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Objective. To gain a better understanding of how low-income fathers of young children think about their role as fathers, we conducted a qualitative inquiry into the beliefs of fathers of 24-month-old children about what 'good fatherhood' means to them. Design. The 575 open-ended interviews, collected in 14 Early Head Start Fathers of Toddlers Qualitative Interview Substudy sites around the United States were analyzed using NUD*IST qualitative software to code and categorize the various roles fathers identified as important to them and their children. Results. Four broad types of roles were identified: (1) providing a stable environment (e.g., providing a living, 'being there' emotionally and physically), (2) teaching (e.g., giving guidance, exposing their child to the world), (3) physical interaction (e.g., play, caregiving), and (4) emotional support (e.g., providing love, building self-esteem). Conclusion. The beliefs of these men are considered in the context of historical perceptions of fatherhood, as well as their implications for generative theories of fatherhood. Overall, fathers articulated a strong sense of commitment and intentionality in their plans for interactions with their children. Our findings provide opportunities for service providers and policymakers to develop positive strategies to ensure fathers' ability to carry out their intentions. [ABSTRACT FROM AUTHOR]

In this introductory article to the Special Issue, we provide an overview of the research and policy context for the Early Head Start Father Studies. We describe the methods used to conduct the father studies, which began in 1997 and were designed to complement the Early Head Start Research and Evaluation Project, a random assignment evaluation of 3,001 families - half who received Early Head Start services and half who did not. The Early Head Start Father Studies included in the Special Issue addressed 5 key research questions about low-income fathers and their children (all under 3 years old) using a variety of data collection approaches, including mother report, father report, father - child videotaped interactions, and Early Head Start program staff report. Here we describe the father studies' methods and response rates, father demographics, and father - child relationship status. [ABSTRACT FROM AUTHOR]

The voltage–power characteristics and spatial structure of an RF discharge in the mixtures of CO[sub 2] and N[sub 2] molecular gases with He at total pressures of tens of torr are studied. One-dimensional numerical simulations of an RF discharge are carried out within two approaches: (i) the distribution function and the related kinetic coefficients are assumed to be functions of the local reduced field, and (ii) the kinetic coefficients are functions of the electron mean energy, which is calculated with allowance for both electron heat conduction and diffusion. The latter approach is shown to better describe the existing experimental dependence of the discharge voltage and the phase shift between the discharge current and voltage on the driving power. © 2002 MAIK “Nauka / Interperiodica”. [ABSTRACT FROM AUTHOR]

Examines operant conditioning and memory retrieval in six-month old infants using a memory reactivation paradigm. Subjects; Procedure; Results; Explanation of reactivation paradigm; More.

We present detailed measurements on the x-ray preionization electron density in a discharge chamber filled with different gases relevant to discharge pumped high-pressure excimer lasers. By comparing experimental results with the theoretical electron densities, we conclude that the observed preionization is inconsistent with the standard picture of direct ionization through x-ray absorption in the gas. We conclude that depending on the gas pressure, type of gas, and the gap length between the discharge electrodes used, x-ray preionization in excimer gases is, to a significant extent or even dominantly, based on a different mechanism. We identify that this mechanism is based on fast photoelectrons emitted by the cathode into the discharge chamber. [ABSTRACT FROM AUTHOR]

The discharge homogeneity in F2-based excimer laser gas mixtures and its dependence on various key parameters, such as the degree of preionization, preionization delay time, F2 concentration and current density, is investigated in a small x-ray preionized discharge chamber. The spatial and temporal evolution of the discharges is monitored by taking photographs of the discharge fluorescence with a fast intensified CCD camera. It is found that a preionization electron density of about 107 cm-3 bar-1 is sufficient to initiate a streamer-free homogeneous discharge in gas mixtures of helium and fluorine with multiatmospheric gas pressure. The accompanying optimum time delay between the application of the x-ray pulse and voltage across the discharge electrodes is determined to be about 20 ns. It is shown that in spite of these optimum initial conditions, a homogeneous glow discharge eventually transforms into an inhomogeneous discharge containing numerous filaments. Our experiments show that the higher the initial F2 concentration, the initial current density or the pump power density, the shorter the time interval over which the discharge stays homogeneous. By a quantitative characterization and defining a detailed measure of the observed discharge inhomogeneity we find that halogen depletion, as suggested from the theory, is responsible for the temporal instability of discharges in such laser gas mixtures, as the experimental results are in good agreement with the theory on the halogen depletion instability mechanism. [ABSTRACT FROM AUTHOR]

We report on the influence that waveguide-induced fluctuations in the phase velocity of the radiation wave have on the gain of Cherenkov-type free-electron lasers. We theoretically analyze low-gain Cherenkov free-electron lasers with a compact design that require resonator feedback for operation. We find that even small spatial variations of the waveguide parameters along the propagation direction can lead to significant degradation of the gain, and we present typical values for the required degree in waveguide precision that would eliminate such effects. [ABSTRACT FROM AUTHOR]

Spatial and temporal gain profiles as well as the peak net gain at 193 nm have been measured in X-ray preionized discharges excited by a single pulse electrical system working in the charge transfer mode. Ar- and F2-containing laser gas mixtures with He or Ne as a buffer gas have been used. With a pumping pulse duration of ∼ 100 ns (FWHM) and a specific peak power deposition of ∼ 1 MW cm-3 bar-1 in a gas mixture containing F2 : Ar : He (0.1%:5%:94.9%), at 2 bar total pressure, a very high peak net gain coefficient of ∼ 30% cm-1 was measured in the gas discharge. The FWHM of the gain waveform was ∼ 60 ns. [ABSTRACT FROM AUTHOR]

Abstract: The motion of a classical (harmonic) oscillator is studied in the case where the oscillator is driven by a pulsed oscillating force with a frequency varying in time (frequency chirp). The amplitude and phase of the oscillations left after the pulsed force in dependence on the profile and strength of chirp, frequency and duration of the force is investigated. [Copyright &y& Elsevier]

We determine the size of argon clusters generated with a planar nozzle, based on the optical measurements in conjunction with theoretical modelling. Using a quasi-one dimensional model for the moments of the cluster size distribution, we determine the influence of critical physical assumptions. These refer to the surface tension depending on the presence of thermal equilibrium, the mass density of clusters, and different methods to model the growth rate of the cluster radius. We show that, despite strong variation in the predicted cluster size, ⟨N⟩, the liquid mass ratio, g, can be determined with high trustworthiness, because g is predicted as being almost independent of the specific model assumptions. Exploiting this observation, we use the calculated value for g to retrieve the cluster size from optical measurements, i.e., calibrated Rayleigh scattering and interferometry. Based on the measurements of the cluster size vs. the nozzle stagnation pressure, we provide a new power law for the prediction of the cluster size in experiments with higher values of the Hagena parameter (Γ*>104). This range is of relevance for experiments on high-intensity laser matter interactions. [ABSTRACT FROM AUTHOR]

Abstract. We report on dye-laser-pumped, continuous-wave (CW) KTiOPO[sub 4] (KTP) optical parametric oscillators (OPOs) with pump and idler resonant cavities. With a linear two-mirror cavity the pump power at threshold was 70 mW. The single-frequency signal and idler output wavelengths were tuned in the range of 1025 to 1040nm and 1250 to 1380nm by tuning the dye laser in the range of 565 to 588nm. With a dual three-mirror cavity the threshold was 135 mW. Pumped by 500 mW of 578 nm radiation the 1040 nm single-frequency signal wave output power was 84 mW. Power and frequency stable operation with a spectral bandwidth of less than 9 MHz was obtained by piezo-electrically locking the length of the pump resonant cavity to the dye laser wavelength. Similar performance was achieved by placing the idler resonant OPO inside the resonator of the dye laser. With this system power stable and single-frequency operation was achieved with a spectral bandwidth of less than 11 MHz for the idler wave. [ABSTRACT FROM AUTHOR]

Abstract. We investigate the intensity noise spectra of a pump-enhanced continuous-wave (cw) optical parametric oscillator (OPO) as a function of the pump power. When the OPO is operating sufficiently high above threshold, the intensity noise spectra of the signal wave output exhibit a pronounced peak, that shifts to higher noise-frequencies in proportion to the fourth root of the above-threshold pump power. The width of the peak remains approximately constant. The observed shapes of the noise spectra and the measured dependence on the pump power are in good agreement with a theoretical model derived from the coupled field equations. The agreement shows that the intensity noise is caused by relaxation oscillations of the OPO which resonantly enhance the spectrally white intensity noise of the pump laser around the OPO's relaxation oscillation frequency. The pump laser is an A1GaAs diode laser master-oscillator power-amplifier (MOPA) system which delivers up to 250mW of single-frequency, 808-nm radiation in a near diffraction limited beam. The cavity of the ope consists of two mirrors to enhance the pump laser power and resonate the signal and idler waves. The triply resonant ope is based on non-critical type-II phasematching in RbTiOAsO[sub 4] (RTA), which provides a threshold pump power of 16mW. The maximum signal wave power is 23 mW at a wavelength of 1243 nm. The spectral bandwidth of the signal wave is less than 750 kHz. [ABSTRACT FROM AUTHOR]

Abstract. This paper reports on an experimental characterization and numerical analysis of the performance of a special AlGaAs master oscillator power amplifier (MOPA) system. This MOPA consists of a single stripe diode laser and a broad area double-pass amplifier. With an input of 76 mW, the amplifier generates 780 mW of 810 nm radiation in an almost diffraction limited beam (M[sup 2] = 1.1). The detailed experimental characterization includes the measurement of the output power as a function of the optical and electrical input power as well as the measurement of the dependence of the small signal gain, the saturation power and the power of the amplified spontaneous emission (ASE) on the amplifier current. The numerical analysis is based on a two-dimensional model which considers the spatial propagation and amplification of the input beam in the amplifier's active layer and the gain competition between ASE and the amplified input radiation. The numerical simulation provides values for parameters measured in the experiment (such as the saturation power or the small signal gain) and the power distribution in the amplifying layer. The good agreement between the experimental and numerical results indicates that the phenomenological, steady-state description of the amplification process should be well suited for a simple and rapid analysis of basic properties of high-power diode laser amplifiers. PACS: 42.55 Px; 42.60 Da; 42.60 Jf [ABSTRACT FROM AUTHOR]

Discharge instabilities in x-ray preionized F2-doped excimer laser gas mixtures are investigated using an intensified charge coupled device camera with a gating time of 300 ps. In contradiction with earlier theories and observations, it is found that the discharges in He/F2 mixtures are homogeneous only at very low concentration of F2 (0.025%). We present experimental results, which prove that in He/Kr/F2 mixtures the appearance of discharge filaments is coupled with the presence of F2 rather than Kr. [ABSTRACT FROM AUTHOR]

The net gain is measured for various pump power densities in a discharge-pumped long-pulse KrCl laser (222 nm). For this, a three-electrode laser system is employed, which is operated at high gas pressures of around 3.5 bar with pump power densities of 300-650 kW cm-3. The net gain reaches a maximum of 1.6% cm-1. Using the experimental results, values are calculated for the small-signal gain, the losses, and the saturation intensity. The losses and the saturation intensity are found to increase much stronger with the excitation rate than the small-signal gain. Fluorescence measurements at 222 nm show that the upper laser level depopulates faster when the power density increases. The influence of collisional quenching and the halogen consumption on the laser performance are discussed. [ABSTRACT FROM AUTHOR]

In this article we present a theoretical investigation on an experimental design of a laser wakefield accelerator in which electron bunches from a photocathode radio frequency linac are injected into a capillary discharge plasma channel just in front of a few tens of terawatt drive laser pulse. The electron bunch, with a kinetic energy of 2.9 MeV and an energy chirp imposed by the linac, is magnetically compressed by a factor of 8 to a duration of 250 fs, and is magnetically focused into the plasma channel where it matches the spot size of the drive laser (≈30 μm). The dynamics of the bunch, starting from the photocathode, through the linac, along the beam transportation line, through the magnetic compressor, and its focusing into the plasma channel are comprehensively simulated with the general particle tracer code. Further, we use our three-dimensional numerical codes to calculate the laser wakefield and to determine and optimize the trapping and acceleration of the injected bunch in the wakefield. We show that, injecting a 5 pC electron bunch of 250 fs duration, the experiment should deliver an electron bunch of approximately 744 MeV energy, with 1.1% relative energy spread, and with an extremely short duration (6 fs), after acceleration in a 5.4 cm long plasma channel. [ABSTRACT FROM AUTHOR]

Modeling free-electron laser (FEL) oscillators requires calculation of both the light-beam interaction within the undulator and the light propagation outside the undulator. We have developed a paraxial optical propagation code that can be combined with various existing models of gain media, for example, Genesis 1.3 for FELs, to model oscillators with full paraxial wave propagation within the resonator. A flexible scripting interface is used both to describe the optical resonator and to control the codes for propagation and amplification. To illustrate its capabilities, we numerically investigate two significantly different FEL oscillators: the free-electron laser for infrared experiments (FELIX) system and the vacuum-ultraviolet (VUV)-FEL oscillator of the proposed high-gain fourth generation light source. For the FELIX system, we find that diffraction losses are a considerable part of the single-pass cavity loss (at a wavelength of 40 μm). We also demonstrate that a resonator with hole coupling may be a viable alternative to a standard resonator with transmissive optics for the high gain VUV-FEL oscillator. [ABSTRACT FROM AUTHOR]

The influence of a plasma density gradient on ions accelerated along the specular (back reflection) direction in the transparent Target Normal Sheath Acceleration regime is investigated. Enhanced acceleration of ions is experimentally observed in this regime using high-intensity and ultra-high contrast laser pulses and extremely thin foils of few nanometer thicknesses. The experimental trend for the maximum proton energy appeared quite different from the already published numerical results in this regime where an infinitely steep plasma gradient was assumed. We showed that for a realistic modelling, a finite density gradient has to be taken into account. By means of particle-incell (PIC) simulations, we studied for the first time the influence of the plasma density scale length on ion acceleration from these nanofoil targets. Through a qualitative agreement between our numerical particle-in-cell simulations and our experiments, the main conclusion with regard to the experimental requirements is that, in the transparent regime evidenced with nanofoils as compared to the opaque regime, the plasma expansion has to be taken into account and both the pulse contrast and the damage threshold of the material are essential parameters. [ABSTRACT FROM AUTHOR]

fiber-amplified Distributed Bragg Reflector diode laser is used to pump a continuous wave, singly resonant Optical Parametric Oscillator (OPO). The output radiation covers the 3-4 μm with ability of rapid (100 THz/s) and broad mode-hop-free tuning (5 cm). Wavelength Modulation Spectroscopy is combined with the OPO to take optimal advantage of the spectral scan speed. The sensitivity of the system was determined as 0.8 ppbv (parts-per-billion by volume) for ethane (CH) for the absorption peak at 2996.9 cm recorded in 1.3 seconds, corresponding to a noise equivalent absorption sensitivity (NEAS) of 1.2×10 cm/Hz. A comparison between results using the 1, 2 and 4 harmonic derivative signal from wavelength modulation was performed. The broad continuous tunability was demonstrated by covering 35 cm while recording absorption features of ethane, methane and water. [ABSTRACT FROM AUTHOR]

The effect of addition of xenon on the long term homogeneity of discharges in F2and ArF excimer laser gas mixtures was investigated in a small-volume discharge chamber. The gas mixture in the discharge chamber was preionized by X-rays. A special electrical excitation circuit containing a pulse forming line provided a long, square-shaped current pumping pulse of a predetermined duration to the discharge electrodes. The initiation and the development of the discharge was monitored via its fluorescence signal with an intensified CCD camera. We found that adding Xe up to partial pressures of 0.53 mbar extended the homogeneous phase of the discharge from 80 ns to approximately 200 ns in He/F2as well as in He/Ar/F2and Ne/Ar/F2excimer laser gas mixtures. Monitoring of the ArF and XeF spontaneous emission signals showed that the formation of ArF excimers remained unaffected by the addition of xenon (up to 1.3 mbar) to the laser gas mixture. [ABSTRACT FROM AUTHOR]

A continuous wave optical parametric oscillator, generating up to 300 mW idler output in the 3–4 μm wavelength region, and pumped by a fiber-amplified DBR diode laser is used for trace gas detection by means of quartz-enhanced photoacoustic spectroscopy (QEPAS). Mode-hop-free tuning of the OPO output over 5.2 cm-1 and continuous spectral coverage exceeding 16.5 cm-1 were achieved via electronic pump source tuning alone. Online monitoring of the idler wavelength, with feedback to the DBR diode laser, provided an automated closed-loop control allowing arbitrary idler wavelength selection within the pump tuning range and locking of the idler wavelength with a stability of 1.7×10-3 cm-1 over at least 30 min. Using this approach, we locked the idler wavelength at an ethane absorption peak and obtained QEPAS data to verify the linear response of the QEPAS signal at different ethane concentrations (100 ppbv-20 ppmv) and different power levels. The detection limit for ethane was determined to be 13 ppbv (20 s averaging), corresponding to a normalized noise equivalent absorption coefficient of 4.4×10-7 cm-1 W/Hz1/2. [ABSTRACT FROM AUTHOR]

The article looks at methods used to enhance antibody yield, focusing on the optimal seeding concentrations of hybridomas. It is believed that laboratory techniques used to increase the yield of monoclonal antibodies (MAbs) can be applied to the production of antibodies on a larger scale. Human endogenous retrovirus antibody-producing cell lines used on laboratory mice are discussed.

External injection of an electron bunch in the laser wakefield can result in femtosecond accelerated bunches with relatively low energy spread. In this paper it is shown that the density transition from vacuum to plasma can play an important role in the trapping process. The plasma wavelength in this transition region changes continuously, which means that the injected electrons see an altering wakefield. This can result in strong defocusing of the injected bunch. It is found that the effect becomes stronger for stronger wakefields, longer transition lengths, and lower injection energies. The transition region can be avoided if the bunch is injected into the wakefield at an angle. Injecting the bunch at an angle allows the bunch to be wider and results in more charge being trapped. The dynamics of the bunch in this case are similar to the dynamics of a bunch injected in front of the laser pulse. [ABSTRACT FROM AUTHOR]

A proposal for a self-seeding, tunable free-electron laser amplifier operating in the vacuum ultra-violet (VUV) region of the spectrum is presented. Full three-dimensional (3D) modelling of the free electron laser and the optical feedback system has been carried out. Simulations demonstrate the generation of near transform limited radiation pulses with peak powers in the hundreds of megawatts. Preliminary 1D simulations show that by using a similar system it may be possible to extend such operation beyond the VUV to higher photon energies. [ABSTRACT FROM AUTHOR]

The discharge quality and optimum pump parameters of a long-pulse high-pressure gas discharge excited KrCl laser are investigated. A three-electrode prepulse–mainpulse excitation circuit is employed as pump source. The discharge volume contains a gas mixture of HCl/Kr/Ne operated at a total pressure of up to 5 bar. For a plane–plane resonator, the divergence of both output laser beams is measured. A low beam divergence of less than 1 mrad is measured as a result of the very high discharge homogeneity. A maximum laser pulse duration of 150 ns (FWHM) is achieved for a pump duration of 270 ns (FWHM) and a power density of 340 kW cm-3. Pumping the discharge under optimum conditions employing a stable resonator results in a maximum specific energy of 0.45 J/l with a laser pulse duration of 117 ns and an efficiency of 0.63% based on the deposited energy. [ABSTRACT FROM AUTHOR]

For the purpose of laser wakefield acceleration, it turns out that the injection of electron bunches longer than the plasma wavelength can also generate accelerated femtosecond bunches with a relatively low energy spread. This is of great interest because such injecting bunches can be provided, e.g., by photo cathode rf linacs. Here we show that when an e-bunch is injected into the wakefield, it is important to take into account the interaction of the injected bunch with the laser pulse in the vacuum region located in front of the plasma. We show that at low energies of the injected bunch, this leads to ponderomotive scattering of the bunch and results in a significant drop of the collection efficiency. For certain injection energies the ponderomotive scattering may result in a smaller energy spread in the accelerated bunch. It is found that the injection position in the laser wakefield plays an important role. Higher collection efficiency can be obtained for certain injection energies, when the bunch is injected in plasma at some distance from the laser pulse; the energy spread, however, is typically larger in this case. We also estimate the minimum trapping energy for the injected electrons and the length of the trapped bunch. [ABSTRACT FROM AUTHOR]

Abstract: We present a conceptual design of a laser wakefield acceleration experiment where a sub-picosecond electron bunch from a photo-cathode RF linac is injected into a plasma channel just before a laser pulse. The pulse overtakes the bunch which is then trapped, compressed and accelerated in the laser wakefield. This way ultra-relativistic bunches with a size of the order of a micron and relatively low energy spread can be generated. We show the results of our simulations and discuss the setup for a demonstration experiment. [Copyright &y& Elsevier]

We describe a continuous-wave master-oscillator power-amplifier system based on a distributed Bragg reflection diode laser and an Yb doped fiber amplifier. The observed optical spectrum of the amplified seed source can be tailored to arbitrary shapes and widths between 30 MHz and greater than 1 GHz by controlling the radio frequency modulation wave form of the injection current. [ABSTRACT FROM AUTHOR]

Objective. To gain a better understanding of how low-income fathers of young children think about their role as fathers, we conducted a qualitative inquiry into the beliefs of fathers of 24-month-old children about what 'good fatherhood' means to them. Design. The 575 open-ended interviews, collected in 14 Early Head Start Fathers of Toddlers Qualitative Interview Substudy sites around the United States were analyzed using NUD*IST qualitative software to code and categorize the various roles fathers identified as important to them and their children. Results. Four broad types of roles were identified: (1) providing a stable environment (e.g., providing a living, 'being there' emotionally and physically), (2) teaching (e.g., giving guidance, exposing their child to the world), (3) physical interaction (e.g., play, caregiving), and (4) emotional support (e.g., providing love, building self-esteem). Conclusion. The beliefs of these men are considered in the context of historical perceptions of fatherhood, as well as their implications for generative theories of fatherhood. Overall, fathers articulated a strong sense of commitment and intentionality in their plans for interactions with their children. Our findings provide opportunities for service providers and policymakers to develop positive strategies to ensure fathers' ability to carry out their intentions. [ABSTRACT FROM AUTHOR]

The effect of frequency variation (chirp) in an electromagnetic (EM) pulse on the pulse interaction with a charged particle and plasma is studied. Various types of chirp and pulse envelopes are considered. In vacuum, a charged particle receives a kick in the polarization direction after interaction with a chirped EM pulse. Interaction of a one-dimensional chirped pulse with uniform plasma is considered. We found that the amplitude of the wake wave generated in plasma by an EM pulse can be significantly higher when the pulse is chirped. [ABSTRACT FROM AUTHOR]

After the development of a novel XeCl excimer laser with a nearly diffraction-limited beam and 175 ns pulse length, research was done on different industrial applications of this laser. Hole drilling, one of these applications, was studied extensively. A better understanding of the drilling process is necessary to optimise the drilling efficiency and to control the quality of the holes. A shadowgraphic imaging technique was used for studying the removal of material from the hole and the absorption of the laser beam by this removed material. Images were made at successive times both during and after the laser pulse.In drilling of thin foils, it was shown that the material was ejected mainly after the laser pulse. A comparison of different materials showed that the drilling process should be optimised for each material independently. Furthermore, the plume was found to be not fully transparent for processing materials with a strong absorption line at or near the laser wavelength. The correlation between material and drilling speed suggests improved energy transfer and improved melt ejection for the materials with this absorption. [ABSTRACT FROM AUTHOR]

An approach to bolometry has been developed. It is based on the measurements of optical reflectivity change of a thin metal layer deposited on a transparent substrate. The reflectivity change results from the temperature rise due to absorption of energetic particles or x rays. The sensor of the bolometer has no ohmic contact with the measuring unit, making this method well suited for an environment with strong electromagnetic noise interference. The technique was applied to characterize a method for the generation of intense electron beams in a dense gas. Very high efficiency for the e-beam generation (up to 95%) was measured. [ABSTRACT FROM AUTHOR]

We theoretically and experimentally investigate wavelength tuning of synchronously pumped optical parametric oscillators (OPOs) on changing the cavity length or the pump-repetition rate. Conditions for rapid and wide-range wavelength access are derived. Using an OPO pumped directly by a mode-locked diode-laser master-oscillator power-amplifier (MOPA) system, an all-electronically controlled access to near- and mid-infrared wavelengths is demonstrated. The singly (signal) resonant OPO is based on periodically poled lithium niobate (PPLN) and emits 8 ps idler pulses at a repetition rate of 2.5 GHz in the wavelength range 1986 to 2348 nm (signal: 1530 to 1737 nm). Wavelength tuning over 114 nm (signal) and 189 nm (idler) is achieved solely by electronically varying the repetition rate of the diode-laser oscillator over 720 kHz. By controlling the repetition rate with a programmable driver, an arbitrary emission sequence of the OPO on two wavelength channels is generated, with access times as short as 10 μs. 11 OPO wavelengths equally spaced in the range 1627–1689 nm (signal) or 2054–2154 nm (idler) could be addressed. [ABSTRACT FROM AUTHOR]

An electron beam source based on a dielectric barrier discharge and a perforated anode working in a dense gas is described. Electron beams with current densities up to 60 A/cm[sup 2] and pulse durations of 150 ns were generated. Stable operation of the device at a repetition frequency of 200 Hz has been demonstrated. © 2003 American Institute of Physics. [ABSTRACT FROM AUTHOR]