Plasma sources Microwave plasmas

Microwave discharges at pressures below 1 Pa witli low collision frequencies can be generated in tlie presence of a magnetic field B where tlie electrons rotate witli tlie electron cyclotron frequency. In a magnetic field of 875 G tlie rotational motion of tlie electrons is in resonance witli tlie microwaves of 2.45 GHz. In such low-pressure electron cyclotron resonance plasma sources collisions between tlie atoms, molecules and ions are reduced and the fonnation of unwanted particles in tlie plasma volume ( dusty plasma ) is largely avoided. 

Korzec D, Werner F, Winter R and Engemann J 1996 Scaiing of microwave siot antenna (SLAN) a concept for efficient piasma generation Plasma Sources Sol. Technol. 5 216-34... 

In a typical MIP-MS instrument, the ICP portion is replaced with one of a variety of microwave discharge sources, usually a fairly standardised (modified) Beenakker cavity connected to a microwave generator. The analytical MIP at intermediate power (<500 W) is a small and quiet plasma source compared with the ICP. The mass spectrometer needs no major modifications for it to be interfaced with the MIP. With MIP used as a spectroscopic radiation source, typically consisting of a capillary (1mm i.d.), a power of 30-50 W and a gas flow below 1 L min 1, multi-element determinations are possible. By applying electrodeposition on graphite electrodes, ultratrace element determinations are within reach, e.g. pg amounts of Hg. 

E.H. Evans, J.J. Giglio, T.M. Castillano and J.A. Caruso, Inductively Coupled and Microwave Induced Plasma Sources for Mass Spectrometry, The Royal Society of Chemistry, Cambridge (1995). 

Baeva, M., Gier, H., Pott, A. et al. (2002) Pulsed microwave discharge at atmospheric pressure for NOx decomposition, Plasma Sources Sci. Technol. 11, 1-9. 

In contrast to the d.c. or microwave plasma apparatus, the sample environment produced by these directed beam sources has been reasonably well characterized. Studies of Kaufman source operation (Sharp et al., 1979) have established that H beams are typically composed of mixtures of H+ and H2+ ions and a roughly equal mixture of energetic neutrals. The ion energy spectrum of such a source is fairly sharply peaked at the maximum energy at low acceleration voltages (150-500 eV) but spreads out considerably if the source is operated at voltages above 1000V. 

Other Flame-like Plasma Sources 4.5.1 Microwave Plasmas... 

Among the plasma sources that have been used for analytical measurements include the inductively coupled argon plasma (ICP), direct current argon plasma (DCP) and microwave induced heUum plasma (MIP). The instrumentation and I rformance of the more popular ICP source have been discussed by Barnes More rwently, Thompson and Walsh have published a book dealing with the practical aspects of ICP. 

Further designs of ion sources applied in plasma spectroscopy such as electrodeless microwave induced plasmas (MIPs) operating in a noble gas atmosphere at low power (mostly below 200 W) or capacitively coupled microwave plasma using Ar, He or N2 the as plasma gas (at 400-800 W) were described in detail by Broekaert.33 Microwave plasmas produced by a magnetron are operated at 1-5 GHz. Their special application fields for selected elements and/or element species are based (due to the low power applied) in atomic emission spectrometry.33... 

Recently, Hieftje et al.15-16 equipped a small double-focusing mass spectrograph built in house with Mattauch-Herzog geometry with several ion sources (such as glow discharge, an inductively coupled plasma ion source or a microwave plasma torch) and a novel array detector for simultaneous ion detection. 

Inductively Coupled and Microwave Induced Plasma Sources for Mass Spectrometry 4 Industrial Analysis with Vibrational Spectroscopy 5 Ionization Methods in Organic Mass Spectrometry 6 Quantitative Millimetre Wavelength Spectrometry 7 Glow Discharge Optical Emission Spectroscopy A Practical Guide 8 Chemometrics in Analytical Spectroscopy, 2nd Edition 9 Raman Spectroscopy in Archaeology and Art History 10 Basic Chemometric Techniques in Atomic Spectroscopy... 

The electron source of the PIMMS is an argon plasma. Inside the plasma chamber the gas is ionized by a 2.45 GHz microwave field, ignited by an electric spark. In the plasma chamber free electrons are created, that are accelerated by a static electric field for impact ionization of the sample gas atoms. The layout of the plasma chamber has to incorporate both the fluidic and the electrostatic requirements. On the one hand the gas apertures of the chamber must have the appropriate dimensions to assure that the gas flow out of the chamber is low. On the other hand the geometry must be such that most of the electrons are generated close to the outlet of the chamber and can be extracted through this small aperture. Electrons should be generated close to the acceleration field, which intrudes the chamber only to a small depth. 

Pack et al. described the coupling of GC separations to TOF-MS by utilization of a microwave plasma torch (MPT) [50]. This low-power microwave plasma source has exhibited excellent limits of detection for halogenated species. When such species are separated by GC, the simultaneous capabilities of TOF-MS allowed the monitoring of 12C and 35C1 simultaneously, thereby facilitating the determination of empirical formulas. Presumably, ion chromatographic separations, FIA systems, and other separations might also benefit from the capabilities of TOF-MS. 

Most chemical agents contain specific elements in common. G and V agents all contain phosphoms and blister agents, like the mustards, contain sulfur or nitrogen. The combustion of these materials yields excited atoms that emit light characteristic of these elements. The emissions are viewed through an interference filter by a photodetector. As an alternative to a flame, low-powered, inductively coupled (or microwave) plasmas have been used as emission sources. These sources have been combined with... 

RF- and ion-beam assisted PLD PLD chamber equipped with RF or microwave plasma source or ion beam source to enhance the composition of particular film components such as N or O to grow in-plane aligned films on polycrystalline substrates, and to grow nanostructures [128]... 

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