Compton edge:

In a Compton scattering process, an incident photon collides with an electron in the scintillator. The amount of energy exchanged varies with angle, and is given by the formula:

(1)
\begin{align} 1/E'-1/E=1/mc^2(1-cos\theta) \end{align}

The amount of energy transferred to the scintillator varies with the angle of deflection. As θ approaches zero, none of the energy is transferred. The maximum amount of energy is transferred when θ approaches 180 degrees.

(2)
\begin{equation} ET=E-E' \end{equation}

(3)
\begin{equation} ET(max)=2E^2/(mc^2+2E) \end{equation}

It is impossible for the photon to transfer any more energy via this process, hence there is a sharp cutoff at this energy giving rise to the name Compton edge.

Compton suppression:

In gamma ray spectroscopy, Compton suppression is a technique that improves the signal by preventing data which has been corrupted by the incident gamma ray Compton scattering out of the target before depositing all of its energy. The effect is to minimize the Compton edge feature in the data.

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