Thomas Levine

US Patent:

55588360, Sep 24, 1996

Filed:

Oct 3, 1994

Appl. No.:

8/316905

Inventors:

David P. Rounbehler - Bedford MA
Dirk Appel - Salem MA
Daniel A. Dussault - Newburyport MA
Thomas M. Levine - Lee NH
Jonathan E. Bosworth - Acton MA

Assignee:

Thermedics Detection Inc. - Woburn MA

International Classification:

G01N 2115

US Classification:

422 91

Abstract:

A detection system for detecting the emission (i. e. , the fluorescence or phosphorescence) from a contaminant contained in a sample gas. In order to keep the optics of the system clean and maintain a high signal-to-noise ratio in the detected signal, the detection system contains a housing separated into illumination and sample chambers by an aperture-containing partition. A sample inlet port is connected to the sample chamber, and a purge inlet port is connected to the illumination chamber to direct the purge and sample gasses into their respective chambers. A vacuum system is connected to a vacuum port on the sample chamber to simultaneously draw the sample and purge gasses into their chambers through the inlet ports; the purge gas is then drawn through the aperture and into the sample chamber. Finally, both gasses are drawn out of the sample chamber through the vacuum port. Thus, the vacuum provides a flow of sample gas into the sample chamber, and a flow of purge gas into the illumination chamber to reduce contact between the sample gas and a portion of the optics, thereby keeping them free of debris.