Charge diffusion in the field-free region of charge-coupled devices

Widenhorn, Ralf; Weber‐Bargioni, Alexander; Blouke, Morley M.; Bae, Albert; Bodegom, Erik

doi:10.1117/1.3386514

Cited by 11 publications

(10 citation statements)

References 15 publications

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“…defocus), we attributed to a MTF degradation by the detector. This value of 1 for the FWHM equivalent of the MTF degradation kernel, or about 2/3 of a pixel, is not uncommon and matches values measured in dedicated experiments with similar thinned detectors (Widenhorn et al 2010;van Dam et al 2004). This issue could not be remedied with the current EEV-CCD39.…”

Section: Wfs Ccd Pixel Modulation Transfer Functionsupporting

confidence: 81%

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Gemini multiconjugate adaptive optics system review - I. Design, trade-offs and integration

Rigaut¹,

Neichel²,

Boccas³

et al. 2013

Monthly Notices of the Royal Astronomical Society

126

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The Gemini Multi-conjugate adaptive optics System (GeMS) at the Gemini South telescope in Cerro Pachón is the first sodium-based multi-Laser Guide Star (LGS) adaptive optics system. It uses five LGSs and two deformable mirrors to measure and compensate for atmospheric distortions. The GeMS project started in 1999, and saw first light in 2011. It is now in regular operation, producing images close to the diffraction limit in the near infrared, with uniform quality over a field of view of two square arcminutes. The present paper (I) is the first one in a two-paper review of GeMS. It describes the system, explains why and how it was built, discusses the design choices and trade-offs, and presents the main issues encountered during the course of the project. Finally, we briefly present the results of the system first light.

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Section: Wfs Ccd Pixel Modulation Transfer Functionsupporting

confidence: 81%

“…Through a phenomenon called pixel edge diffusion, there is a finite probability that a photon falling within the boundaries of a pixel be detected by a neighbouring pixel instead (see e.g. Widenhorn et al (2010)).…”

Section: Wfs Ccd Pixel Modulation Transfer Functionmentioning

confidence: 99%

Gemini multiconjugate adaptive optics system review - I. Design, trade-offs and integration

Rigaut¹,

Neichel²,

Boccas³

et al. 2013

Monthly Notices of the Royal Astronomical Society

126

View full text Add to dashboard Cite

show abstract

“…Since the electric field within the device is defined by and concentrated between the two electrodes (ITO substrate and AFM tip), it is orthogonal to the in‐plane/lateral hole transport . Given negligible in‐plane electric‐field, diffusion of photogenerated carriers would thus be expected to follow an exponential decay with lateral distance from the excitation source . By fitting an exponential function to each set of data, we can extract the decay coefficients to semiquantitatively compare their respective efficiencies of long‐range photocarrier transport.…”

Section: Resultsmentioning

confidence: 99%

“…38 Given negligible in-plane electric-field, diffusion of photogenerated carriers would thus be expected to follow an exponential decay with lateral distance from the excitation source. 39 By fitting an exponential function to each set of FIGURE 4 Schematic of the photoconductive AFM measurement setup (a), in which laser illumination from below can be focused on a spot directly on the scan region or displaced from it. For the measurements on the aligned device, the scan region was on the edge of a large fiber as illustrated in (b), and the photocurrent map under direct illumination is shown in (c).…”

Section: Full Papermentioning

confidence: 99%

Macroscopic alignment of poly(3‐hexylthiophene) for enhanced long‐range collection of photogenerated carriers

Bilby

Dong

et al. 2015

J Polym Sci B Polym Phys

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An epitaxy-directing solvent additive 1,3,5-trichlorobenzene is combined with an off-center spin-casting technique to produce poly(3-hexylthiophene) (P3HT) fibers with uniaxial in-plane alignment on the centimeter scale. Photoconductive atomic force microscopy (pc-AFM) is used to characterize planar heterojunction devices assembled from phenyl-C 61 butyric acid methyl ester (PCBM) acceptor and both aligned and unaligned P3HT donor. By varying the relative positions of the laser spot (site of carrier generation) and probe (site of hole extraction), it is found that devices with aligned P3HT exhibit anisotropic and greatly enhanced long-range photocarrier transport, with nearly 10% of original photocurrent measured 400 mm from the laser spot along the direction parallel to the alignment. Complementary thin film transistor (TFT) measurements reveal a factor of 3.5 difference in the hole mobilities parallel and perpendicular to the direction of alignment. Together, these findings highlight the importance of macroscopic alignment as a strategy to overcome the low mobilities of disordered polymer semiconductors.1

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“…Beyond optics, the detectors also degrade the spatial resolution of stellar images through charge disturbances processes such as CTI (Short et al 2013;Massey et al 2014), "brighterfatter" (Guyonnet et al 2015), and diffusion (Widenhorn 2010). Several tests are being carried out by ESA to characterize such effects for the charge coupled devices (CCD) of PLATO cameras, so at the present date no formal specifications for the corresponding parameters are available.…”

Section: Point Spread Functionmentioning

confidence: 99%

In-flight photometry extraction of PLATO targets

Marchiori

Samadi

Fialho

et al. 2019

A&A

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Context. The ESA PLATO space mission is devoted to unveiling and characterizing new extrasolar planets and their host stars. This mission will encompass a very large (>2100 deg2) field of view, granting it the potential to survey up to one million stars depending on the final observation strategy. The telemetry budget of the spacecraft cannot handle transmitting individual images for such a huge stellar sample at the right cadence, so the development of an appropriate strategy to perform on-board data reduction is mandatory. Aims. We employ mask-based (aperture) photometry to produce stellar light curves in flight. Our aim is thus to find the mask model that optimizes the scientific performance of the reduced data. Methods. We considered three distinct aperture models: binary mask, weighted Gaussian mask, and weighted gradient mask giving lowest noise-to-signal ratio, computed through a novel direct method. Each model was tested on synthetic images generated for 50 000 potential PLATO targets. We extracted the stellar population from the Gaia DR2 catalogue. An innovative criterion was adopted for choosing between different mask models. We designated as optimal the model providing the best compromise between sensitivity to detect true and false planet transits. We determined the optimal model based on simulated noise-to-signal ratio and frequency of threshold crossing events. Results. Our results show that, although the binary mask statistically presents a few percent higher noise-to-signal ratio compared to weighted masks, both strategies have very similar efficiency in detecting legitimate planet transits. When it comes to avoiding spurious signals from contaminant stars however the binary mask statistically collects considerably less contaminant flux than weighted masks, thereby allowing the former to deliver up to ∼30% less false transit signatures at 7.1σ detection threshold. Conclusions. Our proposed approach for choosing apertures has been proven to be decisive for the determination of a mask model capable to provide near maximum planet yield and substantially reduced occurrence of false positives for the PLATO mission. Overall, this work constitutes an important step in the design of both on-board and on-ground science data processing pipelines.

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Charge diffusion in the field-free region of charge-coupled devices

Cited by 11 publications

References 15 publications

Gemini multiconjugate adaptive optics system review - I. Design, trade-offs and integration

Gemini multiconjugate adaptive optics system review - I. Design, trade-offs and integration

Macroscopic alignment of poly(3‐hexylthiophene) for enhanced long‐range collection of photogenerated carriers

In-flight photometry extraction of PLATO targets

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