RFQ-cooler for low-energy radioactive ions at ISOLDE

A radio frequency ion cooler and buncher project at the CERN-ISOLDE facility is presented. Monte Carlo simulations, based on the ion mobility concept will be discussed. Future options for the facility are outlined

Molecular tendrils feeding star formation in the Eye of the Medusa - The Medusa merger in high resolution 12CO 2-1 maps

Studying molecular gas properties in merging galaxies gives us important clues to the onset and evolution of interaction-triggered starbursts. NGC4194 is particularly interesting to study since its FIR-to-CO luminosity ratio rivals that of ULIRGs,despite its lower luminosity compared to ULIRGs, which indicates a high star formation efficiency that is relative to even most spirals and ULIRGs.We study the molecular medium at an angular resolution of 0.65"x .52" through our observations of CO2-1 emission using the SMA. We compare our CO2-1 maps with optical HST and high angular resolution radio continuum images to study the relationship between molecular gas and other components of the starburst region. The molecular gas is tracing the complicated dust lane structure of NGC4194 with the brightest emission being located in an off-nuclear ring-like structure with ~320pc radius, the Eye of the Medusa. The bulk CO emission of the ring is found south of the kinematical center of NGC4194. The northern tip of the ring is associated with the galaxy nucleus, where the radio continuum has its peak. A prominent, secondary emission maximum in the radio continuum is located inside the molecular ring. This suggests that the morphology of the ring is partially influenced by massive supernova explosions. From the combined evidence, we propose that the Eye of the Medusa contains a shell of swept up material where we identify a number of giant molecular associations. We propose that the Eye may be the site of an efficient starburst of 5-7M_sun/yr, but it would still constitute only a fraction of the 30-50M_sun/yr SFR of NGC4194. Furthermore, we find that ~50% of the molecular mass of NGC4194 is found in extended filamentary-like structures tracing the minor and major axis dust lanes. We suggest that molecular gas is transported along these lanes providing the central starburst region with fuel.Comment: accepted for publication in A&A, 12 pages, 9 figure

Optimization of Neutrino Rates from the EURISOL Beta-Beam Accelerator Complex

The beta beam concept for the production of intense (anti-)neutrino beams is now well established. A baseline design has recently been published for a beta-beam facility at CERN. It has the virtue of respecting the known limitations of the CERN PS and SPS synchrotrons, but falls short of delivering the requested annual rate of neutrinos. We report on a first analysis to increase the rate using the baseline ions of 6He and 18 Ne. A powerful method to understand the functional dependence of the many parameters that influence the figure of merit for a given facility is available with modern analytical calculation software. The method requires that a symbolic analytical description is produced of the full accelerator chain. Such a description has been made using Mathematica for the proposed beta beam facility at CERN. The direct access from Mathematica to an ORACLE database for reading basic design parameters and re-injecting derived parameters for completion of the parameter list is both convenient and efficient

θ13\theta_{13}, δ\delta and the neutrino mass hierarchy at a γ=350\gamma=350 double baseline Li/B β\beta-Beam

We consider a $\beta$-Beam facility where $^8$Li and $^8$B ions are accelerated at $\gamma = 350$, accumulated in a 10 Km storage ring and let decay, so as to produce intense $\bar \nu_e$ and $\nu_e$ beams. These beams illuminate two iron detectors located at $L \simeq 2000$ Km and $L \simeq 7000$ Km, respectively. The physics potential of this setup is analysed in full detail as a function of the flux. We find that, for the highest flux ($10 \times 10^{18}$ ion decays per year per baseline), the sensitivity to $\theta_{13}$ reaches $\sin^2 2 \theta_{13} \geq 2 \times10^{-4}$; the sign of the atmospheric mass difference can be identified, regardless of the true hierarchy, for $\sin^2 2 \theta_{13} \geq 4\times10^{-4}$; and, CP-violation can be discovered in 70% of the $\delta$-parameter space for $\sin^2 2 \theta_{13} \geq 10^{-3}$, having some sensitivity to CP-violation down to $\sin^2 2 \theta_{13} \geq 10^{-4}$ for $|\delta| \sim 90^\circ$.Comment: 35 pages, 20 figures. Minor changes, matches the published versio

The High Resolution Spectrometer at ISOLDE

ISOLDE's HRS (High Resolution isotope Separator) was recommissioned in mid 2000, after a period out of service. Since then, the separator has routinely run with a mass resolution of 3000-4500 and during 2001 it delivered 72% of ISOLDE's radioactive output. A concerted effort has been made to understand the ion optics and optimise performance. In this paper we present an overview of the HRS and investigate the factors which limit the attainable mass resolution: ion-source emittance; optical aberrations; beam instrumentation and magnet stability

Towards a first-principles theory of surface thermodynamics and kinetics

Understanding of the complex behavior of particles at surfaces requires detailed knowledge of both macroscopic and microscopic processes that take place; also certain processes depend critically on temperature and gas pressure. To link these processes we combine state-of-the-art microscopic, and macroscopic phenomenological, theories. We apply our theory to the O/Ru(0001) system and calculate thermal desorption spectra, heat of adsorption, and the surface phase diagram. The agreement with experiment provides validity for our approach which thus identifies the way for a predictive simulation of surface thermodynamics and kinetics.Comment: 4 pages including 3 figures. Related publications can be found at http://www.fhi-berlin.mpg.de/th/paper.htm

Energetic and spatial bonding properties from angular distributions of ultraviolet photoelectrons: application to the GaAs(110) surface

Angle-resolved ultraviolet photoemission spectra are interpreted by combining the energetics and spatial properties of the contributing states. One-step calculations are in excellent agreement with new azimuthal experimental data for GaAs(110). Strong variations caused by the dispersion of the surface bands permit an accurate mapping of the electronic structure. The delocalization of the valence states is discussed analogous to photoelectron diffraction. The spatial origin of the electrons is determined, and found to be strongly energy dependent, with uv excitation probing the bonding region.Comment: 5 pages, 3 figures, submitted for publicatio

Optimal β\beta-beam at the CERN-SPS

A $\beta$-beam with maximum $\gamma=150$ (for \helio ions) or $\gamma=250$ (for \neon) could be achieved at the CERN-SPS. We study the sensitivity to $\theta_{13}$ and $\delta$ of such a beam as function of $\gamma$, optimizing with the baseline constrained to CERN-Frejus (130 km), and also with simultaneous variation of the baseline. These results are compared to the {\it standard} scenario previously considered, with lower $\gamma=60/100$, and also with a higher $\gamma\sim 350$ option that requires a more powerful accelerator. Although higher $\gamma$ is better, loss of sensitivity to $\theta _{13}$ and $\delta$ is most pronounced for $\gamma$ below 100.Comment: 22 page

Nickel: A very fast diffuser in silicon

Nickel is increasingly used in both IC and photovoltaic device fabrication, yet it has the potential to create highly recombination-active precipitates in silicon. For nearly three decades, the accepted nickel diffusivity in silicon has been DNi(T)=2.3×10exp−3 exp(−0.47 eV/kBT) cm2/s, a surprisingly low value given reports of rapid nickel diffusion in industrial applications. In this paper, we employ modern experimental methods to measure the higher nickel diffusivity DNi(T)=(1.69±0.74)×10exp−4 exp(−0.15±0.04 eV/kBT)  cm2/s. The measured activation energy is close to that predicted by first-principles theory using the nudged-elastic-band method. Our measured diffusivity of nickel is higher than previously published values at temperatures below 1150 °C, and orders of magnitude higher when extrapolated to room temperature.Peer reviewe