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How to get induced current signal from a special shape of anode

Hello,
I simulate the zp1200(a geiger muller tube) by using Garfield++,the model structure as figure 1, and the electric field and the mesh generated from the COMSOL as figure 2.
Could you tell me how to get the induced current signal from the anode as figure 3

2 3

Maybe better to contact directly the authors:

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Hi,
sorry for not replying to your earlier e-mail on the same subject.
To simulate the induced current you will need map of the weighting potential. To calculate this map in COMSOL, you use the same mesh as you used for calculating the electric field, but apply a different set of boundary conditions, namely 1 V at the electrode you want to readout (i. e. the wire) and 0 V at the other electrodes. You can load this map in ComponentComsol using the function SetWeightingField.
You then also need to request the induced current to be calculated for this weighting field using the function AddElectrode of your Sensor object, see the “recipe” the
website.
Since you are dealing with a (very) high gas gain, it doesn’t make sense to simulate all electrons in the avalanche individually, so you probably want to use the class DriftLineRKF for simulating the electron avalanche.

Since Garfield++ is typically used for simulating detectors operating in proportional mode, I’m afraid that things won’t work out of the box if you want to simulate signals in the Geiger regime:

  • Photon feedback is not included in the simulation so you will not get secondary avalanches.
  • The effect of space charge on the electric field is taken into account (not by default anyway). If you want to do it rigorously, you would need to recalculate an electric field map in COMSOL for different stages of space charge build up.

Now we can of course give it a try to make it work, and perhaps there are some shortcuts/tricks we can use, but it will need some work…

Thank your for your rely,i will try it.

A hydrodynamic finite-element calculation is probably a better approach for your setup. You can find some pointers for doing this kind of simulation using COMSOL on this page:

https://garfieldpp.web.cern.ch/examples/avalanches_streamers/

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Thank you,emmm…
can the hydrodynamic finite-element be export to interface with Garfield++?

Thank you.

hi,
thank you for your reply.I’ve read the content of website calculation of induced currents.
but,i am not familar with ANSYS,and what is the “WSOL.lis” file refer to?
The COMSL export file contains “mesh.mphtxt”, “dielectrics.dat”, “field.txt”, how can i get the file as the same funciton as “WSOL.lis”, could you offer some examples or tips? Thanks

With the hydrodynamic approach you would simulate the induced current signal in Comsol, so I’m not sure if there’s much post-processing you could do in Garfield++ afterwards?

The equivalent in COMSOL would be a field.txt file which contains the solution for the weighting field configuration, i. e. 1 V applied to the electrode that you read out (= the wire) and 0 V to the other electrodes (= the tube).

Is there any COMSOL example to refered to?I’ve create the “Data1” in “Export”,however,how can i export another “Data2” for the weighting filed?
it there is, could you send the file to my e-mail,hatiden@msn.com
Thanks a lot.

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