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Boston Technical Center (BTC) 1 Te-Yang Liu, Ph.D. senior scientist, Research & Development : Woburn,

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Presentation on theme: "Boston Technical Center (BTC) 1 Te-Yang Liu, Ph.D. senior scientist, Research & Development : Woburn,"— Presentation transcript:

1 Boston Technical Center (BTC) 1 Te-Yang Liu, Ph.D. senior scientist, Research & Development : Woburn, MA USA Insights Into H 2 O Measurements CRDS, TDLS 2013 March (v.1.012

2 DF-700 Model lineup H2O spectral characteristics Cavity ring down spectroscopy (CRDS) Tunable diode laser spectroscopy (TDLS) wavelength modulation (WM) Real World Data 700 series performance Live demo on 745SG GSF editor BTC Facility Photo Tour 2 Contents

3 3 Servomex TDLS – H 2 O analyzer models Model No.bkgrd gasLDL Full Range DF 750semi0.2 ppb20 ppm DF 760 Dualsemi0.2 ppb H2O20 ppm ppb O2 DF 749semi0.4 ppb20 ppm DF 745semi2 ppb20 ppm DF 730*HCl, H2, N210 ppb10 ppm DF 740*NH3, N210 ppb10 ppm DF 745SGspecialty100 ppb100 ppm semi: N2, O2, H2, He, Ar Specialty (12): + CO, CO2, SF6, N2O, N2, Kr, Xe; adding new gases… *: no blending

4 4 Instruments vs. Analyzers Laboratory instruments: non-continuous/discrete: requires calibrations before use: x-ray, APIMS, UV-Vis, FTIR, NMR, GC … etc performance spec: statistically established – long term stability Process analyzers: online 24 hr/7 days, no calibrations: Servomex DF-700 series performance & stability spec: empirically challenged & verified

5 5 O H H Transitions: Electronic: UV-Vis (C) Vibrational: IR (B) Rotational: microwave (A) E V R H 2 O Transitions - spectrum origin

6 H 2 O IR Spectrum - fingerprints m region 1.9 m region Popular detection wavelength at 1392 nm & 1854 nm

7 7 with a lamp source Cavity Ring Down Spectroscopy (CRDS) Perpetual like number of passes Single wavelength detection

8 8 CRDS Simplicity

9 9 R = ( 0 c – d) / 0 c = (100E-6* E10 – 30) / (100E-6* E10) = = % CRDS – mirror reflectivity, & for 0 = 100 µs, d = 30 cm, 100 µs = 30 km = 100, 000 passes TO web

10 10 CRDS – extremely sensitive to R Graph 1: Mirror Reflectivity vs. 0 at d = 30 cm

11 11 0 (µs) R 10 ppb of moisture sample A: 1 (µs)B: (µs) C: eq. res CRDS – reducing resolution vs. Table 1: resolution vs. 0 Easier to resolve 4.9 µs at 200 µs than at 100 µs. A resolution = 4.9 µs in time -> 10 ppb at 0 = 200 µs. The same can only resolve 173 ppb at 0 = 50 µs. CRD Optics

12 12 CRDS – reducing resolution vs. Graph 2: 1ppb equivalent resolution vs. mirror reflectivity If a new analyzer with a 0 = 200 µs has a 1 ppb ( = 0.50 µs) resolution, when 0 decreases to = 50 µs, with same = 0.50 µs its resolution is reduced to 16 ppb.

13 13 CRDS – baseline drift vs. R & 0 Graph 3: baseline up-drift due to decaying R, resulting in decaying 0 Graph 4: baseline up-drift due to decaying 0 If not zeroed, reading drifts up with decaying R. Q: when? (auto 0?)

14 14 Know CRDS available: know crds.exe (http://56123.info/56123/?p=725)know crds.exe

15 15 CRDS Limitation – mirror reflectivity CRDS analyzers health indicator: where is the 0 ? the mirror reflectivity? Analyzers reading Analyzers resolution Analyzers zero depends on 0 Two parallel mirrors, infinite passes =>>> Conundrum: Higher reflectivity -> better resolution ? Higher reflectivity -> less light escape -> less signal Perpetual-like number of passes …

16 16 Servomex TDLS - implementation H 2 O vial LASER Multi-pass Herriott Cell Mirrors Cell Window sample Detector Focusing Mirror Gas Outlet Gas Inlet I o /I Wavelength modulation Partially reflected reference beam reference Detector Herriott cell: resilient self-focusing multi-passes Wavelength modulation: S/N enhancement H2O spectrum: absorption peak capture

17 Tunable Wavelength (nm) Laser Current mA Laser Wavelength modulation Wavelength vs. current plot Servomex TDLS – detection scheme (sim) Artfully scan (16 Hz), gather and capture an absorption peak area and shape. Modulation at ~43 kHz. The laser wavelength is locked to reference H2O line center. Checked every 2 seconds. Laser wavelength tuning: fine: current coarse: temperature Software monitors more than 25 pars every 2 – 30 seconds 17

18 18 Servomex TDLS – Voigt profile (sim) Gaussian: thermal Doppler broadening Lorentzian: pressure broadening Voigt line shape: convolution of Gaussian + Lorentzian

19 19 Servomex TDLS – peak profiles (sim) Original absorption profile 1f Voigt profile 2f Voigt profile

20 Data and spectra in the presentation are from our customers DF-700 units with a standard released firmware. (unless otherwise stated) 20 Real World Data Servomex: DF-700 series H2O analyzers: 1.5 decades of making DF series O2 analyzers: 4 decades of making

21 21 X: wavelength index Y: 2f H2O intensity Blue: ~200 torr Red: ~760 torr H2 PB: 2.1E-4, 1.5x H2O/H2: 900 ppb N2 PB: 3.2E-4, 1x H2O/N2: 350 ppb Background Gas Pressure Broadening Laser line width << 1/100 absorption peak

22 22 Servomex TDLS – profile modeling H2O in semi-conductor background gases: N2(3.2E-4, hardest), O2(1.5E-4), N2 350 ppb 200 torr N2 350 ppb 1 atm O2 400 ppb 1 atm O2 450 ppb 200 torr Blue: experiment Red: model

23 23 Servomex TDLS - performance 0.7 ppb of H2O in He background gas ND-10489

24 24 Servomex TDLS – ppb step linearity Courtesy: APCI

25 25 Servomex TDLS – sub ppb steps Courtesy: APCI

26 Moisture in Argon Courtesy of SAES Getters S.P.A. 26 Servomex TDLS – 2 ppb steps

27 Courtesy of SAES Getters S.P.A. Moisture in Argon 27 Servomex TDLS – large ppb steps

28 28 Servomex TDLS – long term stability 1 ~ 8 years ~ 7 years ~ 8 years 3 customer units

29 29 Servomex TDLS – long term stability 2a Trend period: ~6.5 yr (2,348 days, 4:01:23 ), background: He User reading: Raw reading: 1 year: Summer/fall 1 customer unit

30 30 Servomex TDLS – long term stability 2b Continued from previous page Ambient temp: Laser intensity: Raw reading:

31 31 745SG GSF editor live demo Easy, very easy to use User templates Gas blending Expandable *PH3: no longer supported in 745SG

32 32 Servomex – visual photo tour rds2

33 33


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