Noise Characterization of the Microwave Plasma Torch (MPT) Source

Authors: Madrid, Yolanda1; Borer, Matthew W.2; Zhu, Chu3; Jin, Qinhan4; Hieftje, Gary M.5

Source: Applied Spectroscopy, Volume 48, Issue 8, Pages 915-1032 (August 1994) , pp. 994-1002(9)

Publisher: Society for Applied Spectroscopy

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Abstract:

Noise characteristics of emission signals from the Ar microwave plasma torch (MPT) discharge have been analyzed. Noise spectra are reported with the use of a nebulizer sample introduction system for desolvated and undesolvated aerosols, for varying analyte concentrations, and for background emission from argon and water vapor. The analytical system appears to be flicker-noise limited at frequencies below about 1 Hz. White noise was found to be dominant below 100 Hz, but discrete noise peaks were detected in the frequency region extending to 300 Hz. The noise frequency characteristics are independent of the plasma viewing position, analyte concentration, and sample introduction method but strongly dependent on the argon carrier flow rate and on the introduction of water vapor. The discrete-frequency peaks presumably have a fluid-dynamics origin, caused by flow fluctuations as argon exits the top of the torch. Noise from the measurement system and from external sources was not significant compared with the noise level observed from the plasma.

Keywords: Atomic emission spectrometry; Microwave plasma torch; Noise power spectra

Document Type: Research Article

DOI: http://dx.doi.org/10.1366/0003702944029721

Affiliations: 1: Department of Chemistry, Indiana University, Bloomington, Indiana 47405; current address: Departamento de Quimica Analitica, Universidad Complutense, Madrid, 28040, Spain 2: Department of Chemistry, Indiana University, Bloomington, Indiana 47405; current address: Lilly Research Laboratories, Lilly Corporate Center, Drop Code 0724, Indianapolis, IN 46285 3: Department of Chemistry, Indiana University, Bloomington, Indiana 47405; current address: Procter & Gamble Co. Inc., Skin Care Product Development, Sharon Woods Technical Center, HB Bldg., 11511 Reed Hartman Highway, Cincinnati, OH 45241 4: Department of Chemistry, Indiana University, Bloomington, Indiana 47405; permanent address: Department of Chemistry, Jilin University, Changchun, 130023, People's Republic of China 5: Department of Chemistry, Indiana University, Bloomington, Indiana 47405

Publication date: August 1, 1994

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