The ground state and several excited states of 9 He, the most neutron-rich nucleus to date, have been identified by means of the reaction 9 Be(/r~,/r + ) 9 He. The mass excess of the ground state has been measured and it is found that the nucleus is unbound against single-neutron decay by 1.13 ±0.10 MeV only. It is found that the excited-state spectrum of this nucleus, which is very far from the valley of stability, is in good agreement with the predictions of "no-core" shell-model calculations whose parameters were optimized for the stable nuclei in the valley.

Data are presented on the energy and angle dependence of the charge-symmetry superratio R and simple ratios r I and r2 for~-elastic scattering from H and He. r i and r2 were normalized with respect to~+ d and m d elastic scattering, which is assumed to have the ratio 1.0. The beam energies are T =142, 180, and 220 MeV, and the scattering angle, |9L, ranges from 40' to 110. In all cases measured it is found that R ) 1, r', =1, and r2) 1. These results provide substantial evidence for charge-symmetry violation. The angular distributions for a -H and m -He elastic scattering also have been measured and comparisons are made with various model calculations. R:cr(0)[sr+ H]o'(0)[tr 3H]/cr(0)[n He]o'(8)[sr+ He], r', =o(0)[~+ 'H]cr(0)[vr d]/o(0)[m. 'He]cr(0)[vr+d], r'2 =o{0)[n H]cr(0)[m+d]/o. (0)[m+ 3He]cr(0)[vr d].

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The Gamma-to-Electron Magnetic Spectrometer (GEMS) diagnostic is designed to measure the prompt γ-ray energy spectrum during high yield deuterium-tritium (DT) implosions at the National Ignition Facility (NIF). The prompt γ-ray spectrum will provide "burn-averaged" observables, including total DT fusion yield, total areal density (ρR), ablator ρR, and fuel ρR. These burn-averaged observables are unique because they are essentially averaged over 4π, providing a global reference for the line-of-sight-specific measurements typical of x-ray and neutron diagnostics. The GEMS conceptual design meets the physics-based requirements: ΔE/E = 3%-5% can be achieved in the range of 2-25 MeV γ-ray energy. Minimum DT neutron yields required for 15% measurement uncertainty at low-resolution mode are: 5 × 10(14) DT-n for ablator ρR (at 0.2 g/cm(2)); 2 × 10(15) DT-n for total DT yield (at 4.2 × 10(-5) γ/n); and 1 × 10(16) DT-n for fuel ρR (at 1 g/cm(2)).

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