Apparatus for the investigation of instabilities in gas cooled heat exchanger tubes

Apparatus to investigate laminar instability in gas cooled heat exchanger tube

The role of ν\nu-induced reactions on lead and iron in neutrino detectors

We have calculated cross sections and branching ratios for neutrino induced reactions on ^{208}Pb and ^{56}Fe for various supernova and accelerator-relevant neutrino spectra. This was motivated by the facts that lead and iron will be used on one hand as target materials in future neutrino detectors, on the other hand have been and are still used as shielding materials in accelerator-based experiments. In particular we study the inclusive ^{56}$Fe(\nu_e,e^-)$^{56}Co and ^{208}$Pb(\nu_e,e^-)$^{208}Bi cross sections and calculate the neutron energy spectra following the decay of the daughter nuclei. These reactions give a potential background signal in the KARMEN and LSND experiment and are discussed as a detection scheme for supernova neutrinos in the proposed OMNIS and LAND detectors. We also study the neutron-emission following the neutrino-induced neutral-current excitation of ^{56}Fe and ^{208}Pb.Comment: 23 pages (including 7 figures

Neutrino and antineutrino cross sections in 12^{12}C

We extend the formalism of weak interaction processes, obtaining new expressions for the transition rates, which greatly facilitate numerical calculations, both for neutrino-nucleus reactions and muon capture. We have done a thorough study of exclusive (ground state) properties of $^{12}$B and $^{12}$N within the projected quasiparticle random phase approximation (PQRPA). Good agreement with experimental data is achieved in this way. The inclusive neutrino/antineutrino ($\nu/\tilde{\nu}$) reactions $^{12}$C($\nu,e^-)^{12}$N and $^{12}$C($\tilde{\nu},e^+)^{12}$B are calculated within both the PQRPA, and the relativistic QRPA (RQRPA). It is found that the magnitudes of the resulting cross-sections: i) are close to the sum-rule limit at low energy, but significantly smaller than this limit at high energies both for $\nu$ and $\tilde{\nu}$, ii) they steadily increase when the size of the configuration space is augmented, and particulary for $\nu/\tilde{\nu}$ energies $> 200$ MeV, and iii) converge for sufficiently large configuration space and final state spin.Comment: Proceedings of the International Nuclear Physics Conference 2010, Vancouver, BC - Canada 4-9 Jul 201

Rydberg excitation of a single trapped ion

We demonstrate excitation of a single trapped cold $^{40}$Ca$^+$ ion to Rydberg levels by laser radiation in the vacuum-ultraviolet at 122 nm wavelength. Observed resonances are identified as 3d$^2$D$_{3/2}$ to 51 F, 52 F and 3d$^2$D$_{5/2}$ to 64F. We model the lineshape and our results imply a large state-dependent coupling to the trapping potential. Rydberg ions are of great interest for future applications in quantum computing and simulation, in which large dipolar interactions are combined with the superb experimental control offered by Paul traps.Comment: 4 pages, 3 figure

Neutrino-Nucleus Cross Section Measurements using Stopped Pions and Low Energy Beta Beams

Two new facilities have recently been proposed to measure low energy neutrino-nucleus cross sections, the nu-SNS (Spallation Neutron Source) and low energy beta beams. The former produces neutrinos by pion decay at rest, while the latter produces neutrinos from the beta decays of accelerated ions. One of the uses of neutrino-nucleus cross section measurements is for supernova studies, where typical neutrino energies are 10s of MeV. In this energy range there are many different components to the nuclear response and this makes the theoretical interpretation of the results of such an experiment complex. Although even one measurement on a heavy nucleus such as lead is much anticipated, more than one data set would be still better. We suggest that this can be done by breaking the electron spectrum down into the parts produced in coincidence with one or two neutrons, running a beta beam at more than one energy, comparing the spectra produced with pions and a beta beam or any combination of these.Comment: 6 pages, 6 figure

Muon capture on nuclei with N > Z, random phase approximation, and in-medium renormalization of the axial-vector coupling constant

We use the random phase approximation to describe the muon capture rate on ${}^{44}$Ca,${}^{48}$Ca, ${}^{56}$Fe, ${}^{90}$Zr, and ${}^{208}$Pb. With ${}^{40}$Ca as a test case, we show that the Continuum Random Phase Approximation (CRPA) and the standard RPA give essentially equivalent descriptions of the muon capture process. Using the standard RPA with the free nucleon weak form factors we reproduce the experimental total capture rates on these nuclei quite well. Confirming our previous CRPA result for the $N = Z$ nuclei, we find that the calculated rates would be significantly lower than the data if the in-medium quenching of the axial-vector coupling constant were employed.Comment: submitted to Phys. Rev.

Neutrino induced transitions between the ground states of the A=12 triad

Neutrino induced reactions on $^{12}$C, an ingredient of liquid scintillators, have been studied in several experiments. We show that for currently available neutrino energies, $E_{\nu} \le$ 300 MeV, calculated exclusive cross sections $^{12}$C$_{gs}(\nu,l)$$^{12}$N$_{gs}$ for both muon and electron neutrinos are essentially model independent, provided the calculations simultaneously describe the rates of several other reactions involving the same states or their isobar analogs. The calculations agree well with the measured cross sections, which can be therefore used to check the normalization of the incident neutrino spectrum and the efficiency of the detector.Comment: 9 pages REVTEX, 2 postscript figures, text and figures available at http://www.krl.caltech.edu/preprints/MAP.htm

Signal for supernova νμ\nu_\mu and ντ\nu_\tau neutrinos in water \v{C}erenkov detectors

We suggest that photons with energies between 5 and 10 MeV, generated by the ($\nu,\nu'p\gamma$) and ($\nu,\nu'n\gamma$) reactions on $^{16}$O, constitute a signal which allows a unique identification of supernova $\nu_\mu$ and $\nu_\tau$ neutrinos in water \v{C}erenkov detectors. We calculate the yield of such $\gamma$ events and estimate that a few hundred of them would be detected in Superkamiokande for a supernova at 10 kpc distance.Comment: 8 pages, RevTex 3.0, figures and text available at http://www.krl.caltech.edu/preprints/MAP.htm

Continuous Lyman-alpha generation by four-wave mixing in mercury for laser-cooling of antihydrogen

Cooling antihydrogen atoms is important for future experiments both to test the fundamental CPT symmetry by high-resolution laser spectroscopy and also to measure the gravitational acceleration of antimatter. Laser-cooling of antihydrogen can be done on the strong 1S-2P transition at the wavelength of Lyman-alpha (121.6nm). A continuous-wave laser at the Lyman-alpha wavelength based on solid-state fundamental lasers is described. By using a two-photon and a near one photon resonance a scan across the whole phasematching curve of the four-wave mixing process is possible. Furthermore the influence of the beam profile of one fundamental beam on the four-wave mixing process is studied.Comment: 4 pages, 4 figure

Foundation Grouting for the Forks of Butte Powerhouse

Construction of a powerhouse on unconsolidated landslide debris materials at the edge of a stream channel in a narrow, steep-sided canyon in northern California entailed application of an unusual combination of grouting techniques to protect the foundation during peak flows. These techniques included permeation grouting, displacement grouting, compaction grouting, and controlled hydrofracture grouting