Raman fiber optic probe assembly for use in hostile environments

DETAILED DESCRIPTION This invention provides a device for Raman spectroscopic measurement of composition and concentrations in a hostile environment by the use of a first fiber optic as a means of directing high intensity monochromatic light from a laser to the hostile environment and a second fiber optic to receive the lower intensity scattered light for transmittal to a monochromator for analysis.
To avoid damage to the fiber optics, they are protected from the hostile environment.
To accomplish this a compact Raman fiber optic probe assembly is provided using an optimal 90.
degree.
Raman spectroscopy geometry.
It enables monochromatic light to penetrate into a hostile environment and scattered light to be collected by means of diamond windows and fiber optic cables.
This probe is suitable for hostile high pressure, high temperature, caustic environments.
A preferred embodiment of the Raman fiber optic probe is able to obtain Raman spectra of corrosive gases and solutions at temperatures up to 600.
degree.
F.
and pressures up to 2000 psi.
A 90.
degree.
scattering geometry is utilized which minimizes the Rayleigh scattering received by the collecting fiber.
The incident exciting fiber optic cable makes an angle of substantially 90.
degree.
with the collecting fiber optic cable.
This 90.
degree.
geometry minimizes the Rayleigh scattering signal picked up by the collecting fiber, because the intensity of Rayleigh scattering is lowest in the direction perpendicular to the beam path of the exciting light and therefore a 90.
degree.
scattering geometry optimizes the signal to noise ratio, that is the Raman signal against the Rayleigh background.
The criterion for the angle formed by the fiber optic cables is that the Raman signal be favored over the Rayleigh background.
The substantially 90.
degree.
angle can be between about 70.
degree.
and about 110.
degree.
.
Between 85.
degree.
and 95.
degree.
is more preferred, and the optimum angle is 90.
degree.
.
The preferred Raman fiber optic probe comprises a housing and two fiber optic penetrators sealed to the housing by gold metal gaskets