scholarly journals On the detection of letters within redundant arrays

1986 ◽  
Vol 40 (2) ◽  
pp. 93-100 ◽  
Author(s):  
Neal F. Johnson
Keyword(s):  
Redundant Arrays

scholarly journals A coded aperture microscope for X-ray fluorescence full-field imaging

2020 ◽  
Vol 27 (6) ◽  
pp. 1703-1706
Author(s):  
D. P. Siddons ◽  
A. J. Kuczewski ◽  
A. K. Rumaiz ◽  
R. Tappero ◽  
M. Idir ◽  
...  
Keyword(s):  
Silicon Nitride ◽  
Near Field ◽  
Coded Aperture ◽  
Full Field ◽  
X Ray ◽  
Silicon Nitride Membrane ◽  
Coded Apertures ◽  
Redundant Arrays ◽  
Field Imaging ◽  
Good Contrast

The design and construction of an instrument for full-field imaging of the X-ray fluorescence emitted by a fully illuminated sample are presented. The aim is to produce an X-ray microscope with a few micrometers spatial resolution, which does not need to scan the sample. Since the fluorescence from a spatially inhomogeneous sample may contain many fluorescence lines, the optic which will provide the magnification of the emissions must be achromatic, i.e. its optical properties must be energy-independent. The only optics which fulfill this requirement in the X-ray regime are mirrors and pinholes. The throughput of a simple pinhole is very low, so the concept of coded apertures is an attractive extension which improves the throughput by having many pinholes, and retains the achromatic property. Modified uniformly redundant arrays (MURAs) with 10 µm openings and 50% open area have been fabricated using gold in a lithographic technique, fabricated on a 1 µm-thick silicon nitride membrane. The gold is 25 µm thick, offering good contrast up to 20 keV. The silicon nitride is transparent down into the soft X-ray region. MURAs with various orders, from 19 up to 73, as well as their respective negative (a mask where open and closed positions are inversed compared with the original mask), have been made. Having both signs of mask will reduce near-field artifacts and make it possible to correct for any lack of contrast.

scholarly journals Gridded and direct Epoch of Reionisation bispectrum estimates using the Murchison Widefield Array

2019 ◽  
Vol 36 ◽  
Author(s):  
Cathryn M. Trott ◽  
Catherine A. Watkinson ◽  
Christopher H. Jordan ◽  
Shintaro Yoshiura ◽  
Suman Majumdar ◽  
...  
Keyword(s):  
Power Spectrum ◽  
Point Source ◽  
Noise Level ◽  
Future Prospects ◽  
Careful Choice ◽  
Murchison Widefield Array ◽  
Using Data ◽  
Redundant Arrays ◽  
High Band ◽  
Compact Array

AbstractWe apply two methods to estimate the 21-cm bispectrum from data taken within the Epoch of Reionisation (EoR) project of the Murchison Widefield Array (MWA). Using data acquired with the Phase II compact array allows a direct bispectrum estimate to be undertaken on the multiple redundantly spaced triangles of antenna tiles, as well as an estimate based on data gridded to the uv-plane. The direct and gridded bispectrum estimators are applied to 21 h of high-band (167–197 MHz; z = 6.2–7.5) data from the 2016 and 2017 observing seasons. Analytic predictions for the bispectrum bias and variance for point-source foregrounds are derived. We compare the output of these approaches, the foreground contribution to the signal, and future prospects for measuring the bispectra with redundant and non-redundant arrays. We find that some triangle configurations yield bispectrum estimates that are consistent with the expected noise level after 10 h, while equilateral configurations are strongly foreground-dominated. Careful choice of triangle configurations may be made to reduce foreground bias that hinders power spectrum estimators, and the 21-cm bispectrum may be accessible in less time than the 21-cm power spectrum for some wave modes, with detections in hundreds of hours.

Fabrication of uniformly redundant arrays and Young's slits for coherence measurements in x-rays

2002 ◽  
Author(s):  
Nicolai A. Moldovan ◽  
David Paterson ◽  
Ralu Divan ◽  
Derrick C. Mancini ◽  
John Lin ◽  
...  
Keyword(s):  
X Rays ◽  
Redundant Arrays

scholarly journals Use of redundant arrays of inexpensive disks in orthodontic practice

2017 ◽  
Vol 151 (4) ◽  
pp. 816-820
Author(s):  
David Matthew Graham ◽  
Michael James Graham ◽  
Mel Mupparapu
Keyword(s):  
Redundant Arrays
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