An optical system for performing an absorption measurement of a medium sample includes a laser source configured to output a laser beam having a wavelength corresponding to an absorption region of interest; a ringdown cavity comprising a chamber configured to receive the medium sample, an input mirror at an input end, an output mirror at an output end, and an optical axis that extends through the centers of the input mirror and the output mirror; a coupling device configured to couple the laser beam through the input mirror into the chamber; and a detector optically coupled with the cavity, and configured to detect an intensity of light of the wavelength corresponding to the absorption region of interest that extends through the output mirror, wherein a cavity geometry of the cavity increases the re-entrant condition of the cavity relative to a conventional cavity comprised of two spherical mirrors.

A measuring apparatus for measuring a spectrum of a gaseous sample includes a tunable laser light source to provide an illuminating light beam, a sample cell with an inner surface to provide scrambled light that is transmitted through the gaseous sample, a detector to detect intensity of transmitted scrambled light and a pressure control system to maintain an absolute pressure of the gaseous sample smaller than 50 kPa inside the sample cell to reduce spectral widths of spectral features of the gaseous sample. The measuring apparatus measures spectral transmittance values of the sample by modulating the spectral position of the illuminating light, and detecting the intensity of the transmitted light at different spectral positions. The divergence of the illuminating light beam in a transverse direction is greater than 20° to cause multiple consecutive reflections of the scrambled light from the inner surface.

In one illustrative configuration, an air quality monitoring system may enable wide-scale deployment of multiple air quality monitors with high-confidence and actionable data is provided. Further, the air quality monitoring system may enable identifying a target emission from a plurality of potential sources at a site based on simulating plume models. The simulation of plume models may take into consideration various simulation parameters including wind speed and direction. Further, methods of determining a plume flux of a plume of emissions at a site, and methods of transmitting data from an air quality monitor are disclosed.

A sensor is disclosed, comprising: a first optical reflector provided on a first support element; a second optical reflector provided on a second support element and arranged opposed to the first optical reflector along an optical axis, the opposed first and second optical reflectors being spaced from each other forming a sample space for containing a sample between the first and second optical reflectors; wherein the second optical reflector comprises a recess to provide an optical cavity with stable resonance in at least one mode and having an optical cavity length of at most 50 μm and/or an optical mode volume of 100 μm.sup.3 or less; at least one electromagnetic (EM) radiation source configured to illuminate the optical cavity with EM radiation; and a detector configured to detect EM radiation from the optical cavity; wherein the first support element and the second support element are bonded to each other and form a unitary structure.

A flow cell assembly (16) for a fluid analyzer (14) that analyzes a sample (12) includes (i) a base (350) that includes a base window (350B); (ii) a cap (352) having a cap window (352B) that is spaced apart from the base window (350B); and (iii) a gasket (360) that is secured to and positioned between the base (350) and the cap (352), the gasket (360) having a gasket body (360A) that includes a gasket opening (360B). The gasket body (360A), the base (350) and the cap (352) cooperate to define a flow cell chamber (362). Moreover, an inlet passageway (366) extends into the flow cell chamber (362) to direct the sample (12) into the flow cell chamber (362); and an outlet passageway (368) extends into the flow cell chamber (362) to allow the sample (12) to exit the flow cell chamber (362).

Apparatus and method for detecting a dissolved gaseous impurity in an aqueous environment, comprises a tube for isolating liquid surface, or a sampler for obtaining a liquid sample from the aqueous environment, a vacuum pump located to exert a vacuum, leaving the surface to evaporate into the vacuum; and a holding compartment for holding evaporated gas which may then be analyzed using electrochemical or spectroscopic methods. The apparatus is useful for detecting levels of ammonia in fish ponds or indeed any impurity that may be dissolved in the water.

The invention concerns sensors (1) for detection of gas, in particular sensors for detection of transcutaneous gas such as CO.sub.2, and methods for manufacturing a sensor (1). The sensor (1) comprises at least one radiation source (3) for emitting radiation, at least one detector (4) for detection of radiation emitted by the radiation source (3), and at least one measurement chamber (6) for receiving the sample gas. The radiation source (3), the detector (4), and the measurement chamber (6) are arranged such that at least a part of the radiation propagates along a path passing through the measurement chamber (6). The sensor (1) further comprises a casing (7), wherein the radiation source (3), the detector (4), the measurement chamber (6) are arranged. The sensor (1) has a contact face (8) which is directable towards a measuring site and the sensor (1) has at least one gas-access channel (9) enabling gas to migrate from the contact face (8) into the measurement chamber (6). The casing (7) comprises a, preferably metallic, material having a high thermal conductivity, preferably more than 10 W/m/K.

A beating spectroscopy device includes: first and second quantum cascade lasers; a quantum cascade detector; and a sample holder configured to hold a sample on an optical path between the second quantum cascade laser and the quantum cascade detector. Lights from the first and second quantum cascade lasers are detected by the quantum cascade detector while a wavelength of the light from the second quantum cascade laser is changed to scan a frequency of a beating signal having a frequency in accordance with a wavelength difference between the lights from the first and second quantum cascade lasers.

A gas cell (1) for the spectroscopic, in particular absorption spectroscopic, analysis of a gas, in which the gas is exposed to an incident beam of rays (S) of electromagnetic radiation and a beam of rays (S.sub.A) of electromagnetic radiation exiting the gas is detected to form a measurement signal, wherein the gas cell (1) comprises a body (10) formed by a porous, electromagnetic radiation-scattering material, an in-coupling device (20) for coupling the incident beam of rays (S) into the gas cell (1) and an out-coupling device (30) for coupling the exiting beam of rays (S.sub.A) out of the gas cell (1), wherein, according to the invention, the gas cell is further developed according to the invention by forming a material-free cavity (12) in the body (10), which is surrounded by an inner surface (14) running within the material and is both diffusely reflecting and transmitting the electromagnetic radiation.

An apparatus for analysing a liquid sample comprising particles, comprises: a first chamber (12) and a second chamber (14), and an optical path between the first chamber (12) and the second chamber (14), wherein: the first chamber (12) is a sample chamber comprising: a sample space for receiving the sample; a light input (24) for input of light into the first chamber (12) for interaction with the sample; and an exit aperture (26) arranged for scattered and/or reflected light to pass from the first chamber via the optical path to the second chamber (14); the second chamber (14) is a detection chamber comprising: an input aperture (28) for receiving light from the optical path; and a detector (25) for detecting, or a detector aperture for receiving, light to be detected; wherein the first chamber (12) and the second chamber (14) provide at least one light integrating volume, and wherein the first chamber (12) is configured such that in operation the liquid sample is present in the first chamber (12) and isolated from the second chamber (14).