Ion source based on Penning discharge for production of doubly charged helium ions

The method of Cermak and Herman has been applied to studies of unsymmetrical charge and proton transfer reactions. If the charge is transferred between atoms low cross sections are observed since part of the kinetic energy of the reacting system has to be converted into internal energy of the reactants. Large cross sections, however, have been found for the charge transfer between polyatomic species where apparently no resonance restriction exists. In several instances the unsymmetrical transfer B++A ➝ B+A+ has a higher rate than either of the processes B++B or A++A. If the ionization potential of B is lower than that of A the cross sections are in general low. In certain cases exceptionally large cross sections are observed and can be explained by the excess energy of a long lived excited state of the donor B+. Dissociations following the transfer of one charge from a doubly charged ion to a neutral molecule such asKr+++H2O ➝ (Kr+)*+ (H2O+)* ➝ OH++H ,NO+++NO ➝ (NO+)*+(NO+)* ➝ N++Ohave also been observed. The results indicate that the doubly charged ion generally captures the electron into a high lying orbital.Protonated cyclopropane is shown to be readily formed in ionized cyclopropane. In mixtures of water and methane, proton transfer has been observed in both directions. A large isotope effect on the secondary ion currents resulting from the transfer of a deuteron or a proton has been found in several simple systems. This isotope effect appears only if the secondary ions are observed in the Cermak—Herman method and is not found in the conventional operating of the ion source where reactions of slow ions predominate. This information provides some insite into the mechanistic details of the proton transfer since little isotope effect is expected if the reaction occurs via an inelastic collision complex while an isotope effect of the order of magnitude observed here is predicted by a stripping model.

Download Full-text

Re-ionization of a partially ionized plasma by an Alfvén wave of moderate amplitude

Journal of Plasma Physics ◽

10.1017/s0022377800022637 ◽

1980 ◽

Vol 24 (1) ◽

pp. 65-74

Author(s):

M. H. Brennan ◽

M. L. Sawley

Keyword(s):

Plasma Temperature ◽

Torsional Wave ◽

Alfven Wave ◽

Helium Plasma ◽

Acoustic Oscillations ◽

Radial Density ◽

Helium Ions ◽

Wave Pulse ◽

Partially Ionized ◽

Doubly Charged

This paper reports on the use of forced magneto-acoustic oscillations to investigate the effect of a torsional hydromagnetic (Alfvén) wave pulse of moderate amplitude on the properties of a partially ionized afterglow helium plasma. Observations of the magnetic flux associated with the oscillations, measured at a number of frequencies, are used to determine radial density proffles and to provide estimates of plasma temperature. The torsional wave is shown to cause significant re-ionization of the plasma with no corresponding increase in the plasma temperature. The torsional wave is shown to cause significant re-ionization of the plasma with no corresponding increase in the plasma temperature. However, the presence of a number of energetic particles is evidenced by the production of a significant number of doubly charged helium ions.

Download Full-text

Rate of decrease in the intensity ratio of doubly charged ions to singly charged ions in liquid-metal ion source with gold-based alloy

Ultramicroscopy ◽

10.1016/s0304-3991(97)00140-x ◽

1998 ◽

Vol 73 (1-4) ◽

pp. 83-87 ◽

Cited By ~ 3

Author(s):

Y. Gotoh ◽

H. Tsuji ◽

J. Ishikawa

Keyword(s):

Liquid Metal ◽

Intensity Ratio ◽

Metal Ion ◽

Ion Source ◽

Doubly Charged Ions ◽

Singly Charged ◽

Doubly Charged ◽

Charged Ions

Download Full-text

Contrast Differences Between Nitrogen and Helium Ion Induced Secondary Electron Images Beyond Instrument Effects

MRS Advances ◽

10.1557/adv.2018.33 ◽

2018 ◽

Vol 3 (10) ◽

pp. 505-510 ◽

Cited By ~ 1

Author(s):

Marek E. Schmidt ◽

Shinichi Ogawa ◽

Hiroshi Mizuta

Keyword(s):

Secondary Electron ◽

Bubble Formation ◽

Ion Source ◽

Limiting Factors ◽

Helium Ions ◽

Gas Field ◽

Helium Ion ◽

Ion Microscopy ◽

Nitrogen Ion ◽

Ion Species

ABSTRACTThe gas field ion source (GFIS) is able to generate tightly focused ion beams, which can be used to image or modify a specimen. Among the beam species, helium offers extremely high resolution, however, low sputter yield and sub-surface bubble formation are limiting factors in some applications. Therefore, heavier ions such as neon or nitrogen are used as well. In addition to being a suitable choice for lithographic mask editing, secondary electron (SE) generation by nitrogen beams has been recently shown to be affected by certain types of samples, providing additional contrast compared to helium ions. Here, we report our progress on the study of SE imaging differences between the nitrogen ion microscopy (N2IM) and helium ion microscopy (HIM). SE images of two nano-patterned samples comprising insulator, metal and carbon regions have been imaged by nitrogen and helium ions in two fundamentally different GFIS microscopes. The results corroborate previous reports of significant contrast differences in certain samples caused by the different ion species.

Download Full-text