Fusion Flame Research Articles

Research on video flame detection algorithm based on improved DS evidence theory

The detection and prevention of flame is of great value to protect people’s lives and property safety. At present, most flame detection methods use a single classifier and have achieved some results. However, a single classification algorithm has poor adaptability to fire detection in a variety of complex situations. Therefore, a multi-classifier fusion flame detection algorithm is proposed based on Dempster-Shafer (DS) evidence theory is proposed. In short, firstly four classifiers are used to classify the same flame feature, and the four classification results are fused to make preliminary decision. The four classifiers include support vector machine (SVM), K-nearest neighbor (KNN), decision tree (DT) and random forest (RF). Second, three complementary flame features are chosen, namely color, texture and shape changes. Finally, the preliminary decision results of the three features are fused to obtain the final classification result. It should be noted that when different classifiers have strong conflicts on the classification result of the same feature, the fusion rule of DS evidence theory will be invalid. To solve this problem, the DS evidence theory is improved. For the experiment, the public flame videos are collected to construct a data set including different complex scenes for algorithm verification, where the frame rate of the video is 15 or 24 frames/s and the resolution is 320 × 240. The experimental results show that there is a strong complementary among the results of different single classifier. The multi-classifier fusion algorithm can achieve better classification performance and robust performance than the single classifier by integrating the results of each classifier, and its average detection rate reaches 93.08%. In addition, for the changes of different environments, the proposed method has higher adaptability and stability than other state-of-art methods.

High efficient ultrahigh acceleration of plasma blocks by PW-ps laser pulses for producing fusion flames in DT and HB11 of solid state density

Ultrahigh acceleration of plasma blocks in the range of 1020 cm/s2 has been confirmed experimentally after this was long predicted as a non-thermal direct conversion of optical energy into plasma motion due to dominating nonlinear (ponderomotive) forces [1]. The use of laser pulses of more than PW power and ps or shorter duration can ignite a nuclear fusion flame in solid density deuterium tritium because the necessary energy flux of >108J/cm2 according to the theory of Chu [2] is available [3]. For the studies of the necessary velocities of the generated fusion flames above 1000 km/s the detailed processes can be analyzed by using the advanced genuine two-fluid hydrodynamic model [4] where it was surprising that the ignition of the fusion flame by the picosecond interaction needs a comparably long development in the nanosecond range before the thermal processes result in shock fronts similar to the Rakine-Hugoniot theory. For the evaluation of power generation the problem of lateral energy losses was studied by using very high pulsed magnetic fields. The recently produced 10 Kilotesla magnetic fields [5] are very promising for solutions.

Optimized boron fusion with magnetic trapping by laser driven plasma block initiation at nonlinear forced driven ultrahigh acceleration

AbstractFusion reactions of solid density boron-11 with protons after initiation of a fusion flame by very powerful picosecond laser pulses were derived for plane geometry. The problem of lateral energy losses with laser beams was solved by using spherical geometry, where however the gains are limited. The other elimination of losses now available by cylinder-axis symmetric 10 kilotesla magnetic fields is possible needing laser powers in the exawatt range. Estimations are presented by varying parameters for reducing the necessary laser pulse powers to lower values by up to a factor 100.

Efficient Generation of Fusion Flames Using PW-ps Laser Pulses for Ultrahigh Acceleration of Plasma Blocks by Nonlinear (Ponderomotive) Forces

Changing the high intensity interaction time of lasers with plasma from nanosecond duration to picoseconds results in a categorically different regime. With high intensity picoseconds laser pulses, the optical energy is converted directly into kinetic energy of plasma blocks without thermal losses, without delays by collisions, and with exclusion of most of the instabilities. Following the long known theory by the nonlinear (ponderomotive) force, the plasma receives a predicted ultrahigh acceleration in agreement with measurements by Sauerbrey. Interaction of the generated plasma blocks with solid state fusion fuel should produce a side-on ignition of a Chu-Bobin fusion flame. Using hydrodynamics with separate electron and ion fluids, detailed properties can be studied about shock generation, including the varying velocity of the flame fronts far . Results from recent computations confirm how the collective nonthermal nonlinear force driven plasma interactions are causing only marginal electron heating.

Fiber ICAN laser with exawatt-picosecond pulses for fusion without nuclear radiation problems

AbstractOne of the numerous applications of the ICAN laser using the advantage of fiber optics with chirped pulse amplification (CPA), is the scheme of side-on initiation of a nuclear fusion flame in solid density fuel with laser pulses of shorter than picosecond (ps) duration and power in the petawatt (PW) and higher range. The ICAN Fiber optics has special advantages with the potential that >900 PW spherical laser pulses may ignite the proton reaction with 11B (HB11) without the problem of dangerous radioactive radiation. Though secondary reactions can be estimated very roughly, the feasibility of a power station with the necessary energy gains can be concluded.

Application of picosecond terawatt laser pulses for fast ignition of fusion

AbstractIn this research, we presented the application of picosecond terawatt laser pulses for ultrahigh acceleration of plasma blocks for fast ignition of fusion. Ultrahigh acceleration of plasma blocks after irradiation of picosecond laser pulses of around terawatt power in the range of 1020 cm/s2was discovered by Sauerbrey (1996) as measured by Doppler effect where the laser intensity was up to about 1018W/cm2. This is several orders of magnitude higher than acceleration by irradiation based on thermal interaction of lasers has produced. This ultrahigh acceleration resulted from hydrodynamic computations at plane target interaction in 1978 at comparable conditions where the interaction was dominated by the nonlinear (generalized ponderomotive) forces where the laser energy was instantly converted into plasma motion in contrast to slow and delayed thermal collision processes. After clarifying this basic result, the application of the plasma blocks for side-on ignition of solid density or modestly compressed fusion fuel following the theory of Chu (1971) is updated in view of later discovered plasma properties and the ignition of deuterium tritium and of proton-11B appeared possible for a dozen of PW-PS laser pulses if an extremely high contrast ratio avoided relativistic self-focusing. A re-evaluation of more recent experiment confirms the acceleration by the nonlinear force, and the generation of the fusion flame with properties of Rankine-Hugoniot shocks is reported.

The internal propagation of fusion flame with the strong shock of a laser driven plasma block for advanced nuclear fuel ignition

An accelerated skin layer may be used to ignite solid state fuels. Detailed analyses were clarified by solving the hydrodynamic equations for nonlinear force driven plasma block ignition. In this paper, the complementary mechanisms are included for the advanced fuel ignition: external factors such as lasers, compression, shock waves, and sparks. The other category is created within the plasma fusion as reheating of an alpha particle, the Bremsstrahlung absorption, expansion, conduction, and shock waves generated by explosions. With the new condition for the control of shock waves, the spherical deuterium-tritium fuel density should be increased to 75 times that of the solid state. The threshold ignition energy flux density for advanced fuel ignition may be obtained using temperature equations, including the ones for the density profile obtained through the continuity equation and the expansion velocity for the r ≠ 0 layers. These thresholds are significantly reduced in comparison with the ignition thresholds at x = 0 for solid advanced fuels. The quantum correction for the collision frequency is applied in the case of the delay in ion heating. Under the shock wave condition, the spherical proton-boron and proton-lithium fuel densities should be increased to densities 120 and 180 times that of the solid state. These plasma compressions are achieved through a longer duration laser pulse or X-ray.

Shock mechanisms by ultrahigh laser accelerated plasma blocks in solid density targets for fusion

Ignition of nuclear fusion flames in solid state density fuel following Chuʼs model of 1972 is evaluated using now available plasma blocks from ultrahigh acceleration with laser pulses of picosecond (ps) duration and power up to and beyond petawatt (PW). A new numerical approach is reported where genuine two-fluid hydrodynamics is used in order to study the shock mechanism of the generated fusion flame, its propagation velocities above 1000 km / s , and fusion efficiencies for deuterium–tritium needing an energy flux of 10 8 J / cm 2 . The results of the built-up of the shock process are reported showing a basic difference between the ps and nanosecond (ns) properties. ► Nuclear fusion of solid state deuterium–tritium. ► Plasma blocks driven by nonlinear (ponderomotive) forces ignite solid fuel. ► Study the shock mechanism of the generated fusion flame. ► A new numerical approach is reported where genuine two-fluid hydrodynamics is used. ► Study of the built-up of the shock process.

In depth fusion flame spreading with a deuterium—tritium plane fuel density profile for plasma block ignition

Solid-state fuel ignition was given by Chu and Bobin according to the hydrodynamic theory at x = 0 qualitatively. A high threshold energy flux density, i.e., E* = 4.3 × 1012 J/m2, has been reached. Recently, fast ignition by employing clean petawatt—picosecond laser pulses was performed. The anomalous phenomena were observed to be based on suppression of prepulses. The accelerated plasma block was used to ignite deuterium—tritium fuel at solid-state density. The detailed analysis of the thermonuclear wave propagation was investigated. Also the fusion conditions at x ≠ 0 layers were clarified by exactly solving hydrodynamic equations for plasma block ignition. In this paper, the applied physical mechanisms are determined for nonlinear force laser driven plasma blocks, thermonuclear reaction, heat transfer, electron—ion equilibration, stopping power of alpha particles, bremsstrahlung, expansion, density dependence, and fluid dynamics. New ignition conditions may be obtained by using temperature equations, including the density profile that is obtained by the continuity equation and expansion velocity. The density is only a function of x and independent of time. The ignition energy flux density, E*t, for the x ≠ 0 layers is 1.95 × 1012 J/m2. Thus threshold ignition energy in comparison with that at x = 0 layers would be reduced to less than 50 percent.

Propagation of ion shock in solid DT target with nonlinear force-driven plasma blocks

The plasma block (piston) with pressure P 1 is generated as a result of the nonlinear (ponderomotive) force in laser–plasma interaction. The plasma block can be used for the ignition of a fusion flame front in a solid density deuterium–tritium (DT) target by compressing the fuel that creates an ion shock propagating with velocity u ion− shock in the inside of a solid DT target. The ignition is achieved by creating an ion shock during the final stages of the implosion. We estimated the effect of an ion shock in solid DT target at an early stage with no compression and at the last stage with compression, where density increases by a factor of solid-state density. According to the theoretical model, a large target with a very thin layer of fuel (high-aspect ratio target) would be ideal to obtain the very strong shocks. Results indicate that the maximum compression even by an infinitely strong single shock can never produce more than four times the initial density of DT fuel. The results reported that the threshold ignition energy in a solid DT target is reduced by a factor of 4.

Review about acceleration of plasma by nonlinear forces from picoseond laser pulses and block generated fusion flame in uncompressed fuel

AbstractIn addition to the matured “laser inertial fusion energy” with spherical compression and thermal ignition of deuterium-tritium (DT), a very new alternative for the fast ignition scheme may have now been opened by using side-on block ignition aiming beyond the DT-fusion with igniting the neutron-free reaction of proton-boron-11 (p-11B). Measurements with laser pulses of terawatt power and ps duration led to the discovery of an anomaly of interaction, if the prepulses are cut off by a factor 108(contrast ratio) to avoid relativistic self focusing in agreement with preceding computations. Applying this to petawatt (PW) pulses for Bobin-Chu conditions of side-on ignition of solid fusion fuel results after several improvements in energy gains of 10,000. This is in contrast to the impossible laser-ignition of p-11B by the usual spherical compression and thermal ignition. The side-on ignition is less than ten times only more difficult than for DT ignition. This is essentially based on the instant and direct conversion the optical laser energy by the nonlinear force into extremely high plasma acceleration. Genuine two-fluid hydrodynamic computations for DT are presented showing details how ps laser pulses generate a fusion flame in solid state density with an increase of the density in the thin flame region. Densities four times higher are produced automatically confirming a Rankine-Hugoniot shock wave process with an increasing thickness of the shock up to the nanosecond range and a shock velocity of 1500 km/s which is characteristic for these reactions.

Nonlinear force driven skin layer acceleration of plasma blocks

Since the interaction of ps laser pulses of TW power with plasmas was measured, an anomalous process was discovered which was significantly different from the usually observed numerous relativistic phenomena. This could be explained by earlier extensive numerical studies. Applications for laser fusion are reported for the generation of thick plasma blocks for ignition of fusion flames. For irradiation of spherical DT shells, the ablation efficiency may be ten times higher for the nonlinear force driven plasma blocks for volume ignition.

Plasma blocks from nonlinear force generated skin layer acceleration for ignition of a fusion flame in nearly uncompressed solid DT

It seemed to be an impossible task thirty years ago to shine a laser beam on uncompressed solid DT and to ignite a fusion flame since the necessary energy flux densities are in the range of more than 100MJ/cm 2 or corresponding deuterium ion current densities above 10 10 Amp/cm 2 which conditions were completely out of range. Since PW-ps laser pulses are available now, the situation has changed, however, by inclusion of a very sophisticated method for suppressing prepulses such that relativistic self-focusing is avoided and a purely plane or similar geometry interaction as a skin layer process appears. Out of the wide stream of research, only very special experiments with clear laser pulses confirmed this kind of interaction in theoretical and numerical agreement. This leads to the space-charge neutral plasma blocks or pistons generated by the nonlinear (ponderomotive) acceleration for producing the necessary ion current densities for the optimized ion energies of 80 keV to irradiate solid state DT. While numerous further properties have to be evaluated, the aim seems to be attractive for the very low cost fusion energy production by laser irradiation.

Fusion energy from plasma block ignition

Generation of high speed dense plasma blocks is well known from hydrodynamic theory and computations (PIC) with experimental confirmation by Badziaket al.(2005) since ps laser pulses with power above TW are available. These blocks may be used for fusion flame generation (thermonuclear propagation) in uncompressed solid state deuterium and tritium for very high gain uncomplicated operation in power stations. Hydrodynamic theory from computations from the end of 1970s to recent, genuine two fluid computations support the skin layer accelerations (SLA), by nonlinear (ponderomotive) forces as measured now in details under the uniquely selected conditions to suppress relativistic self-focusing by high contrast ratio and to keep plane geometry interaction. It is shown how the now available PW-ps laser pulses may provide the very extreme conditions for generating the fusion flames in solid state density DT.

Difference between relativistic petawatt-picosecond laser-plasma interaction and subrelativistic plasma-block generation

Some preliminary views are presented to the topic “Fast High Density Plasma Blocks Driven by Picosecond Terawatt Lasers” of the UWS-International Workshop 1–4 December 2004 in Sydney, Australia, underlining the motivation to explain the difference between the relativistic and the subrelativistic effects of ps-laser pulse interaction with plasma at powers above TW. This refers to specifically selected experimental and theoretical presentations at the workshop containing results for explaining the differences but also the important applications for studies on the fast ignitor scheme for application on nuclear fusion energy. One of the aims with relativistic proton beams is to realize conditions of spark ignition, while the subrelativistic case implies the generation of fast plasma blocks eventually with the possibility to ignite a fusion flame in uncompressed solid DT fuel for a power station with high efficiency.

Small‐Scale Interaction of Turbulence with Thermonuclear Flames in Type Ia Supernovae

Microscopic turbulence-flame interactions of thermonuclear fusion flames occurring in Type Ia supernovae were studied by means of incompressible direct numerical simulations with a highly simplified flame description. The flame is treated as a single diffusive scalar field with a nonlinear source term. It is characterized by its Prandtl number, Pr 1, and laminar flame speed, Slam. We find that if Slam ≥ u', where u' is the rms amplitude of turbulent velocity fluctuations, the local flame propagation speed does not significantly deviate from Slam even in the presence of velocity fluctuations on scales below the laminar flame thickness. This result is interpreted in the context of subgrid-scale modeling of supernova explosions and the mechanism for deflagration-detonation transitions.

Propagation velocity and structure of thermonuclear deflagration waves

Structure and propagation speeds have been determined for thermonuclear deflagration waves (fusion flames) in idealized, magnetically confined, deuterium - tritium plasmas. A one-dimensional time-dependent numerical code using multi-fluid and magnetohydrodynamic equations and detailed treatments of alpha particle energy deposition and radiative energy transfer was used. In all cases studied, deflagration waves with well defined structures form and propagate through the plasma with a speed of , where is the ion density , B is the magnetic field (T), and u is the local plasma fluid velocity.

Flow structure in near-nozzle region of gas jet flames

A flow visualization study of the near-nozzle regions of a cold jet, an attached flame, and a lifted flame of propane jet exiting a contoured nozzle with uniform velocity profile in quiescent air is presented. The observed flowfields and celerities of the coherent structures in the three cases are compared. The results show that com- bustion reactions occur away from both jet boundary and cores of coherent structures. The presence of flame retards the growth of the coherent structures and increases their celerity substantially. HE interaction of flames and flow structure in combus- tion systems has been the subject of several investiagations in the past. Many of these studies were concerned with pre- mixed flames. In recent years, however, considerable effort has been devoted to understand the flame/flow interaction in reacting plane shear layers13 and axisymmetric gas jets.47 Such studies are motivated by the necessity to understand the roles of coherent structures in the mixing rates.89 This infor- mation is needed to improve the burning characteristics of dif- fusion flames and to develop theoretical models for their prediction. A review of the uses of coherent structures was presented recently by Coles.10 An understanding of the detailed flow structure and its interaction with reaction zones is also crucial to unfold the stability mechanism of diffusion flames, including liftoff and blowout phenomena, which has been a topic of controversy in recent years.11'12 Here, we present some results from a flow visualization study in the near-nozzle region of propane gas jet flames where the flowfield is essen- tially an axisymmetric shear layer. The results not only con- firm the presence of large-scale structures in the flames but also reveal some characteristic features of their behavior in the presence of combustion. We focused our attention on the near-nozzle region in order to understand 1) the changes in flow structure of cold jets caused by the presence of a surrounding burner-attached flame, and 2) the liftoff and reattachment processes of flames.