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AbstractNeutron fluences have been measured from 155 MeV/nucleon 4He and 12C ions stopping in an Al target at laboratory angles between 10 and 160 deg. The resultant spectra were integrated over angle and energy above 10 MeV to produce total neutron yields. Comparison of the two systems shows that approximately two times as many neutrons are produced from 155 MeV/nucleon 4He stopping in Al and 155 MeV/nucleon 12C stopping in Al. Using an energy-dependent geometric cross-section formula to calculate the expected number of primary nuclear interactions shows that the 12C + Al system has, within uncertainties, the same number of neutrons per interaction (0.99 ± 0.03) as does the 4He + Al system (1.02 ± 0.04), despite the fact that 12C has three times as many neutrons as does 4He. Energy and angular distributions for both systems are also reported. No major differences can be seen between the two systems in those distributions, except for the overall magnitude. Where possible, the 4He + Al spectra are compared with previously measured spectra from 160 and 177.5 MeV/nucleon 4He interactions in a variety of stopping targets. The reported spectra are consistent with previously measured spectra. The data were acquired to provide data applicable to problems dealing with the determination of the radiation risk to humans engaged in long-term missions in space; however, the data are also of interest for issues related to the determination of the radiation environment in high-altitude flight, with shielding at high-energy heavy-ion accelerators and with doses delivered outside tumor sites treated with high-energy hadronic beams.

A systematic study of the dependence of the critical temperature on the superconducting carrier density, as measured byμ+SR, was carried out for a variety of cuprate oxides. We have shown that substitution of Pb for Bi and La for Sr result in well pinned vortex lattices in Bi2Sr2CaCu2Ox, and studied (BiPb)-2212 from the underdoped to the slightly overdoped regime. We also found that Tl-1212 samples, which have optimal maximumTc=108 K, trace a separate line with parameters comparable to overdoped Tl-2223 at the maximum. These data, together with data on Y-124/247, Tl-2201 and other cuprates result in an larger set of “universal correlations” between Tc andσ(0) ∞ns/m* for the high temperature superconductors.

Three distinct electronic states were detected for positive muons (µ+) after implantation into a C60 powder sample. About 40% of the µ+ remained in the bare (“diamagnetic”) state, essentially an interstitial charged point particle. The rest of the muons were found to thermalize predominantly in two muonium (Mu=µ+ e-) atomic species. A “vacuum” Mu state, with hyperfine coupling close to that of free Mu, most likely at the molecular center, and a muonic substituted radical, i.e. a hydrogen-like Mu addition to double bonds on the carbon rings. This opens up a rich subfield of fullerene spectroscopy using muons.