Lead Shield Cone
We need to edit the EXn02DetectorConstruction file to allow for a target that is a lead cone to simulate the Moller Shield. The header file for an elliptical Cone gives the parameters need to call with.
// $Id: G4EllipticalCone.hh 67011 2013-01-29 16:17:41Z gcosmo $ // // // -------------------------------------------------------------------- // GEANT 4 class header file // // G4EllipticalCone // // Class description: // // G4EllipticalCone is a full cone with elliptical base which can be cut in Z. // // Member Data: // // xSemiAxis semi-axis, x, without dimentions // ySemiAxis semi-axis, y, without dimentions // zheight height, z // zTopCut upper cut plane level, z // // The height in Z corresponds to where the elliptical cone hits the // Z-axis if it had no Z cut. Also the cone is centered at zero having a // base at zTopCut and another at -zTopCut. The semi-major axes at the Z=0 // plane are given by xSemiAxis*zheight and ySemiAxis*zheight so that the // curved surface of our cone satisfies the equation: // // *************************************************************************** // * * // * (x/xSemiAxis)^2 + (y/ySemiAxis)^2 = (zheight - z)^2 * // * * // *************************************************************************** // // In case you want to construct G4EllipticalCone from : // 1. halflength in Z = zTopCut // 2. Dx and Dy = halflength of ellipse axis at z = -zTopCut // 3. dx and dy = halflength of ellipse axis at z = zTopCut // ! Attention : dx/dy=Dx/Dy // // You need to find xSemiAxis,ySemiAxis and zheight: // // xSemiAxis = (Dx-dx)/(2*zTopCut) // ySemiAxis = (Dy-dy)/(2*zTopCut) // zheight = (Dx+dx)/(2*xSemiAxis)
The geometry looks like
Solving the variables:
1. halflength in Z = zTopCut
The cone shape starts 380 cm from the vertex point of (0,0,0). It extends 1325.9 beyond the starting position. This gives the z(max) as z = 1705.9 cm. Since this cone is centered at the vertex with zTopCut positive and negative placed an equal distance from the vertex, 1325.9/2=662.95 cm
2. Dx and Dy = halflength of ellipse axis at z = -zTopCut
The length of the x and y components at the smaller end of the cone are found from the diameter at this position. Assuming a circle for the cross-cut, then x=y=0.5 dia= 43 cm /2 = 21.5 cm
3. dx and dy = halflength of ellipse axis at z = zTopCut
Using geometry, for a right triangle with it's apex at the vertex and a height of 1705.9, with an interior angle of 5 degrees.
Solving for the variable to pass to the function:
The height in z is defined at the the point where the cone vertex crosses the z=0 plane in x&y. From the drawing, the vertex is originally placed at 0,0,0. Since the GEANT4 cone is centered at a new vertex with the circular cross sections of the cone at +/- 662.95, and the distance from the first smaller cross section is 380, this gives the intersection at -1042.95 cm with respect to the new vertex.