Watts Of Output Power Research Articles

Proposing linear structure for annular thermoelectric generators; thermal, exergetic, mechanical, and economic analysis

Annular thermoelectric generators have been the subject of many studies in recent years due to their structure which improves the efficiency when recovering heat from round surfaces. A novel linear arrangement of legs is proposed in this paper which greatly increases the flexibility of design compared to the conventional π structure of annular thermoelectric generators. Every geometric feature of the legs in the linear annular thermoelectric generator can be changed and optimized independently. Numerical simulations are carried out to study the effect of various parameters such as height ratio (θh), total height (h), angle ratio (θφ), total angle (φ), thickness ratio (θt), total thickness (t), hot and cold side temperature on the output power, efficiency, mechanical and economic performance of the linear shape annular thermoelectric generator. Results indicated that the height ratio, angle ratio, and thickness ratio of 0.5 lead to the highest conversion and exergy efficiencies while producing the lowest thermal stress on the legs and having the least cost per watt of output power. Additionally, it is found that the increment of the total combined height, total angle, or total thickness of the thermoelectric legs increases the costs per watt of output power. For example, the dollar/watt value is grown by 7% when the total thickness is increased from 8 mm to 16 mm for an angle ratio of 0.5. The increase of the heat source temperature can boost the output power, and conversion efficiency, and lower the cost but also impose larger stress as well.

A triple resonance (e, 1H, 13C) probehead for liquid-state DNP experiments at 9.4 Tesla

In DNP experiments, NMR signal intensity is increased by transferring the much larger electron spin polarization to nuclear spins via microwave irradiation. Here we describe the design and performance of a probehead that makes it possible to perform Overhauser DNP experiments at 1H and 13C in liquid samples with a volume of up to 100 nl. We demonstrate on a 13C-labeled sodium pyruvate sample in water that proton decoupling under DNP conditions is possible with this new triple-resonance DNP probehead. In addition, the heat dissipation from the sample has been greatly improved with our new probe design. This makes it possible to keep liquid samples at a constant temperature under irradiation with a high-frequency 263 GHz microwave gyrotron with a few watts of output power. This improved performance opens up the possibility to disentangle the role of sample temperature and applied microwave power for DNP efficiency in liquids and to obtain a quantitative determination of EPR saturation by observing the suppression of paramagnetic shift as a function of microwave power.

Activated Carbon Based on Pineapple Crown for Heavy Metal Adsorption

The objectives of this study are to investigate the influence of concentration variation of potassium hydroxide (KOH) and to remove a heavy metal in liquid waste of the activated carbon. The raw material of activated carbon was obtained from pineapple crown waste. Pineapple crowns pre-carbonized at 180 oC for 1 hour. Chemical activation was carried out using KOH with concentration 2M, 3M, and 4M for 20 hours at 30 oC and temperature 60 oC for 2 hours. Microwave irradiation was conducted at 630 Watt of output power for 15 minutes. The physical properties of activated carbon were characterized using scanning electron microscopy to determine surface morphology of activated carbon, X-ray diffraction to calculated microstructure (i.e. interlayer spacing and microcrystalline dimension) using Bragg’s and Scherer’s equations, specific surface area was calculated from N2 adsorption-desorption isotherm using BET equation, Fourier-transform infrared (FTIR) identify the functional groups of activated carbon, and heavy metals absorption was tested using atomic adsorption spectrophotometric. The highest surface area of activated carbon is 300,901 m2/g for activated carbon with concentration 2M corresponding to the highest stack height (Lc) of activated carbon of 10,470 nm. The carbon chain structure shows the functional groups C-H, C≡C, O-H, C-OH, and CH2 at wavenumbers of 2889,49 cm-1, 2360,97 cm-1, 2339,97 cm-1, and 998,21 cm-1, respectively.

PENYERAPAN LOGAM BERAT Pb DAN Cu MENGGUNAKAN KARBON AKTIF BERBASIS MAHKOTA NANAS DENGAN VARIASI KONSENTRASI KALIUM HIDROKSIDA

This study aims to determine the influence of concentration of potassium hydroxide (KOH) on the adsorption of Pb2+ and Cu2+ metal ions in industrial used water. The activated carbon was prepared from pineapple crown waste. Pineapple crown was pre-carbonized at 180oC for 1 hours. Chemical activation was done using KOH with variations in concentrations of 2, 3, and 4 M. The samples were irradiated by using a microwave at 630 Watt of output power for 15 minutes. KOH activation and microwave irradiation power were influenced to the physical properties of the samples. Activated carbon obtained were characterized using SEM, EDX, FTIR and AAS. The results showed that highest adsorption were obtained from activated carbon that was activated by KOH 2 M. Adsorption efficiency for Pb2+ and Cu2+ metals were 81.15% and 49.71%, respectively. The carbon chain structure shows the functional groups C-H, C≡C, O-H, C=C at wavenumber 2889.49 cm-1, 2360.97 cm-1, 2339.97 cm-1.

2.4-GHz-Band High-Power and High-Efficiency Solid-State Injection-Locked Oscillator

There is increasing research interest in the development of solid-state devices to provide intelligent uniform heating, spot heating, and so on. However, the use of the solid-state devices to realize the same 1-kW output power as a conventional microwave oven requires configuration complexity that, for the moment, prevents its wider adoption. Although there is a demand for microwave generators with average output power of several tens to several hundreds of watts, existing solid-state solutions cannot produce this level of power. These problems prompted us to investigate, both by analysis and prototyping, small injection-locked oscillators that use high-efficiency microwave generators to provide several hundred watts of output power. Using an imbalanced coupling resonator in the feedback circuit, we were able to achieve an output power of 210 W and an efficiency of 51% at 2.45 GHz, when injecting a reference signal at a level of less than 1/10 000 of the output power. The high-power and high-efficiency solid-state injection-locked oscillators described in this paper have the advantages of long life, tunable frequency and phase, and low-voltage operation. These characteristics are potentially useful for realizing precise temperature control in chemical reactions, as well as spot and uniform heating by microwave ovens.

Design, Realization, and Evaluation of a Riemann Pump in GaN Technology

The realization of a novel Riemann Pump for radio frequency digital-to-analog converters (RF DACs) in combination with a power amplifier is presented, which improves the signal-to-noise ratio of conventional converter concepts. The presented concept results in an arbitrary waveform generator that at the same time is capable to provide several watts of output power at RF-frequencies to $50~\Omega $ . Furthermore, the gallium nitride (GaN) high-electron-mobility transistor technology provides high-switching frequencies to ensure an oversampling ratio of 5 for a wide baseband bandwidth. The Riemann Pump, which is controlled with a digital bit-stream, is based on the current-steering topology and provides the possibility to synthesize arbitrary waveforms. A 2-b RF DAC was designed with multiple GaN monolithic microwave-integrated circuits and proves the feasibility to generate arbitrary waveforms. Measurement results yield triangular signals with a baseband frequency of 100 MHz for an input-control data rate of 200 Mb/s.

Generation of 6.8 W of CW output power at 1550 nm using small mode field diameter Er:Yb co-doped double clad fiber in laser oscillator configuration

We report studies on erbium:ytterbium doped fiber laser, that uses a commercially available off-the-shelf Er:Yb co-doped single mode fiber with small mode field diameter of 7 µm, which is compatible with single mode fibers used in most of the communication systems. In a FBG based laser oscillator configuration pumped at 976 nm, the single transverse mode fiber laser emitted more than 6.87 Watts of output power at 1550 nm with a conversion efficiency of ~32% over a narrow line width. The pump radiation is coupled into active fiber using free-space optics. To the best of our knowledge, this is the highest power reported in the 1.55 µm region by using commercially available off-the-shelf active fiber of small mode field diameter (~7 µm) in a simple laser oscillator configuration with 9×× nm pumping. We also observed the effect of weak secondary grating structure in FBGs on the spectral characteristics of EYDFLs and explained its significance for co-doped fiber lasers such as erbium–ytterbium fiber lasers.

Theoretical and experimental analysis of high-power frequency-stabilized semiconductor master oscillator power-amplifier system.

We present a compact high-power 780 nm frequency-stabilized diode laser with a power of as high as 2.825 W, corresponding to an estimated overall efficiency of 38.5%. The tapered amplifier (TPA) gain was about 24.5 dB, which was basically consistent with the simulation results. The beam quality factor was M2<1.72. The core feature of the system was stabilizing the frequency of the narrowband semiconductor TPA system with the matured saturated absorption spectrum technique. The laser frequency was stabilized against mode hops for a period of >4200 s with a frequency fluctuation around 6.7×10-10 within 1 s of the observation period, and the linewidth was no more than 0.95 MHz. The laser performance indicates that the current frequency-stabilized semiconductor laser has great potential in certain conditions that require several watts of output power.

High-slope-efficiency 2.06 μm Ho: YLF laser in-band pumped by a fiber-coupled broadband diode.

We first demonstrate the laser performance of a compact 2.06 μm Ho: YLF laser resonantly pumped by a broadband fiber-coupled diode. In continuous-wave (CW) operation, maximum output power of 1.63 W, corresponding to a slope efficiency of 89.2%, was obtained with a near diffraction-limited beam quality. In actively Q-switched operation, maximum pulse energy of 1.1 mJ was achieved at the repetition frequency of 100 Hz. The minimum pulse duration was 43 ns. The performance in both the CW and Q-switched regimes indicates that the current fiber-coupled diode in-band pumped Ho: YLF laser has great potential in certain conditions that require several watts of output power or several millijoules of short pulse energy.

Modeling of transient modal instability in fiber amplifiers

A model of transient modal instability in fiber amplifiers is presented. This model combines an optical beam propagation method that incorporates laser gain through local solution of the rate equations and refractive index perturbations caused by the thermo-optic effect with a time-dependent thermal solver with a quantum defect heating source term. This model predicts modal instability a fiber amplifier operating at 241, 270, and 287 Watts of output power characterized by power coupling to un-seeded modes, the presence of stable and unstable regions within the fiber, and rapid intensity variations along the fiber. The instability becomes more severe as the power is increased.

156 µm 1 watt single frequency semiconductor disk laser

A single frequency wafer-fused semiconductor disk laser at 1.56 µm with 1 watt of output power and a coherence length over 5 km in fiber is demonstrated. The result represents the highest output power reported for a narrow-line semiconductor disk laser operating at this spectral range. The study shows the promising potential of the wafer fusion technique for power scaling of single frequency vertical-cavity lasers emitting in the 1.3-1.6 µm range.

11 W narrow linewidth laser source at 780nm for laser cooling and manipulation of Rubidium

We present a narrow linewidth continuous laser source with over 11 Watts of output power at 780nm, based on single-pass frequency doubling of an amplified 1560nm fibre laser with 36% efficiency. This source offers a combination of high power, simplicity, mode quality and stability. Without any active stabilization, the linewidth is measured to be below 10kHz. The fibre seed is tunable over 60GHz, which allows access to the D2 transitions in 87Rb and 85Rb, providing a viable high-power source for laser cooling as well as for large-momentum-transfer beamsplitters in atom interferometry. Sources of this type will pave the way for a new generation of high flux, high duty-cycle degenerate quantum gas experiments.

Power voltage-current converter using quasi-complementary MOSFET current mirrors

A voltage current convertor is described having a quasi complementary class AB architecture that is particularly suited to implementation using discrete power MOSFETs. High-voltage mirror designs are presented, enabling the construction of sources with kilovolt compliance range, tens of watts of output power and greater than 100 kHz bandwidth. GΩ output impedance and distortion below 1% can be obtained with no trimming or transistor matching.

레이더용 X-대역 63 Watt Pulsed SSPA 개발

본 논문에서는 소형 하이브리드 HMIC(Hybrid Microwave Integrated Circuits)를 사용하여 레이더용 X-대역 63 watt 펄스 구동형(pulsed) SSPA(Solid State Power Amplifier)를 개발하였다. Pulsed SSPA는 전원공급기와 초단증폭기, 구동증폭기, 고출력을 위한 최종단 증폭기의 3단의 증폭기로 구성되어 있다. 70도의 고온에서도 듀티 1.2%이고, 짧은 펄스 폭에서 63 watts 이상의 출력을 얻었다. 제작된 모듈은 동작대역 내에서 포화 상태의 이득 37 dB 성능을 보였다. 입출력 정재파비는 1.5:1 미만을 만족하였다. 이 모듈은 +28 <TEX>$V_{dc}$</TEX>로 동작되고 400 mA 전력 소모를 가진다. 본 논문에서 개발한 SSPA는 고속으로 동작하는 펄스 도플러 레이더에 적용할 수 있다. In this paper, we developed the X-band 63 watt pulsed SSPA(Solid State Power Amplifier) by using HMIC(Hybrid Microwave Integrated Circuits). The pulsed SSPA consists of power supply and 3-stage amplifier modules : pre-amplifier stage, driver-amplifier stage, final-amplifier stage. The developed pulsed SSPA provides more than 63 watts of output power with a short pulse width and the duty cycle of up to 1.2 % at <TEX>$70^{\circ}C$</TEX>. The fabricated module offers great than 37 dB of saturated gain across the operating band. Input and output VSWR is <1.5:1. This module has an average current of 400 mA typical and operates at a +28 <TEX>$V_{dc}$</TEX> supply. The developed SSPA in this paper can apply to pulsed Doppler radar with high speed operation.

Fiber-MOPA sources of coherent radiation

This paper presents the concept and design of medium to high power fiber radiation sources in MOPA (Master Oscillator Power Amplifier) configuration. Research results are presented on a two-stage power amplifier for MOPA applications for the third telecommunications window at 1550 nm based on active erbium-doped and erbium/ytterbium-doped fibers. The amplifier is fabricated entirely in fiber technology and delivers several watts of output power.

Limits on efficiency and power scaling in semiconductor disk lasers with diamond heatspreaders

The semiconductor disk laser (SDL) is a versatile laser source offering multiwatt-level output powers and diffraction limited beams. While an approach to thermal management based on substrate removal has led to tens of watts of output power in the 1 μm region, the use of intracavity diamond heatspreaders for thermal management has enabled multiwatt performance levels to be achieved at wavelengths from the red to the mid-infrared. The modeling presented indicates that this dichotomy in approach arises from the ability of the heatspreader approach to bypass the thermal resistance of the mirror structure built into the SDL. The power scaling limitations of SDLs with heatspreaders are explored: nonaxial heat flow in the heatspreader is shown to limit the power scaling with pump spot radius. The critical roles of the pump spot size and output coupling on efficiency are experimentally investigated. An output power of 7 W in a 1060 nm SDL is achieved with the maximum output power achieved at a pump spot radius of 85 μm.

Efficient continuous-wave thin disk laser operation of Yb:Ca_4YO(BO_3)_3 in E∥Z and E∥X orientations with 26 W output power

We report continuous-wave laser operation with Yb(15 at. %):Ca4YO(BO3)3 (Yb:YCOB) reaching 26 W of output power in the thin disk laser setup at an optical-to-optical efficiency of 58% and a slope efficiency of 67% in the E∥Z polarization. In the E∥X polarization the efficiency of the laser was slightly lower, but a large tuning range of 95 nm with several watts of output power could be obtained here. Furthermore, applying the pinhole method, the fluorescence lifetime was determined to be 2.2 ms. The obtained results reveal that Yb:YCOB is a promising candidate for the generation of very short pulses at high pulse energies in the thin disk laser setup.

Birefringence-induced bifocusing for selection of radially or azimuthally polarized laser modes

We develop a round-trip matrix diagonalization method for quantitative description of selection of radially or azimuthally polarized beams by birefringence-induced bifocusing in a simple laser resonator. We employ different focusing between radially and tangentially polarized light in thermally stressed laser rods to obtain low-loss stable oscillation in a radially polarized Laguerre-Gaussian, LG(0,1)*, mode. We derive a free-space propagator for the radially and azimuthally polarized LG(0,1)* modes and explain basic principles of mode selection by use of a round-trip matrix diagonalization method. Within this method we calculate round-trip diffraction losses and intensity distributions for the lowest-loss transverse modes. We show that, for the considered laser configuration, the round-trip loss obtained for the radially polarized LG(0,1)* mode is significantly smaller than that of the azimuthally polarized mode. Our experimental results, obtained with a diode side-pumped Nd:YAG rod in a flat-convex resonator, confirm the theoretical predictions. We achieved a pure radially polarized LG(0,1)* beam with M(2)=2.5 and tens of watts of output power.

502 Watt, single transverse mode, narrow linewidth, bidirectionally pumped Yb-doped fiber amplifier

High power operation of narrow linewidth optical fiber amplifiers is usually limited by the onset of stimulated Brillouin scattering. In this paper, we present results demonstrating over 500 Watts of power in a single mode beam from a fiber designed to suppress stimulated Brillouin scattering through a reduction in the overlap of the optical and acoustic fields. Simulations demonstrate the potential for this fiber to achieve greater than 1000 Watts of output power.

Power scaling of highly neodymium-doped YAG ceramic lasers with a bounce amplifier geometry

High power operation of highly-doped ceramic Nd:YAG laser is demonstrated using a laser diode transversely-pumped bounce geometry. Using a 2% doped ceramic Nd:YAG amplifier, an output power of 45W was achieved with 158W diode pumping. The cavity configuration was optimized for TEM00 operation and a high spatial quality output (M2 >1.5) was obtained at an output power of 27W. A ceramic Nd:YAG laser with 4% doping was operated at over 1 watt of output power. These are the highest power levels achieved in ceramic Nd:YAG lasers at >1% doping level.