[Gate-users] Use of ion source with Gate8.2

[Gunjan Kayal]

Dear Gate-users

We found an unusual behaviour with Gate 8.2 (Geant10.5.0) when using the ion source. 
When comparing the spherical shell DPKs (Dose Point Kernels) between Gate 8.1 and Gate 8.2, there was a difference in absorbed dose up to 10% (for spheres close to the source) and a difference up to 40% for far away spheres (~10 cm from source).
After many tests, we realised that this difference was coming from Geant4 versions, namely 10.4.2 (GATE 8.1) and 10.5.0 (GATE 8.2). 

Seems like Geant4 10.5.0 includes some changes regarding the ion source but nothing relating to this is written in the release notes. 

We performed some test:
Gate 8.2 with Geant 10.5.1 (i.e. with the patch 1)
Gate8.2 with Geant 10.6.0 (beta)
And this gives the same results as Gate 8.1 with Geant10.4.2 (max difference is 1%)

So it seems that this Geant4 issue was fixed. Therefore, we recommend being cautious when using ion source with Geant4 10.5.0.
Just a reminder, the virtual GATE8.2 is installed with Geant4 10.5.0.

Thank you.

Have a good day.

Regards.
Gunjan (on behalf of CRCT, INSERM team)


Gunjan KAYAL
Research Scholar (Ph.D)
SCK.CEN and INSERM,CRCT U1037, Equipe 15
Belgium and France
Tel: +33 (0)7 69 83 00 70



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