[Gate-users] Problem with the coincidence

[Jinxia Guo]

Dear gate users,

I encountered a problem when I inspection the time difference of two singles
in a coincidence. In the simulation, there are many coincidences in which
the time difference of two singles is larger than the coincidence window. I
do two simulation. In the first one, the time resolution is set to 200ps and
the coincidence window is set to 200ps. In the second one, the time
resolution is set to 0 and the coincidence window is set to 200ps. In both
simulation, the problem exists. I can't find why this happened with chapter8
of GATE user guide. So who know how gate does its coincidence？Why the time
difference of singles in coincidences is larger than the coincidence window?

In addition to the above simulation, I do another two simulation. In first
one, the time resolution is 300ps and coincidence window is 10ns. In second
one, the time resolution is 300ps too and coincidence window is 100ns. I
found there are more coincidences in the first simulation than in the second
simulation,about five times larger.Then who can explain it？

By the way, in all simulations, the diameter of simulated PET ring is about
82cm. And the simulation time is the same.

Hope for help. Thank you!

-
Jinxia Guo
School of Life Sci&Tech
D11 Building Room 503

Huazhong Univ. of Sci. & Tech

1037 Luoyu Road, Wuhan 430074, China
Tel:+86-27-8779-2294