RADAR TRANSPARENCIES OF MINE AND TUNNEL ROCKS

Geophysics ◽  
1975 ◽  
Vol 40 (5) ◽  
pp. 865-885 ◽  
Author(s):  
John C. Cook
Keyword(s):  
Moisture Content ◽  
Complex Permittivity ◽  
Parallel Plate ◽  
High Grade ◽  
Laboratory Measurements ◽  
Low Loss ◽  
Tar Sands ◽  
Fine Grained ◽  
Governing Factor ◽  
Oil Shales

Laboratory measurements of RF complex permittivity have been made on a variety of “rocks” encountered in mining, tunneling, and engineering works. An RF impedance bridge and a parallel‐plate capacitance test cell were employed at frequencies of 1, 5, 25, and 100 Mhz. The results predict that low‐loss propagation will be possible in certain granites, limestones, coals, and dry concretes. Existing VHF mining radar equipment should be capable of exploring into such rocks to distances of up to hundreds of feet. Useful but shorter probing distances are predicted for other coals, gypsums, oil shales, dry sandstones, high‐grade tar sands, and schists. Radar probing distances of less than 10 ft are predicted for most shales, clays, and fine‐grained soils. Uncombined moisture content is evidently the, governing factor. Efforts were made throughout the experiments to preserve or simulate the original moisture content of the “rocks” in place.

High Resolution Low Loss Microscopy of Crystalline Surfaces

1980 ◽  
Vol 38 ◽  
pp. 162-163
Author(s):  
William Krakow ◽  
Alec N. Broers
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Surface Topography ◽  
Secondary Electron ◽  
Objective Lens ◽  
Surface Imaging ◽  
Low Loss ◽  
Fine Grained ◽  
Scanning Electron ◽  
Crystalline Surfaces

Low-loss scanning electron microscopy can be used to investigate the surface topography of solid specimens and provides enhanced image contrast over secondary electron images. A high resolution-condenser objective lens has allowed the low-loss technique to resolve separations of Au nucleii of 50Å and smaller dimensions of 25Å in samples coated with a fine grained carbon-Au-palladium layer. An estimate of the surface topography of fine grained vapor deposited materials (20 - 100Å) and the surface topography of underlying single crystal Si in the 1000 - 2000Å range has also been investigated. Surface imaging has also been performed on single crystals using diffracted electrons scattered through 10−2 rad in a conventional TEM. However, severe tilting of the specimen is required which degrades the resolution 15 to 100 fold due to image forshortening.

scholarly journals Miniaturizing transmon qubits using van der Waals materials

2021 ◽  
Author(s):  
Abhinandan Antony ◽  
Martin Gustafsson ◽  
Guilhem Ribeill ◽  
Matthew Ware ◽  
Anjaly Rajendran ◽  
...  
Keyword(s):  
Parallel Plate ◽  
Hexagonal Boron Nitride ◽  
Van Der Waals ◽  
Spatial Density ◽  
Quantum Computers ◽  
Low Loss ◽  
Quantum Devices ◽  
Lossy Dielectrics ◽  
Circuit Components ◽  
High Coherence

Abstract Quantum computers can potentially achieve an exponential speedup versus classical computers on certain computational tasks, recently demonstrated in systems of superconducting qubits. However, the capacitor electrodes that comprise these qubits must be large in order to avoid lossy dielectrics. This tactic hinders scaling by increasing parasitic coupling among circuit components, degrading individual qubit addressability, and limiting the spatial density of qubits. Here, we take advantage of the unique properties of van der Waals (vdW) materials to reduce the qubit area by $>1000$ times while preserving the required capacitance without increasing substantial loss. Our qubits combine conventional aluminum-based Josephson junctions with parallel-plate capacitors composed of crystalline layers of superconducting niobium diselenide and insulating hexagonal-boron nitride. We measure a vdW transmon $T_1$ relaxation time of 1.06 $\mu$s, which demonstrates a path to achieve high-qubit-density quantum processors with long coherence times, and the broad utility of layered heterostructures in low-loss, high-coherence quantum devices.

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