private void visualizeKleinNishina(double energyJoule) {
int gridWidth = 600;
int gridHeight = 500;
double maxAngle = 360;
Grid2D grid = new Grid2D(gridWidth, gridHeight);
FloatProcessor fp = new FloatProcessor(grid.getWidth(), grid.getHeight());
fp.setPixels(grid.getBuffer());
// find max value
double max = 0;
for (int i = 0; i < maxAngle; ++i) {
double value = XRayTracerSampling.comptonAngleProbability(energyJoule, Math.toRadians(i));
if (value > max) {
max = value;
}
}
fp.drawLine((int) 0, grid.getHeight() / 2, grid.getWidth(), grid.getHeight() / 2);
fp.drawLine(grid.getWidth() / 2, 0, grid.getWidth() / 2, grid.getHeight());
fp.drawOval((grid.getWidth() - grid.getHeight()) / 2, 0, grid.getHeight(), grid.getHeight());
double lastX = 0;
double lastY = 0;
// draw angle distribution
for (int i = 0; i < maxAngle; ++i) {
double value = XRayTracerSampling.comptonAngleProbability(energyJoule, Math.toRadians(i));
SimpleMatrix m = Rotations.createBasicZRotationMatrix(Math.toRadians(i));
SimpleVector v = new SimpleVector(((value / max) * ((double) grid.getHeight() / 2.d)), 0, 0);
SimpleVector r = SimpleOperators.multiply(m, v);
double x = grid.getWidth() / 2 + r.getElement(0);
double y = grid.getHeight() / 2 + r.getElement(1);
if (i > 0) fp.drawLine((int) lastX, (int) lastY, (int) x, (int) y);
lastX = x;
lastY = y;
}
grid.show(
"Normalized Klein-Nishina cross-section as a function of scatter angle ("
+ energyJoule / eV
+ "eV)");
grid = new Grid2D(gridWidth, gridHeight);
fp = new FloatProcessor(grid.getWidth(), grid.getHeight());
fp.setPixels(grid.getBuffer());
// draw histogram with rejection sampling of the klein-nishina
// distribution
int[] angles = new int[grid.getWidth()];
for (int i = 0; i < numSamples; ++i) {
double angle = Math.toDegrees(sampler.getComptonAngleTheta(energyJoule));
int pos = (int) (angle * grid.getWidth() / 360.d);
angles[pos] += 1;
}
double max2 = 0;
for (int i = 0; i < angles.length; ++i) {
if (angles[i] > max2) {
max2 = angles[i];
}
}
for (int i = 0; i < angles.length; ++i) {
double x = i;
double y = ((angles[i]) * (grid.getHeight() / (max2)));
fp.drawLine((int) x, (int) grid.getHeight(), (int) x, grid.getHeight() - (int) y);
}
// draw klein-nishina probability function
lastX = 0;
lastY = 0;
for (int i = 0; i < maxAngle; ++i) {
double value = XRayTracerSampling.comptonAngleProbability(energyJoule, Math.toRadians(i));
double x = (i * (grid.getWidth() / 360.f));
double y = grid.getHeight() - ((value) * (grid.getHeight() / (max)));
fp.drawLine((int) lastX, (int) lastY, (int) x, (int) y);
lastX = x;
lastY = y;
}
grid.show(
"Energy: " + energyJoule / eV + "eV; x-axis: angle[0-360]; y-axis: probability[0-max]");
}
