Understanding Dynode Multiplication in Scintillation Detectors

[m-i-t-o]

Hi all,my question is on dynodes. For ex: in scintillation detector we ususally say that a visible photon when incident on photocathode,undergoes photoelectric effect.But what the process occurring on dynodes when this photoelectron incident on it.
Electrons are multiplying successively as moving from one dynode to other.What you called such a process,this is not photo electric effect! as instead of photon electron is incidenting on material.
Please help

 

[malawi_glenn]

The photoelectric effect is just creating the first electrons, then these electrons are accelerated towards metal plates and will blast out electrons from it, and these will be accelerated to another metal piece etc.

The electrons are IONIZING the atoms in the metal, ionization due to collisions you might call it. (c.f collision ionization in hot and dense astrophysical gases etc.)

 

[sir-pinski]

Hi there,

Thank you for your question regarding dynode multiplication in scintillation detectors. Dynode multiplication is a crucial process in scintillation detectors, as it allows for the amplification of the signal produced by the initial interaction of a photon with the photocathode.

To understand dynode multiplication, it is important to first understand the basic principles of a scintillation detector. When a photon interacts with the scintillator material, it produces a burst of light that is then detected by the photocathode. The photocathode is a material that is sensitive to light and can release electrons when exposed to it. These electrons are then accelerated towards the dynodes, which are a series of metal plates with a high voltage applied to them.

When the photoelectron from the photocathode reaches the first dynode, it is accelerated towards it due to the high voltage difference. As it hits the dynode, it releases multiple secondary electrons through a process called secondary emission. These secondary electrons are then accelerated towards the next dynode, where the process repeats itself. This multiplication of electrons continues until the electrons reach the anode, where they are collected and measured as the final signal.

This process is known as dynode multiplication or electron cascade. It is not the same as the photoelectric effect, as you correctly pointed out. The photoelectric effect refers to the ejection of electrons from a material when it is exposed to light. In the case of dynode multiplication, the electrons are not being ejected by the light itself, but rather by the energy they receive from the initial photoelectron.

I hope this helps to clarify the process of dynode multiplication in scintillation detectors. Please let me know if you have any other questions.