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Vacuum UV Spectroscopy

Posted on: October 28th, 2019

Introduction:

Does your LIBS or plasma application require measurements into the vacuum UV below the oxygen absorption limit of 185 nm?  If so, Avantes offers a great option for this need.

Spectroscopic measurements conducted in vacuum environments range from reflection measurements during coating processes to high-speed plasma monitoring during a reaction. These techniques are frequently used for sophisticated process control monitoring such as endpoint detection. This procedure involves monitoring a peak or wavelength range to detect a process inflection point characterized by a spectral shift which signals the end of the process. High vacuum (~10-3 torr) and ultra-high vacuum (~10−9 torr) measurements require special consideration when selecting a spectrometer and the associated fiber optics used for sampling. Avantes has worked extensively with customers operating in vacuum environments and offers a variety of instruments and accessories to meet the needs of vacuum spectroscopy.

For customers interested in the VUV wavelengths, the AvaSpec series is also available in a specialized configuration with purge ports to facilitate the evacuation of the optical bench using inert gases. The Purge-ULS option features two purge ports on the back of the spectrometer along with a magnesium fluoride window behind the slit and a top cover seal in the optical bench. This configuration is offered with a choice of a deep UV coated detector for operation down to 160 nm or window-less back-thinned detector which facilitates operation down to 120 nm. VUV configurations such as these often require specialized grating selections.

All Avantes spectrometers are available in single, dual or multi-channel configurations. Avantes’ unique instrument platform enables true synchronous operation of our multi-channel spectrometers so as to facilitate the simultaneous acquisition of spectral data from all instruments in an array.

Avantes PURGE-ULS

Avantes recently developed our PURGE-ULS option which is available on all our uncooled ULS spectrometers and provides for the evacuation of air from the optical bench and introduction of an inert gas such as argon.   Purged ULS spectrometers are capable of measuring down to 160 nm well into the vacuum UV.  The purge option consists of a UV transmissive window that is installed at the spectrometer entrance, sealing gasket for the optical bench and two external purge ports (inlet and output).   Below are some spectra obtained from a LIBS customer.  Avantes DA-COL-Spec is a direct-attached collimating lens that can also be purged and provides for fiberless illumination of our AvaSpec instrument, a requirement for vacuum UV applications.

For more information about this affordable yet extremely useful spectrometer option, please contact a Sales Engineer.