Continuous tuning characteristics of a small high pressure uv preionised CO2 laser

The wavelength tuning characteristics of a compact uv preionised CO₂ laser operating at pressures in the range 8–12 atmospheres are reported. This laser, with a gain length of 16 cm, is demonstrated to have a continuous tuning range of 17 cm^-1 in the 10.4 μm P-branch and 12 cm^-1 in the R branch at 10 atmospheres.     

A topological proof of the bott periodicity theorems

Summary A proof is given of theBott periodicity theorems using only well known techniques of algebrdbc topology. To Enrico Bompiani on his scientific Jubilee. This research was done in part while the first author held a Sloan Foundation Fellowship and the second author held a Senior National Science Foundation Fellowhip. It was also supported in part by the National Science Foundation under contract number G-10369.     

Crystalline boron nanowires

Ideal nanowire interconnects for nanoelectronics will be refractory, covalently bonded, and highly conductive, irrespective of crystallographic orientation. Theoretical studies suggest that boron nanotubes should be stable and exhibit higher electrical conductivities than those of carbon nanotubes. We describe CVD growth of elemental boron nanowires, which are found to be dense nanowhiskers rather than nanotubes. Conductivity measurements establish that they are semiconducting, with electrical properties consistent with those of elemental boron. High conductivities should be achievable through doping.     

Sorption of 60Co on a synthetic titanosilicate analogue of the mineral penkvilksite-2O and antimonysilicate

The ability of two different types of synthetic inorganic ion-exchangers to sorb radioactive cobalt-60 using a batch-type method was studied. The two materials examined were the analogue of the natural titanosilicate penkvilksite-2O (AM-3) and a synthetic antimonysilicate. Ion-exchange experiments were performed with solutions labelled with radioactive cobalt (⁶⁰Co). The sorption of ⁶⁰Co onto the two samples materials were compared in terms of distribution coefficient (K _d), sorption percentage and cobalt quantity removed in mg per gram weight of the material. Several parameters were investigated viz. contact time, cobalt concentration, and sorbent concentration. It was found that the batch factor and cobalt concentration had a significant influence on the sorption of cobalt onto both of the materials. This was associated with the difference in pH generated by suspensions of the materials in water which was alkaline for the penkvilksite-2O analogue, and acid for the synthetic antimonysilicate.     

Simultaneous imaging of K-α radiation and coherent transition radiation from relativistic-intensity laser-irradiated solid target plasmas

Laser acceleration of hot electrons and their transport through 12-32 μm thick Ti foils was explored experimentally using two complementary diagnostics, a bent crystal imaging the Ti K_α emission and optical imaging of the coherent transition radiation (CTR) produced by the exit of the hot electrons from the foil. The spatial extent of the hot electron production measured by these two diagnostics is dramatically different. Electrons producing CTR emerge in a spot of less than 7 μm and appear to maintain a high degree of collimation during transport through the foil while electrons that produce K_α emission appear to diverge to sizes of 50-100 μm as viewed from the back surface of the foil. These results indicate that there is a large difference in the transport of the highest energy electrons contributing to CTR signal as compared with the bulk of the hot electron population generating K_α signal.     

Anion exchange in hydrous oxides

Commercially available synthetic hydrous oxides (Ferrox, Zirox, Alumina, Oxti, and Oxtain) have been used to study the sorption of some anionic species from simulated radioactive waste. Results of the analysis showed varying degrees of uptake for the anions in various media solutions. Sorption was most effective in the solution pH 2–7 range following the amphoteric nature of these materials. The presence of competing anions had a marked effect on the sorption properties of the material.