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- TL;DR Summary
- I have to count the number of photons detected by a photodiode, I want to do it based on voltage/current measurements, but my professor wants me to do some statistical analysis which I think don't apply in this case

Hello, I'm working on a scintillation device to detect protons, I have a disagreement with one professor and I would like your opinion.

There is one photodiode model we want to use to measure the light intensity from the scintillators, and we want to relate the signal of that photodiode with the number of photons it is absorbing.

To do this we took a CAEN DT5751, connected a photodiode to it, and put an LED in front of the photodiode. This DT5751 samples the signal, measures its voltage, and counts how many times it has seen such a voltage, producing a histogram with a gaussian distribution, so far so good.

What I want to do is to get the mean voltage, divide by the resistance the photodiode sees (50 ohms, I measured), get the current produced by the photodiode, and use the photodiode's responsivity to get the mean number of photons. Easy piecy.

BUT my professor says that there's a better way (aka "I want this in your report"). We know that the statistical distribution of the photons is a Poissonian Distribution when N approaches infinity, which is a gaussian where sigma^2 = mean. And he is right, that distribution does fit with our results.

Then he says that we should be able to use the quantum efficiency of the photodiode and the number of counts to know the number of photons. Equation 5.57 here

Here's my problem with that reasoning: Our set up does not count photons, it counts current pulses, and each pulse is produced by the photodiode when it absorbs a bunch of photons, something like 10^10 at least, those formulas is for when you have a device capable of counting individual photons, so those formulas don't apply.

I brought up this point but he just told me to read more, and I did, I read this and this but he just said he had better things to do than to teach me what I should already know.

Maybe he's right, maybe there is a way to use photon statistics to get the total number of photons with this set up, so I come to you, is there?, has ay of you done something similar?, because I am lost.

PD:

The manual of the DT5751 says that "Input dynamic is 1 Vpp" and the values are stored with "16 MSB". I take that to mean that it has 2^16 slots to store all the values from 0 to 1 volts. For example a value of "20,000" would be 20,000/2^16 = 0.35 volts, is that correct?

There is one photodiode model we want to use to measure the light intensity from the scintillators, and we want to relate the signal of that photodiode with the number of photons it is absorbing.

To do this we took a CAEN DT5751, connected a photodiode to it, and put an LED in front of the photodiode. This DT5751 samples the signal, measures its voltage, and counts how many times it has seen such a voltage, producing a histogram with a gaussian distribution, so far so good.

What I want to do is to get the mean voltage, divide by the resistance the photodiode sees (50 ohms, I measured), get the current produced by the photodiode, and use the photodiode's responsivity to get the mean number of photons. Easy piecy.

BUT my professor says that there's a better way (aka "I want this in your report"). We know that the statistical distribution of the photons is a Poissonian Distribution when N approaches infinity, which is a gaussian where sigma^2 = mean. And he is right, that distribution does fit with our results.

Then he says that we should be able to use the quantum efficiency of the photodiode and the number of counts to know the number of photons. Equation 5.57 here

Here's my problem with that reasoning: Our set up does not count photons, it counts current pulses, and each pulse is produced by the photodiode when it absorbs a bunch of photons, something like 10^10 at least, those formulas is for when you have a device capable of counting individual photons, so those formulas don't apply.

I brought up this point but he just told me to read more, and I did, I read this and this but he just said he had better things to do than to teach me what I should already know.

Maybe he's right, maybe there is a way to use photon statistics to get the total number of photons with this set up, so I come to you, is there?, has ay of you done something similar?, because I am lost.

PD:

The manual of the DT5751 says that "Input dynamic is 1 Vpp" and the values are stored with "16 MSB". I take that to mean that it has 2^16 slots to store all the values from 0 to 1 volts. For example a value of "20,000" would be 20,000/2^16 = 0.35 volts, is that correct?