Plasma radiation

Dry cleaning, also called gas-phase cleaning, is based on excitation energy such as plasma, radiation or thermal excitation. This section will concentrate on the wet processes, the area where ozone is of interest. 

Single-component irradiations have provided useful information concerning certain projectile/surface interactions which contribute to plasma contaminant release and surface damage and erosion, but they cannot yield any information about interactive (synergistic) surface effects. These arise when two or more plasma radiation components interact simulaneously with surfaces, together producing plasma contaminant release and/or surface erosion either larger or smaller than that expected from a simple summation of the effects caused by the individual radiation components. Interactive effects can also occur after sequential irradiations. 

In addition to thermal desorption, gas desorption has been found to result from electron, ion and photon bombardment of surfaces. Therefore, simultaneous particle and photon bombardments can be expected to alter desorption rates, as well as the nature and charge distribution of the desorbed species. Furthermore, simultaneous bombardment of a surface by neutrons and ions could affect diffusion processes, e.g., by radiation-induced segregation. In turn, desorption processes can be influenced by altering the diffusion of species from the bulk to the surface. The type, energy, and angular distribution of particles expected to strike neutral beam injector dump areas (such areas can represent 1/9 of total first wall area) can cause synergistic effects on gas desorption which can be quite different from those expected from the interaction of plasma radiations with the first wall. 

Figure 3. Photo scanning of plasma radiation intensity at 44 kHz frequency during one period of current. Corresponding graph of current variation is shown below. Scheme of electrodes positioning is shown on the right, r - distance between electrodes, I - current t -time.

Fig. 3.10. Normalized ELM particle loss (AArELM/Artot, where Ntot is the total particle content) versus ELM frequency (/elm) for JET discharges with plasma current /p = 2.5 MA, toroidal field Bt = 2.4-2.7 T, input power Pinput = 14-17 MW and medium (S = 0.3) and high (<5 = 0.5) triangularity. Two discharges (at medium and high S) in which Argon has been injected to increase the level of plasma radiation are shown for comparison. Lines are to guide the eye [16]...

Fig. 13.4. Example of a discharge with silicon evaporation from a test limiter made of Si-doped CFC (SEP NS31). The figure shows the time traces of the local silicon fluxes from the limiter (Si/D), the line-integrated radiation of Si XII emission, the local surface temperature of the limiter measured at the location of maximal power loading, the energy loss due to plasma radiation (Prad), the radiation level 7 = Pia.d/P, the diamagnetic energy Fdia and the convective power on the test limiter P — Praa, respectively...

As a future plan, we would like to explore a new field where atomic and nuclear physics are related in plasmas and systemize them. Extensions of our research to non-equilibrium, non-thermal and non-isotropic plasma, especially polarization spectroscopy are considered. We would like to develop quantum molecular dynamics for plasma-wall interactions, plasma radiation science, high-density plasma states, and atomic processes in high fields. These... 

Table 5.1 Comparison Plasma, Radiation, and Parylene Pol5merizations...

Class 4 Average power above 0.5 W Pulsed lasers Exceeds 0.125 J within 0.25 sec Direct and specular reflection viewing hazards Diffuse reflection may present a hazard May pose a fire hazard May generate plasma radiation... 

The object of modeling plasma chemistry is to relate the external variables, such as discharge power or current, applied voltage, gas composition, pressure, temperature, discharge geometry, etc., which one can adjust in a laboratory device, to properties that are of interest, such as electron and ion densities, densities of excited or radical species, plasma radiation characteristics, etc. The electron impact processes in an ionized gas drive the plasma chemistry. In... 

Plasma in CTE conditions cannot be practically realized in the laboratory. Nevertheless, thermal plasmas sometimes are modeled this way for simplicity. To imagine CTE plasma, one should consider so large a plasma voltrme that its central part is homogeneous and not serrsitive to botmdaries. Electromagnetic plasma radiation can be cortsidered in this case as that of a blackbody with the plasma temperatrrre. 

T. Thermal plasma radiation cannot exceed that of the absolute blackbody at the plasma temperature. Therefore, fixing the required spectral emission interval determines the required values of the thermal plasma temperature. Specifically, for effective emission in UV and VUV spectral ranges, the thermal plasma temperature should be in the interval from 2 to 15 eV Plasma in high-brightness light sources is usually characterized by volume... 

Lasers are another source of excitation radiation used in fluorescence detection systems. The high-directional output of a laser maximizes the fraction of total output that can be easily focused down to a spot size compatible with the dimensions of CE detection cells. The output of a laser is also typically monochromatic, or a discrete set of spectrally narrow lines. This type of output makes it relatively easy to filter out low-level incoherent plasma radiation and undesired emission lines without greatly diminishing the overall output power. In addition, many lasers provide flexibility in terms of pulse width and repetition rate, which allows one to optimize excitation with respect to analyte photostability. 

Figure 10.4 shows one of the Dy203 lamps in operation. The strong blue and UV absorption of the arc tube body material filters some of the plasma radiation and... 

However, an O2 plasma is not efficient for treating PTFE. One reason for this is also shown in Figure 11, the 130.5nm emission from an O2 plasma is not strongly absorbed by PTFE and does not cause decomposition of that polymer. It is necessary to use a plasma gas that radiates at a shorter wavelength than O2. For example, an H2 containing plasma radiates at 121.Snm. This radiation will be absorbed by the surface of the FIFE and will break the surface bonds. Also, the H can abstract the surface fluorine to form HF and eiq>ose carbon free-radicals to further attack by other species in the boundary layer. 

Locator Designator (G/VLLD) May pose a fire hazard. May generate plasma radiation. EXTREMELY HIGH... 

In large plasmas the lower harmonics of the cyclotron frequency are reabsorbed before they escape, and the synchrotron losses are not as large as in Eq. (45). For harmonics lower than a critical harmonic m, the plasma radiates like a black body from its surface higher harmonics have lower amplitude but are not reabsorbed. An early estimate by Dawson for a p-B ... 

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