HW7 - EE 119 Homework 7 Professor: Jeff Bokor TA: Xi Luo...

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EE 119 Homework 7 Professor: Jeff Bokor TA: Xi Luo Due Tuesday , March 30 th 2010 (Please submit your answers in EE119 homework box located in 240 Cory Hall) 1. Photomultiplier tube a) Assume constant quantum efficiency and constant power. Plot the variation of cathode current as a function of wavelength between 200nm and 1 μ m. (Assume a current of 10nA at 200nm). b) If the photocathode material has a work function of 1.8eV, what is the maximum wavelength it can detect? 2. Dark Current a) If the cathode dark current of a PMT is found to be 2x10 4 e/sec at room temperature (300K), what is the equivalent shot noise to this dark current? Assume the bandwidth is 1Hz. b) We can actually distinguish a light signal that only exceeds the shot noise level of the dark current. Based on this criterion, what is the minimum power that can be detected? Assume the quantum efficiency is 50% at
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HW7 - EE 119 Homework 7 Professor: Jeff Bokor TA: Xi Luo...

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