Ion temperature measurement

Fig. 8.5. Comparison between the central ion temperature measured by the X-ray spectrometer and the ion temperature by charge exchange recombination spectroscopy (CXRS) [3]...

The above discussion is presented merely to give an idea of the types of EUV detectors and their applications in use on present fusion plasma experiments. It is by no means an exhaustive list of possibilities. Indeed, several different detectors are in use or being planned in future experiments. Resistive anode encoders will probably see more use in fusion experiments as they become commercially available. However, the low count rates available ( 10 to 10 sec-1) will result in these detectors being used mostly for line profile studies (e.g., ion temperature measurements via Doppler broadening measurements). Intensified CCD arrays (back-illuminated or otherwise), vidicon or CID systems, lens-coupled intensifiers, and anode detectors have all seen some use on tokamak experiments or are planned for the near future, but have not been widely used as yet. However, in terms of availability, pixel format, dynamic range, insensitivity to magnetic fields, compact package, and moderate cost, the IPDA remains the most versatile multichannel EUV detector for plasma spectroscopy. 

This frequency is a measure of the vibration rate of the electrons relative to the ions which are considered stationary. Eor tme plasma behavior, plasma frequency, COp, must exceed the particle-coUision rate, This plays a central role in the interactions of electromagnetic waves with plasmas. The frequencies of electron plasma waves depend on the plasma frequency and the thermal electron velocity. They propagate in plasmas because the presence of the plasma oscillation at any one point is communicated to nearby regions by the thermal motion. The frequencies of ion plasma waves, also called ion acoustic or plasma sound waves, depend on the electron and ion temperatures as well as on the ion mass. Both electron and ion waves, ie, electrostatic waves, are longitudinal in nature that is, they consist of compressions and rarefactions (areas of lower density, eg, the area between two compression waves) along the direction of motion. 

In the plasma, the sample is vaporized and chemical bonds are effectively broken resulting in free atoms and ions. Temperatures of 5000-9000 K have been measured in the plasma compared to typical temperatures of 2000-3000 K in flames and graphite furnaces. 

The thermochemical determinations involving ions obtained via ES, described in this work, provide an illustration of opportunities presented by the ES method. However, these are only the beginning of what we believe should become an important area in gas-phase ion chemistry. The ion equilibria measurements, so far performed in our laboratory, were restricted by the limited upper temperature (T < 500 K). This restriction was due to the cryopumping used and could be easily overcome and the temperature extended upwards by -200 K by using conventional pumping. 

Adsorption measurements were made by batch technique at room temperature (25 3°C). Known amounts of tannin resin were placed in 250 mL erlenmeyer flasks containing 100 mL of metal ion solution of known concentration and were stirred for a given time period. The solutions were then filtered, centrifuged and the concentrations of metal ions were measured by AAS. The difference in the metal ion (Pb + and Ztf+) content before and after adsorption represented the amount of Pb and Zn adsorbed by new resin. 

Dickson et al. [5], calculated the Gibbs function for the ionization of the bisulfate ion by measurement of cell potentials in the temperature range from 50° to 250°C. They found that the Gibbs function could be represented by the equation... 

The latter authors used anode and cathode symmetrical cells in EIS analysis in order to simplify the complication that often arises from asymmetrical half-cells so that the contributions from anode/ electrolyte and cathode/electrolyte interfaces could be isolated, and consequently, the temperature-dependences of these components could be established. This is an extension of their earlier work, in which the overall impedances of full lithium ion cells were studied and Ret was identified as the controlling factor. As Figure 68 shows, for each of the two interfaces, Ra dominates the overall impedance in the symmetrical cells as in a full lithium ion cell, indicating that, even at room temperature, the electrodic reaction kinetics at both the cathode and anode surfaces dictate the overall lithium ion chemistry. At lower temperature, this determining role of Ra becomes more pronounced, as Figure 69c shows, in which relative resistance , defined as the ratio of a certain resistance at a specific temperature to that at 20 °C, is used to compare the temperature-dependences of bulk resistance (i b), surface layer resistance Rsi), and i ct- For the convenience of comparison, the temperature-dependence of the ion conductivity measured for the bulk electrolyte is also included in Figure 69 as a benchmark. Apparently, both and Rsi vary with temperature at a similar pace to what ion conductivity adopts, as expected, but a significant deviation was observed in the temperature dependence of R below —10 °C. Thus, one... 

If a S> 1, collective effects play an important role and the light scattering is no longer caused by individual electrons but by electron density fluctuations 280), Jn this case the spectrum shows a central line at Xq and two narrow lines located symmetrically about Xq, at a distance governed by the electron plasma frequency. The linewidth is smaller than in the case X < 1 and is determined rather by the thermal motion of the ions, not that of the electrons. The line shape depends on the ratio of electron to ion temperatures. Therefore, a measurement of the shape and width of this central line allows, under certain assumptions, a direct determination of the ion temperature. 

This fact has been used to measure electron and ion temperatures in a theta-pinch plasma 28i), and a dense plasma (/tg = 10 cm ) produced in a carbon arc 282). Both experiments employed pulsed ruby lasers as light sources. 

Sulfur isotope temperatures from ore deposits often have been controversial one of the reasons are strong " S zonations in sulfide minerals that have been observed by laser probe and ion probe measurements (McKibben and Riciputi 1998). 

The kinetic parameters of Zn(II)/Zn(Hg) electrode reaction in aqueous solution containing perchlorate, nitrate, chloride, and bromide ions were measured at different temperatures (5-50°C) [35]. The Arrhenius activation energy and thermodynamic parameters for the Zn(II)/Zn(Hg) system... 

If the activation energies of surface diffusion vary over a wide range from one element to another and from one surface to another, the diffusivity, or the pre-exponential factor, D0, does not. Within the very limited accuracy of the field ion microscope measurements, usually no better than one order of magnitude because of the narrow temperature range within which a measurement can be conveniently done, all measured values of D0 are consistent with eq. (4.22) by taking AS = 0, and v0 = kTIh where h is the Planck constant, or D0 are about a few 10-3 cm2/s. This has been pointed out repeatedly by the author126 since there is... 

Adatom diffusion, at least under the low temperature of field ion microscope measurements, almost always follows the direction of the surface channels. Thus adatoms on the W (112) and Rh (110) surfaces diffuse in one direction along the closely packed atomic rows of the surface channels. Such one-dimensional surface channel structures and random walks can be directly seen in the field ion images, and thus the diffusion anisotropy is observed directly through FIM images. Unfortunately, for smoother surfaces such as the W (110) and the fee (111), no atomic or surface channel structures can be seen in field ion images. But even in such cases, diffusion anisotropy can be established through a measurement of the two-dimensional displacement distributions, as discussed in the last section. Because of the anisotropy of a surface channel structure, the mean square displacements along any two directions will be different. In fact this is how diffusion anisotropy on the W (110) surface was initially found in an FIM observation.120... 

---