Trouble plotting signal

Hi Piet,

Looking at my results I’ve just had a thought. When calculating weighting fields should I be grounding all elements, or only the elements I intend to use as readout strips. i.e. I should leave the anode strips and cathode strips at their respective potentials and only ground the readout strips (with each strip field set to 1V for their respective weighting field file).

Thanks,

Connor

To calculate the weighting potential you should apply 1 V to the elements you want to use as readout electrodes and ground all other elements.

Dear Connor,

Thank you for the plot. I do not immediately see a problem with this.

I am not sure it would be the signal form the mesh. While you indeed expect a polarity change in the ion tail, I would expect the polarity change to happen later and the negative fluke to be longer and to have a lower amplitude.

If I am not misinterpreting your plots, it looks like you ground the resistive strips when you calculate the weighting potential. This should not be the case, there should not be any applied conditions on them.

Kind regards,

Djunes

I figured maybe the negative tail of the original signal might come from the ions. I plotted 50,000 ions starting from below the mesh and I got the following signal.


Am I to interpret that the negative signal on the readout strips comes from the ions moving above the mesh to the top of the detector?

So when the ions are moving from the hv strips to the anode the induced signal is positive, but when they’re moving above the mesh to the cathode the signal is negative?

Hi djjansse,

I was interpreting HSchindl’s comment as being that when calculating the weighting potential all electrodes are set to 0V other than the particular readout electrode (including the hv strips). Am I to assume from your comment that this is not the case.

So for example given my 10 readout electrode strips, for each one set the other 9 to 0V and keep the resistive strips and the cathode at their respective potentials of 600V and -400V? (i.e. only ground the readout electrodes?).

Dear Conner,

Heinrich is completely right. However, your strips are resistive, which changes the situation a bit. You should directly ground all metallic electrodes except the one you want to study. For resistive elements you ground the points where they are connected to HV. So in your case it will be on the edge of the detector. Since you are only interested in the prompt component of the signal, this grounding of the resistive strips on the edge will not impact the weighting potential map sufficiently far away from this region.

I would suggest redoing the weighting potentials where:

  • Put a unit potential on the strip you want to look at

  • Ground all other metallic electrodes

  • Ground the resistive strips on their edge, but you can just replace this by leaving them unconnected.

I hope this helps.

Kind regards,

Djunes

Hi Djunes,

Thankyou very much for the insight, I will try this out and come back with the results.

Thanks,

Connor

Hi Djunes,

I did what you suggested, recalculated all the weighting fields with the resistive HV strips held at 700V and each readout strip alternated between 1V and the rest at 0V. I didn’t ground the edge of the strips though (I assume you meant at the boundary of the detector, where they would connect). I simulated an avalanche towards the middle of the detector (detector is 0.5 cm wide) directly above the x3 strip, so I figured the effect of the edges would be insignificant, though I’m likely wrong in assuming this.

Something else I also noticed was that I was imported the potential plots using fm.SetWeightingField, so I added a line UseWeightingPotential(true) as you had suggested in another post.

I get the following two plots for the current and charge, they seem to be more appropriate, the negative signal as suggested in a reply above. However I now run into an issue in that this current and charge plots are the same for all readout strips. Is this an effect of having such a large potential on the resistive strips in comparison to the unit potential on the weighting strips?

Also not sure if it helps but I currently have the dielectric for the strips set at 17, and the integrated charge seems to be way to high.


Dear Conner,

Rereading my above response I realize that I could have explained it better. If you are only interested in the prompt signal, you should not put the resistive strips to 700V, rather you need to treat them as if they are perfect insulators. So I would remove the 700V condition form the resistive strips and try again.

Kind regards,

Djunes

Hi Djunes,

I figured that was the case and have been using the old weighting fields I calculated. Thankyou very much for your help throughout this thread, it’s been very insightful.

Thanks,

Connor