This paper is a comprehensive review of the state-of-knowledge in the field of radiation effects in glasses that are to be used for the immobilization of high-level nuclear waste and plutonium disposition. The current status and issues in the area of radiation damage processes, defect generation, microstructure development, theoretical methods and experimental methods are reviewed. Questions of fundamental and technological interest that offer opportunities for research are identified.

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We describe portable software to simulate universal quantum computers on massive parallel computers. We illustrate the use of the simulation software by running various quantum algorithms on different computer architectures, such as a IBM BlueGene/L, a IBM Regatta p690+, a Hitachi SR11000/J1, a Cray X1E, a SGI Altix 3700 and clusters of PCs running Windows XP. We study the performance of the software by simulating quantum computers containing up to 36 qubits, using up to 4096 processors and up to 1 TB of memory. Our results demonstrate that the simulator exhibits nearly ideal scaling as a function of the number of processors and suggest that the simulation software described in this paper may also serve as benchmark for testing high-end parallel computers.

The near-surface nucleation and crystallization behavior of Ag+ ion-implanted lithia-alumina-silica glasses has been studied. For room-temperature Ag implants, crystallization of the glass ceramic phase was prevented by dissolution of Ag precipitates and migration of Ag atoms at temperatures below that necessary for formation of the glass ceramic phase. Crystallization was demonstrated after low-temperature or low-dose-rate implantations. Optical spectroscopy was used to monitor the size of colloidal Ag particles and to detect the presence of the crystalline phase. Rutherford backscattering spectroscopy (RBS) was used to obtain the depth distribution of Ag atoms in the glass and thus monitor Ag migration. For samples implanted at room temperature and at relatively high dose rates (∼1 μA/cm2), aggregation of the Ag atoms into colloids occurred during implantation and also during subsequent annealing to temperatures ?350 °C. The RBS spectra indicate some migration of the Ag to the surface at these temperatures. For annealing temperatures ≳350 °C, both optical and RBS measurements show that Ag is lost from the glass surface. The initial spatial distribution of the Ag for these high-dose-rate room-temperature implantations was distorted by interactions with the associated damage and possibly by local electric fields caused by neutralization of the implanted ions. It was possible to obtain dispersed Ag nuclei by implanting at low sample temperatures (80 K) or at low beam current (∼200 nA/cm2) to reduce ion-beam heating. Although some migration to the surface was seen in these samples, it occurred at higher temperatures and crystalline precipitation was achieved by annealing at 500 °C.

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