No products in LiF target by thermal neutrons

[tsiledak]

Dear experts,

I am trying with restRoot to study thermal neutrons that hit a target of LiF (0.35 microns in thickness) and produce alphas and tritons of ~ 2 MeV in a gas mixture. With geant4 as a standalone code it works! But no events are saved to output file (on the other hand with alphas etc it works!) using rest.

$ export REST_FOIL=0.35
$ export REST_ENERGY=0.000000025

and

$ restG4 neutrons.rml

with:

neutrons.rml:

and

geometry.gdml

<physvol name="gas">
    <volumeref ref="gasVolume"/>
    <position name="gasPos" unit="mm" x="0" y="0" z="0"/>
</physvol>

<physvol name="cathode">
    <volumeref ref="cathodeVolume"/>
    <position name="cathodePos" unit="mm" x="0" y="0" z="-5-foilThickness"/>
</physvol>

and

setup.gdml

		<!-- ##VERSION REST Example 08.Alphas Foil thickness : ${REST_FOIL} um Version 1.0## -->

    <!ENTITY materials SYSTEM "https://rest-for-physics.github.io/materials/rest.xml">
    ]>

<!-- All values should be in mm -->

<define>
    <constant name="world_size" value="20000"/>
	<constant name="foilThickness" value="0.001*${REST_FOIL}"/>

	<!-- Aproximate density values for 1-atm -->
	<variable name="targetGasDensity" value="1.664"/> <!-- g/cm3 -->
    <variable name="quencherDensity" value="2.51"/>
    <variable name="quencherFraction" value="0.01"/>
    <variable name="gasTemperature" value="300"/>
    <variable name="gasPressure" value="1"/>
</define>

&materials;

&geometry;


<setup name="Default" version="1.0">
    <world ref="World"/>
</setup>

I wonder whether you could have a look and let me know where is the mistake...

Thanks a lot in advance

Best regards

Georgios

[lobis]

Hello,

I remember I stumbled upon a similar problem a few months ago. In my case the problem was due to the tritium not decaying due to the configuration of the decay physics list.

I submitted a fix on #68.

In order to correcly simulate the tritium decay you will need to set the following option in the decay physics list:

<physicsList name="G4RadioactiveDecay">
    <option name="TritiumDecay" value="true"/>
</physicsList>

I'm not quite sure why this needs to be explicitly enabled. It probably has to do with the validation pipeline since enabling this new decay would probably affect in a very minor way the results of the validation simulations and this would require to update all reference files. Perhaps we can discuss this @jgalan at some point.

Please @tsiledak let us know if this solves your issue.

Regards,
Luis

[tsiledak]

neutrons.rml.txt
geometry.gdml.txt
setup.gdml.txt

I have tried but in vein...
No events are recorded...

============================= Run Summary =============================
0 events stored out of 100000 simulated events

                         [==                       DataBase Entry Added! Run Number: 1, File ID: 0                        ==]                             
                         [==                                TRestRun: Output File Updated.                                ==]                             
                         [==    - Path : /local/home/gt226504/rest-framework/install/examples/restG4/08.Alphas_n/data     ==]                             
                         [==                         - Filename : Run_0.000000025MeV_0.35um.root                          ==]                             
                         ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++                             
                         ||                                  TRestGeant4Metadata content                                   ||                             
                         ||                                   Config file : neutrons.rml                                   ||                             
                         ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++                             
                         ||                                        Name : neutrons                                         ||                             
                         ||                                        Title : Neutrons                                        ||                             
                         ||                                      REST Version : 2.4.0                                      ||                             
                         ||                                   REST Official release: Yes                                   ||                             
                         ||                                        Clean state: Yes                                        ||                             
                         ||                                     REST Commit : 075f65d7                                     ||                             
                         ||                                   REST Library version : 2.1                                   ||                             
                         ----------------------------------------------------------------------------------------------------                             
                         ||                                     Geant4 version: 11.0.3                                     ||                             
                         ||                                     Random seed: 17021981                                      ||                             
                         ||          GDML geometry:  REST Example 08.Alphas Foil thickness : 0.35 um Version 1.0           ||                             
                         ||                         GDML materials reference:  REST materials 1.5                          ||                             
                         ||                                  Sub-event time delay: 100 us                                  ||                             
                         ||                                  Magnetic field: (0, 0, 0) T                                   ||                             
                         ||                             Register empty tracks was NOT enabled                              ||                             
                         ||                                                                                                ||                             
                         ||                                ++++++++++ Generator +++++++++++                                ||                             
                         ||                               Number of generated events: 100000                               ||                             
                         ||                                     Generator type: Point                                      ||                             
                         ||                                Generator center : (0,0,-500) mm                                ||                             
                         ||                            Generator rotation : (0,0,1), angle: 0º                            ||                             
                         ||                                                                                                ||                             
                         ||                                 Particle Source Name: neutron                                  ||                             
                         ||                                Angular distribution type: Flux                                 ||                             
                         ||                            Angular distribution direction: (0,0,1)                             ||                             
                         ||                                 Energy distribution type: Mono                                 ||                             
                         ||                            Energy distribution energy: 2.5e-05 keV                             ||                             
                         ||                                                                                                ||                             
                         ||                                ++++++++++ Detector +++++++++++                                 ||                             
                         ||                                 Energy range (keV): (0, 3000)                                  ||                             
                         ||                                 Number of sensitive volumes: 1                                 ||                             
                         ||                                     Sensitive volume: gas                                      ||                             
                         ||                                  Number of active volumes: 3                                   ||                             
                         ||                          Name: gas, ID: 0, maxStep: 0.5mm , chance: 1                          ||                             
                         ||                        Name: World_PV, ID: 1, maxStep: 0mm , chance: 1                         ||                             
                         ||                         Name: cathode, ID: 2, maxStep: 0mm , chance: 1                         ||                             
                         ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++                             
                         ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++                             
                         ||                                        TRestRun content                                        ||                             
                         ||                                   Config file : neutrons.rml                                   ||                             
                         ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++                             
                         ||                                      Name : Run metadata                                       ||                             
                         ||                           Title : REST Metadata run info (template)                            ||                             
                         ||                                      REST Version : 2.4.0                                      ||                             
                         ||                                   REST Official release: Yes                                   ||                             
                         ||                                        Clean state: Yes                                        ||                             
                         ||                                     REST Commit : 075f65d7                                     ||                             
                         ||                                    REST Library version : 0                                    ||                             
                         ----------------------------------------------------------------------------------------------------                             
                         ||                                        Version : 2.4.0                                         ||                             
                         ||                                     Parent run number : 0                                      ||                             
                         ||                                         Run number : 1                                         ||                             
                         ||                                 Experiment/project : Neutrons                                  ||                             
                         ||                                       Run type : restG4                                        ||                             
                         ||                                Run tag : 0.000000025MeV_0.35um                                 ||                             
                         ||                                      Run user : gt226504                                       ||                             
                         ||                                       Run description :                                        ||                             
                         ||                      Start Date/Time : 2023/09/12 17:45:26 (1.69453e+09)                       ||                             
                         ||                       End Date/Time : 2023/09/12 17:46:10 (1.69453e+09)                        ||                             
                         ||                                         Input file :                                           ||                             
                         ||                          Output file : Run_0.000000025MeV_0.35um.root                          ||                             
                         ||                                      Number of events : 0                                      ||                             
                         ----------------------------------------------------------------------------------------------------         

[jgalan]

Hi @tsiledak and @lobis I modified the RML to enable saveAllEvents and to add the cathode as a sensitive volume.

        <parameter name="saveAllEvents" value="true"/>

and

        <detector>
            <parameter name="energyRange" value="(0,3)" units="MeV"/>
            <volume name="gas" sensitive="true" maxStepSize="0.5mm"/>
            <volume name="cathode" sensitive="true" maxStepSize="0.5mm"/>
        </detector>

Then, I get the following inside the event, when I open using restRoot Run_0.000000025MeV_0.35um.root

root [1] ev
(TRestGeant4Event *) 0x55acc89028a0
root [2] ev->PrintEvent()

EventID: 0 - SubEventID: 0
- Timestamp: Wed, 13 Sep 2023 13:19:44 +0000 (GMT) +        0 nsec
- Total deposited energy: 0
- Sensitive detectors total energy: 0
- Primary source position: (0.000, 0.000, -500.000) mm
   - Source primary particle: neutron
     Direction: (0.000, 0.000, 1.000)
     Energy: 25.00 meV

Total number of tracks: 1
 * TrackID: 1 - Particle: neutron - ParentID: 0 - Created by 'PrimaryGenerator' with initial KE of 25.00 meV
   Initial position (0.000, 0.000, -500.000) mm at time 0 - Time length of 226.34 us and spatial length of 495.00 mm
      - Hit 0 - Energy: 0 - Process: Init - Volume: World_PV - Position: (0.000, 0.000, -500.000) mm - Time: 0 - KE: 25.00 meV
      - Hit 1 - Energy: 0 - Process: Transportation - Volume: World_PV - Position: (0.000, 0.000, -5.001) mm - Time: 226.34 us - KE: 25.00 meV
      - Hit 2 - Energy: 0 - Process: nKiller - Volume: cathode - Position: (0.000, 0.000, -5.001) mm - Time: 226.34 us - KE: 25.00 meV
root [3] 

Perhaps the nKiller process might give a hint of what is going on?