Comparison of 4 Residual Gas Analysers

Comparison of 4 Residual Gas Analysers
B. JENNINGER B. Jenninger TE-VSC

Overview of Suppliers (not exhaustive) PFEIFFER Vacuum Granville-Phillips INFICON HIDEN Analytical Thermo Scientific ULVAC Stanford Research Systems SRS MKS AMETEK B. Jenninger TE-VSC

Our choice 1. PRISMA QMA200 Head Part-Nr.: BKM25272, Ser.-Nr.:185381Z002 Control unit Part-Nr: BGD28505, Serial Nr.: W003 Largely used at CERN (more the 50 in use). Supplier: PFEIFFER (manufacturer INFICON under licence agreement) 2. Anharmonic Resonant Trap Mass Spectrometer ART-MS Head Part-Nr.: DYG, Ser.-Nr.:830A00272 Control unit 830-VQM, Part-Nr: U1-0 , Serial Nr.: 830 A 00261 Supplier: Brooks Automation Inc. (Granville-Phillips Centre) New Technology based on purely electrostatic ion trap combined with low power RF. Very compact. Control unit 3 m from head. Longer distances (10 and 20 m) under study at Brooks. 3. Thermo VGQ (controller) in combination with refurbished MASSTORR Head, Ser.-Nr.: MDT-2-415 Control unit Part-Nr: VGQ; Serial-Nr.: Supplier: Thermo-Scientific. (Refurbishing by Enterprise Technologies) (Refurbishing includes: Cleaning, replacement ion source and C-SEM, testing) There are about 20 Masstorr RGA heads available. They have been used for the “magic boxes” and mobile pumping groups in LEP (proved robustness). Masstorr control units are obsolete, but heads can be equipped with modern control VGQ units, which are used on the Thermo ONIX 100D. B. Jenninger TE-VSC

Our choice 4. RGA100 SRS Head, Serial.-Nr.: 8412E Control unit Serial-Nr.: Supplier: Stanford Research Systems RGA has been procured 10 ago. Faraday mode did not work. Repaired and put in service for the test this year. This RGA is still on the marked. (5. MKS Microvision IP) Head, Serial.-Nr.: MKS D2 Control unit Serial-Nr.: LM 15m matching unit: LM The work on this RGA presented here was done by Holger Neupert Supplier: MKS RGA with 15m extension cable and matching unit. It has been ordered for an application in the SPS. Not tested together with the other 4 RGAs. Analyser and extension unit seems identical with SPECTRA Satellite units, which are installed in AD. B. Jenninger TE-VSC

Working principle of quadrupole RGAs For details: \\cern.ch\dfs\Workspaces\d\div_lhc\VACUUM\Talks & Seminars\Cours Vacuum\Training2011 ResidualGasAnalyzers-PChiggiato THERMO-VGQ Ion source PRISMA QMA200 Ion source SRS Ion source B. Jenninger TE-VSC

Working principle of the Ion trap RGA (ART-MS) Ion source Ions crated inside ion trap and start oscillating Oscillation frequency is function of mass and charge Low power RF is superposed on transition plate potential (V6) At an RF of 2x oscillation frequency ions will enter in resonant mode => amplitude increase => ions are ejected Scan over RF frequency (80 ms) Total charge inside trap approximately constant. Ratiometric device (measures ion current proportions, but NOT absolute ion currents). Sensitivity depends on pressure and number of gas components. B. Jenninger TE-VSC

Test stand Measured system pumping speed for Hydrogen: SH2 = 133 l/s RGA 4 3 2 RGA 1 DN 100-CF Gate valve 0.5 L Calibrated BA-gauge Type SVT 305 Pirani & Penning Limit pressure (eq. H2) : PLimit = mbar B. Jenninger TE-VSC

Outgassing measurement Crosscheck compared with Time to reach stable pressure after change of filament status: ~ 2 hours B. Jenninger TE-VSC

Outgassing components Main outgassing component H2 Followed by CO, CH4 and H2O B. Jenninger TE-VSC

Spectra before bakeout P = mbar FARADAY PRISMA THERMO-VGQ Comparable quality of both spectra Possibility to view all relevant parameters with the spectrum Very stable noise level Narrow noise band Possibility to add comments with the spectrum Very low and stable noise level B. Jenninger TE-VSC

Spectra before bakeout P = mbar FARADAY SRS ART-MS Has no faraday mode Unstable noice level B. Jenninger TE-VSC

Spectra before bakeout P = mbar SEM PRISMA THERMO-VGQ Very good resolving power up to high masses and low currents Good resolving power Very large dynamic range: 6-7 decades Good dynamic range: 6 decades B. Jenninger TE-VSC

Spectra before bakeout P = mbar SEM SRS ART-MS Access to all relevant parameters during scan. All voltage settings can be modified by user. Software recalculates faraday current using gain Good resolving power at mid mass range Mass 3 not resolved Limited dynamic range: 4 decades Limited dynamic range: 3-4 decades Smallest mass Mass 1 not resolved B. Jenninger TE-VSC

Spectra after bakeout P = mbar SEM PRISMA Thermo - VGQ Tungsten from filament ESD peak Background shifted after baking Reduced resolving power due to increased step size as set by user (from 0.1 to 0.2 amu) B. Jenninger TE-VSC

Spectra after bakeout P = mbar SEM SRS ART-MS Limitation at 60 nA 2 Excellent resolving power at low masses 3 Because Ion currents are always calculated in faraday currents it not easy to see whether a spectre is made in faraday or SEM mode. In records ion source and scan parameters were wrong and did not correspond to the real settings during the scan as indicated in the screen shots.. B. Jenninger TE-VSC

Spectra as function of e--emission current PRISMA Linear up to ~ 1 mA Stable peak shape Space charge effects above 1 mA Factory setting of 2 mA seems too high Otherwise well optimised source Ion current ratios at peak maxima B. Jenninger TE-VSC

Spectra as function of e--emission current Thermo-VGQ Strong variation of peak shape Factory setting 1.6 mA too high Around 1 mA seems the optimum Minimum adjustable emission current 1 mA Ion current ratios at peak maxima B. Jenninger TE-VSC

Spectra as function of e--emission current ART - MS Very strong change in peak shape at higher masses and emission currents Factory setting of 0.07 mA too high System behaves differently if Mono-gas or multi-gas Below 10 micro A spectra very stable Ion current peak ratios Note the very small emission currents B. Jenninger TE-VSC

Spectra as function of e--emission current SRS Stable peak shape Factory setting of emission (1 mA) seems optimised Ion current peak ratios B. Jenninger TE-VSC

Sensitivity as function of Multiplier voltage P(Ar) = mbar PRISMA Thermo-VGQ S_far(Ar) = A/mbar S_far(Ar) = A/mbar ART-MS Current limitation SRS S_far(Ar) = A/mbar Unit: counts/step Step size = * mass Minimum adjustable gain 100. B. Jenninger TE-VSC

Sensitivity as function of pressure PRISMA Thermo-VGQ SEM SEM Sensitivity stable for mass 40 Sensitivity affected by change in peak shape Faraday Faraday B. Jenninger TE-VSC

Sensitivity as function of pressure SRS ART-MS Sensitivity increases with decreasing pressure At lower pressure, ratio remains constant SEM Sensitivity and peak shape constant over pressure range Faraday Ratio change with deformation of peak shape B. Jenninger TE-VSC

Resolution and resolving power Injection gas mixture: (Xe 10% / Kr 10% / Ar 10% / He 10% / H2 20% / CH4 20% / N2 20%) P_png = mbar PRISMA Constant peak shape Constant resolving power ∆ B. Jenninger TE-VSC

Resolution and resolving power Injection gas mixture: (Xe 10% / Kr 10% / Ar 10% / He 10% / H2 20% / CH4 20% / N2 20%) P = mbar Thermo-VGQ Peak shape not constant over mass range Resolving power affected by too large step size (user setting) Constant resolving power ∆ B. Jenninger TE-VSC

Resolution and resolving power Injection gas mixture: (Xe 10% / Kr 10% / Ar 10% / He 10% / H2 20% / CH4 20% / N2 20%) P = mbar SRS Peak shape constant over mass range Resolving power NOT constant ∆ B. Jenninger TE-VSC

Resolution and resolving power Injection gas mixture: (Xe 10% / Kr 10% / Ar 10% / He 10% / H2 20% / CH4 20% / N2 20%) P = mbar ART-MS Note the excellent resolving power at low masses Note, no sign of deformation of peak shape up to highest masses Multi-gas injection more favorable Less influence of gas in resonance to trapped charge (guess) ∆ Approximately constant resolution B. Jenninger TE-VSC

Few words on the MKS Courtesy Holger Neupert Very good linearity in faraday mode Calibration for H2 Mass spectra can only be represented in a pressure unit, which makes no sense Very BAD linearity in SEM mode N2 injection Good dynamic range and quality of spectra RGA with control unit installed in SPS B. Jenninger TE-VSC

Conclusion PRISMA was a good choice in terms of quality of spectra for standard loboratory applications where the instrument outgassing is not of concern. It is no more manufactured. Replaced by PRISMA PLUS with same analyser head, but different control unit and driver software (QUADERA, which is not user friendly in its present version). PRISMA and driver software (Quadstar) well known. With Alice Michet we put in place a procedure for ion source optimisation (focus, field axes and extraction). It is therefore normal that we get the best possible results out of this rga. For other RGAs it is not guaranteed that factory settings are optimised settings. For Thermo-VGQ and ART-MS it seems not. I do also not guarantee that I made the best possible use of the different driver softwares. With optimised ion source setting, the Thermo-VGQ (Masstorr) is certainly competitive with the PRISMA. SRS and MKS were not convincing The ART-MS needs further investigation for the optimum ion source setting and to understand its behavior under different conditions. It is a very promising candidate for particular applications like rapid acquisition, installation in radioactive environment and where very high resolving power is required. The ion source settings (emission current and repeller voltage) has to be optimised as function of pressure. Donat Holzer is working on this subject. B. Jenninger TE-VSC

Comparison of 4 Residual Gas Analysers

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