How Do Silicon Radiation Detectors Work in Detecting Beta and Gamma Radiations?

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Discussion Overview

The discussion revolves around the functioning of silicon radiation detectors in detecting beta and gamma radiations, particularly in the context of a second-year undergraduate radioactivity lab. Participants explore the mechanisms of energy deposition, signal detection, and the characteristics of discharge curves observed on an oscilloscope.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant expresses confusion about how the silicon detectors work, questioning whether some energy from the radiation goes into the kinetic energies of conducting electrons and is not captured as voltage.
  • Another participant mentions that induced currents result in very low net electron velocities, raising questions about the expected energy and the calibration needed for energy per electron/hole pair, noting that not all energy contributes to producing those pairs due to losses as heat.
  • There is a discussion about the layers of discharge curves observed on the oscilloscope, with participants noting that while the curves have different peaks, they appear to have the same spread or period, leading to questions about whether they are timed and if discharges occur at the same voltage.
  • Some participants highlight that the energy deposited by beta electrons varies and depends on their path through the silicon, suggesting that the characteristics of the sensor and the type of radiation influence the measurements.

Areas of Agreement / Disagreement

Participants do not reach a consensus, as there are multiple competing views regarding the energy deposition processes, the behavior of induced currents, and the interpretation of discharge curves.

Contextual Notes

Participants note limitations in understanding the calibration process for energy measurements and the dependence of energy deposition on the radiation path in silicon, but these aspects remain unresolved.

Who May Find This Useful

This discussion may be useful for undergraduate students studying radiation detection, particularly those interested in the technical workings of silicon detectors and the complexities involved in measuring beta and gamma radiation.

C_Pu
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So we are doing Radioactivity lab at second year undergraduate. I am confused about the workings of the silicon radiation detects we are using even though the demonstrators tried to explain. We are detecting beta and gamma radiations by placing sources above a silicon detector that have a small area exposed.

According to the demonstrators, the detected signal represents all the energy deposited by the radiation. But wouldn't some energy go into the kinetic energies of the conducting electrons which would not be picked up as voltage?

Also, we see layers of discharge curves on the oscilloscope, how does the discharge work? They seem to have the same spread/period, are they timed? If it's just capacitor with same threshold, shouldn't all discharge occur at the same voltage?
 
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The induced currents lead to net electron velocities of something like femtometers per second - how much energy do you expect?
In addition, this is a process that happens after all the energy got deposited, and you need a calibration of "energy per electron/hole pair" anyway because not all the energy is used to produce those pairs (most of it is lost as heat).
C_Pu said:
Also, we see layers of discharge curves on the oscilloscope, how does the discharge work? They seem to have the same spread/period, are they timed? If it's just capacitor with same threshold, shouldn't all discharge occur at the same voltage?
Is the energy the same every time?
 
mfb said:
The induced currents lead to net electron velocities of something like femtometers per second - how much energy do you expect?
In addition, this is a process that happens after all the energy got deposited, and you need a calibration of "energy per electron/hole pair" anyway because not all the energy is used to produce those pairs (most of it is lost as heat).Is the energy the same every time?
The energies from incoming beta electrons are different and energy deposited depends on the path in silicon too. We see many layers of discharge curve with different peaks but about same period.
 
C_Pu said:
and energy deposited depends on the path in silicon too
Depends on your sensor and the radiation.
C_Pu said:
We see many layers of discharge curve with different peaks but about same period.
Okay. What is unclear now?
 

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