Toyoyuki Ishihara

Empirical formula for the average equilibrium charge-state of heavy ions behind various foils

A new empirical formula for the average equilibrium charge-state, q, of heavy ions observed after traversal of various foils is presented. The formula is q=[1−exp(−1.25X+0.32X2−0.11X3)]1−0.0019(Z2−6)X+0.00001(Z2−6)2X where Z1 and Z2 are the ion and target foil atomic numbers respectively, and X is the reduced ion velocity as defined by Nikolaev and Dmitriev [1]. The present formula is useful for the collision range Z1 ⩾ 8, 4 ⩽ Z2 ⩽ 79 and E < 6 MeV/amu, to within an accuracy of Δq/Z1 < 0.04.

Z2 oscillation of mean charge states of fast Si and Cl ions after passage through thin foils

Abstract Z 2 (target atomic number) oscillation of equilibrium charge states has been observed for 30–110 MeV Si and 70 and 110 MeV Cl ions after the passage through 22 different Z 2 foils. This oscillation may be related to the Z 2 oscillation of electron capture cross sections into the projectile K vacancy.

Equilibrium charge state distributions of fast Si and Cl ions in carbon and gold foils

Abstract Equilibrium charge state distributions have been measured for 30–110 MeV Si ions in carbon and gold foils and 25–142 MeV Cl ions in carbon foils. Obtained values of mean charge states have been well reproduced by the empirical formula by Shima et al. in both ion energy dependence and foil Z 2 dependence. Asymmetric charge state distributions are in fairly good agreement with the prediction of the chi-squared model by Baudinet-Robinet.

Charge distribution width of heavy ions after passage through carbon foils

Abstract Equilibrium charge state distributions have been measured for 45–166 MeV Br ions after passage through carbon foils. Including the Br ion data, systematic investigation has been carried out for the charge distribution width ( d ) of various heavy ions (Z 1 ) over a wide range of projectile velocity ( v ). It is found that the variation of d as a function of v is closely related to the variation of projectile shell structure. Based on this concept, trials have been performed to present the expression of d values using new co-ordinates.

Charge states of fast heavy ions in glancing collisions with aligned atoms in single crystals

Abstract Spectroscopy of ion-induced secondary electrons emitted from single crystals allows observation of high-energy shadowing which is the initial stage of ion channeling. The high-energy shadowing effect is sensitive to short-range (∼ 0.1 A) screening of the ions nuclear charge by inner-shell electrons and, accordingly, reflects the charge states of the ions moving in the crystal. This article reports recent progress in the study of charge states of MeV/u ions in glancing collisions with crystal atoms.

Equilibrium charge fractions of 1 MeV/u Fe and Ni ions after passage through a carbon foil

Abstract Equilibrium charge fractions have been measured for 56 MeV 56Fe and 58Ni ions passing through a carbon foil to investigate the Z1-dependence of heavy ion charge states at 1 MeV/u.

Planar Shadowing of Fast Ion Beams in Si and Ge Crystals Bombarded with 5 keV Ar

We have measured shadowing patterns for Si and Ge crystals bombarded with 5 keV Ar+, using keV secondary electrons induced by 56 MeV O8+. In the planar shadowing patterns, the increase in the electron yield due to Ar+ bombardment can be directly related to the thickness of the damaged layer on the crystal surface, as previously found for axial shadowing. The results indicate that not only axial but also planar shadowing in the damaged crystals can be accounted for in terms of the effective target thickness responsible for the keV electron yield.

High-Sensitivity Channeling Analysis of Lattice Disorder Near Surfaces Using Secondary Electrons Induced by Fast Ions

Under the channeling condition of 56 MeV O8+, the sensitivity of keV secondary-electron yield to lattice disorder in crystals has been investigated for Si and Ge damaged with 5 keV Ar+, and for epitaxially grown CeO2 on Si and Si on sapphire. The analysis indicates that the ratio of channeling to random yield is a sensitive measure of displaced atoms whose areal density is equivalent to a nanometer-thick amorphous layer on a crystal surface. This technique enables low-density defect analyses where commonly used ion backscattering spectrometry is unapplicable.

Optimal foil material and thickness for the charge striping of heavy ions of around 100 MeV

Abstract In order to seek an optimal charge stripping material and its thickness for the charge stripping of heavy ions of around 100 MeV, the transmission of highly charged ions after passage through charge stripping foils has been measured using 95 MeV Cl ions. Tested foils are Be and C foils of various thicknesses. As a result, Be foils with several tens of μg/cm 2 are most efficient for the obtainment of highly charged ions whose charge states are higher than the most probable charge state. On the other hand, for the use of ions with the most probable charge state, there is no noticeable difference between the use of C and Be foils provided that their thicknesses are a few tends of μg/cm 2 .

The 12 UD pelletron accelerator at the University of Tsukuba

Abstract The 12 UD Pelletron installed at the Tandem Accelerator Center of the University of Tsukuba has been in operation for nearly four years. The installation of the accelerator is described and the operational experience with the accelerator and associate facilities are summarized.