DESCRIPTION
The CMP-30 multipass cell is a Herriott absorption cell with a total optical path length of 30m. It lends itself to applications which require a long interaction path length between an electromagnetic wave and a gaseous sample, e.g. for monitoring tasks in industrial environments, but also for infrared absorption spectroscopy in scientific research. The CMP-30 is avaliable in two models for standard and high pressure use.
APPLICATIONS
An incident beam enters the cell through a hole in one of the mirrors. The beam then undergoes 73 reflections, describing a circle of spots on each mirror surface, before exiting the cell again. The dimensions of mirrors, separation between adjacent spots and the diameter of the entrance/exit hole have been designed to avoid spot overlap and thus unwanted interference up to wavelengths of 3 μm.
The beam enters the cell in the horizontal plane, whereas the output beam travels upwards. This ensures a clear separation between input and output beam, permitting accurate absorption measurements even in case of misalignment or incorrect focussing.
The cell is resistant to the most common chemicals. Materials in contact with the gas are Pyrex and BK7 glass, stainless steel, CaF2, Gold, Viton and Teflon. Gas inlet and outlet ports at both ends of the cell allow for examining flowing gases. On the other hand, the Pyrex glass pipe can be removed in-situ without dismantling the cell, when “room air” measurements are to be performed.
The main structure of the CMP-30 HP is strengthened and the Pyrex tube of the CMP-30 standard is replaced by a steel one, additionally a pressure valve prevents the cell reaching pressures higher than 5 atm.
SPECIFICATIONS
| Optical path length | 29.9 m |
| Volume | 900 cm3 |
| Overall length | 55 cm |
| Overall height | 13.5 cm |
| Overall width | 10 cm |
| Mirror reflectivity (λ>1μm) | >98.2 % |
|
Transmission |
>26% |
| Operating pressure | 1 –5 Atm |
| Window transmission (CaF2) | 0.2 –9.5 μm |
