The excitation of coherent transients in Mossbauer spectra has been previously limited by the high powers required to modulate the nuclear phases. Reported here is an orders-of-magnitude increase in the efficiency through which such phenomena can be produced. Magnetic modulation of the quantum phases of 57 Fe nuclei in paramagnetic media has been produced by spin waves of large amplitude transported from ferromagnetic sources.

This paper discusses a new downhole logging instrument that measures three-phase flow in horizontal and highly deviated wells. The focus is on the instrument design features, and the measurement techniques that produce the three-phase holdup and velocity measurements. Signals from a two dimensional array of capacitive sensors are measured, and subsequent processing determines the volume fraction and velocity of each component of the borehole flow. The design incorporates an array of capacitive sensors that span the wellbore. Since two orthogonal electrical signals are used to excite local fluid elements, it is possible to determine the fluid capacitance or the volume fraction of conductive fluid in the vicinity of each sensor. Holdups are calculated from these sensor outputs. Velocities are calculated by correlating outputs from adjacent sensors. Measurement concepts and instrument characterization are demonstrated with flow loop data. [S0195-0738(00)00802-5]

A nuclear frequency-modulation spectrometer (NFMS) for high-resolution gamma-ray spectroscopy is described in this article. As the name implies, this device operates by modulating the cross section for gamma-ray absorption. The automation of this spectrometer required the development of an interface to an Apple computer which provides a real-time data display. This interface also enables the Apple computer to control up to two Mossbauer spectrometers at once, with a real-time data display for each. A nuclear frequency-modulation spectrometer makes it possible to observe directly the phenomenon known as Hrf sidebands" in M6ssbauer spectroscopy,without interference from the "parent transitions." The high resolution of NFMS makes it possible to examine the "rf sidebands" for any fine structure.

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