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| 2. |
- Holsti, N., et al.
(författare)
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WCET Tool Challenge 2008 : Report
- 2008
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Ingår i: OpenAccess Ser. Informatics. - 9783939897101
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Konferensbidrag (refereegranskat)abstract
- Following the successful WCET Tool Challenge in 2006, the second event in this series was organized in 2008, again with support from the ARTIST2 Network of Excellence. The WCET Tool Challenge 2008 (WCC'08) provides benchmark programs and poses a number of "analysis problems" about the dynamic, runtime properties of these programs. The participants are challenged to solve these problems with their programanalysis tools. Two kinds of problems are defined: WCET problems, which ask for bounds on the execution time of chosen parts (subprograms) of the benchmarks, under given constraints on input data; and flowanalysis problems, which ask for bounds on the number of times certain parts of the benchmark can be executed, again under some constraints. We describe the organization of WCC'08, the benchmark programs, the participating tools, and the general results, successes, and failures. Most participants found WCC'08 to be a useful test of their tools. Unlike the 2006 Challenge, the WCC'08 participants include several tools for the same target (ARM7, LPC2138), and tools that combine measurements and static analysis, as well as pure staticanalysis tools.
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| 3. |
- Wong, Winnie S., et al.
(författare)
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A pixel detector asic for dosimetry using time-over-threshold energy measurements
- 2011
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Ingår i: Radiation Measurements. - : Elsevier BV. - 1350-4487 .- 1879-0925. ; 46:12, s. 1619-1623
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Tidskriftsartikel (refereegranskat)abstract
- In this work we present the design of a chip which provides the readout of a highly segmented diode array, in which signals induced by individual X-ray photons are processed discretely. There are several benefits to this approach, including the ability to achieve a high signal to noise ratio due to the inherently low sensor capacitance, and the suppression of background noise (e.g. dark current) using an analogue threshold. The segmentation also ensures a linear behaviour even at very high dose rates. A time over threshold (ToT1) energy measurement technique provides an immediate digital value corresponding to the energy deposited onto the diode by each individual photon. Deadtime-free operation is achieved by reading out a subset of the detector segments at a time while the rest of the detector continues to process signals. This paper describes the application-specific integrated circuit (ASIC) chip which was designed to provide pre-processing of photo-induced signals in the detector and readout of the processed digital data.
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| 4. |
- Ballabriga, R., et al.
(författare)
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Medipix3 : A 64 k pixel detector readout chip working in single photon counting mode with improved spectrometric performance
- 2011
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Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier BV. - 0168-9002 .- 1872-9576. ; 633:SUPPL. 1, s. S15-S18
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Tidskriftsartikel (refereegranskat)abstract
- Medipix3 is a 256×256 channel hybrid pixel detector readout chip working in a single photon counting mode with a new inter-pixel architecture, which aims to improve the energy resolution in pixelated detectors by mitigating the effects of charge sharing between channels. Charges are summed in all 2×2 pixel clusters on the chip and a given hit is allocated locally to the pixel summing circuit with the biggest total charge on an event-by-event basis. Each pixel contains also two 12-bit binary counters with programmable depth and overflow control. The chip is configurable such that either the dimensions of each detector pixel match those of one readout pixel or detector pixels are four times greater in area than the readout pixels. In the latter case, event-by-event summing is still possible between the larger pixels. Each pixel has around 1600 transistors and the analog static power consumption is below 15 μW in the charge summing mode and 9 μW in the single pixel mode. The chip has been built in an 8-metal 0.13 μm CMOS technology. This paper describes the chip from the pixel to the periphery and first electrical results are summarized.
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| 6. |
- Campbell, M., et al.
(författare)
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Towards a new generation of pixel detector readout chips
- 2016
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Ingår i: Journal of Instrumentation. - 1748-0221. ; 11:1
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Tidskriftsartikel (refereegranskat)abstract
- The Medipix3 Collaboration has broken new ground in spectroscopic X-ray imaging and in single particle detection and tracking. This paper will review briefly the performance and limitations of the present generation of pixel detector readout chips developed by the Collaboration. Through Silicon Via technology has the potential to provide a significant improvement in the tile-ability and more flexibility in the choice of readout architecture. This has been explored in the context of 3 projects with CEA-LETI using Medipix3 and Timepix3 wafers. The next generation of chips will aim to provide improved spectroscopic imaging performance at rates compatible with human CT. It will also aim to provide full spectroscopic images with unprecedented energy and spatial resolution. Some of the opportunities and challenges posed by moving to a more dense CMOS process will be discussed.
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| 7. |
- Fröjdh, Erik, et al.
(författare)
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Count rate linearity and spectral response of the Medipix3RX chip coupled to a 300μm silicon sensor under high flux conditions
- 2014
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Ingår i: Journal of Instrumentation. - 1748-0221. ; 9:4, s. Art. no. C04028-
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Tidskriftsartikel (refereegranskat)abstract
- For clinical X-ray imaging, the detector performance under high flux conditions is very important, with typical flux rates for modern CT systems reaching 109 photons s-1 mm-2 in the direct beam. In addition, for spectral imaging a good energy resolution under these conditions is needed. This poses difficulties, since pulse pileup in the pixel electronics does not only affect the count rate, leading to a deviation from the otherwise linear behavior, but also degrades the spectral response of the detector, making k-edge subtraction and other contrast enhancement techniques less efficient. In this paper, we investigate the count rate capabilities and the energy response of the Medipix3RX chip under high flux conditions using 10 keV monochromatic photons. © CERN 2014.
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| 9. |
- Tlustos, L, et al.
(författare)
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Imaging properties of the Medipix2 system exploiting single and dual enery thresholds
- 2006
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Ingår i: IEEE Transactions on Nuclear Science. - 0018-9499 .- 1558-1578. ; 53, s. 1323-1328
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Tidskriftsartikel (refereegranskat)abstract
- Low noise, high resolution and high dose efficiency are the common requirements for most X-ray imaging applications. Especially in medical applications the dose efficiency is a necessity for detector systems. We present the imaging performance of the Medipix2 readout chip bump bonded to a 300 mu m thick Si detector as a function of the detection threshold, a free parameter not available in conventional integrating imaging systems. Spatial resolution has been measured using the modulation transfer function (MTF) and it varies between 8.2 Ip/mm and 11.0 Ip/mm at 70%. An associated measurement of noise power spectrum (NPS) permits us to derive the detective quantum efficiency (DQE) which can be as a high as 25.5 % for a broadband incoming spectrum. The influence of charge diffusion in the sensor together with threshold variation in the readout chip is discussed. Although the Medipix2 system is used in photon counting mode with a single threshold in energy, the system is also capable of counting within a given energy window of down to ~1.4 keV. First measurements and images using this feature reveal capabilities that allow to identify fluorescence and other sources of disturbance.
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