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Previous work has demonstrated that fluorophosphate (FP) glasses doped with trivalent samarium (Sm3+) can be used as a dosimetric detector in microbeam radiation therapy (MRT) to measure high radiation doses and large dose variations with a resolution in the micrometer range. The present work addresses the use of intense optical radiation at 405nm to erase the recorded dose information in Sm3+-doped FP glass plates and examines the underlying physics. We have evaluated both the conversion and optical erasure of Sm3+-doped FP glasses using synchrotron-generated high-dose x-rays at the Canadian Light Source. The Sm-ion valency conversion is accompanied by the appearance of x-ray induced optical absorbance due to the trapping of holes and electrons into phosphorus-oxygen hole (POHC) and electron (POEC) capture centers. Nearly complete Sm2+ to Sm3+ reconversion (erasure) may be achieved by intense optical illumination. Combined analysis of absorbance and electron spin resonance measurements indicates that the optical illumination causes partial disappearance of the POHC and the appearance of new POEC. The suggested model for the observed phenomena is based on the release of electrons during the Sm2+ to Sm3+ reconversion process, the capture of these electrons by POHC (and hence their disappearance), or by PO groups, with the appearance of new and/or additional POEC. Optical erasure may be used as a practical means to erase the recorded data and permits the reuse of these Sm-doped FP glasses in monitoring dose in MRT. [ABSTRACT FROM AUTHOR]

We report the photoluminescence and x-ray luminescence of lanthanum-stabilized cubic barium chloride with europium (Eu2+) doping, of general composition Ba1-x-yEuyLaxCl2+x. X-ray diffraction patterns confirm that the material adopts a cubic fluorite structure for x=0.125 and 02+ substituting for Ba2+ giving a site of cubic symmetry, based on the excitation spectra which show a T2g band and Eg band similar to those in cubic SrCl2:Eu. The 420 nm band has a very different lifetime and excitation spectrum and is assigned to Eu2+ ions which have an associated chlorine interstitial ion. The two bands are also found in the x-ray luminescence spectra. For both bands, and an additional minor emission at 520 nm found only at low temperatures and for high Eu concentrations, there is a common excitation in the UV from 150 to 200 nm which we attribute to excitons associated with the high concentration of chlorine interstitials. ESR measurements support a two-site model for the interpretation of the optical spectra. A measurement of the x-ray luminescence intensity compared to a standard commercial Gd2O2S:Tb phosphor sheet shows approximately equal brightness. [ABSTRACT FROM AUTHOR]

The nanoporous surfaces that can be produced by ion implantation of helium into metals have considerable potential for applications. The structures are characterised by random nanoscale cavities of uniform size, a high degree of swelling and very thin metal "walls" separating the neighbouring cavities. These structures are "seeded" by an earlier stage - a gas-bubble superlattice -- comprising small helium bubbles again of uniform size (∼ 2 nm diameter) ordered on a space lattice having the same symmetry as the host. For the fcc metals the bubble superlattice always contains structural variants -- that is, regions where the ordered bubble array has an orientation that is rational with, but different from, that of the crystal lattice of the host metal. In contrast for bcc metals previous work has suggested that the bubble lattice aligns solely parallel with the host crystal. Here we report the first clear demonstration of the presence of structural variant bubble lattices in a bcc metal. A combination of techniques including helium depth-profiling using HERDA is enabling the helium dose requirements for producing ordered bubble structures to be investigated more closely. These techniques are reviewed. [ABSTRACT FROM AUTHOR]