Electric field simulation

Geometry, Fields and Transportation
1

Dear Experts

I have successfully created the proportional counter of dimension 6m0.1m0.1m, it also has a tungsten wire which is kept at 3000v potential difference. I have to figure out how should i implement an Electric field generated from the tungsten wire which works as an anode.

Thanks

#include “construction.hh”
#include “G4Box.hh”
#include “G4LogicalVolume.hh”
#include “G4NistManager.hh”
#include “G4PVPlacement.hh”
#include “G4SystemOfUnits.hh”
#include “G4VisAttributes.hh”
#include “G4Tubs.hh”
#include “G4SDManager.hh”

MyDetectorConstruction::MyDetectorConstruction()
: G4VUserDetectorConstruction(), LogicDetector(nullptr), LogicAnode(nullptr), fElectricFieldSetup(nullptr)
{
fMessenger = new G4GenericMessenger(this, “/Detector/”, “Detector construction”);
fMessenger->DeclareProperty(“nCols”, nCols, “Number of columns”);
fMessenger->DeclareProperty(“nRows”, nRows, “Number of rows”);

nCols = 80;
nRows = 80;

DefineMaterials();

}

MyDetectorConstruction::~MyDetectorConstruction() {
delete fElectricFieldSetup;
}

void MyDetectorConstruction::DefineMaterials()
{
G4NistManager* nist = G4NistManager::Instance();
air = nist->FindOrBuildMaterial(“G4_AIR”);
tungsten = nist->FindOrBuildMaterial(“G4_W”);

argon = nist->FindOrBuildMaterial("G4_Ar");
methane = nist->FindOrBuildMaterial("G4_METHANE");

P10 = new G4Material("P10", 1.66 * mg/cm3, 2, kStateGas, 298.0 * kelvin, 1.0 * atmosphere);
P10->AddMaterial(argon, 90 * perCent);
P10->AddMaterial(methane, 10 * perCent);

mildSteel = nist->FindOrBuildMaterial("G4_STAINLESS-STEEL");

}

G4VPhysicalVolume* MyDetectorConstruction::Construct()
{
// Define dimensions
G4double world_sizeX = 8.0 * m;
G4double world_sizeY = 2.5 * m;
G4double world_sizeZ = 2.5 * m;
G4double detector_sizeX = 6.0 * m;
G4double detector_sizeY = 0.1 * m;
G4double detector_sizeZ = 0.1 * m;
G4double anode_radius = 100 * um;
G4double anode_length = detector_sizeX;

// Create world volume
solidWorld = new G4Box("World", world_sizeX / 2, world_sizeY / 2, world_sizeZ / 2);
logicWorld = new G4LogicalVolume(solidWorld, air, "World");
physWorld = new G4PVPlacement(0, G4ThreeVector(), logicWorld, "World", 0, false, 0);

// Create primary detector volume (cuboidal)
solidCounter = new G4Box("Counter", detector_sizeX / 2, detector_sizeY / 2, detector_sizeZ / 2);
logicCounter = new G4LogicalVolume(solidCounter, P10, "Counter");
new G4PVPlacement(0, G4ThreeVector(), logicCounter, "Counter", logicWorld, false, 0);

// Set blue color for the detector
G4VisAttributes* detectorVisAttr = new G4VisAttributes(G4Colour(0.0, 0.0, 1.0)); // Blue color
detectorVisAttr->SetVisibility(true);
logicCounter->SetVisAttributes(detectorVisAttr);

// Create mild steel PRC body
solidCounter = new G4Box("CounterBody", detector_sizeX / 2, detector_sizeY / 2, detector_sizeZ / 2);
G4LogicalVolume* logicCounterBody = new G4LogicalVolume(solidCounter, mildSteel, "CounterBody");
new G4PVPlacement(0, G4ThreeVector(), logicCounterBody, "CounterBody", logicWorld, false, 0);

// Set grey color for the PRC body
G4VisAttributes* counterBodyVisAttr = new G4VisAttributes(G4Colour(0.5, 0.5, 0.5)); // Grey color
counterBodyVisAttr->SetVisibility(true);
logicCounterBody->SetVisAttributes(counterBodyVisAttr);

// Place the gas volume inside the PRC body
new G4PVPlacement(0, G4ThreeVector(), logicCounter, "Counter", logicCounterBody, false, 0);

// Create tungsten anode (cylindrical) parallel to the detector
solidAnode = new G4Tubs("Anode", 0.0, anode_radius, anode_length / 2, 0.0, 360.0 * deg);
LogicAnode = new G4LogicalVolume(solidAnode, tungsten, "Anode");

// Place the anode at the center of the detector volume
G4ThreeVector anodePosition(0, 0, 0);
G4RotationMatrix *rotationMatrix = new G4RotationMatrix();
rotationMatrix->rotateY(90.0 * deg); // Rotate the anode to align with the X-axis
new G4PVPlacement(rotationMatrix, anodePosition, LogicAnode, "Anode", logicCounter, false, 0);

// Set red color for the anode to see the difference
G4VisAttributes *anodeVisAttr = new G4VisAttributes(G4Colour(1.0, 0.0, 0.0));
anodeVisAttr->SetVisibility(true);
LogicAnode->SetVisAttributes(anodeVisAttr);

fScoringVolume = logicCounter;



return physWorld;

}

void MyDetectorConstruction::ConstructSDandField() {
// Create a sensitive detector and register it
G4String detectorName = “Counter”;
MySensitiveDetector* aDetector = new MySensitiveDetector(detectorName);
G4SDManager::GetSDMpointer()->AddNewDetector(aDetector);

// Assign the sensitive detector to the logical volume
SetSensitiveDetector(logicCounter, aDetector);

}
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_Geant4 Version:_11.2.1
_Operating System:_Ubuntu 22.04.4 LTS

2

Geant4 doesn’t calculate electric fields. You can use COMSOL to construct a finite-element model for your electric field, and write your own code to import that into Geant4.

You could also use Garfield to simulate your device response, rather than Geant4. Garfield can model the electron drift and avalanche processes, much better than Geant4 does.

1 Like
3

Thanks for your reply mr Michael
I am trying to implement the finite element method, but I don’t have access to COMSOL so I am trying ELMER with its connected libraries. Are there any examples where you can point me so that I can get a reference?
Also in the code provided above, I have tried to implement Garfield++, can you suggest me a method to do that correctly.

Thanks

4

Hi

I am facing the same problematic to simulate a Free Air Chamber, that is using Elmer to simulate the Electromagnetic Fiel of the chamber and Gerfield to process the migration…So since june 2024 i will apreciate to have your feedback on such a simulation case