Cyclotron target to predict activation of Havar foils


I am simulating the irradiation of a cyclotron target to predict activation of Havar foils and target components. I started making a simple model of the target, but didn’t get the expected results, therefore I bombarded with a proton beam a simple volume of H2O (oxygen-18) to simulate the 18O(p,n)18F reaction. I compared the results of the reaction yield (GBq/C) at three different beam energies, but my results are very far from published values. I also calculated analytically the number of activated 18F nuclei with IAEA recommended cross sections at different energies with my simulation, but once again my results are very far from what I was expecting. I am using example Activation for the simulation. Can anyone give some advice? Does this mean Geant4 is not using the correct cross sections?


You can download different/special cross section data for a few applications, which you can use instead of the standard corss section libraries.
There are many Evaluated neutron cross section Labraries at
and there is the TENDL library at

What is your beam energy? For low-energy proton reactions (around 20 MeV) the TENDL library could improve your results.
I recommend you take a look into the advanced example ‘STCyclotron’ because this example seems to fit your problem pretty well.


@MaxLoep my energy is 16.5MeV

As Max said, Geant4 used the TENDL database if you select the particleHP physics. TENDL is based on the existing experimental cross sections plus TALYS interpolations. You can see the differences at
I did the exercise long time ago of correcting the Geant4 data with the IAEA medical database. Delete the files G4TENDL1.4/Proton/Inelastic/F02/8_18_Oxygen.z , G4TENDL1.4/Proton/Inelastic/CrossSection/8_18_Oxygen.z and uncrompress the tar ball at in G4TENDL1.4/Proton
It is based in TENDL 2009 database (G4TENDL1.4 uses TENDL 2019) but it will serve you

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you do not specified what Geant4 version and what Physics List you are using. When you say cross section is far different from known value I would ask how you get this? I would agree that TENDL cross section may help, it may be enabled by choice of corresponding Physics List.


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