Method for accurately measuring partial pressure of hydrogen, deuterium and helium by using conventional quadrupole mass spectrometer

Abstract

The invention provides a method for accurately measuring partial pressure of hydrogen, deuterium and helium by using a conventional quadrupole mass spectrometer. The method comprises the following steps: selecting two kinds of ionization energy of low (15.4-24.5 eV) ionization energy and high (>25.3eV) ionization energy, distinguishing the contribution of H2<+> and D<+> to the ion flow of the mass number (AMU) 2 and the contribution of D2<+> and He<+> to the ion flow of the AMU4 according to the characteristic that the molecular ionization threshold values and the atomic ionization threshold values of the hydrogen. Calibration of a four-stage mass spectrometer is carried out in a wide-range vacuum environment of pure hydrogen, pure deuterium and pure helium, and corresponding relations between various gas pressures and ion flows of AMU2 and AMU4 under two selected ionization energies are obtained. In subsequent four-stage mass spectrometer measurement, ion flows of AMU2 and AMU4 under two selected ionization energy conditions are scanned at the same time, and accurate partial pressure of hydrogen, deuterium and helium is obtained through analysis and calculation.

Description

technical field [0001] The patent of the present invention relates to the field of vacuum measurement, specifically using a conventional low-resolution quadruple mass spectrometer to realize Method for accurate measurement of partial pressures of hydrogen, deuterium and helium. Background technique [0002] In nuclear fusion research devices, deuterium and helium are usually used as experimental gases, and hydrogen is a conventional participating gas in the vacuum chamber. For the purposes of device leak detection and impurity removal, it is necessary to accurately measure the hydrogen, deuterium and helium gas. gas pressure. But due to deuterium gas (D 2 , mass number 4.028) is very close to the mass number of helium (He, mass number 4.003), while hydrogen (H 2 , mass number 2.016) is also very close to the mass number of deuterium atom (D, mass number 2.014), and the conventional quadruple mass spectrometer cannot directly distinguish D due to insufficient resolution. ...

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Problems solved by technology

[0005] In order to solve the shortcomings of current accurate measurement of hydrogen, deuterium and helium partial pressures such as high cost, large equipment volume and inaccurate measurement, the present invention provides a method for accurately measuring hydrogen, deuterium and helium partial pressures using a conventional quadruple mass spectrometer. method, considering that conventional quadruple mass spectrometers cannot accurately measure hydrogen, deuterium and helium due to their resolution, but they usually have the function of ionization energy adjustment. In addition, although deuterium molecules and helium molecules, and hydrogen molecules and deuterium atoms The mass numbers are close, but these molecules and atoms have different ionization thresholds, as follows: H 2 + 15.4eV, D 2 + 15.4eV, He + 24.5eV, D + 25.3eV

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