Mean Current of Photomultiplier at anode

In summary, we are given a weak light source with a wavelength of 600 nm and mean power of 66.2 pW, falling on a multiplier tube with 8 dynodes. The goal is to determine the mean current at the anode with an amplification of 108 and a 50% quantum efficiency for the photoelectric effect. After using the equation for kinetic energy and calculating the average current at the first dynode, we need to take into account the 50% quantum efficiency to calculate the final average current at the anode.
  • #1
sunrah
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Homework Statement


A weak light source (wavelength 600 nm, mean power 66.2 pW) falls on a multiplier tube with a cascade of 8 dynodes. How large is the mean current at the anode with an amplification of 108 and a 50% quantum efficiency for the photoelectric effect.

Homework Equations


[itex]E_{kin} = h\nu - W[/itex]

The Attempt at a Solution



No. of incident photons = No. of electrons emitted ??
[itex]N_{\gamma} = N_{e}[/itex]
[itex] \frac{P * t * λ}{h * c} = \frac{66.2pW * 1s * 600nm}{h*c} = 1.66E29[/itex] (in one second)

average current produced at first dynode = I0

[itex]I_{0} = \frac{dq}{dt} = \frac{N_{e} * e}{1s} = 3.201E-11A[/itex]

Then this is amplified by a factor 108 to give final average current at anode

I = I_{0} * 1E8 = 3.201E-3A

well, that was my idea but I don't see how the 50% efficiency fits into this. spot my mistake anyone?
 
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  • #2
The mistake is right in the first line i.e the number of incident photons =no of electrons emitted. You should use the quantum efficiency to calcualte that, i.e no. of photoelectrons=no of incident photons *Quantum efficiency . It is usually a function of the incident wavelength.
 

Related to Mean Current of Photomultiplier at anode

1. What is the mean current of a photomultiplier at the anode?

The mean current of a photomultiplier at the anode refers to the average amount of electrical current generated by the photomultiplier at its anode. This current is a measure of the amount of light that is being detected and converted into electrical signals by the photomultiplier.

2. How is the mean current of a photomultiplier at the anode measured?

The mean current of a photomultiplier at the anode is typically measured by connecting a current meter in series with the anode of the photomultiplier. The current meter will then display the average amount of current being generated by the photomultiplier.

3. What factors can affect the mean current of a photomultiplier at the anode?

There are several factors that can affect the mean current of a photomultiplier at the anode, including the intensity and wavelength of the incident light, the efficiency of the photomultiplier, and the gain or amplification of the photomultiplier's electron cascade.

4. How does the mean current of a photomultiplier at the anode relate to its sensitivity?

The mean current of a photomultiplier at the anode is directly related to its sensitivity. A higher mean current indicates a more sensitive photomultiplier, as it is able to detect and convert more light into electrical signals. However, the sensitivity of a photomultiplier also depends on other factors such as noise levels and dark current.

5. Can the mean current of a photomultiplier at the anode be increased?

Yes, the mean current of a photomultiplier at the anode can be increased by adjusting the gain or amplification of the electron cascade within the photomultiplier. Additionally, using a higher intensity light source or a more efficient photomultiplier can also increase the mean current at the anode.

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