Mass spectrometers pressure gauges

As an UV-light source, a high-pressure mercury lamp supplied with a water filter and quartz light collimator was employed. The catalyst samples were irradiated in the quartz cell at ambient temperature in a circulating flow of NO-CO mixtures of different compositions. The composition of the gas phase above the catalyst was continuously monitored during UV-irradiation with a monopole-type MKh-7304 mass-spectrometer. Pressures of gaseous reactants were measured with a capacity-type gauge VDG-1 with an accuracy of about 3%. 

Vacuum system. Components associated with lowering the pressure within a mass spectrometer. A vacuum system includes not only the various pumping components but also valves, gauges, and associated electronic or other control devices the chamber in which ions are formed and detected and the vacuum envelope. 

Figure 7.6 shows a schematic set up for TPD. The crystal, mounted on a manipulator in an ultrahigh vacuum chamber, is heated such that the temperature increases linearly in time. The concentration of desorbing species is monitored with a mass spectrometer or with a simple pressure gauge. 

Total pressure, required for detailed interpretation of the mass spectra, is determined with an ionization gauge (S). The gas inlet system (A, B, C) is used for calibration purposes. The relation between measured total pressure and the ion current of an injected specific gas permits calibration of the mass spectrometer in absolute partial pressure units or amps/torr. 

N cuum technology mass spectrometer partial pressure gauges, definitions, characteristic variables, operating conditions 11/86... 

It is not enough merely to reach a low pressure it must also be possible to measure it. Ionization gauges are almost always used for this purpose. In these the residual gas is ionized, collected at an electrode, and the resulting current measured. The current varies linearly with the gas pressure down to about 10 11 torr. If the ions are separated by mass —making the gauge a mass spectrometer —then the partial pressures of various gases in the vacuum chamber can be determined. 

Residual Gas Analyzer. The residual gas or partial-pressure analyzer is a form of ionization gauge in which the positive ions are mass analyzed either by a conventional sector-mass-spectrometer arrangement (employing a permanent magnet) or by a quadrupole-mass-spectrometer arrangement (which requires no magnet). The ion current is amplified either... 

While a THF film (> 15 A) condensed on Li/Ag was warmed the gas composition in the UHV chamber was monitored using an ion gauge and the mass spectrometer. As expected, a pressure burst occured when the sample temperature reached about 163 K, the condensation point of THF, and a gas composition characteristic of vapor phase THF was detected by mass spectrometer. 

In almost every system, the Mettler Thermoanalyzer I was coupled to a quadrupole mass spectrometer, such as is illustrated in Figure 8.14 (37. 69i. The sample may be studied under vacuum 10"6 Tom or under higher pressures to 1 atm. The reaction chamber, R. is surrounded by the furnace and separated from the balance by a diffusion baffle. The evolved gases pass directly to the mass analyzer. F. which is connected to a recorder, J. through the mass spectrometer control panel. Total pressure is determined by an ionization gauge, S, which also permits the recording of the EGD curve (in this case, due to the pressure change in the system). The relation between measured total pressure and the ion current of the calibration gas permits calibration of the mass spectrometer in absolute partial pressure units or A/Torr. 

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