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Title: Self-tuning method for monitoring the density of a gas vapor component using a tunable laser

The present invention relates to a vapor density monitor and laser atomic absorption spectroscopy method for highly accurate, continuous monitoring of vapor densities, composition, flow velocity, internal and kinetic temperatures and constituent distributions. The vapor density monitor employs a diode laser, preferably of an external cavity design. By using a diode laser, the vapor density monitor is significantly less expensive and more reliable than prior art vapor density monitoring devices. In addition, the compact size of diode lasers enables the vapor density monitor to be portable. According to the method of the present invention, the density of a component of a gas vapor is calculated by tuning the diode laser to a frequency at which the amount of light absorbed by the component is at a minimum or a maximum within about 50 MHz of that frequency. Laser light from the diode laser is then transmitted at the determined frequency across a predetermined pathlength of the gas vapor. By comparing the amount of light transmitted by the diode laser to the amount of light transmitted after the laser light passes through the gas vapor, the density of the component can be determined using Beer's law.
Inventors:
 [1];  [1];  [1];  [2]
  1. (Livermore, CA)
  2. (Tracy, CA)
Issue Date:
OSTI Identifier:
870585
Assignee:
United States of America as represented by United States (Washington, DC) LLNL
Patent Number(s):
US 5550636
Contract Number:
W-7405-ENG-48
Research Org:
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Country of Publication:
United States
Language:
English
Subject:
self-tuning; method; monitoring; density; gas; vapor; component; tunable; laser; relates; monitor; atomic; absorption; spectroscopy; highly; accurate; continuous; densities; composition; flow; velocity; internal; kinetic; temperatures; constituent; distributions; employs; diode; preferably; external; cavity; design; significantly; expensive; reliable; prior; devices; addition; compact; size; lasers; enables; portable; according; calculated; tuning; frequency; amount; light; absorbed; minimum; maximum; 50; mhz; transmitted; determined; predetermined; pathlength; comparing; passes; beer; law; monitoring device; gas vapor; atomic absorption; light passes; continuous monitoring; spectroscopy method; laser light; diode laser; flow velocity; vapor density; tunable laser; light transmitted; density monitor; diode lasers; absorption spectroscopy; cavity design; kinetic temperature; light absorbed; highly accurate; /356/

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