Ionization probes

Figure 4.21 Schematic of an atmospheric-pressure-chemical-ionization probe. From applications literature published by Micromass UK Ltd, Manchester, UK, and reproduced with permission.

The ionizing electrode method, also called the radioactive or ionizing probe, requires a radioactive source to ionize the gas gap and a high-... 

In fuel-lean premixed burners, the primary air ratio determines the quality of combustion changing the rotational speed of the flue gas fan has also some influence. An ionization probe is used to determine the quality of combustion. A dedicated system, developed at GWI, provides accurate detection and analysis of the ionization signal. This includes a metering device, which is provided with a rectangular supply voltage, thus warranting very accurate ionization signals. 

To investigate these problems, Brossard et al (Ref 13) analyzed data on cylindri-cally diverging detonation waves in various propane/C>2/N2 mixtures contained in divergent sectors. Detonation was initiated with an exploding wire located in the apex of the sector angle. The wave velocity was measured with ionization probes, and the wave structure was observed by means of streak-schlieren and soot-track techniques... 

A 300-Kvolt X-ray FEXITRON unit was used, the flash duration being 0.12/isec and t he opt ical magnification 1.1. Ionization probes pi aced on t he axis of t he chge wer e... 

A.Ya. Apin L.G. Bolkhovitinov, Dokl-AkadN 124, 338-39 (1959) CA 55, 6865 (1961) (Measurement of the rate of combstn of smokeless proplnt grains directly in detonation wave by using the ionizing probe method. The combstn rate was directly proportional to pressure and at 60000kg/sq cm, the rate for NB proplnt was 200- 300m/sec) 58) A.N. 

The POT is a discrete measurement technique using pin type ionization probes as sensors for detecting the arrival time of detonation wave at pre-determined points and measuring propagation time between these points with the help of a high-speed oscilloscope. The schematic of instrumentation set-up is shown in Figure 3.17. 

Ionization probes These probes are called ionization probes because they get shorted due to the ionization of detonation products. The insulated copper wires of 0.8 mm dia and length 600 mm are taken and twisted together at the center followed by cutting of the twisted ends in the same plane (Figure 3.18a). These are usually inserted and anchored in the test sample to about 2-3 mm depth. 

Sulfur probe An ionization probe coated with a thin layer of molten sulfur on its conducting tip is used for measurement of shock velocity (Figure 3.18b). This is a special probe which is used in the conducting medium (Sulfur is non-conducting at ambient pressure but becomes conducting at shock pressures as its resistance decreases drastically at such pressures). This property of sulfur allows the R-C network to generate an electrical pulse at the time of arrival of shock wave. 

Figure 22-19 (a) Atmospheric pressure chemical ionization interface between a liquid chromatography column and a mass spectrometer. A fine aerosol Is produced by the nebulizing gas flow and the heater. The electric discharge from the corona needle creates gaseous ions from the analyte. [Adapted from E. C. Huang, T. Wachs, J. J. Conboy, and J. D. Henion, Atmospheric Pressure Ionization Mass Spectrometry," Anal. Chem. 1990,62,713A ] (b) Atmospheric pressure chemical ionization probe. [Courtesy Shimadzu Scientific Instruments, Columbia, MD.J... 

E—Ionization Probe Location F—Explosive Charge G—Tube H—Bottom Closure. Inner Diameter516.3mm, Outer Diameter55 50.8mm. Distance From Igniter/Explo-sive Interface To Bottom Closure=295.4mm)... 

Engel, V. and Metiu, H. (1989). The study of Nal predissociation with pump-probe femtosecond laser pulses The use of an ionizing probe pulse to obtain more detailed dynamic information, Chem. Phys. Lett. 155, 77-82. 

When combined with tandem mass spectrometry, capable of selectively detecting a few analytes from the many that could be present, this approach provides for unsurpassed analytical selectivity for difficult chemical problems such as the study of drug—receptor binding [36] or the separation of complex mixtures of proteins or peptides [37]. The detection approach can be implemented in either on- or off-line formats. Alternatively, the purified antibody can be immobilized on a matrix-assisted laser-desorption ionization probe to allow direct application and characterization of a liquid sample containing the target molecule [38]. 

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