Gencoa and OPTIX
On Friday I had a video conference with GENCOA regarding the OPTIX device. I am very happy that my expectations were met. Perhaps since sometime in 1997, when we started working with our first Fours BMI low pressure nitriding (LPN) furnace, we have been dealing with the constant problem of how to optimally control the nitriding number in this process. It always failed because the only instrument available was a quadrupole mass spectrometer, which would be very difficult and prohibitively expensive to install on such a device.
OPTIX solves this. It is able to work with pressures as low as 500 mbar, which is exactly what we need. LPN has a working range from 300 to 400 mbar, LPC up to 10 mbar. In doing so, we do not need any special pumping system, in contrast to the quadrupole spectrometer, where the precondition is a turbomolecular pump and a vacuum < 10-6 mbar.
How does it work? It is a device working with plasma optical spectrometry, which can continuously evaluate the individual peaks of the gases present at wavelengths of 200 to 900 nm.
Typical spectra for mass and optical spectrometry are in this figure. It can be seen that this is a similar result of gas analysis, where the peak size can subsequently be transformed into mV voltage suitable for further evaluation. This can be, for example, a trigger, triggering some form of alarm, or directly a regulator linked to a mass flow meter with constant pressure regulation.
The easiest way to use gauges is to check the device for leaks, where we can easily find out from the spectrum whether the leak is from air or water. We will appreciate the usefulness of such an assessment if the source of the leak is a water cooler or the inner wall of the double-walled chamber, cooled by water. Exactly this type of leak is found with a classic helium leak detector very laboriously, and often without a concrete result. OPTIX can give us the answer to that very quickly.
A typical spectrum for water and air is shown in this figure. If the nitrogen (N2+) peak is smaller than the water (OH and H) peak, then everything is fine, the chamber is tight.
However, the gauge can also be used as a classic helium leak detector, as it is able to detect even the peak of helium entering the chamber. Unlike helium leak detectors, however, we have an overview of the entire spectrum, and at a significantly better price.
I consider OPTIX to be a revolutionary solution, especially for practice. After all, we all know what a problem is our inability to see the detailed behaviour of gases in heat treatment processes, without knowing what is happening to us in the vacuum chamber.
Jiří Stanislav
June 24, 2024
