Dose indicators such as the computed tomography dose index (CTDI) and dose-length product (DLP) were gathered for all routine abdomen-pelvis, chest and head examinations performed on all computed tomography (CT) scanners at a University Health Center (UHC) in Canada. These indicators were analysed and compared with the range of diagnostic reference levels (DRLs) suggested by Health Canada and with DRLs in other countries. Mean DLP values varied from one scanner to another, but mean values at the UHC (750 mGy cm(-1) for abdomen-pelvis CT, 349 mGy cm(-1) for chest CT and 1181 mGy cm(-1) for head CT) were all below the upper limit of the range of DRLs suggested by Health Canada. Local DRLs at the UHC were set to 810 mGy cm(-1) for abdomen-pelvis CT, 345 mGy cm(-1) for chest CT and 1205 mGy cm(-1) for head CT. Results, however, show the need for protocols revisions, since some scanners exhibit mean DLP values slightly below or above the upper limit of the range of DRLs suggested by Health Canada.

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The areal density of extended defects in P-implanted and annealed Si is observed to increase with ion dose to the power 8. A simple model based on Poisson statistics applied to point defects created during ion implantation shows that such a dependence corresponds to enhanced stability of interstitial clusters consisting of at least eight interstitial atoms, and it implies an interstitial “clustering” radius of 0.8 nm. The direct observation of “n=8” confirms the curious behavior observed earlier in transient-enhanced diffusion of B in Si, and provides a quantitative explanation of the threshold dose for the formation of extended defects in ion-implanted Si.

The optical and structural properties of ion-implanted 6H-SiC single crystals were investigated for samples implanted with 370 keV 28 Si ions to doses ranging from 5 × 10 13 to 1 × 10 16 cm −2 and at irradiation temperatures ranging from 20 to 600 • C. Rutherford backscattering spectrometry channelling (RBS/C) showed that the dynamic recovery of the induced-damage layer increases with irradiation temperature. The final disorder determined from RBS/C as a function of implantation temperature was modelled in terms of a thermally activated process which yielded an activation energy of 0.08 eV. Defect distributions are found to shift to greater depths with increasing implantation temperature and dose. Some defects are even found farther than the accessible range of the implanted ions. RBS/C data on high-temperature implantations also suggests that defect complexes are created at high doses in addition to the point defects that are still stable at high temperature. A decrease in Raman intensity of implanted samples relative to that of crystalline samples was observed and correlated with an increase in optical absorption near the wavelength of the laser pump (514.5 nm).