Mass separation of deuterium and helium with conventional quadrupole mass spectrometer by using varied ionization energy.

Deuterium pressure in deuterium-helium mixture gas is successfully measured by a common quadrupole mass spectrometer (model: RGA200) with a resolution of ∼0.5 atomic mass unit (AMU), by using varied ionization energy together with new developed software and dedicated calibration for RGA200. The new software is developed by using MATLAB with the new functions: electron energy (EE) scanning, deuterium partial pressure measurement, and automatic data saving. RGA200 with new software is calibrated in pure deuterium and pure helium 1.0 × 10(-6)-5.0 × 10(-2) Pa, and the relation between pressure and ion current of AMU4 under EE = 25 eV and EE = 70 eV is obtained. From the calibration result and RGA200 scanning with varied ionization energy in deuterium and helium mixture gas, both deuterium partial pressures (P(D2)) and helium partial pressure (P(He)) could be obtained. The result shows that deuterium partial pressure could be measured if P(D2) > 10(-6) Pa (limited by ultimate pressure of calibration vessel), and helium pressure could be measured only if P(He)/P(D2) > 0.45, and the measurement error is evaluated as 15%. This method is successfully employed in EAST 2015 summer campaign to monitor deuterium outgassing/desorption during helium discharge cleaning.