A new mask-antimask coded-aperture telescope for hard X-ray astronomy

Braga, J.; Villela, T.; Jayanthi, U. B.; D'Amico, F.; Neri, J.A.C.F.

doi:10.1007/bf00576323

Cited by 28 publications

(15 citation statements)

References 13 publications

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“…Even though other mask pattern arrangements have been found to equal and/or surpass MURA signal-to-noise ratios [13,8,14,15], MURA patterns exhibit ideal imaging properties because the number of artifacts is minimized due to auto-correlative properties [16]. In addition, due to the antisymmetry of the MURA pattern under rotation, background subtraction is uncomplicated and efficient [17].…”

Section: Coded-aperture Imaging Variables Of Interestmentioning

confidence: 99%

“…In rotating an anti-symmetric mask by 901 and exposing the detector plane, an anti-mask exposure is obtained because the spatial locations of the open and closed mask positions are exchanged [17,18]. Subtracting the anti-mask counts from the mask counts suppresses image artifacts and provides an in situ background subtraction [11].…”

Section: Coded-aperture Imaging Variables Of Interestmentioning

confidence: 99%

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Correlated statistical uncertainties in coded-aperture imaging

Fleenor

Blackston

Ziock

2015

Nuclear Instruments and Methods in Physics Research Section A:

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a b s t r a c tIn nuclear security applications, coded-aperture imagers can provide a wealth of information regarding the attributes of both the radioactive and nonradioactive components of the objects being imaged. However, for optimum benefit to the community, spatial attributes need to be determined in a quantitative and statistically meaningful manner. To address a deficiency of quantifiable errors in coded-aperture imaging, we present uncertainty matrices containing covariance terms between image pixels for MURA mask patterns. We calculated these correlated uncertainties as functions of variation in mask rank, mask pattern over-sampling, and whether or not anti-mask data are included. Utilizing simulated point source data, we found that correlations arose when two or more image pixels were summed. Furthermore, we found that the presence of correlations was heightened by the process of over-sampling, while correlations were suppressed by the inclusion of anti-mask data and with increased mask rank. As an application of this result, we explored how statistics-based alarming is impacted in a radiological search scenario.

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Section: Coded-aperture Imaging Variables Of Interestmentioning

confidence: 99%

Section: Coded-aperture Imaging Variables Of Interestmentioning

confidence: 99%

Correlated statistical uncertainties in coded-aperture imaging

Fleenor

Blackston

Ziock

2015

Nuclear Instruments and Methods in Physics Research Section A:

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“…En effet, il est nécessaire de minimiser le poids de la caméra, par conséquent a été privilégié dans la première campagne de mesure le traitement logiciel des images (calcul puis soustraction d'un bruit de fond moyen sur les images). Cette solution n'étant pas entièrement satisfaisante, une autre méthode a été mise en oeuvre dans la seconde campagne, la mesure masque-antimasque : deux images successives sont prises en effectuant une rotation du masque d'un quart de tour pour la deuxième mesure (Braga et al, 1991). La soustraction des deux images permet de retirer la composante bruit de fond en ne conservant que le signal produit par les sources se trouvant dans le champ de vue de la caméra.…”

Section: Gampix Gamma Camera On the Tripod During Measurements In Theunclassified

Un nouveau système d’imagerie gamma portable dédié à la détection et à la visualisation des points chauds dans les centrales nucléaires

Gaillard-Lecanu¹,

Hameau²,

Onillon³

et al. 2013

Radioprotection

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RÉSUMÉDans une centrale nucléaire (CNPE), la localisation des points chauds est une préoc-cupation importante, car ils participent à la dose que reçoivent les intervenants, en particulier lors des opérations de maintenance. Article publié par EDP SciencesVol. 48, n°4 , pages 471 à 492 E. GAILLARD-LECANU et al. 472 RADIOPROTECTION -VOL. 48 -N°4 (2013) image with a visible image, in order to locate radioactive sources in a given area. Onsite measurements at the Tricastin EDF NPP, combined with specific developments at CEA, have been carried out in order to meet the particular environmental and radiological conditions experienced in such industrial facilities: the relatively high energy of cobalt-60 (1.17 and 1.33 MeV) and the existence of an ubiquitous background. This article will present the specifications required, the corresponding improvements and the main results obtained during the on-site measurements campaigns. Even if they were dedicated to the qualification of the camera, the tests carried out showed useful results like the leakage lines along a lead protection and the displacement of a hot spot in a pipe (compared to its identified position). At the end, further developments are presented.

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“…29,30,33 The images presented here were obtained using a 320 mCi 137 Cs radioactive source placed ͑aligned with a laser beam͒ in the center of the FOV, 68 m away from the PSD. This distance is long enough so as to make the magnification of the mask shadow negligible ͑the detector scale adjustment that would be needed, of 0.3 mm, is much less than the detector spatial resolution of ϳ1 cm͒.…”

Section: Laboratory Imagesmentioning

confidence: 99%

Development of the imaging system of the balloon-borne gamma-ray telescope Máscara Codificada (MASCO)

Braga

D'Amico

Villela

et al. 2002

Review of Scientific Instruments

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We report laboratory imaging results of a balloon-borne gamma-ray imaging telescope, Máscara Codificada ͑Portuguese for ''coded mask,''͒ designed to obtain high angular resolution ͑ϳ14 arcmin͒ images of the sky in the 50 keV-1.8 MeV energy range. The instrument incorporates a coded mask with an aperture pattern based on a 19ϫ19-element modified uniformly redundant array ͑MURA͒. This pattern belongs to a subclass of MURAs that are almost completely antisymmetrical for 90°rotations with respect to the lower-right corner of the central element, which allows the implementation of an antimask by a single rotation of the whole mask by 90°. The symmetry properties of the MURAs are discussed. The algorithm for determining the position of the gamma-ray interactions on the instrument's main detector is described and the results of laboratory tests of the imaging system are presented. The mask-antimask subtraction, applied after a flat-fielding procedure, produced a 60% increase in the signal-to-noise ratio of a strong ͑ϳ100͒ point source ͑662 keV photons coming from a 137 Cs radioactive source͒ image by eliminating systematic distortions in the instrumental background measured over the detector plane.

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A new mask-antimask coded-aperture telescope for hard X-ray astronomy

Cited by 28 publications

References 13 publications

Correlated statistical uncertainties in coded-aperture imaging

Correlated statistical uncertainties in coded-aperture imaging

Un nouveau système d’imagerie gamma portable dédié à la détection et à la visualisation des points chauds dans les centrales nucléaires

Development of the imaging system of the balloon-borne gamma-ray telescope Máscara Codificada (MASCO)

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