NEW APPROACHES FOR LEAK DETECTION D Mari M

NEW APPROACHES FOR LEAK DETECTION D. Mari, M. Bergoglio, M. Zucco INRIM: Istituto Nazionale di Ricerca Metrologica, Strada delle Cacce 91, 10135 Torino, Italy 1

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

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

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

Broadband source and In. Ga. As detector: Interferogram and Fast Fourier Transform FFT 5

FTIR preliminary results (transmission) H 2 O 6

FTIR preliminary results (transmission) 7

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

FTIR preliminary test at INRIM (He discharge) He plasma FTIR Gas inlet system arranged to have gas flows between 5 x 10 -4 mbar L/s and 5 x 10 -3 mbar L/s FTIR parameters to have a time interval of 0. 1 s for signal acquisition The initial discharge was at a residual pressure of 3. 8 x 10 -2 mbar Gas Inlet Detector 9

FTIR preliminary results at INRIM (He discarge) 10

FTIR preliminary results at INRIM (He discarge) throughput FTIR signal mbar L/s 8. 2 E-04 1. 27 E-03 1. 4 E-03 2. 71 E-03 2. 0 E-03 4. 03 E-03 2. 3 E-03 5. 07 E-03 2. 7 E-03 6. 72 E-03 2. 9 E-03 7. 36 E-03 3. 3 E-03 8. 63 E-03 3. 6 E-03 1. 01 E-02 3. 9 E-03 1. 15 E-02 FTIR signal versus throughput ( mbar L/s ) 11

Th Thank an you ky for y ou our f o atte Thank yo ry u for you ntio r attentio our n n att Th Thank y ou for y ank en our atte t you ntion i o n Thank for Th y Th ank you for you ra Th an tten tion you ky Thank you for your atte ou for you r ntion ra tten att en tion ou for y tion Than our att k you Thank yo ention for yo ank you for you ra tten tion ur at tentio n u for you r attentio n 12