Experimental Methods in The Physical Sciences 

About: Experimental Methods in The Physical Sciences is an academic journal. The journal publishes majorly in the area(s): Neutron scattering & Laser. It has an ISSN identifier of 1079-4042. Over the lifetime, 206 publications have been published receiving 1900 citations.

Neutron Scattering Lengths and Cross Sections

Abstract: In this appendix, we present an updated table of neutron scattering lengths and cross sections for most of the known nuclides, based on preexisting works. We include the coherent and incoherent scattering lengths, as well as the spin-dependent scattering lengths b + and b − , in cases where this information is available. Also presented are the scattering coherent, incoherent, total, and absorption cross sections. We present an overview of the fundamental theory of the magnitudes to which the table is referred, and also a summary of the main experimental techniques used in determining these magnitudes.

1. Stabilizing diode lasers to high-finesse cavities

Abstract: Publisher Summary This chapter discusses the issues involved in diode laser locking. The chapter describes in detail the various steps needed to lock the laser to a cavity resonance: (1) Derivetion of the error (locking) signal, (2) design of the electronic feedback circuitry, (3) initial locking of the laser, (4) adjustment of the feedback design, and (5) evaluation of the lock performance. The chapter illustrates this discussion by frequency locking an extended-cavity diode laser, reducing the linewidth to a few hertz relative to the cavity. The chapter concludes with an example in which the locking apparatus is modified for a cavity ring-down demonstration. Included are results showing the laser repetitively locking and unlocking to the cavity.

9. Nuclear Magnetic Resonance

Abstract: Publisher Summary The chapter presents a review on the methods and applications of nuclear magnetic resonance (NMR) measurements of porous media. It focuses on amplitude and relaxation techniques developed specifically for porous media. Other reviews cover magnetic resonance imaging, pulsed field-gradient techniques, and characterization of fluid flows by NMR. Special attention is paid to sedimentary rocks, which present a broad range of difficulties to the experimentalist and are in many respects “worst-case” porous media. Measurements have been made in the laboratory and, in some cases, by “inside-out’’ NMR equipment operating as much as 10 km underground for the purpose of measuring properties of subsurface geological formations in situ . Where the pore openings are on a molecular scale, such as in intercalation compounds and zeolites, the guest phases behave as individual molecules not as continuous fluids. Methods that are useful for characterizing these materials are in some respects distinct from those presented in the chapter. The use of NMR to investigate porous media has primarily focused on measurements of the fluids in the pore space. Because the common pore fluids are rich in hydrogen, most applications are based on proton NMR measurements. An NMR relaxation time measurement can be used to determine a volumetrically weighted distribution of pore sizes spanning several orders of magnitude. Properties that have been derived from the NMR-determined pore size distribution include hydraulic permeability and the capillary pressure curve. Calibrated proton spin density measurements can be the simplest and most accurate way to measure the volume fraction of pore space (porosity).

2 - Supersonic Beam Sources

Abstract: The supersonic expansions provide a means of preparing a molecular beam with a well-defined kinetic energy, which is particularly useful for crossed-beam and beam-surface scattering experiments This chapter discusses the supersonic expansions from circular nozzles The idealized continuum model assumes that collisions occur with sufficient frequency for equilibrium to be maintained throughout the expansion process This chapter also describes the interaction with background gases In any real apparatus, the idealized continuum model will also break down when the expanding gas becomes sufficiently rarefied that its density approaches that of the background gases This chapter also focuses on the supersonic expansions from slit nozzles (plane jets) In an idealized continuum slit supersonic expansion, it is still assumed that the gas flows without heat transfer to the walls and without viscosity, and an adiabatic, isentropic expansion is obtained

1. Digital Images and Computer Modeling

Abstract: This chapter describes how digital images of porous materials can be analyzed to give information about the structure and properties of the material and the various ways 3-D digital-image-based models can be generated to help understand real porous materials.