Modeling of steel spheres impacting polyethylene

The effect of shrapnel on target chamber components and experiments at large lasers such as the National Ignition Facility at LLNL and the Megajoule Laser at CESTA in France is an important issue in fielding targets and exposure samples. Modeling calculations are likely to be an important component of this effort. Some work in this area has been performed by French workers, who are collaborating with the LLNL on many issues relating to target chamber, experiment-component, and diagnostics survival. Experiments have been performed at the Phebus laser in France to measure shrapnel produced by laser-driven targets; among these shots were experiments that accelerated spheres of a size characteristic of some of the more damaging shrapnel. These spheres were stopped in polyethylene witness plates. The penetration depth is characteristic of the velocity of the shrapnel. Experimental calibration of steel sphere penetration into polyethylene was performed at the CESTA facility. The penetration depth has been reported (ref. 1) and comparisons with modeling calculations have been made (ref. 2). There was interest in a comparison study of the modeling of these experiments to provide independent checks of the calculations. This work has been approved both by DOE headquarters and by the French Atomic Energy Commission (CEA); it is task number 99-3.2 of the 1999 ICF agreement between the DOE and the CEA. Daniel Gogny of the CEA who is on a long-term assignment to LLNL catalyzed this collaboration. This report contains the initial results of our modeling effort

A Configurationally-Resolved-Super-Transition-Arrays method for calculation of the spectral absorption coefficient in hot plasmas

A new method, 'Configurationally-Resolved-Super-Transition-Arrays', for calculation of the spectral absorption coefficient in hot plasmas is presented. In the new method, the spectrum of each Super-Transition-Array is evaluated as the Fourier transform of a single Complex Pseudo Partition Function, which represents the exact analytical sum of the contributions of all constituting unresolved transition arrays sharing the same set of one-electron solutions. Thus, in the new method, the spectrum of each Super-Transition-Array is resolved down to the level of the (unresolved) transition arrays. It is shown that the corresponding spectrum, evaluated by the traditional Super-Transition-Arrays (STA) method [A. Bar Shalom, J. Oreg, W.H. Goldstein, D. Shvarts and A. Zigler, Phys. Rev. A 40, 3183 (1989)], is just the coarse grained Gaussian approximation of the Configurationally-Resolved-Super-Transition-Array. A new computer program is presented, capable of evaluating the absorption coefficient by both the new configurationally resolved and the traditional Gaussian Super-Transition-Arrays methods. A numerical example of gold at temperature 1keV and density 0.5 gr/cm^{3}, is presented, demonstrating the simplicity, efficiency and accuracy of the new method

The Berkeley Sample of Stripped-Envelope Supernovae

We present the complete sample of stripped-envelope supernova (SN) spectra observed by the Lick Observatory Supernova Search (LOSS) collaboration over the last three decades: 888 spectra of 302 SNe, 652 published here for the first time, with 384 spectra (of 92 SNe) having photometrically-determined phases. After correcting for redshift and Milky Way dust reddening and reevaluating the spectroscopic classifications for each SN, we construct mean spectra of the three major spectral subtypes (Types IIb, Ib, and Ic) binned by phase. We compare measures of line strengths and widths made from this sample to the results of previous efforts, confirming that O I {\lambda}7774 absorption is stronger and found at higher velocity in Type Ic SNe than in Types Ib or IIb SNe in the first 30 days after peak brightness, though the widths of nebular emission lines are consistent across subtypes. We also highlight newly available observations for a few rare subpopulations of interest.Comment: 13 pages; 14 figures; 3 tables. Accepted for publication in MNRA

Application of the extended P+QQ force model to N≈ZN \approx Z fp shell nuclei

To study collective motion, the extended pairing plus $QQ$ force model proposed recently is applied to $A$=46, 48 and 50 nuclei in the $fp$ shell region. Exact shell model calculations in the truncated model space $(f_{7/2},p_{3/2},p_{1/2})$ prove the usefulness of the interaction. The simple model with the pairing plus quadrupole pairing plus $QQ$ force and $J$-independent isoscalar proton-neutron force reproduces unexpectedly well observed binding energies, energy levels of collective (yrast) states and reduced $E2$ transition probabilities in $^{46}$Ti, $^{46}$V, $^{48}$V, $^{48}$Cr, $^{50}$Cr and $^{50}$Mn. The correspondence between theory and experiment is almost comparable to that attained by the full $fp$ shell model calculations with realistic effective interactions. Some predictions are made for energy levels and variations of $B(E2)$ in the yrast bands, in these nuclei. Characteristics of the interaction are investigated by comparing with the realistic effective interactions.Comment: 34 pages including 14 figure

The Lick AGN Monitoring Project: Reverberation Mapping of Optical Hydrogen and Helium Recombination Lines

We have recently completed a 64-night spectroscopic monitoring campaign at the Lick Observatory 3-m Shane telescope with the aim of measuring the masses of the black holes in 12 nearby (z < 0.05) Seyfert 1 galaxies with expected masses in the range ~10^6-10^7M_sun and also the well-studied nearby active galactic nucleus (AGN) NGC 5548. Nine of the objects in the sample (including NGC 5548) showed optical variability of sufficient strength during the monitoring campaign to allow for a time lag to be measured between the continuum fluctuations and the response to these fluctuations in the broad Hbeta emission, which we have previously reported. We present here the light curves for the Halpha, Hgamma, HeII 4686, and HeI 5876 emission lines and the time lags for the emission-line responses relative to changes in the continuum flux. Combining each emission-line time lag with the measured width of the line in the variable part of the spectrum, we determine a virial mass of the central supermassive black hole from several independent emission lines. We find that the masses are generally consistent within the uncertainties. The time-lag response as a function of velocity across the Balmer line profiles is examined for six of the AGNs. Finally we compare several trends seen in the dataset against the predictions from photoionization calculations as presented by Korista & Goad. We confirm several of their predictions, including an increase in responsivity and a decrease in the mean time lag as the excitation and ionization level for the species increases. Further confirmation of photoionization predictions for broad-line gas behavior will require additional monitoring programs for these AGNs while they are in different luminosity states. [abridged]Comment: 37 pages, 18 figures and 15 tables, accepted for publication in the Astrophysical Journa

Direct Analysis of Spectra of the Unusual Type Ib Supernova 2005bf

Synthetic spectra generated with the parameterized supernova synthetic-spectrum code SYNOW are compared to spectra of the unusual Type Ib supernova 2005bf. We confirm the discovery by Folatelli et al. (2006) that very early spectra (about 30 days before maximum light) contain both photospheric-velocity (8000 km/s) features of He I, Ca II, and Fe II, and detached high-velocity (14,000 km/s) features of H-alpha, Ca II, and Fe II. An early spectrum of SN 2005bf is an almost perfect match to a near-maximum-light spectrum of the Type Ib SN 1999ex. Although these two spectra were at very different times with respect to maximum light (20 days before maximum for SN 2005bf and five days after for SN 1999ex), they were for similar times after explosion - about 20 days for SN 2005bf and 24 days for SN 1999ex. The almost perfect match clinches the previously suggested identification of H-alpha in SN 1999ex and supports the proposition that many if not all Type Ib supernovae eject a small amount of hydrogen. The earliest available spectrum of SN 2005bf resembles a near-maximum-light spectrum of the Type Ic SN 1994I. These two spectra also were at different times with respect to maximum light (32 days before maximum for SN 2005bf and four days before for SN 1994I) but at similar times after explosion - about eight days for SN 2005bf and 10 days for SN 1994I. The resemblance motivates us to consider a reinterpretation of the spectra of Type Ic supernovae, involving coexisting photospheric-velocity and high-velocity features. The implications of our results for the geometry of the SN 2005bf ejecta, which has been suggested to be grossly asymmetric, are briefly discussed.Comment: Accepted by PAS

The (2j-1) rule with other interactions

We recently formulated a rule for isomeric states for a system of 4 nucleons with isospin T=1, namely that if the nucleons are in a single j shell then states with angular momenta J=2 and J=(2j-1) are either isomeric or ground states [ze12]. To show that this is a robust result, we here consider a new interaction from the literature that was used to discuss even-even and odd-even nuclei. We here apply it to an odd-odd nucleus.Comment: arXiv admin note: substantial text overlap with arXiv:1107.4068, arXiv:1112.480

The Peculiar SN 2005hk: Do Some Type Ia Supernovae Explode as Deflagrations?

We present extensive u'g'r'i'BVRIYJHKs photometry and optical spectroscopy of SN 2005hk. These data reveal that SN 2005hk was nearly identical in its observed properties to SN 2002cx, which has been called ``the most peculiar known type Ia supernova.'' Both supernovae exhibited high ionization SN 1991T-like pre-maximum spectra, yet low peak luminosities like SN 1991bg. The spectra reveal that SN 2005hk, like SN 2002cx, exhibited expansion velocities that were roughly half those of typical type Ia supernovae. The R and I light curves of both supernovae were also peculiar in not displaying the secondary maximum observed for normal type Ia supernovae. Our YJH photometry of SN 2005hk reveals the same peculiarity in the near-infrared. By combining our optical and near-infrared photometry of SN 2005hk with published ultraviolet light curves obtained with the Swift satellite, we are able to construct a bolometric light curve from ~10 days before to ~60 days after B maximum. The shape and unusually low peak luminosity of this light curve, plus the low expansion velocities and absence of a secondary maximum at red and near-infrared wavelengths, are all in reasonable agreement with model calculations of a 3D deflagration which produces ~0.25 M_sun of 56Ni.Comment: Accepted by PASP, to appear in April 2007 issue, 63 pages, 16 figures, 11 table