Abstract
A sensitivity determination method for a quadrupole mass spectrometer using an electron impact ionization process was investigated to determine ion density from observed ion current. Theoretical expression of the relation among measured ion current, irradiated electron beam current and electron energy was obtained, in which direct ionization was assumed. Sensitivity was determined as a fitting factor of the calculated value to the measured ion current by the least square method.
Sensitivity was measured for argon under the condition that ionization processes except direct ionization were negligible. The dependence of measured ion current on the irradiated electron energy and current agreed with the theoretical prediction and the sensitivity was determined with an uncertainty of 6%. The same measurement was performed for uranium and the sensitivity was successfully determined.
