Paul Muzikar

Scaling factors for the rates of production of cosmogenic nuclides for geometric shielding and attenuation at depth on sloped surfaces

Abstract The decrease in rates of production of cosmogenic nuclides occurs because of shielding of cosmic rays by mountains, sloped surfaces, and local rock formations that block them. When a large part of the sky is blocked, this correction is large and requires detailed model calculations. This paper considers three geometries: a rectangular obstruction, a triangular obstruction, and a sloped surface. Other geometries can be considered as a combination of these. The results are presented in terms of formulas and graphs so that the reader can easily apply them to common field situations. Any use of cosmogenic nuclides in the study of geomorphic processes or forms must consider factors that introduce variations in the production of nuclides.

Dating sediment burial with in situ-produced cosmogenic nuclides: theory, techniques, and limitations

Abstract Dating sediment burial over million-year time scales is crucial in many areas of the Earth sciences and archeology, but is often difficult using traditional techniques. Sediment burial can be dated by the radioactive decay of cosmogenic nuclides, provided that the sediment was exposed to cosmic rays prior to burial. Dating calculations are straightforward if sediment is buried deeply and rapidly enough to prevent cosmogenic nuclide production after burial. However, the analysis can be complicated by postburial production if sediment is insufficiently shielded from secondary cosmic-ray nucleons and muons. This paper discusses how buried sediments can be dated over timescales up to 5 Myr using 26 Al and 10 Be in quartz.

Accelerator mass spectrometry in geologic research

The ability of accelerator mass spectrometry (AMS) to measure very small concentrations of the nuclides 10 Be, 14 C, 26 Al, 36 Cl, and 129 I has led to many innovative applications in geologic research. To take advantage of this opportunity in the geosciences, it is important to understand how AMS works, how these nuclides are produced, and how they can be applied to geologic problems. We first discuss the basics of AMS, explaining what gives the method its ability to count small numbers of these nuclides. We review how these nuclides are produced and transported in the atmosphere, hydrosphere, and lithosphere. We then explain the ways that AMS is being used to solve a wide range of problems in geologic research by discussing specific applications in areas such as geomorphology, tectonics, climatology, hydrology, and geochronology.

Correcting for Contamination in Ams 14c Dating

When using accelerator mass spectrometry (AMS) for radiocarbon dating, it is important to correct for carbon contamination that is added to the sample and the standard during chemical processing. We derive an equation for making this correction that generalizes previous work in several ways. We treat the case in which contaminating carbon is added during both the combustion step and graphitization step. Taking this two-stage contamination process into account is particularly important when only a fraction of the CO2 produced in the combustion is graphitized. We also allow for the fact that the 13C fractions of the sample, the standard, and the contaminants may be different.

Quantitative study of contamination effects in AMS 14C sample processing

Abstract When using AMS for radiocarbon work, it is important to characterize the contaminating carbon which is added to the sample during its preparation for the AMS measurement. This allows the effects of the contamination to be correctly subtracted out, and also helps to guide efforts to reduce the contamination. We performed a series of measurements on blanks and standards of varying sizes to quantify the contamination arising in the PRIME Lab’s radiocarbon sample processing laboratory. We present our results, along with a discussion of the analysis used to extract properties of the contaminants from the data. Our analysis allows for contamination added at two different stages in the sample preparation, and does not assume that the contaminants are modern.

Fermi-Liquid Theory of Non-S-Wave Superconductivity

These lectures present the Fermi-liquid theory of superconductivity, which is applicable to a broad range of systems that are candidates for non-s-wave pairing, e.g. the heavy fermions, organic metals and the CuO superconductors. Ginzburg-Landau (GL) theory provides an important link between experimental properties of non-s-wave superconductors and the more general Fermi-liquid theory. The multiple superconducting phases of UPt3 provide an ideal example of the role that is played by the GL theory for non-s-wave superconductors. The difference between non-swave superconductivity and conventional anisotropic superconductivity is illustrated here by the unique effects that impurities are predicted to have on the properties of non-s-wave superconductors.

Stability analysis of a low energy vortex configuration

AbstractRecent work using the London theory of anisotropic superconductivity has shown that, for small values ofB and large values of the anisotropy, a lattice of vortex lines parallel to

Vortex lines and field reversal in anisotropic superconductors

\vec B