mass_spectrometer Pfeiffer обзор (1248468), страница 3
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The usage of the software on more than one system is prohibited. The purchaser is only entitled to copy,re-work, translate or convert from the object code to the source code within the legally permissible scope (Articles69 a ff. of the Copyright Law (UrhG)). The purchaser commits himself not to eliminate or change the manufacturer’sinformation or Pfeiffer Vacuum’s information – especially copyright information – without Pfeiffer Vacuum’s explicitprior approval. All other rights relating to the software and the documentation, including the copies thereof, shallremain with Pfeiffer Vacuum or with the software supplier.
The issuance of sub-licences is not permissible.XII. Applicable Law/Place of Jurisdictioin1. All legal relations between Pfeiffer Vacuum and the purchaser are subject to the substantive laws of the FederalRepublic of Germany. This applies also for foreign business transactions. The application of the UN purchase rightwill be excluded.2.
The place of jurisdiction is the court competent for Pfeiffer Vacuum’s company seat. Pfeiffer Vacuum shall, however,be entitled to file a suit at the purchaser’s head office.1152ContentsPage684 Mass spectrometer for ion analysis945 AppendixResidual gas analysis3 Mass spectrometer for gas analysisGas analysis56Analysis of Ions2 Mass spectrometers for residual gas analysisFundamentalsGrundlagen4102Appendix1 Fundamentals of mass spectrometry31 Fundamentals of mass spectrometryContentsPage1 Fundamentals of Mass Spectrometry441.1Introduction71.2The quadrupole mass spectrometer91.2.1 The ionization process111.2.2 Mass separation171.2.3 Ion detection241.2.4 Control and signal evaluation291.333Mass spectrometer in connection with gas inlet and pump system1.3.1 Mass spectrometers – set ups for inlet pressures <10 mbar341.3.2 Mass spectrometers – set ups for inlet pressures >10 mbar391.446Mass spectrometer for detection of externally generated ionsand plasma diagnostics1.4.1 Detection of externally generated ions461.4.2 Application examples481.4.3 Mass spectrometric plasma diagnostics501.4.4 Solution variations501.4.5 Measurements with the plasma monitor521.4.6 Measurement range extension545AppendixAnalysis of IonsGas analysisResidual gas analysisFundamentals1 Fundamentals of mass spectrometry61.1 Introductionversely, development of vacuum technologies has increasingly required the utilization of small high performance massspectrometers.FundamentalsMass spectrometric measuring methodshave become an indispensable diagnosticaid in numerous branches of processengineering, technology and productdevelopment, medicine and basic scientific research.Mass and Charge● The total pressure is the sum of all pressures of a given gas mixture● To determine the partial pressure of a certain gas component, this component must beisolated from the mixtureThus prior separation of the gas mixture is necessary● This takes place according to the ratio of mass to charge: m/eNo separationTotal pressureTypical applications are:mass-selective leak testing of serialproduction components in the automotive industryquantitative determination of the composition and purity of process gasescomplex analysis of catalytic reactionson the surface of solid bodiesthe investigation of biochemical substance transformations.In view of this wide range of applications itis not surprising that in the course of recent decades numerous physical methodsfor mass separation of particles have beendeveloped and implemented in maturedpractical measuring instruments.In spite of the considerable difference ofthe methods, they all have a common feature.
A vacuum must be generated foroperating mass spectrometers, in manycases with several pressure ranges. Con-Separation in time or spaceIndividual partial pressuresFig. 1:In contrast to totalpressure measurements, in massselective measuringmethods detection isaccording to themass/charge ratioof the ions.Some examples are:leak detectionpartial pressure measurements in highvacuum systemsmonitoring of the gas composition invacuum coating processesend point determination in vacuumetchingmass-resolved determination ofneutral particles and ions in plasmaprocessesdetermination of gas-specific desorption and adsorption rates of materialsfor vacuum system components.Chiefly quadrupole mass filters (Fig. 2) areused today particularly for these measuring tasks.
The properties of quadrupolemass filters which are especially useful forthese applications are the simple mannerof scanning the entire mass range, highsensitivity, high measuring and repetition71 Fundamentals of mass spectrometryIon generation byelectron collision ionizationin the ion sourceIon separation accordingto the m/e ratioin the rod systemIon detectionin the ion detectorIon opticsyzxFormation spaceFilament(U+Vcosωι)Fig 2:Functional principleof a quadrupole massspectrometer.rate, large measuring range (up to 10decades) and compatibility with the general requirements of vacuum technologysuch as relatively small dimensions,arbitrary mounting position and low outgassing rates.A quadrupole mass spectrometer intendedfor partial pressure measurements is inprinciple an ionization vacuum gaugeequipped with an additional device, therod system, which first of all separates thetypes of ions produced by the ionizationMeasuring gas feedSample gasprocess according to their mass/chargeratio (m/e) before measuring them with anion detector.The ions are separated in a high frequency electric quadrupole field between thefour rod electrodes with field radius r0.The voltage between the electrodes consists of a high frequency alternating voltage Vcos t and a superimposed directvoltage U.
When ions are trapped in thedirection of the field axis perpendicular tothe plane of the diagram, they performGas inlet andpressure reductionMass-selective analyzer unitOutputInputHFGeneratorAnalyzerCalibration gasTest gasControlunitSPSQUADSTARsoftwareFig. 3:Components forgas analysisThe associated pumpsystems are describedin detail in the catalogPfeiffer Vacuum,Vacuum Technology2002–2004.8Control and measureddata evaluationQualitative gas analysisAQuantitative gas analysis%H2m/e in AMUHet in sec.Specific optimized application solutions(Fig.
3) are possible only by combininghigh performance mutually matched components for sample gas feed, for pressurereduction, for the actual mass spectrometer system and for the respective vacuumgenerating systems.Fundamentalsoscillations perpendicular to the field axisunder the influence of the high frequencyfield. For certain values of U,V, and r0only ions with a particular ratio m/e canpass through the separating field andreach the ion detector. Ions which have adifferent mass/charge ratio are rejected bythe quadrupole field and therefore cannotreach the detector.
Mass/charge ratio scanning can be achieved by varying the frequency (m/e ~ 1/2) or, as is for technicalreasons almost always the case, by varying the voltages (m/e ~ V) . This gives alinear mass scale by simple means. It isalso possible to adjust the resolution capability (⌬m/m) of a quadrupole mass spectrometer via the ratio of the magnitude Uof the direct voltage component to theamplitude V of the high frequency component. It must be pointed out already at thisjuncture that it is always necessary to finda compromise between best possiblemass resolution and high sensitivity.1.2 The quadrupole mass spectrometerA first technically realizable variant of aquadrupole mass spectrometer wasdescribed in 1953 by W. Paul and H.
Steinwedel [1, 2, 3]. The chief functional components of the mass spectrometers presented in this catalog are:analyzer unit (QMA) with ion source,rod system and detectorHF generator (QMH)electrometer preamplifier (EP) ora pulse preamplifier (CP)control unit (QMS,QMI) with thequadrupole electronics (QC)power supply for the ion source (IS)and the high voltage power supply fora SEM detector (HV) and the computerinterfaces (RS 232 C and LAN ArcNet)control and evaluation software(QuadStarTM)The modular construction with the variousfunctional groups permits technically optimised equipment variants with good priceto performance ratio for numerous applications, through combination of variousanalysers, different HF generators andspecific equipment variants for the controlunit. This also facilitates subsequent modification for other applications.
QuadStarTMsoftware is the common platform for thediversity of equipment versions, giving theoperator a standardised user interface andthe facilities for transferring measureddata, measuring parameter sets and complete measuring sequences even for verydifferent QMG systems.Only the analyzer unit is under vacuum. Itis attached via a CF flange connection,whereby the ion source (and the ionoptics) as well as a part of the rod systemproject into the analysis chamber.91 Fundamentals of mass spectrometryElectrometer preamplifierEP422Signal linesHF generatorQMH 400-1Vacuum, p < 1 · E-04 mbarRF linesControl unit QMS 422HV 421, HV 422QC 421, IC 421,AO 421, IS 421AnalyzerQMA 410Quadstar™RS 232 cable orLAN, optical fibre cableFig.
4:Functional componentunits of a QMG 422.10The mounting orientation of a quadrupoleanalyser can be arbitrary, i.e. it can beoptimally adapted to the particular application. The preamplifier is connecteddirectly to the signal output of the iondetector via a plug connection, to minimise signal losses.
The length of the HF linesand thus the possible distance betweenthe analyzer and the HF generator is usually limited, because the parasitic capacitances of the connecting leads make aconsiderable contribution to the totalcapacitance of the HF resonant circuit. Theattachment orientation of the HF generatoris arbitrary, but it is necessary to ensureadequate air circulation for cooling. Thecontrol units are constructed as slide-inmodules for racking systems and canaccommodate further modules for analogand digital signal input/output (AO 421, AI421, DO 421, DI 421). In addition to aninternal bus system which interconnectsall system components, the control unitsalso contain their own data and parametermemories, so that the current operatingmode (including set alarm points) can stillrun even when communication with thecomputer is interrupted.
A local operatorconsole CS 422 permitting operation without computer support is available for thecontrol unit QMS 422.In the compact units of the PrismaTM series(Fig. 5), the electronic components comprising the HF generator, the electrometerpreamplifier, the quadrupole electronics,the ion source power supply, the highvoltage power supply and the data interface, are combined in a housing and directlyconnected to the analyzer via a disconnectable plug connection. The direct couplingof the HF generator to the rod systemleads to significantly smaller HF powerloss when coupling-in the high frequencyfield.
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