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Fast Optical Method for Leak Detection

This feasibility study explores an optical method to detect leaks as an alternative to mass spectrometer detection. The method involves creating a discharge in a cell connected to the test leak chamber and observing the emitted spectrum with an interferometer or dispersive instrument.

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Fast Optical Method for Leak Detection

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  1. New approaches for leak detection D. Mari,M. Bergoglio,M. Zucco INRIM: Istituto Nazionale di Ricerca Metrologica, Strada delle Cacce 91, 10135 Torino, Italy

  2. Task 2.5 Feasibility study on alternative methods than mass spectrometer leak detector to detect leaks within few seconds (INRIM) The aim of this task is to develop a fast optical method to detect leaks that can be used as an alternative to mass spectrometer detection for global leak detection when the measuring speed is an issue. Description of work:In order to be competitive with respect to mass spectrometer detection method, an optical method to detect leaks will be studied. The idea is to create a discharge in a cell connected to the test leak chamber and observe the emitted spectrum with an interferometer based instrument (like a Michelson or a Fabry-Perot interferometer) or dispersive instrument (prism or grating). Compared to other optical methods based on Lambert Beer law the discharge method has the advantage of requiring a simpler set-up for the source, but may have a larger associated uncertainty since it is difficult to model the effect of a discharge. Nevertheless the characteristic of this discharge method will fulfil the needs of the industry. 2

  3. Helium Spectroscopy (ground state) From web page: http://physics.nist.gov/PhysRefData/Handbook/Tables/heliumtable3.htm From: M. Alonso & E. J. Finn, Physics (Workingham: Eddison-Wesley)

  4. FTIR Spectrometer (transmission) • Collects and digitizes the interferogram by a scanning interferometer • Perform the FT transform • Calculates the spectrum of the incoming light MICHELSON INTERFEROMETER SAMPLE

  5. Broadband source and InGaAs detector: Interferogram and Fast Fourier Transform FFT

  6. FTIR preliminary results (transmission) H2O

  7. FTIR preliminary results (transmission)

  8. FTIR preliminary test at INRIM (EMISSION) Emission He-Ne LASER He Ne

  9. FTIR preliminary test at INRIM (He discharge) Gas inlet system arranged to have gas flows between 5x10-4 mbar L/s and 5x10-3 mbar L/s FTIR He plasma FTIR parameters to have a time interval of 0.1 s for signal acquisition The initial discharge was at a residual pressure of 3.8x10-2 mbar Gas Inlet Detector

  10. FTIR preliminary results at INRIM (He discarge)

  11. FTIR preliminary results at INRIM (He discarge) FTIR signal versus throughput ( mbar L/s )

  12. Thank you for your attention Thank you for your attention Thank you for your attention Thank you for your attention Thank you for your attention Thank you for your attention Thank you for your attention Thank you for your attention Thank you for your attention Thank you for your attention Thank you for your attention Thank you for your attention

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