Quasistatic Bubble Propagation in 1.5 μm Period Ion-Implanted Tracks for 64 Mbit Magnetic Bubble Memory Devices
Ion-implanted tracks with a 1.5 μm period for use in 64 Mbit magnetic bubble memory devices have been fabricated and operated. The bubble material used was (BiSmLu)3 (FeAl)5O12 garnet film, supporting 0.45 μm bubbles. The resist mask patterns for implantation were formed using a 1/10 reduction projection aligner, using rectangular patterns on a reticle. The bubble propagation tracks were fabricated by double deuterium implantation and annealed at 400°C for 30 minutes, with an SiO2 layer deposited on the garnet surface to stabilize the implanted layer. An operating bias field margin in excess of 7% was stably obtained in quasistatic bubble propagation. This shows that the ion-implanted devices have great potential for use in 64 Mbit magnetic bubble memory devices.
Bi‐Sc doped bubble garnets supporting 0.35‐μm diameter bubbles
Garnet films of (BiSmLu)3(FeSc)5O12 supporting very small diameter (≲0.4 μm) bubbles have been grown on (111) oriented Nd3Ga5O12 substrates by liquid phase epitaxy. The saturation induction 4πMs is increased up to 2100 G by doping Sc in the octahedral site and Bi in the dodecahedral site. At the composition of Bi0.5Sm1.6Lu0.9Fe4.9Sc0.1O12, 4πMs is 2040 G and the bubble diameter can be decreased to 0.35 μm. The anisotropy energy Ku is 2.73×105 erg/cm3 and the quality factor Q (=Ku/2πMs2) is 1.65. Both Sm–Lu pair and Bi contribute to Ku. Bubbles with 0.35‐μm diam are considered to be the smallest possible in garnets since 4πMs can hardly exceed 2100 G.
Impact of Nuclear Data Uncertainties on Transmutation of Actinides in Accelerator-Driven Assemblies
Abstract The potential impact of nuclear data uncertainties on a large number of performance parameters of reactor cores dedicated to the transmutation of radioactive wastes is discussed. An uncertainty analysis has been performed based on sensitivity theory, which underlines the cross sections, the energy range, and the isotopes that are responsible for the most significant uncertainties. To provide guidelines on priorities for new evaluations or validation experiments, required accuracies on specific nuclear data have been derived, accounting for target accuracies on major design parameters. The required accuracies (mostly in the energy region below 20 MeV), in particular for minor actinide data, are of the same order of magnitude of the achieved accuracies on major actinides. Specific requirements also concern the improvement of minor actinide data related to decay heat and effective delayed-neutron fraction assessment.