Photoacoustic spectrometer for real-time dust monitoring

A method comprising:

• drawing in a particulate species through an inlet and into a chamber of a resonator of a monitoring device;
• directing a laser beam into the chamber of the resonator and toward the particulate species such that the particulate species absorbs energy from the laser beam and transmits heat to the surrounding air within the chamber of the resonator;
• measuring a power of the laser beam as it leaves the resonator and a sound pressure within the chamber of the resonator associated with the transmission of heat by the particulate species;
• and
• determining a mass concentration of the particulate species based on a ratio of the measured sound pressure and power of the laser beam.

A device for monitoring a mass concentration of silica particulates comprising:

• a resonator comprising an inlet, an outlet, a chamber extending between the inlet and the outlet, and a resonant frequency;
• a pump mechanism configured to draw in and direct silica particulates surrounding the monitoring device into the inlet and through the chamber and outlet of the resonator;
• a quantum cascade laser situated and configured to provide and direct a laser beam modulated with a square wave into the chamber of the resonator at a laser power modulation frequency approximately equal to the resonant frequency of the resonator, wherein the silica particulates within the resonator absorbs energy from the laser beam and transmits heat into the surrounding air within the chamber of the resonator;
• a photodetector situated and configured to receive and measure a power of the laser beam leaving the resonator;
• and
• a sensor situated and configured to measure a sound pressure within the chamber of the resonator associated with the heat transmitted from the silica particulates,
• wherein a wavelength of the laser beam ranges from 11 microns to 13 microns.