Problems about ViewField

Garfield++
1

I use ComponentConstant to create a uniform electric field along the z direction and us ViewField for visualization to ensure that I have established the uniform electric field.But the view result is blank.How can I visualize the uniform electric field?
This is my code.

int main(int argc, char *argv[])
{
    TApplication app("app", &argc, argv);
    // Set gas
    MediumMagboltz gas;
    gas.SetTemperature(293.15);
    gas.SetPressure(760.);
    gas.SetComposition("Ar", 0.94, "CO2", 0.03, "H2O", 0.03, "O2", 20.9, "N2", 78.1);
    gas.Initialise(true); // prepares the table of microscopic scattering rates
    gas.LoadGasFile("gas_293_1atm_10-100000nE20.gas");
    const string ionpath = std::getenv("GARFIELD_INSTALL");
    gas.LoadIonMobility(ionpath + "/share/Garfield/Data/IonMobility_Ar+_Ar.txt");

    ComponentConstant cmp;
    constexpr double xlength = 10.; // cm
    constexpr double ylength = 10.;
    constexpr double zlength = 10.;
    cmp.SetArea(0., 0., 0., xlength, ylength, zlength);
    cmp.SetMedium(&gas);
    cmp.SetElectricField(0., 0., 1000.);

    ViewField fieldView;
    constexpr bool plotField = true;
    if (plotField)
    {
        fieldView.SetComponent(&cmp);
        fieldView.SetPlane(0, -1, 0, 0, 0, 0); //viewing plane (xz plane).
        fieldView.SetArea(0., 0, 0, xlength, ylength, zlength); //plot limits
        TCanvas *cf = new TCanvas("cf", "", 600, 600);
        cf->SetLeftMargin(0.16);
        fieldView.SetCanvas(cf);
        fieldView.PlotContour("e");
    }
    app.Run(true);
}

This is the result.

image
image594×633 14.2 KB

Looking forward to your reply, thank you very much！

2

The plot looks correct to me, it shows a constant value of 1000 V/cm. For a uniform field, a contour plot of the field is not very instructive…

3
  1. Emm, you mean the result is right? But I see nothing
  2. How to show the uniform electric field is instructive ?
  3. in Examples I see fieldView.PlotFieldLines ( )
std::vector<double> xf;
std::vector<double> yf;
std::vector<double> zf;
fieldView.EqualFluxIntervals(xmin, 0, 0.99 * zmax, xmax, 0, 0.99 * zmax, xf, yf, zf, 20);
fieldView.PlotFieldLines(xf, yf, zf, true, false);

if I want to PlotFieldLines to show the uniform field, how should I modify the parameters of EqualFluxIntervals()? I don 't quite understand how to use EqualFluxIntervals.

4

What do you mean? The plot shows a constant value. What did you expect to see from a contour plot of a uniform field?

If you want to see a gradient, you could plot the contours of the potential instead of the electric field.

EqualFluxIntervals is a helper function for choosing the starting points for a field line plot. You specify the starting point, end point, and the number of points, and the function will return you the coordinates of a set of points with a spacing corresponding to the density of electric field lines. You can then pass the coordinates of these points to the function PlotFieldLines to be used as starting points.

5

Oh,I got it ! I mistakenly thought I was drawing the potential.Thank you for your patient explanation

6

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