Characteristics of the Time-of-Flight Mass Spectrometer Hokushin Model 12(Bendix Model 12-100)have been discussed by the experiment, The important findings and conclusions obtained here are as follows;(i)The space charge in the ionization chamber is very small owing to the fact that neutral atomsor molecules are ionized by the pulsed electron beam. Therefore, the linearity between the ion and the electron trap current is very good except the case of ions whose m/e is smaller than 4.(ii)The characteristic curve of the electron trap current against the electron energy shows an abnormal point at 20 eV of the electron energy; that is, the electron trap current does not increase linearly with the bias voltage of the electron control grid.(iii)It is ascertained by the observation of the time of flight of ions that the flight path of ion is not strictly linear especially in the case of ion of small m/e. This is perhaps due to the existence of the collimating and compensating magnet. However, the time of flight of ion is close to the value calculated theoretically.(iv)The mass resolution has been determined to be about 140 by the measurement of the spectral line width, which increases almost linearly with m/e.(v)The, spectraline of CH3+ion in the spectrum of propane is found to be composed of three peaks, in which two peaks can be assigned to CH 3+ion having an excess kinetic energy.(vi)The absolutesen sitivity gradually decrease after the suppply of the high voltage to the electron multiplier. This phenomenon results in a serious effect on the accuracy of the quantitative analysisby this mass spectrometer.(vii)The cracking pattern coefficients obtained here are almost the same as the ones of A. P. I. The reproducibility is, however, slightly worse than that of the magnetic type mass spectrometer.(viii)The n-and iso-butane mixture of known composition has been analyzed by this mass spectrometer and the mean deviation is 1.5%.(ix)The reproducibility of mass spectrum on the synchroscope depends on the mean number of ions in the ionization chamber. In the present case, the fluctuation of peak intensity is about 20% at 104 ions in the ionization chamber. It has been considered for this problem that there must be some reasons other than the statistical fluctuation of ionization by the electron impact.
