The energy of photon

Garfield++
1

When I use this method called transportphoton() in gas medium, I found that when the energy of photon is greater than 1 Mev, there is very little number of generated electron.

What is the Energy range of photon Garfield++ applicated?

What else method can apply the energy of photon is greater than 1 Mev?

Wait to your reply .Thanks a lot!

2

Compton scattering + Pair production

3

Beyond the K shell edge, the photoabsorption cross-section decreases quite fast and at 1 MeV (depending on the size of your gas volume of course) the probability for photon to interact via photo absorption inside the gas medium becomes small.