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All I know is that detecting the deflecting alpha particles was a very tedious process, so much so that that was probably one reason why he asked Hans Geiger and Ernest Marsden to do the experiment. Modern day recreation of the experiment uses light detectors. (In the 1950s they gave white lines on a TV screen when alpha particles were detected and presently a doorbell sound. Or at least that's what I found on YouTube.)

I am curious about how the deflection was detected in the original experiment. My textbook says they used a microscope. But how? Wouldn't they have to place the microscope inside the vacuum chamber?

Also secondly where were the scintillating effects produced? Was it produced on a zinc sulphide coated screen or somewhere else?

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    $\begingroup$ The article Rutherford Scattering offers the desired details. Referring to a diagram included in the article: "By means of a diaphragm placed at D, a pencil of alpha particles was directed normally on to the scattering foil F. By rotating the microscope [M] the alpha particles scattered in different directions could be observed on the screen S." further noting that "A single alpha caused a slight fluorescence on the zinc sulphide screen S at the end of the microscope." $\endgroup$
    – nwr
    Feb 6, 2022 at 23:06
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    $\begingroup$ Indeed, as noted by @nwr, the flourescent ZnS screen was the go-to detection device for energetic particles for decades (first with electrons, then to, well, everything else). The unreliable part was the humans, who first had to let their eyes adapt to the dark, and then could only be reliable for ~10-15 minutes at a time before their eyeballs started seeing flashes on their own. $\endgroup$
    – Jon Custer
    Feb 7, 2022 at 14:30
  • $\begingroup$ @nwr what does diaphragm mean in this context? like a thin screen? no but then there's already another screen right there $\endgroup$ Feb 8, 2022 at 10:52
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    $\begingroup$ I assume that it means a barrier with a small hole at its centre which used to ensure that the only particles able to arrive at the screen S do so orthogonally. However, I know very little physics so perhaps user @Conifold would be able to provide a better description. $\endgroup$
    – nwr
    Feb 8, 2022 at 16:57

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