Patent ID: 7345766

Claim:
Apparatus for use in photo-acoustical measurements of radiation-absorbing substances in samples comprising, a housing which defines a tubular measuring channel, entry and exit windows aligned with said tubular measuring channel to enable a laser beam to enter the housing through the entry window, pass through the tubular measuring channel and exit the housing through the exit window, a first expanded chamber between the entry window and a first end of the tubular measuring channel, said first chamber having a larger cross-sectional area than a cross-sectional area of the tubular measuring channel, a second expanded chamber between the exit window and a second end of the tubular measuring channel, the second chamber having a larger cross-sectional area than the cross-sectional area of the tubular measuring channel, a third expanded chamber along the tubular measuring channel between the first and second expanded chambers which has a larger cross-sectional area than a cross-sectional area of the tubular measuring channel, a microphone in communication with the tubular measuring channel, a first sample entry channel in communication with the tubular measuring channel near the first end thereof, a second sample entry channel in communication with the tubular measuring channel near the second end thereof, and a first sample discharge channel in communication with the tubular measuring channel at a location between said first and second sample entry channels.