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Detective quantum efficiency of electron area detectors in electron microscopy.

McMullan G, Chen S, Henderson R, Faruqi AR - Ultramicroscopy (2009)

Bottom Line: Recent progress in detector design has created the need for a careful side-by-side comparison of the modulation transfer function (MTF) and resolution-dependent detective quantum efficiency (DQE) of existing electron detectors with those of detectors based on new technology.In the case of film, the effects of electron backscattering from both the holder and the plastic support have been investigated.We also show that part of the response of the emulsion in film comes from light generated in the plastic support.

View Article: PubMed Central - PubMed

Affiliation: MRC Laboratory of Molecular Biology, Hills Road, Cambridge CB20QH, UK. gm2@mrc-lmb.cam.ac.uk

ABSTRACT
Recent progress in detector design has created the need for a careful side-by-side comparison of the modulation transfer function (MTF) and resolution-dependent detective quantum efficiency (DQE) of existing electron detectors with those of detectors based on new technology. We present MTF and DQE measurements for four types of detector: Kodak SO-163 film, TVIPS 224 charge coupled device (CCD) detector, the Medipix2 hybrid pixel detector, and an experimental direct electron monolithic active pixel sensor (MAPS) detector. Film and CCD performance was measured at 120 and 300 keV, while results are presented for the Medipix2 at 120 keV and for the MAPS detector at 300 keV. In the case of film, the effects of electron backscattering from both the holder and the plastic support have been investigated. We also show that part of the response of the emulsion in film comes from light generated in the plastic support. Computer simulations of film and the MAPS detector have been carried out and show good agreement with experiment. The agreement enables us to conclude that the DQE of a backthinned direct electron MAPS detector is likely to be equal to, or better than, that of film at 300 keV.

No MeSH data available.


Calculated average energy per incident electron deposited within the sensitive layer of the MAPS CMOS detector as a function of incident energy using—CSDA approximation and  the FMC. The measured results, indicated by the solid circles, have been scaled from the raw ADC values.
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fig15: Calculated average energy per incident electron deposited within the sensitive layer of the MAPS CMOS detector as a function of incident energy using—CSDA approximation and the FMC. The measured results, indicated by the solid circles, have been scaled from the raw ADC values.

Mentions: The thickness of the capping and sensitive layers of the MAPS used in this work are both believed to be [7]. The variation in signal with incident energy enables us to refine these values. The minimum detectable energy determines thickness of the capping layer while the peak position and downward slope, fix the thickness of the sensitive layer. As illustrated in Fig. 15, values of 5 and for the capping and sensitive layers, respectively, give good agreement with the observed behaviour in both CSDA and FMC calculations. While the onset and peak position have been refined by parameter adjustment, the ratio of the peak height to that at 300 keV was not. The fact that it comes out close to the measured value gives confidence that the simulations are realistic.


Detective quantum efficiency of electron area detectors in electron microscopy.

McMullan G, Chen S, Henderson R, Faruqi AR - Ultramicroscopy (2009)

Calculated average energy per incident electron deposited within the sensitive layer of the MAPS CMOS detector as a function of incident energy using—CSDA approximation and  the FMC. The measured results, indicated by the solid circles, have been scaled from the raw ADC values.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2864625&req=5

fig15: Calculated average energy per incident electron deposited within the sensitive layer of the MAPS CMOS detector as a function of incident energy using—CSDA approximation and the FMC. The measured results, indicated by the solid circles, have been scaled from the raw ADC values.
Mentions: The thickness of the capping and sensitive layers of the MAPS used in this work are both believed to be [7]. The variation in signal with incident energy enables us to refine these values. The minimum detectable energy determines thickness of the capping layer while the peak position and downward slope, fix the thickness of the sensitive layer. As illustrated in Fig. 15, values of 5 and for the capping and sensitive layers, respectively, give good agreement with the observed behaviour in both CSDA and FMC calculations. While the onset and peak position have been refined by parameter adjustment, the ratio of the peak height to that at 300 keV was not. The fact that it comes out close to the measured value gives confidence that the simulations are realistic.

Bottom Line: Recent progress in detector design has created the need for a careful side-by-side comparison of the modulation transfer function (MTF) and resolution-dependent detective quantum efficiency (DQE) of existing electron detectors with those of detectors based on new technology.In the case of film, the effects of electron backscattering from both the holder and the plastic support have been investigated.We also show that part of the response of the emulsion in film comes from light generated in the plastic support.

View Article: PubMed Central - PubMed

Affiliation: MRC Laboratory of Molecular Biology, Hills Road, Cambridge CB20QH, UK. gm2@mrc-lmb.cam.ac.uk

ABSTRACT
Recent progress in detector design has created the need for a careful side-by-side comparison of the modulation transfer function (MTF) and resolution-dependent detective quantum efficiency (DQE) of existing electron detectors with those of detectors based on new technology. We present MTF and DQE measurements for four types of detector: Kodak SO-163 film, TVIPS 224 charge coupled device (CCD) detector, the Medipix2 hybrid pixel detector, and an experimental direct electron monolithic active pixel sensor (MAPS) detector. Film and CCD performance was measured at 120 and 300 keV, while results are presented for the Medipix2 at 120 keV and for the MAPS detector at 300 keV. In the case of film, the effects of electron backscattering from both the holder and the plastic support have been investigated. We also show that part of the response of the emulsion in film comes from light generated in the plastic support. Computer simulations of film and the MAPS detector have been carried out and show good agreement with experiment. The agreement enables us to conclude that the DQE of a backthinned direct electron MAPS detector is likely to be equal to, or better than, that of film at 300 keV.

No MeSH data available.