Magnetized retarding field energy analyzer measuring the particle flux and ion energy distribution of both positive and negative ions

Abstract

This paper presents the development of a magnetized retarding field energy analyzer (MRFEA) used for positive and negative ion analysis. The two-stage analyzer combines a magnetic electron barrier and an electrostatic ion energy barrier allowing both positive and negative ions to be analyzed without the influence of electrons (co-extracted or created downstream). An optimal design of the MRFEA for ion-ion beams has been achieved by a comparative study of three different MRFEA configurations, and from this, scaling laws of an optimal magnetic field strength and topology have been deduced. The optimal design consists of a uniform magnetic field barrier created in a rectangular channel and an electrostatic barrier consisting of a single grid and a collector placed behind the magnetic field. The magnetic barrier alone provides an electron suppression ratio inside the analyzer of up to 6000, while keeping the ion energy resolution below 5 eV. The effective ion transparency combining the magnetic and electrostatic sections of the MRFEA is measured as a function of the ion energy. It is found that the ion transparency of the magnetic barrier increases almost linearly with increasing ion energy in the low-energy range (below 200 eV) and saturates at high ion energies. The ion transparency of the electrostatic section is almost constant and close to the optical transparency of the entrance grid. We show here that the MRFEA can provide both accurate ion flux and ion energy distribution measurements in various experimental setups with ion beams or plasmas run at low pressure and with ion energies above 10 eV.

Enhancing surface production of negative ions using nitrogen doped diamond in a deuterium plasma

“…Recent measurements show that an absolute negative ion flux could be measured using a magnetised retarding field energy analyser via the technique described in Ref. 57…”

Plasma acceleration using a radio frequency self-bias effect

“…37 The only important difference with previously developed analyzer 37 is the presence of the RF compensation circuit, as described above. The necessity to use RF compensation for ion analysis follows from the fact that the ion transit time through this 1 mm thick RFEA is less than the RF period for the 4 MHz frequency and the Ar ion energy range of 50-500 eV.…”

“…With this analyzer, the ion transmission does not have a strong dependence on the ion energy and grids potential, which is common in multi-grid analyzers. 34,37 The RFEA consists from only one grid and a collector but is otherwise equivalent to the double-grid RFEA (see Fig. 2(b)).…”

“…The integrated ion peaks can easily be converted into the ion flux as U i ¼ T I peak /(qS), where T is an optical transparency coefficient of the grid (0.3 in our work), S is an area of the collector, I peak is the integrated ion current and q is the ion charge. 37 The single grid analyzer can also be operated in a "Mach probe mode." In this case, the grid is kept floating, while the collector is biased to a constant negative potential (À30 V in our experiments).…”

Latest experimental and theoretical advances in the production of negative ions in caesium-free plasmas

“…within the context of space propulsion [96,97]. A detailed description of the Magnetized Retarding Field Energy Analyzer (MRFEA) can be found in the reference [93] and a side-cut view is represented in Fig.…”