A time-of-flight spectrometer for investigations on liquid metal ion sources

Abstract

A time-of-flight spectrometer with differential pulse sweeping was developed for the mass and energy analysis of ions emitted from liquid metal ion sources. The system was tested with a gallium liquid metal ion source. The angular intensity of the total source current, the mass spectra and the energy spread for , and as function of source current have been measured. A mass and energy resolution of about 700 has been obtained independent of the ion mass.

Investigations on a Co–Dy liquid alloy ion source

“…Mass spectra and energy distributions of the emitted ions have been investigated in a time-of-flight spectrometer (TOF). The experimental set-up and the characteristics of the TOF system are described in detail by Mühle et al (1999). The present measurements were done at an acceleration voltage of 5 kV, deflection voltages of 80 and 160 V and at a pulse frequency of 4 kHz.…”

“…The present measurements were done at an acceleration voltage of 5 kV, deflection voltages of 80 and 160 V and at a pulse frequency of 4 kHz. The flight path length L was enlarged from 1.15 to 1.24 m. The spectrometer has a mass and energy resolution of about m/ m = E/ E ≈ 800, see Mühle et al (1999). By the beam defining aperture, see figure 1 in Mühle et al (1999), only an axial part of the beam of nearly 180 µsr is selected for investigation.…”

“…For an absolute comparison of the ion intensities the mass spectra are statistically dead-time corrected, whereas the energy distributions are corrected for the finite time resolution of the electronic system used and the effects of the bunching process (Mühle et al 1999).…”

“…Figure 4 shows a spectrum of the complete mass region at a total source current of 2 µA. The calibration of the time scale and the conversion into a mass scale has been accomplished with known mass peaks using the simple relation that the flight time is proportional to √ m/q, m being the mass and q the charge of the considered ion; see Mühle et al (1999). The total flight time window in figure 4 is nearly 18 µs.…”

Micro mass spectrometer on a chip.

“…For example, in the case outlined in Table 1-1, for ∆E = 0.016 eV the mass resolution m/∆m is about 100. For a typical time-of-flight ionization method ∆E is in the order of unity (Muhle, Dobeli et al 1999). …”