Power flux

Microwaves may be used to ionize gases when sufficient power is apphed, but only through the intermediate process of classical acceleration of plasma electrons. The electrons must have energy values exceeding the ioniza tion potential of molecules in the gas (see Plasma technology). Ionizing radiation exhibits more biological-effect potential whatever the power flux levels (2). 

The solar spectrum corresponds roughly to the radiation of a black body at the temperature 5750 K. If we denote the photon flux in the wavelength interval from A to (A 4- dA) (in photons/m2 s) as /(A), the total solar power flux (in W/m2) is given as ... 

The power flux corrected for atmospheric absorptions equals about 1 kW/m2 if the Sun stands at zenith and the sky is clear. This situation is customarily labelled AM 1 (one standard air mass). 

Thus, an event causing h 10-18 at 3kFIz (whatever the source distance) produces a power flux of 2.7MW/m2. Even so, the amount of energy deposited in any amount of matter will be extremely small. 

Power flux is the scalar product of displacement velocity and traction. In an isotropic medium with no viscosity these are parallel, and the mean power flow is... 

Human civilization deals with power fluxes in a wide range of magnitudes from global to local. At personal level, the flows for computer users would seem small but they cannot be ignored (Table 1). 

Power Flux Watts Fraction to absorbed solar radiation... 

Fig. 3.6. Divertor surface temperature in the JET tokamak during a discharge with Type I ELMs [17]. The origin for the time axis is taken as the beginning of the ELM power flux (seen at the inner divertor for this ELM). The surface temperature of the inner divertor rises by more than 500° C in less than 200 ps following the ELM event...

Fig. 3.21. Time evolution of the surface temperature of the outer divertor target and the deduced power flux, for typical low density ELMy H-mode conditions in JET (ne,ped = 5.2 1019m 3, Te,pea = 1650eV). For inter-machine comparisons, the duration of the ELM power pulse is characterized by the rise time of the surface temperature during the ELM (tiIrLM), as illustrated in the figure [16,40]...

As shown in Figs. 3.21 and 3.22, the temporal evolution of the power flux during Type I ELMs is much more complicated than what is described in a simple way by In particular, the power flux during an ELM is substantially different from a square waveform in time with duration as it... 

Fig. 3.25. Heat flux histories following an ELM of 1MJ/m2 with a power flux triangular waveform (curve 1) with ramp-up and ramp-down phases lasting 300 ds each on a 10mm thick W target under an inter-ELM power flux of 10MWm 2. Curves. (1) incident heat flux load (2) conducted heat flux into the material (3) heat flux spent in melting of the material (the evaporation and black-body radiation heat fluxes are comparatively small and not shown). Curve (4) shows the surface target temperature and (5) shows the temperature of the melt layer. Curve (6) shows the vaporized thickness (amplified of a factor of 1000) and (7) the melt layer assuming that no losses of molten material occur during the ELM [3]...

Divertor erosion/co-deposition estimates in ITER are based on the RE-DEP/WBC code package [98-100]. Power fluxes as well as plasma particle fluxes (i.e., D-T ions and atoms, and impurities such as helium and carbon)... 

According to Steinfeld [13], there is a temperature, Toptimum, for which the TCWSC efficiency is maximum. Assuming a uniform power-flux distribution, Toptimum can be determined from the following implicit equation ... 

Here, intensity means the time average of the power flux per unit area, as follows from the theory of electrodynamics 2) 7 = 5 = E x 5 1 and ... 

---