Fan Array Research Articles

Design of radial neutron spectrometer array for the International Thermonuclear Experimental Reactor

We designed the radial neutron spectrometer using a new type DT neutron spectrometer base on a recoil proton counter-telescope technique aiming ion temperature measurement for the International Thermonuclear Experimental Reactor (ITER). The neutron spectrometer will be installed on the well collimated neutron beam line. A large area recoil proton emitter is placed parallel to the incident neutron beam and microchannel collimating plates are inserted between the radiator and the recoil proton detectors away from the neutron beam in order to limit the scattering angle of protons to the proton detectors. Here a very thin polyethylene film and a silicon surface barrier detector are employed as the radiator and proton detector, respectively. The energy resolution and detection efficiency are estimated to be 2.5% and 1×10−5 counts neutron−1 m2, respectively, for the DT neutron through Monte Carlo calculations. Five units of the spectrometers will be installed just outside the biological shield, will include a fan array using penetrations inside the bioshield and a precollimator in the horizontal port. The lifetime of the proton detectors is estimated to be about one year in the basic performance phase of ITER by neutron transport calculations using the Monte Carlo neutron and photon transport code (MCNP).

Optical characteristics of beam steerable semiconductorfan laser array

A detailed characterisation of beam steerable fan laser arrays is presented. The near field of the fan arrays is imaged to show that the device has a single common effective aperture. The threshold statistics indicate that facet reflectivity is independent of crystal orientation. Further, the output angle is pump current independent.

Velocity structure of the Long Valley Caldera from the inversion of local earthquake P and S travel times

A high‐resolution tomographic study of the Long Valley region began in 1989 with the installation of a special fan array of eight three‐component borehole (80–160 m depths) receivers on the northwestern rim of the caldera to provide the data necessary for a joint inversion for hypocenters and the three‐dimensional P and S wave velocity structure in and below the caldera. The experiment specifically targeted the subsurface location of the previously inferred magma chamber beneath the Resurgent Dome. Additional coverage was provided by existing U.S. Geological Survey and University of Nevada, Reno seismographic networks. We employed the progressive inversion scheme of Thurber (1983), with cubic spline interpolation after Michelini and McEvilly (1991). The final model is based on data from 280 well‐distributed local earthquakes. Some 6900 arrival times were used, including about 700 S wave times from the three‐component stations. The resulting velocity structure reflects the known geology, defining the low‐velocity caldera fill to 2 km depth, contrasting markedly with the surrounding higher‐velocity Sierran block and highland terrane. No isolated distinct low‐velocity anomalies are revealed beneath the caldera floor, although a diffuse zone of reduced velocity persists to a depth of about 8 km. These lower velocities may be related to hydrothermal alteration and/or extensive fractures. The Vp/Vs structure contains significant lateral variation within and beneath the caldera to about 8 km depth, and these variations can be related to accepted models of the active geothermal system. The lack of a significant S wave velocity anomaly, along with the normal or low values of the Vp/Vs ratio, argues against the presence of a sizable and distinct magma body at shallow to midcrustal depth beneath Long Valley caldera, although a very low percentage of partial melt cannot be precluded.

Basement Tectonics of the Southem Termination of the Santander Massif, Eastern Cordillera, Colombian Andes

The Santander Massif is a broad, basement cored antiform which, where fully developed, is limited toward its eastern and western foreland basins by two oppositely dipping reverse faults, which involve minor thrusting within the foreland sediments. More internal faults, however, accommodated an east-west extension by limiting sedimentary wedges which have the structure of half-grabens. Both marginal and internal faults impart a near symmetrical fan structure to the massif. The alternating compressional and extensional deformation regimes are taken as evidence for a vertical flow model, in which laminar parts of the massif rose along slightly divergent movement paths, following the fan array of the faults, and triggered the extensional deformation at higher levels. Evidence for a steep attitude of the faults is provided by (1) normal faults which, when bordering secondary basement highs, become reverse faults of an opposed dip, and (2) by the Bucaramanga fault, which between the Santander Massif on its eastern side and the more southerly Mogotes-Arcabuco Massif on its western side inverts both dip and displacement. A further internal deformation, which controlled the massif's structural evolution, consists of a longitudinal stretch. This was mitigated within the basement itself by an internal arching, and, where transmitted to themore » foreland, was absorbed by minor transcurrent faults or by east-west trending normal faults, as is the case of the displaceD plateaus in the Bucaramanga area. Considering the deep-seated origin of the structures of the Santander Massif, it is suggested that the imbricate sheets of the Guaicaramo fold and thrust belt at the eastern foothills of the Cocuy Massif evolved out of steeply inclined synclines. Folding of these imbricate sheets reflects uplift of more foreland oriented basement blocks.« less

Multiorder rotating grating interferometer

A multichannel interferometer that uses a rotating grating to both disperse and Doppler shift an incident far-infrared laser beam is described. The laser beam is diffracted into a fan array of many (~ 10) beams that can be directed to probe the plasma along distinct chords. The phase-shift information is multiplexed in the frequency domain so that a single detector suffices to sense the recombined probing beams.

Novel scanning interferometer for two-dimensional plasma density measurements

A novel multichannel scanning interferometer designed for tomographically inferring contours of electron density in magnetically confined plasmas is described. The scanning element is a multisectored blazed rotating grating. The diffracted beam emerges at a different angle from each sector, giving rise to a fan array of discrete beams for each rotation of the grating. Signals from the probing chords are multiplexed in time enabling the use of a single detecting element for the extraction of many channels of line-integrated density information. An air-turbine-driven grating wheel assembly has been fabricated and initial tests performed. The proposed interferometer is to operate at 337 μm and will be installed on the H-1 helical axis stellarator currently under construction at the Australian National University.

X-ray tomography on plasmas with arbitrary cross sections and limited access

An x-ray imaging system is described for 2D reconstructions of plasmas with viewing access limitations. A relatively small number of 72 detectors distributed over six fan arrays first provides partial views of the toroidal plasma in a poloidal plane. Next, the line-integrated data is deconvoluted using a computerized tomographic approach based on linear algebra and a least-squares fit. The arrangement and the number of detectors have been optimized to the point where significant reconstruction improvements are limited by available viewing access rather than by the number of lines of sight.

Critical angles and grazing incidence: the breakdown of regular shock reflection in solids

The regular pattern for shock reflection in a nonlinear hyperelastic solid is a centered array of shocks and simple wave fans. As the angle of incidence approaches grazing incidence or a critical angle, the reflection pattern overtakes the incident wave until finally the regular pattern can no longer be sustained. By expanding the reflection solution in powers of amplitude about the linear reflection solution, it is possible to develop a procedure to solve the reflection problem for weak but finite shocks for any material symmetry. Explicit solutions can be exhibited for isotropic materials, including relationships between amplitude and limiting angle for various boundary conditions and incident waves. Some problems require consideration of a nonlinear boundary condition even in the first approximation. Typically, these cases lead to considerable amplification in the leading reflected wave.

Buffer properties of caved ore

Laboratory research and field observation of the buffer properties of caved rock made it possible to effect the following. 1. Obtain a qualitative relationship between the thickness of the buffer layer of ore and its degree of compaction for ore in the 0–2.5, 2.5–5.0, and 5.0–7.0 mm size ranges for parallel and fan hole arrangements. 2. Establish that compaction increases with the thickness of the buffer layer, regardless of the hole arrangement or the coarseness of the material. 3. Establish that in the case of the 0–2.5 mm fraction martite and hydrohematite-martite ores, the effect of the blast in parallel holes extends (for the investigated charge values at any rate) to a depth of 27 cm, while in the case of the 2.5–5.0 and 5.0–7.0 mm fractions, these values are 25 and 23 cm, respectively. 4. Where the holes are in a fan array in the center of the panel (block) the blasting effect extends to depths of 33.30 and 25.5 cm, respectively, for the 0–2.5, 2.5–5.0, and 5.0–7.0 mm fractions. 5. The qualitative laws thus obtained were confirmed in field observations carried out at the Gigant-Glubokaya mine. These laws have been recommended for determining the volume of compensation space available and the thickness of the buffer layer when working deposits in single-stage systems.