Fast ignition of fusion targets by laser-driven electrons

We present hybrid PIC simulations of fast electron transport and energy deposition in pre-compressed fusion targets, taking full account of collective magnetic effects and the hydrodynamic response of the background plasma. Results on actual ignition of an imploded fast ignition configuration are shown accounting for the increased beam divergence found in recent experiments [J.S. Green et al., Phys. Rev. Lett. 100, 015003 (2008)] and the reduction of the electron kinetic energy due to profile steepening predicted by advanced PIC simulations [B. Chrisman et al. Phys. Plasmas 15, 056309 (2008)]. Target ignition is studied as a function of injected electron energy, distance of cone-tip to dense core, initial divergence and kinetic energy of the relativistic electron beam. We found that beam collimation reduces substantially the ignition energies of the cone-guided fuel configuration assumed here.Comment: 15 pages, 9 figures. accepted for publication in Plasma Physics and Controlled Fusio

Reliable random error estimation in the measurement of line-strength indices

We present a new set of accurate formulae for the computation of random errors in the measurement of atomic and molecular indices. The new expressions are in excellent agreement with numerical simulations. We have found that, in some cases, the use of approximated equations can give misleading line-strength index errors. It is important to note that accurate errors can only be achieved after a full control of the error propagation throughout the data reduction with a parallel processing of data and error frames. Finally, simple recipes for the estimation of the required signal-to-noise ratio to achieve a fixed index error are presented.Comment: 9 pages, LaTeX file + 5 PostScript figures, psfig.sty and laa-s.sty required, to be published in Astronomy & Astrophysics Supplement Serie

A Plasma Instability Theory of Gamma-Ray Burst Emission

A new theory for gamma-ray burst radiation is presented. In this theory, magnetic fields and relativistic electrons are created through plasma processes arising as a relativistic shell passes through the interstellar medium. The gamma-rays are produced through synchrotron self-Compton emission. It is found that shocks do not arise in this theory, and that efficient gamma-ray emission only occurs for a high Lorentz factor and a high-density interstellar medium. The former explains the absence of gamma-ray bursts with thermal spectra. The latter provides the Compton attenuation theory with an explanation of why the interstellar medium density is always high. The theory predicts the existence of a class of extragalactic optical transient that emit no gamma-rays.Comment: Presented at the 20 Texas Symposium on Relativistic Astrophysics, December 1998, Paris, France. To appear on the proceedings compact dis

Aggregation of metallochlorophylls - Examination by spectroscopy

Nuclear magnetic resonance measurements determine which metallochlorophylls, besides magnesium-containing chlorophylls, possess coordination aggregation properties. Infrared spectroscopy reveals that only zinc pheophytin and zinc methyl pheophorbide showed significant coordination aggregation, whereas divalent nickel and copper did not

Experimental demonstration of quantum state tomography and qubit-qubit interactions for rare-earth-ion based solid state qubits

We report on the implementation of quantum state tomography for an ensemble of Eu$^{3+}$ dopant ions in a \YSO crystal. The tomography was applied to a qubit based on one of the ion's optical transitions. The qubit was manipulated using optical pulses and measurements were made by observing the optical free induction in a phase sensitive manner. Fidelities of $>90$% for the combined preparation and measurement process were achieved. Interactions between the ions due to the change in the ions' permanent electric dipole moment when excited optically were also measured. In light of these results, the ability to do multi-qubit quantum computation using this system is discussed

Induction of Mutations in a Bacterial Virus

In the course of experiments designed for other purposes a paradoxical observation was made: phage λ, inactivated by UV irradiation, when adsorbed onto sensitive bacteria was reactivated when a further dose of UV was given to the phage-bacterium complexes. Among the reactivated phages a fairly large proportion were mutants. A description of these findings and a discussion of their implications will be found below