A Multi-Pass Absorption Cell
That Can Be Mounted Directly Onto The Plasma Chamber Is Required.
Zhang, "Sensitive detection of oxygen using a diffused integrating cavity as a gas absorption cell
," Sensors and Actuators B: Chemical, vol.
Many absorption spectroscopy techniques such as tunable diode laser absorption spectroscopy (TDLAS), quantum cascade laser absorption spectroscopy (QCLAS), or Fourier transform infrared (FTIR) spectroscopy rely on the accurate knowledge of the optical path length of the absorption cell
of the spectrometer wherein the gas sample interacts with the photons [1-6].
5 that consisted of the following parts: absorption cell
of 1 m length and of 1 [dm.sup.3] volume, equipped with 8 mm Ca[F.sub.2] windows; tunable laser by Sacher Lasertechnik; PIN G8370-1 photodiode by Hamamatsu; DAQ2000--data acquisition board by IOTech.
The spectrum of the absorption cell
is measured synchronously at exactly the same time instances as the output of the Mach-Zehnder interferometer.
The unit is a single-mode optical-fiber-coupled absorption cell
containing carbon monoxide [[blank].sup.12][C.sup.16]O gas, which has many absorption lines in t his region.
A multiple-pass absorption cell
with an effective path length of 5 m is used.