7.6 3 10 6 x-ray photons per 3.5 ps pulse are detected within a 1.8-2.3 Å spectral window during a proof-of-principle laser synchrotron source experiment. A 600 MW CO 2 laser interacted in a head-on collision with a 60 MeV, 140 A, 3.5 ps electron beam. Both beams were focused to a s 32 mm spot. Our next plan is to demonstrate 10 10 x-ray photons per pulse using a CO 2 laser of ϳ1 TW peak power.

In order to learn about in situ structural changes in materials at subseconds time scale, we have further refined the techniques of quick extended x-ray absorption fine structure (QEXAFS) and quick x-ray absorption near edge structure (XANES) spectroscopies at beamline X18B at the National Synchrotron Light Source. The channel cut Si (111) monochromator oscillation is driven through a tangential arm at 5 Hz, using a cam, dc motor, pulley, and belt system. The rubber belt between the motor and the cam damps the mechanical noise. EXAFS scan taken in 100 ms is comparable to standard data. The angle and the angular range of the monochromator can be changed to collect a full EXAFS or XANES spectrum in the energy range 4.7-40.0 KeV. The data are recorded in ascending and descending order of energy, on the fly, without any loss of beam time. The QEXAFS mechanical system is outside the vacuum system, and therefore changing the mode of operation from conventional to QEXAFS takes only a few minutes. This instrument allows the acquisition of time resolved data in a variety of systems relevant to electrochemical, photochemical, catalytic, materials, and environmental sciences.

M.E. Coles, SPE, R.D. Hazlett, and E.L. Muegge, Mobil E& P Technical Center, K.W. Jones, B. Andrews, B. Dowd, P. Siddons, and A. Peskin, Brookhaven National Laboratory, P. Spanne, European Synchrotron Facility, W.E. Soll, Los Alamos National Laboratory Abstract High resolution computed microtomography (CMT) using synchrotron X-ray sources provides the ability to obtain three-dimensional images of specimens with a spatial resolution on the order of micrometers. Microimaging capabilities at Brookhaven National Laboratory's National Synchrotron Light Source have been enhanced to provide larger and higher resolution 3-D renderings of pore networks in reservoir rocks at a fraction of the time required in previous first generation scanning methods. Such data are used to model single and multiphase flow properties in digital images of real porous media. Pore networks are analyzed for tortuosity and connectivity measures, which have been elusive parameters in transport property models. We present examples of porosimetry simulation via network modeling to produce initial water saturation and residual oil distributions in a water-wet pore system. Furthermore, pore networks can provide the boundary condition framework for more rigorous simulations of displacement, such as in the lattice Boltzmann simulated waterflood example provided. Direct comparison between simulation and experiment is also possible. CMT images of a 6 mm subsection of a one inch diameter reservoir core sample were obtained prior and subsequent to flooding to residual oil. The fluid distributions from CMT, lattice Boltzmann waterflood simulation, and percolation-based network modeling were found to be highly correlated. Advances in 3-D visualization, implemented in Brookhaven National Laboratory's 3-D theater, will allow even greater digestion and interpretation of phenomena dependent upon pore interconnectivity and multipore interactions. Introduction Computed Microtomography (CMT) has been available at the National Synchrotron Light Source (NSLS) at Brookhaven National Laboratory for many years. First generation scanning methods gave high resolution images of geological and biological samples approaching 1 m resolution. First generation scanning provided necessary detail in moderate to high permeability porous media samples for transport property modeling with computational fluid dynamics methods. The time requirements of first generation methods limited the number of samples which could be investigated and restricted the potential of in-situ experimental monitoring. Implementation of array detection technology enables acquisition of larger 3-D volumes at a fraction of the time required in first generation scanning. Initial implementation, however, was limited by the resolution of fluorescing elements of the detector material, on the order of 10 m rather than 1 m. With the introduction of expansion optics, images of 2.7 m resolution have been obtained containing in the neighborhood of 3x 107 voxels. Improvements in data acquisition, transmission, and reconstruction have reduced the time requirements to produce such a volume to a few hours. Herein we document the status of CMT at the NSLS and display a variety of applications using both first generation and state-of-the-art image data on reservoir rock samples. Advances in Imaging A schematic of the CMT apparatus is provided as Figure 1, X-ray CMT produces a cross-sectional map, or slice, of linear x-ray attenuation coefficients inside a small sample. To obtain the data for a reconstructed slice, the x-rays transmitted through a single slice of the sample are recorded on a linear array of detectors. The sample is rotated, with the axis of rotation perpendicular to the plane of the incident beam, by a discrete angular interval determined by the linear resolution desired. The transmission of each ray through the sample, along a line from the source to the detector is recorded; this represents a line integral of the attenuation coefficients along this ray. The procedure is repeated for each angular view until the sample has been rotated by 180 in the x-ray beam. P. 413

Abstract-Existence of the natural diffusive spread of charge carriers on the course of their drift towards collecting electrodes in planar, segmented detectors results in a division of the original cloud of carriers between neighboring channels. This paper presents the analysis of algorithms, implementable with reasonable circuit resources, whose task is to prevent degradation of the detective quantum efficiency in highly granular, digital pixel detectors. The immediate motivation of the work is a photon science application requesting simultaneous timing spectroscopy and 2D position sensitivity. Leading edge discrimination, provided it can be freed from uncertainties associated with the charge sharing, is used for timing the events. Analyzed solutions can naturally be extended to the amplitude spectroscopy with pixel detectors.

High resolution computed microtomography (CMT) with synchrotron X-ray sources provides the ability to obtain three-dimensional (3D) images of specimens with a spatial resolution on the order of micrometers. Microimaging capabilities at Brookhaven Natl. Laboratory's Natl. Synchrotron Light Source have been enhanced to provide larger and higher resolution 3D renderings of pore networks in reservoir rocks at a fraction of the time required in previous first generation scanning methods. Such data are used to model single and multiphase flow properties in digital images of real porous media. Pore networks are analyzed for tortuosity and connectivity measures, which have been elusive parameters in transport property models. We present examples of porosimetry simulation through network modeling to produce initial water saturation and residual oil distributions in a water-wet pore system. Furthermore, pore networks can provide the boundary condition framework for more rigorous simulations of displacement, such as in the lattice Boltzmann simulated waterflood example provided. Direct comparison between simulation and experiment is also possible. CMT images of a 6-mm subsection of a 1-in. diameter reservoir core sample were obtained before and after flooding to residual oil. The fluid distributions from CMT, lattice Boltzmann waterflood simulation, and percolation-based network modeling were found to be highly correlated. Advances in 3D visualization will allow even greater digestion and interpretation of phenomena dependent upon pore interconnectivity and multipore interactions.