METHOD AND GAS SENSOR FOR PERFORMING QUARTZ-ENHANCED PHOTOACOUSTIC SPECTROSCOPY

• US 20090027677A1
• Filed: 01/08/2008
• Published: 01/29/2009
• Est. Priority Date: 07/24/2007
• Status: Active Grant

• Current Assignee: Axetris AG
• Original Assignee: Leister Process Technologies
• Inventors: SEIFERT, Andreas, WILLING, Bert, KOHLI, Markus
• Granted Patent: US 7,605,922 B2
• Time in Patent Office: Days
• US Class Current: 356/437
• CPC Class Codes: G01N 21/1702 with opto-acoustic detection, e.g. for gases or analysing solids
• CPC Class Codes: G01N 21/274 Calibration, base line adjustment, drift correction

Abstract

A method for performing quartz-enhanced photoacoustic spectroscopy of a gas, includes providing a light source configured to introduce a laser beam having at least one wavelength into the gas such said at least one molecule within in the gas is stimulated generating an acoustic signal, accumulating the acoustic signal in a resonant acoustic detector, generating a resonant absorption signal (S_A) relative to the gas concentration by at least one tuning fork serving as resonant acoustic detector, generating additionally a resonant intensity signal (S_I) proportional to the intensity of the laser beam travelling through the gas, and providing an output signal (S_GC) from said absorption signal (S_A) and said intensity signal (S_I) being independent of the intensity of the light relative to the presence or concentration of the gas.

Claims

1. A method for performing quartz-enhanced photoacoustic spectroscopy of a gas, comprising

providing a light source configured to introduce a laser beam having at least one wavelength into the gas such said at least one molecule within in the gas is stimulated generating an acoustic signal,

accumulating the acoustic signal in a resonant acoustic detector,

generating a resonant absorption signal (S_A) relative to the gas concentration by at least one tuning fork serving as resonant acoustic detector,

generating additionally a resonant intensity signal (S_I) proportional to the intensity of the laser beam travelling through the gas, and

providing an output signal (S_GC) from said absorption signal (S_A) and said intensity signal (S_I) being independent of the intensity of the light relative to the presence or concentration of the gas.

2. A method according to claim 1, comprising

generating said resonant absorption signal (S_A) by passing the light between the prongs of the said at least one tuning fork, and

generating said resonant intensity signal (S_I) by said at least one tuning fork wherein the light incidents mainly on the prongs of said at least one tuning fork.

3. A method according to claim 1, comprising

generating said resonant absorption signal (S_A) by passing the light between the prongs of the said at least one tuning fork, and

generating said resonant intensity signal (S_I) by said at least one further tuning fork arranged in series to and preferably behind said at least one tuning fork, now serving as first tuning fork, such said the light incidents mainly on the prongs of said at least one second tuning fork.

4. A method according to claim 3, comprising

tuning the light source onto the resonance frequency of said at least one first tuning fork to measure the gas concentration, and

separately, preferably subsequently, tuning the light source onto the resonance frequency of said at least second tuning fork to measure the laser intensity.

5. A method according to claim 3, comprising

providing an optical window between said at least one tuning fork and said at least second tuning fork.

6. A method according to claim 3, comprising

focusing the light beam onto a spot between the prongs of said at least first tuning fork,

placing said at least second tuning fork behind said at least first tuning fork at a distance such said the light intensity between the prongs is low in comparison to the light intensity incident on the wall of the prongs.

7. A photoacoustic gas detector for performing quartz-enhanced photoacoustic spectroscopy comprising

a light source for providing a laser beam,

a detection region provided for receiving at least one sample gas,

at least one tuning fork serving as resonant acoustic detector and providing a resonant absorption signal (S_A),

processing means for providing a signal relative to the presence or concentration of a given gas in said detection region.

8. A photoacoustic gas detector comprising

a light source for providing a laser beam,

a detection region provided for receiving at least one sample gas,

at least one first tuning fork serving as resonant acoustic detector and providing a resonant absorption signal (S_A),

processing means for providing a signal (S_GC) relative to the presence or concentration of a given gas in said detection region,

at least one second tuning fork arranged in series to and preferably behind said at least first tuning fork, said at least one second tuning fork serving as resonant acoustic detector for providing a resonant signal relative to the intensity of the laser beam travelling through said sample gas.

9. A photoacoustic gas detector according to claim 8, wherein the relative arrangement between said at least one second tuning fork and said laser beam provides mainly a resonant intensity signal (S_I) generated by the wall noise of the laser beam incidenting on the prongs of said at least one second tuning fork.

10. A photoacoustic detector according to claim 9, further comprising optical means for focusing the light beam onto a spot between the prongs of said at least first tuning fork.