867f09hw11 - (P esc = 0.4 Accounting for the photocathode...

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ELEG 867 - Devices for Light Detection from the Submillimeter to the Ultraviolet – Fall 2009 Homework #11 - due Wednesday, 25 November 2009, in class Photomultipliers and Image Intensifiers 1. Problem 7.2, from Rieke, p. 215. Hint; the difference between the effective steady current signal and the resolution of the signal into discrete pulses is discussed on p. 199 of GR. The advantage of counting is that weak pulses below a threshold can be rejected, and a very strong noise pulse (from a cosmic ray) only counts as one pulse. 2. Problem 7.3, from Rieke, p. 215. 3. Design an image intensifier, with a GaAs photocathode that is 3 μm thick, to have a photon gain of 10 3 , and operate nominally at a 550 nm wavelength. Determine the external quantum efficiency of the photocathode, from the reflectivity R, the absorption length, the electron diffusion length, and the electron escape probability
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Unformatted text preview: (P esc = 0.4). Accounting for the photocathode QE, how many phosphor output photons must each incident photoelectron produce? Account for the phosphor efficiency (0.25 photons emitted per electron at the bandgap energy corresponding to 550 nm), and calculate the required energy of electrons incident on the phosphor. Assume that the phosphor can emit multiple photons per electron in proportion to the ratio of election energy to bandgap (with the same efficiency for each photon emitted). What is the required electron accelerating voltage? Homework assignments will appear on the web at: http://www.ece.udel.edu/~kolodzey/courses/eleg867f09.html. Note: On each homework and report submission, please give your name, the due date, assignment number and the course number....
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