[en] In the proposed instrument, sample ions are continuously injected into a small racetrack-shaped ring where they are stored for several orbits as the undesired species are removed. This multistaged separation technique has three elements. First, the ions are mass separated by two 180⁰ bending magnets. After this first stage of enrichment the ions are neutralized in a charge exchange cell. The beam is then reionized by a laser before it passes back into the magnets for the second time to be further concentrated. After the desired degree of enrichment is attained, the ions are directed to a particle multiplier. An essential feature of the charge exchange stage is that the cell is electrically isolated and maintained at a potential of ≅75V. This decelerates the ion beam each time it enters the cell and leads to a physically discrete orbit for each pass through the system. The discrete orbits prevent contamination of highly purified ions by ions which have not yet been enriched to the same degree. The end result is that ions of the desired species follow a decaying spiral path until they are intercepted by the detector. The use of multiple orbits results in very high rejection of adjacent isotopes as well as reducing contamination due to low-angle scattering. The charge exchange gas is rubidium, which has a large near-resonant cross section for transfer of an electron into the first excited state of krypton which is metastable with respect to the ground state. From this excited state krypton is easily photoionized by a two-photon transition through a resonant intermediate p state to an ns or nd autoionizing level. In contrast to conventional mass spectrometers, the resonant charge exchange and photoionization processes virtually eliminate isobaric and molecular interferences

[en] A new instrument is being developed for ultrasensitive isotope analysis that combines magnetic mass selection, resonant charge exchange, and laser reionization. For krypton, this technique is expected to achieve isotope abundance sensitivities better than 10^-12. (author)

[en] We have observed ionization of Mg by both direct and stepwise two-photon excitation of the 3p²¹S state. The line shape of the single-color direct process is strongly modified by the resonance denominator associated with the intermediate virtual state. The measured energy and width of this resonance as determined by the stepwise two-color technique agree well with previous determinations

[en] The National Ignition Facility (NIF) is a 192-beam laser facility presently under construction at Lawrence Livermore National Laboratory. When completed, NIF will be a 1.8-MJ, 500-TW ultraviolet laser system. Its missions are to obtain fusion ignition of deuterium-tritium plasmas in ICF (Inertial Confinement Fusion) targets and to perform high energy density experiments in support of the U.S. nuclear weapons stockpile. The NIF facility will consist of 2 laser bays, 4 capacitor areas, 2 laser switchyards, the target area and the building core. The laser is configured in 4 clusters of 48 beams, 2 in each laser bay. Four of the NIF beams have been already commissioned to demonstrate laser performance and to commission the target area including target and beam alignment and laser timing. During this time, NIF has demonstrated on a single-beam basis that it will meet its performance goals and has demonstrated its precision and flexibility for pulse shaping, pointing, timing and beam conditioning. It also performed 4 important experiments for ICF and High Energy Density Science. Presently, the project is installing production hardware to complete the project in 2009 with the goal to begin ignition experiments in 2010. An integrated plan has been developed including the NIF operations, user equipment such as diagnostics and cryogenic target capability, and experiments and calculations to meet this goal. This talk will provide NIF status, the plan to complete NIF, and the path to ignition. (authors)

[en] Generation of mono-energetic, high brightness gamma-rays requires state of the art lasers to both produce a low emittance electron beam in the linac and high intensity, narrow linewidth laser photons for scattering with the relativistic electrons. Here, we overview the laser systems for the 3rd generation Monoenergetic Gamma-ray Source (MEGa-ray) currently under construction at Lawrence Livermore National Lab (LLNL). We also describe a method for increasing the efficiency of laser Compton scattering through laser pulse recirculation. The fiber-based photoinjector laser will produce 50 (micro)J temporally and spatially shaped UV pulses at 120 Hz to generate a low emittance electron beam in the X-band RF photoinjector. The interaction laser generates high intensity photons that focus into the interaction region and scatter off the accelerated electrons. This system utilizes chirped pulse amplification and commercial diode pumped solid state Nd:YAG amplifiers to produce 0.5 J, 10 ps, 120 Hz pulses at 1064 nm and up to 0.2 J after frequency doubling. A single passively mode-locked Ytterbium fiber oscillator seeds both laser systems and provides a timing synch with the linac.

[en] Time resolved hard x-ray images (hv>9 keV) and time integrated hard x-ray spectra (hv=18-150 keV) from vacuum hohlraums irradiated with four 351 nm wavelength National Ignition Facility [J. A. Paisner, E. M. Campbell, and W. J. Hogan, Fusion Technol. 26, 755 (1994)] laser beams are presented as a function of hohlraum size, laser power, and duration. The hard x-ray images and spectra provide insight into the time evolution of the hohlraum plasma filling and the production of hot electrons. The fraction of laser energy detected as hot electrons (F_hot) shows a correlation with laser intensity and with an empirical hohlraum plasma filling model. In addition, the significance of Au K-alpha emission and Au K-shell reabsorption observed in some of the bremsstrahlung dominated spectra is discussed

[en] Time resolved hard X-ray images (hν > 9 keV) and time integrated hard X-ray spectra (hν = 18-150 keV) from vacuum hohlraums irradiated with four 351 nm wavelength NIF laser beams are presented as a function of hohlraum size and laser power and duration. The hard X-ray images and spectra provide insight into the time evolution of the hohlraum plasma filling and the production of hot electrons. The fraction of laser energy detected as hot electrons (f(hot)) shows correlation with both laser intensity and with an analytic plasma filling model. The results show increased filling for smaller hohlraums and/or longer pulses and increased f(hot) for higher intensities and more filling

[en] The rf photoinjector and linear accelerator in the Mono-Energetic Gamma-ray (MEGa-ray) facility at LLNL is presented. This machine uses 11.4 GHz rf technology to accelerate a high-brightness electron beam up to 250 MeV to produce MeV γ-rays through Compton scattering with a Joule-class laser pulse. Compton scattering-based generation of high flux, narrow bandwidth γ-rays places stringent requirements on the performance of the accelerator. The component parts of the accelerator are presented and their requirements described. Simulations of expected electron beam parameters and the resulting light source properties are presented.