A compact 100 kV high voltage glycol capacitor.

A high voltage capacitor is described in this paper. The capacitor uses glycerol as energy storage medium, has a large capacitance close to 1 nF, can hold off voltages of up to 100 kV for μs charging time. Allowing for low inductance, the capacitor electrode is designed as coaxial structure, which is different from the common structure of the ceramic capacitor.

Design of pulsed guiding magnetic field for high power microwave generators.

In this paper, we present a comprehensive study on designing solenoid together with the corresponding power supply system to excite pulsed magnetic field required for high power microwave generators. Particularly, a solenoid is designed and the excited magnetic field is applied to a Ku-band overmoded Cerenkov generator. It is found in experiment that the electron beam is properly guided by the magnetic field and a 1.

Slightly uneven electric field trigatron employed in tens of microseconds charging time.

To solve the issue of operation instability for the trigatron switch in the application of tens of microseconds or even less charging time, a novel trigatron spark gap with slightly uneven electric field was presented. Compared with the conventional trigatron, the novel trigatron was constructed with an obvious field enhancement on the edge of the opposite electrode. The selection of the field enhancement was analyzed based on the theory introduced by Martin.

Focusing electrode and coaxial reflector used for reducing the guiding magnetic field of the Ku-band foilless transit-time oscillator.

Based on the theoretical analysis of the intense relativistic electron beam propagation in the coaxial drift-tube, a focusing electrode and a coaxial reflector is proposed to lessen the demand of the coaxial Ku-band foilless transit-time oscillator (TTO) for the guiding magnetic field. Moreover, a Ku-band TTO with the focusing electrode and the coaxial reflector is designed and studied by particle in cell simulation. When the diode voltage is 390 kV, the beam current 7.

Alloying and oxidation of in situ produced core-shell Al@Yb nanoalloy particles--an "on-the-fly" study.

Core-shell-structured nanoalloy particles with an Al-dominated interior covered by few Yb monolayers have been fabricated using a vapor-aggregation method involving magnetron sputtering. The radially segregated structure of the Yb-Al nanoparticles has been disclosed by "on-the-fly" photoelectron spectroscopy monitoring of the nanoparticle beam in Yb 4f and Al 2p electron binding energy regions. Both, the binding energy values and the electron microscopy images taken on the deposited nanoparticles, allow estimating their dimensions to be in the 5-10 nm range.

Jitter characteristic of series magnetic pulse compressor employed in ns trigger generator.

The jitter characteristic of series magnetic pulse compressor (MPC) employed in ns trigger generator was explored. The time delay of the series MPC is the sum value of the compression time in each stage. The primary voltage disturbance is the original parameter to affect the timing stability of the system.

Influence of different illumination profiles on the on-state resistances of silicon carbide photoconductive semiconductor switches.

Characteristics of a silicon-carbide (SiC) photoconductive switch under different illumination profiles are presented. We triggered a V-doped semi-insulated 6H-SiC switch with lateral geometry using a laser beam of 532-nm wavelength. Photoconductivity tests for different spot profiles and locations show that such switches achieve a minimum on-state resistance when the switching gap is illuminated.

Synthesis and characterization of CuAlO(2) and AgAlO(2) delafossite oxides through low-temperature hydrothermal methods.

In this work, we present one-step low temperature hydrothermal synthesis of submicrometer particulate CuAlO2 and AgAlO2 delafossite oxides, which are two important p-type transparent conducting oxides. The synthesis parameters that affect the crystal formation processes and the product morphologies, including the selection of starting materials and their molar ratios, the pH value of precursors, the hydrothermal temperature, pressure, and reaction time, have been studied. CuAlO2 crystals have been synthesized from the starting materials of CuCl and NaAlO2 at 320-400 °C, and from Cu2O and Al2O3 at 340-400 °C, respectively.

Design and experiment of a cross-shaped mode converter for high-power microwave applications.

A compact mode converter, which is capable of converting a TM01 mode into a circularly polarized TE11 mode, was developed and experimentally studied with high-power microwaves. The converter, consisting of two turnstile junctions, is very short along the wave propagation direction, and therefore is suitable for designing compact and axially aligned high-power microwave radiation systems. In this paper, the principle of a converter working at 1.

A compact bipolar pulse-forming network-Marx generator based on pulse transformers.

A compact bipolar pulse-forming network (PFN)-Marx generator based on pulse transformers is presented in this paper. The high-voltage generator consisted of two sets of pulse transformers, 6 stages of PFNs with ceramic capacitors, a switch unit, and a matched load. The design is characterized by the bipolar pulse charging scheme and the compact structure of the PFN-Marx.

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

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.

Low-noise, single-frequency, single-polarization Brillouin/erbium fiber laser.

We demonstrate a low-noise Brillouin/erbium fiber laser (BEFL), which uses only 1.5 m polarization-maintaining erbium-doped fiber as both the Brillouin and erbium gain media. This BEFL presents a phase noise of -125 dB/Hz(1/2) at 1 kHz frequency, at 2 mW Brillouin pump (~3 MHz linewidth) power and 200 mW 980 nm pump power.

Tm-Ho co-doped all-fiber brand-range self-sweeping laser around 1.9 μm.

We present a brand-range self-sweeping Tm-Ho co-doped fiber laser experimentally. The laser's center wavelength sweeps periodically around 1.9 μm with self-sweeping range of 4 nm ~17 nm, and the sweep rate can be changed in the range of 0.

Analysis of a high power microwave radial line slot antenna.

A traditional radial line slot antenna (RLSA) is a high gain planar array. To improve the power handling capacity, we design a radial line slow wave structure which replaces a traditional dielectric sheet in the radial waveguide of the traditional RLSA. This high power microwave (HPM) RLSA is fed from a double-layered radial line waveguide to realize the directional radiation of the microwave.

Over an octave cascaded Raman scattering in short highly germanium-doped silica fiber.

In this paper, we report on cascaded Raman scattering (RS) in a highly germanium-doped silica fiber (HGDF) pumped by a picosecond pulsed master oscillator power amplifier (MOPA) system at 1064 nm in the normal dispersion regime. Benefited by the higher Raman gain of germanium (GeO2) than silica in the core, the length of the HGDF is only several meters. The broadest output spectrum comprises of 10 orders Raman stokes waves and eventually evolves into a supercontinuum (SC) spanning from 1000 to beyond 2100 nm with an output average power up to Watt scale.

Capacity of MIMO free space optical communications using multiple partially coherent beams propagation through non-Kolmogorov strong turbulence.

We study the average capacity performance for multiple-input multiple-output (MIMO) free-space optical (FSO) communication systems using multiple partially coherent beams propagating through non-Kolmogorov strong turbulence, assuming equal gain combining diversity configuration and the sum of multiple gamma-gamma random variables for multiple independent partially coherent beams. The closed-form expressions of scintillation and average capacity are derived and then used to analyze the dependence on the number of independent diversity branches, power law α, refractive-index structure parameter, propagation distance and spatial coherence length of source beams. Obtained results show that, the average capacity increases more significantly with the increase in the rank of MIMO channel matrix compared with the diversity order.

Spray deposition of water-soluble multiwall carbon nanotube and Cu2ZnSnSe4 nanoparticle composites as highly efficient counter electrodes in a quantum dot-sensitized solar cell system.

In this paper, low-cost counter electrodes (CEs) based on water-soluble multiwall carbon nanotube (MWCNT) and Cu2ZnSnSe4 nanoparticle (CZTSe NP) composites have been successfully introduced into a quantum dot-sensitized solar cell (QDSC) system. Suitable surface modification allows the MWCNTs and CZTSe NPs to be homogeneously dispersed in water, facilitating the subsequent low-temperature spray deposition of high quality composite films with different composite ratios. The electrochemical catalytic activity of the composite CEs has been critically compared by electrochemical impedance spectroscopy and Tafel-polarization analysis.

Enhanced performance of p-type dye-sensitized solar cells based on ultrasmall Mg-doped CuCrO2 nanocrystals.

Herein, we present ultrasmall delafossite-type Mg-doped CuCrO2 nanocrystals prepared by using hydrothermal synthesis and their first application as photocathodes in efficient p-type dye-sensitized solar cells. The short-circuit current density (Jsc ) is notably increased by approximately 27% owing to the decreased crystallite size and the enhanced optical transmittance associated with Mg doping of the CuCrO2 nanocrystalline sample. An open-circuit voltage (Voc ) of 201 mV, Jsc of 1.

A study on the fabrication of nanostructures with high aspect ratio and large area uniformity.

Nanoimprint lithography (NIL), as a promising next generation lithography method, has the advantages of high throughput, sub-10-nm feature and low cost. However, the requirements, such as the structure with high aspect ratio, large area uniformity, and pattern transfer on nonflat surface, have barely been satisfied at the same time. In this study, the authors present a novel fabrication process by introducing a three-mask-layer (TML) Soft UV NIL technique which proves to be a simple and effective method.

A high-impedance attenuator for measurement of high-voltage nanosecond-range pulses.

A novel kind of high-impedance cable attenuator for measurement of high-voltage ns-range pulses is investigated in this paper. The input and output ports of the proposed attenuator were both high-impedance ports, and good pulse response characteristics of the proposed attenuator were obtained with pulse response time less than 1 ns. According to the requirement of measurement, two attenuators with lengths at 14 m and 0.

Theoretical models for beam quality evaluation of fiber supercontinuum sources.

We propose three theoretical models to evaluate the beam quality of the fiber supercontinuum source as a whole. New definitions of spectral centroid and three factors to evaluate the beam quality of supercontinuum source are introduced. Based on the three factors some supercontinuum sources with different output power and spectra obtained from the experiment are calculated numerically.

Intense ultra-broadband down-conversion in co-doped oxide glass by multipolar interaction process.

We report that Eu(2+) can be an efficient sensitizer for Yb(3+) and a broadband absorber for blue solar spectra in the host of oxide glass. The greenish 4f → 5d transition of Eu(2+) and the characteristic near-infrared emission of Yb(3+) were observed, with the blue-light of xenon lamp excitation. The 5d energy can be adjusted by the host and the energy transfer efficiency can be enhanced.

Design and experiment of a directional coupler for X-band long pulse high power microwaves.

Higher power and longer pulse are the trend of the development of high power microwave (HPM), and then some problems emerge in measuring the power of HPM because rf breakdown is easier to occur under the circumstance of high power (the level of gigawatt) and long pulse (about 100 ns). In order to measure the power of the dominant TM₀₁ mode of an X-band long pulse overmoded HPM source, a directional coupler with stable coupling coefficient, high directivity, and high power handling capacity in wide band is investigated numerically and experimentally. At the central frequency 9.

Brillouin/Raman compensation of the Kerr-effect-induced bias in a nonlinear ring laser gyroscope.

In this Letter, the beat frequency at rest of a ring laser gyroscope with nonlinear effects is discussed in detail. Even without an additional intensity-stabilizing system, the random nullshift bias induced by the Kerr effect is compensated by the phase shift associated with the stimulated Brillouin/Raman scattering. And the nonlinear stimulated scattering also serves as the gain mechanism of the gyroscope.

Efficient generation of broad Raman sidebands in an index-guided photonic crystal fiber.

The efficient generation of broad Raman sidebands is experimentally demonstrated in a short piece of index-guided photonic crystal fiber, which is pumped by a high-peak-power pulse near the zero-dispersion wavelength and seeded by a continuous-wave Stokes signal centered at 1117 nm. The Raman sidebands generated via stimulated Raman scattering and cascaded four-wave mixing contain five Stokes and six anti-Stokes peaks and span from 827 to 1398 nm, and the 3 dB linewidth for each peak is smaller than 1 nm. However, the pure Raman sidebands are largely dependent on the pulse pump power as well as the fiber length.