The measurement of gas of vacuum system remains
From;    Author:Stand originally

Assign the content that pressure measures, in the leftover gas inside vacuum system, often not be onefold gas however gas mixture, in aeriform composition unidentified circumstance falls, ultrahigh vacuum plan the pressure that cannot decide its are corresponding. Use ionization plan for example (with air or azotic calibration) the equivalent nitrogen pressure that the ion that is gas mixture to the pressure that gas mixture measures sheds summation place correspondence (or) of dry air pressure. The sensitivity of because ionization compasses is right different gas is not identical, the equivalent nitrogen pressure that consequently ionization compasses measures to gas mixture place is not the real pressure of gas mixture, can have the error of quantitative class even sometimes. Right now, with cent manometric the real total pressure that the sum of measures each minutes of pressure just is gas mixture. To a lot of application, the volume level that measures the equivalent nitrogen pressure that gets leftover gas with total pressure gauge is adequate already. But the precision that if need metrical pressure,obtained ionization rule, criterion compasses canal should fixed calibration, must know it is right the opposite sensitivity of different gas, and must of gas of the remains inside ascertain system when becoming 10-5 Pa of pressure prep above, should use particularly diffuse pump when bleed of aircrew of one mechanical pump, class status of the atmospheric before leftover gas composition and bleed is similar. Value of total inside this pressure limits pressure is significant, pressure can be measured accurately. Pressure under 10 -5Pa when, the circumstance is no longer such. In the certain pump that uses in ultrahigh vacuum system, when taking gas mixture, often can stay certain did not pump the gas that remove actually. And in pressure under 10 Pa when, the gas that vacuum system component releases had main effect to ultimate pressure, the composition of these gas is different from atmosphere. To a lot of actual application, the nature that understands systematic remains gas is more significant than its pressure. Right now, total pressure of the system can't provide significant vacuum environment information, the bases that needs to know gas normally and the cent pressure that its compare exemple or them relatively. Cent pressure measures the leftover gas that surveys ultrahigh vacuum system to divide pressure to need measuring instrument of the pressure that use component. The mass spectra that assigning pressure measuring instrument is gas of the remains inside analytic vacuum system essentially plan, call leftover gas analyzer sometimes. The distinction of it and common mass spectrograph is spent in Yu Lingmin tall, the structure is compact, the quality scope that analyses gas is little. Vacuum mass spectra plan by analyse of ionic source, analysis implement with ionic detector 3 parts place is comprised. Ionization of gas of electronic collision remains relies on to generate ion inside ionic source. Ionic by classify through analysing area after proper electric field is derivative, be collected next and measure. Use normally individual collect extremely, the electric field of analyzer or magnetic field change with linear means, scanning crosses the aeriform quality range of analyzer, will collect extremely output scale pursues into mass spectra. Each kinds of ionic calibration can choose to collect in this kind of method extremely electric current, in order to decide minute of pressure. Namely specific gas pursues in mass spectra go up base sensitivity of peak height × is its divide pressure. The function that separates pressure to measure analyzer is mixed on ionization definitely the detached degree of ion of ionic and derivative efficiency, different gas and exploration efficiency. The main parameter of its function has token: ① measures quality range; ② quality resolution; ③ sensitivity; ④ is the smallest but check divides pressure; ⑤ divides pressure sensitivity. Quality range is in what take no account of resolution or can analyse below sensitivity quality counts range, this is the absolutely limitation of vacuum compasses. Normally the 1 / with atomic mass of carbolic isotope C 12 regard atomic mass as the unit, express with symbolic Amu, logogram is U, namely U—1. 66×10 ‘g. Atomic quality number is for the unit with the gram denotive atomic mass divides the business with earnings of atomic mass unit, m of commonly used symbol expresses, it is equal to the integer value of atomic weight on numerical value. Quality resolution is not defined directly pursue photogenic for detached mass spectra the ability of adjacent quality peak, and express as M of M / △ , △ M is distinguishable here the smallest quality between two peaks counts difference. Quality peak leaves body of approximate Yu Zhong in most circumstance. Because this resolution follows quality,be counted and change and M of as corresponding as opposite peak height peak width △ is concerned. If take △ M=1, mix when M of two quality peak can saying when M 1 is distinguishable is unit quality resolution.
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