Fumio Fukuzawa

Charge-changing contribution to energy loss of 32 MeV 3He+ in the charge state non-equilibrium region☆

Abstract Energy losses of 32 MeV 3 He ions by carbon foils were measured in the charge state non-equilibrium region. The mean energy losses exhibited an abrupt change as a functiion of the foil thickness around 40–50 μg/cm 2 . This behavior is quantitatively explained by considering the contribution from charge-changing collisions.

Single-, Double- and Triple-Electron Capture Cross Sections for Multicharged Slow Carbon Ions in H2, CH4, C2H6, C3H8 and CO2 Molecules

Cross sections have been measured for single, double and triple electron capture by C q + ( q =1–4) ions from H 2 , CH 4 , C 2 H 6 , C 3 H 8 and CO 2 molecules in the energy range of (1–20) q keV. The cross sections obtained here exhibit little dependence on the incident energy. Compared with the previous scaling laws, the present cross sections revealed a much stronger dependence on the first ionization potential of the molecules. For hydrocarbon molecules including H 2 all the cross sections show a remarkable linearity on the number of compositeatoms. The single electron capture cross sections σ q , q -1 are compared with the classical over barrier model and with the Olson model which was slighty modified so as to be applied to the molecular targets.

Target temperature dependence of charge state distributions of fast He ions emerging from solids

Abstract We have measured the charge state distributions of fast helium ions backscattered from various thick targets which are kept at high temperature. For metal targets the charge state distributions start to change at about 400°C and reach equilibrium at about 800°C. Furthermore, it has been also found that these equilibrated charge state distributions at high temperature depend strongly on the target materials. We have assumed that the variation of charge state distributions at various temperatures corresponds to the variation of the thickness of the contaminating layer of light atoms and have estimated the thickness of the adsorbed layer on the target surface at different temperatures. Measurements have also been made for Bi and Sn targets in liquid states.

Zt dependence of equilibrium charge state distributions of MeV He ions emerging from solid

The equilibrium charge state distributions of He ions emerging from various solid targets were measured in the energy range 0.6-2.4 MeV. Atomically clean target surfaces were prepared by continuous evaporation for Ga, Ge, Se and In, and by heating for Sc, Fe, Ta, W and Pt. The measured charge fractions Fi (i=0, 1, 2) were tabulated at 0.2 MeV intervals. In this energy range, the ratio F1/F2 is represented fairly well by the empirical formula AE-B, where E is the energy and A and B are target-dependent constants. The present data, together with the previous data, show clearly oscillatory behaviour of the equilibrium mean charge of He ions with target atomic number Zt. This oscillation is found to be attributed to the shell structure of the target atom.

Electron-loss cross-section measurement of 3He ions by the attenuation method

Abstract We have measured single-electron loss cross sections of 3 He 1+ ions for various solid targets such as C, Al, V, Cr, Cu, Ge, Nb, Ag, Sn and Au at 72 MeV by using the attenuation method. In this method residual 3 He 1+ fractions after charge-changing collisions were measured with a 3 He 1+ incident beam. Concentrations of contaminating atoms in the target were determined by an independent RBS measurement. It was found that surfaces of almost all the targets were covered with thin oxygen layers by which 3 He 1+ fractions were reduced by about 10%. Corrections of the observed loss cross sections are made for the surface oxygen layers.

Equilibrium charge state distributions of MeV He ions backscattered from continuously evaporated targets

The equilibrium charge state distributions of He ions emerging from surfaces of Pb, Sn and Al targets were measured in the energy range 0.8-2.3 MeV. Fresh surfaces of these targets were prepared by continuous evaporation during the measurement. As the evaporation rate was increased, charge state distributions changed gradually and reached the equilibrium ones which were characteristic of the respective targets. The results were compared with the calculation based on the gas model using Bohrs cross sections. The present data support oscillatory behaviour of mean charge with increasing target atomic number.

Equilibrium charge state distributions of 14N and 20Ne ions emerging from solids

Abstract We have developed a new technique of backscattering method for the measurement of equilibrium charge state distributions of ions emerging from a solid medium. By this method, equilibrium charge fractions for nitrogen in the energy range from 0.8 to 1.7 MeV and for neon from 1.5 to 4.4 MeV have been measured. The influence of inner shell vacancies produced by violent collisions on the charge state equilibrium is discussed.

Equilibrium Charge Distributions of Helium Beams in Various Gases

Equilibrium charge distributions of 0.7–2.0 MeV helium beams have been measured in target gases H 2 , He, N 2 , O 2 , CO 2 , CH 4 , C 2 H 6 and C 3 H 8 . Present results are in fairly good agreement with other experimental data in H 2 , He and N 2 . Absence probabilities of bound electrons in He 0 and He + projectiles are estimated by using the equilibrium fractions and the theory of Dmitriev is supportable in this energy region. Average charges in these gases have the following relation; \bar q : H 2 >CH 4 \(\cong\)C 3 H 8 >C 2 H 6 >N 2 >CO 2 >O 2 >He. T h e m a x i m u m d i f f e r e n c e o f q a m o n g t h e s e g a s e s i s a b o u t 0.27 u n i t s o f c h a r g e . T h e h i g h a v e r a g e c h a r g e s i n h y d r o g e n - c o n t a i n i n g m o l e c u l e s a r e a t t r i b u t e d t o t h e s m a l l c a p t u r e c r o s s s e c t i o n s .

Single electron loss cross sections oF 3He1+ ions for solid targets at 52, 62 and 72 MeV

Abstract Single electron loss cross sections of 3He1+ ions for solid targets of C, Cu, Ge, Sn and Au were measured at 52, 62 and 72 MeV using the growth method. The free electron collision model for single electron atoms has been extended to all targets and the corresponding calculations have been carried out. The results give fairly good agreement with the experimental values. Results are also compared with other current theories.

Electron capture from K shells in Cu and Ge by 72, 62 and 52 MeV 3He2+ beams

Abstract A magnetic spectrograph designed for high precision nuclear spectroscopy has been successfully applied to the study of electron capture. By using 72, 62 and 52 MeV 3 He 2+ ions on Cu and Ge target atoms, K shell electron capture was observed well separated from higher shell electron capture. Results are compared with theoretical predictions.