Effect of Detector Material and Size on Pile-Up Elimination in Positron Burst Measurement

AbstractThe pile up patterns arising in nanoindentation are shown to be indicative of the sample crystal symmetry. To explain and interpret these patterns, complementary molecular dynamics simulations and experiments have been performed to determine the atomistic mechanisms of the nanoindentation process in single crystal Fe{110}. The simulations show that dislocation loops start from the tip and end on the crystal surface propagating outwards along the four in-plane <111> directions. These loops carry material away from the indenter and form bumps on the surface along these directions separated from the piled-up material around the indenter hole. Atoms also move in the two out-of-plane <111> directions causing propagation of subsurface defects and pile-up around the hole. This finding is confirmed by scanning force microscopy mapping of the imprint, the piling-up pattern proving a suitable indicator of the surface crystallography. Experimental force-depth curves over the depth range of a few nanometers do not appear smooth and show distinct pop-ins. On the sub-nanometer scale these pop-ins are also visible in the simulation curves and occur as a result of the initiation of the dislocation loops from the tip.

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Issues Involving Infrared Detector Material Systems

10.21236/ada470919 ◽

2006 ◽

Author(s):

Judy Wu

Keyword(s):

Infrared Detector ◽

Material Systems ◽

Detector Material

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Femtosecond Laser Passivation of GaAs Detector Material

10.21236/ada483164 ◽

2008 ◽

Author(s):

Martin Richardson ◽

Glenn Boreman ◽

Kathleen Richardson

Keyword(s):

Femtosecond Laser ◽

Detector Material

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Automated Qualitative Element Analysis of EDS Spectra with Considering Pile-Up Distortions in High Count-Rate Modes

Microscopy and Microanalysis ◽

10.1017/s1431927611006830 ◽

2011 ◽

Vol 17 (S2) ◽

pp. 1192-1193 ◽

Cited By ~ 2

Author(s):

F Eggert ◽

T Elam ◽

R Anderhalt ◽

J Nicolosi

Keyword(s):

Count Rate ◽

High Count ◽

Element Analysis ◽

High Count Rate ◽

Pile Up

Extended abstract of a paper presented at Microscopy and Microanalysis 2011 in Nashville, Tennessee, USA, August 7–August 11, 2011.

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Fully digital PET is unaffected by any deterioration in TOF resolution and TOF image quality in the wide range of routine PET count rates

EJNMMI Physics ◽

10.1186/s40658-020-00344-5 ◽

2021 ◽

Vol 8 (1) ◽

Author(s):

Julien Salvadori ◽

Freddy Odille ◽

Gilles Karcher ◽

Pierre-Yves Marie ◽

Laetitia Imbert

Keyword(s):

Image Quality ◽

Dead Time ◽

Silicon Photomultipliers ◽

Timing Resolution ◽

Upper Limits ◽

Wide Range ◽

Pile Up ◽

Digital Pet ◽

Trigger Circuit

Abstract Purpose Digital PET involving silicon photomultipliers (SiPM) provides an enhanced time-of-flight (TOF) resolution as compared with photomultiplier (PMT)-based PET, but also a better prevention of the count-related rises in dead time and pile-up effects mainly due to smaller trigger domains (i.e., the detection surfaces associated with each trigger circuit). This study aimed to determine whether this latter property could help prevent against deteriorations in TOF resolution and TOF image quality in the wide range of PET count rates documented in clinical routine. Methods Variations, according to count rates, in timing resolution and in TOF-related enhancement of the quality of phantom images were compared between the first fully digital PET (Vereos) and a PMT-based PET (Ingenuity). Single-count rate values were additionally extracted from the list-mode data of routine analog- and digital-PET exams at each 500-ms interval, in order to determine the ranges of routine PET count rates. Results Routine PET count rates were lower for the Vereos than for the Ingenuity. For Ingenuity, the upper limits were estimated at approximately 21.7 and 33.2 Mcps after injection of respectively 3 and 5 MBq.kg-1 of current 18F-labeled tracers. At 5.8 Mcps, corresponding to the lower limit of the routine count rates documented with the Ingenuity, timing resolutions provided by the scatter phantom were 326 and 621 ps for Vereos and Ingenuity, respectively. At higher count rates, timing resolution was remarkably stable for Vereos but exhibited a progressive deterioration for Ingenuity, respectively reaching 732 and 847 ps at the upper limits of 21.7 and 33.2 Mcps. The averaged TOF-related gain in signal/noise ratio was stable at approximately 2 for Vereos but decreased from 1.36 at 5.8 Mcps to 1.14 and 1.00 at respectively 21.7 and 33.2 Mcps for Ingenuity. Conclusion Contrary to the Ingenuity PMT-based PET, the Vereos fully digital PET is unaffected by any deterioration in TOF resolution and consequently, in the quality of TOF images, in the wide range of routine PET count rates. This advantage is even more striking with higher count-rates for which the preferential use of digital PET should be further recommended (i.e., dynamic PET recording, higher injected activities).

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