[Gate-users] Simulate a beam with spaced bunches in GATE

[Salvatore Di Guida]

Dear GATE users and developers,
since I have been using the framework for few weeks, I apologize for my misunderstandings and mistakes.
I have simulated the detector I am working on as two water boxes (equivalent to gas detectors), two plastic scintillator boxes plus a scanner system made up of 30 plastic scintillators. I have attached one phase space to each water box (in order to describe the incoming particles from the source and from the first box, respectively), to the air box between the water boxes (in order to look at the particles outgoing the first water box) and to the air box between the second water fox and the first scintillator (in order to look at the particles outgoing the second water box). Moreover, I have defined a proton pencil beam source: I have implemented it both via G4 GeneralParticleSource and using the PencilBeam template in GATE.
If you like, you can check the geometry and the sources in details in the archive I am attaching to this mail: there you can find the macros I am using. I am working with GATE 6.1 on vGATE 2.0.
The output I want to retrieve is, for each proton, the x and y position in each water box, and the energy deposition in each level of the scanner system.
In my first attempt, I simply created the geometry, the source, and the digitizer system, and launched the simulation with 1000 primaries, producing ROOT files as output. My idea was to distinguish the incoming protons by the (runID, eventID) pair: unfortunately, the phase space does not store this piece of information [1].
Then, since both the phase space and the scanner keep time information, my next attempt was to calculate the coincidences of each proton in the water boxes and in the first scintillator: in this way, I could mark the protons propagating outside the scanner with the same (runID, eventID) pair established inside it. Unfortunately, both sources generate all the protons at t = 0, so it is impossible to get an adequate result via coincidence computations [2].
Next, I tried to overcome this issue using time slices in Data Acquisition: I defined 1000 time slices, where each slice has a time duration larger than the time of flight of the proton, so that I had one primary per slice, and the association between data in water and data in the scanner could be quite easy. Unfortunately, when the second time slice starts, GATE crashes with a segmentation violation with both the PencilBeam source and with GPS source (even when I tried to set GeneralParticleSource::number or setActivity in GATE). Debugging with gdb did not help.

My question is: is there a way in GATE to produce a beam source where a given number of protons are grouped in bunches spaced by a given time interval (say: 100 protons-per-bunch, bunches spaced by 100 ms).

Thanks in advance for your help!

Salvatore

[1]
$ root -l
root [] TFile* gem0RootFile = TFile::Open("GEM0PHS_1000primaries_perfectPBS.root")
root [] TTree* gem0PhaseSpaceTree = (TTree*) gem0RootFile->Get( "PhaseSpace" )
root [] phaseSpaceTree->Print()

[2] the source is 0.05 mm far from the phase space, which is at the origin of the world; so, all protons enter the water box associated to the phase space at t > 0:
root [] TFile* gem0RootFile = TFile::Open("GEM0PHS_1000primaries_perfectPBS.root")
root [] TTree* gem0PhaseSpaceTree = (TTree*) gem0RootFile->Get( "PhaseSpace" )
root [] gem0PhaseSpaceTree->Scan( "ParticleName:Time:X:Y:Z:dX:dY:dZ:Ekine" )
************************************************************************************************************************
*    Row   * ParticleN *      Time *         X *         Y *         Z *        dX *        dY *        dZ *     Ekine *
************************************************************************************************************************
*        0 *    proton * 0.0003519 *         0 *         0 *         0 * -2.63e-08 * 2.610e-08 *         1 *       100 *
*        1 *    proton * 0.0003519 *         0 *         0 *         0 * 2.421e-08 * 9.183e-11 *         1 *       100 *
*        2 *    proton * 0.0003519 *         0 *         0 *         0 * 1.011e-09 * 2.843e-09 *         1 *       100 *
*        3 *    proton * 0.0003519 *         0 *         0 *         0 * -5.11e-09 * 7.478e-10 *         1 *       100 *
*        4 *    proton * 0.0003519 *         0 *         0 *         0 * 2.031e-08 * -2.61e-08 *         1 *       100 *
*        5 *    proton * 0.0003519 *         0 *         0 *         0 * 2.153e-08 * 9.473e-09 *         1 *       100 *
...
And here it is how the ROOT file for the phase space between the two water boxes look like: there is a very slight difference in timing between protons...
root [] TFile* gemSpacingRootFile = TFile::Open("GEMSpacingPHS_1000primaries_perfectPBS.root")
root [] TTree* gemSpacingPhaseSpaceTree = (TTree*) gemSpacingRootFile->Get( "PhaseSpace" )
root [] gemSpacingPhaseSpaceTree->Scan( "ParticleName:Time:X:Y:Z:dX:dY:dZ:Ekine" )
************************************************************************************************************************
*    Row   * ParticleN *      Time *         X *         Y *         Z *        dX *        dY *        dZ *     Ekine *
************************************************************************************************************************
*        0 *    proton * 0.0194233 * 0.0030443 * -0.001321 * 2.7000000 * 0.0042755 * -0.001657 * 0.9999895 * 98.147529 *
*        1 *    proton * 0.0194286 * -0.002575 * 0.0078605 * 2.7000000 * -0.002732 * 0.0060394 * 0.9999780 * 97.927230 *
*        2 *    proton * 0.0194189 * 0.0081350 * -0.003375 * 2.7000000 * 0.0061967 * -0.000981 * 0.9999803 * 98.123619 *
*        3 *    proton * 0.0194209 * 0.0102742 * -0.006316 * 2.7000000 * -0.002067 * -0.004013 * 0.9999898 * 97.984443 *
*        4 *    proton * 0.0194191 * -0.007278 * 0.0019697 * 2.7000000 * -0.005616 * 0.0024906 * 0.9999811 * 98.163551 *
...
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