) /(rho) 0 approximately 3.6% corresponding to a pulse repetition rate (PRR) of approximately 20 Hz, tends to cause the arc discharge without the shocks, ions, discharge products and electrode heating. On the other hand, the second discharge on the double-pulse experiment becomes arc discharge in much smaller non uniformity ((Delta) (rho) /(rho) 0 approximately 1.2% corresponding to PRR approximately 3 Hz). The arc discharge in the double-pulse experiment might be driven by the residual ions and/or discharge products other than gas density depletion except for PRR greater than 20 Hz.

  16. Infrasound tremor from bubble burst eruptions in the viscous shallow crater lake of White Island, New Zealand, and its implications for interpreting volcanic source processes

    NASA Astrophysics Data System (ADS)

    Jolly, Arthur; Kennedy, Ben; Edwards, Matt; Jousset, Philippe; Scheu, Bettina

    2016-11-01

    White Island volcano, New Zealand, produced two periods (January-February and July 2013) of episodic and persistent eruptions through a viscous shallow mud/sulphur pool. The eruptions included an initial hemispherical bubble burst, which was intermittently followed by an up-channel gas jet, and finally a late stage heaving of a mud/sulphur/water suspension. The late stage heave was systematically directed south-eastward as far as 30-40 m from the vent. The associated infrasound time-series included harmonic tremor on permanent stations WIZ and WSRZ. Detailed inspection showed that the tremor was composed of numerous discrete double pulse events without a strong periodic event repetition. The first pulse had highly similar waveforms event-to-event and a notable distortion of the waveform period between the two infrasound stations located on opposites sides from the directed eruption source. The second pulse occurred about 1.5-2.5 s later and was weakly observed on station WSRZ. Where the video can be rigorously linked to the double pulse infrasound signals we interpret aspects of the distinctive eruptive regimes. For this case, the regime dynamics are driven by the propagation of numerous discrete gas slugs though the shallow viscous muddy crater lake, each generating a distinct bubble burst with subsequent eruption heave and associated double pulse infrasound events. The double pulse events are the source of the persistent harmonic tremor having fundamental and overtone spectral frequencies but are not interpreted as related to cavity resonance or a repetitious comb function. Instead the activity is produced by a single event producing a specific two pulse source time function. The observed distortion in the first pulse wave period at WIZ and WSRZ may be ascribed to a Doppler shift associated with the directivity observed in the initial jet/heave eruption process. We surmise that double pulse source dynamics and directivity effects may be generically extended to

  17. Biomass waste gasification - can be the two stage process suitable for tar reduction and power generation?

    PubMed

    Sulc, Jindřich; Stojdl, Jiří; Richter, Miroslav; Popelka, Jan; Svoboda, Karel; Smetana, Jiří; Vacek, Jiří; Skoblja, Siarhei; Buryan, Petr

    2012-04-01

    A pilot scale gasification unit with novel co-current, updraft arrangement in the first stage and counter-current downdraft in the second stage was developed and exploited for studying effects of two stage gasification in comparison with one stage gasification of biomass (wood pellets) on fuel gas composition and attainable gas purity. Significant producer gas parameters (gas composition, heating value, content of tar compounds, content of inorganic gas impurities) were compared for the two stage and the one stage method of the gasification arrangement with only the upward moving bed (co-current updraft). The main novel features of the gasifier conception include grate-less reactor, upward moving bed of biomass particles (e.g. pellets) by means of a screw elevator with changeable rotational speed and gradual expanding diameter of the cylindrical reactor in the part above the upper end of the screw. The gasifier concept and arrangement are considered convenient for thermal power range 100-350 kW(th). The second stage of the gasifier served mainly for tar compounds destruction/reforming by increased temperature (around 950°C) and for gasification reaction of the fuel gas with char. The second stage used additional combustion of the fuel gas by preheated secondary air for attaining higher temperature and faster gasification of the remaining char from the first stage. The measurements of gas composition and tar compound contents confirmed superiority of the two stage gasification system, drastic decrease of aromatic compounds with two and higher number of benzene rings by 1-2 orders. On the other hand the two stage gasification (with overall ER=0.71) led to substantial reduction of gas heating value (LHV=3.15 MJ/Nm(3)), elevation of gas volume and increase of nitrogen content in fuel gas. The increased temperature (>950°C) at the entrance to the char bed caused also substantial decrease of ammonia content in fuel gas. The char with higher content of ash leaving the second stage presented only few mass% of the inlet biomass stream.

  18. Biomass waste gasification - Can be the two stage process suitable for tar reduction and power generation?

    SciTech Connect

    Sulc, Jindrich; Stojdl, Jiri; Richter, Miroslav; Popelka, Jan; Svoboda, Karel; Smetana, Jiri; Vacek, Jiri; Skoblja, Siarhei; Buryan, Petr

    2012-04-15

    Highlights: Black-Right-Pointing-Pointer Comparison of one stage (co-current) and two stage gasification of wood pellets. Black-Right-Pointing-Pointer Original arrangement with grate-less reactor and upward moving bed of the pellets. Black-Right-Pointing-Pointer Two stage gasification leads to drastic reduction of tar content in gas. Black-Right-Pointing-Pointer One stage gasification produces gas with higher LHV at lower overall ER. Black-Right-Pointing-Pointer Content of ammonia in gas is lower in two stage moving bed gasification. - Abstract: A pilot scale gasification unit with novel co-current, updraft arrangement in the first stage and counter-current downdraft in the second stage was developed and exploited for studying effects of two stage gasification in comparison with one stage gasification of biomass (wood pellets) on fuel gas composition and attainable gas purity. Significant producer gas parameters (gas composition, heating value, content of tar compounds, content of inorganic gas impurities) were compared for the two stage and the one stage method of the gasification arrangement with only the upward moving bed (co-current updraft). The main novel features of the gasifier conception include grate-less reactor, upward moving bed of biomass particles (e.g. pellets) by means of a screw elevator with changeable rotational speed and gradual expanding diameter of the cylindrical reactor in the part above the upper end of the screw. The gasifier concept and arrangement are considered convenient for thermal power range 100-350 kW{sub th}. The second stage of the gasifier served mainly for tar compounds destruction/reforming by increased temperature (around 950 Degree-Sign C) and for gasification reaction of the fuel gas with char. The second stage used additional combustion of the fuel gas by preheated secondary air for attaining higher temperature and faster gasification of the remaining char from the first stage. The measurements of gas composition and tar compound contents confirmed superiority of the two stage gasification system, drastic decrease of aromatic compounds with two and higher number of benzene rings by 1-2 orders. On the other hand the two stage gasification (with overall ER = 0.71) led to substantial reduction of gas heating value (LHV = 3.15 MJ/Nm{sup 3}), elevation of gas volume and increase of nitrogen content in fuel gas. The increased temperature (>950 Degree-Sign C) at the entrance to the char bed caused also substantial decrease of ammonia content in fuel gas. The char with higher content of ash leaving the second stage presented only few mass% of the inlet biomass stream.

  19. On-chip noninterference angular momentum multiplexing of broadband light

    NASA Astrophysics Data System (ADS)

    Ren, Haoran; Li, Xiangping; Zhang, Qiming; Gu, Min

    2016-05-01

    Angular momentum division has emerged as a physically orthogonal multiplexing method in high-capacity optical information technologies. However, the typical bulky elements used for information retrieval from the overall diffracted field, based on the interference method, impose a fundamental limit toward realizing on-chip multiplexing. We demonstrate noninterference angular momentum multiplexing by using a mode-sorting nanoring aperture with a chip-scale footprint as small as 4.2 micrometers by 4.2 micrometers, where nanoring slits exhibit a distinctive outcoupling efficiency on tightly confined plasmonic modes. The nonresonant mode-sorting sensitivity and scalability of our approach enable on-chip parallel multiplexing over a bandwidth of 150 nanometers in the visible wavelength range. The results offer the possibility of ultrahigh-capacity and miniaturized nanophotonic devices harnessing angular momentum division.

  20. Highly Resolved Aerosol Measurements from High Altitude Platforms

    NASA Technical Reports Server (NTRS)

    Wilson, James Charles

    1999-01-01

    The University of Denver agreed to develop and fabricate two instruments for the characterization of submicron aerosol. The instruments were to be light weight for use on remotely-piloted aircraft or balloons. The instruments were to provide accurate size measurements of size distributions in the size range from 0.07 to 2 micrometers in diameter and concentration measurements in the size range approximately 0.01 to 2 micrometers in diameter. The instruments constructed under this cooperative agreement respond quite nearly as expected and meet the objective of being light and compact. One has been used for ground based and low altitude studies and the other will be deployed in high altitude studies this winter.

  1. Develop real-time dosimetry concepts and instrumentation for long term missions

    NASA Technical Reports Server (NTRS)

    Braby, L. A.

    1982-01-01

    The development of a rugged portable instrument to evaluate dose and dose equivalent is described. A tissue-equivalent proportional counter simulating a 2 micrometer spherical tissue volume was operated satisfactorily for over a year. The basic elements of the electronic system were designed and tested. And finally, the most suitable mathematical technique for evaluating dose equivalent with a portable instrument was selected. Design and fabrication of a portable prototype, based on the previously tested circuits, is underway.

  2. Stereological analysis of plasmolysis in logarithmic-phase Bacillus licheniformis.

    PubMed Central

    Schall, B F; Marathe, G V; Ghosh, B K

    1981-01-01

    The plasmolytic response of Bacillus licheniformis 749/C cells to the increasing osmolarity of the surrounding medium was quantitated with stereological techniques. Plasmolysis was defined as the area (in square micrometers) of the inside surface of the bacterial wall not in association with bacterial membrane per unit volume (in cubic micrometers) of bacteria. This plasmolyzed surface area was zero when the cells were suspended in a concentration of sucrose solution lower than 0.5 M, but increased linearly when the sucrose molarity rose above 0.5 M, reaching a plateau value of 3.61 micrometers2/micrometers3 in 2 M sucrose. In contrast, when the bacterial cells were treated with lysozyme plasmolysis increased abruptly from 0.06 micrometers2/micrometers3 in 0.75 M sucrose to 4.09 micrometers2/micrometers3 in 1 M sucrose. When the time of exposure was prolonged, the degree of plasmolysis increased gradually for the duration of the experiment (30 min) after exposure to 1 M sucrose without lysozyme, whereas with lysozyme plasmolysis reached a maximum (4.09 micrograms2/micrometers3) in 2 to 5 min. The examination of ultrastructure showed that the protoplast bodies of lysozyme-treated cells in 1 M sucrose and untreated cells in 2 M sucrose are maximally retracted from the intact wall of the bacteria; hardly any retraction of protoplasts could be seen for untreated cells in 1 M sucrose. The data suggest that the B. licheniformis cells are isoosmotic to 800 to 1,100 mosM solutions, but are able to withstand much greater osmotic pressure with no signs of plasmolysis because the cell wall and the plasma membrane are held in close association, perhaps by a covalent bond. It is likely that lysozyme weakens this bond by degradation of the peptidoglycan layer. Cellular autolysis also weakens this wall-membrane association. Images PMID:7217004

  3. Growing Gallium Arsenide On Silicon

    NASA Technical Reports Server (NTRS)

    Radhakrishnan, Gouri

    1989-01-01

    Epitaxial layers of high quality formed on <111> crystal plane. Present work reports successful growth of 1- and 2-micrometer thick layers of n-type, 7-ohms per cm, 2-inch diameter, Si<111> substrate. Growth conducted in Riber-2300(R) MBE system. Both doped and undoped layers of GaAs grown. Chamber equipped with electron gun and camera for in-situ reflection high-energy-electron diffraction measurements. RHEED patterns of surface monitored continuously during slow growth stage.

  4. Barrier layer for a MCrAlY basecoat superalloy combination

    DOEpatents

    Sabol, Stephen M.; Goedjen, John G.; Vance, Steven J.

    2001-01-01

    A turbine component contains a substrate (22) such as a superalloy, a basecoat (24) of the type MCrAlY, and a continuous barrier layer (28) between the substrate and basecoat, where the barrier layer (28) is made of an alloy of (Re, Ta, Ru, Os)X, where X can be Ni, Co or their mixture, where the barrier layer is at least 2 micrometers thick and substantially prevents materials from both the basecoat and substrate from migrating through it.

  5. What the Voyager infrared investigators hope to learn about the Saturn system

    NASA Technical Reports Server (NTRS)

    Hanel, R. A.

    1978-01-01

    The Voyager infrared investigation uses a Michelson interferometer (IRIS) covering the spectral range from 200 to 3000 cm/1 (3.3 to 50 micrometers) and a bore sighted radiometer covering the range from 5000 to 25000 cm/1 (0.4 to 2 micrometers). The spectral resolution of the interferometer is 4.3 cm/1 and the field of view is 0.25 deg. Scientific results anticipated from the investigation of the Saturnian system are discussed.

  6. Midinfrared frequency comb from self-stable degenerate GaAs optical parametric oscillator.

    PubMed

    Lee, Kevin F; Mohr, C; Jiang, J; Schunemann, Peter G; Vodopyanov, K L; Fermann, M E

    2015-10-05

    We pump a degenerate frequency-divide-by-two optical parametric oscillator (OPO) based on orientation-patterned GaAs with a stable Tm frequency comb at 2 micrometer wavelength and measure the OPO comb offset frequency and linewidth. We show frequency division by two with sub-Hz relative linewidth of the comb teeth. The OPO thermally self-stabilizes and oscillates for nearly an hour without any active control.

  7. A High Energy 2-microns Laser for Multiple Lidar Applications

    NASA Technical Reports Server (NTRS)

    Yu, Jirong; Singh, Upendra N.; Barnes, James C.; Barnes, Norman P.; Petros, Mulugeta

    2000-01-01

    Solid-state 2-microns laser has been receiving considerable interest because of its eye-safe property and efficient diode pump operation, It has potential for multiple lidar applications to detect water vapor. carbon dioxide and winds. In this paper, we describe a 2-microns double pulsed Ho:Tm:YLF laser and end-pumped amplifier system. A comprehensive theoretical model has been developed to aid the design and optimization of the laser performance. In a single Q-switched pulse operation the residual energy stored in the Tm atoms will be wasted. However, in a double pulses operation mode, the residual energy stored in the Tm atoms will repopulate the Ho atoms that were depleted by the extraction of the first Q-switched pulse. Thus. the Tin sensitized Ho:YLF laser provides a unique advantage in applications that require double pulse operation, such as Differential Absorption Lidar (DIAL). A total output energy of 146 mJ per pulse pair under Q-switch operation is achieved with as high as 4.8% optical to optical efficiency. Compared to a single pulse laser, 70% higher laser efficiency is realized. To obtain high energy while maintaining the high beam quality, a master-oscillator-power-amplifier 2-microns system is designed. We developed an end-pumped Ho:Tm:YLF disk amplifier. This amplifier uses two diode arrays as pump source. A non-imaging lens duct is used to couple the radiation from the laser diode arrays to the laser disk. Preliminary result shows that the efficiency of this laser can be as high as 3%, a factor of three increases over side-pump configuration. This high energy, highly efficient and high beam quality laser is a promising candidate for use in an efficient, multiple lidar applications.

  8. Effect of experimental conditions on surface hardness measurements of calcified tissues via LIBS

    NASA Astrophysics Data System (ADS)

    Abdel-Salam, Z. A.; Nanjing, Z.; Anglos, D.; Harith, M. A.

    2009-01-01

    This paper reports on the effects of LIBS experimental conditions on the measurement of the surface hardness of calcified tissues. The technique mainly depends on a previously demonstrated correlation between the intensity ratio of ionic to atomic spectral lines and the hardness of the target material. Three types of calcified tissues have been examined, namely enamel of human teeth, shells, and eggshells. Laser-induced breakdown spectra were obtained under two different experimental conditions. In the first nano and picoseconds, laser pulses were used in a single-pulse arrangement, while in the second, single- and double-pulse regimes with nanosecond laser excitation were utilized. The results show that the ionic to atomic spectral line intensity ratios are higher in the case of picosecond laser pulse for both Ca and Mg spectral lines. This effect has been justified in view of the repulsive force of the laser-induced shock waves which depends clearly on the target surface hardness and on the laser irradiance. The electron densities ratio (pico/nano) is shown to be strongly depending on the laser irradiance too. In the case of calcium, single-pulse ratios are higher than the double-pulse ratios, while there is no appreciable difference between both in the case of magnesium. The results obtained herein suggest that double-pulse nanosecond arrangement and the choice of a minor element such as Mg furnishes the best experimental conditions for estimating the surface hardness via LIBS spectra. To validate this method, it has been applied on two previously measured groups of teeth enamel, the first is of ancient Egyptians, and the second from Nubians and Ugandans. The results support the usefulness of this method for similar real-life applications.

  9. Temporal Young's interference experiment by attosecond double and triple soft-x-ray pulses

    SciTech Connect

    Ishikawa, Kenichi L.

    2006-08-15

    We study a temporal version of Young's interference experiment by attosecond soft-x-ray pulses. The photoelectron energy spectra by attosecond double pulses exhibit an interference pattern, since we have no information on which pulse has generated the electron. We can re-establish the 'which-way' information and control the interference visibility by changing the electron's momentum with phase-stabilized laser pulses, by an amount depending on the time of ionization. Moreover, if we use a triple pulse, we can realize a situation where the electron passes through a single and a double slit simultaneously to the same direction and is observed by the same detector.

  10. Turbulence modeling in shock wave/turbulent boundary layer interactions

    NASA Technical Reports Server (NTRS)

    Smits, A. J.

    1992-01-01

    The research performed was an experimental program to help develop turbulence models for shock wave boundary layer interactions. The measurements were taken in a Mach 3, 16 deg compression corner interaction, at a unit Reynolds number of 63 x 10(exp 6)/m. The data consisted of heat transfer data taken upstream and downstream of the interaction, hot wire measurements of the instantaneous temperature and velocity fluctuations to verify the Strong Reynolds Analogy, and single- and double-pulsed Rayleigh scattering images to study the development of the instantaneous shock/turbulence interaction.

  11. Doublet-doublet fluorescence of benzyl, p-methylbenzyl and p-chlorobenzyl radicals in solution

    NASA Astrophysics Data System (ADS)

    Tokumura, Kunihiro; Udagawa, Masahiro; Ozaki, Tomomi; Itoh, Michiya

    1987-11-01

    The doublet-doublet fluorescence spectra of benzyl, p-methylbenzyl and p-chlorobenzyl radicals were detected in the 450-650 nm region upon the double-pulse (248 nm→308 nm) excitation of corresponding benzyl chlorides in hexane at room temperature. The respective fluorescence lifetimes were determined to be ≈ 1 ns or less (benzyl), 14 ns ( p-methylbenzyl) and 81 ns ( p-chlorobenzyl). Extensively temperature-dependent non-radiative relaxation was confirmed for these benzyl radicals with close-lying lowest doublet excited states.

  12. Laser-Induced Plasma Chemistry of the Explosive RDX with Various Metallic Nanoparticles

    DTIC Science & Technology

    2013-04-01

    the detector. The gate delay (tdelay) was varied from 0 to 10 μs while the integration time (tint 1 μs) was held constant at the minimum value for...Continuum double pulse laser with the echelle/EMCCD spectro - meter. As before, the RDX was suspended in acetoni- trile and deposited on the pure Al substrate...slowly decays over time, while the C emission is relatively constant for the first 10 μs of the plasma lifetime. The energy required to promote C into the

  13. Time-sequenced and spectrally filtered Rayleigh imaging of shock wave and boundary layer structure for inlet characterization

    NASA Technical Reports Server (NTRS)

    Forkey, Joseph; Cogne, Sandrine; Smits, Alexander; Bogdonoff, Seymour; Lempert, Walter R.; Miles, Richard B.

    1993-01-01

    Multiple pulsed Rayleigh imaging and filtered Rayleigh scattering are used to generate images of a complex boundary layer structure, shock wave/boundary layer interactions, and crossing shock waves. Time-sequenced Rayleigh images taken with a visible, double-pulsed laser system show the evolution of boundary layer structure of the internal flow in a generic cross-shock inlet. The images taken in the inlet give insight into 3D effects caused by the inlet geometry and may be used for modeling the complex flows.

  14. Efficiency of stone fragmentation by long pulses of a Q-switched Nd:YAG laser

    NASA Astrophysics Data System (ADS)

    Helfmann, Juergen; Mikhailov, B. A.; Konov, Vitali I.; Mueller, Gerhard J.; Nikolaev, D. A.; Pak, S. K.; Shcherbakov, Ivan A.; Silenok, Alexander S.

    1992-06-01

    The effect of long pulsed Nd:YAG laser (pulse duration 300 ns) with the fundamental and second harmonic wavelength on the fragmentation of different urological and gall stones has been investigated. With 200 and 400 micrometers fibers in a contact application, all types of stones could be fragmented with energies less than 120 mJ (400 micrometers fiber) or 45 mJ (200 micrometers fiber). By use of a double pulse-simultaneous application of second harmonic and fundamental radiation the efficiency of fragmentation could be increased and the energy threshold decreased.

  15. Yoctosecond metrology through Hanbury Brown-Twiss correlations from a quark-gluon plasma.

    PubMed

    Ipp, Andreas; Somkuti, Peter

    2012-11-09

    Expansion dynamics at the yoctosecond time scale affect the evolution of the quark gluon plasma (QGP) created in heavy ion collisions. We show how these dynamics are accessible through Hanbury Brown-Twiss (HBT) intensity interferometry of direct photons emitted from the interior of the QGP. A detector placed close to the beam axis is particularly sensitive to early polar momentum anisotropies of the QGP. Observing a modification of the HBT signal at the proposed FoCal detector of the LHC ALICE experiment would allow us to measure the isotropization time of the plasma and could provide first experimental evidence for photon double pulses at the yoctosecond time scale.

  16. Operation of a Ti:Sapphire laser for the SLAC polarized electron source

    SciTech Connect

    Frisch, J.; Alley, R.; Browne, M.; Woods, M.

    1993-04-01

    A new laser system has been developed as the light source for the SLAC polarized electron source for the 1993 SLD physics run. A Q-switched and cavity-dumped Ti:Sapphire laser, pumped by a doubled YAG laser is used. This laser delivers typically 5O{mu}J to the photocathode with the required 2 nanosecond, double pulse, 12OHz time structure. The laser operates at wavelengths between 760nm and 870nm. The laser was installed on the SLAC linac in January 1993, and is currently in use.

  17. Tomographic reconstruction of transient acoustic fields recorded by pulsed TV holography.

    PubMed

    Gren, P; Schedin, S; Li, X

    1998-02-10

    Pulsed TV holography combined with computerized tomography (CT) are used to evaluate the three-dimensional distribution of transient acoustic fields in air. Experiments are performed with an electrical discharge between two electrodes as the sound source. Holograms from several directions of the acoustic field are recorded directly onto a CCD detector by use of a double-pulsed ruby laser as the light source. Phase maps, representing projections of the acoustic field, are evaluated quantitatively from the recorded holograms. The projections are used for the CT reconstruction to evaluate the pressure-field distribution in any cross section of the measured volume of air.

  18. Threshold for Trapping Positrons in the Wake Driven by a Ultra-relativistic Electron Bunch

    SciTech Connect

    Wang, X.; Muggli, P.; Katsouleas, T.; Ischebeck, R.; Hogan, M. J.; Joshi, C.; Mori, W. B.

    2009-01-22

    We have recently proposed a new concept for generating, injecting and accelerating positrons in a plasma using a double-pulse electron bunch. Monte Carlo simulations show that the number of the positrons produced in a foil target has an exponentially decay energy spectrum. The energy threshold for the trapping of these positrons in a ultra-relativistic electron wake is investigated numerically. For a typical 28.5 GeV electron drive bunch, the trapping threshold for the positrons is a few MeV, and therefore a majority of positrons generated in the foil target are focused and accelerated by the plasma wake.

  19. The X-ray correlation spectroscopy instrument at the Linac Coherent Light Source

    DOE PAGES

    Alonso-Mori, Roberto; Caronna, Chiara; Chollet, Matthieu; ...

    2015-03-03

    The X-ray Correlation Spectroscopy instrument is dedicated to the study of dynamics in condensed matter systems using the unique coherence properties of free-electron lasers. It covers a photon energy range of 4–25 keV. The intrinsic temporal characteristics of the Linac Coherent Light Source, in particular the 120 Hz repetition rate, allow for the investigation of slow dynamics (milliseconds) by means of X-ray photon correlation spectroscopy. Double-pulse schemes could probe dynamics on the picosecond timescale. In addition, a description of the instrument capabilities and recent achievements is presented.

  20. Unbalanced Michelson's interferometer as a fiber optic distributed sensor of external signals

    NASA Astrophysics Data System (ADS)

    Chojnacki, M.; Szustakowski, Mieczyslaw; Zyczkowski, Marek

    2001-08-01

    The subject of this work is a novel fiber optic distributed sensor system. The system uses a technique called multiplexed reflectometric interferometry to measure dynamic strain in a network of single mode optical fiber sensors. The sensor is constructed on unbalanced fiber optic Michelson's interferometer is activated by series of double pulse. The time interval between those pulses depends on the length of the section of sensor. Acousto-optical modulator acts as an optical frequency shifter. A change in a frequency of electrical pulses exciting the modulator result in a frequency shift in each generated wave packet.

  1. PT-symmetric mode-locking.

    PubMed

    Longhi, S

    2016-10-01

    Parity-time (PT) symmetry is one of the most important accomplishments in optics over the past decade. Here the concept of PT mode-locking (ML) of a laser is introduced, in which active phase-locking of cavity axial modes is realized by asymmetric mode coupling in a complex time crystal. PT ML shows a transition from single- to double-pulse emission as the PT symmetry breaking point is crossed. The transition can show a turbulent behavior, depending on a dimensionless modulation parameter that plays the same role as the Reynolds number in hydrodynamic flows.

  2. Anisotropic phantom to calibrate high-q diffusion MRI methods

    NASA Astrophysics Data System (ADS)

    Komlosh, M. E.; Benjamini, D.; Barnett, A. S.; Schram, V.; Horkay, F.; Avram, A. V.; Basser, P. J.

    2017-02-01

    A silicon oil-filled glass capillary array is proposed as an anisotropic diffusion MRI phantom. Together with a computational/theoretical pipeline these provide a gold standard for calibrating and validating high-q diffusion MRI experiments. The phantom was used to test high angular resolution diffusion imaging (HARDI) and double pulsed-field gradient (d-PFG) MRI acquisition schemes. MRI-based predictions of microcapillary diameter using both acquisition schemes were compared with results from optical microscopy. This phantom design can be used for quality control and quality assurance purposes and for testing and validating proposed microstructure imaging experiments and the processing pipelines used to analyze them.

  3. A phase-sensitive optical time-domain reflectometer with dual-pulse phase modulated probe signal

    NASA Astrophysics Data System (ADS)

    Alekseev, A. E.; Vdovenko, V. S.; Gorshkov, B. G.; Potapov, V. T.; Simikin, D. E.

    2014-11-01

    A novel configuration of a phase-sensitive optical time-domain reflectometer (OTDR) utilizing dual-pulse phase modulations of the probe signal is presented and experimentally demonstrated. The proposed modulation method enables one to perform the demodulation and reconstruction of an external perturbation signal which impacts the fiber using the phase diversity technique. The proposed phase-sensitive OTDR has some advantages in comparison with conventional solutions, which are discussed. The feasibility of a double pulse OTDR with phase modulation is demonstrated and theoretically proved.

  4. Femtosecond compressed-nitrogen Raman laser

    NASA Astrophysics Data System (ADS)

    Konyashchenko, A. V.; Kostryukov, P. V.; Losev, L. L.; Pazyuk, V. S.

    2017-01-01

    We have estimated the minimum laser pulse duration at which stimulated Raman scattering in gases is possible. Femtosecond Ti : sapphire laser pulses have been converted to the first Stokes in compressed nitrogen using double-pulse pumping of a gas-filled capillary tube by orthogonally polarised chirped pulses. We have obtained 980-nm Stokes pulses of 51 fs duration. The energy conversion efficiency was 12% at a pulse repetition rate of 1 kHz and average laser output power of 2 W.

  5. Gaseous laser targets and optical diagnostics for studying compressible hydrodynamic instabilities

    SciTech Connect

    Edwards, J M; Robey, H; Mackinnon, A

    2001-06-29

    Explore the combination of optical diagnostics and gaseous targets to obtain important information about compressible turbulent flows that cannot be derived from traditional laser experiments for the purposes of V and V of hydrodynamics models and understanding scaling. First year objectives: Develop and characterize blast wave-gas jet test bed; Perform single pulse shadowgraphy of blast wave interaction with turbulent gas jet as a function of blast wave Mach number; Explore double pulse shadowgraphy and image correlation for extracting velocity spectra in the shock-turbulent flow interaction; and Explore the use/adaptation of advanced diagnostics.

  6. 1-kHz-repetition-rate femtosecond Raman laser

    NASA Astrophysics Data System (ADS)

    Didenko, N. V.; Konyashchenko, A. V.; Kostryukov, P. V.; Losev, L. L.; Pazyuk, V. S.; Tenyakov, S. Yu

    2016-07-01

    A femtosecond Raman laser utilising compressed hydrogen is experimentally investigated under pumping by radiation from a 1-kHz-repetition-rate Ti : sapphire laser. In the regime of double-pulse pumping, the conditions are determined, which correspond to the minimal energy dispersion of Stokes pulses. The optical scheme is realised, which is capable of ensuring the long-term stability of the average power of the first Stokes component with a variation of less than 2%. The Stokes pulses are produced with a pulse duration of 60 fs and energy of 0.26 mJ at a conversion efficiency of 14%.

  7. Study on neutron emission from 2.2 kJ plasma focus device

    SciTech Connect

    Talukdar, N.; Neog, N. K.; Borthakur, T. K.

    2014-06-15

    The neutron emission from a low energy (2.2 kJ) plasma focus device operated in deuterium medium has been investigated by employing photo-multiplier tube (PMT) and bubble dosimeter. The neutron emission is found to be pressure dependent and anisotropic in nature. In most cases of plasma focus shots, the PMT signal shows double pulses of neutron emission with different intensities and widths. An interesting relation between intensity of hard X-ray and neutron emission is also observed.

  8. One-Joule-per-Pulse Q-Switched 2-micron Solid State Laser

    NASA Technical Reports Server (NTRS)

    Yu, Jirong; Trieu, Bo C.; Modlin, Ed A.; Singh, Upendra N.; Kavaya, Michael J.; Chen, Songsheng; Bai, Yingxin; Petzar, Pual J.; Petros, Mulugeta

    2005-01-01

    Q-switched output of 1.1 J per pulse at 2-micron wavelength has been achieved in a diode pumped Ho:Tm:LuLF laser using a side-pumped rod configuration in a Master-Oscillator-Power-Amplifier (MOPA) architecture. This is the first time that a 2-micron laser has broken the Joule per pulse barrier for Q-switched operation. The total system efficiency reaches 5% and 6.2% for single and double pulse operation, respectively. The system produces excellent 1.4 times of transform limited beam quality.

  9. The X-ray correlation spectroscopy instrument at the Linac Coherent Light Source

    SciTech Connect

    Alonso-Mori, Roberto; Caronna, Chiara; Chollet, Matthieu; Curtis, Robin; Damiani, Daniel S.; Defever, Jim; Feng, Yiping; Flath, Daniel L.; Glownia, James M.; Lee, Sooheyong; Lemke, Henrik T.; Nelson, Silke; Bong, Eric; Sikorski, Marcin; Song, Sanghoon; Srinivasan, Venkat; Stefanescu, Daniel; Zhu, Diling; Robert, Aymeric

    2015-03-03

    The X-ray Correlation Spectroscopy instrument is dedicated to the study of dynamics in condensed matter systems using the unique coherence properties of free-electron lasers. It covers a photon energy range of 4–25 keV. The intrinsic temporal characteristics of the Linac Coherent Light Source, in particular the 120 Hz repetition rate, allow for the investigation of slow dynamics (milliseconds) by means of X-ray photon correlation spectroscopy. Double-pulse schemes could probe dynamics on the picosecond timescale. In addition, a description of the instrument capabilities and recent achievements is presented.

  10. Holographic Flow Visualization at NASA Langley

    NASA Technical Reports Server (NTRS)

    Burner, A. W.; Goad, W. K.

    2005-01-01

    Holographic flow visualization systems at two NASA Langley facilities, a hypersonic blow-down tunnel using CF4 gas and an expansion tube with very short test time, are described. A pulsed ruby laser is used at a CF4 tunnel for single pulse holography, double pulse with several minutes between exposures, and dual plate holographic interferometry. Shadow-graph, schlieren, and interferograms are reconstructed from the holograms in a separate reconstruction lab. At the expansion tube the short run time of 200 microseconds requires precise triggering of its double pulsed ruby laser. With pulse separation, one pulse can occur before and one after flow is established to obtain fringe free background interferograms (perfect infinite fringe) or both pulses can occur during flow in order to study flow instabilities. Holograms are reconstructed at the expansion tube with an in-place setup which makes use of a high power CW Argon laser and common optics for both recording and reconstructing the holograms. The holographic systems at the CF4 tunnel and expansion tube are operated routinely for flow visualization by tunnel technicians. Typical flow visualization photographs from both facilities are presented.

  11. Optimizing a Laser Process for Making Carbon Nanotubes

    NASA Technical Reports Server (NTRS)

    Arepalli, Sivaram; Nikolaev, Pavel; Holmes, William

    2010-01-01

    A systematic experimental study has been performed to determine the effects of each of the operating conditions in a double-pulse laser ablation process that is used to produce single-wall carbon nanotubes (SWCNTs). The comprehensive data compiled in this study have been analyzed to recommend conditions for optimizing the process and scaling up the process for mass production. The double-pulse laser ablation process for making SWCNTs was developed by Rice University researchers. Of all currently known nanotube-synthesizing processes (arc and chemical vapor deposition), this process yields the greatest proportion of SWCNTs in the product material. The aforementioned process conditions are important for optimizing the production of SWCNTs and scaling up production. Reports of previous research (mostly at Rice University) toward optimization of process conditions mention effects of oven temperature and briefly mention effects of flow conditions, but no systematic, comprehensive study of the effects of process conditions was done prior to the study described here. This was a parametric study, in which several production runs were carried out, changing one operating condition for each run. The study involved variation of a total of nine parameters: the sequence of the laser pulses, pulse-separation time, laser pulse energy density, buffer gas (helium or nitrogen instead of argon), oven temperature, pressure, flow speed, inner diameter of the flow tube, and flow-tube material.

  12. The LLNL Flash X-Ray Induction Linear Accelerator (FXR)

    SciTech Connect

    Multhauf, L G

    2002-09-19

    The FXR is an induction linear accelerator used for high-speed radiography at the Lawrence Livermore National Laboratory's Experimental Test Site. It was designed specifically for the radiography of very thick explosive objects. Since its completion in 1982, it has been very actively used for a large variety of explosives tests, and has been periodically upgraded to achieve higher performance. Upgrades have addressed machine reliability, radiographic sensitivity and resolution, two-frame imaging by double pulsing improvements that are described in detail in the paper. At the same time, the facility in which it was installed has also been extensively upgraded, first by adding space for optical and interferometric diagnostics, and more recently by adding a containment chamber to prevent the environmental dispersal of hazardous and radioactive materials. The containment addition also further expands space for new non-radiographic diagnostics. The new Contained Firing Facility is still in the process of activation. At the same time, FXR is continuing to undergo modifications aimed primarily at further increasing radiographic resolution and sensitivity, and at improving double-pulsed performance.

  13. Optimization of liquid jet system for laser-induced breakdown spectroscopy analysis

    NASA Astrophysics Data System (ADS)

    Skočovská, Katarína; Novotný, Jan; Prochazka, David; Pořízka, Pavel; Novotný, Karel; Kaiser, Jozef

    2016-04-01

    A complex optimization of geometrical and temporal parameters of a jet system (developed in Laser-induced breakdown spectroscopy (LIBS) laboratory of Brno University of Technology) for direct elemental analysis of samples in a liquid state of matter using LIBS was carried out. First, the peristaltic pump was synchronized with the flashlamp of the ablation laser, which reduced variation of the ablated sample amount. Also, the fluctuation of the laser ray angle incident on the jet surface was diminished. Such synchronization reduced signal standard deviations and thus increased repeatability of the measurements. Then, laser energy and distance of the focusing lens from the sample were optimized. The gate delay time and the gate width were optimized for single pulse (SP) experiments; the gate delay time and the inter-pulse delay were optimized for the use of double pulse (DP) variant. Results were assessed according to the highest signal to noise ratios and the lowest relative standard deviations of the signal. The sensitivity of the single pulse and the double pulse LIBS for the detection of heavy metals traces, copper (Cu i at 324.754 nm) and lead (Pb i at 405.781 nm), in aqueous solution of copper (ii) sulfate and lead (ii) acetate, was estimated in terms of limits of detection (LODs). As a result, sensitivity improvement of DP LIBS system was observed, the LOD of Cu obtained with DP was calculated 40% lower than LOD gained from SP technique.

  14. Sympathetic activation by the cold pressor test does not increase the muscle force generation capacity.

    PubMed

    Roatta, Silvestro; Farina, Dario

    2011-06-01

    A positive inotropic action by the sympathetic nervous system on skeletal muscles has been observed and investigated in animal and in vitro studies. This action provided a theoretical basis for the putative ergogenic action of catecholamines and adrenergic agonists, although there is no clear evidence of this effect in humans. The aim of this study was to investigate the occurrence of inotropic effects associated to physiological sympathetic activation in healthy subjects. The muscle force capacity was investigated in the tibialis anterior (n = 9 subjects) and in the soleus (n = 9) muscles electrically stimulated with single pulses and double pulses with variable interspike interval (4-1,000 ms) and short pulse trains (frequency: 5-14 Hz) before, during, and after sympathetic activation by the cold pressor test (CPT). CPT significantly decreased by 10.4 ± 7.2 and 10.6 ± 4.4% the force produced by single and double pulse stimulation, respectively, and produced smaller decreases in the force obtained by train stimulation in the tibialis anterior, while no significant changes were observed in either type of contraction in the soleus muscle. CPT failed to induce any increase in the force capacity of the investigated muscles. The prevalent decrease in force evidenced in this study supports the concept that the weakening sympathetic action on type I fiber, already shown to occur in humans, prevails over the putative potentiating action.

  15. KC-135 aero-optical turbulent boundary layer/shear layer experiment revisited

    NASA Astrophysics Data System (ADS)

    Craig, J.; Allen, C.

    1987-05-01

    The aero-optical effects associated with propagating a laser beam through both an aircraft turbulent boundary layer and artificially generated shear layers are examined. The data present comparisons from observed optical performance with those inferred from aerodynamic measurements of unsteady density and correlation lengths within the same random flow fields. Using optical instrumentation with tens of microsecond temporal resolution through a finite aperture, optical performance degradation was determined and contrasted with the infinite aperture time averaged aerodynamic measurement. In addition, the optical data were artificially clipped to compare to theoretical scaling calculations. Optical instrumentation consisted of a custom Q switched Nd:Yag double pulsed laser, and a holographic camera which recorded the random flow field in a double pass, double pulse mode. Aerodynamic parameters were measured using hot film anemometer probes and a five hole pressure probe. Each technique is described with its associated theoretical basis for comparison. The effects of finite aperture and spatial and temporal frequencies of the random flow are considered.

  16. KC-135 aero-optical turbulent boundary layer/shear layer experiment revisited

    NASA Technical Reports Server (NTRS)

    Craig, J.; Allen, C.

    1987-01-01

    The aero-optical effects associated with propagating a laser beam through both an aircraft turbulent boundary layer and artificially generated shear layers are examined. The data present comparisons from observed optical performance with those inferred from aerodynamic measurements of unsteady density and correlation lengths within the same random flow fields. Using optical instrumentation with tens of microsecond temporal resolution through a finite aperture, optical performance degradation was determined and contrasted with the infinite aperture time averaged aerodynamic measurement. In addition, the optical data were artificially clipped to compare to theoretical scaling calculations. Optical instrumentation consisted of a custom Q switched Nd:Yag double pulsed laser, and a holographic camera which recorded the random flow field in a double pass, double pulse mode. Aerodynamic parameters were measured using hot film anemometer probes and a five hole pressure probe. Each technique is described with its associated theoretical basis for comparison. The effects of finite aperture and spatial and temporal frequencies of the random flow are considered.

  17. Growth of arc in high-pressure, pulsed glow discharge by gas density depletion

    NASA Astrophysics Data System (ADS)

    Imada, Go; Yatsui, Kiyoshi; Masuda, Wataru

    2000-10-01

    Effects of gas density depletion on arc formation of high-pressure, pulsed glow discharge have been investigated by eliminating the other factors which may affect the discharge stability, such as shock waves, residual ions, electrode heating, and discharge products. The gas density depletion has been simulated by utilizing a subsonic gas flow between the curved electrodes combined with a convergent nozzle and a divergent diffuser. A comparison has been made on the discharge in the aerodynamically created gas density depletion with the second discharge in the double-pulse discharge within a stable gas. We have found that the large gas density depletion, Δρ/ρ0˜-3.6% corresponding to a pulse repetition rate (PRR) of ˜50 Hz, tends to cause an arc-like filament or an arc without the shocks, ions, electrode heating, and products. However, the second discharge in the double-pulse discharge becomes an arc in much smaller gas density depletion (Δρ/ρ0˜-1.2% corresponding to PRR ˜3 Hz). Therefore, the collapse of high-pressure, pulsed glow discharge is most likely caused by some factor other than the gas density depletion.

  18. Time-bin entangled photon pairs from spontaneous parametric down-conversion pumped by a cw multi-mode diode laser.

    PubMed

    Kwon, Osung; Park, Kwang-Kyoon; Ra, Young-Sik; Kim, Yong-Su; Kim, Yoon-Ho

    2013-10-21

    Generation of time-bin entangled photon pairs requires the use of the Franson interferometer which consists of two spatially separated unbalanced Mach-Zehnder interferometers through which the signal and idler photons from spontaneous parametric down-conversion (SPDC) are made to transmit individually. There have been two SPDC pumping regimes where the scheme works: the narrowband regime and the double-pulse regime. In the narrowband regime, the SPDC process is pumped by a narrowband cw laser with the coherence length much longer than the path length difference of the Franson interferometer. In the double-pulse regime, the longitudinal separation between the pulse pair is made equal to the path length difference of the Franson interferometer. In this paper, we propose another regime by which the generation of time-bin entanglement is possible and demonstrate the scheme experimentally. In our scheme, differently from the previous approaches, the SPDC process is pumped by a cw multi-mode (i.e., short coherence length) laser and makes use of the coherence revival property of such a laser. The high-visibility two-photon Franson interference demonstrates clearly that high-quality time-bin entanglement source can be developed using inexpensive cw multi-mode diode lasers for various quantum communication applications.

  19. Optimization of liquid jet system for laser-induced breakdown spectroscopy analysis.

    PubMed

    Skočovská, Katarína; Novotný, Jan; Prochazka, David; Pořízka, Pavel; Novotný, Karel; Kaiser, Jozef

    2016-04-01

    A complex optimization of geometrical and temporal parameters of a jet system (developed in Laser-induced breakdown spectroscopy (LIBS) laboratory of Brno University of Technology) for direct elemental analysis of samples in a liquid state of matter using LIBS was carried out. First, the peristaltic pump was synchronized with the flashlamp of the ablation laser, which reduced variation of the ablated sample amount. Also, the fluctuation of the laser ray angle incident on the jet surface was diminished. Such synchronization reduced signal standard deviations and thus increased repeatability of the measurements. Then, laser energy and distance of the focusing lens from the sample were optimized. The gate delay time and the gate width were optimized for single pulse (SP) experiments; the gate delay time and the inter-pulse delay were optimized for the use of double pulse (DP) variant. Results were assessed according to the highest signal to noise ratios and the lowest relative standard deviations of the signal. The sensitivity of the single pulse and the double pulse LIBS for the detection of heavy metals traces, copper (Cu i at 324.754 nm) and lead (Pb i at 405.781 nm), in aqueous solution of copper (ii) sulfate and lead (ii) acetate, was estimated in terms of limits of detection (LODs). As a result, sensitivity improvement of DP LIBS system was observed, the LOD of Cu obtained with DP was calculated 40% lower than LOD gained from SP technique.

  20. Mid-IR enhanced laser ablation molecular isotopic spectrometry

    NASA Astrophysics Data System (ADS)

    Brown, Staci; Ford, Alan; Akpovo, Codjo A.; Johnson, Lewis

    2016-08-01

    A double-pulsed laser-induced breakdown spectroscopy (DP-LIBS) technique utilizing wavelengths in the mid-infrared (MIR) for the second pulse, referred to as double-pulse LAMIS (DP-LAMIS), was examined for its effect on detection limits compared to single-pulse laser ablation molecular isotopic spectrometry (LAMIS). A MIR carbon dioxide (CO2) laser pulse at 10.6 μm was employed to enhance spectral emissions from nanosecond-laser-induced plasma via mid-IR reheating and in turn, improve the determination of the relative abundance of isotopes in a sample. This technique was demonstrated on a collection of 10BO and 11BO molecular spectra created from enriched boric acid (H3BO3) isotopologues in varying concentrations. Effects on the overall ability of both LAMIS and DP-LAMIS to detect the relative abundance of boron isotopes in a starting sample were considered. Least-squares fitting to theoretical models was used to deduce plasma parameters and understand reproducibility of results. Furthermore, some optimization for conditions of the enhanced emission was achieved, along with a comparison of the overall emission intensity, plasma density, and plasma temperature generated by the two techniques.

  1. Development of a 2-micron Pulsed Direct Detection IPDA Lidar for CO2 Measurement

    NASA Astrophysics Data System (ADS)

    Yu, J.; Petros, M.; Singh, U. N.

    2013-12-01

    NASA Langley is developing a 2-micron pulsed Integrated Path Differential Absorption (IPDA) lidar for atmospheric CO2 measurements. The high pulse energy, direct detection lidar operating at CO2 2-micron absorption band provides an alternate approach to measure CO2 concentrations with significant advantages. The objective of this development is to integrate an existing high energy double-pulsed 2-micron laser transmitter with a direct detection receiver and telescope to enable a first proof of principle demonstration of airborne direct detection CO2 measurements at 2-micron wavelength. It is expected to provide high-precision measurement capability by unambiguously eliminating contamination from aerosols and clouds that can bias the IPDA measurement. The system is scheduled to fly on NASA UC12 or B200 research aircrafts before the end of 2013. This paper will describe the design of the airborne 2-micron pulsed IPDA lidar system; the lidar operation parameters; the wavelength pair selection; laser transmitter energy, pulse rate, beam divergence, double pulse generation and accurate frequency control; detector characterization; telescope design; lidar structure design; and lidar signal to noise ratio estimation.

  2. Angle of Observation Influence on Emission Signal from Spatially Confined Laser-Induced Plasmas.

    PubMed

    Weiss, Jiri; Cabalín, Luisa Maria; Laserna, J Javier

    2017-01-01

    The present work focuses on the influence of the angle of observation on the emission signal from copper plasmas. Plasma plumes have been generated inside a home-made chamber consisting of two parallel glass windows spaced by 2.5 mm. This chamber allows observing plasma plumes from different collection angles throughout their perimeter, spanning from 20° to 80° with respect to the surface of the Cu target. In order to minimize the observed volume of the plasma, measurements were made from the closest distance possible through a metallic hollow tube. Single-pulse and collinear double-pulse excitation schemes with a Nd:YAG laser (1064 nm, 5 ns) have been investigated. The results have shown that the selection of the best angle to collect light from the plasma is related to the excitation mode. On the other hand, the shot-to-shot signal variability has been found to depend on the shape of plasma plumes. In single-pulse excitation, a good correlation between the observed laser-induced breakdown spectroscopy (LIBS) emission (from spatially confined plumes) and their integrated signal of plasma image has been ascertained. However, this fact was less evident in double-pulse LIBS, which could be due to a different mechanism involved in the ablation process.

  3. Ejecta Particle-Size Measurements in Vacuum and Helium Gas using Ultraviolet In-Line Fraunhofer Holography

    SciTech Connect

    Sorenson, Danny S.; Pazuchanics, Peter; Johnson, Randall P.; Malone, R. M.; Kaufman, M. I.; Tibbitts, A.; Tunnell, T.; Marks, D.; Capelle, G. A.; Grover, M.; Marshall, B.; Stevens, G. D.; Turley, W. D.; LaLone, B.

    2014-06-25

    An Ultraviolet (UV) in-line Fraunhofer holography diagnostic has been developed for making high-resolution spatial measurements of ejecta particles traveling at many mm/μsec. This report will discuss the development of the diagnostic including the high-powered laser system and high-resolution optical relay system. In addition, the system required to reconstruct the images from the hologram and the corresponding analysis of those images to extract particles will also be described. Finally, results from six high-explosive (HE), shock-driven Sn ejecta experiments will be presented. Particle size distributions will be shown that cover most of the ejecta velocities for experiments conducted in a vacuum, and helium gas environments. In addition, a modification has been made to the laser system that produces two laser pulses separated by 6.8 ns. This double-pulsed capability allows a superposition of two holograms to be acquired at two different times, thus allowing ejecta velocities to be measured directly. Results from this double pulsed experiment will be described.

  4. Ejecta Particle-Size Measurements in Vacuum and Helium Gas using Ultraviolet In-Line Fraunhofer Holography

    SciTech Connect

    Sorenson, D. S.; Pazuchanics, P.; Johnson, R.; Malone, R. M.; Kaufman, M. I.; Tibbitts, A.; Tunnell, T.; Marks, D.; Capelle, G. A.; Grover, M.; Marshall, B.; Stevens, G. D.; Turley, W. D.; LaLone, B.

    2014-06-01

    An ultraviolet (UV) in-line Fraunhofer holography diagnostic has been developed for making high-resolution spatial measurements of ejecta particles traveling at many mm/μsec. This report will discuss the development of the diagnostic, including the high-powered laser system and high-resolution optical relay system. In addition, we will also describe the system required to reconstruct the images from the hologram and the corresponding analysis of those images to extract particles. Finally, we will present results from six high-explosive (HE), shock-driven Sn-ejecta experiments. Particle-size distributions will be shown that cover most of the ejecta velocities for experiments conducted in a vacuum, and helium gas environments. In addition, a modification has been made to the laser system that produces two laser pulses separated by 6.8 ns. This double-pulsed capability allows a superposition of two holograms to be acquired at two different times, thus allowing ejecta velocities to be measured directly. Results from this double-pulsed experiment will be described.

  5. Sodium channel inactivation in the crayfish giant axon. Must channels open before inactivating

    SciTech Connect

    Bean, B.P.

    1981-09-01

    Experiments on sodium channel inactivation kinetics were performed on voltage-clamped crayfish giant axons. The primary goals was to investigate whether channels must open before activating. Voltage-clamp artifacts were minimized by the use of low-sodium solutions and full series resistance compensation, and the spatial uniformity of the currents was checked with a closely spaced pair of electrodes used to measure local current densities. For membrane potentials between -40 and +40 mV, sodium currents decay to zero with a single exponential time-course. The time constant for decay is a steep function of membrane potential. The time-course of inactivation measured with the double-pulse method is very similar to the decay of current at the same potential. Steady-state inactivation curves measured with different test pulses are identical. The time-course of doubling pulse inactivation shows a lag that roughly correlates with the opening of sodium channels, but it is not strictly necessary for channels to open before inactivating. Measurements of the potential dependence of the integral of sodium conductance are also inconsistent with the simplest cases of models in which channels must open before activating.

  6. Star formation in the merging Galaxy NGC3256

    NASA Technical Reports Server (NTRS)

    Graham, James R.; Wright, G. S.; Joseph, R. D.; Frogel, J. A.; Phillips, M. M.; Meikle, W. P. S.

    1987-01-01

    The central 5 kpc of the ultra-luminous merging galaxy NGC 3256 was mapped at J, H, K, L, and 10 micrometer, and a 2 micrometer spectra of the nuclear region was obtained. This data was used to identify and characterize the super starburst which has apparently been triggered and fuelled by the merger of two gas rich galaxies. It is also shown that the old stellar population has relaxed into a single spheroidal system, and that a supernova driven wind might eventually drive any remaining gas from the system to leave a relic which will be indistinguishable from an elliptical galaxy.

  7. Dark matter in the outer solar system

    NASA Technical Reports Server (NTRS)

    Owen, T.; Cruikshank, D.; De Bergh, C.; Geballe, T.

    1994-01-01

    There are now a large number of small bodies in the outer solar system that are known to be covered with dark material. Attempts to identify that material have been thwarted by the absence of discrete absorption features in the reflection spectra of these planetesimals. An absorption at 2.2 micrometers that appeared to be present in several objects has not been confirmed by new observations. Three absorptions in the spectrum of the unusually red planetesimal 5145 Pholus are well-established, but their identity remains a mystery.

  8. Application of alternating PSM to sub-quarter-micrometer technology using i-line lithography

    NASA Astrophysics Data System (ADS)

    Kim, Hung-Eil; Ahn, Chang-Nam; Kim, KeunYoung; Baik, Ki-Ho

    1995-12-01

    Alternating phase shift mask (PSM) is very effective to memory devices which have highly repeated patterns. In order to apply the alternating PSM to a real device, we have investigated the design problems such as proximity effect, phase contradiction, phase transition, and linewidth variation. We also designed various hard defects to check defect printability on a wafer. Using i-line lithography (0.50 NA, 0.46 sigma) with alternating PSM, we obtained a useful DOF of 1.2 micrometer for a bit line of 256 M DRAM. The experimental and simulation results for phase-induced problems and defect printability on wafer are described in detail.

  9. Pulse height response of an optical particle counter to monodisperse aerosols

    NASA Technical Reports Server (NTRS)

    Wilmoth, R. G.; Grice, S. S.; Cuda, V.

    1976-01-01

    The pulse height response of a right angle scattering optical particle counter has been investigated using monodisperse aerosols of polystyrene latex spheres, di-octyl phthalate and methylene blue. The results confirm previous measurements for the variation of mean pulse height as a function of particle diameter and show good agreement with the relative response predicted by Mie scattering theory. Measured cumulative pulse height distributions were found to fit reasonably well to a log normal distribution with a minimum geometric standard deviation of about 1.4 for particle diameters greater than about 2 micrometers. The geometric standard deviation was found to increase significantly with decreasing particle diameter.

  10. Solar radiation absorbing material

    DOEpatents

    Googin, John M.; Schmitt, Charles R.; Schreyer, James M.; Whitehead, Harlan D.

    1977-01-01

    Solar energy absorbing means in solar collectors are provided by a solar selective carbon surface. A solar selective carbon surface is a microporous carbon surface having pores within the range of 0.2 to 2 micrometers. Such a surface is provided in a microporous carbon article by controlling the pore size. A thermally conductive substrate is provided with a solar selective surface by adhering an array of carbon particles in a suitable binder to the substrate, a majority of said particles having diameters within the range of about 0.2-10 microns.

  11. Galileo infrared imaging spectroscopy measurements at venus

    USGS Publications Warehouse

    Carlson, R.W.; Baines, K.H.; Encrenaz, Th.; Taylor, F.W.; Drossart, P.; Kamp, L.W.; Pollack, James B.; Lellouch, E.; Collard, A.D.; Calcutt, S.B.; Grinspoon, D.; Weissman, P.R.; Smythe, W.D.; Ocampo, A.C.; Danielson, G.E.; Fanale, F.P.; Johnson, T.V.; Kieffer, H.H.; Matson, D.L.; McCord, T.B.; Soderblom, L.A.

    1991-01-01

    During the 1990 Galileo Venus flyby, the Near Infrared Mapping Spectrometer investigated the night-side atmosphere of Venus in the spectral range 0.7 to 5.2 micrometers. Multispectral images at high spatial resolution indicate substantial cloud opacity variations in the lower cloud levels, centered at 50 kilometers altitude. Zonal and meridional winds were derived for this level and are consistent with motion of the upper branch of a Hadley cell. Northern and southern hemisphere clouds appear to be markedly different. Spectral profiles were used to derive lower atmosphere abundances of water vapor and other species.

  12. Femtosecond laser direct writing of metal microstructure in a stretchable poly(ethylene glycol) diacrylate (PEGDA) hydrogel.

    PubMed

    Terakawa, Mitsuhiro; Torres-Mapa, Maria Leilani; Takami, Akihiro; Heinemann, Dag; Nedyalkov, Nikolay N; Nakajima, Yasutaka; Hördt, Anton; Ripken, Tammo; Heisterkamp, Alexander

    2016-04-01

    The fabrication of three-dimensional (3D) metal microstructures in a synthetic polymer-based hydrogel is demonstrated by femtosecond laser-induced photoreduction. The linear-shaped silver structure of approximately 2 micrometers in diameter is fabricated inside a biocompatible poly(ethylene glycol) diacrylate (PEGDA) hydrogel. The silver structure is observed and confirmed by scanning electron microscopy (SEM) and elemental analysis using energy-dispersive X-ray spectroscopy (EDX). Shrinking and swelling of the fabricated structure is also demonstrated experimentally, which shows the potential of the present method for realizing 3D flexible electronic and optical devices, as well as for fabricating highly integrated devices at submicron scales.

  13. Ubiquity of biological ice nucleators in snowfall.

    PubMed

    Christner, Brent C; Morris, Cindy E; Foreman, Christine M; Cai, Rongman; Sands, David C

    2008-02-29

    Despite the integral role of ice nucleators (IN) in atmospheric processes leading to precipitation, their sources and distributions have not been well established. We examined IN in snowfall from mid- and high-latitude locations and found that the most active were biological in origin. Of the IN larger than 0.2 micrometer that were active at temperatures warmer than -7 degrees C, 69 to 100% were biological, and a substantial fraction were bacteria. Our results indicate that the biosphere is a source of highly active IN and suggest that these biological particles may affect the precipitation cycle and/or their own precipitation during atmospheric transport.

  14. Three-Dimensional Wind Profiling of Offshore Wind Energy Areas With Airborne Doppler Lidar

    NASA Technical Reports Server (NTRS)

    Koch, Grady J.; Beyon, Jeffrey Y.; Cowen, Larry J.; Kavaya, Michael J.; Grant, Michael S.

    2014-01-01

    A technique has been developed for imaging the wind field over offshore areas being considered for wind farming. This is accomplished with an eye-safe 2-micrometer wavelength coherent Doppler lidar installed in an aircraft. By raster scanning the aircraft over the wind energy area (WEA), a three-dimensional map of the wind vector can be made. This technique was evaluated in 11 flights over the Virginia and Maryland offshore WEAs. Heights above the ocean surface planned for wind turbines are shown to be within the marine boundary layer, and the wind vector is seen to show variation across the geographical area of interest at turbine heights.

  15. Solid C triple bond N bearing material on outer solar system bodies.

    PubMed

    Cruikshank, D P; Allamandola, L J; Hartmann, W K; Tholen, D J; Brown, R H; Matthews, C N; Bell, J F

    1991-01-01

    Using telescopic observations by ourselves and other observers, we have identified cyano-group containing molecules in the very dark solids on the surfaces of a few D-class asteroids, the dust of some comets, and low-albedo hemisphere of Iapetus, and the rings of Uranus, through spectroscopic detection of the 2.2-micrometers overtone of the C triple bond N stretching fundamental mode. The occurrence of this band on all four classes of small Solar System bodies may be diagnostic of the duration of exposure and degree of modification of surface materials, and may also establish a link between outer Solar System and interstellar materials.

  16. Eos, Koronis, and Maria Family Asteroids: Infrared (JHK) Photometry

    NASA Technical Reports Server (NTRS)

    Veeder, Glenn J.; Matson, Dennis L.; Owensby, Pamela D.; Gradie, Jonathan C.; Bell, Jeffrey F.; Tedesco, Edward F.

    1995-01-01

    Infrared photometry at 1.2, 1.6, and 2.2 micrometer (JHK) is reported for 56 asteroids in the Eos, Koronis and, Maria dynamical families. These data are consistent with similar surface composition for all of the asteroids of each family. The infrared colors within each family cluster in the region observed for the S taxonomic class, but Eos asteroids may belong to a separable K class. Asteroid 243 Ida, which was observed by the Galileo spacecraft, is a typical member of the Koronis family. The average infrared colors of the Maria family are slightly redder than those of the Eos and Koronis families.

  17. Growth defects in thick ion-plated coatings

    NASA Technical Reports Server (NTRS)

    Spalvins, T.

    1975-01-01

    Industrial ion plating conditions were selected to deposit metallic coatings such as copper, gold, and chromium 2 micrometer thick on metal and glass substrates. The surface finishes of 304 stainless steel, copper, and brass were utilized with mechanically and electrolytically polished surfaces. Nodular growth occurred in these coatings during ion plating as revealed by scanning electron microscopy. Surface irregularities such as scratches, steps, ledges, and so forth are responsible for outward growth, the typical cone type, whereas surface contaminants and loosely settled foreign particles are responsible for lateral growth; namely, the extreme localized surface outgrowths. These defect crystallographic features create porosity in the coatings when subjected to stresses and strains.

  18. Airborne studies of the emissions from the volcanic eruptions of mount st. Helens.

    PubMed

    Hobbs, P V; Radke, L F; Eltgroth, M W; Hegg, D A

    1981-02-20

    The concentrations of particles less than 10 micrometers in diameter in the ash emissions from Mount St. Helens have been more than 1000 times greater than those in the ambient air. Mass loadings of particles less than 2 micrometers in diameter were generally several hundred micrograms per cubic meter. In the ash clouds, produced by the large eruption on 18 May 1980, the concentrations of several trace gases generally were low. In other emissions, significant, but variable, concentrations of sulfur gases were measured. The 18 May eruption produced nuées ardentes, lightning flashes, and volcanic hail.

  19. Airborne studies of the emissions from the volcanic eruptions of Mount St. Helens

    SciTech Connect

    Hobbs, P.V.; Radke, L.F.; Eltgroth, M.W.; Hegg, D.A.

    1981-01-01

    The concentrations of particles less than 10 micrometers in diameter in the ash emissions from Mount St. Helens have been more than 1000 times greater than those in the ambient air. Mass loadings of particles less than 2 micrometers in diameter were generally several hundred micrograms per cubic meter. In the ash clouds, produced by the large eruption on 18 May 1980, the concentrations of several trace gases generally were low. In other emissions, significant, but variable, concentrations of sulfur gases were measured. The 18 May eruption produced nuees ardentes, lightning flashes, and volcanic hail.

  20. Solid State Radiation Dosimeters for Space and Medical Applications

    NASA Technical Reports Server (NTRS)

    Buehler, Martin G. (Editor)

    1996-01-01

    This report describes the development of two radiation monitors (RADMON's) for use in detecting total radiation dose and high-energy particles. These radiation detectors are chip-size devices fabricated in 1.2 micrometer CMOS and have flown in space on both experimental and commercial spacecraft. They have been used to characterize protons and electrons in the Earth's radiation belts, particles from the Sun, and protons used for medical therapy. Having proven useful in a variety of applications, the detector is now being readied for commercialization.

  1. Halite particles injected into the stratosphere by the 1982 el chichon eruption.

    PubMed

    Woods, D C; Chuan, R L; Rose, W I

    1985-10-11

    Halite particles about 2 micrometers in size were collected by a quartz crystal microbalance cascade impactor from the El Chichón eruption cloud in the lower stratosphere during April and May 1982. These particles are probably derived from the erupted chloride-rich, alkalic magma. Enrichments of hydrogen chloride and increases in optical depolarization in the eruption cloud observed by lidar measurements may reflect the influence of the halite particles. There is evidence that the halite particles reacted with sulfuric acid after about 1 month, releasing gaseous hydrogen chloride, which can influence the catalytic destruction of ozone in the stratosphere.

  2. Search for magnetite in lunar rocks and fines.

    PubMed

    Jedwab, J; Herbosch, A; Wollast, R; Naessens, G; Van Geen-Peers, N

    1970-01-30

    Magnetite crystals larger than 2 micrometers are absent from rocks and fines. Smaller opaque spheres in the fines can tentatively be identified as magnetite. Their concentration is not higher than 1 x 10(-6) particle per particle smaller than 1 millimeter. In the fines from the sampling site, the contribution of material similar to type 1 carbonaceous meteorites is insignificant, either because it never existed, or because it was evaporated or comminuted by impact or was diluted by indigenous material. Other magnetite habits typical of carbonaceous meteorites or possibly of cosmic dust or comets were also sought without success-such as rods, platelets, framboids, spherulites, and idiomorphic crystals.

  3. Near Infrared Imaging of the Hubble Deep Field with Keck Telescope

    NASA Technical Reports Server (NTRS)

    Hogg, David W.; Neugebauer, G.; Armus, Lee; Matthews, K.; Pahre, Michael A.; Soifer, B. T.; Weinberger, A. J.

    1997-01-01

    Two deep K-band (2.2 micrometer) images, with point-source detection limits of K=25.2 mag (one sigma), taken with the Keck Telescope in subfields of the Hubble Deep Field, are presented and analyzed. A sample of objects to K=24 mag is constructed and V(sub 606)- I(sub 814) and I(sub 814)-K colors are measured. By stacking visually selected objects, mean I(sub 814)-K colors can be measured to very faint levels, the mean I(sub 814)-K color is constant with apparent magnitude down to V(sub 606)=28 mag.

  4. Omnidirectional Printing of Flexible, Stretchable, and Spanning Silver Microelectrodes

    NASA Astrophysics Data System (ADS)

    Ahn, Bok Y.; Duoss, Eric B.; Motala, Michael J.; Guo, Xiaoying; Park, Sang-Il; Xiong, Yujie; Yoon, Jongseung; Nuzzo, Ralph G.; Rogers, John A.; Lewis, Jennifer A.

    2009-03-01

    Flexible, stretchable, and spanning microelectrodes that carry signals from one circuit element to another are needed for many emerging forms of electronic and optoelectronic devices. We have patterned silver microelectrodes by omnidirectional printing of concentrated nanoparticle inks in both uniform and high-aspect ratio motifs with minimum widths of approximately 2 micrometers onto semiconductor, plastic, and glass substrates. The patterned microelectrodes can withstand repeated bending and stretching to large levels of strain with minimal degradation of their electrical properties. With this approach, wire bonding to fragile three-dimensional devices and spanning interconnects for solar cell and light-emitting diode arrays are demonstrated.

  5. JWST Primary Mirror Technology Development

    NASA Technical Reports Server (NTRS)

    Stahl, H. Philip

    2010-01-01

    Mirror Technology was identified as a (if not the) critical capability necessary to achieve the Level 1 science goals. A never before demonstrated space telescope capability was required: 6 to 8 meter class pri mary mirror, diffraction limited at 2 micrometers and operates at temperatures below 50K. Launch vehicle constraints placed significant architectural constraints: deployed/segmented primary mirror (4.5 meter fairing diameter) 20 kg/m2 areal density (PM 1000 kg mass) Such mirror technology had never been demonstrated - and did not exist

  6. Impact of shorter wavelengths on optical quality for laws

    NASA Technical Reports Server (NTRS)

    Wissinger, Alan B.; Noll, Robert J.; Tsacoyeanes, James G.; Tausanovitch, Jeanette R.

    1993-01-01

    This study explores parametrically as a function of wavelength the degrading effects of several common optical aberrations (defocus, astigmatism, wavefronttilts, etc.), using the heterodyne mixing efficiency factor as the merit function. A 60 cm diameter aperture beam expander with an expansion ratio of 15:1 and a primary mirror focal ratio of f/2 was designed for the study. An HDOS copyrighted analysis program determined the value of merit function for various optical misalignments. With sensitivities provided by the analysis, preliminary error budget and tolerance allocations were made for potential optical wavefront errors and boresight errors during laser shot transit time. These were compared with the baseline 1.5 m CO2 laws and the optical fabrication state of the art (SOA) as characterized by the Hubble Space Telescope. Reducing wavelength and changing optical design resulted in optical quality tolerances within the SOA both at 2 and 1 micrometer. However, advanced sensing and control devices would be necessary to be tightened by a factory of 1.8 for a 2 micrometer system and by 3.6 for a 1 micrometer system relative to the baseline CO2 LAWS. Available SOA components could be used for operation at 2 micrometers but operation at 1 micrometer does not appear feasible.

  7. Impact of shorter wavelengths on optical quality for laws

    NASA Technical Reports Server (NTRS)

    Wissinger, Alan B.; Noll, Robert J.; Tsacoyeanes, James G.; Tausanovitch, Jeanette R.

    1993-01-01

    This study explores parametrically as a function of wavelength the degrading effects of several common optical aberrations (defocus, astigmatism, wavefront tilts, etc.), using the heterodyne mixing efficiency factor as the merit function. A 60 cm diameter aperture beam expander with an expansion ratio of 15:1 and a primary mirror focal ratio of f/2 was designed for the study. An HDOS copyrighted analysis program determined the value of merit function for various optical misalignments. With sensitivities provided by the analysis, preliminary error budget and tolerance allocations were made for potential optical wavefront errors and boresight errors during laser shot transit time. These were compared with the baseline l.5 m CO2 LAWS and the optical fabrication state of the art (SOA) as characterized by the Hubble Space Telescope. Reducing wavelength and changing optical design resulted in optical quality tolerances within the SOA both at 2 and 1 micrometers. However, advanced sensing and control devices would be necessary to maintain on-orbit alignment. Optical tolerance for maintaining boresight stability would have to be tightened by a factor of 1.8 for a 2 micrometers system and by 3.6 for a 1 micrometers system relative to the baseline CO2 LAWS. Available SOA components could be used for operation at 2 micrometers but operation at 1 micrometers does not appear feasible.

  8. Adaptation of a Filter Assembly to Assess Microbial Bioburden of Pressurant Within a Propulsion System

    NASA Technical Reports Server (NTRS)

    Benardini, James N.; Koukol, Robert C.; Schubert, Wayne W.; Morales, Fabian; Klatte, Marlin F.

    2012-01-01

    A report describes an adaptation of a filter assembly to enable it to be used to filter out microorganisms from a propulsion system. The filter assembly has previously been used for particulates greater than 2 micrometers. Projects that utilize large volumes of nonmetallic materials of planetary protection concern pose a challenge to their bioburden budget, as a conservative specification value of 30 spores per cubic centimeter is typically used. Helium was collected utilizing an adapted filtration approach employing an existing Millipore filter assembly apparatus used by the propulsion team for particulate analysis. The filter holder on the assembly has a 47-mm diameter, and typically a 1.2-5 micrometer pore-size filter is used for particulate analysis making it compatible with commercially available sterilization filters (0.22 micrometers) that are necessary for biological sampling. This adaptation to an existing technology provides a proof-of-concept and a demonstration of successful use in a ground equipment system. This adaptation has demonstrated that the Millipore filter assembly can be utilized to filter out microorganisms from a propulsion system, whereas in previous uses the filter assembly was utilized for particulates greater than 2 micrometers.

  9. Development of improved lithium tantalate pyroelectric detectors

    NASA Technical Reports Server (NTRS)

    Byer, N. E.; Vanderjagt, A.; Holton, W.

    1978-01-01

    A program was undertaken to increase the detectivity of LiTaO3 pyroelectric detectors to meet a performance requirement of D star (500 K, 15 Hz)=4x10 to the 9th power cm Hz1/2W-1. Emphasis was placed on reduction of the thermal conductance of the detector element to its surroundings, thinning the detector wafer to a thickness less than 3 micrometers, and increasing the absorptivity of the standard metallic film coatings. During the program, thermal conductance was reduced 41 percent through the use of reticulated (slotted) structures. Self-supported detector wafers less than 2 micrometers thick were fabricated. Multiple layer coatings, including an AR coating, with 16 percent more absorptance, were designed and fabricated. Later refinements in the multilayer design program have absorptivities of 75-80 percent, but detectors with these coatings had to be more than 2 micrometers thick because of a mismatch in the thermal expansion coefficients with LiTaO3.

  10. The First Diffraction-Limited Images from the W. M. Keck Telescope

    NASA Technical Reports Server (NTRS)

    Matthews, K.; Ghez, A. M.; Weinberger, A. J.; Neugebauer, G.

    1996-01-01

    The first diffraction limited, 0.05s resolution, images on the W. M. Keck Telescope have been obtained at a wavelength of 2.2 micrometers. These images were part of an experiment to test the suitability of the Keck Telescope for speckle imaging. In order to conduct this test, it was necessary to modify the pixel scale of the Keck facility Near Infrared Camera (NIRC) to optimally sample the spatial frequencies made available by the Keck telescope. The design and implementation of the external reimaging optics, which convert the standard fl25 beam from the secondary mirror to fl182, are described here. Techniques for reducing speckle data with field rotation on an alt-az telescope are also described. Three binary stars were observed in this experiment with separations as small as 0.05s. With only 100 frames of data on each, a dynamic range of at least 3.5 mag was achieved in all cases. These observations imply that a companion as faint as 14.5 mag at 2.2 micrometers could be detected around an 11th magnitude point source.

  11. Modeling Hydrodynamics, Water Temperature, and Suspended Sediment in Detroit Lake, Oregon

    USGS Publications Warehouse

    Sullivan, Annett B.; Rounds, Stewart A.; Sobieszczyk, Steven; Bragg, Heather M.

    2007-01-01

    Detroit Lake is a large reservoir on the North Santiam River in west-central Oregon. Water temperature and suspended sediment are issues of concern in the river downstream of the reservoir. A CE-QUAL-W2 model was constructed to simulate hydrodynamics, water temperature, total dissolved solids, and suspended sediment in Detroit Lake. The model was calibrated for calendar years 2002 and 2003, and for a period of storm runoff from December 1, 2005, to February 1, 2006. Input data included lake bathymetry, meteorology, reservoir outflows, and tributary inflows, water temperatures, total dissolved solids, and suspended sediment concentrations. Two suspended sediment size groups were modeled: one for suspended sand and silt with particle diameters larger than 2 micrometers, and another for suspended clay with particle diameters less than or equal to 2 micrometers. The model was calibrated using lake stage data, lake profile data, and data from a continuous water-quality monitor on the North Santiam River near Niagara, about 6 kilometers downstream of Detroit Dam. The calibrated model was used to estimate sediment deposition in the reservoir, examine the sources of suspended sediment exiting the reservoir, and examine the effect of the reservoir on downstream water temperatures.

  12. Optical properties of cometary grains

    NASA Technical Reports Server (NTRS)

    Mukai, Tadashi

    1988-01-01

    An analysis of visible/near IF polarimetry of Comet Halley leads to a variation of the complex refractive index m = n - i x k of grain material with wavelength, i.e., a slight decrease of n from 1.39 at lambda = 0.37 micrometer to 1.37 at lambda = 2.2 micrometers, in constrast to an increase of k from 0.024 at lambda = 0.37 micrometer to 0.042 at lambda 2.2 micrometers. The mass distribution of grains reported by Mazets et al. from in situ measurements of Vega 2 was applied in the analysis. Combining these optical constants with those of astronomical silicate proposed by Draine, cometary silicate is presented as a candidate for cometary grains. The complex refractive index of the proposed cometary silicate is shown. Based on Mie theory, an emission coefficiency of each of the grains in computed as well as its temperature, as functions of grain radius and sun comet (grain) distance. It is found that the tentative thermal spectrum from these cometary silicates, where the mass distribution of grains reported by Mazets from Vega 2 was applied, fits very well to the IR spectrum of Comet Halley. This means that cometary silicate can explain not only the phase angle and wavelength dependences of visible/near IF polarization, but also the thermal emission.

  13. High Efficiency End-Pumped Ho:Tm:YLF Disk Amplifier

    NASA Technical Reports Server (NTRS)

    Yu, Jirong; Singh, Upendra N.; Petros, Mulugeta; Axenson, Theresa J.; Barnes, Norman P.

    1999-01-01

    Space based coherent lidar for global wind measurement requires an all solid state laser system with high energy, high efficiency and narrow linewidth that operates in the eye safe region. A Q-switched, diode pumped Ho:Tm:YLF 2 micrometer laser with output energy of as much as 125 mJ at 6 Hz with an optical-to-optical efficiency of 3% has been reported. Single frequency operation of the laser was achieved by injection seeding. The design of this laser is being incorporated into NASA's SPARCLE (SPAce Readiness Coherent Lidar Experiment) wind lidar mission. Laser output energy ranging from 500 mJ to 2 J is required for an operational space coherent lidar. We previously developed a high energy Ho:Tm:YLF master oscillator and side pumped power amplifier system and demonstrated a 600-mJ single frequency pulse at a repetition rate of 10 Hz. Although the output energy is high, the optical-to-optical efficiency is only about 2%. Designing a high energy, highly efficient, conductively cooled 2-micrometer laser remains a challenge. In this paper, the preliminary result of an end-pumped amplifier that has a potential to provide a factor 3 of improvement in the system efficiency is reported.

  14. Analysis of dynamic characteristics and ways of development of bipolar main memory with miniaturization of integrated circuit elements

    NASA Astrophysics Data System (ADS)

    Sergeyev, A. G.; Savenkov, V. N.; Parmenov, Y. A.; Neklyudov, V. A.; Mindeyeva, A. A.

    1984-08-01

    A forecast estimate of the characteristics of a super large scale integrated circuit (super-BIS) memory as applied to bipolar main memory (OZU) circuits is presented. The limiting speed of bipolar OSU with d 2 micrometer will be determined by the characteristics of the interconnections and not by the parameters of bipolar devices. With d 2 micrometer, slowing down of the rate of growth of the response speed of OZU must be expected as the result of miniaturization as a consequence of the increase of the specific capacities of the p-n junctions and the metallization and constraint on the current density in the interconnections. The limitation and the specific properties of the energetics of bipolar OZU--localization of the current in separate lines, leads to a variance between speed of response and the decree of integration. For realization of the potentially high speed of response of bipolar OSU an improvement is necessary of the technology of the interconnections with the object of an increase of the current density to master a three layered system of interconnections.

  15. Development of a Pulsed 2-Micron Integrated Path Differential Absorption Lidar for CO2 Measurement

    NASA Technical Reports Server (NTRS)

    Singh, Upendra N.; Yu, Jirong; Petros, Mulugeta; Refaat, Tamer; Refaat, Tamer

    2013-01-01

    Atmospheric carbon dioxide (CO2) is an important greenhouse gas that significantly contributes to the carbon cycle and global radiation budget on Earth. Active remote sensing of CO2 is important to address several limitations that contend with passive sensors. A 2-micron double-pulsed, Integrated Path Differential Absorption (IPDA) lidar instrument for ground and airborne atmospheric CO2 concentration measurements via direct detection method is being developed at NASA Langley Research Center. This active remote sensing instrument will provide an alternate approach of measuring atmospheric CO2 concentrations with significant advantages. A high energy pulsed approach provides high-precision measurement capability by having high signal-to-noise ratio level and unambiguously eliminates the contamination from aerosols and clouds that can bias the IPDA measurement. Commercial, on the shelf, components are implemented for the detection system. Instrument integration will be presented in this paper as well as a background for CO2 measurement at NASA Langley research Center

  16. X-ray lasers and methods utilizing two component driving illumination provided by optical laser means of relatively low energy and small physical size

    DOEpatents

    Rosen, Mordecai D.; Matthews, Dennis L.

    1991-01-01

    An X-ray laser (10), and related methodology, are disclosed wherein an X-ray laser target (12) is illuminated with a first pulse of optical laser radiation (14) of relatively long duration having scarcely enough energy to produce a narrow and linear cool plasma of uniform composition (38). A second, relatively short pulse of optical laser radiation (18) is uniformly swept across the length, from end to end, of the plasma (38), at about the speed of light, to consecutively illuminate continuously succeeding portions of the plasma (38) with optical laser radiation having scarcely enough energy to heat, ionize, and invert them into the continuously succeeding portions of an X-ray gain medium. This inventive double pulse technique results in a saving of more than two orders of magnitude in driving optical laser energy, when compared to the conventional single pulse approach.

  17. An all solid-state high-voltage ns trigger generator based on magnetic pulse compression and transmission line transformer.

    PubMed

    Lin, Jiajin; Yang, Jianhua; Zhang, Jiande; Chen, Xinbing

    2013-09-01

    Innovative design of an all solid-state high-voltage ns trigger generator, based on magnetic pulse compression and transmission line transformer, is presented. The repetitive trigger pulse generator was developed to trigger a 700 kV trigatron, which has been used to pulse a repetitive intense electron beam accelerator with Tesla transformer charged double pulse forming lines (PFLs). Experimental results show that the trigger pulse generator could produce 180 kV 65 ns duration pulses with a rise time of 20 ns. The repetitive trigger pulses have nice uniform in the voltage waveform. The control time jitter is less then 3 ns. Owing to its good stability and low time jitter, the high-voltage trigger generator is an excellent candidate to trigger the repetitive accelerator.

  18. Generating femtosecond X-ray pulses using an emittance-spoiling foil in free-electron lasers

    SciTech Connect

    Ding, Y. Coffee, R.; Decker, F.-J.; Emma, P.; Field, C.; Huang, Z.; Krejcik, P.; Krzywinski, J.; Loos, H.; Lutman, A.; Marinelli, A.; Maxwell, T. J.; Turner, J.; Behrens, C.; Helml, W.

    2015-11-09

    Generation of femtosecond to sub-femtosecond pulses is attracting much attention in X-ray free-electron laser user community. One method is to use a slotted, emittance-spoiling foil which was proposed before (P. Emma et al., Phys. Rev. Lett. 92, 074801 (2004)) and has been widely used at the Linac Coherent Light Source. Direct experimental characterization of the slotted-foil performance was previously unfeasible due to a lack of appropriate diagnostics. With a recently installed X-band radio-frequency transverse deflector, we are able to characterize the electron bunch spoiling effect and X-ray pulse when using the slotted foil. We show that few-femtosecond X-ray pulses are generated with flexible control of the single-pulse duration or double-pulse separation with comparison to the theoretical model.

  19. Relative refractory period in an excitable semiconductor laser.

    PubMed

    Selmi, F; Braive, R; Beaudoin, G; Sagnes, I; Kuszelewicz, R; Barbay, S

    2014-05-09

    We report on experimental evidence of neuronlike excitable behavior in a micropillar laser with saturable absorber. We show that under a single pulsed perturbation the system exhibits subnanosecond response pulses and analyze the role of the laser bias pumping. Under a double pulsed excitation we study the absolute and relative refractory periods, similarly to what can be found in neural excitability, and interpret the results in terms of a dynamical inhibition mediated by the carrier dynamics. These measurements shed light on the analogy between optical and biological neurons and pave the way to fast spike-time coding based optical systems with a speed several orders of magnitude faster than their biological or electronic counterparts.

  20. Drift chamber electronics with multi-hit capability for time and current division measurements

    NASA Astrophysics Data System (ADS)

    Manarin, A.; Pregernig, L.; Rabany, M.; Saban, R.; Vismara, G.

    1983-11-01

    Drift chambers have been installed for luminosity measurements in intersection 5 of the SPS accelerator working in p overlinep colliding mode. The required electronics is described. The system is able to process up to 16 hits per wire with a double pulse resolution of 40 ns; drift time and current division, with 1.25 ns and 1.6% resolution respectively, are recorded. Transconductance preamplifiers and discriminators are directly mounted on the chamber; 160 m of twisted-pair cable bring the signals to the digitizer unit. Coarse time is measured using RAM techniques, while fine time is obtained by means of a microstrip delay associated with a 100 K ECL priority encoder. Current division used a single 50 MHz Flash ADC which allows 26 dB dynamic range with 6 bit resolution. First operational results are reported.

  1. Atmospheric propagation of two CO2 laser pulses

    NASA Astrophysics Data System (ADS)

    Autric, M.; Caressa, J.-P.; Dufresne, D.; Bournot, Ph.

    1984-01-01

    At the intensity and fluence levels reached in an experimental investigation of high-energy laser beam propagation, air breakdown occurs through the interaction of the intense radiation with aerosol particles naturally suspended in the path of the beam. The air plasma created is found to expand rapidly and have a detrimental effect on energy propagation. It is determined that the energy transmitted through the breakdown plasma as a function of the incident average energy density is less than 15 percent for fluences greater than 300 J/sq cm, and that incident energy transmission may be increased through the generation of a precursor pulse as a function of double pulse separation times ranging from a few microsec to 0.1 sec. Maximum effects have been obtained at pulse separation intervals of 100-200 microsec, and these are ascribed to the vaporization of aerosol particles by the first pulse.

  2. Solid-State 2-Micron Laser Transmitter Advancement for Wind and Carbon Dioxide Measurements From Ground, Airborne, and Space-Based Lidar Systems

    NASA Technical Reports Server (NTRS)

    Singh, Upendra N.; Kavaya, Michael J.; Koch, Grady; Yu, Jirong; Ismail, Syed

    2008-01-01

    NASA Langley Research Center has been developing 2-micron lidar technologies over a decade for wind measurements, utilizing coherent Doppler wind lidar technique and carbon dioxide measurements, utilizing Differential Absorption Lidar (DIAL) technique. Significant advancements have been made towards developing state-of-the-art technologies towards laser transmitters, detectors, and receiver systems. These efforts have led to the development of solid-state lasers with high pulse energy, tunablility, wavelength-stability, and double-pulsed operation. This paper will present a review of these technological developments along with examples of high resolution wind and high precision CO2 DIAL measurements in the atmosphere. Plans for the development of compact high power lasers for applications in airborne and future space platforms for wind and regional to global scale measurement of atmospheric CO2 will also be discussed.

  3. Far-infrared-light shadowgraphy for high extraction efficiency of extreme ultraviolet light from a CO2-laser-generated tin plasma

    NASA Astrophysics Data System (ADS)

    Matsukuma, Hiraku; Hosoda, Tatsuya; Suzuki, Yosuke; Yogo, Akifumi; Yanagida, Tatsuya; Kodama, Takeshi; Nishimura, Hiroaki

    2016-08-01

    The two-color, double-pulse method is an efficient scheme to generate extreme ultraviolet light for fabricating the next generation semiconductor microchips. In this method, a Nd:YAG laser pulse is used to expand a several-tens-of-micrometers-scale tin droplet, and a CO2 laser pulse is subsequently directed at the expanded tin vapor after an appropriate delay time. We propose the use of shadowgraphy with a CO2 laser probe-pulse scheme to optimize the CO2 main-drive laser. The distribution of absorption coefficients is derived from the experiment, and the results are converted to a practical absorption rate for the CO2 main-drive laser.

  4. Laser ablation process for single-walled carbon nanotube production

    NASA Technical Reports Server (NTRS)

    Arepalli, Sivaram

    2004-01-01

    Different types of lasers are now routinely used to prepare single-walled carbon nanotubes. The original method developed by researchers at Rice University used a "double-pulse laser oven" process. Several researchers have used variations of the lasers to include one-laser pulse (green or infrared), different pulse widths (ns to micros as well as continuous wave), and different laser wavelengths (e.g., CO2, or free electron lasers in the near to far infrared). Some of these variations are tried with different combinations and concentrations of metal catalysts, buffer gases (e.g., helium), oven temperatures, flow conditions, and even different porosities of the graphite targets. This article is an attempt to cover all these variations and their relative merits. Possible growth mechanisms under these different conditions will also be discussed.

  5. Quadratic System Identification: a statistical framework for the paired-pulse paradigm.

    PubMed

    Arunajadai, Srikesh G

    2010-03-01

    System Identification refers to the problem of identifying a model or description of a system based on a stretch of input and the corresponding output from the system. The paired-pulse paradigm or the conditioning test pulse paradigm is often used in neurophysiology experiments. In this work we provide a statistical framework for the conditioning test pulse paradigm which also serves as a system identification tool for quadratic or second order Volterra systems. A nonparametric spectral domain based methodology is proposed for the quadratic system identification. It is shown that by carrying out the analysis in the spectral domain one needs to perform only a single set of double pulse experiments as opposed to multiple sets of experiments in the time domain. Simulation studies are performed to assess the performance of the methodology and to study the conditions under which the methods are expected to perform well.

  6. The insecticide DDT decreases membrane potential and cell input resistance of cultured human liver cells.

    PubMed

    Schefczik, K; Buff, K

    1984-10-03

    The resting membrane potential, Em, and the cell input resistance, Rinp, of cultured human Chang liver cells were measured using the single electrode 'double-pulse' current clamp technique, following exposure of the cells to the insecticide DDT (20 microM). In control (unexposed) cells, the mean Em was -24 mV, and the mean Rinp was 30 M omega. Neither parameter was significantly impaired after 1 h of cell exposure to DDT. But after 7 and 48 h, the Em was depolarized by 15 and 25 mV, respectively, in parallel with a decrease of the cell input resistance. The strongly time-delayed effect of DDT on Chang liver cell membranes may indicate a mode of interaction different from excitable membranes.

  7. The use of laser-induced breakdown spectroscopy for the determination of fluorine concentration in glass ionomer cement

    NASA Astrophysics Data System (ADS)

    Kratochvíl, T.; Pouzar, M.; Novotný, K.; Havránek, V.; Černohorský, T.; Zvolská, M.

    2013-10-01

    The influence of He atmosphere and gate width in laser-induced breakdown spectroscopy (LIBS) determination of fluorine concentration was investigated in detail. The measurements were realized on two double pulse LIBS devices featuring different parameters. Calibration curves, describing the relationship between the fluorine concentration and the corresponding intensity of the LIBS signal, were constructed for both LIBS devices, with and without He flow, respectively. Detection limits achieved were in the range 1.18-0.47 wt.%. The best LOD value was obtained in He atmosphere. The LIBS measurement of fluorine content is influenced by different gate widths and the atmosphere in the working chamber. The proposed method was successfully applied to the determination of fluorine concentration in glass ionomer cements.

  8. PIP₂ hydrolysis is responsible for voltage independent inhibition of CaV2.2 channels in sympathetic neurons.

    PubMed

    Vivas, Oscar; Castro, Hector; Arenas, Isabel; Elías-Viñas, David; García, David E

    2013-03-08

    GPCRs regulate Ca(V)2.2 channels through both voltage dependent and independent inhibition pathways. The aim of the present work was to assess the phosphatidylinositol-4,5-bisphosphate (PIP2) as the molecule underlying the voltage independent inhibition of Ca(V)2.2 channels in SCG neurons. We used a double pulse protocol to study the voltage independent inhibition and changed the PIP(2) concentration by means of blocking the enzyme PLC, filling the cell with a PIP(2) analogue and preventing the PIP(2) resynthesis with wortmannin. We found that voltage independent inhibition requires the activation of PLC and can be hampered by internal dialysis of exogenous PIP(2). In addition, the recovery from voltage independent inhibition is blocked by inhibition of the enzymes involved in the resynthesis of PIP(2). These results support that the hydrolysis of PIP(2) is responsible for the voltage independent inhibition of Ca(V)2.2 channels.

  9. Sound production in marbled rockfish (Sebastiscus marmoratus) and implications for fisheries.

    PubMed

    Zhang, Xuguang; Guo, Hongyi; Zhang, Shouyu; Song, Jiakun

    2015-01-01

    Recently, several rockfish species (genus Sebastes) have been reported to be soniferous. To determine whether an additional rockfish species produces sounds, passive acoustic recordings were analyzed from captive marbled rockfish (Sebastiscus marmoratus) during the non-spawning season. Three distinct sounds were identified based on frequency features. The common characteristics among all sounds were low frequency (below 300 Hz) and rapidly dampened pulses consisting of 3-5 acoustic energy cycles. During free-swimming conditions in the canvas tank, the fish produced voluntary sounds with lower frequencies than the disturbance sounds produced by individuals during prodding. Two types of sounds were identified in the disturbance context: one type consists of single or double pulses with two peak frequencies, and another type consists of a series of pulses with a single peak frequency. These results suggest that specific-species and behavior-associated sounds are potentially useful in passive acoustical surveys to monitor rockfish populations and distributions remotely.

  10. A Ground-Based 2-Micron DIAL System to Profile Tropospheric CO2 and Aerosol Distributions for Atmospheric Studies

    NASA Technical Reports Server (NTRS)

    Ismail, Syed; Koch, Grady; Abedin, Nurul; Refaat, Tamer; Rubio, Manuel; Davis, Kenneth; Miller, Charles; Singh, Upendra

    2006-01-01

    System will operate at a temperature insensitive CO2 line (2050.967 nm) with side-line tuning and off-set locking. Demonstrated an order of magnitude improvement in laser line locking needed for high precision measurements, side-line operation, and simultaneously double pulsing and line locking. Detector testing of phototransistor has demonstrated sensitivity to aerosol features over long distances in the atmosphere and resolve features approx. 100m. Optical systems that collect light onto small area detectors work well. Receiver optical designs are being optimized and data acquisition systems developed. CO2 line parameter characterization in progress In situ sensor calibration in progress for validation of DIAL CO2 system.

  11. In situ industrial applications of optics; Proceedings of the Meeting, Brussels, Belgium, June 25-27, 1986

    NASA Astrophysics Data System (ADS)

    Ebbeni, Jean

    Included in this volume are papers on real-time image enhancement by simple video systems, automatic identification and data collection via barcode laser scanning, the optimization of the cutting up of a strip of float glass, optical sensors for factory automation, and the use of a digital theodolite with infrared radiation. Attention is also given to ISIS (integrated shape imaging system), a new system for follow-up of scoliosis; optical diffraction extensometers; a cross-spectrum technique for high-sensitivity remote vibration analysis by optical interferometry; the compensation and measurement of any motion of three-dimensional objects in holographic interferometry; and stereoscreen. Additional papers are on holographic double pulse YAG lasers, miniature optic connectors, stress-field analysis in an adhesively bonded joint with laser photoelasticimetry, and the locking of the light pulse delay in externally triggered gas lasers.

  12. Optimal control of the strong-field ionization of silver clusters in helium droplets

    SciTech Connect

    Truong, N. X.; Goede, S.; Przystawik, A.; Fennel, Th.; Bornath, Th.; Tiggesbaeumker, J.; Meiwes-Broer, K. H.; Hilse, P.; Schlanges, M.; Doeppner, T.; Gerber, G.

    2010-01-15

    Optimal control techniques combined with femtosecond laser pulse shaping are applied to steer and enhance the strong-field induced emission of highly charged atomic ions from silver clusters embedded in helium nanodroplets. With light fields shaped in amplitude and phase we observe a substantial increase of the Ag{sup q+} yield for q>10 when compared to bandwidth-limited and optimally stretched pulses. A remarkably simple double-pulse structure, containing a low-intensity prepulse and a stronger main pulse, turns out to produce the highest atomic charge states up to Ag{sup 20+}. A negative chirp during the main pulse hints at dynamic frequency locking to the cluster plasmon. A numerical optimal control study on pure silver clusters with a nanoplasma model converges to a similar pulse structure and corroborates that the optimal light field adapts to the resonant excitation of cluster surface plasmons for efficient ionization.

  13. Application of laser-induced breakdown spectroscopy to the analysis of algal biomass for industrial biotechnology

    NASA Astrophysics Data System (ADS)

    Pořízka, P.; Prochazka, D.; Pilát, Z.; Krajcarová, L.; Kaiser, J.; Malina, R.; Novotný, J.; Zemánek, P.; Ježek, J.; Šerý, M.; Bernatová, S.; Krzyžánek, V.; Dobranská, K.; Novotný, K.; Trtílek, M.; Samek, O.

    2012-08-01

    We report on the application of laser-induced breakdown spectroscopy (LIBS) to the determination of elements distinctive in terms of their biological significance (such as potassium, magnesium, calcium, and sodium) and to the monitoring of accumulation of potentially toxic heavy metal ions in living microorganisms (algae), in order to trace e.g. the influence of environmental exposure and other cultivation and biological factors having an impact on them. Algae cells were suspended in liquid media or presented in a form of adherent cell mass on a surface (biofilm) and, consequently, characterized using their spectra. In our feasibility study we used three different experimental arrangements employing double-pulse LIBS technique in order to improve on analytical selectivity and sensitivity for potential industrial biotechnology applications, e.g. for monitoring of mass production of commercial biofuels, utilization in the food industry and control of the removal of heavy metal ions from industrial waste waters.

  14. An improved mixed numerical-experimental method for stress field calculation

    NASA Astrophysics Data System (ADS)

    Lopes, H. M. R.; Guedes, R. M.; Vaz, M. A.

    2007-07-01

    In this work a numerical-experimental method is used to study the dynamic behavior of an aluminum plate subjected to a small mass impact. The out-of-plane displacements, due to transient bending wave propagation, were assessed for successive time instants, using double pulse TV-holography, also known as pulsed ESPI. The experimental setup and the image processing methods were improved to allow the calculation of the plate transient stress field. Integral transforms are used to obtain the strain fields from spatial derivatives of displacements noisy data. A numerical simulation of the plate transient response was carried out with FEM Ansys ®. For this purpose a PZT transducer was used to record the impact force history, which was inputted in the numerical model. Finally, the comparisons between numerical and experimental results are presented in order to validate the present methodology.

  15. Microchip in situ electrosynthesis of silver metallic oxide clusters for ultra-FAST detection of galactose in galactosemic newborns' urine samples.

    PubMed

    García-Carmona, Laura; Rojas, Daniel; González, María Cristina; Escarpa, Alberto

    2016-10-17

    This work describes for the first time the coupling of microfluidic chips (MC) to electrosynthetized silver metallic oxide clusters (AgMOCs). As an early demonstration of this novel approach, the ultrafast detection of galactose in galactosemic newborns' urine samples is proposed. AgMOCs were in situ electrosynthetized on integrated microchip platinum electrodes using a double pulse technique and characterized in full using scanning electronic microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS) and electrochemical techniques revealing the presence of silver oxides and electrocatalysis towards galactose as a galactosemia biomarker. Galactose detection in galactosemic newborns' urine samples proceeded in less than 30 s, differentiating between ill and healthy urine samples and requiring negligible urine sample consumption. The significance of the newborns' urine samples confirmed the analytical potency of the MC-AgMOCs approach for future implementation of screening for rare disease diagnosis such as galactosemia.

  16. Application of holography to flow visualization within rotating compressor blade row. [to determine three dimensional shock patterns

    NASA Technical Reports Server (NTRS)

    Wuerker, R. F.; Kobayashi, R. J.; Heflinger, L. O.; Ware, T. C.

    1974-01-01

    Two holographic interblade row flow visualization systems were designed to determine the three-dimensional shock patterns and velocity distributions within the rotating blade row of a transonic fan rotor, utilizing the techniques of pulsed laser transmission holography. Both single- and double-exposure bright field holograms and dark field scattered-light holograms were successfully recorded. Two plastic windows were installed in the rotor tip casing and outer casing forward of the rotor to view the rotor blade passage. The viewing angle allowed detailed investigation of the leading edge shocks and shocks in the midspan damper area; limited details of the trailing edge shocks also were visible. A technique was devised for interpreting the reconstructed holograms by constructing three dimensional models that allowed identification of the major shock systems. The models compared favorably with theoretical predictions and results of the overall and blade element data. Most of the holograms were made using the rapid double-pulse technique.

  17. New μSR spectrometer at J-PARC MUSE based on Kalliope detectors

    NASA Astrophysics Data System (ADS)

    Kojima, K. M.; Murakami, T.; Takahashi, Y.; Lee, H.; Suzuki, S. Y.; Koda, A.; Yamauchi, I.; Miyazaki, M.; Hiraishi, M.; Okabe, H.; Takeshita, S.; Kadono, R.; Ito, T.; Higemoto, W.; Kanda, S.; Fukao, Y.; Saito, N.; Saito, M.; Ikeno, M.; Uchida, T.; Tanaka, M. M.

    2014-12-01

    We developed a new positron detector system called Kalliope, which is based on multi-pixel avalanch photo-diode (m-APD), application specific integrated circuit (ASIC), field programmable gated array (FPGA) and ethernet-based SiTCP data transfer technology. We have manufactured a general-purpose spectrometer for muon spin relaxation (μSR) measurements, employing 40 Kalliope units (1280 channels of scintillators) installed in a 0.4 T longitudinal-field magnet. The spectrometer has been placed at D1 experimental area of J- PARC Muon Science Establishment (MUSE). Since February of 2014, the spectrometer has been used for the user programs of MUSE after a short commissioning period of one week. The data accumulation rate of the new spectrometer is 180 million positron events per hour (after taking the coincidence of two scintillators of telescopes) from a 20×20 mm sample for double-pulsed incoming muons.

  18. Femtosecond laser processing of fused silica and aluminum based on electron dynamics control by shaping pulse trains

    NASA Astrophysics Data System (ADS)

    Leng, Ni; Jiang, Lan; Li, Xin; Xu, Chuancai; Liu, Pengjun; Lu, Yongfeng

    2012-11-01

    The pulse train effects on femtosecond laser material processing are investigated from the viewpoint of electron dynamics on dielectrics with fused silica as a case study and metals with Al as a case study in air and water. During femtosecond laser (800 nm, 35 fs) pulse train (double pulses per train) processing of fused silica, a non-monotonic relationship between ablation size and pulse separation is observed with an abrupt rise in the range of 150-275 fs. It is assumed that this is due to the enhancement of photon-electron coupling efficiency and transition of the phase-change mechanism by adjusting the free electron density during pulse train ablation. Surface quality in Al is improved with less recast by designing the pulse energy distribution to adjust the electron/lattice temperature distribution. Furthermore, the positive effects on ablation quality by femtosecond pulse train technology are more significant in water than those in air.

  19. Somatosensory Electrical Stimulation Does Not Augment Motor Skill Acquisition and Intermanual Transfer in Healthy Young Adults - A Pilot Study.

    PubMed

    Négyesi, János; Veldman, Menno P; Berghuis, Kelly M M; Javet, Marie; Tihanyi, József; Hortobágyi, Tibor

    2017-03-24

    Sensory input can modify motor function and magnify interlimb transfer. We examined the effects of low-intensity somatosensory electrical stimulation (SES) on motor practice-induced (MP) skill acquisition and intermanual transfer. Participants practiced a visuomotor skill for 25 minutes and received SES to the practice or the transfer arm. Responses to single- and double pulse transcranial magnetic stimulation (TMS) were measured in both extensor carpi radialis. SES did not further increase skill acquisition (RMP: 30.8%, RMP+RSES: 27.8%) and intermanual transfer (RMP: 13.6%, RMP+RSES: 9.8%) when delivered to the left arm (RMP+LSES: 44.8%, 18.6%, respectively). Furthermore, TMS measures revealed no changes in either hand. Future studies should systematically manipulate SES parameters to better understand the mechanisms of how SES affords motor learning benefits documented but not studied in patients.

  20. Local deposition of anisotropic nanoparticles using scanning electrochemical microscopy (SECM).

    PubMed

    Fedorov, Roman G; Mandler, Daniel

    2013-02-28

    We demonstrate localized electrodeposition of anisotropic metal nanoobjects, namely Au nanorods (GNR), on indium tin oxide (ITO) using scanning electrochemical microscopy (SECM). A gold microelectrode was the source of the gold ions whereby double pulse chronoamperometry was employed to generate initially Au seeds which were further grown under controlled conditions. The distance between the microelectrode and the ITO surface as well as the different experimental parameters (electrodeposition regime, solution composition and temperature) were optimized to produce faceted gold seeds with the required characteristics (size and distribution). Colloidal chemical synthesis was successfully exploited for better understanding the role of the surfactant and different additives in breaking the crystallographic symmetry and anisotropic growth of GNR. Experiments performed in a conventional three-electrode cell revealed the most appropriate electrochemical conditions allowing high yield synthesis of nanorods with well-defined shape as well as nanocubes and bipyramids.

  1. Measurement of Sub-Picosecond Electron Bunches via Electro-Optic Sampling of Coherent Transition Radiation

    SciTech Connect

    Maxwell, Timothy John

    2012-01-01

    Future collider applications as well as present high-gradient laser plasma wakefield accelerators and free-electron lasers operating with picosecond bunch durations place a higher demand on the time resolution of bunch distribution diagnostics. This demand has led to significant advancements in the field of electro-optic sampling over the past ten years. These methods allow the probing of diagnostic light such as coherent transition radiation or the bunch wakefields with sub-picosecond time resolution. We present results on the single-shot electro-optic spectral decoding of coherent transition radiation from bunches generated at the Fermilab A0 photoinjector laboratory. A longitudinal double-pulse modulation of the electron beam is also realized by transverse beam masking followed by a transverse-to-longitudinal phase-space exchange beamline. Live profile tuning is demonstrated by upstream beam focusing in conjunction with downstream monitoring of single-shot electro-optic spectral decoding of the coherent transition radiation.

  2. Pressure-driven sound turbulence in a high-beta plasma

    NASA Technical Reports Server (NTRS)

    Stenzel, R. L.

    1990-01-01

    LF turbulence is investigated experimentally in a 2-m-long 1-m-diameter magnetized electron fluid with beta(e) = about 0.5 and unmagnetized ions, generated in a double-pulsed linear dc discharge under a uniform external magnetic field of 15 G. The results of measurements with Langmuir probes, electric probes, and a directional particle analyzer are presented in graphs and characterized in detail. It is shown that the strong cross-field sound turbulence observed near the lower hybrid frequency is caused by the electron pressure gradient rather than E x B drift, with (1) temperature-gradient wave refraction as the dominant saturation mechanism, (2) wave-enhanced ion mass flow, and (3) only negligible ion-tail formation. The relevance of the present findings for studies of magnetic shock propagation is indicated.

  3. Development of a pulsed 2-micron integrated path differential absorption lidar for CO2 measurement

    NASA Astrophysics Data System (ADS)

    Singh, Upendra N.; Yu, Jirong; Petros, Mulugeta; Refaat, Tamer; Reithmaier, Karl

    2013-09-01

    Atmospheric carbon dioxide (CO2) is an important greenhouse gas that significantly contributes to the carbon cycle and global radiation budget on Earth. Active remote sensing of CO2 is important to address several limitations that contend with passive sensors. A 2-micron double-pulsed, Integrated Path Differential Absorption (IPDA) lidar instrument for ground and airborne atmospheric CO2 concentration measurements via direct detection method is being developed at NASA Langley Research Center. This active remote sensing instrument will provide an alternate approach of measuring atmospheric CO2 concentrations with significant advantages. A high energy pulsed approach provides high-precision measurement capability by having high signal-to-noise ratio level and unambiguously eliminates the contamination from aerosols and clouds that can bias the IPDA measurement. Commercial, on the shelf, components are implemented for the detection system. Instrument integration will be presented in this paper as well as a background for CO2 measurement at NASA Langley research Center.

  4. Laser synthesis and modification of composite nanoparticles in liquids

    SciTech Connect

    Tarasenko, N V; Butsen, A V

    2010-12-29

    The works devoted to the formation and modification of nanoparticles using laser ablation of solid targets in liquids are reviewed. Several approaches to implement laser ablation in liquids, aimed at synthesising nanoparticles of complex composition, are considered: direct laser ablation of a target of corresponding composition, laser ablation of a combined target composed of two different metals, laser irradiation of a mixture of two or more colloidal solutions, and laser ablation in reactive liquids. The properties of two-component bimetallic systems (Ag - Cu, Ag - Au), semiconductor nanocrystals (ZnO, CdSe), chalcopyrite nanoparticles, and doped oxide nanoparticles (ZnO:Ag, Gd{sub 2}O{sub 2}:Tb{sup 3+}) formed as a result of single- and double-pulse laser ablation in different liquids (water, ethanol, acetone, solutions of polysaccharides) are discussed. (photonics and nanotechnology)

  5. A microcontroller system for investigating the catch effect: functional electrical stimulation of the common peroneal nerve.

    PubMed

    Hart, D J; Taylor, P N; Chappell, P H; Wood, D E

    2006-06-01

    Correction of drop foot in hemiplegic gait is achieved by electrical stimulation of the common peroneal nerve with a series of pulses at a fixed frequency. However, during normal gait, the electromyographic signals from the tibialis anterior muscle indicate that muscle force is not constant but varies during the swing phase. The application of double pulses for the correction of drop foot may enhance the gait by generating greater torque at the ankle and thereby increase the efficiency of the stimulation with reduced fatigue. A flexible controller has been designed around the Odstock Drop Foot Stimulator to deliver different profiles of pulses implementing doublets and optimum series. A peripheral interface controller (PIC) microcontroller with some external circuits has been designed and tested to accommodate six profiles. Preliminary results of the measurements from a normal subject seated in a multi-moment chair (an isometric torque measurement device) indicate that profiles containing doublets and optimum spaced pulses look favourable for clinical use.

  6. A parametric study of single-wall carbon nanotube growth by laser ablation

    NASA Technical Reports Server (NTRS)

    Arepalli, Sivaram; Holmes, William A.; Nikolaev, Pavel; Hadjiev, Victor G.; Scott, Carl D.

    2004-01-01

    Results of a parametric study of carbon nanotube production by the double-pulse laser oven process are presented. The effect of various operating parameters on the production of single-wall carbon nanotubes (SWCNTs) is estimated by characterizing the nanotube material using analytical techniques, including scanning electron microscopy, transmission electron microscopy, thermo gravimetric analysis and Raman spectroscopy. The study included changing the sequence of the laser pulses, laser energy, pulse separation, type of buffer gas used, operating pressure, flow rate, inner tube diameter, as well as its material, and oven temperature. It was found that the material quality and quantity improve with deviation from normal operation parameters such as laser energy density higher than 1.5 J/cm2, pressure lower than 67 kPa, and flow rates higher than 100 sccm. Use of helium produced mainly small diameter tubes and a lower yield. The diameter of SWCNTs decreases with decreasing oven temperature and lower flow rates.

  7. Influence of excitation and deexcitation processes on the dynamics of laser-excited argon clusters

    NASA Astrophysics Data System (ADS)

    Moll, M.; Schlanges, M.; Bornath, Th.; Krainov, V. P.

    2015-03-01

    The excitation of atomic clusters by intense infrared laser pulses leads to the creation of highly charged ions and to the emission of energetic photons. These phenomena, which follow from ionization processes occurring in the cluster, depend significantly on the population of ground states and excited states in the laser-produced nanoplasma. This makes it necessary to account for collisional excitation and deexcitation processes. We investigate the interaction of femtosecond laser pulses with argon clusters by means of a nanoplasma model. Considering laser excitation with single and double pulses, we analyze the role of excitation and deexcitation processes in detail and calculate the yield of highly charged ions and of energetic photons in different wavelength regimes.

  8. Development of a strontium vapor laser with pulse repetition frequency up to 1 MHz

    NASA Astrophysics Data System (ADS)

    Soldatov, A. N.; Yudin, N. A.; Polunin, Yu. P.; Vasilieva, A. V.; Chebotarev, G. D.; Latush, E. L.; Fesenko, A. A.

    2010-09-01

    The problem of obtaining high pulse repetition frequencies in metal vapor lasers is urgent from the viewpoint of laser application to various technologies, increase of productivity of industrial laser systems, study of transient processes, etc. In addition, the high pulse repetition frequency provides large average laser radiation power in spite of a rather low energy extracted from a single lasing pulse. In this work, the possibility of increasing the pulse repetition frequency of a laser on self-terminated strontium ion transitions was investigated. The double pulse method was used to demonstrate experimentally that a pulse repetition frequency of ~1 MHz could be achieved at wavelengths of 1.03 and 1.09 μm of the strontium vapor laser. To explain the results obtained, the kinetics of the active medium was modeled using the self-consistent mathematical model of a He- Sr+ laser.

  9. Production rate enhancement of size-tunable silicon nanoparticles by temporally shaping femtosecond laser pulses in ethanol.

    PubMed

    Li, Xin; Zhang, Guangming; Jiang, Lan; Shi, Xuesong; Zhang, Kaihu; Rong, Wenlong; Duan, Ji'an; Lu, Yongfeng

    2015-02-23

    This paper proposes an efficient approach for production-rate enhancement and size reduction of silicon nanoparticles produced by femtosecond (fs) double-pulse ablation of silicon in ethanol. Compared with a single pulse, the production rate is ~2.6 times higher and the mean size of the NPs is reduced by ~1/5 with a delay of 2 ps. The abnormal enhancement in the production rate is obtained at pulse delays Δt > 200 fs. The production-rate enhancement is mainly attributed to high photon absorption efficiency. It is caused by an increase in localized transient electron density, which results from the first sub-pulse ionization of ethanol molecules before the second sub-pulse arrives. The phase-change mechanism at a critical point might reduce nanoparticle size.

  10. Portable standoff Raman system for fast detection of homemade explosives through glass, plastic, and water

    NASA Astrophysics Data System (ADS)

    Misra, Anupam K.; Sharma, Shiv K.; Acosta, Tayro E.; Porter, John N.; Lucey, Paul G.; Bates, David E.

    2012-06-01

    The University of Hawaii has been developing portable remote Raman systems capable of detecting chemicals in daylight from a safe standoff distance. We present data on standoff detection of chemicals used in the synthesis of homemade explosives (HME) using a portable standoff Raman system utilizing an 8-inch telescope. Data show that good-quality Raman spectra of various hazardous chemicals such as ammonium nitrate, potassium nitrate, potassium perchlorate, sulfur, nitrobenzene, benzene, acetone, various organic and inorganic chemicals etc. could be easily obtained from remote distances, tested up to 120 meters, with a single-pulse laser excitation and with detection time less than 1 μs. The system uses a frequency-doubled Nd:YAG pulsed laser source (532 nm, 100 mJ/pulse, 15 Hz, pulse width 10 ns) capable of firing a single or double pulse. The double-pulse configuration also allows the system to perform standoff LIBS (Laser-Induced Breakdown Spectroscopy) at 50 m range. In the standoff Raman detection, the doublepulse sequence simply doubles the signal to noise ratio. Significant improvement in the quality of Raman spectra is observed when the standoff detection is made with 1s integration time. The system uses a 50-micron slit and has spectral resolution of 8 cm-1. The HME chemicals could be easily detected through clear and brown glass bottles, PP and HDPE plastic bottles, and also through fluorescent plastic water bottles. Standoff Raman detection of HME chemical from a 10 m distance through non-visible concealed bottles in plastic bubble wrap packaging is demonstrated with 1 s integration time. Possible applications of the standoff Raman system for homeland security and environmental monitoring are discussed.

  11. Overpressure wave interaction with droplets: time resolved measurements by laser shadowscopy

    NASA Astrophysics Data System (ADS)

    Slangen, Pierre; Aprin, Laurent; Heymes, Frédéric; Munier, Laurent; Lapébie, Emmanuel; Dusserre, Gilles

    2012-10-01

    Risk sciences involve increasingly optics applications to perform accurate analysis of critical behavior such as failures, explosions, fires. In this particular context, different area sizes are investigated under high temporal sampling rate up to 10000fps. With the improvement of light sources and optical sensors, it is now possible to cope with high spatial resolution even for time resolved measurement. The paper deals with the study of the interaction between overpressure waves, occurring in case of explosion for example, with a liquid droplet present in the vicinity of the overpressure wave. This is a typical scenario encountered in case of industrial breakdown including liquid leakage and explosions. We designed an experimental setup for the evaluation of the interaction between the overpressure wave and falling liquid droplets. A gas chamber is filled with nitrogen until breakage of the outlet rupture disk at about 4 bar. The droplets fall is controlled by an automatic syringe injector placed in the overpressure wave. The imaging system is based on laser shadowscopy. The laser source is a double cavity 15mJ- 1000Hz Nd YLF laser emitting double pulses of about 10ns at 527nm. To record the double pulse after crossing the falling droplets, the transmitted light is captured by a lasersynchronized double frame camera. Since these measurements are time-synchronized, it is then possible to know accurately the different parameters of the phenomenon, such as overpressure wave velocity, droplets diameter, and Reynolds number. Different experiments have been carried out at about 4000 doubleframe/s. The paper presents the whole experiment, the enhancements of the setup and the results for different liquid products from water to acetone.

  12. Pulsed laser propulsion for low cost, high volume launch to orbit

    SciTech Connect

    Kare, J.

    1989-06-02

    Pulsed laser propulsion offers the prospect of delivering high thrust at high specific impulse (500-1000 seconds) from a very simple thruster, using the energy of a remote ground-based laser to heat an inert propellant. Current analyses indicate that payloads of approximately 1 kg per megawatt of average laser power can be launched at a rate of one payload every 15 minutes and a marginal cost of $20 to $200 per kg. A 20 MW entry-level launch system could be built using current technology at a cost of $500 million or less; it would be capable of placing 600 tons per year into LEO. The SDIO Laser Propulsion Program has been developing the technology for such a launch system since 1987. The program has conducted theoretical and experimental research on a particular class of laser-driven thruster, the planar double-pulse LSD-wave thruster, which could be used for a near-term launcher. The double-pulse thruster offers several advantages, including extreme simplicity, design flexibility, and the ability to guide a vehicle remotely by precise control of the laser beam. Small-scale experiments have demonstrated the operation of this thruster at a specific impulse of 600 seconds and 10% efficiency; larger experiments now under way are expected to increase this to at least 20% efficiency. Systems-level issues, from guidance and tracking to possible unique applications, have also been considered and will be briefly discussed. There appear to be no fundamental obstacles to creating, in the next five to ten years, a new low-cost ''pipe-line to space.'' 7 refs., 2 figs., 1 tab.

  13. Stratified Volume Diffractive Optical Elements as Low-Mass Coherent Lidar Scanners

    NASA Technical Reports Server (NTRS)

    Chambers, Diana M.; Nordin, Gregory P.; Kavaya, Michael J.

    1999-01-01

    Transmissive scanning elements for coherent laser radar systems are typically optical wedges, or prisms, which deflect the lidar beam at a specified angle and are then rotated about the instrument optical axis to produce a scan pattern. The wedge is placed in the lidar optical system subsequent to a beam-expanding telescope, implying that it has the largest diameter of any element in the system. The combination of the wedge diameter and asymmetric profile result in the element having very large mass and, consequently, relatively large power consumption required for scanning. These two parameters, mass and power consumption, are among the instrument requirements which need to be minimized when designing a lidar for a space-borne platform. Reducing the scanner contributions in these areas will have a significant effect on the overall instrument specifications, Replacing the optical wedge with a diffraction grating on the surface of a thin substrate is a straight forward approach with potential to reduce the mass of the scanning element significantly. For example, the optical wedge that will be used for the SPAce Readiness Coherent Lidar Experiment (SPARCLE) is approximately 25 cm in diameter and is made from silicon with a wedge angle designed for 30 degree deflection of a beam operating at approx. 2 micrometer wavelength. The mass of this element could be reduced by a factor of four by instead using a fused silica substrate, 1 cm thick, with a grating fabricated on one of the surfaces. For a grating to deflect a beam with a 2 micrometer wavelength by 30 degrees, a period of approximately 4 micrometers is required. This is small enough that fabrication of appropriate high efficiency blazed or multi-phase level diffractive optical gratings is prohibitively difficult. Moreover, bulk or stratified volume holographic approaches appear impractical due to materials limitations at 2 micrometers and the need to maintain adequate wavefront quality. In order to avoid the

  14. Identification of Gas Phase PAHs in Absorption Towards Protostellar Sources

    NASA Technical Reports Server (NTRS)

    Bregman, Jesse D.; Temi, Pasquale; DeVincenzi, Donald L. (Technical Monitor)

    2000-01-01

    The infrared emission bands (also known as the UIR bands.) have recently been observed in absorption at 3.25 micrometers in the ices surrounding a few proto-stellar objects at 11.2 micrometers in MonR2, and at 6.2 micrometers towards two sources near the galactic center. The UIR bands have been observed in emission for many years, but identifying these bands has proven to be both difficult and contentious as no one has yet found a single material that provides a good match to the features. However, most investigators agree that some form of carbon-based material with aromatic bonds is the most likely candidate, and many arguments favor free molecules (polycyclic aromatic hydrocarbons, PAHs) as the carriers of at least the narrow emission bands. Since the emission arises not from a single molecule but from a family of molecules, identifying which PAHs are contributing to the infrared emission bands is difficult. The identification is further complicated by the fact that the emission at short wavelengths is dominated by small molecules while at long wavelengths it is dominated by large molecules. Thus, for example, the emission at 3.3 micrometers is from a different mix of molecules than those which produce the 11.2 micrometer band. To complicate matters further, the molecular mix includes both neutral and ionic species. In absorption, the same mixture of molecules contributes at all wavelengths and the molecules should be neutral, potentially simplifying comparisons with lab data. Also, absorption strengths measured in the lab are directly applicable to interstellar absorption bands without the need to model an emission spectrum of an unknown mixture of ionized and neutral PAHs. In this paper we show that a mixture of argon matrix isolated PAH molecules can reproduce the 3.25 micrometers absorption band seen in the ISO SWS spectra of four embedded Infrared sources, S140 IRS1, AFGL 2591, Elias 29, and AFGL 989. In section 2 we describe the ISO SWS data analysis and

  15. Reflectance and Mossbauer spectroscopy of ferrihydrite-montmorillonite assemblages as Mars soil analog materials

    NASA Technical Reports Server (NTRS)

    Bishop, J. L.; Pieters, C. M.; Burns, R. G.; Chang, S. (Principal Investigator)

    1993-01-01

    Spectroscopic analyses show that Fe(3+)-doped smectites prepared in the laboratory exhibit important similarities to the soils on Mars. Ferrihydrite has been identified as the interlayer ferric component in Fe(3+)-doped smectites by a low quadrupole splitting and magnetic field strength of approximately 48 tesla in Mossbauer spectra measured at 4.2 K, as well as a crystal field transition at 0.92 micrometer. Ferrihydrite in these smectites explains features in the visible-near infrared region that resemble the energies and band strengths of features in reflectance spectra observed for several bright regions on Mars. Clay silicates have met resistance in the past as Mars soil analogs because terrestrial clay silicates exhibit prominent hydrous spectral features at 1.4, 1.9, and 2.2 micrometers; and these are observed weakly, if at all, in reflectance spectra of Mars. However, several mechanisms can weaken or compress these features, including desiccation under low-humidity conditions. The hydration properties of the interlayer cations also effect band strengths, such that a ferrihydrite-bearing smectite in the Martian environment would exhibit a 1.9 micrometers H2O absorption that is even weaker than the 2.2 micrometers structural OH absorption. Mixing experiments demonstrate that infrared spectral features of clays can be significantly suppressed and that the reflectance can be significantly darkened by mixing with only a few percent of a strongly absorbing opaque material. Therefore, the absolute reflectance of a soil on Mars may be disproportionately sensitive to a minor component. For this reason, the shape and position of spectral features and the chemical composition of potential analogs are of utmost importance in assessing the composition of the soil on Mars. Given the remarkable similarity between visible-infrared reflectance spectra of soils in bright regions on Mars and Fe(3+)-doped montmorillonites, coupled with recent observations of smectites in SNC

  16. Development of an advanced mask and its fabrication system

    NASA Astrophysics Data System (ADS)

    Takigawa, Tadahiro; Tojo, Toru; Ogawa, Yoji; Koyama, Kiyomi; Ono, Akira; Inoue, Soichi; Ito, Shinichi; Goto, Mineo

    1995-07-01

    Masks and their fabrication technologies are keys to the further advancement of optical lithography. A stable SiNx single layer attenuated masks for DUV have been developed. A 0.2 micrometers contact hole pattern was fabricated using a KrF stepper with the SiNx attenuated mask. Toshiba mask fabrication system, including an electron beam writing system, a data base inspection system, and a data conversion system, has been developed for 64 Mbit DRAM class. Required mask improvements for increasing optical lithography resolution include better critical dimension (CD) uniformity, higher mask writing system resolution, and automatic shifter patten generation of alternating phase shifting masks. In addition, improved mask pattern positioning accuracy is also required. In this paper, experimental CD uniformity and resolution improvements, automatic phase shifter assignment method, and improvement in positioning accuracy, are described. The future development of masks will incorporate these key technologies.

  17. Nd:YAG laser micromachining of SiC precision structures for MEMS

    NASA Astrophysics Data System (ADS)

    Kreutz, Ernst-Wolfgang; Weichenhain, Ruth; Horn, Alexander

    2001-04-01

    Micromachining of SiC with 1(omega) , 2(omega) , 3(omega) -Nd:YAG laser radiation with pulse durations in the ps to ns regime is performed in various processing gas atmospheres as a function of processing variables showing the influence of the heat and pressure load onto the precision of geometric structures generated. The physical and chemical processes involved in micromachining with laser radiation are characterized by a machine vision system and the produced structures are analyzed by profilometry, optical and electron microscopy as well as X- photoelectron spectroscopy. 3D microstructures are produced by scanning and turning the laser beam onto the material surface, width of structures < 100 micrometers and surface roughness < 2 micrometers , for example, require an overlap < 0.8 independent of the type of processing gas under investigation.

  18. Science support for the atmospheric trace molecule spectroscopy (ATMOS) experiment

    NASA Technical Reports Server (NTRS)

    Rinsland, C. P.

    1982-01-01

    The experiment is a satellite solar occultation interferometer spectrometer experiment under development for flight on Spacelab 3. Launch is expected in March 1985. ATMOS will provide high spectral resolution (0.02/cm) and high spatial resolution (2 km from Shuttle altitude) data over the spectral range from 2 micrometers to 16 micrometers. This region of the spectrum is rich in absorption features of major and minor trace gases which are critical to the understanding of the chemistry and physics of the Earth's upper atmosphere. The broad objectives of the ATMOS experiment are to: identify and measure, on a global scale, the volume mixing ratios of known and newly discovered molecular species; determine vertical profiles for these species; and provide spectral data on the atmosphere for use in optimizing the design of future instruments to monitor specific gases.

  19. Radial Distribution of Electron Spectra from High-Energy Ions

    NASA Technical Reports Server (NTRS)

    Cucinotta, Francis A.; Katz, Robert; Wilson, John W.

    1998-01-01

    The average track model describes the response of physical and biological systems using radial dose distribution as the key physical descriptor. We report on an extension of this model to describe the average distribution of electron spectra as a function of radial distance from an ion. We present calculations of these spectra for ions of identical linear energy transfer (LET), but dissimilar charge and velocity to evaluate the differences in electron spectra from these ions. To illustrate the usefulness of the radial electron spectra for describing effects that are not described by electron dose, we consider the evaluation of the indirect events in microdosimetric distributions for ions. We show that folding our average electron spectra model with experimentally determined frequency distributions for photons or electrons provides a good representation of radial event spectra from high-energy ions in 0.5-2 micrometer sites.

  20. Effect of Lunar Dust Simulant on Human Epithelial Cell Lines

    NASA Technical Reports Server (NTRS)

    Myers, Nicholas J.; Wallace, William T.; Jeevarajan, Antony S.

    2009-01-01

    The purpose of this project is to assess the potential toxicity of lunar dust to cause the release of pro-inflammatory cytokines by human lung cells. Some of this dust is on the scale of 1-2 micrometers and could enter the lungs when astronauts track dust into the habitat and inhale it. This could be a serious problem as NASA plans on going back to the moon for an extended period of time. Literature shows that quartz, which has a known cytoxicity, can cause acute cases of silicosis within 6 months, and in most cases cause silicosis after 3 years. The activation of lunar dust through impacts creates surface based radicals which, upon contact with water create hydroxl radicals and peroxyl radicals which are very reactive and potentially might even be as cytotoxic as quartz. These radicals could then react with lung cells to produce pro-inflammatory mediators such as interleukin-6 and interleukin-8, and TNF-alpha.

  1. Holographic evaluation of the marginal fit of complete crowns loaded at central fossa

    NASA Astrophysics Data System (ADS)

    Chen, Terry Y.; Chang, Guan L.; Wu, Shih H.

    1993-07-01

    In dentistry, the defect of cementation on the margins of crowns accumulates bacterial plaque easily. This can result in recurrent caries and periodontal disease. In this paper holographic interferometry is applied to study the effect of masticatory force on various complete crowns. Four complete molar crowns made from different casting materials (Au, Pd-Ag, Ni-Cr, and PFM) were tested. The horizontal displacements of two points near the margin, measured by the method of multiple observations, could be as large as 15 micrometers under normal load (25 kgw). However, the marginal discrepancy of all four crowns estimated were quite small (< 0.2 micrometers ). This also indicates that the cementation between the crown and the tooth is quite good. Nevertheless, when the load was increased to 45 kgw, a defect of cementation was found on the Pd-Ag crown.

  2. Holographic evaluation of the marginal fits of complete crowns loaded at the central fossa

    NASA Astrophysics Data System (ADS)

    Chen, Terry Y.; Chang, Guan L.; Wu, Shih H.

    1995-05-01

    In dentistry, a defect of cementation on the margins of crowns accumulates bacterial plaque easily. This can result in recurrent caries and periodontal disease. In this paper holographic interferometry was applied to evaluate the effect of masticatory force on various complete crowns. Four complete molar crowns made from different materials (Au alloy, Pd-Ag alloy, Ni-Cr alloy, and porcelain fused to metal) were tested. The out-of-plane displacements of the crown specimens were measured by the method of multiple observations. The displacements measured range from 6 to 10 micrometers under normal load (25 N). However, the marginal openings of all four crowns were estimated to be less than 0.2 micrometers . In addition the defect of the crown was examined.

  3. Identification of oligomerizing peptides.

    PubMed

    Dhiman, A; Rodgers, M E; Schleif, R

    2001-06-08

    The AraC DNA binding domain is inactive in a monomeric form but can activate transcription from the arabinose operon promoters upon its dimerization. We used this property to identify plasmids encoding peptide additions to the AraC DNA binding domain that could dimerize the domain. We generated a high diversity library of plasmids by inserting 90-base oligonucleotides of random sequence ahead of DNA coding for the AraC DNA binding domain in an expression vector, transforming, and selecting colonies containing functional oligomeric peptide-AraC DNA binding domain chimeric proteins by their growth on minimal arabinose medium. Six of seven Ara(+) candidates were partially characterized, and one was purified. Equilibrium analytical centrifugation experiments showed that it dimerizes with a dissociation constant of approximately 2 micrometer.

  4. Amorphous microcellular polytetrafluoroethylene foam film

    NASA Astrophysics Data System (ADS)

    Tang, Chongzheng

    1991-11-01

    We report herein the preparation of novel low-density ultramicrocellular fluorocarbon foams and their application. These fluorocarbon foams are of interest for the biochemistry arena in numerous applications including foodstuff, pharmacy, wine making, beer brewery, fermentation medical laboratory, and other processing factories. All of those require good quality processing programs in which, after eliminating bacterium and virus, compressed air is needed. Ordinarily, compressed air contains bacterium and virus, its size is 0.01 - 2 micrometers fluorocarbon foam films. Having average porous diameter 0.04 - 0.1 micrometers , these are stable to high temperature (280 degree(s)C) and chemical environments, and generally have good engineering and mechanical properties (e.g., low coefficient of thermal expansion, high modulus, and good dimensional stability). Our new process for preparing low density fluorocarbon foams provides materials with unique properties. As such, they offer the possibility for being superior to earlier materials for a number of the filter applications mentioned.

  5. Preliminary results from the viking x-ray fluorescence experiment: The first sample from chryse planitia, Mars

    USGS Publications Warehouse

    Toulmin, P.; Clark, B. C.; Baird, A.K.; Keil, Klaus; Rose, H.J.

    1976-01-01

    Iron, calcium, aluminum, silicon, and sulfur are major elements in the first surface sample of Mars that has been analyzed by the Viking x-ray fluorescence spectrometer. Titanium is present in minor quantities. This is consistent with the sample being a mixture of fine silicate and oxide mineral grains, with a significant proportion of sulfates, possibly hydrated. Ferric oxide is regarded as the red pigmenting agent on the martian surface, but if it coats silicate grains, the coatings must be very thin (??? 2 micrometers) or discontinuous. A high abundance of Fe, relatively low abundances of Al, Rb, Sr, and Zr, and a high Ca/K ratio are distinctive features of the spectra. Preliminary determinations indicate the following abundances (as percentages by weight): Fe, 14 ?? 2; Ti < 1; S, 2 to 5; the Ca/K ratio by weight is greater than 5.

  6. Detection of hydrothermal alteration at Virginia City, Nevada using Airborne Imaging Spectrometry (AIS)

    NASA Technical Reports Server (NTRS)

    Hutsinpiller, A.; Taranik, J. V.

    1986-01-01

    Airborne Imaging Spectrometer (AIS) data were collected over Virginia City, Nevada; an area of gold and silver mineralization with extensive surface exposures of altered volcanic rocks. The data were corrected for atmospheric effects by a flat-field method, and compared to library spectra of various alteration minerals using a spectral analysis program SPAM. Areas of strong clay alteration were identified on the AIS images that were mapped as kaolinitic, illitic, and sericitic alterations zones. Kaolinitic alteration is distinguishable in the 2.1 to 2.4 and 1.2 to 1.5 micrometer wavelength regions. Montmorillonite, illite, and sericite have absorption features similar to each other at 2.2 micrometer wavelength. Montnorillonite and illite also may be present in varying proportions within one Ground Instantaneous Field of View (GIFOV). In general AIS data is useful in identifying alteration zones that are associated with or lie above precious metal mineralization at Virginia City.

  7. Title: Characterizing a Frozen Extrasolar World

    NASA Technical Reports Server (NTRS)

    Skemer, Andrew J.; Morley, Caroline V.; Allers, Katelyn N.; Geballe, Thomas R.; Marley, Mark S.; Fortney, Jonathan J.; Faherty, Jacqueline K.; Bjoraker, Gordon L.

    2016-01-01

    The recently discovered brown dwarf WISE 0855 presents our first opportunity to study an object outside the Solar System that is nearly as cold as our own gas giant planets. However the traditional methodology for characterizing brown dwarfs-near infrared spectroscopy-is not currently feasible as WISE 0855 is too cold and faint. To characterize this frozen extrasolar world we obtained a 4.5-5.2 micrometers spectrum, the same bandpass long used to study Jupiter's deep thermal emission. Our spectrum reveals the presence of atmospheric water vapor and clouds, with an absorption profile that is strikingly similar to Jupiter. The spectrum is high enough quality to allow the investigation of dynamical and chemical processes that have long been studied in Jupiter's atmosphere, but this time on an extrasolar world.

  8. Juneau Airport Doppler Lidar Deployment: Extraction of Accurate Turbulent Wind Statistics

    NASA Technical Reports Server (NTRS)

    Hannon, Stephen M.; Frehlich, Rod; Cornman, Larry; Goodrich, Robert; Norris, Douglas; Williams, John

    1999-01-01

    A 2 micrometer pulsed Doppler lidar was deployed to the Juneau Airport in 1998 to measure turbulence and wind shear in and around the departure and arrival corridors. The primary objective of the measurement program was to demonstrate and evaluate the capability of a pulsed coherent lidar to remotely and unambiguously measure wind turbulence. Lidar measurements were coordinated with flights of an instrumented research aircraft operated by representatives of the University of North Dakota (UND) under the direction of the National Center for Atmospheric Research (NCAR). The data collected is expected to aid both turbulence characterization as well as airborne turbulence detection algorithm development activities within NASA and the FAA. This paper presents a summary of the deployment and results of analysis and simulation which address important issues regarding the measurement requirements for accurate turbulent wind statistics extraction.

  9. Low-coherence in-depth microscopy for biological tissue imaging: design of a real-time control system

    NASA Astrophysics Data System (ADS)

    Blanchot, Loic; Lebec, Martial; Beaurepaire, Emmanuel; Gleyzes, Philippe; Boccara, Albert C.; Saint-Jalmes, Herve

    1998-01-01

    We describe the design of a versatile electronic system performing a lock-in detection in parallel on every pixel of a 2D CCD camera. The system is based on a multiplexed lock- in detection method that requires accurate synchronization of the camera, the excitation signal and the processing computer. This device has been incorporated in an imaging setup based on the optical coherence tomography principle, enabling to acquire a full 2D head-on image without scanning. The imaging experiment is implemented on a modified commercial microscope. Lateral resolution is on the order of 2 micrometers , and the coherence length of the light source defines an axial resolution of approximately 8 micrometers . Images of onion cells a few hundred microns deep into the sample are obtained with 100 dB sensitivity.

  10. Low-coherence in-depth microscopy for biological tissue imaging: design of a real-time control system

    NASA Astrophysics Data System (ADS)

    Blanchot, Loic; Lebec, Martial; Beaurepaire, Emmanuel; Gleyzes, Philippe; Boccara, A. Claude; Saint-Jalmes, Herve

    1997-12-01

    We describe the design of a versatile electronic system performing a lock-in detection in parallel on every pixel of a 2D CCD camera. The system is based on a multiplexed lock- in detection method that requires accurate synchronization of the camera, the excitation signal and the processing computer. This device has been incorporated in an imaging setup based on the optical coherence tomography principle, enabling to acquire a full 2D head-on image without scanning. The imaging experiment is implemented on a modified commercial microscope. Lateral resolution is on the order of 2 micrometers , and the coherence length of the light source defines an axial resolution of approximately 8 micrometers . Images of onion cells a few hundred microns deep into the sample are obtained with 100 dB sensitivity.

  11. Advancement of X-Ray Microscopy Technology and its Application to Metal Solidification Studies

    NASA Technical Reports Server (NTRS)

    Kaukler, William F.; Curreri, Peter A.

    1996-01-01

    The technique of x-ray projection microscopy is being used to view, in real time, the structures and dynamics of the solid-liquid interface during solidification. By employing a hard x-ray source with sub-micron dimensions, resolutions of 2 micrometers can be obtained with magnifications of over 800 X. Specimen growth conditions need to be optimized and the best imaging technologies applied to maintain x-ray image resolution, contrast and sensitivity. It turns out that no single imaging technology offers the best solution and traditional methods like radiographic film cannot be used due to specimen motion (solidification). In addition, a special furnace design is required to permit controlled growth conditions and still offer maximum resolution and image contrast.

  12. Ancient asteroids enriched in refractory inclusions.

    PubMed

    Sunshine, J M; Connolly, H C; McCoy, T J; Bus, S J; La Croix, L M

    2008-04-25

    Calcium- and aluminum-rich inclusions (CAIs) occur in all classes of chondritic meteorites and contain refractory minerals predicted to be the first condensates from the solar nebula. Near-infrared spectra of CAIs have strong 2-micrometer absorptions, attributed to iron oxide-bearing aluminous spinel. Similar absorptions are present in the telescopic spectra of several asteroids; modeling indicates that these contain approximately 30 +/- 10% CAIs (two to three times that of any meteorite). Survival of these undifferentiated, large (50- to 100-kilometer diameter) CAI-rich bodies suggests that they may have formed before the injection of radiogenic 26Al into the solar system. They have also experienced only modest post-accretionary alteration. Thus, these asteroids have higher concentrations of CAI material, appear less altered, and are more ancient than any known sample in our meteorite collection, making them prime candidates for sample return.

  13. Effects of fine porosity on the fatigue behavior of a powder metallurgy superalloy

    NASA Technical Reports Server (NTRS)

    Miner, R. V., Jr.; Dreshfield, R. L.

    1980-01-01

    Hot isostatically pressed powder metallurgy Astroloy was obtained which contained 1.4 percent fine porosity at the grain boundaries produced by argon entering the powder container during pressing. This material was tested at 650 C in fatigue, creep fatigue, tension, and stress-rupture and the results compared with previous data on sound Astroloy. The pores averaged about 2 micrometers diameter and 20 micrometers spacing. They did influence fatigue crack initiation and produced a more intergranular mode of propagation. However, fatigue life was not drastically reduced. A large 25 micrometers pore in one specimen resulting from a hollow particle did not reduce life by 60 percent. Fatigue behavior of the porous material showed typical correlation with tensile behavior. The plastic strain range life relation was reduced proportionately with the reduction in tensile ductility, but the elastic strain range-life relation was little changed reflecting the small reduction in sigma sub u/E for the porous material.

  14. NIMS Radiance Point Spectra of Gaspra V1.0

    NASA Astrophysics Data System (ADS)

    Granahan, J. C.

    2014-10-01

    This data volume contains radiometrically corrected point spectra of asteroid 951 as acquired by the Galileo spacecraft Near Infrared Mapping Spectrometer (NIMS) on October 29, 1991. They record the spectra collected as the Galileo spacecraft approached the target asteroid. These data are products of the calibration of the raw data number files gap015tn.qub, gap035tn.qub, gap036tn.qub, gap037tn.qub, and gap038tn.qub (DATA SET ID ='GO-A-NIMS-3 TUBE-V1.0') with calibration factors acquired during the first Earth/Moon encounter of the Galileo mission. These raw data .qub files are archived in the Imaging Node of the NASA Planetary Data System (PDS). The calibrated spectra consist of radiance measurements for wavelengths between 0.7 - 5.2 micrometers.

  15. Radiobiological results from the Bacillus subtilis Biostack experiments within the Apollo and the ASTP space flights.

    PubMed

    Facius, R; Bucker, H; Hildebrand, D; Horneck, G; Holtz, G; Reitz, G; Schafer, M; Toth, B

    1978-01-01

    In order to check the results of earlier Biostack experiments, new experimental techniques were developed for the Biostack III experiment in the Apollo-Soyuz test project (ASTP). These techniques resulted in an increased accuracy of localization down to 0.2 micrometers for the determination of the impact parameter, accompanied by an increase in the sample size available for biological investigation. In addition, colony forming ability, metabolic mutations, and mutations affecting UV- and x-ray sensitivity were rendered observable by these methods. The biological and physical results obtained so far from the evaluation of the Bacillus subtilis experiment within Biostack III confirm and extend the findings of the previous Biostack experiments. They also add to the questions about the mechanisms of action of the radiation field under investigation, since the observed effects cannot be interpreted in terms of standard concepts.

  16. Galaxy Evolution Spectroscopic Explorer (GESE): Science Rationale, Optical Design, and Telescope Architecture

    NASA Technical Reports Server (NTRS)

    Heap, Sara R.; Gong, Qian; Hull, Tony; Purves, Lloyd

    2014-01-01

    One of the key goals of NASA’s astrophysics program is to answer the question: How did galaxies evolve into the spiral, elliptical, and irregular galaxies that we see today? We describe a space mission concept called Galaxy Evolution Spectroscopic Explorer (GESE) to help address this question by making a large ultraviolet spectroscopic survey of galaxies at a redshift, z approximately 1 (look-back time of approximately 8 billion years). GESE is a 1.5-m space telescope with an near-ultraviolet (NUV) multi-object slit spectrograph covering the spectral range, 0.2-0.4 micrometers (0.1-0.2 micrometers as emitted by galaxies at a redshift, z approximately 1) at a spectral resolution of delta lambda=6 A.

  17. A histochemical study of protein-bound SH and SS in chromosomes of hyacinth and fava bean root tips.

    PubMed

    Wiese, D A

    1980-01-01

    Root tips were fixed in ethanol-acetic acid and in neutral formalin containing a mercaptide-forming agent to protect thiols from autoxidation. Serial paraffin sections 2 micrometers thick were labelled for thiols, disulfides and both together with the azogenic maleimide 'APM'. Nuclei were stained somewhat lighter for thiols, and nucleoli much darker, than was the surrounding cytoplasm; disulfide staining was paler and more evenly distributed. However, regardless of the fixative employed, mitotic chromosomes (precisely localized by fluorescent Feulgen counterstaining) contained negligible amounts of either thiols or disulfides. Although published biochemical studies also have indicated low concentrations of cyst(e)inyl residues in chromosomal proteins, the present findings contradict most previous histochemical reports.

  18. Complementary Barrier Infrared Detector (CBIRD) with Double Tunnel Junction Contact and Quantum Dot Barrier Infrared Detector (QD-BIRD)

    NASA Technical Reports Server (NTRS)

    Ting, David Z.-Y; Soibel, Alexander; Khoshakhlagh, Arezou; Keo, Sam A.; Nguyen, Jean; Hoglund, Linda; Mumolo, Jason M.; Liu, John K.; Rafol, Sir B.; Hill, Cory J.; Gunapala, Sarath D.

    2012-01-01

    The InAs/GaSb type-II superlattice based complementary barrier infrared detector (CBIRD) has already demonstrated very good performance in long-wavelength infrared (LWIR) detection. In this work, we describe results on a modified CBIRD device that incorporates a double tunnel junction contact designed for robust device and focal plane array processing. The new device also exhibited reduced turn-on voltage. We also report results on the quantum dot barrier infrared detector (QD-BIRD). By incorporating self-assembled InSb quantum dots into the InAsSb absorber of the standard nBn detector structure, the QD-BIRD extend the detector cutoff wavelength from approximately 4.2 micrometers to 6 micrometers, allowing the coverage of the mid-wavelength infrared (MWIR) transmission window. The device has been observed to show infrared response at 225 K.

  19. Recent patents on electrophoretic displays and materials.

    PubMed

    Christophersen, Marc; Phlips, Bernard F

    2010-11-01

    Electrophoretic displays (EPDs) have made their way into consumer products. EPDs enable displays that offer the look and form of a printed page, often called "electronic paper". We will review recent apparatus and method patents for EPD devices and their fabrication. A brief introduction into the basic display operation and history of EPDs is given, while pointing out the technological challenges and difficulties for inventors. Recently, the majority of scientific publications and patenting activity has been directed to micro-segmented EPDs. These devices exhibit high optical reflectance and contrast, wide viewing angle, and high image resolution. Micro-segmented EPDs can also be integrated with flexible transistors technologies into flexible displays. Typical particles size ranges from 200 nm to 2 micrometer. Currently one very active area of patenting is the development of full-color EPDs. We summarize the recent patenting activity for EPDs and provide comments on perceiving factors driving intellectual property protection for EPD technologies.

  20. Organization of the topical meeting on tunable solid-state lasers. Held in North Falmouth, Massachusetts on May 1-3 1989. Final report, 30 August 1988-30 August 1989

    SciTech Connect

    Not Available

    1989-08-30

    Progress and interest in solid-state lasers generally, and in tunable solid state-lasers specifically, continues to expand. Applications of these lasers include spectroscopy, remote sensing, ranging and imaging, and medicine. New solid-state materials are providing lasers with higher output power, broader tunability, and more-efficient pumping schemes. The quantum electronics and crystal-chemistry properties of these new materials are leading to enhanced laser performance. At the meeting, sessions were held on sapphire, novel laser schemes, Cr lasers, forsterite and excited-state absorption, solid-state lasers for specialized applications, alexandrite lasers, Cr-related issues, diode pumped lasers, nonlinear frequency conversion, 1.3-micrometer Nd lasers, infrared lasers and energy transfer, 2-micrometer lasers, rare earth laser materials, and Er lasers.

  1. Improved performance of the laser guide star adaptive optics system at Lick Observatory

    NASA Astrophysics Data System (ADS)

    Olivier, Scot S.; Gavel, Donald T.; Friedman, Herbert W.; Max, Claire E.; An, Jong R.; Avicola, Kenneth; Bauman, Brian J.; Brase, James M.; Campbell, Eugene W.; Carrano, Carmen J.; Cooke, Jeffrey B.; Freeze, Gary J.; Gates, Elinor L.; Kanz, Vernon K.; Kuklo, Thomas C.; Macintosh, Bruce A.; Newman, Michael J.; Pierce, Edward L.; Waltjen, Kenneth E.; Watson, James A.

    1999-09-01

    Results of experiments with the laser guide star adaptive optics system on the 3-meter Shane telescope at Lick Observatory have demonstrated a factor of 4 performance improvement over previous results. Stellar images recorded at a wavelength of 2 micrometers were corrected to over 40 percent of the theoretical diffraction-limited peak intensity. For the previous two years, this sodium-layer laser guide star system has corrected stellar images at this wavelength to approximately 10 percent of the theoretical peak intensity limit. After a campaign to improve the beam quality of the laser system, and to improve calibration accuracy and stability of the adaptive optics system using new techniques for phase retrieval and phase-shifting diffraction interferometry, the system performance has been substantially increased. The next step will be to use the Lick system for astronomical science observations, and to demonstrate this level of performance with the new system being installed on the 10-meter Keck II telescope.

  2. Design of a Low-Light-Level Image Sensor with On-Chip Sigma-Delta Analog-to- Digital Conversion

    NASA Technical Reports Server (NTRS)

    Mendis, Sunetra K.; Pain, Bedabrata; Nixon, Robert H.; Fossum, Eric R.

    1993-01-01

    The design and projected performance of a low-light-level active-pixel-sensor (APS) chip with semi-parallel analog-to-digital (A/D) conversion is presented. The individual elements have been fabricated and tested using MOSIS* 2 micrometer CMOS technology, although the integrated system has not yet been fabricated. The imager consists of a 128 x 128 array of active pixels at a 50 micrometer pitch. Each column of pixels shares a 10-bit A/D converter based on first-order oversampled sigma-delta (Sigma-Delta) modulation. The 10-bit outputs of each converter are multiplexed and read out through a single set of outputs. A semi-parallel architecture is chosen to achieve 30 frames/second operation even at low light levels. The sensor is designed for less than 12 e^- rms noise performance.

  3. Infrared observations of the galactic center. I - Nature of the compact sources

    NASA Technical Reports Server (NTRS)

    Becklin, E. E.; Matthews, K.; Neugebauer, G.; Willner, S. P.

    1978-01-01

    Photometry from 1.25 to 12 micrometers and spectrophotometry from 8 to 13 micrometers of the compact sources found in the galactic-center region are reported. In addition, revised 10 and new 20 micrometers maps with 2''.3 resolution are given. The nature of the compact sources is discussed. Some are best identified as stars or star clusters; the brightest source at 2 micrometers is probably a supergiant, and the infrared source near the nonthermal radio source is probably a stellar cluster with density greater than 1 million solar masses/cu pc. Other sources emit most of their luminosity at wavelengths of 10 micrometers and greater; this emission is probably from heated dust. One of the sources is observationally similar to extremely red OH/infrared stars. Other sources have luminosities and linear sizes similar to those of compact H II regions; emission from optically thin silicate dust is seen in these.

  4. Development of a laser wind and hazard profiler

    NASA Astrophysics Data System (ADS)

    Rouse, Gordon F.; Bagley, Harold R.; Kane, Thomas J.; Leung, Christopher

    1996-10-01

    This paper describes present day wind-measuring and air-data systems, the limitations of these systems, and the formation of a consortium to develop solutions using the laser Doppler velocimeter (LDV). The LDV concept is discussed as well as the issues related to developing such systems. Significant progress towards making practical, reliable, and affordable eye-safe LDV systems is being gained through the many systems built to date and flight tests. The technical goal of this program is to demonstrate that small, low-power, diode pumped, 2 micrometers wavelength, eye-safe coherent LDV systems can be built and flown on both high-performance military fighter aircraft and advanced military attack helicopters. An industry-government consortium will develop LDV systems with the name Laser Wind and Hazard Profiler.

  5. High Energy Directly Pumped Ho:YLF Laser

    NASA Technical Reports Server (NTRS)

    Petros, Mulugeta; Yu, Ji-Rong; Singh, Upendra N.; Barnes, Norman P.

    2000-01-01

    The most commonly used crystal architecture to produce 2 micrometer laser is co-doping Ho and Tm into a single host crystal. In this method, the stored energy transfer from the Tm (3)F4 to the Ho (5)I7 manifold is not fast enough to warrant high efficiency for short pulse applications. By separating the Ho and the Tm ions and doping the Tm in YALO3 and the Ho in YLF, we were able to directly pump the Ho (5)I7 manifold with 1.94 micrometers. The Ho:YLF laser has produced 33 mJ at 2.062 micrometers with a quantum efficiency of 0.88. The performance of each laser will be presented.

  6. Evaluation of LANDSAT MSS vs TM simulated data for distinguishing hydrothermal alteration

    NASA Technical Reports Server (NTRS)

    Abrams, M. J.; Kahle, A. B.; Madura, D. P.; Soha, J. M.

    1978-01-01

    The LANDSAT Follow-On (LFO) data was simulated to demonstrate the mineral exploration capability of this system for segregating different types of hydrothermal alteration and to compare this capability with that of the existing LANDSAT system. Multispectral data were acquired for several test sites with the Bendix 24-channel MSDS scanner. Contrast enhancements, band ratioing, and principal component transformations were used to process the simulated LFO data for analysis. For Red Mountain, Arizona, the LFO data allowed identification of silicified areas, not identifiable with LANDSAT 1 and 2 data. The improved LFO resolution allowed detection of small silicic outcrops and of a narrow silicified dike. For Cuprite - Ralston, Nevada, the LFO spectral bands allowed discrimination of argillic and opalized altered areas; these could not be spectrally discriminated using LANDSAT 1 and 2 data. Addition of data from the 1.3- and 2.2- micrometer regions allowed better discriminations of hydrothermal alteration types.

  7. Low cost optical tweezers systems using double coil driving stepping motor to controlling sample stage

    NASA Astrophysics Data System (ADS)

    Laowattanatham, N.; Cheamanunkul, N.; Plaipichit, S.; Buranasiri, P.; Nuansri, R.

    2013-06-01

    In this research, the low cost optical tweezers systems using X-Y stage has been developed by using 5-phase stepping motor. By using sequential double coil driving, we can obtain the driving torque larger than using the single coil driving. The moving scale is fine resolution at 0.2 micrometer. The overall systems based on microcontroller PIC18F458 and joystick controller with LabView® graphical user interface (GUI). The mechanical damping has been included in the system for decreasing the vibrational noise. By using this method, our optical tweezers system is cheaper than the other commercial system that has been used the piezoelectric driving, and still has the same efficiency.

  8. Calculating Second-Order Effects in MOSFET's

    NASA Technical Reports Server (NTRS)

    Benumof, Reuben; Zoutendyk, John A.; Coss, James R.

    1990-01-01

    Collection of mathematical models includes second-order effects in n-channel, enhancement-mode, metal-oxide-semiconductor field-effect transistors (MOSFET's). When dimensions of circuit elements relatively large, effects neglected safely. However, as very-large-scale integration of microelectronic circuits leads to MOSFET's shorter or narrower than 2 micrometer, effects become significant in design and operation. Such computer programs as widely-used "Simulation Program With Integrated Circuit Emphasis, Version 2" (SPICE 2) include many of these effects. In second-order models of n-channel, enhancement-mode MOSFET, first-order gate-depletion region diminished by triangular-cross-section deletions on end and augmented by circular-wedge-cross-section bulges on sides.

  9. Characteristics of III-V Semiconductor Devices at High Temperature

    NASA Technical Reports Server (NTRS)

    Simons, Rainee N.; Young, Paul G.; Taub, Susan R.; Alterovitz, Samuel A.

    1994-01-01

    This paper presents the development of III-V based pseudomorphic high electron mobility transistors (PHEMT's) designed to operate over the temperature range 77 to 473 K (-196 to 200 C). These devices have a pseudomorphic undoped InGaAs channel that is sandwiched between an AlGaAs spacer and a buffer layer; gate widths of 200, 400, 1600, and 3200 micrometers; and a gate length of 2 micrometers. Measurements were performed at both room temperature and 473 K (200 C) and show that the drain current decreases by 30 percent and the gate current increases to about 9 microns A (at a reverse bias of -1.5 V) at the higher temperature. These devices have a maximum DC power dissipation of about 4.5 W and a breakdown voltage of about 16 V.

  10. Oxygen-isotope, X-ray-diffraction and scanning-electron-microscope examinations of authigenic-layer-silicate minerals from Mississippian and Pennsylvanian sandstones in the Michigan Basin

    USGS Publications Warehouse

    Zacharias, K.F.; Sibley, D.F.; Westjohn, D.B.; Weaver, T. L.

    1993-01-01

    Oxygen-isotope compositions of authigenic-layer silicates (<2-micrometer fraction) extracted from Mississippian and Pennsylvanian sandstones in the Lower Peninsula of Michigan were determined. Petrographic and scanning-electron-microscope examinations, and X-ray diffractograms show that chlorite and kaolinite are the most common authigenic-layer silicates in Mississippian sandstones. The range of oxygen-isotope compositions of chlorite and kaolinite are +10.3 to +11.9 and +12.9 to +19.3 pars per thousand (per mil) (relative to Standard Mean Ocean Water), respectively. Kaolinite is the only authigenic-isotopic compositions of kaolinite range from +16.8 to +19.0 per mil.

  11. Active-Pixel Image Sensor With Analog-To-Digital Converters

    NASA Technical Reports Server (NTRS)

    Fossum, Eric R.; Mendis, Sunetra K.; Pain, Bedabrata; Nixon, Robert H.

    1995-01-01

    Proposed single-chip integrated-circuit image sensor contains 128 x 128 array of active pixel sensors at 50-micrometer pitch. Output terminals of all pixels in each given column connected to analog-to-digital (A/D) converter located at bottom of column. Pixels scanned in semiparallel fashion, one row at time; during time allocated to scanning row, outputs of all active pixel sensors in row fed to respective A/D converters. Design of chip based on complementary metal oxide semiconductor (CMOS) technology, and individual circuit elements fabricated according to 2-micrometer CMOS design rules. Active pixel sensors designed to operate at video rate of 30 frames/second, even at low light levels. A/D scheme based on first-order Sigma-Delta modulation.

  12. Determination of Scattering and Absorption Coefficients for Plasma-Sprayed Yttria-Stabilized Zirconia Thermal Barrier Coatings at Elevated Temperatures

    NASA Technical Reports Server (NTRS)

    Eldridge, Jeffrey I.; Spuckler, Charles M.; Markham, James R.

    2009-01-01

    The temperature dependence of the scattering and absorption coefficients for a set of freestanding plasma-sprayed 8 wt% yttria-stabilized zirconia (8YSZ) thermal barrier coatings (TBCs) was determined at temperatures up to 1360 C in a wavelength range from 1.2 micrometers up to the 8YSZ absorption edge. The scattering and absorption coefficients were determined by fitting the directional-hemispherical reflectance and transmittance values calculated by a four-flux Kubelka Munk method to the experimentally measured hemispherical-directional reflectance and transmittance values obtained for five 8YSZ thicknesses. The scattering coefficient exhibited a continuous decrease with increasing wavelength and showed no significant temperature dependence. The scattering is primarily attributed to the relatively temperature-insensitive refractive index mismatch between the 8YSZ and its internal voids. The absorption coefficient was very low (less than 1 per centimeter) at wavelengths between 2 micrometers and the absorption edge and showed a definite temperature dependence that consisted of a shift of the absorption edge to shorter wavelengths and an increase in the weak absorption below the absorption edge with increasing temperature. The shift in the absorption edge with temperature is attributed to strongly temperature-dependent multiphonon absorption. While TBC hemispherical transmittance beyond the absorption edge can be predicted by a simple exponential decrease with thickness, below the absorption edge, typical TBC thicknesses are well below the thickness range where a simple exponential decrease in hemispherical transmittance with TBC thickness is expected. [Correction added after online publication August 11, 2009: "edge to a shorter wavelengths" has been updated as edge to shorter wavelengths."

  13. Phototransistors Development and their Applications to Lidar

    NASA Technical Reports Server (NTRS)

    Abedin, M. N.; Refaat, Tamer F.; Ismail, Syed; Singh, Upendra N.

    2007-01-01

    Custom-designed two-micron phototransistors have been developed using Liquid Phase Epitaxy (LPE), Molecular Beam Epitaxy (MBE) and Metal-Organic Chemical Vapor Deposition (MOCVD) techniques under Laser Risk Reduction Program (LRRP). The devices were characterized in the Detector Characterization Laboratory at NASA Langley Research Center. It appears that the performance of LPE- and MBE-grown phototransistors such as responsivity, noise-equivalent-power, and gain, are better than MOCVD-grown devices. Lidar tests have been conducted using LPE and MBE devices under the 2-micrometer CO2 Differential Absorption Lidar (DIAL) Instrument Incubator Program (IIP) at the National Center for Atmospheric Research (NCAR), Boulder, Colorado. The main focus of these tests was to examine the phototransistors performances as compared to commercial InGaAs avalanche photodiode by integrating them into the Raman-shifted Eye-safe Aerosol Lidar (REAL) operating at 1.543 micrometers. A simultaneous measurement of the atmospheric backscatter signals using the LPE phototransistors and the commercial APD demonstrated good agreement between these two devices. On the other hand, simultaneous detection of lidar backscatter signals using MBE-grown phototransistor and InGaAs APD, showed a general agreement between these two devices with a lower performance than LPE devices. These custom-built phototransistors were optimized for detection around 2-micrometer wavelength while the lidar tests were performed at 1.543 micrometers. Phototransistor operation at 2-micron will improve the performance of a lidar system operating at that wavelength. Measurements include detecting hard targets (Rocky Mountains), atmospheric structure consisting of cirrus clouds and boundary layer. These phototransistors may have potential for high sensitivity differential absorption lidar measurements of carbon dioxide and water vapor at 2.05-micrometers and 1.9-micrometers, respectively.

  14. Determining size-specific emission factors for environmental tobacco smoke particles

    SciTech Connect

    Klepeis, Neil E.; Apte, Michael G.; Gundel, Lara A.; Sextro, Richard G.; Nazaroff, William W.

    2002-07-07

    Because size is a major controlling factor for indoor airborne particle behavior, human particle exposure assessments will benefit from improved knowledge of size-specific particle emissions. We report a method of inferring size-specific mass emission factors for indoor sources that makes use of an indoor aerosol dynamics model, measured particle concentration time series data, and an optimization routine. This approach provides--in addition to estimates of the emissions size distribution and integrated emission factors--estimates of deposition rate, an enhanced understanding of particle dynamics, and information about model performance. We applied the method to size-specific environmental tobacco smoke (ETS) particle concentrations measured every minute with an 8-channel optical particle counter (PMS-LASAIR; 0.1-2+ micrometer diameters) and every 10 or 30 min with a 34-channel differential mobility particle sizer (TSI-DMPS; 0.01-1+ micrometer diameters) after a single cigarette or cigar was machine-smoked inside a low air-exchange-rate 20 m{sup 3} chamber. The aerosol dynamics model provided good fits to observed concentrations when using optimized values of mass emission rate and deposition rate for each particle size range as input. Small discrepancies observed in the first 1-2 hours after smoking are likely due to the effect of particle evaporation, a process neglected by the model. Size-specific ETS particle emission factors were fit with log-normal distributions, yielding an average mass median diameter of 0.2 micrometers and an average geometric standard deviation of 2.3 with no systematic differences between cigars and cigarettes. The equivalent total particle emission rate, obtained integrating each size distribution, was 0.2-0.7 mg/min for cigars and 0.7-0.9 mg/min for cigarettes.

  15. Infrared Spectral Signatures For Io's Dark Spots

    NASA Astrophysics Data System (ADS)

    Granahan, J. C.; Sweet, J.; Fanale, F. P.; Carlson, R. W.; Smythe, W. D.; Galileo NIMS Team; Galileo SSI Team

    2000-10-01

    A variety of indicators for silicate volcanism on Io have been observed by the Galileo spacecraft. These include high temperature volcanism ([1] McEwen et al., 2000 and [2] Lopes-Gautier et al., 2000) of up to 1700 K, a 0.9 micrometer absorption present in many dark (and relatively recent) lava flows ([3] Geissler et al., 1999), and large scale releif in f the form of mountains ([4] Turtle et al., 2000). The 0.9 micrometer feature can be interpreted as absorption feature due to pyroxene. This detection was accomplished via the Galileo SSI (Solid State Imager) camera system which utilizes a set of up to 8 discrete filters to sample the wavelength range from 0.4-1.0 micrometers. Orthopyroxene has an absorption feature around 2.0 micrometers. Our study seeks to analyze the infrared signatures that correlate to this 0.9 micrometer feature. The Galileo Near Infrared Mapping Spectrometer (NIMS) collects data from 0.7-5.2 micrometers with up to 408 bands during the nominal mission and with 12 bands during the current mission. Initial results indicate that these dark features appear to have lower concentrations of sulfur dioxide than surrounding surfaces and do not directly correlate to the 1.2 micrometer absorption feature found by NIMS on Io. Although not detected in our initial NIMS spectral survey, we are modeling spectral mixtures to determine the maximum amount of orthopyroxene that can be present in the NIMS observations. [1 & 2] EOS, Trans, Vol. 81, No. 19, Supplement, S288, [3] Icarus, 140, 265, [4] EOS, Trans, Vol. 81, No. 19, Supplement, S289.

  16. Voltage-dependent and calcium-dependent inactivation of calcium channel current in identified snail neurones.

    PubMed Central

    Gutnick, M J; Lux, H D; Swandulla, D; Zucker, H

    1989-01-01

    1. The dependence of Ca2+ current inactivation on membrane potential and intracellular Ca2+ concentration ([Ca2+]i) was studied in TEA-loaded, identified Helix neurones which possess a single population of high-voltage-activated Ca2+ channels. During prolonged depolarization, the Ca2+ current declined from its peak with two clearly distinct phases. The time course of its decay was readily fitted by a double-exponential function. 2. In double-pulse experiments, the relationship between the magnitude of the Ca2+ current and the amount of Ca2+ inactivation was not linear, and considerable inactivation was present, even when conditioning pulses were to levels of depolarization so great that Ca2+ currents were near zero. Similar results were obtained when external Ca2+ was replaced by Ba2+. 3. In double-pulse experiments, hyperpolarization during the interpulse interval served to reprime a portion of the inactivated Ca2+ current for subsequent activation. The extent of repriming increased with hyperpolarization, reaching a maximum between -130 and -150 mV. The effectiveness of repriming hyperpolarizations was considerably increased when Ca2+ was replaced by Ba2+. 4. A significant fraction of inactivated Ca2+ channels can be recovered during hyperpolarizing pulses lasting only milliseconds. If hyperpolarizing pulses were applied before substantial inactivation of Ca2+ current, Ca2+ channels remained available for activation despite considerable Ca2+ entry. 5. The relationship between [Ca2+]i and inactivation was investigated by quantitatively injecting Ca2+-buffered solutions into the cells. The time course of Ca2+ current inactivation was unchanged at free [Ca2+] between 1 x 10(-7) and 1 x 10(-5) M. From 1 x 10(-7) to 1 x 10(-9) M, inactivation became progressively slower, mainly due to a decrease of the amplitude ratio (fast/slow) of the two components of inactivation, which fell from about unity to near zero at 1 x 10(-9) M. In double-pulse experiments, recovery from

  17. A Novel High Efficient Laser Transmitter Design for a Space-borne Ozone Differential Lidar (DIAL)

    NASA Technical Reports Server (NTRS)

    Edwards, W. C.; Chen, S.; Petway, L. B.; Marsh, W. D.; Storm, M. E.; Barnes, J. C.

    2000-01-01

    Development of a UV laser transmitter capable of operating from a space platform is a critical step in enabling global earth observations of aerosols and ozone at resolutions greater than current passive instrument capabilities. Tropospheric chemistry is well recognized as the next frontier for global atmospheric measurement. NASA Langley Research Center (LaRC) and the Canadian Space Agency (CSA) have jointly studied the requirements for a satellite based, global ozone monitoring instrument. The study, called Ozone Research using Advanced Cooperative Lidar Experiment (ORACLE) has defined the Differential Absorption Lidar (DIAL) instrument performance, weight and power, and configuration requirements for a space based measurement. In order to achieve the measurement resolution and acceptable signal-to-noise from lidar returns, 500mJ/pulse (5 Watts average power) is required at both 305-308nm and 315-320nm wavelengths. These are consecutive pulses, in a 10 Hz, double-pulsed format. The two wavelengths are used as the on- and off-lines for the ozone DIAL measurement. NASA Langley is currently developing technology for a UV laser transmitter capable of meeting the ORACLE requirements. Experimental efforts to date have shown that the UV generation scheme is viable, and that energies greater than l00mJ/pulse are possible. In this paper, we will briefly discuss the down select process for the proposed laser design, the study effort to date and the laser system design, including both primary and alternate approaches. We will describe UV laser technology that minimizes the total number of optical components (for enhanced reliability) as well as the number of UV coated optics required to transmit the light from the laser (for enhanced optical damage resistance). While the goal is to develop a laser that will produce 500 mJ of energy, we will describe an optional design that will produce output energies between 100 - 200 mJ/unit and techniques for combining multiple laser

  18. Modeling-independent elucidation of inactivation pathways in recombinant and native A-type Kv channels.

    PubMed

    Fineberg, Jeffrey D; Ritter, David M; Covarrubias, Manuel

    2012-11-01

    A-type voltage-gated K(+) (Kv) channels self-regulate their activity by inactivating directly from the open state (open-state inactivation [OSI]) or by inactivating before they open (closed-state inactivation [CSI]). To determine the inactivation pathways, it is often necessary to apply several pulse protocols, pore blockers, single-channel recording, and kinetic modeling. However, intrinsic hurdles may preclude the standardized application of these methods. Here, we implemented a simple method inspired by earlier studies of Na(+) channels to analyze macroscopic inactivation and conclusively deduce the pathways of inactivation of recombinant and native A-type Kv channels. We investigated two distinct A-type Kv channels expressed heterologously (Kv3.4 and Kv4.2 with accessory subunits) and their native counterparts in dorsal root ganglion and cerebellar granule neurons. This approach applies two conventional pulse protocols to examine inactivation induced by (a) a simple step (single-pulse inactivation) and (b) a conditioning step (double-pulse inactivation). Consistent with OSI, the rate of Kv3.4 inactivation (i.e., the negative first derivative of double-pulse inactivation) precisely superimposes on the profile of the Kv3.4 current evoked by a single pulse because the channels must open to inactivate. In contrast, the rate of Kv4.2 inactivation is asynchronous, already changing at earlier times relative to the profile of the Kv4.2 current evoked by a single pulse. Thus, Kv4.2 inactivation occurs uncoupled from channel opening, indicating CSI. Furthermore, the inactivation time constant versus voltage relation of Kv3.4 decreases monotonically with depolarization and levels off, whereas that of Kv4.2 exhibits a J-shape profile. We also manipulated the inactivation phenotype by changing the subunit composition and show how CSI and CSI combined with OSI might affect spiking properties in a full computational model of the hippocampal CA1 neuron. This work unambiguously

  19. Aero-Optical Turbulent Boundary Layer/Shear Layer Experiment On The KC-135 Aircraft Revisited

    NASA Astrophysics Data System (ADS)

    Craig, James E.; Allen, C.

    1985-06-01

    This paper examines the aero-optical effects associated with propagating a laser beam through both an aircraft turbulent boundary layer and artificially generated shear layers. The data present comparisons of observed optical performances with those inferred from aerodynamic measurements of unsteady density and correlation lengths within the same random flow fields. Using optical instrumentation with tens of microseconds temporal resolution through a finite aperture, optical performance degradation was determined and contrasted with the infinite-aperture, time-averaged aerodynamic measurement. In addition, the optical data were artificially clipped to compare to theoretical scaling calculations. Optical instrumentation consisted of a custom Q-switched Nd:YAG double-pulsed laser and a holographic camera that recorded the random flow field in a double-pass, double-pulse mode. Aero-dynamic parameters were measured using hot film anemometer probes and a five-hole pressure probe. Each technique is described with its associated theo-retical basis for comparison. The effects of finite aperture and spatial and temporal frequencies of the random flow are considered. The results presented represent five flights flown at altitudes from 1.8 km to 10.7 km and at Mach numbers from 0.32 to 0.79. Single-pass phase deviations for the boundary layer were from 0.06 to 0.17 waves (at X = 0.53 ;Am) with piston and tilt components removed. Measured phase deviations for the artificially induced shear flows were from 0.10 to 0.279 waves (at X = 0.53 /um) with piston and tilt components removed. However, when low order aberrations through coma were removed, the remaining deviations were only 0.09 to 0.18 waves. This resulted in a 33 to 250% increase in the Strehl ratio at the 14 cm optical aperture. It was further shown that the low order aberrations corresponded to the longer wavelengths in the random flow, and these waves propagated with a longer characteristic time than the higher order

  20. Action potential propagation through embryonic dorsal root ganglion cells in culture. II. Decrease of conduction reliability during repetitive stimulation.

    PubMed

    Lüscher, C; Streit, J; Lipp, P; Lüscher, H R

    1994-08-01

    1. The reliability of the propagation of action potentials (AP) through dorsal root ganglion (DRG) cells in embryonic slice cultures was investigated during repetitive stimulation at 1-20 Hz. Membrane potentials of DRG cells were recorded intracellularly while the axons were stimulated by an extracellular electrode. 2. In analogy to the double-pulse experiments reported previously, either one or two types of propagation failures were recorded during repetitive stimulation, depending on the cell morphology. In contrast to the double-pulse experiments, the failures appeared at longer interpulse intervals and usually only after several tens of stimuli with reliable propagation. 3. In the period with reliable propagation before the failures, a decrease in the conduction velocity and in the amplitude of the afterhyperpolarization (AHP), an increase in the total membrane conductance, and the disappearance of the action potential "shoulder" were observed. 4. The reliability of conduction during repetitive stimulation was improved by lowering the extracellular calcium concentration or by replacing the extracellular calcium by strontium. The reliability of conduction decreased by the application of cadmium, a calcium channel blocker, 4-amino pyridine, a fast potassium channel blocker, or apamin or muscarine, the blockers of calcium-dependent potassium channels. The reliability of conduction was not effected by blocking the sodium potassium pump with ouabain or by replacing extracellular sodium with lithium. 5. In the period with reliable propagation cadmium, apamin, and muscarine reduced the amplitude of the AHP. The shoulder of the action potential was more pronounced and not sensitive to repetitive stimulation when extracellular calcium was replaced by strontium. It disappeared when cadmium was applied. 6. In DRG somata changes of the intracellular Ca2+ concentration were monitored by measuring the fluorescence of the Ca2+ indicator Fluo-3 with a laser-scanning confocal

  1. Development of Double and Triple-Pulsed 2-micron IPDA Lidars for Column CO2 Measurements

    NASA Technical Reports Server (NTRS)

    Singh, Upendra N.; Yu, Jirong; Petros, Mulugeta; Refaat, Tamer F.; Remus, Ruben G.; Reithmaier, Karl

    2015-01-01

    Carbon dioxide (CO2) is an important greenhouse gas that significantly contributes to the carbon cycle and globalradiation budget on Earth. CO2 role on Earth’s climate is complicated due to different interactions with various climatecomponents that include the atmosphere, the biosphere and the hydrosphere. Although extensive worldwide efforts formonitoring atmospheric CO2 through various techniques, including in-situ and passive sensors, are taking place highuncertainties exist in quantifying CO2 sources and sinks. These uncertainties are mainly due to insufficient spatial andtemporal mapping of the gas. Therefore it is required to have more rapid and accurate CO2 monitoring with higheruniform coverage and higher resolution. CO2 DIAL operating in the 2-µm band offer better near-surface CO2measurement sensitivity due to the intrinsically stronger absorption lines. For more than 15 years, NASA LangleyResearch Center (LaRC) contributed in developing several 2-?m CO2 DIAL systems and technologies. This paperfocuses on the current development of the airborne double-pulsed and triple-pulsed 2-?m CO2 integrated pathdifferential absorption (IPDA) lidar system at NASA LaRC. This includes the IPDA system development andintegration. Results from ground and airborne CO2 IPDA testing will be presented. The potential of scaling suchtechnology to a space mission will be addressed.

  2. Study of Pulsed vs. RF Plasma Properties for Surface Processing Applications

    NASA Astrophysics Data System (ADS)

    Tang, Ricky; Hopkins, Matthew; Barnat, Edward; Miller, Paul

    2015-09-01

    The ability to manipulate the plasma parameters (density, E/N) was previously demonstrated using a double-pulsed column discharge. Experiments extending this to large-surface plasmas of interest to the plasma processing community were conducted. Differences between an audio-frequency pulsed plasma and a radio-frequency (rf) discharge, both prevalent in plasma processing applications, were studied. Optical emission spectroscopy shows higher-intensity emission in the UV/visible range for the pulsed plasma comparing to the rf plasma at comparable powers. Data suggest that the electron energy is higher for the pulsed plasma leading to higher ionization, resulting in increased ion density and ion flux. Diode laser absorption measurements of the concentration of the 1S5 metastable and 1S4 resonance states of argon (correlated with the plasma E/N) provide comparisons between the excitation/ionization states of the two plasmas. Preliminary modeling efforts suggest that the low-frequency polarity switch causes a much more abrupt potential variation to support interesting transport phenomena, generating a ``wave'' of higher temperature electrons leading to more ionization, as well as ``sheath capture'' of a higher density bolus of ions that are then accelerated during polarity switch.

  3. Visual area V5/hMT+ contributes to perception of tactile motion direction: a TMS study.

    PubMed

    Amemiya, Tomohiro; Beck, Brianna; Walsh, Vincent; Gomi, Hiroaki; Haggard, Patrick

    2017-01-20

    Human imaging studies have reported activations associated with tactile motion perception in visual motion area V5/hMT+, primary somatosensory cortex (SI) and posterior parietal cortex (PPC; Brodmann areas 7/40). However, such studies cannot establish whether these areas are causally involved in tactile motion perception. We delivered double-pulse transcranial magnetic stimulation (TMS) while moving a single tactile point across the fingertip, and used signal detection theory to quantify perceptual sensitivity to motion direction. TMS over both SI and V5/hMT+, but not the PPC site, significantly reduced tactile direction discrimination. Our results show that V5/hMT+ plays a causal role in tactile direction processing, and strengthen the case for V5/hMT+ serving multimodal motion perception. Further, our findings are consistent with a serial model of cortical tactile processing, in which higher-order perceptual processing depends upon information received from SI. By contrast, our results do not provide clear evidence that the PPC site we targeted (Brodmann areas 7/40) contributes to tactile direction perception.

  4. The timing of anterior temporal lobe involvement in semantic processing.

    PubMed

    Jackson, Rebecca L; Lambon Ralph, Matthew A; Pobric, Gorana

    2015-07-01

    Despite indications that regions within the anterior temporal lobe (ATL) might make a crucial contribution to pan-modal semantic representation, to date there have been no investigations of when during semantic processing the ATL plays a critical role. To test the timing of the ATL involvement in semantic processing, we studied the effect of double-pulse TMS on behavioral responses in semantic and difficulty-matched control tasks. Chronometric TMS was delivered over the left ATL (10 mm from the tip of the temporal pole along the middle temporal gyrus). During each trial, two pulses of TMS (40 msec apart) were delivered either at baseline (before stimulus presentation) or at one of the experimental time points 100, 250, 400, and 800 msec poststimulus onset. A significant disruption to performance was identified from 400 msec on the semantic task but not on the control assessment. Our results not only reinforce the key role of the left ATL in semantic representation but also indicate that its contribution is especially important around 400 msec poststimulus onset. Together, these facts suggest that the ATL may be one of the neural sources of the N400 ERP component.

  5. Evaluation of diffuse-illumination holographic cinematography in a flutter cascade

    NASA Technical Reports Server (NTRS)

    Decker, A. J.

    1986-01-01

    Since 1979, the Lewis Research Center has examined holographic cinematography for three-dimensional flow visualization. The Nd:YAG lasers used were Q-switched, double-pulsed, and frequency-doubled, operating at 20 pulses per second. The primary subjects for flow visualization were the shock waves produced in two flutter cascades. Flow visualization was by diffuse-illumination, double-exposure, and holographic interferometry. The performances of the lasers, holography, and diffuse-illumination interferometry are evaluated in single-window wind tunnels. The fringe-contrast factor is used to evaluate the results. The effects of turbulence on shock-wave visualization in a transonic flow are discussed. The depth of field for visualization of a turbulent structure is demonstrated to be a measure of the relative density and scale of that structure. Other items discussed are the holographic emulsion, tests of coherence and polarization, effects of windows and diffusers, hologram bleaching, laser configurations, influence and handling of specular reflections, modes of fringe localization, noise sources, and coherence requirements as a function of the pulse energy. Holography and diffuse illumination interferometry are also reviewed.

  6. Recovery of a CVD diamond detection system from strong pulses of laser produced x-rays

    SciTech Connect

    Dauffy, L S; Koch, J A; Izumi, N; Tommasini, R; Lerche, R A

    2006-04-25

    We are studying the response of a CVD diamond detector to a strong x-ray pulse followed by a second weaker pulse arriving 50 to 300 ns later, with a contrast in amplitude of about 1000. These tests, performed at the LLNL Jupiter laser facility, are intended to produce charge carrier densities similar to those expected during a DT implosion at NIF, where a large 14.1 MeV neutron pulse is followed by a weak downscattered neutron signal produced by slower 6-10 MeV neutrons. The number of downscattered neutrons must be carefully measured in order to obtain an accurate value for the areal density, which is proportional to the ratio of downscattered to primary neutrons. The effects of the first strong pulse may include saturation of the diamond wafer, saturation of the oscilloscope, or saturation of the associated power and data acquisition electronics. We are presenting a double pulse experiment that will use a system of several polycrystalline CVD diamond detectors irradiated by 8.6 keV x-rays emitted from a zinc target. We will discuss implication for a NIF areal density measurement.

  7. Charge Carrier Density and signal induced in a CVD diamond detector from NIF DT neutrons, x-rays, and electrons

    SciTech Connect

    Dauffy, L S; Koch, J A

    2005-10-20

    This report investigates the use of x-rays and electrons to excite a CVD polycrystalline diamond detector during a double pulse experiment to levels corresponding to those expected during a successful (1D clean burn) and a typical failed ignition (2D fizzle) shot at the National Ignition Facility, NIF. The monitoring of a failed ignition shot is the main goal of the diagnostic, but nevertheless, the study of a successful ignition shot is also important. A first large neutron pulse is followed by a smaller pulse (a factor of 1000 smaller in intensity) after 50 to 300 ns. The charge carrier densities produced during a successful and failed ignition shot are about 10{sup 15} e-h+/cm{sup 3} and 2.6* 10{sup 12} e-h+/cm{sup 3} respectively, which is lower than the 10{sup 16} e-h+/cm{sup 3} needed to saturate the diamond wafer due to charge recombination. The charge carrier density and the signal induced in the diamond detector are calculated as a function of the incident x-ray and electron energy, flux, and detector dimensions. For available thicknesses of polycrystalline CVD diamond detectors (250 {micro}m to 1000 {micro}m), a flux of over 10{sup 11} x-rays/cm{sup 2} (with x-ray energies varying from 6 keV to about 10 keV) or 10{sup 9} {beta}/cm{sup 2} (corresponding to 400 pC per electron pulse, E{sub {beta}} > 800 keV) is necessary to excite the detector to sufficient levels to simulate a successful ignition's 14 MeV peak. Failed ignition levels would require lower fluxes, over 10{sup 8} x-rays/cm{sup 2} (6 to 10 keV) or 10{sup 6} {beta}/cm{sup 2} (1 pC per electron pulse, E{sub {beta}} > 800 keV). The incident pulse must be delivered on the detector surface in several nanoseconds. The second pulse requires fluxes down by a factor of 1000. Several possible x-ray beam facilities are investigated: (1) the LBNL Advanced Light Source, (2) the Stanford SLAC and SPEAR, (3) the BNL National Synchrotron Light Source, (4) the ANL Advanced Photon Source, (5) the LLNL Janus

  8. Miniature fiber-optic multiphoton microscopy system using frequency-doubled femtosecond Er-doped fiber laser

    PubMed Central

    Huang, Lin; Mills, Arthur K.; Zhao, Yuan; Jones, David J.; Tang, Shuo

    2016-01-01

    We report on a miniature fiber-optic multiphoton microscopy (MPM) system based on a frequency-doubled femtosecond Er-doped fiber laser. The femtosecond pulses from the laser source are delivered to the miniature fiber-optic probe at 1.58 µm wavelength, where a standard single mode fiber is used for delivery without the need of free-space dispersion compensation components. The beam is frequency-doubled inside the probe by a periodically poled MgO:LiNbO3 crystal. Frequency-doubled pulses at 786 nm with a maximum power of 80 mW and a pulsewidth of 150 fs are obtained and applied to excite intrinsic signals from tissues. A MEMS scanner, a miniature objective, and a multimode collection fiber are further used to make the probe compact. The miniature fiber-optic MPM system is highly portable and robust. Ex vivo multiphoton imaging of mammalian skins demonstrates the capability of the system in imaging biological tissues. The results show that the miniature fiber-optic MPM system using frequency-doubled femtosecond fiber laser can potentially bring the MPM imaging for clinical applications. PMID:27231633

  9. First Airborne Lidar Measurements of Methane and Carbon Dioxide Applying the MERLIN Demonstrator CHARM-F

    NASA Astrophysics Data System (ADS)

    Amediek, Axel; Büdenbender, Christian; Ehret, Gerhard; Fix, Andreas; Gerbig, Christoph; Kiemle, Chritstoph; Quatrevalet, Mathieu; Wirth, Martin

    2016-04-01

    CHARM-F is the new airborne four-wavelengths lidar for simultaneous soundings of atmospheric CO2 and CH4. Due to its high technological conformity it is also a demonstrator for MERLIN, the French-German satellite mission providing a methane lidar. MERLIN's Preliminary Design Review was successfully passed recently. The launch is planned for 2020. First CHARM-F measurements were performed in Spring 2015 onboard the German research aircraft HALO. The aircraft's maximum flight altitude of 15 km and special features of the lidar, such as a relatively large laser ground spot, result in data similar to those obtained by a spaceborne system. The CHARM-F and MERLIN lidars are designed in the IPDA (integrated path differential absorption) configuration using short double pulses, which gives column averaged gas mixing ratios between the system and ground. The successfully completed CHARM-F flight measurements provide a valuable dataset, which supports the retrieval algorithm development for MERLIN notably. Furthermore, the dataset allows detailed analyses of measurement sensitivities, general studies on the IPDA principle and on system design questions. These activities are supported by another instrument onboard the aircraft during the flight campaign: a cavity ring down spectrometer, providing in-situ data of carbon dioxide, methane and water vapor with high accuracy and precision, which is ideal for validation purposes of the aircraft lidar. For the near future, detailed characterizations of CHARM-F are planned, further support of the MERLIN design, as well as the scientific aircraft campaign CoMet.

  10. Collisional lasing on a self-terminating transition 2{sup 1}P{sup o}{sub 1} - 2{sup 1}S{sub 0} in helium atom

    SciTech Connect

    Bel'skaya, E V; Bokhan, P A; Zakrevskii, D E; Lavrukhin, M A

    2012-02-28

    Lasing on a self-terminating transition 2{sup 1}P{sup o}{sub 1} - 2{sup 1}S{sub 0} ({lambda} = 2.058 {mu}m) in helium atom is studied for a single- and double-pulse operation regimes under electron beam pumping in pure helium and its mixtures with H{sub 2}, N{sub 2}, O{sub 2}, CO{sub 2}, H{sub 2}O, NH{sub 3}, and N{sub 2}O. In pure helium, the maximal pulse duration is {approx}50 ns, which agrees with the calculated value. Recovery of lasing in the second pulse is observed at a time delay between the pulses of longer than 1.25 {mu}s. In adding CO{sub 2}, N{sub 2}O, NH{sub 3}, and H{sub 2}O, the relaxation rate for population of the metastable state He(2{sup 1}S{sub 0}) increases, which makes the delay, needed for recovering lasing, shorter up to pulse merging in the case of H{sub 2}O. At the exciting pulse base-level duration of 1.2 {mu}s, in mixtures of helium with NH{sub 3} and H{sub 2}O, laser pulses with a duration of {approx}0.8 {mu}s are observed, which testifies that collisional quasi-cw lasing occurs. Mechanisms of collisional lasing are discussed.

  11. Time-resolved imaging of nanosecond-pulsed micro-discharges in heptane

    NASA Astrophysics Data System (ADS)

    Hamdan, A.; Marinov, I.; Rousseau, A.; Belmonte, T.

    2014-02-01

    Nanosecond-pulsed micro-discharges in heptane are studied by time-resolved imaging in pin-to-plate configuration. When a voltage of +5 kV is applied to the pin electrode, the discharge exhibits one maximum in light intensity. At +15 kV, filtered images show that up to three maxima can be identified. These maxima are associated with local electron-ion recombination and bremsstrahlung emission and attributed to the development of a complex space-charge field. In the post-discharge, the dynamics of the gas bubble can be simulated by the Gilmore model, and the pressure evolution in this bubble is predicted. From our results, it seems reasonable to think that the gas bubble develops from the post-discharge of the spark. Results obtained by using the double-pulse technique show that light emission during the post-discharge of the second discharge lasts 10 times longer than the post-discharge of the first spark. The pressure drop in the gas bubble, predicted by the Gilmore model, is used to explain this result and it provides a control method by optical diagnostics in liquids.

  12. Evoked-potential recovery during double click stimulation in a beluga whale: implications for biosonar gain control.

    PubMed

    Supin, Alexander Ya; Popov, Vladimir V

    2015-05-01

    Auditory evoked potentials (AEPs) were recorded in a beluga whale Delphinapterus leucas using a double-pulse stimulation paradigm, specifically measuring the recovery (release from masking) of the second (test) response as a function of delay after the first (conditioning) pulse at various levels of the conditioning and test stimuli. The conditioning/test stimulus level ratio influenced the recovery time (the higher the ratio, the longer the recovery). This interrelation was used to evaluate the intensity/time trade in release from forward masking. Trade was evaluated as 32.2 dB per time decade. Data were considered as simulating interactions between the transmitted pulse and echo during echolocation, assuming that a transmitted sonar pulse produces forward masking of the echo response. With increased target distance, the attenuation of the echo may be compensated by the release from masking. According to the model, the compensation results in substantial stabilization of the echo response even if the intensity/time trade of release from masking is not precisely equal to the rate of echo attenuation with distance.

  13. Characterization and Comparison of Planar and Trench Silicon Carbide (SiC) Power MOSFETs

    SciTech Connect

    Wang, Zhiqiang; Chinthavali, Madhu Sudhan; Campbell, Steven L

    2016-01-01

    This paper presents a comprehensive evaluation and experimental comparison of silicon carbide power MOSFETs through double pulse test. First, a universal hardware platform is designed and developed to test power semiconductor devices with various device packages and measuring requirements. Using the developed platform, the static characteristics and switching performance of the two types of SiC MOSFETs (one planar and one trench type) are evaluated under different case temperatures from 25 oC to 175 oC. Based on the evaluation data, a comparison of both SiC MOSFETs is conducted in terms of their on-state resistance, switching loss, and temperature dependent behavior. It is found that the latest trench SiC MOSFETs present similar switching loss while much lower conduction loss compared to existing commercial planar SiC MOSFETs. Moreover, the trench devices show a nearly temperature independent switching loss, which is beneficial to suppress the potential thermal runaway issue under high temperature continuous operation.

  14. Phototube Testing for the MiniBooNE Experiment

    NASA Astrophysics Data System (ADS)

    Gladstone, Laura; Brice, Steve; Bugel, Len; Fleming, Bonnie; Hawker, Eric; Killewald, Phillip; May, Justin; McKenney, Shawn; Nienaber, Paul; Patterson, Ryan; Roe, Byron; Sandberg, Vern; Smith, Darrel; Wysocki, Matt

    2005-04-01

    The MiniBooNE experiment at FNAL is a neutrino νμ->νe oscillation search whose detector is a 12 m spherical oil tank lined with 1520 8 inch photomultiplier tubes, Hamamatsu models R1408 and R5912, with custom--designed bases. Tests were performed on all the phototubes to determine the dark rate, charge and timing resolutions of the response, double--pulsing rate, and desired operating voltage for each tube, so that they could be sorted for optimal use in the detector. Eight additional phototubes were tested to find the angular dependance of their response, and these results for the R1408 and R5912 phototubes were fit to 5-- and 6--degree polynomials, respectively. This test was performed again at various voltages. These fits were incorporated into the MiniBooNE Monte Carlo. After the Super--K phototube implosion accident, an analysis was performed to determine the risk of a similar accident with MiniBooNE, and the risk was found to be negligible. *MiniBooNE is an experiment at Fermi National Accelerator Laboratory

  15. Multimodal cross-talk of olfactory and gustatory information in the endopiriform nucleus in rats.

    PubMed

    Sugai, T; Yamamoto, R; Yoshimura, H; Kato, N

    2012-10-01

    The endopiriform nucleus (EPN) is a large group of multipolar cells located in the depth of the piriform cortex (PC). Although many studies have suggested that the EPN plays a role in temporal lobe epilepsy, the normal function of the EPN remains to be elucidated. By using optical imaging of coronal brain slice preparations with voltage-sensitive dye, we found signal propagation from the PC or gustatory cortex (GC) to the EPN in normal medium. In our previous research, we failed to elicit a reliable signal reproducibly in the EPN by single stimulation either to the PC or GC. In our current research, we found that a double-pulse stimulation to either the PC or GC (interpulse interval: 20-100 ms) induced robust signal propagation to the EPN through excitation in the agranular division of the insular cortex (AI), with further extension to the claustrum. Finally, double site paired-pulse stimulation to the PC and GC also evoked excitation in the AI, claustrum, and EPN. These results suggest that the EPN has dual roles: 1) further processing of modality-specific olfactory and gustatory information from the PC and GC, respectively and 2) synergistic integration of PC-derived olfactory information and GC-derived gustatory information.

  16. Motor simulation and the coordination of self and other in real-time joint action

    PubMed Central

    Ticini, Luca F.; Schütz-Bosbach, Simone; Keller, Peter E.

    2014-01-01

    Joint actions require the integration of simultaneous self- and other-related behaviour. Here, we investigated whether this function is underpinned by motor simulation, that is the capacity to represent a perceived action in terms of the neural resources required to execute it. This was tested in a music performance experiment wherein on-line brain stimulation (double-pulse transcranial magnetic stimulation, dTMS) was employed to interfere with motor simulation. Pianists played the right-hand part of piano pieces in synchrony with a recording of the left-hand part, which had (Trained) or had not (Untrained) been practiced beforehand. Training was assumed to enhance motor simulation. The task required adaptation to tempo changes in the left-hand part that, in critical conditions, were preceded by dTMS delivered over the right primary motor cortex. Accuracy of tempo adaptation following dTMS or sham stimulations was compared across Trained and Untrained conditions. Results indicate that dTMS impaired tempo adaptation accuracy only during the perception of trained actions. The magnitude of this interference was greater in empathic individuals possessing a strong tendency to adopt others’ perspectives. These findings suggest that motor simulation provides a functional resource for the temporal coordination of one’s own behaviour with others in dynamic social contexts. PMID:23709353

  17. Parametric dispersion and amplification of acoustohelicon waves in piezoelectric semiconductors

    NASA Astrophysics Data System (ADS)

    Neogi, A.; Ghosh, S.

    1991-01-01

    Assuming that the origin of the nonlinear interaction lies in the second-order optical susceptibility arising from the nonlinear induced current density and using the coupled-mode theory, the parametric dispersion and amplification of acoustohelicon waves is analytically investigated in a longitudinally magnetized piezoelectric semiconductor of noncentrosymmetric nature. The relevant experiments have not been reported. The threshold value of the pump electric field E0th and its corresponding excitation intensity is obtained. The longitudinal magnetic field decreases the required magnitude of E0th for the excitation of parametric amplification. The phenomenon of self-defocusing of the signal in the prevailing case is found to be a consequence of the negative dispersive characteristics exhibited by the acoustohelicon waves. Numerical analyses are performed for an InSb crystal at 77 K, duly irradiated by frequency-doubled pulsed 10.6-μm CO2 lasers. The parametric gain constant is observed to be maximum when the cyclotron frequency ωc attains the magnitude equal to that of ω0, the incident laser frequency (=1.78×1014 s-1 ).

  18. Flux amplification and sustainment of ST plasmas by multi-pulsed coaxial helicity injection on HIST

    NASA Astrophysics Data System (ADS)

    Higashi, T.; Ishihara, M.; Kikuchi, Y.; Fukumoto, N.; Nagata, M.

    2010-11-01

    The Helicity Injected Spherical Torus (HIST) device has been developed towards high-current start up and sustainment by Multi-pulsed Coaxial Helicity Injection (M-CHI) method. Multiple pulses operation of the coaxial plasma gun can build the magnetic field of STs and spheromak plasmas in a stepwise manner. So far, successive gun pulses on SSPX at LLNL were demonstrated to maintain the magnetic field of spheromak in a quasi-steady state against resistive decay [1]. The resistive 3D-MHD numerical simulation [2] for STs reproduced the current amplification by the M-CHI method and confirmed that stochastic magnetic field was reduced during the decay phase. By double pulsed operation on HIST, the plasma current was effectively amplified against the resistive decay. The life time increases up to 10 ms which is longer than that in the single CHI case (4 ms). The edge poloidal fields last between 0.5 ms and 6 ms like a repetitive manner. During the second driven phase, the toroidal ion flow is driven in the same direction as the plasma current as well as in the initial driven phase. At the meeting, we will discuss a current amplification mechanism based on the merging process with the plasmoid injected secondly from the gun. [1] B. Hudson et al., Phys. Plasmas Vol.15, 056112 (2008). [2] Y. Kagei et al., J. Plasma Fusion Res. Vol.79, 217 (2003).

  19. Parametric Study of Carbon Nanotube Production by Laser Ablation Process

    NASA Technical Reports Server (NTRS)

    Arepalli, Sivaram; Nikolaev, Pavel; Holmes, William; Hadjiev, Victor; Scott, Carl

    2002-01-01

    Carbon nanotubes form a new class of nanomaterials that are presumed to have extraordinary mechanical, electrical and thermal properties. The single wall nanotubes (SWNTs) are estimated to be 100 times stronger than steel with 1/6th the weight; electrical carrying capacity better than copper and thermal conductivity better than diamond. Applications of these SWNTs include possible weight reduction of aerospace structures, multifunctional materials, nanosensors and nanoelectronics. Double pulsed laser vaporization process produces SWNTs with the highest percentage of nanotubes in the output material. The normal operating conditions include a green laser pulse closely followed by an infrared laser pulse. Lasers ab late a metal-containing graphite target located in a flow tube maintained in an oven at 1473K with argon flow of 100 sccm at a 500 Torr pressure. In the present work a number of production runs were carried out, changing one operating condition at a time. We have studied the effects of nine parameters, including the sequencing of the laser pulses, pulse separation times, laser energy densities, the type of buffer gas used, oven temperature, operating pressure, flow rate and inner flow tube diameters. All runs were done using the same graphite target. The collected nanotube material was characterized by a variety of analytical techniques including scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman and thermo gravimetric analysis (TGA). Results indicate trends that could be used to optimize the process and increase the efficiency of the production process.

  20. Controlled electrodeposition of bismuth nanocatalysts for the solution-liquid-solid synthesis of CdSe nanowires on transparent conductive substrates.

    PubMed

    Reim, Natalia; Littig, Alexander; Behn, Dino; Mews, Alf

    2013-12-11

    Semiconductor nanowires (NWs) composed of cadmium selenide (CdSe) have been directly grown on transparent conductive substrates via the solution-liquid-solid (SLS) approach using electrodeposited bismuth nanoparticles (Bi NPs) as catalyst. Bi NPs were fabricated on indium tin oxide (ITO) surfaces from a bismuth trichloride solution using potentiostatic double-pulse techniques. The size and density of electrodeposited Bi NPs were controlled by the pulse parameters. Since the NW diameter is governed by the dimension of the Bi catalyst, the electrodeposition is a reliable method to synthesize nanowires directly on substrates with a desired size and density. We show that the density can be adjusted from individual NWs on several square micrometer to very dense NW networks. The diameter can be controlled between thick nanowires above 100 nm to very thin NW of 7 nm in diameter, which is well below the respective exciton dimension. Hence, especially the thinnest NWs exhibit diameter-dependent photoluminescence energies as a result of quantum confinement effects in the radial dimension.

  1. Digital PIV Measurements of Acoustic Particle Displacements in a Normal Incidence Impedance Tube

    NASA Technical Reports Server (NTRS)

    Humphreys, William M., Jr.; Bartram, Scott M.; Parrott, Tony L.; Jones, Michael G.

    1998-01-01

    Acoustic particle displacements and velocities inside a normal incidence impedance tube have been successfully measured for a variety of pure tone sound fields using Digital Particle Image Velocimetry (DPIV). The DPIV system utilized two 600-mj Nd:YAG lasers to generate a double-pulsed light sheet synchronized with the sound field and used to illuminate a portion of the oscillatory flow inside the tube. A high resolution (1320 x 1035 pixel), 8-bit camera was used to capture double-exposed images of 2.7-micron hollow silicon dioxide tracer particles inside the tube. Classical spatial autocorrelation analysis techniques were used to ascertain the acoustic particle displacements and associated velocities for various sound field intensities and frequencies. The results show that particle displacements spanning a range of 1-60 microns can be measured for incident sound pressure levels of 100-130 dB and for frequencies spanning 500-1000 Hz. The ability to resolve 1 micron particle displacements at sound pressure levels in the 100 dB range allows the use of DPIV systems for measurement of sound fields at much lower sound pressure levels than had been previously possible. Representative impedance tube data as well as an uncertainty analysis for the measurements are presented.

  2. Orthogonal Double View Digital Holographic Diagnostics for Random Motion of Micro Polymer Jet by Electrospinning

    NASA Astrophysics Data System (ADS)

    Lee, Jaiho; Sallam, Khaled

    2008-11-01

    An experimental investigation of three-dimensional random behavior of polymer micro jet generated by electrospinning is described. Two frequency doubled Nd:YAG lasers were used as the light source and a commercial grade CCD sensor (Nikon D-70) was used for holograms recording. The two lasers could be fired with a pulse separation as small as 100 ns, and the two laser beams were aligned with three polarized beam splitter cubes. Orthogonal double-view and double-pulses were recorded on the same camera frame. The camera frame was split into two, and both of the halves of the frame were used for each view. Two objective lenses (M 5x) and two spatial filters (Pinhole ˜ 5μm) were used to generate expanding laser beams in the digital microscopic holography (DMH) optical setup. As the electric field (˜20 kV) was intensified, the polymer solution formed a charged filament (or multiple filaments) from the tip of the Taylor cone. As the filament was accelerated toward the collector, its diameter was shrunk and axisymmetric disturbances grew further away from the exit. The polymer was randomly deposited on the collector as non woven microfiber.

  3. Influence of shielding gas on the mechanical and metallurgical properties of DP-GMA-welded 5083-H321 aluminum alloy

    NASA Astrophysics Data System (ADS)

    Koushki, Amin Reza; Goodarzi, Massoud; Paidar, Moslem

    2016-12-01

    In the present research, 6-mm-thick 5083-H321 aluminum alloy was joined by the double-pulsed gas metal arc welding (DP-GMAW) process. The objective was to investigate the influence of the shielding gas composition on the microstructure and properties of GMA welds. A macrostructural study indicated that the addition of nitrogen and oxygen to the argon shielding gas resulted in better weld penetration. Furthermore, the tensile strength and bending strength of the welds were improved when oxygen and nitrogen (at concentrations as high as approximately 0.1vol%) were added to the shielding gas; however, these properties were adversely affected when the oxygen and nitrogen contents were increased further. This behavior was attributed to the formation of excessive brown and black oxide films on the bead surface, the formation of intermetallic compounds in the weld metal, and the formation of thicker oxide layers on the bead surface with increasing nitrogen and oxygen contents in the argon-based shielding gas. Analysis by energy-dispersive X-ray spectroscopy revealed that most of these compounds are nitrides or oxides.

  4. Fresh-slice multicolour X-ray free-electron lasers

    SciTech Connect

    Lutman, Alberto A.; Maxwell, Timothy J.; MacArthur, James P.; Guetg, Marc W.; Berrah, Nora; Coffee, Ryan N.; Ding, Yuantao; Huang, Zhirong; Marinelli, Agostino; Moeller, Stefan; Zemella, Johann C. U.

    2016-10-24

    X-ray free-electron lasers (XFELs) provide femtosecond X-ray pulses with a narrow energy bandwidth and unprecedented brightness. Ultrafast physical and chemical dynamics, initiated with a site-specific X-ray pulse, can be explored using XFELs with a second ultrashort X-ray probe pulse. However, existing double-pulse schemes are complicated, difficult to customize or provide only low-intensity pulses. Here we present the novel fresh-slice technique for multicolour pulse production, wherein different temporal slices of an electron bunch lase to saturation in separate undulator sections. This method combines electron bunch tailoring from a passive wakefield device with trajectory control to provide multicolour pulses. The fresh-slice scheme outperforms existing techniques at soft X-ray wavelengths. It produces femtosecond pulses with a power of tens of gigawatts and flexible colour separation. The pulse delay can be varied from temporal overlap to almost one picosecond. As a result, we also demonstrate the first three-colour XFEL and variably polarized two-colour pulses.

  5. Fresh-slice multicolour X-ray free-electron lasers

    DOE PAGES

    Lutman, Alberto A.; Maxwell, Timothy J.; MacArthur, James P.; ...

    2016-10-24

    X-ray free-electron lasers (XFELs) provide femtosecond X-ray pulses with a narrow energy bandwidth and unprecedented brightness. Ultrafast physical and chemical dynamics, initiated with a site-specific X-ray pulse, can be explored using XFELs with a second ultrashort X-ray probe pulse. However, existing double-pulse schemes are complicated, difficult to customize or provide only low-intensity pulses. Here we present the novel fresh-slice technique for multicolour pulse production, wherein different temporal slices of an electron bunch lase to saturation in separate undulator sections. This method combines electron bunch tailoring from a passive wakefield device with trajectory control to provide multicolour pulses. The fresh-slice schememore » outperforms existing techniques at soft X-ray wavelengths. It produces femtosecond pulses with a power of tens of gigawatts and flexible colour separation. The pulse delay can be varied from temporal overlap to almost one picosecond. As a result, we also demonstrate the first three-colour XFEL and variably polarized two-colour pulses.« less

  6. Analysis of the dynamic avalanche of carrier stored trench bipolar transistor (CSTBT) during clamped inductive turn-off transient

    NASA Astrophysics Data System (ADS)

    Xue, Peng; Fu, Guicui

    2017-03-01

    The dynamic avalanche has a huge impact on the switching robustness of carrier stored trench bipolar transistor (CSTBT). The purpose of this work is to investigate the CSTBT's dynamic avalanche mechanism during clamped inductive turn-off transient. At first, with a Mitsubishi 600 V/150 A CSTBT and a Infineon 600 V/200 A field stop insulated gate bipolar transistor (FS-IGBT) utilized, the clamped inductive turn-off characteristics are obtained by double pulse test. The unclamped inductive switching (UIS) test is also utilized to identify the CSTBT's clamping voltage under dynamic avalanche condition. After the test data analysis, it is found that the CSTBT's dynamic avalanche is abnormal and can be triggered under much looser condition than the conventional buffer layer IGBT. The comparison between the FS-IGBT and CSTBT's experimental results implies that the CSTBT's abnormal dynamic avalanche phenomenon may be induced by the carrier storage (CS) layer. Based on the semiconductor physics, the electric field distribution and dynamic avalanche generation in the depletion region are analyzed. The analysis confirms that the CS layer is the root cause of the CSTBT's abnormal dynamic avalanche mechanism. Moreover, the CSTBT's negative gate capacitance effect is also investigated to clarify the underlying mechanism of the gate voltage bump observed in the test. In the end, the mixed-mode numerical simulation is utilized to reproduce the CSTBT's dynamic avalanche behavior. The simulation results validate the proposed dynamic avalanche mechanisms.

  7. Comparison of line x-ray emission from solid and porous nano-layer coated targets irradiated by double laser pulses

    SciTech Connect

    Fazeli, R.; Mahdieh, M. H.

    2015-11-15

    Enhancement of line x-ray emission from both solid and porous iron targets induced by irradiation of single and double laser pulses is studied numerically. The line emission from laser produced plasma is calculated within the extreme ultra-violet lithography wavelength range of 13.5–13.7 nm. The effects of pre-pulse intensity and delay time between two pulses (pre-pulse and main pulse) are examined. The results show that using double pulses irradiation in the conditions of porous target can reduce the x-ray enhancement. According to the results, the use of both pre-pulse and porous target leads to efficient absorption of the laser energy. Calculations also show that such enhanced laser absorption can ionize atoms of the target material to very high degrees of ionization, leading to decrease of the density of appropriate ions that are responsible for line emission in the selected wavelength region. By increasing the target porosity, x-ray yield was more reduced.

  8. Modification of polymer velvet cathode via metallic Mo coating for enhancement of high-current electron emission performances

    SciTech Connect

    Xiong, Ying; Wang, Bing; Yi, Yong; Xia, Liansheng; Zhang, Huang

    2013-09-15

    The effect of surface Mo coating on the high-current electron emission performances for polymer velvet cathode has been investigated in a diode with A-K gap of 11.5 cm by the combination of time-resolved electrical diagnostic and temporal pressure variation. Compared with uncoated polymer velvet cathode under the single-pulsed emission mode, the Mo-coated one shows lower outgassing levels (∼0.40 Pa L), slower cathode plasma expansion velocity (∼2.30 cm/μs), and higher emission stability as evidences by the change in cathode current, temporal pressure variation, and diode perveance. Moreover, after Mo coating, the emission consistency of the polymer velvet cathode between two adjacent pulses is significantly improved in double-pulsed emission mode with ∼500 ns interval between two pulses, which further confirms the effectiveness of Mo coating for enhancement of electron emission performance of polymer velvet cathodes. These results should be of interest to the high-repetitive high-power microwave systems with cold cathodes.

  9. Anoxia/high temperature double whammy during the Permian-Triassic marine crisis and its aftermath

    NASA Astrophysics Data System (ADS)

    Song, Haijun; Wignall, Paul B.; Chu, Daoliang; Tong, Jinnan; Sun, Yadong; Song, Huyue; He, Weihong; Tian, Li

    2014-02-01

    The Permian-Triassic mass extinction was the most severe biotic crisis in the past 500 million years. Many hypotheses have been proposed to explain the crisis, but few account for the spectrum of extinction selectivity and subsequent recovery. Here we show that selective losses are best accounted for by a combination of lethally warm, shallow waters and anoxic deep waters that acted to severely restrict the habitable area to a narrow mid-water refuge zone. The relative tolerance of groups to this double whammy provides the first clear explanation for the selective extinction losses during this double-pulsed crisis and also the fitful recovery. Thus, high temperature intolerant shallow-water dwellers, such as corals, large foraminifers and radiolarians were eliminated first whilst high temperature tolerant ostracods thrived except in anoxic deeper-waters. In contrast, hypoxia tolerant but temperature intolerant small foraminifers were driven from shallow-waters but thrived on dysoxic slopes margins. Only those mollusc groups, which are tolerant of both hypoxia and high temperatures, were able to thrive in the immediate aftermath of the extinction. Limited Early Triassic benthic recovery was restricted to mid-water depths and coincided with intervals of cooling and deepening of water column anoxia that expanded the habitable mid-water refuge zone.

  10. Application of holography to the determination of flow conditions within the rotating blade row of a compressor

    NASA Technical Reports Server (NTRS)

    Hantman, R. G.; Burr, R. J.; Alwang, W. G.; Williams, M. C.

    1973-01-01

    The double-pulse, double-exposure holography technique was applied to visualize the flow field within a transonic compressor rotor with a tip speed of 1800 ft/sec. The principal objective was to visualize the shock waves created in the flow field which was supersonic relative to the rotating blade row. The upstream rotor blade bow shocks and, at high speed, the outermost portion of the leading edge passage shock were successfully observed in the holograms. Techniques were devised for locating these shocks in three dimensions, and the results were compared with theoretical predictions. Density changes between the two pulses due to motion of the shocks were large and, therefore, it was not possible to resolve the fringe systems in detail for the 100% speed conditions. However, gross features of the shocks were easily observed, and the upstream shocks were well displayed. In all cases the shock angles were somewhat larger than predicted by theory, and a distinct increase in angle near the outer wall was observed, which may be attributed to endwall boundary layer effects. The location and orientation of the observed leading edge passage shocks were in good agreement with static pressure contours obtained from measurements in the outer casing over the rotor tip.

  11. Laser-supported detonation waves and pulsed laser propulsion

    SciTech Connect

    Kare, J.T.

    1989-01-01

    A laser thermal rocket uses the energy of a large remote laser, possibly ground-based, to heat an inert propellant and generate thrust. Use of a pulsed laser allows the design of extremely simple thrusters with very high performance compared to chemical rockets. The temperatures, pressures, and fluxes involved in such thrusters (10{sup 4} K, 10{sup 2} atmospheres, 10{sup 7} w/cm{sup 2}) typically result in the creation of laser-supported detonation (LSD) waves. The thrust cycle thus involves a complex set of transient shock phenomena, including laser-surface interactions in the ignition if the LSD wave, laser-plasma interactions in the LSD wave itself, and high-temperature nonequilibrium chemistry behind the LSD wave. The SDIO Laser Propulsion Program is investigating these phenomena as part of an overall effort to develop the technology for a low-cost Earth-to-orbit laser launch system. We will summarize the program's approach to developing a high performance thruster, the double-pulse planar thruster, and present an overview of some results obtained to date, along with a discussion of the many research questions still outstanding in this area. 16 refs., 7 figs.

  12. Laser-supported detonation waves and pulsed laser propulsion

    SciTech Connect

    Kare, J. )

    1990-07-30

    A laser thermal rocket uses the energy of a large remote laser, possibly ground-based, to heat an inert propellant and generate thrust. Use of a pulsed laser allows the design of extremely simple thrusters with very high performance compared to chemical rockets. The temperatures, pressures, and fluxes involved in such thrusters (10{sup 4} K, 10{sup 2} atmospheres, 10{sup 7} w/cm{sup 2}) typically result in the creation of laser-supported detonation (LSD) waves. The thrust cycle thus involves a complex set of transient shock phenomena, including laser-surface interactions in the ignition of the LSD wave, laser-plasma interactions in the LSD wave itself, and high-temperature nonequilibrium chemistry behind the LSD wave. The SDIO Laser Propulsion Program is investigating these phenomena as part of an overall effort to develop the technology for a low-cost Earth-to-orbit laser launch system. We will summarize the Program's approach to developing a high performance thruster, the double-pulse planar thruster, and present an overview of some results obtained to date, along with a discussion of the many research question still outstanding in this area.

  13. ,* Copper transport and accumulation in spruce stems (picea abies(L.) Karsten) revelaed by laser-induced breakdown spectroscopy

    SciTech Connect

    Krajcarova, Dr. Lucie; Novotny, Dr. Karel; Babula, Dr. Petr; Pravaznik, Dr Ivo; Kucerova, Dr. Petra; Vojtech, Dr. Adam; Martin, Madhavi Z; Kizek, Dr. Rene; Kaiser, Jozef

    2013-01-01

    Laser-Induced Breakdown Spectroscopy (LIBS) in double pulse configuration (DP LIBS) was used for scanning elemental spatial distribution in annual terminal stems of spruce (Picea abies (L.) Karsten). Cross sections of stems cultivated in Cu2+ solution of different concentrations were prepared and analyzed by DP LIBS. Raster scanning with 150 m spatial resolution was set and 2D (2-dimentional) maps of Cu and Ca distribution were created on the basis of the data obtained. Stem parts originating in the vicinity of the implementation of the cross sections were mineralized and subsequently Cu and Ca contents were analyzed by inductively coupled plasma mass spectrometry (ICP-MS). The results provide quantitative information about overall concentration of the elements in places, where LIBS measurements were performed. The fluorescence pictures were created to compare LIBS distribution maps and the fluorescence intensity (or the increase in autofluorescence) was used for the comparison of ICP-MS quantitative results. Results from these three methods can be utilized for quantitative measurements of copper ions transport in different plant compartments in dependence on the concentration of cultivation medium and/or the time of cultivation.

  14. Anoxia/high temperature double whammy during the Permian-Triassic marine crisis and its aftermath.

    PubMed

    Song, Haijun; Wignall, Paul B; Chu, Daoliang; Tong, Jinnan; Sun, Yadong; Song, Huyue; He, Weihong; Tian, Li

    2014-02-19

    The Permian-Triassic mass extinction was the most severe biotic crisis in the past 500 million years. Many hypotheses have been proposed to explain the crisis, but few account for the spectrum of extinction selectivity and subsequent recovery. Here we show that selective losses are best accounted for by a combination of lethally warm, shallow waters and anoxic deep waters that acted to severely restrict the habitable area to a narrow mid-water refuge zone. The relative tolerance of groups to this double whammy provides the first clear explanation for the selective extinction losses during this double-pulsed crisis and also the fitful recovery. Thus, high temperature intolerant shallow-water dwellers, such as corals, large foraminifers and radiolarians were eliminated first whilst high temperature tolerant ostracods thrived except in anoxic deeper-waters. In contrast, hypoxia tolerant but temperature intolerant small foraminifers were driven from shallow-waters but thrived on dysoxic slopes margins. Only those mollusc groups, which are tolerant of both hypoxia and high temperatures, were able to thrive in the immediate aftermath of the extinction. Limited Early Triassic benthic recovery was restricted to mid-water depths and coincided with intervals of cooling and deepening of water column anoxia that expanded the habitable mid-water refuge zone.

  15. ESPY measurements of submerged composite plate vibrations

    SciTech Connect

    Pechersky, M.J.

    1990-12-31

    An Electronic Speckle pattern interferometer (ESPI) was constructed which performs full-field surface displacement measurements. This measurement technique when combined with a single-point measurement known as laser vibrometry, can completely determine the vibrational characteristics of complex structures. This information can, in turn, be used for nondestructive testing as well as for modal analysis. One NDT&E technique is to vibrationally excite the object and evaluate the time averaged interferograms from the ESPI and the vibration spectra from the vibrometer. Anomalies in the interferograms can be related to subsurface defects such as defective weld joints, internal cracks, voids, etc. All of this can be accomplished in a noncontacting and nonintrusive manor. In many instances, a finite element analysis in concert with this approach can be useful in interpreting the results. Since ESPI is analogous to optical holography, other methods equivalent to real-time and double-pulse holography may also be easily applied. As in holography, EXSPI is sensitive to out-of-plane surface displacements. Other optical arrangements can be implemented with the same equipment to give in-plane displacements which would give results similar to Moire interferometry without the need to apply gratings to the object under test. The advantage of this method over holographic interferometry is that the feedback from the measurements is for all practical purposes instantaneous. This has important positive ramifications with regard to the ease of performing measurements, relaxed stability requirements, and reliability.

  16. ESPY measurements of submerged composite plate vibrations

    SciTech Connect

    Pechersky, M.J.

    1990-01-01

    An Electronic Speckle pattern interferometer (ESPI) was constructed which performs full-field surface displacement measurements. This measurement technique when combined with a single-point measurement known as laser vibrometry, can completely determine the vibrational characteristics of complex structures. This information can, in turn, be used for nondestructive testing as well as for modal analysis. One NDT E technique is to vibrationally excite the object and evaluate the time averaged interferograms from the ESPI and the vibration spectra from the vibrometer. Anomalies in the interferograms can be related to subsurface defects such as defective weld joints, internal cracks, voids, etc. All of this can be accomplished in a noncontacting and nonintrusive manor. In many instances, a finite element analysis in concert with this approach can be useful in interpreting the results. Since ESPI is analogous to optical holography, other methods equivalent to real-time and double-pulse holography may also be easily applied. As in holography, EXSPI is sensitive to out-of-plane surface displacements. Other optical arrangements can be implemented with the same equipment to give in-plane displacements which would give results similar to Moire interferometry without the need to apply gratings to the object under test. The advantage of this method over holographic interferometry is that the feedback from the measurements is for all practical purposes instantaneous. This has important positive ramifications with regard to the ease of performing measurements, relaxed stability requirements, and reliability.

  17. Signal processing and flagellar motor switching during phototaxis of Halobacterium salinarum.

    PubMed

    Nutsch, Torsten; Marwan, Wolfgang; Oesterhelt, Dieter; Gilles, Ernst Dieter

    2003-11-01

    Prokaryotic taxis, the active search of motile cells for the best environmental conditions, is one of the paradigms for signal transduction. The search algorithm implemented by the cellular biochemistry modulates the probability of switching the rotational direction of the flagellar motor, a nanomachine that propels prokaryotic cells. On the basis of the well-known biochemical mechanisms of chemotaxis in Escherichia coli, kinetic modeling of the events leading from chemoreceptor activation by ligand binding to the motility response has been performed with great success. In contrast to Escherichia coli, Halobacterium salinarum, in addition, responds to visible light, which is sensed through specific photoreceptors of different wavelength sensitivity (phototaxis). Light stimuli of defined intensity and time course can be controlled precisely, which facilitates input-output measurements used for system analysis of the molecular network connecting the sensory receptors to the flagellar motor switch. Here, we analyze the response of halobacterial cells to single and double-pulse light stimuli and present the first kinetic model for prokaryotic cells that couples the signal-transduction pathway with the flagellar motor switch. Modeling based on experimental data supports the current biochemical model of halobacterial phototaxis. Moreover, the simulations demonstrate that motor switching occurs through subsequent rate-limiting steps, which are both under sensory control, suggesting that two signals may be involved in halobacterial phototaxis.

  18. Laser imaging in liquid-liquid flows

    NASA Astrophysics Data System (ADS)

    Abidin, M. I. I. Zainal; Park, Kyeong H.; Voulgaropoulos, Victor; Chinaud, Maxime; Angeli, Panagiota

    2016-11-01

    In this work, the flow patterns formed during the horizontal flow of two immiscible liquids are studied. The pipe is made from acrylic, has an ID of 26 mm and a length of 4 m. A silicone oil (5cSt) and a water/glycerol mixture are used as test fluids. This set of liquids is chosen to match the refractive indices of the phases and enable laser based flow pattern identification. A double pulsed Nd:Yag laser was employed (532mm) with the appropriate optics to generate a laser sheet at the middle of the pipe. The aqueous phase was dyed with Rhodamine 6G, to distinguish between the two phases. Experiments were carried out for mixture velocities ranging from 0.15 to 2 m/s. Different inlet designs were used to actuate flow patterns in a controlled way and observe their development downstream the test section. A static mixer produced dispersed flow at the inlet which separated downstream due to enhanced coalescence. On the other hand, the use of a cylindrical bluff body at the inlet created non-linear interfacial waves in initially stratified flows from which drops detached leading to the transition to dispersed patterns. From the detailed images important flow parameters were measured such as wave characteristics and drop size. Project funded under the UK Engineering and Physical Sciences Research Council (EPSRC) Programme Grant MEMPHIS.

  19. Closed electron drift in a self-magnetically insulated ion diode

    SciTech Connect

    Pushkarev, A. I.; Isakova, Y. I.

    2013-05-15

    The paper investigates a spiral geometry self-magnetically insulated ion diode with an explosive-emission cathode made from graphite. The experiments have been carried out using the TEMP-4M accelerator, with the accelerator configured to operate in double-pulse mode: the first negative pulse (300–500 ns, 100–150 kV) and the second positive pulse (150 ns, 250–300 kV). The ion beam energy density was 0.4–0.8 J/cm{sup 2} and the beam was composed of carbon ions (80%–85%) and protons. In order to increase the efficiency of ion current generation, we have developed a new diode with a spiral-shaped grounded electrode. Using this geometry, it seems possible to realize closed electron drift in a diode with self-magnetic insulation. In the spiral diode, the efficiency of accelerated ions is increased from 5%–9% (conventional self-insulated diodes) up to 30%–40%. The realization of closed electron drift in the diode increases the efficiency of C{sup +} ion generation up to 40–50 times the Childe-Langmuir limit, which is more than 4 times higher than with other known constructions of self-magnetically insulated diodes.

  20. Generation and diagnostics of pulsed intense ion beams with an energy density of 10 J/cm{sup 2}

    SciTech Connect

    Isakova, Yu. Pushkarev, A.; Khailov, I.; Zhong, H.

    2015-07-15

    The paper presents the results of a study on transportation and focusing of a pulsed ion beam at gigawatt power level, generated by a diode with explosive-emission cathode. The experiments were carried out with the TEMP-4M accelerator operating in double-pulse mode: the first pulse is of negative polarity (500 ns, 100-150 kV), and this is followed by a second pulse of positive polarity (120 ns, 200-250 kV). To reduce the beam divergence, we modified the construction of the diode. The width of the anode was increased compared to that of the cathode. We studied different configurations of planar and focusing strip diodes. It was found that the divergence of the ion beam formed by a planar strip diode, after construction modification, does not exceed 3° (half-angle). Modification to the construction of a focusing diode made it possible to reduce the beam divergence from 8° to 4°-5°, as well as to increase the energy density at the focus up to 10-12 J/cm{sup 2}, and decrease the shot to shot variation in the energy density from 10%-15% to 5%-6%. When measuring the ion beam energy density above the ablation threshold of the target material (3.5-4 J/cm{sup 2}), we used a metal mesh with 50% transparency to lower the energy density. The influence of the metal mesh on beam transport has been studied.

  1. Analysis of the reverse recovery oscillation of superjunction MOSFET body diode

    NASA Astrophysics Data System (ADS)

    Xue, Peng; Fu, Guicui

    2017-03-01

    The voltage and current oscillations occasionally occur during the reverse recovery transient of the superjunction MOSFET body diode. This paper identifies the unique reverse recovery oscillation characteristics of the superjunction MOSFET body diode. Base on the experimental investigation and theoretical analysis, the various reverse recovery oscillation mechanisms are clarified. At first, with a discrete 650 V/47 A superjunction MOSFET utilized, the high-frequency and low-frequency oscillation characteristics during the reverse recovery transient are obtained by the double-pulse test. After the theoretical analysis, it is found that the superjunction MOSFET body diode has various oscillation mechanisms depending on its drift region injection level. Under high-level injection condition, the high-frequency oscillation occurs due to the plasma extraction transient-time (PETT) effect. Under low-level injection condition, the body diode's snappy reverse recovery results in the low-frequency LC oscillation. In the end of the paper, the oscillation behaviors under both high and low level injection conditions are reproduced by the mixed-mode numerical simulation, the simulation results validate the proposed oscillation mechanisms.

  2. 3D Plenoptic PIV Measurements of a Shock Wave Boundary Layer Interaction

    NASA Astrophysics Data System (ADS)

    Thurow, Brian; Bolton, Johnathan; Arora, Nishul; Alvi, Farrukh

    2016-11-01

    Plenoptic particle image velocimetry (PIV) is a relatively new technique that uses the computational refocusing capability of a single plenoptic camera and volume illumination with a double-pulsed light source to measure the instantaneous 3D/3C velocity field of a flow field seeded with particles. In this work, plenoptic PIV is used to perform volumetric velocity field measurements of a shock-wave turbulent boundary layer interaction (SBLI). Experiments were performed in a Mach 2.0 flow with the SBLI produced by an unswept fin at 15°angle of attack. The measurement volume was 38 x 25 x 32 mm3 and illuminated with a 400 mJ/pulse Nd:YAG laser with 1.7 microsecond inter-pulse time. Conventional planar PIV measurements along two planes within the volume are used for comparison. 3D visualizations of the fin generated shock and subsequent SBLI are presented. The growth of the shock foot and separation region with increasing distance from the fin tip is observed and agrees with observations made using planar PIV. Instantaneous images depict 3D fluctuations in the position of the shock foot from one image to the next. The authors acknowledge the support of the Air Force Office of Scientific Research.

  3. Time resolved, near wall PIV measurements in a high Reynolds number turbulent pipe flow

    NASA Astrophysics Data System (ADS)

    Willert, C.; Soria, J.; Stanislas, M.; Amili, O.; Bellani, G.; Cuvier, C.; Eisfelder, M.; Fiorini, T.; Graf, N.; Klinner, J.

    2016-11-01

    We report on near wall measurements of a turbulent pipe flow at shear Reynolds numbers up to Reτ = 40000 acquired in the CICLoPE facility near Bologna, Italy. With 900 mm diameter and 110 m length the facility offers a well-established turbulent flow with viscous length scales ranging from y+ = 85 μ m at Reτ = 5000 to y+ = 11 μ m at Reτ = 40000 . These length scales can be resolved with a high-speed PIV camera at image magnification near unity. For the measurement the light of a high-speed, double-pulse laser is focused into a 300 μ m thin light sheet that is introduced radially into the pipe. The light scattered by 1 μ m water-glycerol droplet seeding is observed from the side by the camera via a thin high-aspect ratio mirror with a field of view covering 20mm in wall-normal and 5mm in stream-wise direction. Statistically converged velocity profiles could be achieved using 70000 samples per sequence acquired at low laser repetition rates (100Hz). Higher sampling rates of 10 kHz provide temporally coherent data from which frequency spectra can be derived. Preliminary analysis of the data shows a well resolved inner peak that grows with increasing Reynolds number. (Project funding through EuHIT - www.euhit.org)

  4. Proposal for a quantum delayed-choice experiment with a spin-mechanical setup

    NASA Astrophysics Data System (ADS)

    Li, Peng-Bo; Li, Fu-Li

    2016-10-01

    We describe an experimentally feasible protocol for performing a variant of the quantum delayed-choice experiment with massive objects. In this scheme, a single nitrogen-vacancy (NV) center in diamond driven by microwave fields is dispersively coupled to a massive mechanical resonator. A double-pulse Ramsey interferometer can be implemented with the spin-mechanical setup, where the second Ramsey microwave pulse drives the spin conditioned on the number states of the resonator. The probability for finding the NV center in definite spin states exhibits interference fringes when the mechanical resonator is prepared in a specific number state. On the other hand, the interference is destroyed if the mechanical resonator stays in some other number states. The wavelike and particlelike behavior of the NV spin can be superposed by preparing the mechanical resonator in a superposition of two distinct number states. Thus a quantum version of Wheeler's delayed-choice experiment could be implemented, allowing fundamental tests of quantum mechanics on a macroscopic scale.

  5. Investigation of charge balance in ion accelerator TEMP-4M

    NASA Astrophysics Data System (ADS)

    Khailov, I. P.; Pak, V. G.

    2014-10-01

    The paper presents the results of a study on the balance of charge in accelerator TEMP-4M operating in double-pulse mode with resistance load and ion diode. Crucially, it was found, that during the switching there is no losses of accumulated charge. It means, that all accumulated charge transferred to the load. However when the charge is transferred from the Marx generator to Blumlein line the half of accumulated charge is lost. Calibration of diagnostic equipment showed a good agreement between the calculated and experimental values of voltage and current. It means, that our diagnostic system is correct for registration parameters of the ion accelerator. A distinctive feature of the ion accelerators with self-magnetically insulated diode is that there is no need to use additional energy source for the creation of an external magnetic field. That's why the efficiency of ion diodes with an external magnetic field is not more than 10-15%. The efficiency of energy conversion in self-magnetically insulated diodes will be determined by not only the efficiency of the diode, but the energy losses in the units of the accelerator. The aim of the researches is the analysis of the balance of charge in units of the ion beams pulsed generator and definition of the most significant channels of energy loss.

  6. Tomography of homogenized laser-induced plasma by Radon transform technique

    NASA Astrophysics Data System (ADS)

    Eschlböck-Fuchs, S.; Demidov, A.; Gornushkin, I. B.; Schmid, T.; Rössler, R.; Huber, N.; Panne, U.; Pedarnig, J. D.

    2016-09-01

    Tomography of a laser-induced plasma in air is performed by inverse Radon transform of angle-resolved plasma images. Plasmas were induced by single laser pulses (SP), double pulses (DP) in collinear geometry, and by a combination of single laser pulses with pulsed arc discharges (SP-AD). Images of plasmas on metallurgical steel slags were taken at delay times suitable for calibration-free laser-induced breakdown spectroscopy (CF-LIBS). Delays ranged from few microseconds for SP and DP up to tens of microseconds for SP-AD excitation. The white-light and the spectrally resolved emissivity ε(x,y,z) was reconstructed for the three plasma excitation schemes. The electron number density Ne(x,y,z) and plasma temperature Te(x,y,z) were determined from Mg and Mn emission lines in reconstructed spectra employing the Saha-Boltzmann plot method. The SP plasma revealed strongly inhomogeneous emissivity and plasma temperature. Re-excitation of plasma by a second laser pulse (DP) and by an arc discharge (SP-AD) homogenized the plasma and reduced the spatial variation of ε and Te. The homogenization of a plasma is a promising approach to increase the accuracy of calibration-free LIBS analysis of complex materials.

  7. Detection of chlorine with concentration of 0.18 kg/m{sup 3} in concrete by laser-induced breakdown spectroscopy

    SciTech Connect

    Sugiyama, K.; Fujii, T.; Matsumura, T.; Shiogama, Y.; Yamaguchi, M.; Nemoto, K.

    2010-05-01

    The chlorine concentration in concrete samples was measured by laser-induced breakdown spectroscopy (LIBS). One or two pulsed second harmonic Nd:YAG lasers ({lambda}=532 nm) were used for the generation of laser-induced breakdown, and an intensified CCD camera, spectrometer, and optical bundle fiber were used for spectral measurement. To maximize the spectral intensity of the chlorine fluorescence line at a wavelength of 837.59 nm, the time delay between laser irradiation and spectral measurement, the time delay between the two laser pulses in double-pulse measurement, and the gate width of the spectral measurement were optimized. The linear relationship between the spectral intensity of the chlorine fluorescence line and the chlorine concentration was verified for pressed samples with chlorine concentrations from 0.18 to 5.4 kg/m{sup 3}. The signal-to-noise ratio was higher than 2 for the sample with a chlorine concentration of 0.18 kg/m{sup 3} (0.008 wt. %). Thus, a chlorine concentration of 0.6 kg/m{sup 3}, at which the reinforcing bars in concrete structures start to corrode, can be detected. These results show that LIBS is effective for the quantitative measurement of chlorine concentration in concrete with high sensitivity.

  8. Effective desynchronization with a resetting pulse train followed by a single pulse

    NASA Astrophysics Data System (ADS)

    Tass, P. A.

    2001-07-01

    A combined pulse train, single-pulse stimulation technique is presented here which makes it possible to effectively desynchronize a cluster of globally coupled phase oscillators in the presence of noise. Such a composite stimulus consists of a resetting short periodic high-frequent pulse train followed by a desynchronizing single pulse. The pulse train entrains and, thus, restarts the collective oscillation independently of its initial dynamic state. With a fixed delay after the pulse train, a single pulse is delivered which desynchronizes the cluster by hitting it in a vulnerable state. After the desynchronization the cluster wants to become synchronized again since the incoherent state is unstable. Nevertheless, repeated administration of the same composite stimulus blocks the resynchronization. Compared to double-pulse phase resetting and with regard to neurological applications, this method is particularly mild and can be applied to effectively maintain incoherency in a population of oscillatory neurons that tend to synchronize their firing. The composite stimulation approach sheds new light on the mechanism of standard deep brain stimulation and suggests an improved, milder and demand-controlled deep brain stimulation technique for patients with Parkinson's disease or essential tremor.

  9. Synchronous Use of IR and UV Laser Pulses in the Removal of Encrustation: Mechanistic Aspects, Discoloration Phenomena and Benefits

    NASA Astrophysics Data System (ADS)

    Zafiropulos, V.; Pouli, P.; Kylikoglou, V.; Maravelaki-Kalaitzaki, P.; Luk'yanchuk, B. S.; Dogariu, A.

    The removal of encrustation from sculptures and monuments has been by far the most pronounced application of lasers in LACONA field. Considerable effort has been put in recognizing the operative ablation mechanisms when using different laser wavelengths and power levels, as well as in understanding the associated "yellowing" phenomenon. The deeper insight into the laser-matter interactions for different laser parameters as well as the understanding of side discoloration phenomena has led us in combining IR and UV laser pulses with excellent results. More specifically, the fundamental and the third harmonic of a Q-Switched Nd:YAG laser has been spatially and temporally combined to create a double pulse. The power levels must be fixed at a certain ratio for the two wavelengths in such a way, that the different operative removal mechanisms (mainly selective vaporization for IR- and spallation for UV-pulses) take action at the same depth from the surface of encrustation. The resulted surface after the final removal of encrustation lacks the yellowish hue, which is present when only IR pulses are used. A theoretical model has been applied to account for the different phenomena observed with the synchronous use of laser pulses as well as the absence of yellowing. This novel methodology has been applied to Parthenon West Frieze with success (see parallel case study contribution by Pouli et al.).

  10. Gas and metal vapor lasers and applications; Proceedings of the Meeting, Los Angeles, CA, Jan. 22, 23, 1991

    NASA Astrophysics Data System (ADS)

    Kim, Jin J.; Tittel, Frank K.

    Various papers on gas and metal vapor lasers and applications are presented. Individual topics addressed include: high-power copper vapor laser development, modified off-axis unstable resonator for copper vapor laser, industrial applications of metal vapor lasers, newly developed excitation circuit for kHz pulsed lasers, copper vapor laser precision processing, development of solid state pulse power supply for copper vapor laser, multiple spectral structure of the 578.2-nm line for copper vapor laser, adsorption of bromine in CuBr laser, processing of polytetrafluoroethylene with high-power VUV laser radiation, characterization of a subpicosecond XeF(C - A) excimer laser, X-ray preionization for high-repetition-rate discharge excimer lasers. Also discussed are: investigation of microwave-pumped excimer and rare-gas laser transitions, influence of gas composition of XeCl laser performance, output power stabilization of a XeCl excimer laser by HCl gas injection, excimer laser machining of optical fiber taps, diagnostics of a compact UV-preionized XeCl laser with BCl3 halogen donor, blackbody-pumped CO32 lasers using Gaussian and waveguide cavities, chemical problems of high-power sealed-off CO lasers, laser action of Xe and Ne pumped by electron beam, process monitoring during CO2 laser cutting, double-pulsed TEA CO2 laser, superhigh-gain gas laser, high-power ns-pulse iodine laser provided with SBS mirror. (No individual items are abstracted in this volume)

  11. Multidiagnostic analysis of ultrafast laser ablation of metals with pulse pair irradiation

    NASA Astrophysics Data System (ADS)

    Amoruso, S.; Bruzzese, R.; Wang, X.; O'Connell, G.; Lunney, J. G.

    2010-12-01

    Copper targets are irradiated in the ablation regime by pairs of equal, time-delayed collinear laser pulses separated on a timescale going from ≈2 ps to ≈2 ns. The ablation plume is characterized by ion probe diagnostic, fast imaging, and temporally and spatially resolved optical emission spectroscopy. The variation in the ablation efficiency with the delay between the pulses is analyzed by measuring the ablation crater profile with a contact profilometer. The second laser pulse modifies the characteristics of the plasma plume produced by the first pulse and the ablation efficiency. The different mechanisms involved in double pulse ultrafast laser ablation are identified and discussed. The experimental findings are interpreted in the frame of a simple model of the interaction of the second pulse with the nascent ablation plume produced by the first pulse. This model yields consistent and quantitative agreement with the experimental findings predicting the observed experimental trends of the ablation depth reduction and ion yield increase with the delay between the pulses, as well as the characteristic timescale of the observed changes. The possibility of controlling the characteristics of the plumes produced during ultrafast laser ablation via an efficient coupling of the energy of the second pulse to the various ablation components produced by the first pulse is of particular interest in ultrafast pulsed laser deposition and microprobe analyses of materials.

  12. Anoxia/high temperature double whammy during the Permian-Triassic marine crisis and its aftermath

    PubMed Central

    Song, Haijun; Wignall, Paul B.; Chu, Daoliang; Tong, Jinnan; Sun, Yadong; Song, Huyue; He, Weihong; Tian, Li

    2014-01-01

    The Permian-Triassic mass extinction was the most severe biotic crisis in the past 500 million years. Many hypotheses have been proposed to explain the crisis, but few account for the spectrum of extinction selectivity and subsequent recovery. Here we show that selective losses are best accounted for by a combination of lethally warm, shallow waters and anoxic deep waters that acted to severely restrict the habitable area to a narrow mid-water refuge zone. The relative tolerance of groups to this double whammy provides the first clear explanation for the selective extinction losses during this double-pulsed crisis and also the fitful recovery. Thus, high temperature intolerant shallow-water dwellers, such as corals, large foraminifers and radiolarians were eliminated first whilst high temperature tolerant ostracods thrived except in anoxic deeper-waters. In contrast, hypoxia tolerant but temperature intolerant small foraminifers were driven from shallow-waters but thrived on dysoxic slopes margins. Only those mollusc groups, which are tolerant of both hypoxia and high temperatures, were able to thrive in the immediate aftermath of the extinction. Limited Early Triassic benthic recovery was restricted to mid-water depths and coincided with intervals of cooling and deepening of water column anoxia that expanded the habitable mid-water refuge zone. PMID:24549265

  13. Wavelength dependence on the forensic analysis of glass by nanosecond 266 nm and 1064 nm laser induced breakdown spectroscopy

    SciTech Connect

    Cahoon, Erica M.; Almirall, Jose R.

    2010-05-01

    Laser induced breakdown spectroscopy can be used for the chemical characterization of glass to provide evidence of an association between a fragment found at a crime scene to a source of glass of known origin. Two different laser irradiances, 266 nm and 1064 nm, were used to conduct qualitative and quantitative analysis of glass standards. Single-pulse and double-pulse configurations and lens-to-sample-distance settings were optimized to yield the best laser-glass coupling. Laser energy and acquisition timing delays were also optimized to result in the highest signal-to-noise ratio corresponding to the highest precision and accuracy. The crater morphology was examined and the mass removed was calculated for both the 266 nm and 1064 nm irradiations. The analytical figures of merit suggest that the 266 nm and 1064 nm wavelengths are capable of good performance for the forensic chemical characterization of glass. The results presented here suggest that the 266 nm laser produces a better laser-glass matrix coupling, resulting in a better stoichiometric representation of the glass sample. The 266 nm irradiance is therefore recommended for the forensic analysis and comparison of glass samples.

  14. Application of Laser Induced Breakdown Spectroscopy to the identification of emeralds from different synthetic processes

    NASA Astrophysics Data System (ADS)

    Agrosì, G.; Tempesta, G.; Scandale, E.; Legnaioli, S.; Lorenzetti, G.; Pagnotta, S.; Palleschi, V.; Mangone, A.; Lezzerini, M.

    2014-12-01

    Laser Induced Breakdown Spectroscopy can provide a useful contribution in mineralogical field in which the quantitative chemical analyses (including the evaluation of light elements) can play a key role in the studies on the origin of the emeralds. In particular, the chemical analyses permit to determine those trace elements, known as fingerprints, that can be useful to study their provenance. This technique, not requiring sample preparation results particularly suitable for gemstones, that obviously must be studied in a non-destructive way. In this paper, the LIBS technique was applied to distinguish synthetic emeralds grown by Biron hydrothermal method from those grown by Chatham flux method. The analyses performed by collinear double-pulse LIBS give a signal enhancement useful for the quantitative chemical analyses while guaranteeing a minimal sample damage. In this way it was obtained a considerable improvement on the detection limit of the trace elements, whose determination is essential for determining the origin of emerald gemstone. The trace elements V, Cr, and Fe and their relative amounts allowed the correct attribution of the manufacturer. Two different methods for quantitative analyses were used for this study: the standard Calibration-Free LIBS (CF-LIBS) method and its recent evolution, the One Point Calibration LIBS (OPC-LIBS). This is the first approach to the evaluation of the emerald origin by means of the LIBS technique.

  15. Voltage-independent inhibition of Ca(V)2.2 channels is delimited to a specific region of the membrane potential in rat SCG neurons.

    PubMed

    Vivas, Oscar; Arenas, Isabel; García, David E

    2012-06-01

    Neurotransmitters and hormones regulate Ca(V)2.2 channels through a voltage-independent pathway which is not well understood. It has been suggested that this voltage-independent inhibition is constant at all membrane voltages. However, changes in the percent of voltage-independent inhibition of Ca(V)2.2 have not been tested within a physiological voltage range. Here, we used a double-pulse protocol to isolate the voltage-independent inhibition of Ca(V)2.2 channels induced by noradrenaline in rat superior cervical ganglion neurons. To assess changes in the percent of the voltage-independent inhibition, the activation voltage of the channels was tested between -40 and +40 mV. We found that the percent of voltage-independent inhibition induced by noradrenaline changed with the activation voltage used. In addition, voltage-independent inhibition induced by oxo-M, a muscarinic agonist, exhibited the same dependence on activation voltage, which supports that this pattern is not exclusive for adrenergic activation. Our results suggested that voltage-independent inhibition of Ca(V)2.2 channels depends on the activation voltage of the channel in a physiological voltage range. This may have relevant implications in the understanding of the mechanism involved in voltage-independent inhibition.

  16. Single-shot laser pulse reconstruction based on self-phase modulated spectra measurements

    PubMed Central

    Anashkina, Elena A.; Ginzburg, Vladislav N.; Kochetkov, Anton A.; Yakovlev, Ivan V.; Kim, Arkady V.; Khazanov, Efim A.

    2016-01-01

    We report a method for ultrashort pulse reconstruction based only on the pulse spectrum and two self-phase modulated (SPM) spectra measured after pulse propagation through thin media with a Kerr nonlinearity. The advantage of this method is that it is a simple and very effective tool for characterization of complex signals. We have developed a new retrieval algorithm that was verified by reconstructing numerically generated fields, such as a complex electric field of double pulses and few-cycle pulses with noises, pedestals and dips down to zero spectral intensity, which is challenging for commonly used techniques. We have also demonstrated a single-shot implementation of the technique for the reconstruction of experimentally obtained pulses. This method can be used for high power laser systems operating in a single-shot mode in the optical, near- and mid-IR spectral ranges. The method is robust, low cost, stable to noise, does not require a priori information, and has no ambiguity related to time direction. PMID:27646027

  17. Fresh-slice multicolour X-ray free-electron lasers

    NASA Astrophysics Data System (ADS)

    Lutman, Alberto A.; Maxwell, Timothy J.; MacArthur, James P.; Guetg, Marc W.; Berrah, Nora; Coffee, Ryan N.; Ding, Yuantao; Huang, Zhirong; Marinelli, Agostino; Moeller, Stefan; Zemella, Johann C. U.

    2016-11-01

    X-ray free-electron lasers (XFELs) provide femtosecond X-ray pulses with a narrow energy bandwidth and unprecedented brightness. Ultrafast physical and chemical dynamics, initiated with a site-specific X-ray pulse, can be explored using XFELs with a second ultrashort X-ray probe pulse. However, existing double-pulse schemes are complicated, difficult to customize or provide only low-intensity pulses. Here we present the novel fresh-slice technique for multicolour pulse production, wherein different temporal slices of an electron bunch lase to saturation in separate undulator sections. This method combines electron bunch tailoring from a passive wakefield device with trajectory control to provide multicolour pulses. The fresh-slice scheme outperforms existing techniques at soft X-ray wavelengths. It produces femtosecond pulses with a power of tens of gigawatts and flexible colour separation. The pulse delay can be varied from temporal overlap to almost one picosecond. We also demonstrate the first three-colour XFEL and variably polarized two-colour pulses.

  18. Ultra-Shallow P{sup +}/N Junction Formation in Si Using Low Temperature Solid Phase Epitaxy Assisted with Laser Activation

    SciTech Connect

    Hara, Shuhei; Tanaka, Yuki; Fukaya, Takumi; Matsumoto, Satoru; Suzuki, Toshiharu; Fuse, Genshu; Kudo, Toshio; Sakuragi, Susumu

    2008-11-03

    A combination of Ge pre-amorphization implantation (Ge-PAI), low-energy B implantation and laser annealing is a promising method to form highly-activated, abrupt and ultra-shallow junctions (USJ). In our previous report of IIT 2006, we succeeded in forming pn junctions less than 10 nm using non-melt double-pulsed green laser. However, a large leakage current under reverse bias was observed consequently due to residual defects in the implanted layer. In this study, a method to form USJ is proposed: a combination of low-temperature solid phase epitaxy and non-melt laser irradiation for B activation. Ge pre-amorphization implantation was performed at energy of 6 keV with a dose of 3x10{sup 14}/cm{sup 2}. Then B implantation was performed at energy of 0.2 keV with a dose of 1.2x10{sup 15}/cm{sup 2}. Samples were annealed at 400 deg. C for 10 h in nitrogen atmosphere. Subsequently, non-melt laser irradiation was performed at energy of 690 mJ/cm{sup 2} and pulse duration of 100 ns with intervals of 300 ns. As a result, USJ around 10 nm with better crystallinity was successfully formed. And the leakage current of pn diodes was reduced significantly. Moreover, it is proven from secondary ion mass spectroscopy (SIMS) analysis that transient enhanced diffusion (TED) of B is specifically suppressed.

  19. The matrix formalism for generalised gradients with time-varying orientation in diffusion NMR.

    PubMed

    Drobnjak, Ivana; Zhang, Hui; Hall, Matt G; Alexander, Daniel C

    2011-05-01

    The matrix formalism is a general framework for evaluating the diffusion NMR signal from restricted spins under generalised gradient waveforms. The original publications demonstrate the method for waveforms that vary only in magnitude and have fixed orientation. In this work, we extend the method to allow for variations in the direction of the gradient. This extension is necessary, for example to incorporate the effects of crusher gradients or imaging gradients in diffusion MRI, to characterise signal anisotropy in double pulsed field gradient (dPFG) experiments, or to optimise the gradient waveform for microstructure sensitivity. In particular, we show for primitive geometries (planes, cylinders and spheres), how to express the matrix operators at each time point of the gradient waveform as a linear combination of one or two fundamental matrices. Thus we obtain an efficient implementation with both the storage and CPU demands similar to the fixed-orientation case. Comparison with Monte Carlo simulations validates the implementation on three different sequences: dPFG, helical waveforms and the stimulated echo (STEAM) sequence.

  20. Temporal interaction in electrical hearing elucidates auditory nerve dynamics in humans.

    PubMed

    Karg, S A; Lackner, C; Hemmert, W

    2013-05-01

    In cochlear implants, severe limitations arise from electrical crosstalk between channels. Therefore, the current trend in cochlear implants is to increase stimulation rates to encode signals with higher temporal precision. However, the fundamental question: "What is the limit of temporal precision due to inherent neuronal dynamics of the stimulated neurons?" has not yet been resolved. In this study we have developed a double-pulse method and, for the first time, reversed stimulus polarity systematically between consecutive pulses to elucidate subthreshold-induced temporal interaction effects. This method allowed us to determine the time-course of subthreshold temporal interaction in human subjects which identifies the limits of encoded temporal precision. Our results show significant temporal interaction up to 600 μs inter-pulse interval. In all the cases tested we saw a facilitation effect on threshold. Interaction effects at a 20% below threshold pre-conditioning stimulation showed up to 38% ± 6% threshold reduction. These results imply that there is significant temporal interaction between two subsequent pulses. This interaction diminishes the precision of amplitude coding. We predict interaction effects on temporal precision and channel interaction. For (interleaved) stimulation with short inter-pulse intervals it is interesting to consider our interaction results; and it may become important to consider them for future coding strategies where high temporal precision is required. In an increasing group of binaural implanted patients this will be the case when interaural time differences are encoded with μs precision.

  1. Development of the Lidar Atmospheric Sensing Experiment (LASE): An Advanced Airborne DIAL Instrument

    NASA Technical Reports Server (NTRS)

    Moore, Alvah S., Jr.; Brown, Kevin E.; Hall, William M.; Barnes, James C.; Edwards, William C.; Petway, Larry B.; Little, Alan D.; Luck, William S., Jr.; Jones, Irby W.; Antill, Charles W., Jr.

    1997-01-01

    The Lidar Atmospheric Sensing Experiment (LASE) Instrument is the first fully-engineered, autonomous Differential Absorption Lidar (DIAL) System for the measurement of water vapor in the troposphere (aerosol and cloud measurements are included). LASE uses a double-pulsed Ti:Sapphire laser for the transmitter with a 30 ns pulse length and 150 mJ/pulse. The laser beam is "seeded" to operate on a selected water vapor absorption line in the 815-nm region using a laser diode and an onboard absorption reference cell. A 40 cm diameter telescope collects the backscattered signals and directs them onto two detectors. LASE collects DIAL data at 5 Hz while onboard a NASA/Ames ER-2 aircraft flying at altitudes from 16-21 km. LASE was designed to operate autonomously within the environment and physical constraints of the ER-2 aircraft and to make water vapor profile measurements across the troposphere to better than 10% accuracy. LASE has flown 19 times during the development of the instrument and the validation of the science data. This paper describes the design, operation, and reliability of the LASE Instrument.

  2. Four Pulse Drive System for the Beam Induction Cells for DARHT Axis 2

    SciTech Connect

    Downing, J.; Carlson, R.; Melton, J.; Fockler, J.

    1999-06-28

    The proposed drive system allows for the generation of up to four (4) high-quality radiographic pulses along one line-of-sight, having arbitrary pulse spacing ({approximately}500 ns), using demonstrated technologies. This concept uses a four-pulse drive system to drive both a 16-MeV ensemble of 250-kV, 4-kA induction cells and a four-pulse, 4-MeV injector. The key to this approach lies in the method used to combine four pulses from different generators in a manner that does not compromise the voltage flatness requirement of {+-} 1%. The induction cells use core material for only a single pulse. A simple reverse bias circuit is used to reset the cores between pulses, and the insulator has been redesigned to withstand the reverse reset voltage. This approach can be installed in stages so that the facility can be used for dual axis radiography while implementing the multi-pulsing capability. A dual double-pulse format has been identified which provides a sequence of two pulses along one line-of-sight within a 2-{micro}sec window. The 2-{micro}sec windows can be separated by arbitrary time intervals of 2- to 10-{micro}sec.

  3. Generation and diagnostics of pulsed intense ion beams with an energy density of 10 J/cm².

    PubMed

    Isakova, Yu; Pushkarev, A; Khailov, I; Zhong, H

    2015-07-01

    The paper presents the results of a study on transportation and focusing of a pulsed ion beam at gigawatt power level, generated by a diode with explosive-emission cathode. The experiments were carried out with the TEMP-4M accelerator operating in double-pulse mode: the first pulse is of negative polarity (500 ns, 100-150 kV), and this is followed by a second pulse of positive polarity (120 ns, 200-250 kV). To reduce the beam divergence, we modified the construction of the diode. The width of the anode was increased compared to that of the cathode. We studied different configurations of planar and focusing strip diodes. It was found that the divergence of the ion beam formed by a planar strip diode, after construction modification, does not exceed 3° (half-angle). Modification to the construction of a focusing diode made it possible to reduce the beam divergence from 8° to 4°-5°, as well as to increase the energy density at the focus up to 10-12 J/cm(2), and decrease the shot to shot variation in the energy density from 10%-15% to 5%-6%. When measuring the ion beam energy density above the ablation threshold of the target material (3.5-4 J/cm(2)), we used a metal mesh with 50% transparency to lower the energy density. The influence of the metal mesh on beam transport has been studied.

  4. Generation and diagnostics of pulsed intense ion beams with an energy density of 10 J/cm2

    NASA Astrophysics Data System (ADS)

    Isakova, Yu.; Pushkarev, A.; Khailov, I.; Zhong, H.

    2015-07-01

    The paper presents the results of a study on transportation and focusing of a pulsed ion beam at gigawatt power level, generated by a diode with explosive-emission cathode. The experiments were carried out with the TEMP-4M accelerator operating in double-pulse mode: the first pulse is of negative polarity (500 ns, 100-150 kV), and this is followed by a second pulse of positive polarity (120 ns, 200-250 kV). To reduce the beam divergence, we modified the construction of the diode. The width of the anode was increased compared to that of the cathode. We studied different configurations of planar and focusing strip diodes. It was found that the divergence of the ion beam formed by a planar strip diode, after construction modification, does not exceed 3° (half-angle). Modification to the construction of a focusing diode made it possible to reduce the beam divergence from 8° to 4°-5°, as well as to increase the energy density at the focus up to 10-12 J/cm2, and decrease the shot to shot variation in the energy density from 10%-15% to 5%-6%. When measuring the ion beam energy density above the ablation threshold of the target material (3.5-4 J/cm2), we used a metal mesh with 50% transparency to lower the energy density. The influence of the metal mesh on beam transport has been studied.

  5. Analysis of 100-lb(sub f) (445-N) LO2-LCH4 Reaction Control Engine Impulse Bit Performance

    NASA Technical Reports Server (NTRS)

    Marshall, William M.; Klenhenz, Julie E.

    2012-01-01

    Recently, liquid oxygen-liquid methane (LO2-LCH4) has been considered as a potential green propellant alternative for future exploration missions. The Propulsion and Cryogenic Advanced Development (PCAD) project was tasked by NASA to develop this propulsion combination to enable safe and cost-effective exploration missions. To date, limited experience with such combinations exist, and as a result a comprehensive test program is critical to demonstrating with the viability of implementing such a system. The NASA Glenn Research Center conducted a test program of a 100-lbf (445-N) reaction control engine (RCE) at the Center s Altitude Combustion Stand (ACS), focusing on altitude testing over a wide variety of operational conditions. The ACS facility includes unique propellant conditioning feed systems (PCFS), which allow precise control of propellant inlet conditions to the engine. Engine performance as a result of these inlet conditions was examined extensively during the test program. This paper is a companion to the previous specific impulse testing paper, and discusses the pulsed-mode operation portion of testing, with a focus on minimum impulse bit (MIB) and repeatable pulse performance. The engine successfully demonstrated target MIB performance at all conditions, as well as successful demonstration of repeatable pulse widths. Some anomalous conditions experienced during testing are also discussed, including a double pulse phenomenon, which was not noted in previous test programs for this engine.

  6. Transcranial magnetic stimulation disrupts the perception and embodiment of facial expressions.

    PubMed

    Pitcher, David; Garrido, Lúcia; Walsh, Vincent; Duchaine, Bradley C

    2008-09-03

    Theories of embodied cognition propose that recognizing facial expressions requires visual processing followed by simulation of the somatovisceral responses associated with the perceived expression. To test this proposal, we targeted the right occipital face area (rOFA) and the face region of right somatosensory cortex (rSC) with repetitive transcranial magnetic stimulation (rTMS) while participants discriminated facial expressions. rTMS selectively impaired discrimination of facial expressions at both sites but had no effect on a matched face identity task. Site specificity within the rSC was demonstrated by targeting rTMS at the face and finger regions while participants performed the expression discrimination task. rTMS targeted at the face region impaired task performance relative to rTMS targeted at the finger region. To establish the temporal course of visual and somatosensory contributions to expression processing, double-pulse TMS was delivered at different times to rOFA and rSC during expression discrimination. Accuracy dropped when pulses were delivered at 60-100 ms at rOFA and at 100-140 and 130-170 ms at rSC. These sequential impairments at rOFA and rSC support embodied accounts of expression recognition as well as hierarchical models of face processing. The results also demonstrate that nonvisual cortical areas contribute during early stages of expression processing.

  7. Beamed Energy Propulsion: Research Status And Needs--Part 1

    SciTech Connect

    Birkan, Mitat

    2008-04-28

    One promising solution to the operationally responsive space is the application of remote electromagnetic energy to propel a launch vehicle into orbit. With beamed energy propulsion, one can leave the power source stationary on the ground or space, and direct heat propellant on the spacecraft with a beam from a fixed station. This permits the spacecraft to leave its power source at home, saving significant amounts of mass, greatly improving performance. This concept, which removes the mass penalty of carrying the propulsion energy source on board the vehicle, was first proposed by Arthur Kantrowitz in 1972; he invoked an extremely powerful ground based laser. The same year Michael Minovich suggested a conceptually similar 'in-space' laser rocket system utilizing a remote laser power station. In the late 1980's, Air Force Office of Scientific Research (AFOSR) funded continuous, double pulse laser and microwave propulsion while Strategic Defense Initiative Office (SDIO) funded ablative laser rocket propulsion. Currently AFOSR has been funding the concept initiated by Leik Myrabo, repetitively pulsed laser propulsion, which has been universally perceived, arguably, to be the closest for mid-term applications. This 2-part paper examines the investment strategies in beamed energy propulsion and technical challenges to be overcome. Part 1 presents a world-wide review of beamed energy propulsion research, including both laser and microwave arenas.

  8. Beamed Energy Propulsion: Research Status And Needs--Part 2

    SciTech Connect

    Birkan, Mitat

    2008-04-28

    One promising solution to the operationally responsive space is the application of remote electromagnetic energy to propel a launch vehicle into orbit. With beamed energy propulsion, one can leave the power source stationary on the ground or space, and direct heat propellant on the spacecraft with a beam from a fixed station. This permits the spacecraft to leave its power source at home, saving significant amounts of mass, greatly improving performance. This concept, which removes the mass penalty of carrying the propulsion energy source on board the vehicle, was first proposed by Arthur Kantrowitz in 1972; he invoked an extremely powerful ground based laser. The same year Michael Minovich suggested a conceptually similar 'in-space' laser rocket system utilizing a remote laser power station. In the late 1980's, Air Force Office of Scientific Research (AFOSR) funded continuous, double pulse laser and microwave propulsion while Strategic Defense Initiative Office (SDIO) funded ablative laser rocket propulsion. Currently AFOSR has been funding the concept initiated by Leik Myrabo, repetitively pulsed laser propulsion, which has been universally perceived, arguably, to be the closest for mid-term applications. This 2-part paper examines the investment strategies in beamed energy propulsion and technical challenges to be covers Part 2 covers the present research status and needs.

  9. Diagnostics of Laser Produced Plume Under Carbon Nanotube Growth Conditions

    NASA Technical Reports Server (NTRS)

    Arepalli, Sivaram; Nikolaev, Pavel; Holmes, William; Scott, Carl D.

    1999-01-01

    This paper presents diagnostic data obtained from the plume of a graphite composite target during carbon nanotube production by the double-pulse laser oven method. The insitu emission spectrum (300 to 650 nm) is recorded at different locations upstream of the target and at different delay times from the lasers (IR and green). Spectral features are identified as emissions from C2 (Swan System: a (sup 3)pi(sub g) - delta (sup 3)pi(sub u) and C3 (Comet Head System: A (sup 1)pi(sub u) - chi (sup 1)sigma(sub u) (sup +). Experimental spectra are compared with computed spectra to estimate vibrational temperatures of excited state C2 in the range of 2500 to 4000 kappa The temporal evolution of the 510 nm band of C2 is monitored for two target positions in various locations which shows confinement of the plume in the inner tube and increase in plume velocity with temperature. The excitation spectra of C2 are obtained by using a dye laser to pump the (0,1) transition of the Swan System and collecting the Laser Induced Fluorescence signal from C2 These are used to obtain "ground-state" rotational and vibrational temperatures which are close to the oven temperature. Images of the plume are also collected and are compared with the spectral measurements.

  10. Two-colour hard X-ray free-electron laser with wide tunability.

    PubMed

    Hara, Toru; Inubushi, Yuichi; Katayama, Tetsuo; Sato, Takahiro; Tanaka, Hitoshi; Tanaka, Takashi; Togashi, Tadashi; Togawa, Kazuaki; Tono, Kensuke; Yabashi, Makina; Ishikawa, Tetsuya

    2013-01-01

    Ultrabrilliant, femtosecond X-ray pulses from X-ray free-electron lasers (XFELs) have promoted the investigation of exotic interactions between intense X-rays and matters, and the observation of minute targets with high spatio-temporal resolution. Although a single X-ray beam has been utilized for these experiments, the use of multiple beams with flexible and optimum beam parameters should drastically enhance the capability and potentiality of XFELs. Here we show a new light source of a two-colour double-pulse (TCDP) XFEL in hard X-rays using variable-gap undulators, which realizes a large and flexible wavelength separation of more than 30% with an ultraprecisely controlled time interval in the attosecond regime. Together with sub-10-fs pulse duration and multi-gigawatt peak powers, the TCDP scheme enables us to elucidate X-ray-induced ultrafast transitions of electronic states and structures, which will significantly contribute to the advancement of ultrafast chemistry, plasma and astronomical physics, and quantum X-ray optics.

  11. Summary of Altitude Pulse Testing of a 100-lbf L02/LCH4 Reaction Control Engine

    NASA Technical Reports Server (NTRS)

    Marshall, William M.; Kleinhenz, Julie E.

    2011-01-01

    Recently, liquid oxygen-liquid methane (LO2/LCH4) has been considered as a potential "green" propellant alternative for future exploration missions. The Propulsion and Cryogenic Advanced Development (PCAD) project has been tasked by NASA to develop this propulsion combination to enable safe and cost effective exploration missions. To date, limited experience with such combinations exist, and as a result a comprehensive test program is critical to demonstrating the viability of implementing such a system. The NASA Glenn Research Center has conducted a test program of a 100-lbf (445-N) reaction control engine (RCE) at the center s Altitude Combustion Stand (ACS), focusing on altitude testing over a wide variety of operational conditions. The ACS facility includes a unique propellant conditioning feed system (PCFS) which allows precise control of propellant inlet conditions to the engine. Engine performance as a result of these inlet conditions was examined extensively during the test program. This paper is a companion to the previous specific impulse testing paper, and discusses the pulsed mode operation portion of testing, with a focus on minimum impulse bit (I-bit) and repeatable pulse performance. The engine successfully demonstrated target minimum impulse bit performance at all conditions, as well as successful demonstration of repeatable pulse widths. Some anomalous conditions experienced during testing are also discussed, including a double pulse phenomenon which was not noted in previous test programs for this engine.

  12. Dependence of Nociceptive Detection Thresholds on Physiological Parameters and Capsaicin-Induced Neuroplasticity: A Computational Study

    PubMed Central

    Yang, Huan; Meijer, Hil G. E.; Doll, Robert J.; Buitenweg, Jan R.; van Gils, Stephan A.

    2016-01-01

    Physiological properties of peripheral and central nociceptive subsystems can be altered over time due to medical interventions. The effective change for the whole nociceptive system can be reflected in changes of psychophysical characteristics, e.g., detection thresholds. However, it is challenging to separate contributions of distinct altered mechanisms with measurements of thresholds only. Here, we aim to understand how these alterations affect Aδ-fiber-mediated nociceptive detection of electrocutaneous stimuli. First, with a neurophysiology-based model, we study the effects of single-model parameters on detection thresholds. Second, we derive an expression of model parameters determining the functional relationship between detection thresholds and the interpulse interval for double-pulse stimuli. Third, in a case study with topical capsaicin treatment, we translate neuroplasticity into plausible changes of model parameters. Model simulations qualitatively agree with changes in experimental detection thresholds. The simulations with individual forms of neuroplasticity confirm that nerve degeneration is the dominant mechanism for capsaicin-induced increases in detection thresholds. In addition, our study suggests that capsaicin-induced central plasticity may last at least 1 month. PMID:27252644

  13. Interaction of nitroimidazole sensitizers and oxygen in the radiosensitization of mammalian cells at ultrahigh dose rates

    SciTech Connect

    Michaels, H.B.; Ling, C.C.; Epp, E.R.; Peterson, E.C.

    1981-03-01

    When CHO cells, equilibrated with 0.44% oxygen, are irradiated with single 3-nsec pulses of electrons from a 600-kV-field emission source, a breaking survival curve is observed. The breaking behavior, believed to be the result of radiolytic oxygen depletion, can be prevented by the presence of a relatively low concentration of the hypoxic cell sensitizer misonidazole; similar results are obtained with metronidazole and Ro-05-9963. The resulting survival curves exhibit a sensitized response similar to that obtained with conventional dose rate radiation for CHO cells under this oxygen concentration. This degree of sensitization is greater than that observed for CHO cells irradiated at ultrahigh dose rates under the same concentration of sensitizer in nitrogen. The data suggest that the nitroimidazole compounds interfere with the radiation chemical oxygen depletion process and that the radiosensitization observed in the nonbreaking survival curve is the consequence of sensitization by both the nitroimidazole and, primarily, the oxygen rather than a direct subsitution for oxygen by the sensitizer. This conclusion is also supported by data obtained in double-pulse experiments. The results are discussed with regard to the mechanisms of the oxygen depletion process and radiosensitization.

  14. A methodology for laser diagnostics in large-bore marine two-stroke diesel engines

    NASA Astrophysics Data System (ADS)

    Hult, J.; Mayer, S.

    2013-04-01

    Large two-stroke diesel engines for marine propulsion offer several challenges to successful implementation of the laser diagnostic techniques applied extensively in smaller automotive engines. For this purpose a fully operational large-bore engine has been modified to allow flexible optical access, through 24 optical ports with clear diameters of 40 mm. By mounting the entire optical set-up directly to the engine, effects of the vigorous vibrations and thermal drifts on alignment can be minimized. Wide-angle observation and illumination, as well as relatively large aperture detection, is made possible through mounting of optical modules and relays inside optical ports. This allows positioning of the last optical element within 10 mm from the cylinder wall. Finally, the implementation on a multi-cylinder engine allows for flexible and independent operation of the optically accessible cylinder for testing purposes. The performance of the integrated optical engine and imaging system developed is demonstrated through laser Mie scattering imaging of fuel jet structures, from which information on liquid penetration and spray angles can be deduced. Double pulse laser-sheet imaging of native in-cylinder structures is also demonstrated, for the purpose of velocimetry.

  15. A low frequency study of PSRs B1133+16, B1112+50, and B0031-07

    NASA Astrophysics Data System (ADS)

    Karuppusamy, R.; Stappers, B. W.; Serylak, M.

    2011-01-01

    We use the low frequency (110-180 MHz) capabilities of the Westerbork Synthesis Radio Telescope (WSRT) to characterise a large collection of single pulses from three low magnetic field pulsars. Using the Pulsar Machine II (PuMa-II) to acquire and coherently dedisperse the pulsar signals, we examine whether the bright pulses observed in these pulsars are related to the classical giant pulse emission. Giant pulses are reported from PSR B1112+50 and bright pulses from the PSRs B1133+16 and B0031-07. These pulsars also exhibit large intensity modulations observed as rapid changes in the single pulse intensity. Evidence of global magnetospheric effects is provided by our detection of bright double pulses in PSRs B0031-07 and B1133+16. Using the multi-frequency observations, we accurately determine the dispersion measures (4.844 ± 0.002 for B1133+16 and 9.1750 ± 0.0001 for B1112+50), derive the radio emission height in PSR B1133+16 and report on the properties of subpulse drift modes in these pulsars. We also find that these pulsars show a much larger intensity modulation at low sky frequencies resulting in narrow and bright emissions.

  16. Development of a laser-induced breakdown spectroscopy method for soil and ecological analysis (review)

    NASA Astrophysics Data System (ADS)

    Burakov, V. S.; Raikov, S. N.; Tarasenko, N. V.; Belkov, M. V.; Kiris, V. V.

    2010-11-01

    The application of laser spectrochemical analysis to testing for basic compounds and nutritious/toxic elements in soil has been reviewed. A combined laser-spark approach has been applied for the rapid measurement of the carbon content in soil. Spectra have been excited both directly in a laser-ablation plume and by passing a pulsed electric discharge through the plume. The emission spectrum intensity in the combined plasma is considerably higher. The application of a complex of methods to carbon determination in soil has shown that in fact the data on the humus content usually obtained in agrochemical practice by a conventional method of carbon oxidation by potassium dichromate need to be corrected taking into account the possibility of incomplete oxidation of organic matter in soil. The efficiency of various double-pulse LIBS applications has been demonstrated in solving a number of environmental problems such as the determination of heavy and toxic metals in soil and the detection of sulfur in coal. The instrumentation and analytical procedures have been proposed and optimized for rapid control of the chlorine content in plant samples. The technique can be easily extended to ecological monitoring of toxic elements and heavy metals in any biogenic material.

  17. Laser Induced Breakdown Spectroscopy application for ash characterisation for a coal fired power plant

    NASA Astrophysics Data System (ADS)

    Ctvrtnickova, T.; Mateo, M. P.; Yañez, A.; Nicolas, G.

    2010-08-01

    The aim of this work was to apply the LIBS technique for the analysis of fly ash and bottom ash resulting from the coal combustion in a coal fired power plant. The steps of presented LIBS analysis were pelletizing of powdered samples, firing with laser and spectroscopic detection. The analysis "on tape" was presented as an alternative fast sampling approach. This procedure was compared with the usual steps of normalized chemical analysis methods for coal which are coal calcination, fluxing in high temperature plasma, dilution in strong acids and analyzing by means of ICP-OES and/or AAS. First, the single pulse LIBS approach was used for determination and quantification of elemental content in fly ash and bottom ash on the exit of the boiler. For pellet preparation, ash has to be mixed with proper binder to assure the sample resistance. Preparation of the samples (binder selection and pressing/pelletizing conditions) was determined and LIBS experimental conditions optimized. No preparation is necessary in "on tape" sampling. Moreover, double-pulse approach in orthogonal reheating configuration was applied to enhance the repeatability and precision of the LIBS results and to surpass the matrix effect influencing the calibration curves in case of some elements. Obtained results showed that LIBS responses are comparable to the normalized analytical methods. Once optimized the experimental conditions and features, application of LIBS may be a promising technique for combustion process control even in on-line mode.

  18. Effect of temperature on acoustic communication: sound production in the croaking gourami (labyrinth fishes).

    PubMed

    Ladich, Friedrich; Schleinzer, Günter

    2015-04-01

    Sound communication comprising the production and detection of acoustic signals is affected by ambient temperature in ectothermic animals. In the present study we investigated the effects of temperature on sound production and characteristics in the croaking gourami Trichopsis vittata, a freshwater fish from Southeast Asia possessing a highly specialized sound-generating mechanism found only in a single genus. The croaking gourami produces pulsed sounds by stretching and plucking two enhanced pectoral fin tendons during rapid pectoral fin beating. Croaking sounds typically consist of a series of double-pulsed bursts with main energies between 1 and 1.5 kHz. Sounds were recorded during dyadic contests between two males at three different temperatures (25°, 30° and 35°C). The mean dominant frequency increased with rising temperature from 1.18 to 1.33 kHz, whereas temporal characteristics decreased. The sound interval dropped from 492 to 259 ms, the burst period from 51 to 35 ms and the pulse period from 5.8 to 5.1 ms. In contrast, the number of sounds and number of bursts within a sound were not affected by temperature. The current study shows that spectral and temporal characteristics of sounds are affected in different ways by temperature in the croaking gourami, whereas the numbers of sounds and bursts remain unaffected. We conclude that acoustic communication in gouramis is affected by changes in ambient temperature.

  19. Range-resolved optical detection of honeybees by use of wing-beat modulation of scattered light for locating land mines

    NASA Astrophysics Data System (ADS)

    Hoffman, David S.; Nehrir, Amin R.; Repasky, Kevin S.; Shaw, Joseph A.; Carlsten, John L.

    2007-05-01

    An imaging lidar instrument with the capability of measuring the frequency response of a backscattered return signal up to 3.6 kHz is demonstrated. The instrument uses a commercial microchip frequency-doubled pulsed Nd:YAG laser with a 7.2 kHz pulse repetition rate, a pulse duration of less than 1 ns, and a pulse energy of greater than 10 μJ. A 15.2 cm commercial telescope is used to collect the backscattered signal, and a photomultiplier tube is used to monitor the scattered light. This instrument is designed for range- and angle-resolved optical detection of honeybees for explosives and land-mine detection. The instrument is capable of distinguishing between the scattered light from honeybees and other sources through the frequency content of the return signal caused by the wing-beat modulation of the backscattered light. Detection of honeybees near a bee hive and spatial mapping of honeybee densities near feeders are demonstrated.

  20. Nucleation and growth in electrodeposition of thin copper films on pyrolytic graphite

    SciTech Connect

    Kinaci, F.S.; Muller, R.H.

    1992-05-01

    Electrodeposition of Cu on graphite electrodes was studied, with emphasis on nucleation. Various ex-situ and in-situ methods were investigated for determining the number density of nuclei. Two direct methods were studied (scanning electron microscopy and scanning tunneling microscopy); indirect determinations included Raman spectroscopy and analysis of potentiostatic current transients. Though some of the techniques correctly predicted the nucleation densities under special conditions, SEM was the most reliable tool. The large scatter in the data necessitated steps to minimize this effect. To electrodeposit Cu on graphite, a nucleation overpotential of 250 mV was measured with cyclic voltammetry; such a large overpotential does not occur on a Pt or on a Cu-covered graphite electrode. The deposition potential is the dominant parameter governing nucleation density. There is a sharp increase in the nucleation density with applied potential. Cu can be deposited on highly oriented pyrolytic graphite only between the nucleation overpotential and the hydrogen evolution potential. To increase the Cu nucleation density, while avoiding excessive H evolution, a double pulse potential technique was used; nucleation densities on the order of 10{sup 10} nuclei/cm{sup 2} were achieved. The use of inhibitors (PVA, benzotriazole) was also investigated. Deposition on conducting polymer electrodes was also studied; initial results with polyaniline show promise. 57 figs, 6 tabs, refs. (DLC)

  1. Status of the Ablative Laser Propulsion Studies

    NASA Technical Reports Server (NTRS)

    Herren, Kenneth A.; Lin, Jun; Cohen, Tinothy; Pakhomov, Andrew V.; Thompson, M. Shane

    2004-01-01

    We present a short review of our laser-propulsion research as well as some of the current results of the Ablative Laser Propulsion (ALP) studies currently underway at the University of Alabama in Huntsville. It has been shown that direct surface ablation of a solid material produces high specific impulse (Isp) at relatively high energy conversion efficiency (20 - 40%). We detail measurements of specific impulse, thrust and coupling coefficients for elemental target materials both with single and with double pulse laser shots. We also present measurements taken using three independent methods for determination of Isp. The three methods produce consistent values from ion time-of-flight technique, impulse measurements and imaging of the expansion front of plasma plume. We present a demonstration of our ALP lightcraft, a small free-flying micro-vehicle that is propelled by ablation. For ALP lightcraft we use a subscale thin shell of nickel replicated over a diamond turned mandrel that produces a highly polished self-focusing, truncated at the focus parabolic mirror. The mass of the lightcraft is 54 mg and it is driven by 100-ps wide, 35-mJ laser pulses at 532 nm wavelength. This is an ongoing research. We also present the latest work on laserdriven micro-thrusters and detail some the near term goals of our program.

  2. Comparison of ultrashort-pulse frequency-resolved-optical-gating traces for three common beam geometries

    SciTech Connect

    DeLong, K.W.; Trebino, R. ); Kane, D.J. )

    1994-09-01

    We recently introduced frequency-resolved optical gating (FROG), a technique for measuring the intensity and phase of an individual, arbitrary, ultrashort laser pulse. FROG can use almost any instantaneous optical nonlinearity, with the most common geometries being polarization gate, self-diffraction, and second-harmonic generation. The experimentally generated FROG trace is intuitive, visually appealing, and can yield quantitative information about the pulse parameters (such as temporal and spectral width and chirp). However, the qualitative and the quantitative features of the FROG trace depend strongly on the geometry used. We compare the FROG traces for several common ultrashort pulses for these three common geometries and, where possible, develop scaling rules that allow one to obtain quantitative information about the pulse directly from the experimental FROG trace. We illuminate the important features of the various FROG traces for transform-limited, linearly chirped, self-phase modulated, and nonlinearly chirped pulses, pulses with simultaneous linear chirp and self-phase modulation, and pulses with simultaneous linear chirp and cubic phase distortion, as well as double pulses, pulses with phase jumps, and pulses with complex intensity and phase substructure.

  3. New Results from Frequency and Energy Reference Measurements during the first Test Flight with the Airborne Integrated Path Differential Absorption Lidar System CHARM-F

    NASA Astrophysics Data System (ADS)

    Ehret, G.; Fix, A.; Amediek, A.; Quatrevalet, M.

    2015-12-01

    The Integrated Path Differential Absorption Lidar (IPDA) technique is regarded as a suitable means for the measurement of methane and carbon dioxide columns from satellite or aircraft platforms with unprecedented accuracy. Currently, the German-French methane mission MERLIN (Methan Remote Lidar Mission) is prepared. At the same time CHARM-F, an aircraft installed system has been developed at DLR as an airborne demonstrator for a spaceborne greenhouse gas mission. Both use e.g. optical parametric oscillators (OPOs) in a double-pulse mode as the transmitter. Of particular importance for both instruments are the sub-modules required for the frequency stabilization of the transmitter wavelength and, since the IPDA technique, in contrast to DIAL, requires the exact knowledge of the energy ratio of outgoing on-line. The coherence of the lidar transmitter gives rise to speckle effects which have to be considered for the monitoring of the energy ratio of outgoing on- and off-line pulses. For the frequency reference of CHARM-F, a very successful stabilization scheme has been developed which will also serve as the reference for MERLIN. In Spring 2015, CHARM-F was flown aboard the German HALO aircraft for the first time which enables a detailed view on the performance of both the energy calibration and frequency reference subsystems under real flight conditions. As an initial quality check we will compared the airborne results to previous lab measurements which have been performed under stable environmental conditions.

  4. Development and Evaluation of a High Sensitivity DIAL System for Profiling Atmospheric CO2

    NASA Technical Reports Server (NTRS)

    Ismail, Syed; Koch, Grady J.; Refaat, Tamer F.; Abedin, M. N.; Yu, Jirong; Singh, Upendra N.

    2008-01-01

    A ground-based 2-micron Differential Absorption Lidar (DIAL) CO2 profiling system for atmospheric boundary layer studies and validation of space-based CO2 sensors is being developed and tested at NASA Langley Research Center as part of the NASA Instrument Incubator Program. To capture the variability of CO2 in the lower troposphere a precision of 1-2 ppm of CO2 (less than 0.5%) with 0.5 to 1 km vertical resolution from near surface to free troposphere (4-5 km) is one of the goals of this program. In addition, a 1% (3 ppm) absolute accuracy with a 1 km resolution over 0.5 km to free troposphere (4-5 km) is also a goal of the program. This DIAL system leverages 2-micron laser technology developed under NASA's Laser Risk Reduction Program (LRRP) and other NASA programs to develop new solid-state laser technology that provides high pulse energy, tunable, wavelength-stabilized, and double-pulsed lasers that are operable over pre-selected temperature insensitive strong CO2 absorption lines suitable for profiling of lower tropospheric CO2. It also incorporates new high quantum efficiency, high gain, and relatively low noise phototransistors, and a new receiver/signal processor system to achieve high precision DIAL measurements. This presentation describes the capabilities of this system for atmospheric CO2 and aerosol profiling. Examples of atmospheric measurements in the lidar and DIAL mode will be presented.

  5. PIV, high-speed PLIF and chemiluminescence imaging for near-spark-plug investigations in IC engines

    NASA Astrophysics Data System (ADS)

    Fajardo, C. M.; Smith, J. D.; Sick, V.

    2006-07-01

    Measurements of the local flow and mixture condition near the spark plug of internal combustion engines are important to characterize their influence on ignition and combustion performance. This is especially true for direct-injection engines where limited time is available for mixture formation and optimum stratification of the fuel/air mixture to achieve best performance. Transient processes need to be visualized in an optically challenging environment. The application of digital Particle Image Velocimetry (PIV) for flow field measurements along with crank angle-resolved planar laser induced fluorescence (PLIF) and chemiluminescence imaging is discussed in the context of investigations of a highly stratified sprayguided direct-injection engine. Flow fields were captured in a firing optical single-cylinder engine to study the interaction of the fast spray and the underlying in-cylinder tumble flow. The impingement of the fuel spray on the spark plug electrodes and subsequent dispersion of the fuel cloud was filmed at a rate of 12kHz with a new PLIF technique using a diode-pumped Nd:YAG laser. Subsequent flame development and combustion progress could be followed via high-speed imaging of OH* chemiluminescence. This approach was also combined with double- pulse PLIF imaging of fuel distributions.

  6. Phase sensitive properties and coherent manipulation of a photonic crystal microcavity.

    PubMed

    Quiring, Wadim; Jonas, Björn; Förstner, Jens; Rai, Ashish K; Reuter, Dirk; Wieck, Andreas D; Zrenner, Artur

    2016-09-05

    We present phase sensitive cavity field measurements on photonic crystal microcavities. The experiments have been performed as autocorrelation measurements with ps double pulse laser excitation for resonant and detuned conditions. Measured E-field autocorrelation functions reveal a very strong detuning dependence of the phase shift between laser and cavity field and of the autocorrelation amplitude of the cavity field. The fully resolved phase information allows for a precise frequency discrimination and hence for a precise measurement of the detuning between laser and cavity. The behavior of the autocorrelation amplitude and phase and their detuning dependence can be fully described by an analytic model. Furthermore, coherent control of the cavity field is demonstrated by tailored laser excitation with phase and amplitude controlled pulses. The experimental proof and verification of the above described phenomena became possible by an electric detection scheme, which employs planar photonic crystal microcavity photo diodes with metallic Schottky contacts in the defect region of the resonator. The applied photo current detection was shown to work also efficiently at room temperature, which make electrically contacted microcavities attractive for real world applications.

  7. Photoacoustic lifetime imaging of dissolved oxygen using methylene blue

    NASA Astrophysics Data System (ADS)

    Ashkenazi, Shai

    2010-07-01

    Measuring distribution of dissolved oxygen in biological tissue is of prime interest for cancer diagnosis, prognosis, and therapy optimization. Tumor hypoxia indicates poor prognosis and resistance to radiotherapy. Despite its major clinical significance, no current imaging modality provides direct imaging of tissue oxygen. We present preliminary results demonstrating the potential of photoacoustic lifetime imaging (PALI) for noninvasive, 3-D imaging of tissue oxygen. The technique is based on photoacoustic probing of the excited state lifetime of methylene blue (MB) dye. MB is an FDA-approved water soluble dye with a peak absorption at 660 nm. A double pulse laser system (pump probe) is used to excite the dye and probe its transient absorption by detecting photoacoustic emission. The relaxation rate of MB depends linearly on oxygen concentration. Our measurements show high photoacoustic signal contrast at a probe wavelength of 810 nm, where the excited state absorption is more than four times higher than the ground state absorption. Imaging of a simple phantom is demonstrated. We conclude by discussing possible implementations of the technique in clinical settings and combining it with photodynamic therapy (PDT) for real-time therapy monitoring.

  8. The effect of ion current density amplification in a diode with passive anode in magnetic self-isolation mode

    SciTech Connect

    Pushkarev, Alexander I.; Isakova, Yulia I.; Vakhrushev, Dmitry V.

    2010-12-15

    The results of a study on gigawatt power pulsed ion beam parameters are presented here. The pulsed ion beam is formed by a diode with an explosive-emission potential electrode, in magnetic self-isolation mode [A. I. Pushkarev, J. I. Isakova, M. S. Saltimakov et al., Phys. Plasmas 17, 013104 (2010)]. The ion current density is 20-40 A/cm{sup 2}, the energy of the ions is 200-250 keV, and the beam composition is of protons and carbon ions. Experiments have been performed on the TEMP-4M accelerator, set in double-pulse formation mode. To measure the beam parameters, we used a time-of-flight diagnosis. It is shown that the carbon ion current density, formed in a planar diode with graphite potential electrode, is five to seven times higher than the values calculated from the Child-Langmuir ratio. A model of ion current density amplification in a diode with magnetic self-isolation is proposed. The motion of electrons in the anode-cathode gap is simulated using the program CST PARTICLE STUDIO.

  9. Motor simulation and the coordination of self and other in real-time joint action.

    PubMed

    Novembre, Giacomo; Ticini, Luca F; Schütz-Bosbach, Simone; Keller, Peter E

    2014-08-01

    Joint actions require the integration of simultaneous self- and other-related behaviour. Here, we investigated whether this function is underpinned by motor simulation, that is the capacity to represent a perceived action in terms of the neural resources required to execute it. This was tested in a music performance experiment wherein on-line brain stimulation (double-pulse transcranial magnetic stimulation, dTMS) was employed to interfere with motor simulation. Pianists played the right-hand part of piano pieces in synchrony with a recording of the left-hand part, which had (Trained) or had not (Untrained) been practiced beforehand. Training was assumed to enhance motor simulation. The task required adaptation to tempo changes in the left-hand part that, in critical conditions, were preceded by dTMS delivered over the right primary motor cortex. Accuracy of tempo adaptation following dTMS or sham stimulations was compared across Trained and Untrained conditions. Results indicate that dTMS impaired tempo adaptation accuracy only during the perception of trained actions. The magnitude of this interference was greater in empathic individuals possessing a strong tendency to adopt others' perspectives. These findings suggest that motor simulation provides a functional resource for the temporal coordination of one's own behaviour with others in dynamic social contexts.

  10. Single-shot laser pulse reconstruction based on self-phase modulated spectra measurements

    NASA Astrophysics Data System (ADS)

    Anashkina, Elena A.; Ginzburg, Vladislav N.; Kochetkov, Anton A.; Yakovlev, Ivan V.; Kim, Arkady V.; Khazanov, Efim A.

    2016-09-01

    We report a method for ultrashort pulse reconstruction based only on the pulse spectrum and two self-phase modulated (SPM) spectra measured after pulse propagation through thin media with a Kerr nonlinearity. The advantage of this method is that it is a simple and very effective tool for characterization of complex signals. We have developed a new retrieval algorithm that was verified by reconstructing numerically generated fields, such as a complex electric field of double pulses and few-cycle pulses with noises, pedestals and dips down to zero spectral intensity, which is challenging for commonly used techniques. We have also demonstrated a single-shot implementation of the technique for the reconstruction of experimentally obtained pulses. This method can be used for high power laser systems operating in a single-shot mode in the optical, near- and mid-IR spectral ranges. The method is robust, low cost, stable to noise, does not require a priori information, and has no ambiguity related to time direction.

  11. Optimization of modified carbon paste electrode with multiwalled carbon nanotube/ionic liquid/cauliflower-like gold nanostructures for simultaneous determination of ascorbic acid, dopamine and uric acid.

    PubMed

    Afraz, Ahmadreza; Rafati, Amir Abbas; Najafi, Mojgan

    2014-11-01

    We describe the modification of a carbon paste electrode (CPE) with multiwalled carbon nanotubes (MWCNTs) and an ionic liquid (IL). Electrochemical studies by using a D-optimal mixture design in Design-Expert software revealed an optimized composition of 60% graphite, 14.2% paraffin, 10.8% MWCNT and 15% IL. The optimal modified CPE shows good electrochemical properties that are well matched with model prediction parameters. In the next step, the optimized CPE was modified with gold nanostructures by applying a double-pulse electrochemical technique. The resulting electrode was characterized by scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction, and electrochemical impedance spectroscopy. It gives three sharp and well-separated oxidation peaks for ascorbic acid (AA), dopamine (DA), and uric acid (UA). The sensor enables simultaneous determination of AA, DA and UA with linear responses from 0.3 to 285, 0.08 to 200, and 0.1 to 450 μM, respectively, and with 120, 30 and 30 nM detection limits (at an S/N of 3). The method was successfully applied to the determination of AA, DA, and UA in spiked samples of human serum and urine.

  12. Optical alignment and diagnostics for the ATF microundulator FEL oscillator

    SciTech Connect

    Babzien, M.; Ben-Zvi, I.; Fang, J.M.

    1995-12-31

    The microundulator FEL oscillator has a wiggler period of 8.8 mm, and is designed for initial lasing at 0.5 microns with a 50 MeV electron beam. The design and performance of the optical diagnostics and alignment are discussed. A HeNe coalignment laser is mode-matched to the resonator cavity for transverse alignment. Interference fringes are observed in the cavity with a pellicle, allowing an alignment tolerance of +/- 10 micro-radians. The same pellicle is used to produce transition radiation by the electron beam. This enables precise transverse alignment of the electron beam to the resonator axis. The HeNe laser is also used to align the wiggler by backlighting its bore. This method aligns the wiggler to the optic axis to a tolerance of +/- 50 microns. A frequency-doubled,pulsed Nd:YAG laser that produces the electron bunch train is also mode-matched to the FEL cavity. The cavity length is adjusted to resonate with this pulse train. Light from the FEL is transported to the diagnostic room using two separate paths: one for the single pass spontaneous emission, and the second for the multipass cavity output. Several diagnostics (CCD camera, photodiode, photomultiplier tube, joulemeter, spectrometer, and streak camera) are used to characterize the light. These instruments measure light energy per micropulse ranging from 10 femto-Joules to 10 micro-Joules.

  13. Direct evidence of mismatching effect on H emission in laser-induced atmospheric helium gas plasma

    SciTech Connect

    Zener Sukra Lie; Koo Hendrik Kurniawan; May On Tjia; Rinda, Hedwig; Suliyanti, Maria Margaretha; Syahrun Nur Abdulmadjid; Nasrullah Idris; Alion Mangasi Marpaung; Marincan Pardede; Jobiliong, Eric; Muliadi Ramli; Heri Suyanto; Fukumoto, Kenichi; Kagawa, Kiichiro

    2013-02-07

    A time-resolved orthogonal double pulse laser-induced breakdown spectroscopy (LIBS) with helium surrounding gas is developed for the explicit demonstration of time mismatch between the passage of fast moving impurity hydrogen atoms and the formation of thermal shock wave plasma generated by the relatively slow moving major host atoms of much greater masses ablated from the same sample. Although this so-called 'mismatching effect' has been consistently shown to be responsible for the gas pressure induced intensity diminution of hydrogen emission in a number of LIBS measurements using different ambient gases, its explicit demonstration has yet to be reported. The previously reported helium assisted excitation process has made possible the use of surrounding helium gas in our experimental set-up for showing that the ablated hydrogen atoms indeed move faster than the simultaneously ablated much heavier major host atoms as signaled by the earlier H emission in the helium plasma generated by a separate laser prior to the laser ablation. This conclusion is further substantiated by the observed dominant distribution of H atoms in the forward cone-shaped target plasma.

  14. Visual area V5/hMT+ contributes to perception of tactile motion direction: a TMS study

    PubMed Central

    Amemiya, Tomohiro; Beck, Brianna; Walsh, Vincent; Gomi, Hiroaki; Haggard, Patrick

    2017-01-01

    Human imaging studies have reported activations associated with tactile motion perception in visual motion area V5/hMT+, primary somatosensory cortex (SI) and posterior parietal cortex (PPC; Brodmann areas 7/40). However, such studies cannot establish whether these areas are causally involved in tactile motion perception. We delivered double-pulse transcranial magnetic stimulation (TMS) while moving a single tactile point across the fingertip, and used signal detection theory to quantify perceptual sensitivity to motion direction. TMS over both SI and V5/hMT+, but not the PPC site, significantly reduced tactile direction discrimination. Our results show that V5/hMT+ plays a causal role in tactile direction processing, and strengthen the case for V5/hMT+ serving multimodal motion perception. Further, our findings are consistent with a serial model of cortical tactile processing, in which higher-order perceptual processing depends upon information received from SI. By contrast, our results do not provide clear evidence that the PPC site we targeted (Brodmann areas 7/40) contributes to tactile direction perception. PMID:28106123

  15. An Experimental Study of Droplets Produced by Plunging Breakers

    NASA Astrophysics Data System (ADS)

    Wang, D.; Dai, D.; Liu, X.; Duncan, J. H.

    2012-11-01

    The production of droplets by breaking water waves greatly affects the heat, mass and momentum transfer between the atmosphere and the sea surface. In this study, the production of droplets by mechanically generated breaking water waves was explored in a wave tank. The breakers were generated from dispersively focused wave packets (average frequency 1.15 Hz) using a programmable wave maker. Two overall wave maker amplitudes were used to create a strong spilling and a strong plunging breaker. The profile histories of the breaking wave crests along the center plane of the tank were measured with a cinematic laser-induced fluorescence technique, while the droplet diameter distributions and motions were measured at different locations along a horizontal line, which is 1 cm above the maximum height of the wave crest, using a double-pulsed cinematic shadowgraph technique. It is found that droplets are primarily generated when the plunging jet of the wave generates strong turbulence during impact with the wave's front face and when large air bubbles, entrapped during the plunging process, rise to the free surface and pop. The differences between the generation mechanisms in spilling and plunging breakers is highlighted. This work is supported by the Ocean Sciences Division of the National Science Foundation.

  16. A dual-camera cinematographic PIV measurement system at kilohertz frame rate for high-speed, unsteady flows

    NASA Astrophysics Data System (ADS)

    Bian, Shiyao; Ceccio, Steven L.; Driscoll, James F.

    2010-03-01

    A digital dual-camera cinematographic particle image velocimetry (CPIV) system has been developed to provide time-resolved, high resolution flow measurements in high-Reynolds number, turbulent flows. Two high-speed CMOS cameras were optically combined to acquire double-pulsed CPIV images at kilohertz frame rates. Bias and random errors due to camera misalignment, camera vibration, and lens aberration were corrected or estimated. Systematic errors due to the camera misalignment were reduced to less than 2 pixels throughout the image plane using mechanical alignment, resulting in 3.1% positional uncertainty of velocity measurements. Frame-to-frame uncertainties caused by mechanical vibration were eliminated with the aid of digital image calibration and frame-to-frame camera registration. This dual-camera CPIV system is capable of resolving high speed, unsteady flows with high temporal and spatial resolutions. It also allows time intervals between the two exposures down to 4 μs, enabling the measurements of speed flows 5-10 times higher than possible with frame-straddling using similar cameras. A turbulent shallow cavity was then chosen as the experimental object investigated by this dual-camera CPIV technique.

  17. Laboratory Measurements of Droplets Generated by Breaking Water Waves

    NASA Astrophysics Data System (ADS)

    Liu, X.; Duncan, J. H.

    2008-11-01

    The sizes and motions of droplets that are generated by single breaking water waves are explored in a wave tank that is 11.8 m long, 1.1 m wide and 2.2 m high (0.91 m water depth). A programmable wave maker is used to generate wave packets (central frequency 1.15 Hz) that create breakers by dispersive focusing. Different amplitudes of the wave maker motion are used to generate various breaking waves ranging from weakly spilling breakers to plunging breakers. The profile histories of the breaking wave crests along the center plane of the tank are measured with a cinematic LIF technique. The droplets at various heights and positions above the crests of the breaking waves are measured with a shadowgraph technique that uses a double-pulsed laser, a long-distance microscope lens and a CCD camera. These two measurement systems are mounted on an instrument carriage that moves along the tank with the speed of the breaking crests. The results include the size distributions of the droplets, the variations of the droplet number with height above the wave crest and the velocities of the droplets. The effects of the intensity of the breaking waves on the dynamics of the droplets are discussed.

  18. Laboratory Measurements of Droplets Generated by Breaking Water Waves

    NASA Astrophysics Data System (ADS)

    Wang, D.; Liu, X.; Duncan, J. H.

    2010-11-01

    The production of droplets generated by breaking water waves greatly affects the heat, mass and momentum transfer between the atmosphere and the sea surface. In this study, the generation of droplets by single breaking water waves, was explored in a wave tank. Plunging breakers were generated from dispersively focused wave packets (average frequency 1.15 Hz) using a programmable wave maker. The profile histories of the breaking wave crests along the center plane of the tank were measured with a cinematic laser-induced fluorescence technique, while the droplet diameters and motions were measured with a double-pulsed cinematic shadowgraph technique. The two measurement systems were mounted on an instrument carriage that was set to move along the tank following the breaking crests. It was found that droplets are primarily generated when the wave's plunging jet generates strong turbulence during impact with the wave's front face and when large air bubbles, entrapped during the plunging process, rise to the free surface and pop.

  19. Security of the differential-quadrature-phase-shift quantum key distribution

    NASA Astrophysics Data System (ADS)

    Kawakami, Shun; Sasaki, Toshihiko; Koashi, Masato

    2016-08-01

    One of the simplest methods for implementing quantum key distribution over fiber-optic communication is the Bennett-Brassard 1984 protocol with phase encoding (PE-BB84 protocol), in which the sender uses phase modulation over double pulses from a laser and the receiver uses a passive delayed interferometer. Using essentially the same setup and by regarding a train of many pulses as a single block, one can carry out the so-called differential-quadrature-phase-shift (DQPS) protocol, which is a variant of differential-phase-shift (DPS) protocols. Here we prove the security of the DQPS protocol based on an adaptation of proof techniques for the BB84 protocol, which inherits the advantages arising from the simplicity of the protocol, such as accommodating the use of threshold detectors and simple off-line calibration methods for the light source. We show that the secure key rate of the DQPS protocol in the proof is eight-thirds as high as the rate of the PE-BB84 protocol.

  20. Modification of sodium and potassium channel gating kinetics by ether and halothane

    SciTech Connect

    Bean, B.P.; Shrager, P.; Goldstein, D.A.

    1981-03-01

    The effects of ether and halothane on the kinetics of sodium and potassium currents were investigated in the crayfish giant axon. Both general anesthetics produced a reversible, dose-dependent speeding up of sodium current inactivation at all membrane potentials, with no change in the rising phase of the currents. Double-pulse inactivation experiments with ether also showed faster inactivation, but the rate of recovery from inactivation at negative potentials was not affected. Ether shifted the midpoint of the steady-state fast inactivation curve in the hyperpolarizing direction and made the curve steeper. The activation of potassium currents was faster with ether present, with no change in the voltage dependence of steady-state potassium currents. Ether and halothane are known to perturb the structure of lipid bilayer membranes; the alterations in sodium and potassium channel gating kinetics are consistent with the hypothesis that the rats of the gating processes of the channels can be affected by the state of the lipids surrounding the channels, but a direct effect of ether and halothane on the protein part of the channels cannot be ruled out.

  1. Statistical analysis of the ion beam production in a self magnetically insulated diode

    SciTech Connect

    Isakova, Y. I.; Pushkarev, A. I.; Khaylov, I. P.

    2013-09-15

    The paper presents the results of a study on shot to shot variation in energy density of an ion beam formed by a self-magnetically insulated diode with an explosive emission cathode. The experiments were carried out with the TEMP-4M accelerator operating in double-pulse mode: plasma formation occurs during the first pulse (negative polarity, 300–500 ns, 100–150 kV), and ion extraction and acceleration during the second pulse (positive polarity, 150 ns, 250–300 kV). Crucially, it was found that the standard deviation of energy density does not exceed 11%, whilst the same variation for ion current density was 20%–30%, suggesting the presence of neutrals in the beam. This idea is further supported by the fact that ion current density is only weakly dependant on the accelerating voltage and other output parameters of the accelerator (coefficient of determination < 0.3), whilst the correlation between the energy density of the beam and the output parameters is strong (coefficient of determination > 0.9). We attribute the neutral component as being due to charge exchange between accelerated ions and neutral molecules from a neutral layer near the anode surface. Implementation using a self-magnetically insulated diode with an explosive-emission cathode, having an operational lifetime of up to 10{sup 7} shots, has promising prospects for various technological applications.

  2. 0.4-3.5-micrometer Observations of 4179 Toutatis

    NASA Astrophysics Data System (ADS)

    Howell, E. S.; Britt, D. T.; Bell, J. F.; Binzel, R. P.; Lebofsky, L. A.

    1993-07-01

    We obtained nearly simultaneous observations of 4179 Toutatis over a 0.3-3.5 micrometer wavelength range on 4 January 1993 UT. Howell obtained a 1.2-2.5 micrometer spectrophotometry using the Multiple Mirror Telescope in Arizona. Britt and Bell obtained narrowband photometry in the 3-micrometer region as well as broadband JHK photometry from the Infrared Telescope Facility in Hawaii. Binzel measured the visible spectrum using a CCD spectrograph at the McGraw-Hill Observatory in Arizona. Using V photometry reported by Pravec in the Czech Republic on adjacent nights [1], we were able to combine all these spectral regions. The rotation period of this object is approximately 10 days, so the time differences between the measurements of different spectral regions are negligible. Tholen has classified 4179 Toutatis as an S-type asteroid based on visible photometry. We measure a pyroxene absorption band near 2 micrometers, present in most S-type asteroid spectra. Unfortunately, a gap in spectral coverage prevents us from determining the characteristics of the 1-micrometer absorption band accurately. The spectral slope as measured from 1.25 to 2.2 micrometers is 6-10%, which is modest compared to other S-type asteroids. The spectrum of this asteroid is similar to other near-Earth S-type asteroids that have been observed in the near-infrared wavelength region. On 4 January 1993, 4179 Toutatis was 0.182 AU from the Earth, and 1.158 AU from the Sun. At this solar distance, the thermal emission contributes substantially to the flux at 3 micrometers. The determination of thermal emission is complicated by the slow rotation rate and the irregular shape of this object that was revealed by radar observations [2]. Preliminary results suggest that no 3-micrometer absorption feature is present, indicating that this object is anhydrous. Using these spectral data, we will compare 4179 Toutatis to other S-type asteroids, both in the main belt and the near-Earth environment. References

  3. The fate of the solid matter orbiting HR 4796A

    NASA Technical Reports Server (NTRS)

    Jura, M.; Ghez, A. M.; White, Russell J.; Mccarthy, D. W.; Smith, R. C.; Martin, P. G.

    1995-01-01

    We have obtained optical spectra, 2 micrometers speckle images, and an upper limit to the 800 micrometers flux for HR 4796A, and optical spectra for its physical companion separated by 7.7 arcsecs, HR 4796B. We detect H-beta, H-gamma, and the calcium H and K lines in emission from HR 4796B; these data are consistent with the hypothesis that it is later than spectral type M2 and lies substantially above the main-sequence. From the location of HR 4796B on the H-R diagram, the estimated age of this star is 3 x 10(exp 6) yr, and assuming this age for the entire system, we find from our 2 micrometers speckle data that there is no close stellar companion to HR 4796A (M greater than 0.125 solar mass) between 11 and 120 AU from the star. From the IRAS and ground-based photometry, it seems that there is a hole in the dust distribution around HR 4796A with an inner radius of between approximately 40 and approximately 200 AU. The observed circumstellar dust grains, which lie at D greater than 40 AU from the star, are likely to be at least 3 micrometers in radius in order to be gravitationally bound to HR 4796A, if the circumstellar dust cloud is optically thin. Since they are larger than almost all interstellar grains, the circumstellar dust grains probably grew by coalescence. Because the existing grains at D greater than 40 AU have undergone measurable coalescence, it is possible that particles that presumably once existed at D less than 40 AU, where the collision times were shorter than at D greater than 40 AU, grew into macroscopic objects. A likely explanation for the dust hole is that there is a companion located at about half the inner radius of the dust hole, or between 20 and 100 AU from the star. If such a companion exists, it must have a mass less than 0.125 solar mass. Since grain coalescence has occurred, this putative companion possibly could be a planet.

  4. JWST Mirror Technology Development

    NASA Technical Reports Server (NTRS)

    Stahl, H. Philip

    2010-01-01

    Since the initial Design Studies leading to JWST, Mirror Technology was identified as a (if not the) critical capability necessary to enable the next generation of large aperture space telescopes required to achieve the science goals of imaging the earliest galaxies and proto-galaxies after the big bang. Specific telescope architectures were explored via three independent design concept studies conducted during the summer of 1996. Achieving the desired science objectives required a never before demonstrated space telescope capability, one with an 8 meter class primary mirror that is diffraction limited at 2 micrometers and operating in deep space at temperatures well below 70K. Beryllium was identified in the NASA "Yardstick" design as the preferred material because of its ability to provide stable optical performance in the anticipated thermal environment as well as its excellent specific stiffness. Because of launch vehicle constraints, two very significant architectural constraints were placed upon the telescope: segmentation and areal density. Each of these directly resulted in specific technology capability requirements. First, because the maximum launch vehicle payload fairing diameter is approximately 4.5 meters, the only way to launch an 8 meter class mirror is to segment it, fold it and deploy it on orbit - resulting in actuation and control requirements. Second, because of launch vehicle mass limits, the primary mirror allocation was only 1000 kg - resulting in a maximum areal density specification of 20 kilograms per square meter.

  5. Near-Infrared Interferometric Images of the Solar System Sized Disk Surrounding the Herbig Ae/Be Star MWC 349A

    NASA Technical Reports Server (NTRS)

    Danchi, W.C.; Tuthill, P. G.; Monnier, J. D.; Fisher, Richard (Technical Monitor)

    2000-01-01

    We present images of the Herbig Ae/Be star MWC 349A at 1.65 and 2.27, and 3.08 micrometers, reconstructed from complex visibility data obtained with an aperture masking interferometric technique on the Keck I telescope. These images have an approximately elliptical shape, and are consistent with the expected shape of a nearly edge-on Keplerian disk. Visibility data were fitted with uniform ellipses with major axes 36 +/- 2, 47 +/- 2, and 62 +/- 1 mas, respectively. The axial ratio of the ellipses is approximately 0.5 +/- 0.1, and the major axis is at a position angle of 100 +/- 3 degrees, consistent with the position angle of the dark lane observed previously in the Very Large Array (VLA) radio continuum maps at 8 and 22 GHz, perpendicular to the symmetry axis of the bipolar lobes of H66(alpha) recombination line emission, and consistent with positions of the recombination line maser spots at 1.3 mm. At an assumed distance of 1.2 kpc, the linear sizes of the disk are 44 and 57 AU at 1.65 and 2.2 micrometers, respectively. The disk is the presumed source of ionized material in the bipolar outflow and ultracompact HII region around the star.

  6. Martian aerosols: Near-infrared spectral properties and effects on the observation of the surface

    NASA Technical Reports Server (NTRS)

    Erard, Stephane; Mustard, John; Murchie, Scott; Bibring, Jean-Pierre; Cerroni, Priscilla; Caradini, Angioletta

    1994-01-01

    Imaging sprectroscopic measurements (ISM) of Mars acquired by the ISM instrument on Phobos-2 are used to investigate the NIR spectral properties of aerosols and the effects of atmospheric scattering on inferred mineralogy of the surface. Estimates of aerosols spectra between 0.77 and 2.6 micrometers are derived above Tharsis and Ophir Planum. The spectral continua are consistent with the particle size distribution derived using data from the solar occultation experiment on-board the spacecraft (effective radius approximately = 1.2 micrometers, with an effective variance approximately = 0.2). The aerosols spectra contain water-ice absorption features and possibly absorptions due to clay and/or sulfates. The largest effect of the aerosols on surface spectra is in dark regions, where the continuum spectral slope becomes more negative and the 1-micrometers absorption due to Fe in pyroxene is shifted toward longer wavelengths. The effects of aerosols on spectra of bright regions are insufficiently large to change mineralogic interpretations based on ISM data, i.e., that bright regions in Tharsis are dominated spectrally by hematite, but that additional ferric minerals are probably present in other areas including Arabia.

  7. Using scattered-light modeling for semiconductor critical dimension metrology and calibration

    NASA Astrophysics Data System (ADS)

    Krukar, Richard H.; Prins, Steven L.; Krukar, D. M.; Peterson, Gary A., Jr.; Gaspar, Steve; McNeil, John R.; Naqvi, S. Sohail H.; Hush, Donald R.

    1993-08-01

    Quantitative methods are developed to use optical scatter to measure the critical dimensions of gratings etched into bulk Si and developed photoresist patterns on silicon substrates. Previous work either classified microstructures qualitatively or employed a 'chi-by-eye' method to find that structures were similar or dissimilar. A single detector scanning scatterometer is used to measure large 32 micrometers pitch structures while another instrument that varies the angle of incidence and tracks diffracted orders via the grating equation is used to measure 2 micrometers pitch structures. A rigorous coupled wave light scatter model is used to simulate diffraction from a set of test wafers. Partial least squares and neural network analysis techniques are then employed to use correlations between the simulated diffraction and the critical dimensions of the modeled structures to produce a capability to measure the critical dimensions from scattered light measurements. The marriage of rigorous coupled wave diffraction modeling and optical scatterometry directly addresses the needs of the industry for a rapid and nondestructive metrology tool.

  8. Particulate retrieval of hydrolytically degraded poly(lactide-co-glycolide) polymers.

    PubMed

    Cordewener, F W; Dijkgraaf, L C; Ong, J L; Agrawal, C M; Zardeneta, G; Milam, S B; Schmitz, J P

    2000-04-01

    This article describes a technique for the retrieval of polymeric particulate debris following advanced hydrolytic in vitro degradation of a biodegradable polymer and presents the results of the subsequent particle analysis. Granular 80/20 poly(L-lactide-co-glycolide) (PLG) was degraded in distilled, deionized water in Pyrextrade mark test tubes at 80 degrees C for 6 weeks. Subsequently, a density gradient was created by layering isopropanol over the water, followed by a 48-h incubation. Two opaque layers formed in the PLG tubes, which were removed and filtered through 0.2-micrometer polycarbonate membrane filters. In addition, Fourier transform IR spectroscopy (FTIR) was performed to confirm the presence of polymer in the removed layers. The filters were gold sputter coated, and scanning electron microscopy (SEM) images were made. FTIR analysis confirmed that the removed material was PLG. SEM images of the extracts from the upper (lowest density) opaque layer showed a fine, powderlike substance and globular structures of 500-750 nm. The SEM images of the lower (highest density) opaque layer showed particles with a crystalline-like morphology ranging in size from 4 to 30 micrometer. Particulate PLG debris generated with the described technique can be useful for further studies of its biological role in complications associated with poly(alpha-hydroxy)ester implants. This study shows the presence of very persistent nano- and microparticles in the degradation pathway of PLG.

  9. Multimode Broad-Band Patch Antennas

    NASA Technical Reports Server (NTRS)

    Romanofsky, Robert R.

    2003-01-01

    Microstrip patch antennas of a proposed type would be tunable over broad wavelength ranges. These antennas would be attractive for use in a variety of microwave communication systems in which there are requirements for transmission and/or reception at multiple, widely separated frequencies. Prior efforts to construct tunable microstrip patch antennas have involved integration of microstrip circuitry with, variously, ferrite films with magneticfield tuning, solid-state electronic tuning devices, or piezoelectric tuning actuators. Those efforts have been somewhat successful, but have yielded tuning ranges of 20 percent and smaller much smaller than needed in typical practical cases. Like prior microstrip patch antennas (both tunable and non-tunable), the proposed antennas would have instantaneous bandwidths of about 1 percent of their nominal or resonance frequencies. However, these would be tunable over much broader frequency ranges as much as several octaves, depending on specific designs. They could be fabricated relatively simply and inexpensively by use of conventional photolithography, and without need for integration with solid-state electronic or piezoelectric control devices. An antenna as proposed (see figure) would include a microstrip patch radiating element on a thin ferroelectric film on a semiconductor substrate with a ground-plane conductor on the underside of the substrate. The ferroelectric film could be, for example, SrTiO3 with a thickness of the order of 1 or 2 micrometers.

  10. Galileo infrared imaging spectrometry measurements at the Moon

    NASA Astrophysics Data System (ADS)

    McCord, T. B.; Soderblom, L. A.; Carlson, R. W.; Fanale, F. P.; Lopes-Gautier, R.; Ocampo, A. C.; Forsythe, J.; Campell, B.; Granahan, J. C.; Smythe, W. D.; Weissmann, P. R.; Becker, K. J.; Edwards, K.; Kamp, L.; Lo, J.; Mehlman, R.; Torson, J.; Danielson, G. E.; Matson, D. L.; Kieffer, H. H.; Johnson, T. V.

    1994-03-01

    Imaging spectrometer observations were made of the surface of the Moon during the December 1990 flyby of the Earth-Moon system by the Galileo spacecraft. This article documents this data set and presents analyses of some of the data. The near infrared mapping spectrometer (NIMS) investigation obtained 17 separate mosaics of the Moon in 408 spectral channels between about 0.7 and 5.2 micrometers. The instrument was originally designed to operate in orbit about Jupiter and therefore saturates at many spectral channels for most measurement situations at 1 AU. However, sufficient measurements were made of the Moon to verify the proper operation of the instrument and to demonstrate its capabilities. Analysis of these data show that the NIMS worked as expected and produced measurements consistent with previous ground-based telescopic studies. These are the first imaging spectrometer measurements of this type from space for the Moon, and they illustrate several major points concerning this type of observation and about the NIMS capabilities specifically. Of major importance are the difference between framing and scanning instruments and the effects of the spacecraft and the scan platform on the performance of such and experiment. The science return of subsequent NIMS and other investigation measurements will be significantly enhanced by the experience and results gained.

  11. Patch recognition of algal blooms and macroalgae

    NASA Astrophysics Data System (ADS)

    Szekielda, K. H.; Bowles, J. H.; Gillis, D. B.; Snyder, W.; Miller, W. D.

    2010-04-01

    Fraunhofer lines and atmospheric absorption bands interfere with the spectral location of absorption bands of photosynthetic pigments in plankton. Hyperspectral data were used to address this interference on identifying absorption bands by applying derivative analysis of radiance spectra. Algal blooms show elevated radiance data even at longer wavelengths compared to oligotrophic water and may reach radiance values of around 800 W/m2/micrometer/sr at a wavelength of about 0.8 μm. Therefore, the use of a spectral range beyond 0.55 μm is useful to describe bloom characteristics. In particular, the slope between 0.55 μm to 0.80 μm shows an advantage to depict gradients in plankton blooms. Radiance spectra in the region from 0.4 to 0.8 μm for oligotrophic water and near coastal water show similar location of absorption bands when analyzed with derivative analysis but with different amplitudes. For this reason, radiance spectra were also analyzed without atmospheric correction, and various approaches to interpret radiance data over plankton blooms were investigated. Cluster analysis and ratio techniques at longer wavelengths were found to assist in the separation of ocean color gradients and distinguish bio-geochemical provinces in near-coastal waters. Furthermore, using the slope of spectra from plankton blooms, in connection with scatter diagrams at various wavelengths, shows that details can be revealed that would not be recognized in single channels at lower wavelength.

  12. Fluid mechanical proximity effects in high-resolution gravure printing for printed electronics

    NASA Astrophysics Data System (ADS)

    Grau, Gerd; Scheideler, William J.; Subramanian, Vivek

    2016-11-01

    Gravure printing is a very promising method for printed electronics because it combines high throughput with high resolution. Recently, printed lines with 2 micrometer resolution have been demonstrated at printing speeds on the order of 1m/s. In order to build realistic circuits, the fluid dynamics of complex pattern formation needs to be studied. Recently, we showed that highly-scaled lines printed in close succession exhibit proximity effects that can either improve or deteriorate print quality depending on a number of parameters. It was found that this effect occurs if cells are connected by a thin fluid film. Here, we present further experimental and modeling results explaining the mechanism by which this thin fluid film affects pattern formation. During the transfer of ink from the roll to the substrate, ink can flow in between connected cells. Asymmetry in the fluid distribution created by the preceding doctor blade wiping process results in net fluid flow from cells that transfer first to cells that transfer subsequently. The proximity of these cells thus affects the final ink distribution on the substrate, which is critically important to understand and design optimally when printing highly-scaled patterns of electronic materials. This work is based upon work supported in part by the National Science Foundation under Cooperative Agreement No. EEC-1160494.

  13. Measuring the Magnetic Center Behavior of an ILC Superconducting Quadrupole Prototype

    SciTech Connect

    Spencer, Cherrill M.; Adolphsen, Chris; Berndt, Martin; Jensen, David R.; Rogers, Ron; Sheppard, John C.; Lorant, Steve St; Weber, Thomas B.; Weisend, John, II; Brueck, Heinrich; Toral, Fernando; /Madrid, CIEMAT

    2011-02-07

    The main linacs of the proposed International Linear Collider (ILC) consist of superconducting cavities operated at 2K. The accelerating cavities are contained in a contiguous series of cryogenic modules that also house the main linac quadrupoles, thus the quadrupoles also need to be superconducting. In an early ILC design, these magnets are about 0.6 m long, have cos (2{theta}) coils, and operate at constant field gradients up to 60 T/m. In order to preserve the small beam emittances in the ILC linacs, the e+ and e- beams need to traverse the quadrupoles near their magnetic centers. A quadrupole shunting technique is used to measure the quadrupole alignment with the beams; this process requires the magnetic centers move by no more than about 5 micrometers when their strength is changed. To determine if such tight stability is achievable in a superconducting quadrupole, we at SLAC measured the magnetic center motions in a prototype ILC quadrupole built at CIEMAT in Spain. A rotating coil technique was used with a better than 0.1 micrometer precision in the relative field center position, and less than a 2 micrometer systematic error over 30 minutes. This paper describes the warm-bore cryomodule that houses the quadrupole in its Helium vessel, the magnetic center measurement system, the measured center data and strength and harmonics magnetic data.

  14. Green evolution and dynamic adaptations revealed by genomes of the marine picoeukaryotes Micromonas.

    PubMed

    Worden, Alexandra Z; Lee, Jae-Hyeok; Mock, Thomas; Rouzé, Pierre; Simmons, Melinda P; Aerts, Andrea L; Allen, Andrew E; Cuvelier, Marie L; Derelle, Evelyne; Everett, Meredith V; Foulon, Elodie; Grimwood, Jane; Gundlach, Heidrun; Henrissat, Bernard; Napoli, Carolyn; McDonald, Sarah M; Parker, Micaela S; Rombauts, Stephane; Salamov, Aasf; Von Dassow, Peter; Badger, Jonathan H; Coutinho, Pedro M; Demir, Elif; Dubchak, Inna; Gentemann, Chelle; Eikrem, Wenche; Gready, Jill E; John, Uwe; Lanier, William; Lindquist, Erika A; Lucas, Susan; Mayer, Klaus F X; Moreau, Herve; Not, Fabrice; Otillar, Robert; Panaud, Olivier; Pangilinan, Jasmyn; Paulsen, Ian; Piegu, Benoit; Poliakov, Aaron; Robbens, Steven; Schmutz, Jeremy; Toulza, Eve; Wyss, Tania; Zelensky, Alexander; Zhou, Kemin; Armbrust, E Virginia; Bhattacharya, Debashish; Goodenough, Ursula W; Van de Peer, Yves; Grigoriev, Igor V

    2009-04-10

    Picoeukaryotes are a taxonomically diverse group of organisms less than 2 micrometers in diameter. Photosynthetic marine picoeukaryotes in the genus Micromonas thrive in ecosystems ranging from tropical to polar and could serve as sentinel organisms for biogeochemical fluxes of modern oceans during climate change. These broadly distributed primary producers belong to an anciently diverged sister clade to land plants. Although Micromonas isolates have high 18S ribosomal RNA gene identity, we found that genomes from two isolates shared only 90% of their predicted genes. Their independent evolutionary paths were emphasized by distinct riboswitch arrangements as well as the discovery of intronic repeat elements in one isolate, and in metagenomic data, but not in other genomes. Divergence appears to have been facilitated by selection and acquisition processes that actively shape the repertoire of genes that are mutually exclusive between the two isolates differently than the core genes. Analyses of the Micromonas genomes offer valuable insights into ecological differentiation and the dynamic nature of early plant evolution.

  15. Cross-bridge kinetics in rat myocardium: effect of sarcomere length and calcium activation.

    PubMed

    Wannenburg, T; Heijne, G H; Geerdink, J H; Van Den Dool, H W; Janssen, P M; De Tombe, P P

    2000-08-01

    We tested the hypotheses that Ca(2+) concentration ([Ca(2+)]) and sarcomere length (SL) modulate force development via graded effects on cross-bridge kinetics in chemically permeabilized rat cardiac trabeculae. Using sinusoidal length perturbations, we derived the transfer functions of stiffness over a range of [Ca(2+)] at a constant SL of 2.1 micrometer (n = 8) and at SL of 2.0, 2.1, and 2.2 micrometer (n = 4). We found that changes in SL affected only the magnitude of stiffness, whereas [Ca(2+)] affected the magnitude and phase-frequency relations. The data were fit to complex functions of two exponential processes. The characteristic frequencies (b and c) of these processes are indexes of cross-bridge kinetics, with b relating to cross-bridge attachment to and c to detachment from certain non-force-generating states. Both were significantly affected by [Ca(2+)], with an increase in b and c of 140 and 44%, respectively, over the range of [Ca(2+)] studied (P < 0.01). In contrast, SL had no effect on the characteristic frequencies (P > 0.6). We conclude that Ca(2+) activation modulates force development in rat myocardium, at least in part, via a graded effect on cross-bridge kinetics, whereas SL effects are mediated mainly by recruitment of cross bridges.

  16. Optical Constants of the Ammonium Ion: A Potential Ice Product in the Outer Solar System

    NASA Astrophysics Data System (ADS)

    Roush, T. L.; Moore, M. H.; Cook, J. C.

    2008-12-01

    Optical constants, the real and imaginary indices of refraction, are the fundamental values used in a wide variety of radiative transfer models that are relevant to many environments including circumstellar disks, planetary atmospheres, and planetary surfaces. Cook et al. (2007) observed a feature near 2.2 micrometers (um) in the reflectance spectrum of Pluto's moon, Charon. They suggested evidence for both ammonia di- hydrate and ammonia hemi-hydrate on opposite hemispheres of Charon. Moore et al. (2003) discuss the irradiation of N2-CH4-CO ices; mixtures relevant for Pluto, Triton, and a plausible constituent for some Kuiper Belt Objects and Centaurs. One stable product observed after irradiation of the ice mixture is the ammonium ion, NH4+. NH4+ has strong spectral features in the 3-4 um region and weaker overtones near 2.21 and 2.24 um (Moore et al. 2003). The 2.21 um feature is the strongest of the overtone bands and is near the wavelengths observed for Charon. Using the measurements of Moore et al. (2003) the optical constants of NH4+ are estimated and will be available to investigate NH4+ as an alternative candidate for the feature observed on Charon. Moore, M. et al. 2003, Earth Moon Planets, 92, 291-306. Cook, J. et al. 2007, Ap J, 663, 1406-1419.

  17. Energy transfer and lasing in LiYbF4:Ho, LiYbF4:Ho,Tm, and KYb(WO4)3 crystals

    NASA Astrophysics Data System (ADS)

    Sandulenko, Alexander V.; Sandulenko, V. A.; Tkachuk, Alexandra M.; Titov, Alexandre N.; Reiterov, V. M.; Ivanov, V. N.

    1998-12-01

    We have studied both theoretically and experimentally the energy transfer processes in YbLiF4:Ho3+ (0.4%) and YbLiF4:Ho3+ (0.4%),Tm3+ (10%) crystals and in the series of crystals KYb(WO4)2:Tm3+,Ho3+ (0.4%) with the thulium concentration 5; 10; and 20%. The population kinetics of the 5I7 holmium level was studied under the 1.047 micrometers Q-switched YLF:Nd3+ laser pumping. The efficiency of energy transfer processes in Ho3+ doped crystals, codoped with Yb3+ and Tm3+, was demonstrated. With an YbLiF4:Ho3+ (0.4%) laser rod we have obtained lasing at 2.06 micrometers with the total efficiency of 4.8% and the slope efficiency of 11%. In the KYb(WO4)2:Tm3+ (10%),Ho3+ (0.4%) crystal, lasing was obtained for the first time at 2 micrometers . The pumping threshold being approximately 150 mJ, total efficiency 6% and slope efficiency 9.7% was achieved.

  18. SiC and Si3N4 Recession Due to SiO2 Scale Volatility Under Combustor Conditions

    NASA Technical Reports Server (NTRS)

    Smialek, James L.; Robinson, Raymond C.; Opila, Elizabeth J.; Fox, Dennis S.; Jacobson, Nathan S.

    1999-01-01

    Silicon carbide (SiC) and Si3N4 materials were tested in various turbine engine combustion environments chosen to represent either conventional fuel-lean or fuel-rich mixtures proposed for high-speed aircraft. Representative chemical vapor-deposited (CVD), sintered, and composite materials were evaluated by furnace and high-pressure burner rig exposures. Although protective SiO2 scales formed in all cases, the evidence presented supports a model based on paralinear growth kinetics (i.e., parabolic growth moderated simultaneously by linear volatilization). The volatility rate is dependent on temperature, moisture content, system pressure, and gas velocity. The burner tests were thus used to map SiO2 volatility (and SiC recession) over a range of temperatures, pressures, and velocities. The functional dependency of material recession (volatility) that emerged followed the form A[exp(-Q / RT)](P(sup x)v(sup y). These empirical relations were compared with rates predicted from the thermodynamics of volatile SiO and SiOxHy reaction products and a kinetic model of diffusion through a moving boundary layer. For typical combustion conditions, recession of 0.2 to 2 micrometers/hr is predicted at 1200 to 1400 C, far in excess of acceptable long-term limits.

  19. CSHELL: a high spectral resolution 1-5 um cryogenic echelle spectrograph for the IRTF

    NASA Astrophysics Data System (ADS)

    Greene, Thomas P.; Tokunaga, Alan T.; Toomey, Douglas W.; Carr, Jonathan B.

    1993-10-01

    A 1 - 5.4 micrometers Cryogenic Echelle Spectrograph (CSHELL) for the NASA Infrared Telescope Facility is described. It achieves a resolving power of 5,000 to 40,000 using slits ranging from 4.0' to 0.5' in width and 30' long. It operates in a single-order long-slit mode, and a circular variable filter is used as an order sorter. Two infrared arrays are employed to achieve spectral coverage from 1 - 5.4 micrometers : a 256 X 256 HgCdTe NICMOS-3 array for 1 - 2.5 micrometers and a SBRC 58 X 62 InSb array for 2.8 - 5.4 micrometers . A closed- cycle cooler is employed to keep the optics and supporting structure at 73 K and to maintain the detectors at their proper operating temperatures. The entire spectrograph fits within an envelope of 64 cm X 35 cm X 27 cm. The instrument is controlled by a microcomputer mounted on the telescope, but the observer commands the instrument from a UNIX X Windows workstation on the Internet. This use of the Internet for communication between instrument control and user interface computers facilitates remote observing. A limiting magnitude of 12.3 mag is achieved for S/N equals 10 in 1 hour integration time, at resolving power of 20,000 at 2.2 micrometers wavelength.

  20. Chlorpromazine-induced corneal endothelial phototoxicity

    SciTech Connect

    Hull, D.S.; Csukas, S.; Green, K.

    1982-04-01

    Chlorpromazine, which has been used extensively for the treatment of psychiatric disorders, is known to accumulate in the posterior corneal stroma, lens, and uveal tract. Because it is a phototoxic compound, the potential exists for it to cause cellular damage after light exposure. Specular microscopic perfusion of corneal endothelial cells in darkness with 0.5 mM chlorpromazine HCl resulted in a swelling rate of 18 +/- 2 micrometer/hr, whereas corneas exposed to long-wavelength ultraviolet light for 3 min in the presence of 0.5 mM chlorpromazine swelled at 37 +/- 9 micrometer/hr (p less than 0.01). Preirradiation of 0.5 mM chlorpromazine solution with ultraviolet light for 30 min and subsequent corneal perfusion with the solution resulted in a corneal swelling rate of 45 +/- 19 micrometer/hr. Cornea endothelial cells perfused with 0.5 mM chlorpromazine that was preirradiated with ultraviolet light showed marked swelling on scanning electron microscopic examination, whereas those perfused with nonirradiated chlorpromazine were flat and showed a normal mosaic pattern. Combining either 500 U/ml catalase or 290 U/ml superoxide dismutase with chlorpromazine did not alter photoinduction of corneal swelling. The data suggest that corneal endothelial chlorpromazine phototoxicity is secondary to cytotoxic products resulting from the photodynamically induced decomposition of chlorpromazine and is not caused by hydrogen peroxide or superoxide anion generated during the phototoxic reaction.

  1. Comparison of aerobically-treated and untreated crop residue as a source of recycled nutrients in a recirculating hydroponic system

    NASA Technical Reports Server (NTRS)

    Mackowiak, C. L.; Garland, J. L.; Strayer, R. F.; Finger, B. W.; Wheeler, R. M.

    1996-01-01

    This study compared the growth of potato plants on nutrients recycled from inedible potato biomass. Plants were grown for 105 days in recirculating, thin-film hydroponic systems containing four separate nutrient solution treatments: (1) modified half-strength Hoagland's (control), 2) liquid effluent from a bioreactor containing inedible potato biomass, 3) filtered (0.2 micrometer) effluent, and 4) the water soluble fraction of inedible potato biomass (leachate). Approximately 50% of the total nutrient requirement in treatments 2-4 were provided (recycled) from the potato biomass. Leachate had an inhibitory effect on leaf conductance, photosynthetic rate, and growth (50% reduction in plant height and 60% reduction in tuber yield). Plants grown on bioreactor effluent (filtered or unfiltered) were similar to the control plants. These results indicated that rapidly degraded, water soluble organic material contained in the inedible biomass, i.e., material in leachate, brought about phytotoxicity in the hydroponic culture of potato. Recalcitrant, water soluble organic material accumulated in all nutrient recycling treatments (650% increase after 105 days), but no increase in rhizosphere microbial numbers was observed.

  2. Continued Development of a Planetary Imaging Fourier Transform Spectrometer (PIFTS)

    NASA Technical Reports Server (NTRS)

    Sromovsky, L. A.

    2002-01-01

    This report describes continued efforts to evaluate a breadboard of a Planetary Imaging Fourier Transform Spectrometer (PIFTS). The PIFTS breadboard was developed under prior PIDDP funding. That effort is described in the final report for NASA Grant NAG5-6248 and in two conference papers (Sromovsky et al. 2000; Revercomb et al. 2000). The PIFTS breadboard was designed for near-IR (1-5.2 micrometer imaging of planetary targets with spectral resolving powers of several hundred to several thousand, using an InSb detector array providing at least 64x64 pixels imaging detail. The major focus of the development effort was to combine existing technologies to produce a small and low power design compatible with a very low mass flyable instrument. The objective of this grant (NAG5-10729) was further characterization of the breadboard performance, including intercomparisons with the highly accurate non-imaging Advanced Emitted Radiance Interferometer (AERI) (Revercomb et al. 1994; Best et al. 1997).

  3. Galileo infrared imaging spectrometry measurements at the Moon

    NASA Technical Reports Server (NTRS)

    Mccord, Thomas B.; Soderblom, Larry A.; Carlson, Robert W.; Fanale, Fraser P.; Lopes-Gautier, Rosaly; Ocampo, Adriano; Forsythe, Jennifer; Campbell, Bruce; Granahan, James C.; Smythe, W. D.

    1994-01-01

    Imaging spectrometer observations were made of the surface of the Moon during the December 1990 flyby of the Earth-Moon system by the Galileo spacecraft. This article documents this data set and presents analyses of some of the data. The near infrared mapping spectrometer (NIMS) investigation obtained 17 separate mosaics of the Moon in 408 spectral channels between about 0.7 and 5.2 micrometers. The instrument was originally designed to operate in orbit about Jupiter and therefore saturates at many spectral channels for most measurement situations at 1 AU. However, sufficient measurements were made of the Moon to verify the proper operation of the instrument and to demonstrate its capabilities. Analysis of these data show that the NIMS worked as expected and produced measurements consistent with previous ground-based telescopic studies. These are the first imaging spectrometer measurements of this type from space for the Moon, and they illustrate several major points concerning this type of observation and about the NIMS capabilities specifically. Of major importance are the difference between framing and scanning instruments and the effects of the spacecraft and the scan platform on the performance of such and experiment. The science return of subsequent NIMS and other investigation measurements will be significantly enhanced by the experience and results gained.

  4. Removing Atmospheric Effects From AVIRIS Data for Surface Reflectance Retrievals

    NASA Technical Reports Server (NTRS)

    Gao, Bo-Cai; Goetz, Alexander F. H.; Zamudio, J. A.

    1991-01-01

    Analysis of high resolution imaging spectrometer data requires a thorough compensation for atmospheric absorption and scattering. A method for retrieving surface reflectances from spectral data collected by the Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) is being developed. In this method, the integrated water vapor amount on a pixel by pixel basis is derived from the 0.94- and 1.14-micrometer water vapor features. The water vapor, carbon dioxide (CO2), oxygen (O2) and methane (CH4) transmission spectrum in the 0.4-2.5 micrometer region is calculated. The derived water vapor value and the solar and observational geometry are used in the spectral calculation. The AVIRIS spectrum is ratioed against the transmission spectrum to obtain the surface reflectance spectrum. Major mineral absorption features near 2.2 micrometer in retrieved reflectance spectra can be identified. Different vegetation absorption characteristics are observed. At present, the method is most useful for deriving surface reflectances from AVIRIS data measured on clear days with high visibilities. Atmospheric scattering effects will be included in our spectral calculations in the near future.

  5. Ceramic bearing technology program, volume 1: Final report. Final report, 1 August 1992-1 July 1995

    SciTech Connect

    Komanduri, R.; Lange, J.; Wicksted, J.; Krasinski, J.

    1995-07-01

    This project deals with the development of advanced manufacturing technologies for finishing silicon nitride balls and rollers for bearing applications and non-destructive inspection (NDI) methods for assessing surface damage of ceramic materials and to correlate the surface properties with tribological performance. Magnetic field assisted polishing was used for finishing the balls and magnetic abrasive finishing for finishing rollers. By applying low levels of controlled force (1 N/ball or less) the damage to the finished surface is expected to be minimal. Also chemomechanical polishing was used to minimize the brittle fracture. Using these techniques the polishing time was reduced from some 10 - 20 weeks to about 20 hours. The finish obtained was about 5-10 nm and the sphericity in the range of 0.5 - 1 micrometers. The non-destructive inspection (NDI) techniques used include Raman spectroscopy and radio frequency absorption (Lange), Brillouin scattering, and photoacoustic methods to detect surface damage. Inelastic Raman Light Scattering technique was found to be a rapid, non-contact method for characterizing the physical properties of the near-surface (approx. 2 micrometers) ceramic material in bearing balls. A number of features of the Raman spectra were demonstrated to be related to properties of the ceramic which are pertinent to the performance of the bearing balls.

  6. Precision optical asphere fabrication by plasma jet chemical etching (PJCE) and ion beam figuring

    NASA Astrophysics Data System (ADS)

    Schindler, Axel; Boehm, Georg; Haensel, Thomas; Frank, Wilfried; Nickel, Andreas; Rauschenbach, Bernd; Bigl, Frieder

    2001-12-01

    We develop a Plasma Jet Chemical Etching (PJCE) technique for high rate precision machining of optical materials aiming in a technology mature for precision asphere and free-form surface topology fabrication. The present contribution summarizes the achievements after about twelve months experience with a prototype production tool facility. PJCE is performed with the help of a microwave driven reactive plasma-jet working in a broad pressure range (10-600 mbar). We developed a moveable lightweight microwave plasma jet source for dwell time techniques performed in a roughly pumped process chamber equipped with a six axis system for precision workpiece and plasma source movement. Volume etch rates of some 10 mm3/min have been achieved for fused silica and silicon, respectively, using reactive (CF4,SF6,O2) and inert (Ar,He) gas mixtures and applying a microwave (2.45 GHz) power in the 100-200 W range. Large quartz plates (80-160 mm) have been figured using dwell time methods to achieve aspheric deformations of some 10 micrometers . The figured surfaces show shape errors of 1-2 micrometers and a microroughness of 50-100 nm RMS but no sub-surface damage enabling a small tool shape conserving post polishing up to the sub-nanometer roughness level. Thus, surface shaping to the nanometer error range can be done by ion beam finishing.

  7. Dust Aerosol, Clouds, and the Atmospheric Optical Depth Record over 5 Mars Years of the Mars Exploration Rover Mission

    NASA Technical Reports Server (NTRS)

    Lemmon, Mark T.; Wolff, Michael J.; Bell, James F., III; Smith, Michael D.; Cantor, Bruce A.; Smith, Peter H.

    2014-01-01

    Dust aerosol plays a fundamental role in the behavior and evolution of the Martian atmosphere. The first five Mars years of Mars Exploration Rover data provide an unprecedented record of the dust load at two sites. This record is useful for characterization of the atmosphere at the sites and as ground truth for orbital observations. Atmospheric extinction optical depths have been derived from solar images after calibration and correction for time-varying dust that has accumulated on the camera windows. The record includes local, regional, and globally extensive dust storms. Comparison with contemporaneous thermal infrared data suggests significant variation in the size of the dust aerosols, with a 1 micrometer effective radius during northern summer and a 2 micrometer effective radius at the onset of a dust lifting event. The solar longitude (L (sub s)) 20-136 degrees period is also characterized by the presence of cirriform clouds at the Opportunity site, especially near LS = 50 and 115 degrees. In addition to water ice clouds, a water ice haze may also be present, and carbon dioxide clouds may be present early in the season. Variations in dust opacity are important to the energy balance of each site, and work with seasonal variations in insolation to control dust devil frequency at the Spirit site.

  8. Cell fractionation with affinity ligands conjugated to agarose-polyacrolein microsphere beads.

    PubMed

    Margel, S; Ofarim, M; Eshhar, Z

    1983-07-01

    A new effective insoluble support useful for cell fractionation based on agarose-polyacrolein microsphere beads (APAMB) of diameters 150--250 micrometers has been developed. The synthesized polyacrolein (PA) microspheres, of average diameter 0.2 micrometer, are provided with reactive aldehyde groups through which various ligands containing primary amino groups are bound covalently in a single step at physiological pH. Antibodies coupled to the microspheres are very effective for labelling of cell surface receptors on human red blood cells and mouse lymphoid cells. APAMB were obtained by encapsulating the PA microspheres with agarose. Antibodies and lectins bound to the APAMB serve to construct affinity columns for the separation of red blood cells and murine lymphocyte subpopulations. Anti-human red blood cell antibodies coupled to anti-immunoglobulin APAMB are effective in separating human from turkey red blood cells, whereas either anti-Thy 1.2 anti-immunoglobulin antibodies or soybean agglutinin coupled to APAMB have proved useful for the separation of T and B cells from heterogeneous population of spleen cells. The separation procedure is simple, rapid and effective. The viability of the fractionated cells is unaffected by the procedure and the recovery of the cells is high: between 80% and 100%.

  9. NIST-BMDO transfer radiometer (BXR)

    NASA Astrophysics Data System (ADS)

    Jung, Timothy M.; Carter, Adriaan C.; Lorentz, Steven R.; Datla, Raju V.

    2000-07-01

    An infrared transfer radiometer has been recently developed at the Low-Background Infrared Calibration (LBIR) facility at the National Institute of Standards and Technology (NIST) for the Ballistic Missile Defense Organization (BMDO) program. The BMDO Transfer Radiometer (BXR) is designed to measure the irradiance of a collimated source of infrared light having an angular divergence of less than 1 mrad. It is capable of measuring irradiance levels as low as 10-15 W/cm2 over the spectral range from 2 micrometer to 30 micrometer. The radiometer uses an arsenic-doped silicon blocked impurity band (BIB) detector operated at temperatures below 12 K. Spectral resolution is provided by narrow bandpass interference filters and long-wavelength blocking filters. All the components of the radiometer, which include a mechanical shutter, an internal calibration source and detector, a long baffle section, a spatial filter, two filter wheels and a two- axis detector stage are cooled with an active flow of liquid helium to maintain temperatures below 20 K. A cryogenic vacuum chamber has been built to house the radiometer and to provide mechanical tilt alignment to the source. The radiometer is easily transported to a user site along with its support equipment.

  10. Fabrication of five-level ultraplanar micromirror arrays by flip-chip assembly

    NASA Astrophysics Data System (ADS)

    Michalicek, M. Adrian; Bright, Victor M.

    2001-10-01

    This paper reports a detailed study of the fabrication of various piston, torsion, and cantilever style micromirror arrays using a novel, simple, and inexpensive flip-chip assembly technique. Several rectangular and polar arrays were commercially prefabricated in the MUMPs process and then flip-chip bonded to form advanced micromirror arrays where adverse effects typically associated with surface micromachining were removed. These arrays were bonded by directly fusing the MUMPs gold layers with no complex preprocessing. The modules were assembled using a computer-controlled, custom-built flip-chip bonding machine. Topographically opposed bond pads were designed to correct for slight misalignment errors during bonding and typically result in less than 2 micrometers of lateral alignment error. Although flip-chip micromirror performance is briefly discussed, the means used to create these arrays is the focus of the paper. A detailed study of flip-chip process yield is presented which describes the primary failure mechanisms for flip-chip bonding. Studies of alignment tolerance, bonding force, stress concentration, module planarity, bonding machine calibration techniques, prefabrication errors, and release procedures are presented in relation to specific observations in process yield. Ultimately, the standard thermo-compression flip-chip assembly process remains a viable technique to develop highly complex prototypes of advanced micromirror arrays.

  11. Structural transformations in the a-tricalcium phosphate powders after mechanical activation and subsequent heat treatment

    NASA Astrophysics Data System (ADS)

    Shamray, V. F.; Karpihin, A. E.; Fedotov, A. Y.; Komlev, V. S.; Barinov, S. M.; Sirotinkin, V. P.

    2016-04-01

    X-ray diffraction analysis of the structural phase evolution in the a-TCP powder subjected to milling in the planetary mill in butanol, and followed by annealing at 1300 °C was performed. After milling, there was a systematic smoothing of the X-ray diffraction pattern of α-TCP. Significant changes in lattice constants and atomic parameters were not observed. The average particle size was reduced from 10 to 2 micrometers. The decrease of the size of coherently scattering domains CSD (250 to 80 nm) makes the main contribution to the X-ray lines broadening. The value of microstrain changes from 1 *10-6 to 2*10-4. After annealing at 1300 °C for 2 hours the phase with apatite structure was found. The content of the apatite phase increases with increasing of time of mechanical activation. Possible mechanisms of deformation of α-TCP particles and structural transformations α-TCP → HA are considered.

  12. Factors influencing the properties of fluoropolymer-based resists for 157-nm lithography

    NASA Astrophysics Data System (ADS)

    Taylor, Gary N.; Xu, Cheng-Bai; Teng, Gary; Leonard, JoAnne; Szmanda, Charles R.; Lawrence, William; Nur, Sassan; Brown, Kirk W.; Stephen, Al

    2002-07-01

    This paper describes characterization and lithographic results for one class of low absorbance fluoropolymers that were developed for use in 157 nm lithography. We discuss basic resist properties such as absorbance, hydrophobicity, thickness, resolution and profile for dense 1:1 and semi- dense 1:1.5-10 L/S features, reflection control and plasma etching resistance as a function of composition. Lithographic results were obtained on two types of substrates, silicon and SiON hardmask anti-reflectant. The results on the anti-reflectant were compared to those obtained from simulations using PROLITH. Some of the conclusions of this investigation are: Lower absorbance resists have higher hydrophobicity and better resolution; Resists with high hydrophobicity have very poor adhesion on SiOn, but have very good adhesion on Si and organic anti-reflectants; Only inorganic anti-reflectants have sufficient absorption to provide very low reflectance in <30nm thick films; 100 nm 1:1 L/S resolution is attained in 205 nm thick resist on Si at a resist absorption of 2.2/micrometers . The profile is tapered due to absorption; Adhesion to SiON has been achieved by polymer modification.

  13. Optical properties of ALON (aluminum oxynitride)

    NASA Astrophysics Data System (ADS)

    Hartnett, Thomas M.; Bernstein, Steven D.; Maguire, Edward A.; Tustison, Randal W.

    1997-06-01

    Aluminum oxynitride or ALON is a transparent polycrystalline ceramic material having high strength (380 MPa) and hardness (1950 kg/mm2). The transmission range of ALON extends from 0.2 micrometer in the UV through the visible to 6.0 micrometer in the infrared. This material is made by conventional powder processing and sintering a powder compact to full density and optical transparency. Powder compacts of near net shape and size are made by conventional dry pressing, by slip casting, and by injection molding methods. This gives the material great latitude in size and shape capabilities not afforded by materials formed by single crystal growth methods. Intrinsic transparency extending from ultraviolet wavelengths (UV) to mid-infrared wavelengths (MID-IR) and low levels of optical scatter have been achieved. In this paper recent measurements of the spectral dependence of forward optical scatter, the spectral emittance from room temperature to 1200 degrees Celsius, and the index of refraction (n) of ALON are presented. Literature values for the changes in refractive index with temperature (dn/dT) are compared.

  14. Confocal microscopy of excised human skin using acetic acid and crossed polarization: rapid detection of nonmelanoma skin cancers

    NASA Astrophysics Data System (ADS)

    Rajadhyaksha, Milind M.; Menaker, Gregg; Gonzalez, Salvador

    2000-05-01

    Moh's micrographic surgery for basal- and squamous-cell cancers (BCCs, SCCs) involves precise excision of the tumor with minimal damage to the surrounding normal skin. Precise excision is guided by histopathologic examination for tumor margins; typically, 2 - 4 slices of skin are excised, and there is a waiting time of 15 - 45 minutes for the surgeon and patient while each slice is being processed for histopathology. We can avoid the processing by using a confocal reflectance microscope; confocal detection of BCCs and SCCs is possible after staining the nuclei in the excised skin with 5% acetic acid, and imaging in crossed polarization. The cancerous nuclei appear bright against the dark surrounding normal dermis. The contrast is due to increased back-scattering as well as increased depolarization from the intra-nuclear structure relative to that from the surrounding normal dermis. As in conventional histopathology, the tumors are first detected at low resolution (section thickness 20 micrometer) in a wide field (1-2 mm); nuclear morphology is then viewed at high resolution (section thickness 2 micrometer) in a small field (0.25 - 0.50 mm). Mosaics of images are assembled to produce confocal maps of the BCCs or SCCs within large excised tissue. Rapid detection (within minutes) is possible.

  15. Hydrochemical data for the Truckee River drainage system, California and Nevada

    SciTech Connect

    Benson, L.V.

    1984-01-01

    Surface-water samples were collected from the Truckee River drainage system during 1975, 1976, and 1981. Data resulting from chemical analyses of these samples, as well as certain other previously unpublished data, are tabulated in this report. The report contains the following hydrochemical data: (1) chemical composition of 21 tributaries to Lake Tahoe and the Truckee River upstream from Farad, California (May and October 1971, and June 1972); (2) chemical composition of the Truckee River at Tahoe City (January 1968 to January 1975) and at Farad, California (January 1968 to June 1980), and of the Little Truckee River upstream from Stampede Reservoir, California (January 1968 to April 1980); (3) chemical composition of the Truckee River at 11 sites from Tahoe City, California, to Nixon, Nevada (June 4 and September 3, 1975); (4) historical chemical analyses of water from Pyramid Lake, Nevada (1882 to 1973); (5) chemical composition (November 1975 to December 1976), water temperature (January 1976 to November 1977), and dissolved oxygen (January 1976 to November 1977) at various depths in Pyramid Lake, Nevada; (6) chemical composition of pore fluids from and carbonate mineralogy of sediment greater than 2 micrometers in five cores, Pyramid Lake, Nevada; (7) chemical composition of the Truckee River at Farad, California (January to July 1981); and (8) chemical composition of tufa from the Pyramid Lake basin. 9 references, 3 figures, 14 tables.

  16. Flat-plate solar array project process development area process research of non-CZ silicon material

    NASA Technical Reports Server (NTRS)

    1985-01-01

    Three sets of samples were laser processed and then cell processed. The laser processing was carried out on P-type and N-type web at laser power levels from 0.5 joule/sq cm to 2.5 joule/sq cm. Six different liquid dopants were tested (3 phosphorus dopants, 2 boron dopants, 1 aluminum dopant). The laser processed web strips were fabricated into solar cells immediately after laser processing and after various annealing cycles. Spreading resistance measurements made on a number of these samples indicate that the N(+)P (phosphorus doped) junction is approx. 0.2 micrometers deep and suitable for solar cells. However, the P(+)N (or P(+)P) junction is very shallow ( 0.1 micrometers) with a low surface concentration and resulting high resistance. Due to this effect, the fabricated cells are of low efficiency. The maximum efficiency attained was 9.6% on P-type web after a 700 C anneal. The main reason for the low efficiency was a high series resistance in the cell due to a high resistance back contact.

  17. Radioisotope assay for 1-aminocyclopropane-1-carboxylic acid synthase: s-adenosylhomocysteine analogs as inhibitors of the enzyme involved in plant senescence

    SciTech Connect

    Miura, G.A.; Chiang, P.K.

    1985-01-01

    A simple and rapid radioisotopic assay for 1-aminocyclopropane-1-carboxylic acid (ACC) synthase was developed, an enzyme involved in the biosynthesis of the plant hormone ethylene. The assay utilizes an AG50-X4(NH4 (+)) column which separates S-adenosyl-L-(carboxyl-/sup 14/C)methionine (AdoMet) from the product (/sup 14/C)acc, since the latter is not bound to the resin while (/sup 14/C)adoMet is. As opposed to other assays, this procedure measures ACC directly and does not require further conversion to ethylene. When an enzyme preparation from ripe-tomato fruits (Lycopersicon esculentum Mill) was assayed, an I/sub 50/ of 2.5 + or - 0.8 micrometers for sinefungin and a K/sub m/ of 27 + or - 2 micrometers for AdoMet were obtained; these values were in good agreement with previous previous determinations made with a gas-chromatographic assay. When other nucleosides were tested as inhibitors the following order of decreasing activity was found: sinefungin, S-adenosylhomocysteine (AdoHcy), AdoHcy sulfoxide, S-n-butyladenosine, 3-deaza-adenosylhomocysteine, S-isobutyladenosine, S-isobutyladenosine, S-isobutyl-l-deazaadenosine. In contrast, S-isobutyl-3-deazaadenosine, S-isobutyl-7-deazaadenosine, 3-deazaadenosine, and adenodine were not inhibitory.

  18. New semiconductor diode laser emitting at 2 um for microsurgery applications

    NASA Astrophysics Data System (ADS)

    Gobbi, Pier Giorgio; Ragazzi, D.; Azzolini, Claudio; Trabucchi, Giuseppe; Brancato, Rosario

    1996-01-01

    A surgical laser instrument is presented, based on a semiconductor diode emitting in the spectral region around 2 micrometer, in continuous mode. At this wavelength tissue absorption is via histological water, and the interaction is purely thermal. A portable laser station was built, emitting up to 250 mW of optical power at 1.94 micrometers, out of the tip of a low- hydroxil fused-silica optical fiber of 200 micrometer diameter. Experiments have been performed both in vitro with enucleated porcine eyes and in vivo, on rabbits and rats. In vitreo-retinal surgery, retinectomies and incisions of epiretinal fibrotic membranes have been achieved. At reduced output power the laser radiation has been applied to the welding of tissues, in particular cornea, sclera and skin, with interesting results. This new laser source, characterized by ergonomic advantages like compactness, portability, long lifetime, reduced maintenance, is potentially attractive for a number of microsurgical procedures like micro- incisions, shallow coagulations, and welding of hydrated biological membranes.

  19. The Synergistic Effect of Leukocyte Platelet-Rich Fibrin and Micrometer/Nanometer Surface Texturing on Bone Healing around Immediately Placed Implants: An Experimental Study in Dogs

    PubMed Central

    Neiva, Rodrigo F.; Gil, Luiz Fernando; Tovar, Nick; Janal, Malvin N.; Marao, Heloisa Fonseca; Pinto, Nelson; Coelho, Paulo G.

    2016-01-01

    Aims. This study evaluated the effects of L-PRF presence and implant surface texture on bone healing around immediately placed implants. Methods. The first mandibular molars of 8 beagle dogs were bilaterally extracted, and implants (Blossom™, Intra-Lock International, Boca Raton, FL) were placed in the mesial or distal extraction sockets in an interpolated fashion per animal. Two implant surfaces were distributed per sockets: (1) dual acid-etched (DAE, micrometer scale textured) and (2) micrometer/nanometer scale textured (Ossean™ surface). L-PRF (Intraspin system, Intra-Lock International) was placed in a split-mouth design to fill the macrogap between implant and socket walls on one side of the mandible. The contralateral side received implants without L-PRF. A mixed-model ANOVA (at α = 0.05) evaluated the effect of implant surface, presence of L-PRF, and socket position (mesial or distal), individually or in combination on bone area fraction occupancy (BAFO). Results. BAFO values were significantly higher for the Ossean relative to the DAE surface on the larger mesial socket. The presence of L-PRF resulted in higher BAFO. The Ossean surface and L-PRF presence resulted in significantly higher BAFO. Conclusion. L-PRF and the micro-/nanometer scale textured surface resulted in increased bone formation around immediately placed implants. PMID:28042577

  20. Optical coherence microscopy for the in-depth study of biological structures: system based on a parallel detection scheme

    NASA Astrophysics Data System (ADS)

    Beaurepaire, Emmanuel; Gleyzes, Philippe; Lebec, Martial; Blanchot, Loic; Saint-Jalmes, Herve; Boccara, Albert C.

    1998-04-01

    We present a new microscopy system based on the OCT principle, that uses a multiplexed lock-in detection scheme to generate a 2D head-on image in parallel without lateral scanning. Our 'full-field optical coherence microscopy' comprises a Michelson interferometer built with a polarizing beam splitter, and uses a photoelastic birefringence modulator to modulate the optical path difference between the two orthogonal polarizations. A novel signal processing method is used to achieve a demodulation in parallel on every pixel of a 256 X 256 CCD camera. A 840 nm electroluminescent diode with 20 micrometers coherence length is used to illuminate the field of view through the microscope objective lens. In-depth exploration of the sample is realized by changing the plane of focus. The lateral resolution of the images is limited by the camera pixel size and is 2 micrometers . The axial sectioning ability is approximately 8 micrometers . Having validated our setup on model samples, we now evaluate its performance on biological structures. As an example, images of onion cells from 50-400 micrometers below the surface are obtained in 1 s with 100 dB sensitivity.

  1. Interrelationships Between Aerosol Characteristics and Light Scattering During Late-winter in a Eastern Mediterranean Arid Environment

    NASA Technical Reports Server (NTRS)

    Ichoku, C.; Andreae, M. O.; Meixner, F. X.; Schebeske, G.; Formenti, P.; Maenhaut, W.; Cafmeyer, J.; Ptasinski, J.; Karnieli, A.; Orlovsky, L.

    1999-01-01

    An intensive field campaign involving measurement of various aerosol physical, chemical, and radiative properties was conducted at Sde Boker in the Negev Desert of Israel, from 18 February to 15 March 1997. Nephelometer measurements gave average background scattering coefficient values of about 25 M/m at 550 nm wavelength, but strong dust events caused the value of this parameter to rise up to about 800 M/m Backscattering fractions did not depend on aerosol loading, and generally fell in the range of 0.1 to 0.25, comparable to values reported for marine and Arctic environments. Chemical analysis of the aerosol revealed that, in the coarse size range (2 - 10 micrometer equivalent aerodynamic diameter (EAD)), calcium (Ca) was by far the most abundant element followed by silicon (Si), both of which are indicators for mineral dust. In the fine size fraction (< 2 micrometers EAD), sulfur (S) generally was the dominant element, except during high dust episodes when Ca and Si were again the most abundant. Furthermore, fine black carbon (BC) correlates with S, suggesting that they may have originated from the same sources or source regions. An indication of the short-term effect of aerosol loading on radiative forcing was provided by measurements of global and diffuse solar radiation, which showed that during high turbidity periods (strong dust events) almost all of the solar radiation reaching the area is scattered or absorbed.

  2. Detailed analysis of carrier transport in InAs(0.3)Sb(0.7) layers grown on GaAs substrates by metalorganic chemical-vapor deposition

    NASA Astrophysics Data System (ADS)

    Besikci, C.; Choi, Y. H.; Labeyrie, G.; Bigan, E.; Razeghi, M.; Cohen, J. B.; Carsello, J.; Dravid, V. P.

    1994-11-01

    InAs(0.3)Sb(0.7) layers with mirrorlike morphology have been grown on GaAs substrates by low-pressure metalorganic chemical vapor deposition. A room-temperature electron Hall mobility of 2 x 10(exp 4) sq cm/(V s) has been obtained for a 2-micrometer-thick layer. Low temperature resistivity of the layers depended on TMIn flow rate and layer thickness. Hall mobility decreased monotonically with decreasing temperature below 300 K. A 77 K conductivity profile has shown an anomalous increase in the sample conductivity with decreasing thickness except in the near vicinity of the heterointerface. Experimental and theoretical results suggest that the combined effects of the dislocations generated by the large lattice mismatch and strong surface inversion may lead to deceptive Hall measurements by reflecting typical n-type behavior for a p-type sample, and the measured carried concentration may considerably be affected by the surface conduction up to near room temperature. A quantitative analysis of dislocation scattering has shown significant degradation in electron mobility for dislocation densities above 10(exp 7)/sq cm. The effects of dislocation scattering on hole mobility have been found to be less severe. It has also been observed that there is a critical epilayer thickness (approximately 1 micrometer) below which the surface electron mobility is limited by dislocation scattering.

  3. Compact VLSI neural computer integrated with active pixel sensor for real-time ATR applications

    NASA Astrophysics Data System (ADS)

    Fang, Wai-Chi; Udomkesmalee, Gabriel; Alkalai, Leon

    1997-04-01

    A compact VLSI neural computer integrated with an active pixel sensor has been under development to mimic what is inherent in biological vision systems. This electronic eye- brain computer is targeted for real-time machine vision applications which require both high-bandwidth communication and high-performance computing for data sensing, synergy of multiple types of sensory information, feature extraction, target detection, target recognition, and control functions. The neural computer is based on a composite structure which combines Annealing Cellular Neural Network (ACNN) and Hierarchical Self-Organization Neural Network (HSONN). The ACNN architecture is a programmable and scalable multi- dimensional array of annealing neurons which are locally connected with their local neurons. Meanwhile, the HSONN adopts a hierarchical structure with nonlinear basis functions. The ACNN+HSONN neural computer is effectively designed to perform programmable functions for machine vision processing in all levels with its embedded host processor. It provides a two order-of-magnitude increase in computation power over the state-of-the-art microcomputer and DSP microelectronics. A compact current-mode VLSI design feasibility of the ACNN+HSONN neural computer is demonstrated by a 3D 16X8X9-cube neural processor chip design in a 2-micrometers CMOS technology. Integration of this neural computer as one slice of a 4'X4' multichip module into the 3D MCM based avionics architecture for NASA's New Millennium Program is also described.

  4. Optical properties and infrared optics applications of composite films based on polyethylene and low-melting-point chalcogenide glass

    NASA Astrophysics Data System (ADS)

    Bormashenko, Edward; Pogreb, Roman; Sutovski, Semion; Levin, Mark

    2002-02-01

    A novel composite material based on medium-density polyethylene and thermoplastic chalcogenide glass has been produced. Both materials are highly transparent in the middle and far IR, but their refractive indices differ dramatically. The polymer and the glass have nearly equal viscosities at the temperature of polyethylene processing. This fact allowed the use of extrusion for homogenization. Single- and twin-screw extrusion processes yielded compositions that contain up to 40% of chalcogenide glass particles, which were dispersed in the polymer matrix. Highly homogeneous compositions that contain perfectly spherical glass particles 1 to 2 micrometers in diameter dispersed in the polymer matrix were obtained. Highly oriented structures involving chalcogenide glass fibers immersed in the polymer matrix were prepared at high stretch speeds. It was established that it is possible to produce a composite that is opaque in the visible and near IR, and highly transparent in the 2 to 25-micrometers wavelength band. The use of oriented films as IR laser light-shaping diffusers is possible. The composite films obtained were tried successfully as immersion adhesive layers for the contacting of IR fibers.

  5. GESE: A Small UV Space Telescope to Conduct a Large Spectroscopic Survey of Z-1 Galaxies

    NASA Technical Reports Server (NTRS)

    Heap, Sara R.; Gong, Qian; Hull, Tony; Kruk, Jeffrey; Purves, Lloyd

    2013-01-01

    One of the key goals of NASA's astrophysics program is to answer the question: How did galaxies evolve into the spirals and elliptical galaxies that we see today? We describe a space mission concept called Galaxy Evolution Spectroscopic Explorer (GESE) to address this question by making a large spectroscopic survey of galaxies at a redshift, z is approximately 1 (look-back time of approximately 8 billion years). GESE is a 1.5-meter space telescope with an ultraviolet (UV) multi-object slit spectrograph that can obtain spectra of hundreds of galaxies per exposure. The spectrograph covers the spectral range, 0.2-0.4 micrometers at a spectral resolving power, R approximately 500. This observed spectral range corresponds to 0.1-0.2 micrometers as emitted by a galaxy at a redshift, z=1. The mission concept takes advantage of two new technological advances: (1) light-weighted, wide-field telescope mirrors, and (2) the Next- Generation MicroShutter Array (NG-MSA) to be used as a slit generator in the multi-object slit spectrograph.

  6. Bondability of Al-Si thin film in thermosonic gold wire bonding. [integrated circuits

    NASA Technical Reports Server (NTRS)

    Nakagawa, K.; Miyata, K.; Banjo, T.; Shimada, W.

    1985-01-01

    The bondability of two kinds of Al-Si thin films in thermosonic Au wire bonding was examined by means of microshear tests. One type of film was formed by sputtering an Al-2% Si alloy, and the other was formed by depositing an 0.05 micrometer-thick polysilicon layer on SiO2 by chemical vapor deposition (CVD) and then depositing a 1.2 micrometer-thick Al layer on them by evaporation. After heat-treatment at 450 deg for 30 min., Si in the Al-Si film crystallized. The grain size of the crystallized Si affects the thermosonic wire bondability, i.e., for Al-2% Si sputtered films, good bondability was obtained under relatively small (1.0 micrometer) grain size conditions. In the successive layer process, on the other hand, the grain size of crystallized Si varies with the polysilicon CVD temperature. The optimum CVD temp. was determined from the standpoint of bondability with respect to grain size.

  7. Effect of Increased Cyclic AMP Concentration on Muscle Protein Synthesis and Beta-Adrenergic Receptor Expression in Chicken Skeletal Muscle Cells in Culture

    NASA Technical Reports Server (NTRS)

    Young, R. B.; Vaughn, J. R.; Bridge, K. Y.; Smith, C. K.

    1998-01-01

    Analogies of epinephrine are known to cause hypertrophy of skeletal muscle when fed to animals. These compounds presumably exert their physiological action through interaction with the P-adrenergic receptor. Since the intracellular signal generated by the Beta-adrenergic receptor is cyclic AMP (cAMP), experiments were initiated in cell culture to determine if artificial elevation of cAMP by treatment with forskolin would alter muscle protein metabolism and P-adrenergic receptor expression. Chicken skeletal muscle cells after 7 days in culture were treated with 0.2-30 micrometers forskolin for a total of three days. At the end of the treatment period, both the concentration of cAMP and the quantity of myosin heavy chain (MHC) were measured. Concentration of cAMP in forskolin-treated cells increased up to 10-fold in a dose dependent manner. In contrast, the quantity of MHC was increased approximately 50% above control cells at 0.2 micrometers forskolin, but exhibited a gradual decline at higher levels of forskolin so that the quantity of MHC in cells treated with 30 micrometers forskolin was not significantly different from controls. Curiously, the intracellular concentration of cAMP which elicited the maximum increase in the quantity of MHC was only 40% higher than cAMP concentration in control cells.

  8. NIMS Radiance Point Spectra of Ida and Dactyl V1.0

    NASA Astrophysics Data System (ADS)

    Granahan, J. C.

    2013-08-01

    This data volume contains radiometrically corrected point spectra of asteroid 243 Ida and a spectrum of the asteroid satellite Dactyl (Ida I) as acquired by the Galileo spacecraft Near Infrared Mapping Spectrometer (NIMS) on August 28, 1993. They record the spectra collected as the Galileo spacecraft approached the 243 Ida system. These data are products of the calibration of the raw data number files idu002tn.qub, idu005tn.qub, idu006tn.qub, idu007tn.qub, idu019tn.qub, idu020tn.qub, idu022tn.qub, idu028tn.qub, idu032tn.qub, idu033tn.qub, and idu035tn.qub (DATA SET ID ='GO-A-NIMS-3-TUBE-V1.0') with calibration factors acquired during the Jovian tour of the Galileo mission. These raw data .qub files are archived in the Imaging Node of the NASA Planetary Data System (PDS). The calibrated spectra consist of radiance and incidence/flux measurements for wavelengths between 0.7 - 5.2 micrometers.

  9. Hollow optical waveguides with omni-directional reflectors

    NASA Astrophysics Data System (ADS)

    Lo, Shih-Shou; Hou, Chia-Hung; Chien, Hung-Ta; Hsiao, Fu-Li; Chen, Chii-Chang

    2005-03-01

    In this study, we design and fabricate a hollow optical waveguide with omni-directional reflectors in silicon-based materials. A groove is etched by inductive coupled plasma (ICP) with photolithographic process on (100) silicon wafer. The width of the groove is varied from 3.5 to 5.5 micrometer for different waveguide designs. The depth of the groove is 1.2 micrometers. Plasma enhanced chemical vapor deposition is used to deposit six pairs of Si/SiO2(0.111/0.258micrometers) on the samples. Finally, the top of the sample is covered by another silicon substrate on which the identical omni-directional reflector has been also deposited. By wafer bonding technology, the top omni-directional reflector can be combined with the groove to form a hollow optical waveguide. Light with the wavelength at 1.55 micrometers can be confined by the omni-directional reflectors at single mode operation. Polarization independent hollow optical waveguides can be achieved with this fabrication process.

  10. Physical properties of asteroids

    NASA Technical Reports Server (NTRS)

    Veeder, Glenn J.

    1988-01-01

    Infrared photometry at 1.2, 1.6 and 2.2 micrometer provides a relatively rapid and accurate method for the classification of asteroids and is important for comparison with laboratory measurements of meteorites and other possible compositional analogues. Extension beyond the visual is espicially useful for minerals which have strong characteristic infrared colors such as olivine in the A class asteroids. Radiometry at long infrared wavelengths is important for deriving basic physical parameters (via thermal models) such as size and albedo which in turn enables the conversion of relative colors to absolute reflectances. In particular, albedos are the only way to distinguish among the otherwise ambiguous E, M and P classes of asteroids. Infrared observations of 15 asteroids were made at the NASA infrared Telescope Facility (IRTF) on Mauna Kea in 1987. Researchers completed the analysis of 22 Aten, Apollo and Amor asteroids. Results include albedos and diameters for these objects as well as the identification of the first known class M and Class E near-Earth asteroids. The standard thermal model appears to be inadequate for some of these small asteroids because of their coarse regolith, so researchers constructed a rotating thermal model for such asteroids. They have identified a subtle systematic difference between the sub-populations of large and small IRAS asteroids as well as several anomalous objects.

  11. Selective evaporation of focusing fluid in two-fluid hydrodynamic print head.

    SciTech Connect

    Keicher, David M.; Cook, Adam W.

    2014-09-01

    The work performed in this project has demonstrated the feasibility to use hydrodynamic focusing of two fluid steams to create a novel micro printing technology for electronics and other high performance applications. Initial efforts focused solely on selective evaporation of the sheath fluid from print stream provided insight in developing a unique print head geometry allowing excess sheath fluid to be separated from the print flow stream for recycling/reuse. Fluid flow models suggest that more than 81 percent of the sheath fluid can be removed without affecting the print stream. Further development and optimization is required to demonstrate this capability in operation. Print results using two-fluid hydrodynamic focusing yielded a 30 micrometers wide by 0.5 micrometers tall line that suggests that the cross-section of the printed feature from the print head was approximately 2 micrometers in diameter. Printing results also demonstrated that complete removal of the sheath fluid is not necessary for all material systems. The two-fluid printing technology could enable printing of insulated conductors and clad optical interconnects. Further development of this concept should be pursued.

  12. Dispersion of SiO2-based nanocomposites with high performance liquid chromatography.

    PubMed

    Wang, Jun; White, William B; Adair, James H

    2006-03-16

    Core-shell structured Ag/SiO2 nanocomposite has been synthesized by a cyclohexane/Igepal/water reverse micelle system. The spherical nanocomposite particles were washed and concentrated with high performance liquid chromatography (HPLC) to remove the surfactant added during synthesis. Spherical SiO2 micrometer-scale particles were packed in the HPLC column as a stationary phase for the washing and dispersing of Ag/SiO2 nanocomposite particles. Surface modification of Ag/SiO2 nanocomposite particles and SiO2 microspheres with silane coupling agent enhanced the surface charge of the particles and improved the efficiency of washing with HPLC. Well-dispersed Ag/SiO2 stable suspensions were successfully attained in ethanol/water mixed solvents after HPLC washing. The state of dispersion for the Ag/SiO2 nanocomposite suspension was systematically assessed using dynamic light scattering (DLS) and transmission electron microscope (TEM) and spin coat/atomic force microscope (AFM) analyses. The mechanism of the enabling HPLC washing protocol for SiO2-based nanoparticles is discussed.

  13. 13CO2/12CO2 ratio analysis in exhaled air by lead-salt tunable diode lasers for noninvasive diagnostics in gastroenterology

    NASA Astrophysics Data System (ADS)

    Stepanov, Eugene V.; Zyrianov, Pavel V.; Miliaev, Valerii A.; Selivanov, Yurii G.; Chizhevskii, Eugene G.; Os'kina, Svetlana; Ivashkin, Vladimir T.; Nikitina, Elena I.

    1999-07-01

    An analyzer of 13CO2/12CO2 ratio in exhaled air based on lead-salt tunable diode lasers is presented. High accuracy of the carbon isotope ratio detection in exhaled carbon dioxide was achieved with help of very simple optical schematics. It was based on the use of MBE laser diodes operating in pulse mode and on recording the resonance CO2 absorption at 4.2 micrometers . Special fast acquisition electronics and software were applied for spectral data collection and processing. Developed laser system was tested in a clinical train aimed to assessment eradication efficiency in therapy of gastritis associated with Helicobacter pylori infection. Data on the 13C-urea breath test used for P.pylori detection and obtained with tunable diode lasers in the course of the trail was compared with the results of Mass-Spectroscopy analysis and histology observations. The analyzer can be used also for 13CO2/12CO2 ratio detection in exhalation to perform gastroenterology breath test based on using other compounds labeled with stable isotopes.

  14. Microbiologic quality assurance for intravenous admixtures in a small hospital.

    PubMed

    Doss, H L; James, J D; Killough, D M; Snodgrass, G L

    1982-05-01

    A simple, inexpensive method for end-product testing of intravenous admixtures for microbial contamination was developed and tested by challenging the system with low levels of microbial contamination. The 16-step procedure for testing i.v. admixtures for microbial contamination used total-sample membrane filtration A 0.2-micrometers Nalgene filter unit was used; the entire contents of randomly selected admixtures were to be filtered and discarded under the procedure. Filters were incubated on sheep-blood agar plates for 48 hours at 35 degrees C. Low concentrations (Klebsiella pneumoniae and Pseudomonas aeruginosa were used to contaminate admixtures deliberately to challenge the system. Seventy-two solutions were contaminated with each microbe; 72 other solutions were inoculated with sterile 0.9% sodium chloride; and 72 uninoculated solutions served as controls. Filtration was performed on a laboratory bench to prevent contamination of the laminar-flow hood. In deliberately contaminated solutions, a mean of 82% of inoculated organisms was isolated by membrane filtration. Five instances of adventitious contamination were noted among the 288 samples; these occurred across all experimental groups. Cost per sample was $4-5. This system can be used by hospital pharmacists to produce documentation of quality assurance that will be acceptable in terms of cost, simplicity, and accuracy.

  15. Aryl hydrocarbon hydroxylase (AHH) induction by polybrominated biphenyls (PBBs): enchancement by photolysis.

    PubMed

    Robertson, L W; Parkinson, A; Chittim, B; Bandiera, S; Sawyer, T W; Safe, S

    1981-01-01

    Irradiation of the commercial polybrominated biphenyl (PBB( mixture, fireMaster BP-6, in cyclohexane solution at 300 nm for 930 min resulted in a marked diminution of the major components of the mixture. Administration of the photolyzed PBB mixture of fireMaster BP-6 to immature male Wistar rats caused both dose-related decreases in thymus weight and increase in hepatic microsomal benzo[a]pyrene hydroxylase (AHH), 4-dimethylaminoantipyrine N-demethylase and NADPH-cytochrome c reductase activities and cytochrome P-450 content. The dose effecting half-maximal AHH induction for the photolyzed PBBs (9 mg . KG-1) was approximately 6 times lower than that of fireMaster BP-6 (50 mg. kg-1). Furthermore, the concentration of photolyzed PBBs (2 micrometers) required to displace 50% of the specifically-bound [3H] TCDD from its high-affinity cytosolic Ah receptor was approximately 150 times lower than that required for fireMaster BP-6 (300 micrometers), as measured by sucrose density gradient centrifugation analysis. The results suggest that the photolysis of the commercial PBB mixture yields products which possess increased biologic activity.

  16. Separation and Detection of Toxic Gases with a Silicon Micromachined Gas Chromatography System

    NASA Technical Reports Server (NTRS)

    Kolesar, Edward S.; Reston, Rocky R.

    1995-01-01

    A miniature gas chromatography (GC) system was designed and fabricated using silicon micromachining and integrated circuit (IC) processing techniques. The silicon micromachined gas chromatography system (SMGCS) is composed of a miniature sample injector that incorporates a 10 microliter sample loop; a 0.9 meter long, rectangular shaped (300 micrometer width and 10 micrometer height) capillary column coated with a 0.2 micrometer thick copper phthalocyanine (CuPc) stationary phase; and a dual detector scheme based upon a CuPc-coated chemiresistor and a commercially available 125 micrometer diameter thermal conductivity detector (TCD) bead. Silicon micromachining was employed to fabricate the interface between the sample injector and the GC column, the column itself, and the dual detector cavity. A novel IC thin-film processing technique was developed to sublime the CuPc stationary phase coating on the column walls that were micromachined in the host silicon wafer substrate and Pyrex (r) cover plate, which were then electrostatically bonded together. The SMGCS can separate binary gas mixtures composed of parts-per-million (ppm) concentrations of ammonia (NH3) and nitrogen dioxide (NO2) when isothermally operated (55-80 degrees C). With a helium carrier gas and nitrogen diluent, a 10 microliter sample volume containing ammonia and nitrogen dioxide injected at 40 psi ((2.8 x 10(exp 5)Pa)) can be separated in less than 30 minutes.

  17. Heart cell contractions measured using a micromachined polysilicon force transducer

    NASA Astrophysics Data System (ADS)

    Lin, Gisela; Pister, Kristofer S. J.; Roos, Kenneth P.

    1995-09-01

    A microelectromechanical systems (MEMS) force transducer, with a volume less than one cubic millimeter, is being developed to measure forces generated by living, isolated cardiac muscle cells in order to resolve the complex mechanisms of muscle contraction. The force transducer consists of two movable clamps facing each other. Each clamp contains two vertical, parallel hinged polysilicon plates attached to a moveable shuttle, and the entire structure is suspended 2 micrometers above the substrate via support beams attached to the substrate at one end. Each end of a living rat heart cell is glued between a pair of vertical plates. Calcium is then introduced into the cell's nutrient bath and stimulates the cell to contract. Upon contraction the support beams bend, and the amount of deflection is translated to force via the known spring constant in the beams. Typcially the 70 micrometers long central portion of a 120 micrometers long cell will contract approximately 6-7 micrometers in full activating solution, resulting in forces up to 16 (mu) N. The average value obtained for Fmax per cross-sectional area was 21.8mN/mm2 which is comparable to the value found in other laboratories using standard transducer technology.

  18. Noninvasive detection of cardiovascular pulsations by optical Doppler techniques

    NASA Astrophysics Data System (ADS)

    Hong, HyunDae; Fox, Martin D.

    1997-10-01

    A system has been developed based on the measurement of skin surface vibration that can be used to detect the underlying vascular wall motion of superficial arteries and the chest wall. Data obtained from tissue phantoms suggested that the detected signals were related to intravascular pressure, an important clinical and physiological parameter. Unlike the conventional optical Doppler techniques that have been used to measure blood perfusion in skin layers and blood flow within superficial arteries, the present system was optimized to pick up skin vibrations. An optical interferometer with a 633-nm He:Ne laser was utilized to detect micrometer displacements of the skin surface. Motion velocity profiles of the skin surface near each superficial artery and auscultation points on a chest for the two heart valve sounds exhibited distinctive profiles. The theoretical and experimental results demonstrated that the system detected the velocity of skin movement, which is related to the time derivative of the pressure. The system also reduces the loading effect on the pulsation signals and heart sounds produced by the conventional piezoelectric vibration sensors. The system's sensitivity, which could be optimized further, was 366.2 micrometers /s for the present research. Overall, optical cardiovascular vibrometry has the potential to become a simple noninvasive approach to cardiovascular screening.

  19. Determination of the Contact Angle Based on the Casimir Effect

    NASA Technical Reports Server (NTRS)

    Mazuruk, K.; Volz, M. P.

    2015-01-01

    In several crystal growth processed based on capillarity, a melt comes into contact with a crucible wall at an angle defined as the contact angle. For molten metals and semiconductors, this contact angle is dependent upon both the crucible and melt material and typical values fall in the range 80-170deg. However, on a microscopic scale, there does not exist a precise and sharp contact angle but rather the melt and solid surfaces merge smoothly and continuously over a distance of up to several micrometers. Accurate modeling requires a more advanced treatment of this interaction. The interaction between the melt and solid surfaces can be calculated by considering two forces: a short-range repulsive force and a longer range (up to a few micrometers) Casimir force. The Casimir force between the two bodies of complex geometry is calculated using a retarded temperature Green's function (Matsubara type) for the photon in the medium. The governing equations are cast in the form of a set of boundary integral equations which are then solved numerically for the case of molten Ge on SiO2. The shape of the molten surface approaching the flat solid body is determined, and the contact angle is defined as the angle between the two surfaces at the microscopically asymptotic distance of 1-2 micrometers. The formulation of this model and the results of the numerical calculations will be presented and discussed.

  20. Hydrogen and fluorine in the surfaces of lunar samples

    NASA Technical Reports Server (NTRS)

    Leich, D. A.; Goldberg, R. H.; Burnett, D. S.; Tombrello, T. A.

    1974-01-01

    The resonant nuclear reaction F-19 (p, alpha gamma)0-16 has been used to perform depth sensitive analyses for both fluorine and hydrogen in lunar samples. The resonance at 0.83 MeV (center-of-mass) in this reaction has been applied to the measurement of the distribution of trapped solar protons in lunar samples to depths of about 1/2 micrometer. These results are interpreted in terms of terrestrial H2O surface contamination and a redistribution of the implanted solar H which has been influenced by heavy radiation damage in the surface region. Results are also presented for an experiment to test the penetration of H2O into laboratory glass samples which have been irradiated with 0-16 to simulate the radiation damaged surfaces of lunar glasses. Fluorine determinations have been performed in a 1 pm surface layer on lunar samples using the same F-19 alpha gamma)0-16 resonance. The data are discussed from the standpoint of lunar fluorine and Teflon contamination.

  1. Dimensions of calcium release domains in frog skeletal muscle fibers

    NASA Astrophysics Data System (ADS)

    Vergara, Julio L.; DiFranco, Marino; Novo, David

    2001-07-01

    The spatiotemporal properties of the Ca2+ release process in skeletal muscle fibers were determined using an improved confocal spot detection system. Muscle fibers were loaded with the low affinity fluorescent Ca2+ indicator OGB-5N and localized action potential-induced fluorescence signals were recorded from consecutive locations separated by 200 nm within a single sarcomere. Three-dimensional reconstructions on the Ca2+ transients illustrate the existence of domains of increased fluorescence around Ca2+ release sites in the neighborhood of the T-tubules. We estimated the dimensions of these domains by drawing isochronal curves ((delta) F/F vs. spot position) and fitting Gaussian profiles to them. It was found that the earliest detectable full-width-at-half- maximum of these profiles was 0.77 +/- 0.25 micrometers and increased rapidly with time to 1.4 +/- 0.2 micrometers at their peak (18 degree(s)C). A brief, but statistically significant delay of 0.8 +/- 0.42ms was observed between the onset of the fluorescent transients at the Z- and M-lines. Our results are compatible with the possibility that, in response to AP stimulation, Ca2+ is not released exclusively from the junctional region of the sarcoplasmic reticulum, but from a broader expanse of the triadic region.

  2. The Fingerprint of a Galactic Nucleus

    NASA Astrophysics Data System (ADS)

    Nogueras-Lara, Francisco; Schödel, Rainer

    2017-01-01

    Because of the unique observational challenges -extreme crowding and extinction- any existing large-scale near-infrared (NIR) imaging data on the Galactic Center (GC) are limited by either one, or a combination, of the following: saturation, lack of sensitivity, too low angular resolution, or lack of multi-wavelength coverage. To overcome this situation, we are currently carrying out a sensitive, 0.2'' resolution JHK imaging survey of the Galactic Centre with HAWK-I/VLT. Thanks to holographic imaging, we achieve a similar resolution than with HST/WFC, but can cover also the long NIR, beyond 2 micrometers, which is essential to deal with extinction. Our survey is supported by an ESO Large Programme and will provide photometrically accurate (few percent uncertainty for H < 18 stars), high-angular resolution, NIR data for an area of several 1000 pc2, a more than ten-fold increase compared to the current state of affairs. Here we present an overview and first results.

  3. Airborne Turbulence Detection and Warning ACLAIM Flight Test Results

    NASA Technical Reports Server (NTRS)

    Hannon, Stephen M.; Bagley, Hal R.; Soreide, Dave C.; Bowdle, David A.; Bogue, Rodney K.; Ehernberger, L. Jack

    1999-01-01

    The Airborne Coherent Lidar for Advanced Inflight Measurements (ACLAIM) is a NASA/Dryden-lead program to develop and demonstrate a 2 micrometers pulsed Doppler lidar for airborne look-ahead turbulence detection and warning. Advanced warning of approaching turbulence can significantly reduce injuries to passengers and crew aboard commercial airliners. The ACLAIM instrument is a key asset to the ongoing Turbulence component of NASA's Aviation Safety Program, aimed at reducing the accident rate aboard commercial airliners by a factor of five over the next ten years and by a factor of ten over the next twenty years. As well, the advanced turbulence warning capability can prevent "unstarts" in the inlet of supersonic aircraft engines by alerting the flight control computer which then adjusts the engine to operate in a less fuel efficient, and more turbulence tolerant, mode. Initial flight tests of the ACLAIM were completed in March and April of 1998. This paper and presentation gives results from these initial flights, with validated demonstration of Doppler lidar wind turbulence detection several kilometers ahead of the aircraft.

  4. Calcium effects on stomatal movement in Commelina communis L

    SciTech Connect

    Schwartz, A.; Ilan, N.; Grantz, D.A. )

    1988-07-01

    Stomatal movements depends on both ion influx and efflux: attainment of steady state apertures reflects modulation of either or both processes. The role of Ca{sup 2+} in those two processes was investigated in isolated epidermal strips of Commelina communis, using the Ca{sup 2+} chelator EGTA to reduce apoplastic (Ca{sup 2+}). The results suggest that a certain concentration of Ca{sup 2+} is an absolute requirement for salt efflux and stomatal closure. EGTA (2 millimolar) increased KCl-dependent stomatal opening in darkness and completely inhibited the dark-induced closure of initially open stomata. Closure was inhibited even in a KCl-free medium. Thus, maintenance of stomata in the open state does not necessarily depend on continued K{sup +} influx but on the inhibition of salt efflux. Opening in the dark was stimulated by IAA in a concentration-dependent manner, up to 15.4 micrometer without reaching saturation, while the response to EGTA leveled off at 9.2 micrometer. IAA did not inhibit stomatal closure to the extent it stimulated opening. The response to IAA is thus consistent with a primary stimulation of opening, while EGTA can be considered a specific inhibitor of stomatal closing since it inhibits closure to a much larger degree than it stimulates opening. CO{sub 2} causes concentration-dependent reduction in the steady state stomatal aperture. EGTA completely reversed CO{sub 2}-induced closing of open stomata but only partially prevented the inhibition of opening.

  5. An inversion in the atmosphere of Titan. [caused by solar radiation absorption

    NASA Technical Reports Server (NTRS)

    Danielson, R. E.; Caldwell, J. J.; Larach, D. R.

    1974-01-01

    A very detailed greenhouse model derives a methane to hydrogen ratio of unity and a minimum surface pressure of 0.4 atm. Based on a surface gravity g = 140 cm sec/2, the minimum CH4 abundance is 30-40 km-A and the minimum H2 abundance varies from 15 to 85 km-A. A model of the atmosphere of Titan is proposed which seems to be consistent with observations and requires a much smaller CH4 abundance (of the order or 2 km-atm). Although no H2 is required, the presence of some H2 is readily accommodated. In this model, a temperature inversion exists in the atmosphere due to absorption of blue and ultraviolet solar radiation by small particles. The absorbed radiation is re-radiated by the dust and by molecules having long wavelength bands such as CH4 7.7 micrometer and ethane at 12.2 micrometer. The brightness temperature at 20 micrometer is primarily due to re-radiation by the dust.

  6. Green evolution and dynamic adaptations revealed by genomes of the marine picoeukaryotes Micromonas

    SciTech Connect

    Worden, Alexandra Z.; Lee, Jae-Hyeok; Mock, Thomas; Rouze, Pierre; Simmons, Melinda P.; Aerts, Andrea L.; Allen, Andrew E.; Cuvelier, Marie L.; Derelle, Evelyne; Everett, Meredieht V.; Foulon, Elodie; Grimwood, Jane; Gundlach, Heidrun; Henrissat, Bernard; Napoli, Carolyn; McDonald, Sarah M.; Parker, Micaela S.; Rombauts, Stephane; Salamov, Asaf; von Dassow, Peter; Badger, Jonathan G,; Coutinho, Pedro M.; Demir, Elif; Dubchak, Inna; Gentemann, Chelle; Eikrem, Wenche; Gready, Jill E.; John, Uwe; Lanier, William; Lindquist, Erika A.; Lucas, Susan; Mayer, Kluas F. X.; Moreau, Herve; Not, Fabrice; Otillar, Robert; Panaud, Olivier; Pangilinan, Jasmyn; Paulsen, Ian; Piegu, Benoit; Poliakov, Aaron; Robbens, Steven; Schmutz, Jeremy; Roulza, Eve; Wyss, Tania; Zelensky, Alexander; Zhou, Kemin; Armbrust, E. Virginia; Bhattacharya, Debashish; Goodenough, Ursula W.; Van de Peer, Yves; Grigoriev, Igor V.

    2009-10-14

    Picoeukaryotes are a taxonomically diverse group of organisms less than 2 micrometers in diameter. Photosynthetic marine picoeukaryotes in the genus Micromonas thrive in ecosystems ranging from tropical to polar and could serve as sentinel organisms for biogeochemical fluxes of modern oceans during climate change. These broadly distributed primary producers belong to an anciently diverged sister clade to land plants. Although Micromonas isolates have high 18S ribosomal RNA gene identity, we found that genomes from two isolates shared only 90percent of their predicted genes. Their independent evolutionary paths were emphasized by distinct riboswitch arrangements as well as the discovery of intronic repeat elements in one isolate, and in metagenomic data, but not in other genomes. Divergence appears to have been facilitated by selection and acquisition processes that actively shape the repertoire of genes that are mutually exclusive between the two isolates differently than the core genes. Analyses of the Micromonas genomes offer valuable insights into ecological differentiation and the dynamic nature of early plant evolution.

  7. Fabrication process of superconducting integrated circuits with submicron Nb/AlOx/Nb junctions using electron-beam direct writing technique

    NASA Astrophysics Data System (ADS)

    Aoyagi, Masahiro; Nakagawa, Hiroshi

    1997-07-01

    For enhancing operating speed of a superconducting integrated circuit (IC), the device size must be reduced into the submicron level. For this purpose, we have introduced electron beam (EB) direct writing technique into the fabrication process of a Nb/AlOx/Nb Josephson IC. A two-layer (PMMA/(alpha) M-CMS) resist method called the portable conformable mask (PCM) method was utilized for having a high aspect ratio. The electron cyclotron resonance (ECR) plasma etching technique was utilized. We have fabricated micron or submicron-size Nb/AlOx/Nb Josephson junctions, where the size of the junction was varied from 2 micrometer to 0.5 micrometer at 0.1 micrometer intervals. These junctions were designed for evaluating the spread of the junction critical current. We achieved minimum-to-maximum Ic spread of plus or minus 13% for 0.81-micrometer-square (plus or minus 16% for 0.67-micrometer-square) 100 junctions spreading in 130- micrometer-square area. The size deviation of 0.05 micrometer was estimated from the spread values. We have successfully demonstrated a small-scale logic IC with 0.9-micrometer-square junctions having a 50 4JL OR-gate chain, where 4JL means four junctions logic family. The circuit was designed for measuring the gate delay. We obtained a preliminary result of the OR- gate logic delay, where the minimum delay was 8.6 ps/gate.

  8. Effects of sulfur oxide pollutants on respiratory function, particle deposition and bronchial clearance. Final report

    SciTech Connect

    Lippmann, M.

    1980-11-01

    The effects of sulfur oxide pollutants on respiratory function, particle deposition, and bronchial clearance were explored in a series of three studies, two on donkeys and one on humans. In the first study, the effects of one-hour inhalation exposures to 0.3 - 0.6 micrograms H/sub 2/SO/sub 4/ and (NH/sub 4/)/sub 2/SO/sub 4/ aerosols in the donkey were studied in terms of alterations in pulmonary flow resistance and dynamic compliance, and changes in the regional deposition and tracheobronchial mucociliary clearance of an inert test aerosol. In the second study, the effect of chronic inhalation exposures to sulfuric acid mist upon mucociliary clearance from the lungs was studied, using the donkey as an analogue for man. Four animals were exposed one hour per day, five days per week, for six months; two to a concentration of 102 micrograms/cu m, the other to 106 micrograms/cu m. In the final study, the mucociliary particle clearance and respiratory mechanics of twelve healty nonsmokers exposed to 1/2 micrometer H/sub 2/SO/sub 4/ at 0 (control), 100, 300, and 1,000 micrograms/cu m for one hour per day for four days were examined.

  9. MODIS Solar Reflective Calibration Traceability

    NASA Technical Reports Server (NTRS)

    Xiong, Xiaoxiong; Butler, Jim

    2009-01-01

    Long-term climate data records often consist of observations made by multiple sensors. It is, therefore, extremely important to have instrument overlap, to be able to track instrument stability, to quantify, measurement uncertainties, and to establish absolute scale traceable to the International System of Units (SI). The Moderate Resolution Imaging Spectroradiometer (MODIS) is a key instrument for both the Terra and Aqua missions, which were launched in December 1999 and May 2002, respectively. It has 20 reflective solar bands (RSB) with wavelengths from 0.41 to 2.2 micrometers and observes the Earth at three nadir spatial resolutions: 0.25km, 0.5km, and 1km. MODIS RSB on-orbit calibration is reflectance based with reference to the bidirectional reflectance factor (BRF) of its on-board solar diffuser (SD). The SD BRF characterization was made pre-launch by the instrument vendor using reference samples traceable directly to the National Institute of Standards and Technology (NIST). On-orbit SD reflectance degradation is tracked by an on-board solar diffuser monitor (SDSM). This paper provides details of this calibration chain, from prelaunch to on-orbit operation, and associated uncertainty assessments. Using MODIS as an example, this paper also discusses challenges and key design requirements for future missions developed for accurate climate studies.

  10. Infrared techniques for detecting carbonization at onset of device failure

    NASA Astrophysics Data System (ADS)

    Farr, Norman; Sinofsky, Edward L.

    1997-05-01

    We describe the design, and development of an infrared detection system which detects the onset of carbonization of fluoropolymers in the presence of up to 60 watts of 1.06 micrometer laser energy. This system is used to shut down a therapeutic laser system before significant damage is done to a laser delivery device and patient. Black body radiation emitting from the diffusion tip is transmitted, backwards, through the same optical fiber as the therapeutic wavelength. Using a high power 1.06 micrometer laser mirror at 45 degrees, most of the 1.06 micrometer light is reflected while the black body radiation is passed to a holographic notch filter which further filters the signal. Still more filtering was needed before the 1.1 to 2 micrometer signal could be detected within the presence the therapeutic light using an extended indium gallium arsenide photodetector. There was still a significant detected offset which increased with laser power which necessitated a means to automatically null the offset for different laser power settings. The system is designed to be used with any unmodified laser system. It interfaces directly to or in series with most common external safety interlocks and can be used with various diffusing tips, probes or bare fibers.

  11. Long-wavelength-range laser diode using GaInNAs

    NASA Astrophysics Data System (ADS)

    Kondow, Masahiko; Nakatsuka, Shin'ichi; Kitatani, Takeshi; Yazawa, Yoshiaki; Okai, Makoto O.

    1997-05-01

    We propose a novel material: GaInNAs. It can be formed on a GaAs substrate, and has a bandgap energy suitable for long- wavelength-range laser diodes. The band lineup is ideal for preventing electron overflow. Therefore, applying GaInNAs to long-wavelength-range laser diodes is expected to result in excellent high-temperature performance. We have succeeded in demonstrating continuous-wave operation of GaInNAs/GaAs single quantum well laser diodes at room temperature. The threshold current density was about 1.4 kA/cm2. The lasing wavelength was about 1.2 micrometers . We have measured some characteristic parameters of the GaInNAs laser diode under pulsed operation. A high characteristic temperature (T0) of 127 K and a small wavelength shift per ambient temperature change of 0.48 nm/ degree(s)C were obtained. The experimental results indicate the applicability of GaInNAs to long-wavelength-range laser diodes with excellent high- temperature performance.

  12. Cosmic Ray Energy Determination by the Reduced-Opening Angle Method

    NASA Technical Reports Server (NTRS)

    Gregory, John C.

    1998-01-01

    The reduced opening angle technique offers a simple way with minimal model dependence to measure cosmic ray energies over a broad range with out any normalization uncertainties. The emulsion film and CR39 detectors proposed are well established techniques and should perform adequately. The analysis method depends on accurate automatic scanning of the CR39 plates. UAH have developed such a capability. With the proposed geometry energy measurements to approx. 5 TeV/a can be made. The expected iron event rate (E greater than or equal to 500 GeV/a) is 10/sq m day. The expected energy resolution, from accelerator calibrations at 200 GeV/a, is -50% to +80%. Since the absolute flux has some sensitivity to the assumed power law index it is essential that good energy resolution is obtained. The expected charge resolution is approx. 0.3 charge units for the CNO group falling to approx. 1 charge unit for the iron group. A suitable event trigger would be a measurable (greater than 2 micrometer) deflected heavy (Z greater than 2) fragment. One potential background is electromagnetic dissociation that predominantly couples to individual protons or alphas. Although the cross- sections can be appreciable such events will not pass the event trigger.

  13. Differential Absorption Measurements of Atmospheric Water Vapor with a Coherent Lidar at 2050.532 nm

    NASA Technical Reports Server (NTRS)

    Koch, Grady J.; Dharamsi, Amin; Davis, Richard E.; Petros, Mulugeta; McCarthy, John C.

    1999-01-01

    Wind and water vapor are two major factors driving the Earth's atmospheric circulation, and direct measurement of these factors is needed for better understanding of basic atmospheric science, weather forecasting, and climate studies. Coherent lidar has proved to be a valuable tool for Doppler profiling of wind fields, and differential absorption lidar (DIAL) has shown its effectiveness in profiling water vapor. These two lidar techniques are generally considered distinctly different, but this paper explores an experimental combination of the Doppler and DIAL techniques for measuring both wind and water vapor with an eye-safe wavelength based on a solid-state laser material. Researchers have analyzed and demonstrated coherent DIAL water vapor measurements at 10 micrometers wavelength based on CO2 lasers. The hope of the research presented here is that the 2 gm wavelength in a holmium or thulium-based laser may offer smaller packaging and more rugged operation that the CO2-based approach. Researchers have extensively modeled 2 um coherent lasers for water vapor profiling, but no published demonstration is known. Studies have also been made, and results published on the Doppler portion, of a Nd:YAG-based coherent DIAL operating at 1.12 micrometers. Eye-safety of the 1.12 micrometer wavelength may be a concern, whereas the longer 2 micrometer and 10 micrometer systems allow a high level of eyesafety.

  14. Laboratory evaluation of colloidal actinide transport at the Waste Isolation Pilot Plant (WIPP): 1. crushed-dolomite column flow...

    SciTech Connect

    Yelton, W.G.; Behl, Y.K.; Kelly, J.W.; Dunn, M.; Gillow, J.B.; Francis, A.J.; Papenguth, H.W.

    1996-12-31

    Colloid-facilitated transport of Pu, Am, U, Th, and Np has been recognized as a potentially important phenomenon affecting the performance of the Waste Isolation Pilot Plant (WIPP) facility being developed for safe disposal of transuranic radioactive waste. In a human intrusion scenario, actinide-bearing colloidal particles may be released from the repository and be transported by brines (approximately 0.8 to 3 molal ionic strength) through the Culebra, a thin fractured microcrystalline (mean grain size 2 micrometers) dolomite aquifer overlying the repository. Transport experiments were conducted using sieved, uniformly packed crushed Culebra rock or nonporous dolomite cleavage rhombohedra. Experiments with mineral fragments and fixed and live WIPP-relevant bacteria cultures showed significant levels of retardation due to physical filtration effects. Humic substances were not attenuated by the Culebra dolomite. Comparison of elution curves of latex microspheres in columns prepared with microcrystalline rock and nonporous rock showed minimal effect of Culebra micropores on colloid transport. These data form part of the basis to parameterize numerical codes being used to evaluate the performance of the WIPP.

  15. The bacterial gliding machinery

    NASA Astrophysics Data System (ADS)

    Shrivastava, Abhishek

    Cells of Flavobacterium johnsoniae, a rod-shaped bacterium, glide over surfaces with speeds reaching up to 2 micrometer's. Gliding is powered by a protonmotive force. The adhesin SprB forms filaments about 160 nm long that move on the cell-surface along a looped track. Interaction of SprB filaments with a surface produces gliding. We tethered F. johnsoniae cells to glass by adding anti-SprB antibody. Tethered cells spun about fixed points, rotating at speeds of about 1 Hz. The torques required to sustain such speeds were large, comparable to those generated by the flagellar rotary motor. Using a flow cell apparatus, we changed load on the gliding motor by adding the viscous agent Ficoll to tethered cells. We found that a gliding motor runs at constant speed rather than constant torque. We attached gold nanoparticles to the SprB filament and tracked its motion. We fluorescently tagged a bacterial Type IX secretion system (T9SS) protein and imaged its dynamics. Fluorescently tagged T9SS protein localized near the point of tether, indicating that T9SS localizes with the gliding motor. Based on our results, we propose a model to explain bacterial gliding.

  16. Spectral signatures of polar stratospheric clouds and sulfate aerosol

    NASA Technical Reports Server (NTRS)

    Massie, S. T.; Bailey, P. L.; Gille, J. C.; Lee, E. C.; Mergenthaler, J. L.; Roche, A. E.; Kumer, J. B.; Fishbein, E. F.; Waters, J. W.; Lahoz, W. A.

    1994-01-01

    Multiwavelength observations of Antarctic and midlatitude aerosol by the Cryogenic Limb Array Etalon Spectrometer (CLAES) experiment on the Upper Atmosphere Research Satellite (UARS) are used to demonstrate a technique that identifies the location of polar stratospheric clouds. The technique discussed uses the normalized area of the triangle formed by the aerosol extinctions at 925, 1257, and 1605/cm (10.8, 8.0, and 6.2 micrometers) to derive a spectral aerosol measure M of the aerosol spectrum. Mie calculations for spherical particles and T-matrix calculations for spheriodal particles are used to generate theoretical spectral extinction curves for sulfate and polar stratospheric cloud particles. The values of the spectral aerosol measure M for the sulfate and polar stratospheric cloud particles are shown to be different. Aerosol extinction data, corresponding to temperatures between 180 and 220 K at a pressure of 46 hPa (near 21-km altitude) for 18 August 1992, are used to demonstrate the technique. Thermodynamic calculations, based upon frost-point calculations and laboratory phase-equilibrium studies of nitric acid trihydrate, are used to predict the location of nitric acid trihydrate cloud particles.

  17. Feasibility model of a high reliability five-year tape transport, volume 2

    NASA Technical Reports Server (NTRS)

    Eshleman, R. L.; Meyers, A. P.; Davidson, W. A.; Gortowski, R. C.; Anderson, M. E.

    1973-01-01

    Analysis of the design features of the modularized tape transport renders a life expectancy in excess of five years. Tests performed on the tape transport were directed toward determining its performance capability. These tests revealed that the tape jitter and skew are in the range achieved by high quality digital tape transports. Guidance of the tape in the lateral sense by the use of the two hybrid crowned rollers proved to be excellent. Tracking was maintained within less than one thousandth inch (approximately 2 micrometers). The guidance capability demonstrated makes possible the achievement of the performance objective of 7.2 x 10 to the 9th power storage capability employing 1500 ft. of one inch wide tape with a packing density of 5,000 bits per inch per track on 80 tracks. Also, the machine showed excellent characteristics operating over a wide range of tape speeds. The basic design concept lends itself to growth and adaptation to a wide range of recorder requirements.

  18. The Vector Vortex Coronagraph: Sensitivity to Low-Order Aberrations, Central Obscuration, Chromaticism, and Polarization

    NASA Technical Reports Server (NTRS)

    Mawet, Dimitri; Pueyo, Laurent; Moody, Dwight; Krist, John; Serabyn, Eugene

    2010-01-01

    The Vector Vortex Coronagraph is a phase-based coronagraph, one of the most efficient in terms of inner working angle, throughput, discovery space, contrast, and simplicity. Using liquid-crystal polymer technology, this new coronagraph has recently been the subject of lab demonstrations in the near-infrared, visible and was also used on sky at the Palomar observatory in the H and K bands (1.65 and 2.2 micrometers, respectively) to image the brown dwarf companion to HR 7672, and the three extasolar planets around HR 8799. However, despite these recent successes, the Vector Vortex Coronagraph is, as are most coronagraphs, sensitive to the central obscuration and secondary support structures, low-order aberrations (tip-tilt, focus, etc), bandwidth (chromaticism), and polarization when image-plane wavefront sensing is performed. Here, we consider in detail these sensitivities as a function of the topological charge of the vortex and design properties inherent to the manufacturing technology, and show that in practice all of them can be mitigated to meet specific needs.

  19. Clay Bearing Units in the Region around Mawrth Vallis: Stratigraphy, Extent, and Possible Alteration Fronts

    NASA Technical Reports Server (NTRS)

    Dobrea, E. Z. Noe; Bishop, J. L.; McKeown, N. K.; Swayze, G.; Michalski, J. R.; Poulet, F.; Bibring, J.-P.; Mustard, J. F.; Ehlmann, B. L.; Arvidson, R.; Morris, R. B.; Murchie, S.; McEwen, A. S.; Malaret, E.; Hash, C.

    2007-01-01

    The largest exposure of phyllosilicates on Mars occurs on the highland plains around Mawrth Vallis. This exposure extends for about 300 km southward from the edge of the dichotomy boundary, covering an area greater than 200 x 300 kilometers over an elevation range of approximately 2000 meters. At least two different types of hydrated phyllosilicates (Fe/Mg-rich and Al-rich phyllosilicates) have been identified in OMEGA data based on absorption bands near 2.3 and 2.2 micrometers, respectively. These clay-bearing units are associated with layered, indurated light-toned units with complex spatial and stratigraphic relationships, and are unconfomably overlain by a darker, indurated, more heavily cratered unit. Ongoing analysis of OMEGA (approximately 1 kilometer/pixel) and CRISM multi-spectral (MSP, 200 meters/pixel) data reveal hydrated minerals with absorptions at approximately 2.2 or 2.3 micrometers in locations up to 300 kilometers away from the borders of the previously identified extent of clay-bearing units. We seek to: 1) further constrain the mineralogy of the hydrated species identified in [5], and 2) understand spatial and stratigraphic relationships between the different hydrated minerals and the cratered plains units in which they are found. In this work we perform mineralogical and stratigraphic comparisons between units to test whether these extended units may be related, in order to establish a broad zone of alteration.

  20. Laboratory measurements of selected optical, physical, chemical, and remote-sensing properties of five water mixtures containing Calvert clay and a nonfluorescing dye

    NASA Technical Reports Server (NTRS)

    Usry, J. W.; Whitlock, C. H.; Poole, L. R.; Witte, W. G., Jr.

    1981-01-01

    Total suspended solids concentrations ranged from 6.1 ppm to 24.3 ppm and sizes ranged between 1.5 micrometers and 10 micrometers with the most frequently occurring size less than 2 micrometers. Iron concentration was less than 1 percent of the total suspended solids. Nonfluorescing dye concentrations of the two mixtures were 20 ppm and 40 ppm. Attenuation coefficient for the five mixtures ranged from 4.8/m to 21.3/m. Variations in volume scattering function with phase angle were typical. Variations in attenuation and absorption coefficient with wavelength were similar for the mixtures without the dye. Attenuation coefficient of the mixtures with the dye increased for wavelengths less than 600 nm due to the dye's strong absorption peak near 500 nm. Reflectance increased as the concentration of Calvert clay increased and peaked near 600 nm. The nonfluorescent dye decreased the magnitude of the peak, but had practically no effect on the variation for wavelengths greater than 640 nm. At wavelengths less than 600 nm, the spectral variations of the mixtures with the dye were significantly different from those mixtures without the dye.