A Monte Carlo model has been developed for epitaxial silicon active pixel sensor arrays. Ionization generation of 55Fe
X-rays and high energy electrons are modeled directly using random numbers that follow an exponential distribution and
a Bichsel distribution, respectively. Both the simulation and measurement have identified a considerable bulk-silicon
substrate contribution to collected ionization electrons, which is important in accurate modeling of sensor response to
high energy electrons.
KEYWORDS: Sensors, Active sensors, Signal to noise ratio, Electron microscopy, Diodes, CCD image sensors, Detector arrays, CCD cameras, Charge-coupled devices, Electron beams
There is an urgent need to replace film and CCD cameras as recording instruments for transmission electron
microscopy (TEM). Film is too cumbersome to process and CCD cameras have low resolution, marginal to poor
signal-to-noise ratio for single electron detection and high spatial distortion. To find a replacement device, we have
tested a high sensitivity active pixel sensor (APS) array currently being developed for nuclear physics. The tests were
done at 120 keV in a JEOL 1200 electron microscope. At this energy, each electron produced on average a signal-tonoise
ratio about 20/1. The spatial resolution was also excellent with the full width at half maximum (FWHM) about
20 microns. Since it is very radiation tolerant and has almost no spatial distortion, the above tests showed that a high
sensitivity CMOS APS array holds great promise as a direct detection device for electron microscopy.
S. Barwick, J. Ahrens, X. Bai, T. Becka, K.-H. Becker, D. Bertrand, F. Binon, A. Biron, S. Boser, O. Botner, O. Bouhali, T. Burgess, S. Carius, T. Castermans, D. Chirkin, J. Conrad, J. Cooley, D. Cowen, A. Davour, C. De Clercq, T. DeYoung, P. Desiati, J.-P. Dewulf, P. Doksus, P. Ekstrom, T. Feser, T. Gaisser, M. Gaug, L. Gerhardt, A. Goldschmidt, A. Hallgren, Francis Halzen, K. Hanson, R. Hardtke, T. Hauschildt, M. Hellwig, P. Herquet, G. Hill, P. Hulth, K. Hultqvist, J. Hundertmark, Janet Jacobsen, A. Karle, L. Kopke, M. Kowalski, Kyler Kuehn, J. Lamoureux, H. Leich, M. Leuthold, P. Lindahl, J. Madsen, P. Marciniewski, Howard Matis, C. McParland, Y. Minaeva, P. Miocinovic, R. Morse, R. Nahnhauer, T. Neunhöffer, P. Niessen, David Nygren, Hakki Ogelman, Ph. Olbrechts, C. Pérez de los Heros, A. Pohl, P. Price, G. Przybylski, K. Rawlins, E. Resconi, W. Rhode, M. Ribordy, S. Richter, J. Rodríguez Martino, D. Ross, H. Sander, T. Schmidt, D. Schneider, R. Schwarz, A. Silvestri, M. Solarz, G. Spiczak, C. Spiering, D. Steele, P. Steffen, R. Stokstad, P. Sudhoff, K. Sulanke, I. Taboada, L. Thollander, S. Tilav, C. Walck, C. Weinheimer, C. Wiebusch, C. Wiedemann, R. Wischnewski, H. Wissing, K. Woschnagg, Gaurang Yodh, S. Young
This paper briefly describes the principle of operation and science goals of the AMANDA high energy neutrino telescope located at the South Pole, Antarctica. Results from an earlier phase of the telescope, called AMANDA-B10, demonstrate both reliable operation and the broad astrophysical reach of this device, which includes searches for a variety of sources of ultrahigh energy neutrinos: generic point sources, Gamma-Ray Bursts and diffuse sources. The predicted sensitivity and angular resolution of the telescope were confirmed by studies of atmospheric muon and neutrino backgrounds. We also report on the status of the analysis from AMANDA-II, a larger version with far greater capabilities. At this stage of analysis, details of the ice properties and other systematic uncertainties of the AMANDA-II telescope are under study, but we have made progress toward critical science objectives. In particular, we focus on the search for continuous emission from astrophysical point sources and the search for correlated neutrino emission from Gamma Ray Bursts detected by BATSE before decommissioning in May 2000. During the next two years, we expect to exploit the full potential of AMANDA-II with the installation of a new data acquisition system that records full waveforms from the in-ice optical sensors.
Integrated CMOS Active Pixel Sensor (APS) arrays have been fabricated and tested using X-ray and electron sources. The 128 by 128 pixel arrays, designed in a standard 0.25 micron process, use a ~10 micron epitaxial silicon layer as a deep detection region. The epitaxial layer has a much greater thickness than the surface features used by standard CMOS APS, leading to stronger signals and potentially better signal-to-noise ratio (SNR). On the other hand, minority carriers confined within the epitaxial region may diffuse to neighboring pixels, blur images and reduce peak signal intensity. But for low-rate, sparse-event images, centroid analysis of this diffusion may be used to increase position resolution. Careful trade-offs involving pixel size and sense-node area verses capacitance must be made to optimize overall performance. The prototype sensor arrays, therefore, include a range of different pixel designs, including different APS circuits and a range of different epitaxial layer contact structures. The fabricated arrays were tested with 1.5 GeV electrons and Fe-55 X-ray sources, yielding a measured noise of 13 electrons RMS and an SNR for single Fe-55 X-rays of greater than 38.
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