Excitation sources alternating current

The examples we saw are for L C circuits supplied from a direct current source. What happens when an L C circuit is excited by an alternating current source Once again, oscillatory response will be present. The oscillatory waveform superimposes on the fundamental waveform until the damping forces sufficiently attenuate the oscillations. At this point, the system returns to normal operation. In a power system characterized by low resistance and high values of L and C, the effects would be more damaging than if the system were to have high resistance and low L and C because the natural frequencies are high when the values of L and C are low. The... 

During the 1980s, a rapidly increasing number of methods have been published for mercury determination by AES (often called OES = optical emission spectrometry) after excitation/ionization in a gas plasma, usually argon. The plasma source most frequently used is an ICP, but also other kinds of plasma sources are used, e.g. alternating current plasma (ACP), direct current plasma (DCP), and microwave-induced plasma (MIP). AES has a wide multi-element capability the linear range extends over 4-6 orders of magnitude. 

A number of electrical excitation-sources are available for emission spectroscopy. In most commercial spectrochemical instruments, more than one excitation source is contained in a single power-supply cabinet a typical combination may include a spark, a direct-current arc, and an alternating-current arc. A list of the various electrical excitation-sources, some of their characteristics, their approximate cost and the types of samples generally required is given in Table 11.1. Because of the actual or potential widespread use in emission spectroscopy, only the arc, spark, and inductively coupled plasma discharges will be described here in detail. 

NEXAFS spectroscopy basically does not require the most sophisticated apparatus to be performed but a source of tunable radiation as that dispensed by a photon factory or synchrotron plant. The experimental station for the study of macromolecular materials requires a UHV system and a detector apparatus for counting the emitted electrons. The primary process in NEXAFS is the core electron excitation into an appropriate final state empty molecular orbital. After excitation, the whole system undergoes relaxation and this can occur through two main decay processes secondary or Auger electron emission and fluorescence emission. Mostly, the detector for NEXAFS uses a simple channeltron tuned for a specific Auger energy or tuned to collect the whole secondary electrons resulting from the relaxation process fluorescence detector are also relatively common alternatively, for sample insulator the measurement of the drain current from the conductor sample holder is often measured examples are displayed in Fig. 4.4. Measurements can be performed on gas, solid and recently liquid state [3]. 

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