Power Amplification Factor Research Articles

Fabrication, conditioning and installation of the 1st high gradient S-band accelerating module for the energy upgrade of the FERMI free electron laser linac

FERMI is the seeded free electron laser (FEL) user facility at Elettra laboratory in Trieste, operating in the VUV to soft X-rays spectral range. In order to extend the FEL spectral range to shorter wavelengths, an increase in the linear accelerator (linac) energy from 1.5 GeV to 2.0 GeV is required. This result will be achieved by replacing the present old sections with the newly designed accelerating sections which can work at high gradient with lower transverse wakefields. After the successful testing of a short prototype, 354 mm in length, of a new high-gradient (HG) section that sustained an accelerating gradient of 40 MV/m with a breakdown rate (BDR) of 8×10−8 bpp, two 3.0 m HG structures with the same design were built and installed at the FERMI linac. We report here the recent experience on the conditioning and installation of the first high gradient sections and the operation of the spherical pulse compressor prototype, conditioned up to 100 MW output power with a power amplification factor of 3.5.

Concept of terahertz waveguide plasmon amplifier based on a metal groove with active graphene

We propose a concept of terahertz waveguide plasmon amplifier based on a metal groove with active graphene. It is shown that the power amplification factor of the longitudinal-section magnetic (LSM) waveguide plasmon (normalized to its wavelength) near the cut-off frequency of this mode can exceed the amplification factor of the transverse magnetic (TM) plasmon in a layered graphene structure by more than four orders of magnitude for the same frequency. This is caused by the increase of the LSM plasmon wavelength near the cut-off frequency, smaller energy velocity of the LSM mode, and greater energy release from graphene for the LSM plasmon due to stronger lateral confinement of the LSM waveguide plasmon as compared to the TM plasmon in a layered graphene structure. We show that the enhancement of the LSM plasmon amplification factor near the cut-off frequency is a stronger effect than that due to screening of graphene.

Hybrid Fusion-Fission System with Neutron Source Based on Deuterium Plasma

Development of hybrid fusion-fission systems appears today as a promising area in practical use of thermonuclear fusion energy. Thermonuclear plasma in such systems is the source of fast neutrons with the power gain factor Q < 1 power amplification factor in plasma. Hybrid system high amplification is generally achieved through nuclear reactions in the subcritical blanket surrounding plasma. Not only power could be produced in such a blanket, but also nuclear fuel, and waste of the nuclear fuel cycle could be disposed. The problem of systems using the thermonuclear reaction between deuterium and tritium lies in the lack of tritium reserves and in the limited possibilities of its production. Therefore, the work considers organization of a fuel cycle based on the deuterium-deuterium reaction. Options of a neutron source based on tokamak and linear system of the open trap type were examined. Magnitude of the socalled hybrid system electrical efficiency (ratio of the system electrical output to the blanket thermal power) was estimated. Calculations demonstrated fundamental possibility of realizing substantial neutron yield from deuterium plasma. To achieve acceptable performance, power gain in thermonuclear plasma should be Q = 0.5--1. In a tokamak of reasonable scale and when working on deuterium, the gain should be Q ~ 0.3. Potential advantages of linear systems associated with the possibility of high-pressure plasma confinement are presented

Experimental study on models of cylindrical steel tanks under mining tremors and moderate earthquakes

The aim of the study is to show the results of complex shaking table experimental investigation focused on the response of two models of cylindrical steel tanks under mining tremors and moderate earthquakes, including the aspects of diagnosis of structural damage. Firstly, the impact and the sweep-sine tests have been carried out, so as to determine the dynamic properties of models filled with different levels of liquid. Then, the models have been subjected to seismic and paraseismic excitations. Finally, one fully filled structure has been tested after introducing two different types of damages, so as to verify the method of damage diagnosis. The results of the impact and the sweep-sine tests show that filling the models with liquid leads to substantial reduction in natural frequencies, due to gradually increasing overall mass. Moreover, the results of sweep-sine tests clearly indicate that the increase in the liquid level results in significant increase in the damping structural ratio, which is the effect of damping properties of liquid due to its sloshing. The results of seismic and paraseismic tests indicate that filling the tank with liquid leads initially to considerable reduction in values of acceleration (damping effect of liquid sloshing); however, beyond a certain level of water filling, this regularity is inverted and acceleration values increase (effect of increasing total mass of the structure). Moreover, comparison of the responses under mining tremors and moderate earthquakes indicate that the power amplification factor of the mining tremors may be larger than the seismic power amplification factor. Finally, the results of damage diagnosis of fully filled steel tank model indicate that the forms of the Fourier spectra, together with the frequency and power spectral density values, can be directly related to the specific type of structural damage. They show a decrease in the natural frequencies for the model with unscrewed support bolts (global type of damage), while cutting the welds (local type of damage) has resulted in significant increase in values of the power spectral density for higher vibration modes.

Study on an elastic lever system for electromagnetic energy harvesting from rail vibration

Energy harvesting from rail vibration is a promising approach to solve the power supply problem in remote and off-grid areas. The major issue of current energy harvesting techniques and devices is the limited power generating capacity. In this paper, the authors put forward an elastic lever system to enhance the performance of an electromagnetic energy harvester. A vehicle-track coupling dynamics model is established to simulate the service condition of the energy harvester. The Power Amplification Factor (PAF), which is defined as the ratio between the output power with and without a lever system, is introduced to quantify the Enhanced Energy Harvester (EEH). It is found that the PAF can be greater than n2 with a leverage ratio of n. Simulation shows that the output power can be magnified by 430 times with an elastic lever system with a leverage ratio of 10. The amplification effect of the output power comes from two aspects, one is the magnifying effect of leverage itself and the other is the resonance effect. Additionally, it is found that a single EEH will increase the wheel-rail contact force slightly, which indicates the EEH is impractical for use as an approach for rail vibration reduction. Nevertheless, it will not have a significant negative effect on rail vibration.

Effect of thermally induced birefringence on high power picosecond azimuthal polarization Nd:YAG laser system**Project supported by the National Natural Science Foundation of China (Grant No. U1631240), the Education Commission Program of Beijing, and Beijing Natural Science Foundation (Grant No. KZ201510005001).

Pulse-burst 1064-nm picosecond azimuthal polarization beam amplification up to an average power of 16.32 W using side-pumped Nd: YAG amplifiers has been demonstrated. The maximum envelop energy as much as 16.32 mJ, corresponding to a power amplification factor of 299.5%. A simple criterion was defined to help estimate the amount of depolarization in Nd:YAG amplifier stages. The degree of depolarization of the beam was 7.1% and the beam quality was measured to be M2=3.69. The reason for the azimuthal polarization depolarization and beam quality degradation were explained theoretically and experimentally during the amplification process.

Performance Evaluation of Mechanical Power Amplifier for Various Belt Materials

Background: In many applications, it is required to control a large output load using a relatively low control force. To satisfy such purposes, a device like mechanical power amplifier can be used which generally gives a very fast response. As per the requirement of the system, power can be instantaneously available from continuously rotating drums of the mechanical power amplifier. Objective: This paper focuses on the computation of amplification factor of the mechanical power amplifier for different rope materials like leather, woven cotton and steel rope. Method: In this study the experimental analysis is performed. A capstan is a simple mechanical amplifier-rope wound on a motor-driven drum. The drums rotate continuously but communicate torque only when the input shaft is rotated to constricts drum A as shown in Fig. (3). Results: From the experimental analysis, it endorses that when the optimal number of turns tend to two, power amplification factor is to be 2.23 for leather contact, 1.867 for woven cotton contact, 1.32 for steel contact of rope. Conclusion: From the experimental analysis, it is seen that power amplification is higher for leather as compared to woven cotton and steel. The results are remarkably consistent with experimental measurements including favorable calculation of amplification factor.

SIMULATION OF THE CHARACTERISTICS OF AN ACTIVE MICROWAVE POWER COMPRESSOR

In the paper, a model analysis is given to operation of an active microwave power compressor consisting of a waveguide storage resonator and interference switch commutated by the conductivity variation in the local region inside of it. Dynamics of the transient processes that occur during switching the storage resonator from the power accumulation mode to the mode of power release into an offtake waveguide is analyzed. The obtained numerical estimates of the power amplification factor are close to the theoretical limit. The shape and length of the compressed pulse obtained in the numerical simulation are close to the desirable ones. To provide more accurate reconstruction of the time profile of the output signal, further optimization of the compressor geometry is required.

Stochastic geometry based asymptotic analysis for two‐tier HetNets with massive MIMO relay employing MRC/MRT and ZF processing

AbstractThis paper focuses on the multi‐pair amplify‐and‐forward massive multiple‐input multiple‐output (MIMO) relay enabled two‐tier heterogeneous cellular networks in terms of aggregate spectral efficiency (SE), where the macro cells are overlaid with dense small cells. Specially, the maximum ratio combining/maximal ratio transmission and zero‐forcing processing schemes are employed at massive MIMO relay, respectively. The macro base stations located in the center of the cells are equipped with massive MIMO antenna array, while the randomly distributed macro users (MUs), small cell base stations, and small cell users are equipped with single antenna. The positions of MUs, small cell users and small cell base stations are modelled as independent Poisson point processes. For such two‐tier heterogeneous cellular networks, to obtain the aggregate SE in target cell, we first formulate the end‐to‐end signal‐to‐interference noise ratios for a communication pair as well as the expression of power amplification factor at target macro base stations so that the total spectrum efficiency per cell is formulated. Then, by employing stochastic geometry, the closed‐form expressions of the power amplification factor and the expectation of the reciprocal of the equivalent end‐to‐end signal‐to‐interference noise ratios are achieved. With these results, we derive the lower bounds of SEs for maximum ratio combining/maximal ratio transmission and zero‐forcing schemes. The derivations display a clear perspective about the impact of network parameters on the system‐level performance, which includes macro cell radius, small cell radius, macro cell guard radius, the mean number of MUs per cell and so on. To achieve optimal (or suboptimal) system performance, we find that the radius of small cell should be less than the guard radius. For the guard radius, there exists an upper bound, only under which the increase of the guard radius would contribute to the improvement of SE. At the same time, our results show that with given network parameters, especially the guard radius and the small cell radius, there exists a unique greatest lower bound in terms of macro cell radius. When the macro cell radius is less than the greatest lower bound, the aggregate SE is increasing with the macro cell radius. On the contrary, the achievable aggregate SE saturates to the corresponding constant, approximately. In addition, the greatest lower bound of the macro cell radius is the function of the guard radius and the small cell radius. Copyright © 2016 John Wiley & Sons, Ltd.

Correlated noise-based switches and stochastic resonance in a bistable genetic regulation system

The correlated noise-based switches and stochastic resonance are investigated in a bistable single gene switching system driven by an additive noise (environmental fluctuations), a multiplicative noise (fluctuations of the degradation rate). The correlation between the two noise sources originates from on the lysis-lysogeny pathway system of the λ phage. The steady state probability distribution is obtained by solving the time-independent Fokker-Planck equation, and the effects of noises are analyzed. The effects of noises on the switching time between the two stable states (mean first passage time) is investigated by the numerical simulation. The stochastic resonance phenomenon is analyzed by the power amplification factor. The results show that the multiplicative noise can induce the switching from “on” → “off” of the protein production, while the additive noise and the correlation between the noise sources can induce the inverse switching “off” → “on”. A nonmonotonic behaviour of the average switching time versus the multiplicative noise intensity, for different cross-correlation and additive noise intensities, is observed in the genetic system. There exist optimal values of the additive noise, multiplicative noise and cross-correlation intensities for which the weak signal can be optimal amplified.

Superconducting Cavities in Systems of the Resonant Microwave Pulse Compression

Evaluations for possible using of superconducting materials in high power microwave generators based on the method of the resonant microwave compression were made. As an example the relationship between the power amplification factor and frequency was determined for superconducting rectangular cavities. Capabilities of superconducting cavities as energy accumulators were analyzed. Microwave power value required for feeding superconducting accumulator is estimated. Experimental results of storing and extracting the energy in superconducting cavities are presented.

Spectrum Sensing and Data Transmission in a Cognitive Relay Network Considering Spatial False Alarms

In this paper, the average probability of the symbol error rate (SER) and throughput are studied in the presence of joint spectrum sensing and data transmission in a cognitive relay network, which is in the environment of an optimal power allocation strategy. In this investigation, the main component in calculating the secondary throughput is the inclusion of the spatial false alarms, in addition to the conventional false alarms. It has been shown that there exists an optimal secondary power amplification factor at which the probability of SER has a minimum value, whereas the throughput has a maximum value. We performed a Monte-Carlo simulation to validate the analytical results.

Wind Tower System With a Helical Wind Deflecting Structure, Computational Fluid Dynamics, and Experimental Studies

A wind tower system having a three dimensional heliacal wind deflecting structure is studies in this work. The purpose of the helical structure is to increase the natural wind speed and direct the follow of the wind toward two columns of horizontal-axis rooftop-size wind turbines that are installed in the grooves of the helical structure, diametrically opposed to each other. Computational fluid dynamics analyses were conducted to determine the influence of the helical structure on the wind speed reaching the turbines. A wind speed amplification coefficient was determined for a helical structure of 6.7 m outer diameter. The velocity profiles of the wind flow around the helical structure were determined under a postulated wind speed of 4.47 m/s. The flow was modeled as turbulent with a Reynolds Number of 2,052,167. Standard “k–ε” turbulent model with “near wall treatment” and “standard wall function” were adapted in all analysis. A “y+” value of 50 was held constant in all simulation. The grid-size effects on the accuracy of the results were examined. Convergence criterion was satisfied in each case. This study shows that the helical structure having an outer diameter of 6.7 m results in an average wind speed increase factor of 1.52. An experimental wind tower system was fabricated and installed at an elevation of 40 m above the ground. The wind tower system comprised of four identical rooftop size wind turbines, each having 1.6 KW name-plate-rating. A helical wind deflecting structure of 11 m tall, and 7 m in major diameter was used in fabrication of the tower. An active yaw-control mechanism was used to orient the tower into the prevailing wind. The experimental results show that as the result of the use of the wind deflecting structure, an average power amplification factor of 4.69 was obtained for the tower, in comparison with the standard standalone installation of the four wind turbines.

Superimposed training for channel estimation of OFDM modulated amplify-and-forward relay networks

This paper is concerned with the problem of channel estimation for amplify-and-forward (AF) cooperative relay networks with orthogonal frequency division multiplexing (OFDM) modulation. The algorithm is based on both the least square (LS) and minimum mean square error (MMSE) technique with a superimposed training strategy. Specifically, both the source and relay superimpose their own training signal onto data stream prior to transmission so as to estimate the separate channel state information of the source to relay link and the relay to destination link. We also present the performance analysis and derive the approximated closed-form expressions for the MSE of separate channel estimation of source to relay link and the relay to destination link, respectively, from which we compute the optimal training signal as well as the relay power-amplification factor. To further improve the performance of channel estimation, we adopt a weighted average process to enhance the estimation performance over multiple OFDM blocks, from which we compute the optimal tracking factor. Simulation results are provided to corroborate the proposed scheme.

Radiative type-III ELMy H-mode in all-tungsten ASDEX Upgrade

The type-III ELMy H-mode might be the solution for an integrated ITER operation scenario fulfilling the fusion power amplification factor (output fusion power to input heating power) of Q = 10 with simultaneous acceptable steady-state and transient power loads to the plasma-facing components. This highly radiative type-III ELMy H-mode is achieved by nitrogen seeding. Experiments on the tokamak ASDEX Upgrade, in which all plasma-facing components are coated with tungsten, showed favourable confinement conditions (H98(y,2) = 1) at high plasma pressure (βN = 2.4). The power load to the plasma-facing components is as low as ≈3 MW m−2 during the peak heat loads due to edge localized modes (ELMs) at high radiative power fractions of frad ≈ 0.75. In those high-density discharges the central impurity concentration is very low as a result of hollow nitrogen density profiles and minimal erosion of tungsten. The tungsten erosion is not only suppressed in between ELMs, when the divertor is detached, but also during the type-III ELM activity. Such low impurity concentrations in the plasma core might lead to even higher fusion amplification factors in ITER than 10. This is a demonstration of the compatibility of the radiating type-III ELMy H-mode with a tungsten divertor and main chamber wall, with sufficient confinement and favourable power exhaust characteristics. Together with previous results in all-carbon devices this demonstration strengthens the case for a potential application of a Q = 10 scenario on ITER.

How a single stretched polymer responds coherently to a minute oscillation in fluctuating environments: An entropic stochastic resonance

Within the cell, biopolymers are often situated in constrained, fluid environments, e.g., cytoskeletal networks, stretched DNAs in chromatin. It is of paramount importance to understand quantitatively how they, utilizing their flexibility, optimally respond to a minute signal, which is, in general, temporally fluctuating far away from equilibrium. To this end, we analytically study viscoelastic response and associated stochastic resonance in a stretched single semi-flexible chain to an oscillatory force or electric field. Including hydrodynamic interactions between chain segments, we evaluate dynamics of the polymer extension in coherent response to the force or field. We find power amplification factor of the response at a noise-strength (temperature) can attain the maximum that grows as the chain length increases, indicative of an entropic stochastic resonance (ESR). In particular for a charged chain under an electric field, we find that the maximum also occurs at an optimal chain length, a new feature of ESR. The hydrodynamic interaction is found to enhance the power amplification, representing unique polymer cooperativity which the fluid background imparts despite its overdamping nature. For the slow oscillatory force, the resonance behavior is explained by the chain undulation of the longest wavelength. This novel ESR phenomenon suggests how a biopolymer self-organizes in an overdamping environment, utilizing its flexibility and thermal fluctuations.

Comments on the power amplification factor of a driven subcritical system

The power amplification factor PAF of a driven subcritical system is defined as the ratio of the fission power output of the blanket to the power which the driver must deliver to sustain its neutron source intensity. This parameter decisively determines the effectiveness of the whole system independent of its special purpose as energy amplifier or as transmutation facility. The present note derives a refined analytical expression for the PAF which reveals more physical details than the expressions given by other authors. Moreover, the traditionally used forms of the static reactor eigenvalue equation and of its adjoint equation are rewritten for subcritical systems and used in the derivation of the expression for the PAF. The derived formula and the modified eigenvalue equations are discussed.

Neutronic design analyses for a dual-coolant blanket concept: Optimization for a fusion reactor DEMO

The generation of design specifications for a DEMO reactor, including breeding blanket (BB), vacuum vessel (VV) and magnetic field coils (MFC), requires a consistent neutronic optimization of structures between plasma and MFC. This work targets iteratively to generate these neutronic specifications for a Dual-Coolant He/Pb15.7Li breeding blanket design. The iteration process focuses on the optimization of allowable space between plasma scrapped-off-layer and VV in order to generate a MFC/VV/BB/plasma sustainable configuration with minimum global system volumes. Two VV designs have been considered: (1) a double-walled option with light-weight stiffeners and (2) a thick massive one. The optimization process also involves VV materials, looking to warrant radiation impact operational limits on the MFC. The resulting nuclear responses: peak nuclear heating in toroidal field (TF) coil, tritium breeding ratio (TBR), power amplification factor and helium production in the structural material are provided.

Stochastic resonance in a bistable system with global delay and two noises

The global time delay is introduced into a bistable system driven by two noises and a periodic signal. The signal power amplification factor η is employed to characterise stochastic resonance (SR) of the system. Numerical simulation results indicate the following. (1) For a periodic signal with low frequency (Ω), the typical behaviour of the SR is lowered monotonically by increasing the delay time τ; for moderate Ω, τ enhances the SR behaviour and then weakens it, with a critical value at which the SR is optimum. (2) Multiplicative noise intensity D and additive noise intensity α have different influences on the SR performance, viz D enhances the SR monotonically while α enforces the SR initially and then restrains it; (3) correlation intensity λ between the two noises always weakens the SR behaviour of the system.

Octalithium plumbate as breeding blanket ceramic: Neutronic performances, synthesis and partial characterization

A neutronic assessment of the performances of a helium-cooled Li8PbO6 breeding blanket (BB) for the conceptual design of a DEMO fusion reactor is given. Different BB configurations have been considered in order to minimize the amount of beryllium required for neutron multiplication, including the use of graphite as reflector material. The calculated neutronic responses: tritium breeding ratio (TBR), power deposition in TF coils and power amplification factor, indicate the feasibility of Li8PbO6 as breeding material. Furthermore, the synthesis and characterization of Li8PbO6 by X-ray phase analysis are also discussed.