Pion-Nucleus Scattering at Medium Energies with Densities from Chiral Effective Field Theories

Recently developed chiral effective field theory models provide excellent descriptions of the bulk characteristics of finite nuclei, but have not been tested with other observables. In this work, densities from both relativistic point-coupling models and mean-field meson models are used in the analysis of meson-nucleus scattering at medium energies. Elastic scattering observables for 790 MeV/$c$ $\pi^{\pm}$ on $^{208}$Pb are calculated in a relativistic impulse approximation, using the Kemmer-Duffin-Petiau formalism to calculate the $\pi^{\pm}$ nucleus optical potential.Comment: 9 page

Spoke cavity power coupler conceptual design work for the HEL-JTO beam exp.

The objective of this report was to create a low-cost, modest-power RF coupler for a SRF spoke cavity beam test of electrons test to be done at LANL. Developing the design for this magnetically-coupled SRF spoke cavity testing coupler was basically straightforward since the cavity coupling port needed to be one of the 1.22-inch ID ports, and the power level was limited by the available RF to less than 400 W TW power. In addition, the coupler would be immersed in bath cryostat filled with liquid helium, and ultimately used in a pulsed mode to accelerate beam, thereby significantly relaxing the thermal loads on the coupler. Combining the above considerations with the level of resources available for this task, emphasis was placed on rapidly developing a robust, reliable design that would use commercially-available components as available to save design, engineering, and fabrication costs. Analysis was also kept to a minimum. As such, the design incorporates the following features: (1) Use of a commercially-available Type-N ceramic feedthrough. For the power and frequency range of the test, with the feedthrough immersed in LHe, it was felt the Type-N feedthrough would provide a robust, low-cost vacuum window solution. (2) The coupler outer conductors would be solid OFE copper that is brazed into two 2.75-inch CFF, with the cavity-sde flange being rotatable to allow minor Qx adjustments by rotating the coupler. The braze joint shown has the copper brazed into a groove in the SST to ensure maximum strength for successive thermal cyclings. The outer wall of the copper between the two flanges serves as the heat sink for depositing coupler heat to the liquid helium. (3) The inner conductor would be solid OFE copper brazed to the outer conductor at the top to ensure maximum thermal conductivity from the outer thermal sink area to the base of the feedthrough. A mass-reducing hole is placed down the center of the inner conductor to decrease thermal mass and weight. (4) This assembly would be mated to the Type-N feedthrough by pushing the pin from the feedthrough into a spring-loaded connector on the base of the inner conductor, then bolting the flanges together. (5) If the coupling needs to be greatly reduced, an additional 1/2-inch CFF can be inserted between the coupler and cavity flanges. Increasing the coupling can be done with a 3 stub tuner

High-Energy Neutron Imaging Development at LLNL

We are proceeding with the development of a high-energy (10 MeV) neutron imaging system for use as an inspection tool in nuclear stockpile stewardship applications. Our goal is to develop and deploy an imaging system capable of detecting cubic-mm-scale voids, cracks or other significant structural defects in heavily-shielded low-Z materials within nuclear device components. The final production-line system will be relatively compact (suitable for use in existing or proposed facilities within the DOE complex) and capable of acquiring both radiographic and tomographic (CT) images. In this report, we will review our programmatic accomplishments to date, highlighting recent (FY06) progress on engineering and technology development issues related to the proposed imaging system. We will also discuss our preliminary project plan for FY07, including engineering initiatives, proposed radiation damage experiments (neutrons and x rays) and potential options for conducting classified neutron imaging experiments at LLNL

Building Atomic Nuclei with the Dirac Equation

The relevance of the Dirac equation for computations of nuclear structure is motivated and discussed. Quantitatively successful results for medium- and heavy-mass nuclei are described, and modern ideas of effective field theory and density functional theory are used to justify them.Comment: 9 pages, REVTeX 4.0 with 12pt.rtx, aps.rtx, amssymb.tex, bm.sty, ntgdefs.tex. Contribution to the Dirac Centennial Symposium (FSU, 12/6-7/02

Design and Simulation of a Rotating Aperture & Vacuum System for Neutron Imaging

The development of a high-energy (10Mev) neutron imaging system at Lawrence Livermore National Laboratory (LLNL) depends on a precision engineered rotating aperture and vacuum system for generating neutrons that are used for imaging dense objects. This subsystem is part of a larger system which includes a linear accelerator that creates a deuteron beam, a scintillator detector, imaging optics and a high resolution CCD camera. The rotating aperture vacuum system has been successfully simulated and tested. Results show the feasibility of the design and point toward ways to improve the design by minimizing the rotating aperture gap

Application of ILC super conducting cavities for acceleration of protons

Beam acceleration in the International Linear Collider (ILC) will be provided by 9-cell 1300 MHz superconducting (SC) cavities. The cavities are designed for effective acceleration of charged particles moving with the speed of light and are operated on {pi}-mode to provide maximum accelerating gradient. Significant R&D effort has been devoted to develop ILC SC technology and its RF system which resulted excellent performance of ILC cavities. Therefore, the proposed 8-GeV proton driver in Fermilab is based on ILC cavities above {approx}1.2 GeV. The efficiency of proton beam acceleration by ILC cavities drops fast for lower velocities and it was proposed to develop squeezed ILC-type (S-ILC) cavities operating at 1300 MHz and designed for {beta}{sub G} = 0.81, geometrical beta, to accelerate protons or H{sup -} from {approx}420 MeV to 1.2 GeV. This paper discusses the possibility of avoiding the development of new {beta}{sub G} = 0.81 cavities by operating ILC cavities on 8/9{pi}-mode of standing wave oscillations

Designing double-gap linear accelerators for a wide mass range

For applications like ion implantation, rf linacs using double-gap structures with external resonators can be used because they are practical at low frequencies. However, since the two gaps associated with a given resonator cannot be individually phased, it is not obvious how to build a linac that can efficiently accelerate particles having different mass/charge ratios. This paper describes the beam dynamics of double-gap rf linacs and shows how to maximize the range of mass/charge ratios. The theory also tells one how to rescale a linac tune (i.e., reset the voltages and phases) so that a new particle, having a different mass or charge, will behave similarly to the original particle

Effective Field Theory for Bulk Properties of Nuclei

Recent progress in Lorentz-covariant quantum field theories of the nuclear many-body problem ({\em quantum hadrodynamics}, or QHD) is discussed. The importance of modern perspectives in effective field theory and density functional theory for understanding the successes of QHD is emphasized. The inclusion of hadronic electromagnetic structure and of nonanalytic terms in the energy functional is also considered.Comment: 11 pages, 0 figures, REVTeX 3.0; Invited talk at the 11th Conference on Recent Progress in Many-Body Theories (MB 11), Manchester, UK, July 9--13, 200