Channeling studies of radiation damage in sodium chloride crystals

A Two-accelerator Facility and Its Use for Radiation Damage Studies in Alkali Halides

“…At a dose near 10 16 cm -2, all three processes change. The back scattering decreases: this has been attributed (Newton et al 1976) to agglomeration of point defects to form linked clusters with (100) axial symmetry, a mechanism observed earlier by Hobbs et al ( ,1973 in electron microscope studies. The CI X-ray intensity also decreases, but begins to progressively fluctuate, whereas the optical absorption rises, as shown in Figs 3c and 3d.…”

“…In this work, a study of backscattering alone was undertaken. As will be seen from the discussion in earlier work (Newton et al 1976), this provides the most ready understanding of the damage mechanism. One possible source of difference between the damage due to 4He and 16 0 beams lies in the wellknown distinction of energy loss processes between electronic and nuclear phenomena (Lind hard et al 1963).…”

“…A discussion of the mechanism of damage by 1 MeV 4He ions, as displayed in Fig. 5a, has been given by Newton et al (1976). It is of interest here to attempt to relate that mechanism to the observed damage in the same (NaCl) crystal with 60 MeV 16 0 ions.…”

“…The sub-assembly for channeling and in-beam optical absorption studies (Newton et al 1976) was mounted on the target-chamber base. The target support was built into a McLean 3-axis goniometer with stepping motors providing angular increments of 0'01°.…”

“…In previous studies of helium-ion induced radiation damage in single crystals (Newton et al 1976), it has been shown that channeling, characteristic X-ray production and optical ~ absorption provide useful information on some details of the damage mechanism. It was shown that the observed backscattering of a beam aligned to a crystal axis provides a powerful method of interpreting the dechanneling due to radiation damage.…”