Experiments on the Z accelerator with deuterium gas-puff implosions have produced up to 3.7×1013 (±20%) neutrons at 2.34MeV (±0.10MeV). Although the mechanism for generating these neutrons was not definitively identified, this neutron output is 100 times more than previously observed from neutron-producing experiments at Z. Dopant gases in the deuterium (argon and chlorine) were used to study implosion characteristics and stagnated plasma conditions through x-ray yield measurements and spectroscopy. Magnetohydrodynamic (MHD) calculations have suggested that the dopants improved the neutron output through better plasma compression, which has been studied in experiments increasing the dopant fraction. Scaling these experiments, and additional MHD calculations, suggest that ∼5×1014 deuterium-deuterium (DD) neutrons could be generated at the 26-MA refurbished Z facility.

We report the first measurements of the polarization of x rays emitted from bound-bound transitions in a highly ionized He-like ion. Polarization was measured for the decay to the ground state, Is 2 'So, of the He-like Sc 19+ levels \slp l P\> \s2p 3 Pi, ls2p 3 Pi, and \s2s 3 S\. The measurements were made with the Electron Beam Ion Trap at two electron-beam energies: 4.36 and 5.62 keV. Polarization of two of the lines is strongly influenced by the hyperfine interaction with the Sc nucleus, demonstrating that polarization measurements can be used to investigate hyperfine interactions in highly ionized atoms.PACS numbers: 32.30. Rj, 34.80.Kw Evidence for the hyperfine interaction in He-like ions has been seen in beam-foil spectroscopy, where hyperfine effects were found 1 to explain the measured lifetime of the \s2p 3 P2 level in V 21+ . The hyperfine interaction can mix "pure" atomic levels, changing the level lifetimes and even allowing decay by an otherwise forbidden transition. The hyperfine interaction also effects the populations of magnetic sublevels, thus affecting the polarization of the radiation emitted when a state decays. Measurements of the polarization of line emission can be used to test the theory of the hyperfine interaction, as well as provide information relevant to the understanding of solar flares and tokamaks, 2 where nonthermal electron distributions can produce polarized radiation.We have measured, for the first time, the polarization of electric dipole (E\), magnetic dipole (Ml), and magnetic quadrupole (M2) emission lines emitted from a highly ionized He-like ion. The particular emission lines that were observed are the £1 resonance line 1J 21 SO\s2p ] P\, the M2 quadrupole line Is 2 l S 0 -ls2p 3 /> 2 , the E\ intercombination line Is 2 x S$-\s2p 3 P\, and the Ml line Is 2l So-ls2s 3 S\ in Sc 19+ . These transitions are known as w, x, j>, and z, respectively, 3 and are important for solar and tokamak plasma diagnostics. 4,5 The emission lines of Sc 19+ appear in the x-ray region near 2.9 A and were observed with a Bragg crystal spectrometer attached to the Lawrence Livermore National Laboratory Electron Beam Ion Trap (EBIT). Their energies 6 are shown on an energy-level diagram in Fig. 1.Sc 19+ was chosen because it was the He-like ion most suitable for polarization studies with our apparatus. The He-like Sc (Z=21) w = 2 to « = 1 lines fall at wavelengths 7 that correspond to Bragg angles of about 45° for the Ge(220) (2^=4.00 A) curved crystal installed in our Johann spectrometer. 8 Sc is monoisotopic with an / = y nuclear spin. The hyperfine interaction with the nuclear magnetic moment of Sc can influence the polarization of the atomic transitions.EBIT is described in detail elsewhere. 9,10 Briefly, ions are injected into a cylindrical electrostatic well approximately 2 cm long and 70 /zm in diameter. The ions are ionized to high charge states and collisionally excited by a tunable (in energy) electron beam. The electron beam is nearly monoenergetic with a width of 50 eV -1s2p 1 P, ...

Veloce is a medium-voltage, high-current, compact pulsed power generator developed for isentropic and shock compression experiments. Because of its increased availability and ease of operation, Veloce is well suited for studying isentropic compression experiments (ICE) in much greater detail than previously allowed with larger pulsed power machines such as the Z accelerator. Since the compact pulsed power technology used for dynamic material experiments has not been previously used, it is necessary to examine several key issues to ensure that accurate results are obtained. In the present experiments, issues such as panel and sample preparation, uniformity of loading, and edge effects were extensively examined. In addition, magnetohydrodynamic simulations using the ALEGRA code were performed to interpret the experimental results and to design improved sample/panel configurations. Examples of recent ICE studies on aluminum are presented.

We have obtained the first measurement of electron impact excitation cross sections as a function of energy for a highly charged ion. Collisional excitation cross sections to four w-2 levels of He-like titanium were measured from threshold to 1.7 times threshold. The data conform well to established theory, especially for direct excitation; however, significant differences are found with predicted contributions from resonance excitation and in the treatment of radiative cascades. The latter changes plasma temperatures inferred from titanium Ka line intensities by as much as a factor of 2.PACS numbers: 34.80.Dp, 34.80.Kw The interaction of electrons with highly charged, high-Z ions plays a primary role in understanding the physics of hot plasmas. Electron impact excitation (IE) cross sections and excitation rates of highly stripped ions are fundamental in the understanding of x-ray emission from inertial confinement fusion plasmas [1], the study of solar phenomena [2], and the diagnosis of tokamak plasmas [3]. Therefore, not only is a comparison between theory and experiment of IE cross sections of highly charged, high-Z ions crucial to the development of the physics of electron-ion interactions, but also of great practical importance. Measurements of IE cross sections as a function of energy have been reported recently for low ion charge states [4]; these investigations considered excitation to the first excited level only. For highly charged ions, there is one measurement of IE cross sections for neonlike barium, but only at two electron energy points [5]. We present the first measurements of IE cross sections of a highly charged, high-Z ion over a wide range of electron energy, allowing us to assess both electron-ion interaction cross sections as well as excitation rate calculations. This was done for ground-state excitation to the n=2 levels in heliumlike titanium Ti 20+ , which result in characteristic Ka x-ray emission lines used for diagnostics of Maxwellian and non-Maxwellian magnetic fusion plasmas [6,7].The measurements were carried out on the Livermore electron-beam-ion trap (EBIT) [5,8]. In the apparatus, low charge state ions were injected into and trapped inside the space charge of an intense (100-150 mA, 65 //m diam) electron beam. The ions were successively ionized to heliumlike and excited by the beam, which has an energy resolution of 50 eV FWHM. X-ray spectra centered on the n = 2 to n = \ transitions were taken simultaneously at 90° to the beam by a low-resolution germanium detector and a high-resolution von Hamos geometry Bragg crystal spectrometer capable of resolving the intercombination lines , 5'o-3 / > 2 at 4734 eV and , 5o-3 / > i at 4727 eV, as well as the forbidden line l S 0 -3 S\ at 4702 eV, and the resonance line , S 0 -, / > i at 4750 eV [9]. Gabriel has designated these lines respectively as x, y, z, and w[10].

Measured cross sections for single ionisation of Li-like N4+, O5+ and Ne7+ by electron impact are reported for energies from threshold to 2500 eV. The animated crossed beams method has been employed. In addition to direct ionisation, the 1s22s to 1s2l2l' excitation followed by autoionisation is shown to give a significant contribution to the total cross section, and its magnitude has been estimated for all three ions. Comparisons are made with other experimental results and different theoretical predictions. Cross sections for N4+ and O5+ are in a good agreement with previous results and the first result on Ne7+ ionisation is well reproduced by the Coulomb-Born calculations.