Azimuthally excited resonators for photoacoustic spectroscopy

Gordon S. Humphries, Michael Lengden

Research output: Contribution to conferencePoster

Abstract

Photoacoustic spectroscopy is a highly sensitive technique for the measurement of trace gases. Previously, we have demonstrated the benefits of using 3D printing technology to rapidly manufacture small form factor acoustic resonators at low cost and high sensitivity. We have designed a new 3D printed PAS cell that has been optimised to excite azimuthal resonances in the 10's of kHz range for a number of reasons. As transverse modes, the resonant frequency of azimuthal modes is not generally dependent on the length of the resonator, allowing for longer absorption pathlengths. Secondly, the diameter required to support a resonance in the acoustic frequency range is of the order of 10's of millimeters, much larger than the diameter of typical longditudinal resonance based designs, allowing easy integration of the resonator into mutipass, and cavity enhanced spectrometers. Furthermore, the increased cell diameter results in a decrease in the velocity of gas through the cell, reducing distrubance to the resonance structure. The presence of a node and antinode at the opposite vertices of the cell enables a two microphone detection scheme to be implemented, futher increasing the measured signal level. Despite the larger size and lower total acoustic pressure we have shown that 3D-printied azimuthally excited resonators have a similiar sensitivity to the longditudinal excited designs we have tested previously achieving a normalised noise equivilent absorption of 4.697 × 10-9 Wcm-1Hz-1/2
Despite the small size of the resonator itself, the equipment required for laser drive, modulation, and signal acquisition has a significantly larger footprint and high-power demand, which is not desirable in a field deployable sensor. We have also developed a low cost, compact embedded system using the National Instruments MyRio platform, which replaces much of this ancillary equipment. A digital phase sensitive detection algorithm is realised on the system’s processor. The MyRio platform is capable of wireless networking and, as much of the signal processing is completed locally, a high number of sensors can easily be networked and monitored from a single remote workstation to enable multi point measurements.
LanguageEnglish
Number of pages1
Publication statusPublished - 12 Sep 2018
EventField Laser Applications in Industry and Research (FLAIR) 2018 - Assisi, Italy
Duration: 10 Sep 201814 Sep 2018

Conference

ConferenceField Laser Applications in Industry and Research (FLAIR) 2018
CountryItaly
CityAssisi
Period10/09/1814/09/18

Fingerprint

Photoacoustic spectroscopy
Resonators
Acoustics
Acoustic resonators
Sensors
Microphones
Gases
Embedded systems
Spectrometers
Printing
Costs
Natural frequencies
Signal processing
Modulation
Lasers

Keywords

  • photoacoustic spectroscopy
  • azimuthal resonances

Cite this

Humphries, G. S., & Lengden, M. (2018). Azimuthally excited resonators for photoacoustic spectroscopy. Poster session presented at Field Laser Applications in Industry and Research (FLAIR) 2018, Assisi, Italy.
Humphries, Gordon S. ; Lengden, Michael. / Azimuthally excited resonators for photoacoustic spectroscopy. Poster session presented at Field Laser Applications in Industry and Research (FLAIR) 2018, Assisi, Italy.1 p.
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Humphries, GS & Lengden, M 2018, 'Azimuthally excited resonators for photoacoustic spectroscopy' Field Laser Applications in Industry and Research (FLAIR) 2018, Assisi, Italy, 10/09/18 - 14/09/18, .

Azimuthally excited resonators for photoacoustic spectroscopy. / Humphries, Gordon S.; Lengden, Michael.

2018. Poster session presented at Field Laser Applications in Industry and Research (FLAIR) 2018, Assisi, Italy.

Research output: Contribution to conferencePoster

TY - CONF

T1 - Azimuthally excited resonators for photoacoustic spectroscopy

AU - Humphries, Gordon S.

AU - Lengden, Michael

PY - 2018/9/12

Y1 - 2018/9/12

N2 - Photoacoustic spectroscopy is a highly sensitive technique for the measurement of trace gases. Previously, we have demonstrated the benefits of using 3D printing technology to rapidly manufacture small form factor acoustic resonators at low cost and high sensitivity. We have designed a new 3D printed PAS cell that has been optimised to excite azimuthal resonances in the 10's of kHz range for a number of reasons. As transverse modes, the resonant frequency of azimuthal modes is not generally dependent on the length of the resonator, allowing for longer absorption pathlengths. Secondly, the diameter required to support a resonance in the acoustic frequency range is of the order of 10's of millimeters, much larger than the diameter of typical longditudinal resonance based designs, allowing easy integration of the resonator into mutipass, and cavity enhanced spectrometers. Furthermore, the increased cell diameter results in a decrease in the velocity of gas through the cell, reducing distrubance to the resonance structure. The presence of a node and antinode at the opposite vertices of the cell enables a two microphone detection scheme to be implemented, futher increasing the measured signal level. Despite the larger size and lower total acoustic pressure we have shown that 3D-printied azimuthally excited resonators have a similiar sensitivity to the longditudinal excited designs we have tested previously achieving a normalised noise equivilent absorption of 4.697 × 10-9 Wcm-1Hz-1/2Despite the small size of the resonator itself, the equipment required for laser drive, modulation, and signal acquisition has a significantly larger footprint and high-power demand, which is not desirable in a field deployable sensor. We have also developed a low cost, compact embedded system using the National Instruments MyRio platform, which replaces much of this ancillary equipment. A digital phase sensitive detection algorithm is realised on the system’s processor. The MyRio platform is capable of wireless networking and, as much of the signal processing is completed locally, a high number of sensors can easily be networked and monitored from a single remote workstation to enable multi point measurements.

AB - Photoacoustic spectroscopy is a highly sensitive technique for the measurement of trace gases. Previously, we have demonstrated the benefits of using 3D printing technology to rapidly manufacture small form factor acoustic resonators at low cost and high sensitivity. We have designed a new 3D printed PAS cell that has been optimised to excite azimuthal resonances in the 10's of kHz range for a number of reasons. As transverse modes, the resonant frequency of azimuthal modes is not generally dependent on the length of the resonator, allowing for longer absorption pathlengths. Secondly, the diameter required to support a resonance in the acoustic frequency range is of the order of 10's of millimeters, much larger than the diameter of typical longditudinal resonance based designs, allowing easy integration of the resonator into mutipass, and cavity enhanced spectrometers. Furthermore, the increased cell diameter results in a decrease in the velocity of gas through the cell, reducing distrubance to the resonance structure. The presence of a node and antinode at the opposite vertices of the cell enables a two microphone detection scheme to be implemented, futher increasing the measured signal level. Despite the larger size and lower total acoustic pressure we have shown that 3D-printied azimuthally excited resonators have a similiar sensitivity to the longditudinal excited designs we have tested previously achieving a normalised noise equivilent absorption of 4.697 × 10-9 Wcm-1Hz-1/2Despite the small size of the resonator itself, the equipment required for laser drive, modulation, and signal acquisition has a significantly larger footprint and high-power demand, which is not desirable in a field deployable sensor. We have also developed a low cost, compact embedded system using the National Instruments MyRio platform, which replaces much of this ancillary equipment. A digital phase sensitive detection algorithm is realised on the system’s processor. The MyRio platform is capable of wireless networking and, as much of the signal processing is completed locally, a high number of sensors can easily be networked and monitored from a single remote workstation to enable multi point measurements.

KW - photoacoustic spectroscopy

KW - azimuthal resonances

UR - https://fox.ino.it/flair/

M3 - Poster

ER -

Humphries GS, Lengden M. Azimuthally excited resonators for photoacoustic spectroscopy. 2018. Poster session presented at Field Laser Applications in Industry and Research (FLAIR) 2018, Assisi, Italy.