T. Azuma

Strong charge state dependence of H+ and H2+ sputtering induced by slow highly charged ions

Abstract Secondary ion emission has been studied for very slow (∼ 0.01 νB) highly charged Ar and N ions bombarding C60 containing hydrogen as an impurity. It is found that the fragmentations of C60 are very rare even for Ar16+ bombardments. On the other hand, the sputtering of H+ and H2+ has been observed to increase drastically as a function of incident charge q like qγ (e.g., γ ∼ 4.6 for H+ sputtering by 500 eV Arq+).

Development of 500 MHz muon spin resonance spectrometer

The 500 MHz muon resonance was newly developed. The system was constructed with 500MHz resonance cavity, pulsed high power RF-source and the superconducting helmholz coil. This system provide the oppotunity to achieve the diamagnetic muon spectroscopy at 37KG and 500MHz. Also muonic radical resonance and muonium resonance at magnetic field corresponding to the 500MHz resonance frequency. Some preliminary but important result was also reported.

Delayed formation of muon-containing species in organic liquids observed by spin resonance technique

The resonance technique has been applied to observe diamagnetic muons and, for the first time by the resonance, Mu-substituted radicals in organic liquids under strong decoupling magnetic fields. In benzoquinone solutions in benzene the relaxation of Mu-cyclohexadienyl radicals through reaction with quinone was directly observed by the radical resonance technique. The product of this reaction was then observed by the diamagnetic muon resonance as a slow formation. Similar slow formation was observed for diamagnetic muons in neat CS2 and for Mu-radicals in benzene and styrene. Such slow formation can never be observed by the rotation technique due to dephasing problem, and thus the previous method is expected to provide new source of information on slow reaction dynamics of muon containing species.

Production of Slow Positrons Using an Electron Linac

Intense pulsed slow-positron beams have been produced using electron linac beams of energy 25 MeV. Slow positorons were counted by complete separation from strong flashed signals produced directly by the primary electron pulsed beam. The yield of low-energy positrons was estimated as 2×106 slow positrons per second. The conversion efficiency of slow-positron production for 25 MeV electrons, e, was 2.4×10-8, much lower than the value obtained by Howell et al. Several methods of overcoming the difficulties of practical application were attempted, and are discussed in the paper.

Relativistic heavy collision studies at HIMAC: X-rays from radiative electron capture into continuum and secondary electrons from binary encounter collisions

Abstract We describe, in this paper, our recent results on two relativistic heavy ion collision experiments performed at Heavy Ion Accelerator for Medical Application in Chiba (HIMAC) facility, namely the X-rays resulting from the radiative electron capture into projectile continuum states and the secondary electrons produced in the binary encounter collisions (BEC).

New emission bands at high-density excitation of dense gas and liquid of helium irradiated by nitrogen ions

Abstract Dense helium, whose atomic separation is several A near 4 K, shows new emission bands following excitation by fast nitrogen ions. These new emissions can be classified into three groups, which grow and disappear stepwise with increasing pressure, accompanied with lifetime shortening except for a group at the highest density. They are explained as clusters of helium excimers.

L X-ray emission from slow multiply charged Ar ions bombarding Be and Al targets

Abstract Projectile L X-rays are observed for 18–260 keV Ar q + ions ( q =7 − 14) bombarding Be and Al targets. X-ray yields are found to increase with the L-shell hole number for q ≥ 9. The X-rays are shown to be emitted stepwise, which allows to disintegrate the spectra into the individual steps. It is found that 3s-2p transition is dominant in each step. Transitions from higher angular momentum states like 3d-2p and those from higher principal quantum numbers are relatively weak.

Measurements of soft X-rays in collision of slow multiply charged Ar ions with an amorphous C target

Soft X-rays were measured in collision of 1‐3 keV/u Ar qa (qa 2‐14) ions on an amorphous C target. Ar L X-rays due to initial L-shell holes were successfully decomposed. It was found that L-shell vacancies of Ar were filled stepwise primarily via 3s‐2p transition for each step. ” 1998 Elsevier Science B.V.

Secondary electron emission from a C-foil resulting from the passage of orientation selected He2+ molecular ions

Abstract We have measured the effect of the orientation of the molecular axis on average numbers and number distributions of multiply emitted secondary electrons (MUSE) from a very thin (∼ 50 A) carbon foil both in the forward and backward directions resulting from the passage of 1 MeV/u He2+ molecular ions. MUSE was observed in coincidence with a pair of outgoing He2+ ions detected 3.5 m downstream from the carbon foil. Average numbers of MUSE in the forward and backward directions per incident projectile are 11.5 and 7.5, respectively, when the orientation of the molecular axis is disregarded. Number distributions of MUSE are much wider than the Poisson distribution in any case. They are compared with those which are calculated from the data for 1 MeV/u He+ ions. A negative correlation of the number distributions of MUSE in the forward and backward directions was observed. The average number of MUSE in the forward directions is larger when the molecular axis is parallel to the beam direction than when it is perpendicular, but no orientation dependence was observed in the backward direction.

RECC and REC measurements for heavy ion impact on foil targets at relativistic energies

X-ray spectra have been observed for the collision system of bare C6+, Ne10+, Si14+ and Ar18+ ions of 75-290 MeV/u with Be and C foil targets. The radiative electron capture into continuum states (RECC) of these projectiles is always noticeable. For 75 and 150 MeV/u Ar18+, we can also observe a peak due to radiative electron capture into the K-shell (K-REC) in addition to RECC. A small ridge corresponding to K-REC is discerned also for 75 MeV/u Si14+. These features reflect the energy and projectile charge dependence of the intensities of RECC and REC x-rays. The observed edge energies of RECC and peak energies of REC are consistent with estimated values based on energy conservation. The observed absolute intensities of these components are also compared with calculations.