372596238

RIKEN Accel. Próg. Rep. 24 (1990)

IH-2-14. Angular Distribution Measurement of K-X Rays Emitted

from an Ar Beam Passing through C Foil

T. Papp, Y. Awaya, A. Hitachi, T. Kambara, Y. Kanai, and T. Mizogawa

2000

In ion-solid foil interaction, the symmetry of the collision geometry is reflected in the angular and polarization distribution of collision-induced fluorescence. When the beam axis coincides with the axis of the normal to the foil, in beam-foil spectroscopy, the collision geometry has cylindri-cal symmetry. When the foil is tilted with respect to the beam axis, the collision geometry loses its axis of symmetry. This lower degree of symmetry is mirrored by a correspondingly lower degree of symmetry in the angular distribution of emitted radiation.^1,2)

4000

Wave!ength(Channel)

Fig. 1. Ka-satellite X-ray spectrum of Ar measured at 30\ relative to the incoming beam, when the foil was tilted by 45° with respect to the beam axis.

In the experiment, a 1 MeV/u Ar beam obtained from the RILAC was passed through a carbon foil target of 20 /*g/cm² in thickness. Angular distributions of Ar KL” X-ray lines were measured at two target angles, tilted at 90° and 45° relative to the beam direction. The spectra of Ar X rays were measured with a broad-range crystal spectrometer³⁾ using a fiat Ge (111) crys-tal with a Bragg angle at its center 20 = 76°. The spectra were fitted by a quadratic background and an appropriate number of pseudo-Voigt peaks simultaneously, by using a Computer codę EWA.⁴⁾ The spectra were analyzed by a Gaussian-peak shape too, and a better fitting was obtained when a pseudo-Voigt peak shape was used. From the analysis the intensity ratio of the well resolved peaks were determined as a func-tion of the detection angle. At a 90° target angle, all the ratios were found to be isotropic within error limits. At a 45" target angle the ³Pi/¹Pi intensity ratio had a definite anisotropy.

Fig. 2. Intensity ratio of the T, and ³P, transitions as a function of the detector angle. o, beam axis was per-pendicular to the foil surface; •, angle of beam axis and foil was 45°. The linę is drawn to guide the eyes.

References

1) J. Macek and D. Burns: Beam Foil Spectroscopy (ed. S. Bashkin), Springer Verlag, Berlin, Heidelberg, and New York, p. 237 (1976).

2) D. A. Church, R. A. Kenefick, D. - W. Wang, and R. L. Watson: Phys. Rev., A26, 3093 (1982).

3) A. Hitachi, H. Kumagai, and Y. Awaya: Nuci. In* strum. Methods, 195, 631 (1982).

4) J. Vegh: Thesis ATOMKI Debrecen 1990 (unpub-lished).