Sparks radio-frequency

Spark Source Mass Spectrometry (SSMS) is a method of trace level analysis—less than 1 part per million atomic (ppma)—in which a solid material, in the form of two conducting electrodes, is vaporized and ionized by a high-voltage radio frequency spark in vacuum. The ions produced from the sample electrodes are accelerated into a mass spectrometer, separated according to their mass-to-charge ratio, and collected for qualitative identification and quantitative analysis. 

Volatile or volatilizable compounds may be introduced into the spectrometer via a pinhole aperture or molecular leak which allows a steady stream of sample molecules into the ionization area. Non-volatile or thermally labile samples are introduced directly by means of an electrically heated probe inserted through a vacuum lock. Numerous methods of sample ionization are available of which the most important are electron impact (El), chemical ionization (CY), field ionization (FI), field desorption (FD), fast atom bombardment (FAB), and radio-frequency spark discharge. 

The cross-sectional view of an inductively coupled plasma burner in Figure 21-12 shows two turns of a 27- or 41-MHz induction coil wrapped around the upper opening of the quartz apparatus. High-purity Ar gas is fed through the plasma gas inlet. After a spark from a Tesla coil ionizes Ar, free electrons are accelerated by the radio-frequency field. Electrons collide with atoms and transfer their energy to the entire gas. maintaining a temperature of 6 000 to 10 000 K. The quartz torch is protected from overheating by Ar coolant gas. 

Production of Ions. Several methods are used (11 by bombardment with electrons from a heated filament (2 by application of a strong electrostatic field (field ionization, field desorption) Ot by reaction with an ionized reagent gas (chemical ionization) (4 by direct emission of ions from a solid sample that is deposited on a heated filament (surface ionization) (SI by vaporization from a crucible and subsequent electron bombardment (e.g.. Knudsen cell for high-lcmperalure sludies id solids and (6) by radio-frequency spark bomhardmenl of sample fur parts-per-biliion (ppb) elemental analysis of solids as encountered in metallurgical, semiconductor, ceramics, and geological studies. Ions also are produced by photoion izution and laser ionizalion. 

Primary expls (initiating) are used to start the train of reactions which results in the deton of secondary HE s or of the functioning of ammo. These expls are the most sensitive of all chemical components in military ammo, hence, the most hazardous. Primary expls can be ignited by an elec heater or spark, heat from mechanical friction, a free flame, or by an RF (radio frequency) signal. The ideal primary expl is a single compd, since this affords greatest control of its characteristics. Unfortunately, such a compd is not always available so that mixts must usually be used... 

A typical EDL consists of a hermetically sealed quartz envelope containing an inert gas (Ar) at very low pressure and the element or salt of the target element. In order to ionize the inert gas, micro-wave radiation (approximately 100 MHz) or, as is usually the case, radio frequency (RF) radiation (from 100 kHz to 100 MHz) is applied. Commercially available RF EDLs have a built-in starter, run at 27 MHz, which provides a high voltage spark to ionize the filler gas to initiate the discharge. 

In spark sources, electrical discharges are used to desorb and ionize the analytes from solid samples [98]. As shown in Figure 1.42, this source consists of a vacuum chamber in which two electrodes are mounted. A pulsed 1 MHz radio-frequency (RF) voltage of several kilovolts is applied in short pulses across a small gap between these two electrodes and produces electrical discharges. If the sample is a metal it can serve as one of the two electrodes, otherwise it can be mixed with graphite and placed in a cup-shaped electrode. 

Figure 3. Radio Frequency Spark Source. Reproduced with permission from Ref. 11 Copyright 1965 Interscience Publishers.

Spark source SSMS Radio-frequency electric spark Double-focusing... 

Baselyan, E.M., Raizer, Yu.E (1997), Spark Discharge, Moscow Institute of Physics and Technology, Moscow. Bashkirov, Y.A., Medvedev, S.A. (1968), Application of a Radio-Frequency Electrodeless Discharge for Synthesis of Niobium-Vanadium Intermetallic Compounds, in Low Temperature Plasma Generators, p. 501, Energia (Energy), Moscow. 

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