How does a Si(Li) detector work?

Question

I've been reading up on these for a few minutes. It seems they collect energy from x-rays, or other electromagnetic rays, and then generate a voltage by means of the Compton Effect and Photoelectric Effect.

The Compton Effect is when a photon collides with an electron resulted in a change in energy and direction of both photon and electron.

The photoelectric effect is when an atom absorbs a photon and emits and electron.

How do these two effects work together in a Si(Li) detector? What causes one effect to take place and not the other?

Answer 1

compton effect (or compton scattering) happens when high energy photon interacts with a loosely bound electron in an atom's outer shell. this type of electron is sometimes called "free electron". the interaction probability depends on the electron density of the material & nearly independent of Z. high Z materials are consider to have "free electron". so probability of compton interation is higher in high Z atoms and is proportional to mass density (kg/m3).

photoelectric effect (PE) happens when high energy photon interacts with a tightly bound inner orbit electron and transfer all of its energy to the electron causing it to be ejected. outer shell electron will fill this vacancy and photons are produced. probability of PE is proportional to Z^3 and inversely proportional to E^3

by understanding the nature of interaction of photon with matter, we will know which effect will take place (or dominant) and not the other one.

Si(Li) detector is a scintillation detector. the crystal is arranged in lattice pattern. when the crystal absorbed radiation, its electrons will be excited and "jump" from its initial state (in the valance band) into higher state and being trapped in the conduction band. these electrons will remain there.

once u heated the detector with sufficient temperature, these electrons will release their energy and return to the ground state (valance band). the energy is released in the form of light. the light can be measured using photomultiplier tube and is amplified and displayed on a meter.

Answer 2

They both seem to take place :

have a look at this and the references

http://www.fz-juelich.de/ikp/detektorlab...

then try

http://www-ssrl.slac.stanford.edu/~txrf/...

best of luck