Electron cyclotron heating

The electrons are heated by external high-power, high-frequency electromagnetic waves. The frequency is usually between 2.45 and 28 GHz (the most often used frequency is 14.5 GHz) and the applied MW power is several hundreds of watts, sometimes up to several kW. The cyclotron frequency of electrons is proportional to the magnetic flux density (see Eq. 50.3), that is, depends on the time-dependent position of the electron in the plasma. Because the... 

In LDA, the electron correlations are taken into account only by a mean field approximation which utilizes the correlation enei of the uniform electron gas. In the Ce compounds where the 4f electrons are believed to be itinerant in the ground state, such as in CeSns, the topology of the Fermi surface can be described by the band structure calculated in LDA. However, the strong intra-atomic correlation effect between the 4f electrons should be considered for consistent explanations of the Fermi surface, the electronic specific heat coefficient and the cyclotron efifective mass. Beyond LDA, there are two approaches by which the correlation effect between the 4f electrons is taken into account in an explicit way. One is p-f mixing theory and the other is renormalized band theory. 

LaBi is also a semimetal. The Fermi surface is quite similar to that of LaSb (Kitazawa 1982). The cyclotron masses are in the range of 0.18wo to 0.36 Jo- The experimental electronic specific heat coefficients of LaSb and LaBi are 0.80 and 0.95 mJ/K mol, respectively. This is in good agreement with the calculated values, 0.50 and 0.85 mJ/K mol (Hasegawa 1985, Sakai et al. 1985). 

The calculated electronic specific heat coefficient of 6.2 mJ/K mol is almost the same as the experimental value of 8 mJ/K mol for LaCug. The detected masses are thus small and fall into the range of 0.076jwo to 2.50jwo, reflecting the main 4s components of Cu. Branch a is the main Fermi surface, which possess the cyclotron mass of 1.89jwo. 

On the other hand, the cyclotron masses of PrCue and CeCtig are twice and forty times larger than that of LaCug, respectively. No mass enhancement is found in NdCu and SmCug, as shown in fig. 98. Here, the electronic specific heat coefficients of PrCue and... 

Alternative approaches consist in heat extraction by means of thermal analysis, thermal volatilisation and (laser) desorption techniques, or pyrolysis. In most cases mass spectrometric detection modes are used. Early MS work has focused on thermal desorption of the additives from the bulk polymer, followed by electron impact ionisation (El) [98,100], Cl [100,107] and field ionisation (FI) [100]. These methods are limited in that the polymer additives must be both stable and volatile at the higher temperatures, which is not always the case since many additives are thermally labile. More recently, soft ionisation methods have been applied to the analysis of additives from bulk polymeric material. These ionisation methods include FAB [100] and LD [97,108], which may provide qualitative information with minimal sample pretreatment. A comparison with FAB [97] has shown that LD Fourier transform ion cyclotron resonance (LD-FTTCR) is superior for polymer additive identification by giving less molecular ion fragmentation. While PyGC-MS is a much-used tool for the analysis of rubber compounds (both for the characterisation of the polymer and additives), as shown in Section 2.2, its usefulness for the in situ in-polymer additive analysis is equally acknowledged. 

Concerning the first field of application, the kinetics and equilibrium constants for several halide transfer reactions (equation 1) were measured in a pulsed electron high pressure mass spectrometer (HPMS)4 or in a Fourier transform ion cyclotron resonance mass spectrometer (FT-ICR)5. From measurements of equilibrium constants performed at different temperatures, experimental values were obtained for the thermochemical quantities AG°, AH° and AS° for the reaction of equation 1. The heat of formation (AH°) of any carbocation of interest, R+, was then calculated from the AH0 of reaction and the AH° values of the other species (RC1, R Cl and R +) involved. 

Prom the temperature dependence of the dHvA (or SdH) oscillations it is possible to extract the effective cyclotron mass (see Sect. 3.1). Comparisons of the mass obtained by these measurements with values from band-structure calculations, cyclotron resonance and specific-heat measurements are sometimes inconsistent. Whether strong electron-electron or electron-phonon interactions play the dominant role for this discrepancy is still under considerable debate and further studies have to deal with this question. Chapter 4 will review the present-day knowledge of the highly active field of the fermiology of organic superconductors . 

Ions are produced by electron impact (from a heated filament) on a neutral sample at low pressure (10-7 torr). The ions enter the ICR cell under the influence of external electric and magnetic fields, which constrain them to move in circular orbits with a cyclotron frequency applied magnetic field H ... 

The sample inlet is constituted of a heated fused silica capillary, which is maintained at approximately 200 "C and is encased in a flexible tube. The ion source, in the case of electronic ionization, is composed of electrically heated metallic filaments. Mass analyzers, separating the analytes, include time-of-flight (TOF), linear quadmpole (Q), linear quadrupole ion trap (LIT), quadmpole ion trap (QIT), Fourier transform ion cyclotron resonance (FT-ICR), etc. These detectors differ in their capacity to treat ion beams in a continuous or pulsed (TOF). Quadmpole mass analyzers stabilize and destabilize the ion paths with an oscillating electrical field. A triple quad is more recent technology and consists of three quadmpole stages. Quadmpole ion traps will sequentially eject ions that have been trapped in a ring electrode between two endcap electrodes. 

Another important problem is the relation between heavy-electron masses as obtained from measurement of the specific heat -y-value and from the dHvA experiments. For example, in CeCug the former shows a strong field dependence, Stewart et al. (1988) whereas the latter seems to be field independent (Reinders et al. 1986). For CeB, however, both the thermal and the cyclotron masses show pronounced field dependences (Joss et al. 1987). 

As the thermal coupling between the electron and ion fluids is relatively loose and losses through the electron fluid can be high (Doyle et al. 2007) ECRH is not the most efficient way of heating the ions. This task can be more efficiently done by waves resonating in the ion cyclotron... 

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