K Okuno

Gain characteristics of a microchannel plate and a channel-electron multiplier for low energy multiply charged ions

Abstract Pulse height distribution are measured when multiply charged ions of S, Ne, F, O, N and C are incident on a microchannel plate of chevron type (MCP) and a channel electron multiplier (CEM) in the velocity range of 3–4.5 × 105 m/s. The pulse height distributions obtained with the CEM shows no significant dependence of the gain on the energy, mass and charge state of incident ions. On the other hand, for the case of the MCP, an increase of the gain is observed with an increase of the charge state of incident ions irrespectively of ionic species. Such behavior is discussed in connection with secondary electron emission yield at the input and electron multiplication mechanism iin the channels.

Symmetric resonance multiple charge transfer of Neq+ and Arq+(q⩽4)

Cross sections for resonance charge transfer processes, Aq++A to A+Aq+, have been measured for Ne1-4+ and Ar1-4+ at ion acceleration voltages of 2, 3 and 4 kV. The cross sections obtained at 2 kV are 6.9*10-16, 1.74*10-16, 4.9*10-17 and 3.4*10-18 cm2 for Ne+, Ne2+, Ne3+ and Ne4+, respectively, and 2.4*10-15, 5.5*10-16, 9.0*10-17 and 3*10-18 cm2 for Ar+, Ar2+, Ar3+ and Ar4+, respectively. This is the first measurement of resonance charge transfer cross sections for quadruply charged ions. The results obtained are discussed in terms of the total ionisation energies Sigma jqIj of the ions, where Ij is the jth ionisation potential. A concept of the survival factor is introduced.

Electron capture processes of Iq+ ions with very high charge states (41⩾q⩾10) in collisions with He atoms

One-electron capture processes of iodine (Iq+) ions with very high charge q up to 41 in collisions with He atoms at low energies have been investigated using energy gain spectroscopy. It is found that total cross sections increase with increasing charge of ions q, and also increase roughly with the square of the crossing radius Rc of the diabatic potential curves in the quasi-molecules where the electron transfer takes place. This smooth variation, in contrast to that in ions with low charge where only few crossings play a role, can be understood from the fact that a number of the crossings closely located in a relatively narrow region of Rc contribute to the one-electron transfer processes in ions with high charge.

Observation of electron capture into selective state by fully stripped ions from He atom

Energy spectra of charge-changing projectile ions are measured for one-electron capture by fully stripped C and O ions from He atoms. The electron is selectively captured into a single level of principal quantum number n=3 of C5+ and n=4 of O7+, respectively, at a collision of 0.45 KeV amu-1.

Some characteristics of an electron beam ion source

Abstract Some charactersitics of a medium-sized EBIS have been investigated in the continuous and pulsed operation modes. It is found that a 1 keV and 100 mA electron beams, H-like ions such as C 5+ , N 6+ and O 7+ as well as He-like ions are produced with intensities comparable to those of doubly ionized ions. A weak trace of naked carbon ions ( 13 C 6+ ) is also seen in the spectra.

Two-electron capture into autoionising states of N5+ (3l3l') and O5+ (1s3l3l') in collisions of N7+ and O5+ with He

Transfer ionisation processes are studied for the N7++He and O7++He systems by means of ion beam spectroscopy at 7 keV. The autoionising states (3l3l) of N5+ and (1s3l3l) of O5+ are identified.

The (n,l) distributions in electron capture reactions for C3+, N4+ and O5+ ions colliding with He

Distributions of captured electrons in the reaction Aq++He to A(q-1)+(n,l)+He+ over the final-state quantum numbers n and l are measured using a beam spectroscopy method at the energy of 1.0q keV. Projectile ions Aq+ are Li-like species of carbon (q=3), nitrogen (q=4) and oxygen (q=5).

Electron capture in Iq+ (q = 10–41) + He collisions at low energies

One electron capture processes in Iq+ (q = 10–41) +He collisions at low energies have been investigated. It is found that total cross sections for one-electron capture processes increase roughly linearly with increasing charge q of the incident ions and also increase with the square of the crossing radius Rc of the diabatic potential energy curves where the electron transfer takes place. These smooth increases are in contrast to those observed for ions with low charge q < 10.

The dependence of Rc of cross sections for one-electron capture by S11+, S13+ and Krq+ (q=7-25) ions from He atoms

Total cross section measurements and translational energy spectroscopy have been performed at collision energies of 1q keV for one-electron capture processes by S11+, S13+ and Krq+ (7<or=q<or=25) ions from He atoms. When the measured cross sections are plotted as a function of the crossing radius Rc deduced from the observed energy gain, it is found that the cross sections in general increase with Rc and almost all of them lie between the 1/2 pi Rc2 and pi Rc2 curves. This dependence on Rc is very different from previous results for ions with relatively low q(q<10).