scholarly journals Charged particle spectra from U-235 and B-10 micropellets and slab coatings

1984 ◽  
Vol 2 (2) ◽  
pp. 201-211 ◽  
Author(s):  
A. K. Chung ◽  
M. A. Prelas
Keyword(s):  
Charged Particle ◽  
Low Power ◽  
Power Density ◽  
Fission Fragment ◽  
High Efficiency ◽  
Nuclear Reactions ◽  
Length Distribution ◽  
Laser Medium ◽  
Fissile Material ◽  
Particle Spectrum

A novel method of utilizing fluorescence generated from the products of nuclear reactions offers the prospect of compact, high efficiency, multi-megajoule lasers. To overcome the problems associated with traditional laser (or energy converter)-fissile material interfaces, such as a uranium coating (low power density and low efficiency) or a gaseous uranium compound (low power density and deleterious effects on the laser kinetics and photon transport), a method suggested elsewhere of employing a reactor using a uranium aerosol fuel, interspersed with a fluorescer medium, is briefly reviewed. The charged particles produced by nuclear reactions in the fuel produce fluorescence in the core region of the reactor, through interactions with the fluorescer. This fluorescence can then be concentrated, to increase the effective power density in the laser medium, and used to drive a photolytic laser.One key issue in the above process is the charged particle spectrum from the fissile aerosol. These issues can be addressed theoretically based on the Dirac chord length distribution technique and an Arcen's function. The charged particle spectrum from a UO2 coating has been generated and benchmarked with the experimental data of Kahn et al., and Redmond et al. Agreement is generally good except near the end of the fission fragment tracks. The validity of this simple technique in approximating the rate of ion energy loss lends confidence to the generation of fission fragment spectra for other geometries (i.e. spherical in which transport efficiencies of over 60% appear achievable) using U, UO2 and U3O8. Work is also extended to the case of B-10 in a variety of configurations which are frequently used in modern energy conversion experimental devices.

scholarly journals Nuclear driven flashlamps

1988 ◽  
Vol 6 (1) ◽  
pp. 25-62 ◽  
Author(s):  
M. A. Prelas ◽  
F. P. Boody ◽  
G. H. Miley ◽  
J. F. Kunze
Keyword(s):  
Low Power ◽  
Power Density ◽  
High Power ◽  
Nuclear Reactions ◽  
Narrow Band ◽  
Efficient Production ◽  
High Power Lasers ◽  
Sufficient Power ◽  
Band Fluorescence ◽  
Power Densities

Due to the low power density of pumping schemes for nuclear-pumped lasers prior to 1978, a method of utilizing the efficient production of narrow band fluorescence from excimers was developed. This method has since been referred to as a nuclear driven flashlamp. It is possible to achieve sufficient power densities, when combining the flashlamp with novel techniques of reactor/laser interfaces, to drive efficient, high power lasers directly with products from nuclear reactions.

Low-Power Triplet-Triplet Annihilation Upconversion with a New Anthracene Derivatives

2016 ◽  
Vol 852 ◽  
pp. 1265-1270
Author(s):  
Sai Jiang Zhu ◽  
Chang Qing Ye ◽  
Yan Fu ◽  
Zuo Qing Liang ◽  
Xiao Mei Wang
Keyword(s):  
Quantum Yield ◽  
Low Power ◽  
Power Density ◽  
High Efficiency ◽  
Excitation Power ◽  
Quantum Yields ◽  
Excitation Power Density ◽  
High Quantum ◽  
Anthracene Derivatives ◽  
Triplet Triplet Annihilation

Two new anthracene derivatives were synthesized as emitter for low power triplet-triplet annihilation upconversion. Compared with anthracene, the emitter exhibits high quantum yields up to 85%. Pd (II) tetraphenylporphyrin which was selected as the sensitizer with the existence of BBA in DMF, We find a pretty high efficiency (Φuc=21.9%) of the upconversion fluorescence at 532nm with a low excitation power density of 0.5w/cm2.With the comparison of Anthracene, BBA and BTPA systems, quantum yield of the emitter is very important to the improving of the efficiency of upconversion.

scholarly journals ZVS Auxiliary Circuit for a 10 kW Unregulated LLC Full-Bridge Operating at Resonant Frequency for Aircraft Application

Energies ◽  
2019 ◽  
Vol 12 (10) ◽  
pp. 1850 ◽  
Author(s):  
Yann E. Bouvier ◽  
Diego Serrano ◽  
Uroš Borović ◽  
Gonzalo Moreno ◽  
Miroslav Vasić ◽  
...  
Keyword(s):  
Resonant Frequency ◽  
Power Density ◽  
High Efficiency ◽  
Harmonic Approximation ◽  
Maximum Efficiency ◽  
Voltage Gain ◽  
Load Range ◽  
Transition Analysis ◽  
Aircraft Application ◽  
Auxiliary Circuit

In modern aircraft designs, following the More Electrical Aircraft (MEA) philosophy, there is a growing need for new high-power converters. In this context, innovative solutions to provide high efficiency and power density are required. This paper proposes an unregulated LLC full-bridge operating at resonant frequency to obtain a constant gain at all loads. The first harmonic approximation (FHA) model is not accurate enough to estimate the voltage gain in converters with high parasitic resistance. A modified FHA model is proposed for voltage gain analysis, and time-based models are used to calculate the instantaneous current required for the ZVS transition analysis. A method using charge instead of current is proposed and used for this ZVS analysis. Using this method, an auxiliary circuit is proposed to achieve complete ZVS within the whole load range, avoiding a gapped transformer design and increasing the efficiency and power density. A 28 Vdc output voltage prototype, with 10 kW peak output power, has been developed to validate the theoretical analysis and the proposed auxiliary circuit. The maximum efficiency (96.3%) is achieved at the nominal power of 5 kW.

scholarly journals Low Power Cusped Field Thruster Developed for the Space-Borne Gravitational Wave Detection Mission in China

2021 ◽  
Vol 11 (14) ◽  
pp. 6549
Author(s):  
Hui Liu ◽  
Ming Zeng ◽  
Xiang Niu ◽  
Hongyan Huang ◽  
Daren Yu
Keyword(s):  
Low Power ◽  
Gravitational Wave ◽  
Attitude Control ◽  
High Efficiency ◽  
Experimental Investigations ◽  
Attitude Control System ◽  
Gravitational Wave Detection ◽  
Wave Detection ◽  
Wide Range ◽  
Institute Of Technology

The microthruster is the crucial device of the drag-free attitude control system, essential for the space-borne gravitational wave detection mission. The cusped field thruster (also called the High Efficiency Multistage Plasma Thruster) becomes one of the candidate thrusters for the mission due to its low complexity and potential long life over a wide range of thrust. However, the prescribed minimum of thrust and thrust noise are considerable obstacles to downscaling works on cusped field thrusters. This article reviews the development of the low power cusped field thruster at the Harbin Institute of Technology since 2012, including the design of prototypes, experimental investigations and simulation studies. Progress has been made on the downscaling of cusped field thrusters, and a new concept of microwave discharge cusped field thruster has been introduced.

scholarly journals Analysis and Pareto Frontier Based Tradeoff Design of an Integrated Magnetic Structure for a CLLC Resonant Converter

Energies ◽  
2021 ◽  
Vol 14 (6) ◽  
pp. 1756
Author(s):  
Gang Wang ◽  
Qiyu Hu ◽  
Chunyu Xu ◽  
Bin Zhao ◽  
Xiaobao Su
Keyword(s):  
Magnetic Structure ◽  
Power Density ◽  
High Efficiency ◽  
Pareto Frontier ◽  
Optimization Procedure ◽  
Magnetic Core ◽  
Pareto Optimization ◽  
High Power Density ◽  
Resonant Converter ◽  
Conduction Loss

This paper proposes an integrated magnetic structure for a CLLC resonant converter. With the proposed integrated magnetic structure, two resonant inductances and the transformer are integrated into one magnetic core, which improves the power density of the CLLC resonant converter. In the proposed integrated magnetic structure, two resonant inductances are decoupled with the transformer and can be adjusted by the number of turns in each inductance. Furthermore, two resonant inductances are coupled to reduce the number of turns in each inductance. As a result, the conduction loss can be reduced. The trade-off design of the integrated magnetic structure is carried out based on the Pareto optimization procedure. With the Pareto optimization procedure, both high efficiency and high-power density can be achieved. The proposed integrated magnetic structure is validated by theoretical analysis, simulations, and experiments.

scholarly journals Near-field thermophotovoltaics for efficient heat to electricity conversion at high power density

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Rohith Mittapally ◽  
Byungjun Lee ◽  
Linxiao Zhu ◽  
Amin Reihani ◽  
Ju Won Lim ◽  
...  
Keyword(s):  
Power Density ◽  
High Power ◽  
High Efficiency ◽  
Near Field ◽  
Electrical Power ◽  
Photovoltaic Cells ◽  
High Power Density ◽  
Pv Cell ◽  
Electrical Power Output ◽  
Power Densities

AbstractThermophotovoltaic approaches that take advantage of near-field evanescent modes are being actively explored due to their potential for high-power density and high-efficiency energy conversion. However, progress towards functional near-field thermophotovoltaic devices has been limited by challenges in creating thermally robust planar emitters and photovoltaic cells designed for near-field thermal radiation. Here, we demonstrate record power densities of ~5 kW/m2 at an efficiency of 6.8%, where the efficiency of the system is defined as the ratio of the electrical power output of the PV cell to the radiative heat transfer from the emitter to the PV cell. This was accomplished by developing novel emitter devices that can sustain temperatures as high as 1270 K and positioning them into the near-field (<100 nm) of custom-fabricated InGaAs-based thin film photovoltaic cells. In addition to demonstrating efficient heat-to-electricity conversion at high power density, we report the performance of thermophotovoltaic devices across a range of emitter temperatures (~800 K–1270 K) and gap sizes (70 nm–7 µm). The methods and insights achieved in this work represent a critical step towards understanding the fundamental principles of harvesting thermal energy in the near-field.

scholarly journals Alternating Current Loss of Superconductors Applied to Superconducting Electrical Machines

Energies ◽  
2021 ◽  
Vol 14 (8) ◽  
pp. 2234
Author(s):  
Hongye Zhang ◽  
Zezhao Wen ◽  
Francesco Grilli ◽  
Konstantinos Gyftakis ◽  
Markus Mueller
Keyword(s):  
Quantitative Analysis ◽  
Power Density ◽  
High Efficiency ◽  
Alternating Current ◽  
Coated Conductors ◽  
Ac Loss ◽  
Electrical Machines ◽  
Qualitative And Quantitative Analysis ◽  
Qualitative And Quantitative ◽  
Reduction Techniques

Superconductor technology has recently attracted increasing attention in power-generation- and electrical-propulsion-related domains, as it provides a solution to the limited power density seen by the core component, electrical machines. Superconducting machines, characterized by both high power density and high efficiency, can effectively reduce the size and mass compared to conventional machine designs. This opens the way to large-scale purely electrical applications, e.g., all-electrical aircrafts. The alternating current (AC) loss of superconductors caused by time-varying transport currents or magnetic fields (or both) has impaired the efficiency and reliability of superconducting machines, bringing severe challenges to the cryogenic systems, too. Although much research has been conducted in terms of the qualitative and quantitative analysis of AC loss and its reduction methods, AC loss remains a crucial problem for the design of highly efficient superconducting machines, especially for those operating at high speeds for future aviation. Given that a critical review on the research advancement regarding the AC loss of superconductors has not been reported during the last dozen years, especially combined with electrical machines, this paper aims to clarify its research status and provide a useful reference for researchers working on superconducting machines. The adopted superconducting materials, analytical formulae, modelling methods, measurement approaches, as well as reduction techniques for AC loss of low-temperature superconductors (LTSs) and high-temperature superconductors (HTSs) in both low- and high-frequency fields have been systematically analyzed and summarized. Based on the authors’ previous research on the AC loss characteristics of HTS coated conductors (CCs), stacks, and coils at high frequencies, the challenges for the existing AC loss quantification methods have been elucidated, and multiple suggestions with respect to the AC loss reduction in superconducting machines have been put forward. This article systematically reviews the qualitative and quantitative analysis methods of AC loss as well as its reduction techniques in superconductors applied to electrical machines for the first time. It is believed to help deepen the understanding of AC loss and deliver a helpful guideline for the future development of superconducting machines and applied superconductivity.

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