Fixed pinch scattering

build.gradle

@@ -8,7 +8,7 @@ mainClassName = "inr.numass.trapping.Trapping"
 group = 'inr.numass'
 version = 'dev'
 
-description = """trapping"""
+description = "Numass trapping simulation"
 
 sourceCompatibility = 1.8
 targetCompatibility = 1.8
@@ -18,9 +18,9 @@ tasks.withType(JavaCompile) {
 }
 
 repositories {
-
+    mavencentral()
-     maven { url "http://repo.maven.apache.org/maven2" }
 }
+
 dependencies {
     compile group: 'org.apache.commons', name: 'commons-math3', version:'3.6.1'
     testCompile group: 'junit', name: 'junit', version:'4.12'

docs/csource/readme.txt

@@ -0,0 +1 @@
+Original C sources provided by Sebastian Voecking and Ferenc Glueck

src/main/java/inr/numass/trapping/SimulationManager.java

@@ -31,26 +31,58 @@ public class SimulationManager {
         return this;
     }
 
+    /**
+     * Select output for accepted events
+     *
+     * @param output
+     * @return
+     */
     public SimulationManager withOutput(PrintStream output) {
         this.output = output;
         return this;
     }
 
+    /**
+     * Select output for statistics
+     *
+     * @param statisticOutput
+     * @return
+     */
     public SimulationManager withStatisticOutput(PrintStream statisticOutput) {
         this.statisticOutput = statisticOutput;
         return this;
     }
 
+    /**
+     * Set field map as function
+     *
+     * @param fieldMap
+     * @return
+     */
     public SimulationManager withFieldMap(UnivariateFunction fieldMap) {
         this.simulator.setFieldFunc(fieldMap);
         return this;
     }
 
+    /**
+     * Set field map from values
+     *
+     * @param z
+     * @param b
+     * @return
+     */
     public SimulationManager withFieldMap(double[] z, double[] b) {
         this.simulator.setFieldFunc(new LinearInterpolator().interpolate(z, b));
         return this;
     }
 
+    /**
+     * Set source density
+     * PENDING replace by source thickness?
+     *
+     * @param density
+     * @return
+     */
     public SimulationManager withDensity(double density) {
         this.simulator.setGasDensity(density);
         return this;
@@ -68,7 +100,7 @@ public class SimulationManager {
         System.out.printf("%nStarting sumulation with initial energy %g and %d electrons.%n%n", initialE, num);
         Stream.generate(() -> getRandomTheta()).limit(num).parallel()
                 .forEach((theta) -> {
-                    double initZ = generator.nextDouble() * Simulator.SOURCE_LENGTH;
+                    double initZ = (generator.nextDouble()-1) * Simulator.SOURCE_LENGTH;
                     Simulator.SimulationResult res = simulator.simulate(initialE, theta, initZ);
                     if (reportIf.test(res)) {
                         if (output != null) {
@@ -83,7 +115,7 @@ public class SimulationManager {
 
     private double getRandomTheta() {
         double x = generator.nextDouble();
-        // from 0 to 2 Pi
+        // from 0 to Pi
         return Math.acos(1 - 2 * x);
     }
 
@@ -106,6 +138,9 @@ public class SimulationManager {
     }
 
 
+    /**
+     * Statistic counter
+     */
     public static class Counter {
         int accepted = 0;
         int pass = 0;

src/main/java/inr/numass/trapping/Simulator.java

@@ -11,11 +11,10 @@ import org.apache.commons.math3.geometry.euclidean.threed.SphericalCoordinates;
 import org.apache.commons.math3.geometry.euclidean.threed.Vector3D;
 import org.apache.commons.math3.random.JDKRandomGenerator;
 import org.apache.commons.math3.random.RandomGenerator;
+import org.apache.commons.math3.util.DoubleArray;
 import org.apache.commons.math3.util.Pair;
 import org.apache.commons.math3.util.Precision;
 
-import java.util.function.Function;
-
 import static org.apache.commons.math3.util.FastMath.*;
 
 /**
@@ -24,7 +23,7 @@ import static org.apache.commons.math3.util.FastMath.*;
 public class Simulator {
 
     public static final double SOURCE_LENGTH = 3d;
-    private static final double DELTA_L = 0.1; //step for dZ calculation
+    private static final double DELTA_L = 0.1; //step for deltaZ calculation
 
     private RandomGenerator generator;
     private Scatter scatter;
@@ -138,24 +137,45 @@ public class Simulator {
     /**
      * calculate z coordinate change with known path length. Does not change position.
      *
-     * @param dl
+     * @param deltaL
-     * @return
+     * @return z shift and reflection counter
      */
-    private double dZ(State position, double dl) {
+    private Pair<Double, Integer> deltaZ(State position, double deltaL) {
         // if magnetic field not defined, consider it to be uniform and equal bSource
+        int direction = position.isForward() ? 1 : -1;
         if (magneticField == null) {
-            return dl / cos(position.theta);
+            double deltaZ = direction * deltaL * cos(position.theta);
+            int reflectionCounter = (int) (deltaZ / SOURCE_LENGTH);
+            double curZ = normalizeZ(position.z + deltaZ);
+            return new Pair<>(curZ - position.z, reflectionCounter);
         } else {
-            double dz = 0;
+            int reflect = 0;
+            double curZ = position.z;
             double curL = 0;
-            while (curL <= dl) {
-                double delta = min(dl - curL, DELTA_L);
-                double b = field(position.z + dz);
 
-                dz += delta / sqrt(1 - pow(sin(position.theta), 2) * b / bSource);
+
-                curL += DELTA_L;
+            double sin2 = sin(position.theta) * sin(position.theta);
+
+            while (curL <= deltaL) {
+                double delta = DELTA_L; //min(deltaL - curL, DELTA_L);
+                double b = field(curZ);
+
+                //TODO check this!
+                double root = 1 - sin2 * b / bSource;
+                // change direction in case of reflection. Loss of precision here?
+                if (root < 0) {
+                    direction = -direction;
+                    root = -root;
+                    reflect++;
                 }
-            return dz;
+
+                curZ += direction * delta * sqrt(root);
+
+                curZ = normalizeZ(curZ);
+
+                curL += delta;
+            }
+            return new Pair<>(curZ - position.z, reflect);
         }
     }
 
@@ -169,18 +189,23 @@ public class Simulator {
         if (magneticField == null) {
             return bSource;
         } else {
-            while (!(z > 0 && z < SOURCE_LENGTH)) {
-                // reflecting from back wall
-                if (z < 0) {
-                    z = -z;
-                } else {
-                    z -= SOURCE_LENGTH;
-                }
-            }
             return magneticField.value(z);
         }
     }
 
+    private double normalizeZ(double z) {
+        while ((abs(z) > SOURCE_LENGTH / 2)) {
+            if (z < 0) {
+                // reflecting from rear pinch
+                z += SOURCE_LENGTH / 2d;
+            } else {
+                // reflecting from forward transport magnet
+                z -= SOURCE_LENGTH / 2d;
+            }
+        }
+        return z;
+    }
+
     /**
      * Симулируем один пробег электрона от начального значения и до вылетания из
      * иточника или до того момента, как энергия становится меньше eLow.
@@ -188,17 +213,7 @@ public class Simulator {
     public SimulationResult simulate(double initEnergy, double initTheta, double initZ) {
         assert initEnergy > 0;
         assert initTheta > 0 && initTheta < Math.PI;
-        assert initZ >= 0 && initZ < SOURCE_LENGTH;
+        assert abs(initZ) <= SOURCE_LENGTH / 2d;
-
-//        if (initTheta < this.thetaPinch) {
-//            if (generator.nextBoolean()) {
-//                return new SimulationResult(EndState.PASS, initEnergy, initTheta, initTheta, 0);
-//            } else {
-//                return new SimulationResult(EndState.REJECTED, initEnergy, initTheta, initTheta, 0);
-//            }
-//        } else if (initTheta < this.thetaTransport) {
-//            return new SimulationResult(EndState.REJECTED, initEnergy, initTheta, initTheta, 0);
-//        }
 
         State pos = new State(initEnergy, initTheta, initZ);
         EndState endState = EndState.NONE;
@@ -208,15 +223,15 @@ public class Simulator {
         while (!stopflag) {
 
             double dl = freePath(pos.e); // path to next scattering
-            double dz = dZ(pos, dl); // z coordinate to next scattering
+            Pair<Double, Integer> dzCalc = deltaZ(pos, dl);
-            double expectedZ = pos.z + dz; // expected z position of next scattering
+            double dz = dzCalc.getFirst();// z coordinate to next scattering
+            int reflections = dzCalc.getSecond();
 
             //if no scattering on current source pass
-            if (expectedZ < 0 || expectedZ > SOURCE_LENGTH) {
+            if (reflections > 0) {
                 //accepted by spectrometer
                 if (pos.theta < thetaPinch) {
                     stopflag = true;
-                    //Учитываем тот факт, что электрон мог вылететь в правильный угол, но назад
                     if (pos.colNum == 0) {
                         //counting pass electrons
                         endState = EndState.PASS;
@@ -226,23 +241,22 @@ public class Simulator {
                 }
 
 
-                //through the rear magnetic trap
+                //through the rear magnetic pinch
                 if (pos.theta >= PI - thetaTransport) {
                     stopflag = true;
                     endState = EndState.REJECTED;
                 }
-
-                if (pos.e < eLow) {
-                    //Если энергия стала слишком маленькой
-                    stopflag = true;
-                    endState = EndState.LOWENERGY;
-                }
             }
             if (!stopflag) {
                 // perform scatter
                 propagate(pos, dl, dz);
                 pos.colNum++;
                 scatter(pos);
+                if (pos.e < eLow) {
+                    //Если энергия стала слишком маленькой
+                    stopflag = true;
+                    endState = EndState.LOWENERGY;
+                }
             }
 
         }
@@ -312,7 +326,7 @@ public class Simulator {
         int colNum = 0;
 
         /**
-         * current z;
+         * current z. Zero is the center of the source
          */
         double z;
 
@@ -337,13 +351,13 @@ public class Simulator {
          */
         double addZ(double dZ) {
             this.z += dZ;
-            while (!(this.z > 0 && this.z < SOURCE_LENGTH)) {
+            while (abs(this.z) > SOURCE_LENGTH / 2d) {
                 // reflecting from back wall
                 if (z < 0) {
-                    z = -z;
+                    z += SOURCE_LENGTH / 2d;
                     flip();
                 } else {
-                    z -= SOURCE_LENGTH;
+                    z -= SOURCE_LENGTH / 2d;
                     flip();
                 }
             }
@@ -375,7 +389,14 @@ public class Simulator {
             if (magneticField == null) {
                 return theta;
             } else {
-                return asin(sin(theta) * sqrt(field() / bSource));
+                double newTheta = asin(min(abs(sin(theta)) * sqrt(field() / bSource), 1));
+                if (theta > PI / 2) {
+                    newTheta = PI - newTheta;
+                }
+                if (Double.isNaN(newTheta)) {
+                    throw new Error();
+                }
+                return newTheta;
             }
         }
 
@@ -406,7 +427,7 @@ public class Simulator {
             if (newtheta < 0) {
                 newtheta = -newtheta;
             }
-            if (newtheta > Math.PI && newtheta <= Math.PI * 3 / 2) {
+            if (newtheta > Math.PI) {
                 newtheta = 2 * Math.PI - newtheta;
             }
 
@@ -415,7 +436,15 @@ public class Simulator {
                 theta = newtheta;
             } else {
                 theta = asin(sin(newtheta) * sqrt(bSource / field()));
+                if (newtheta > PI / 2) {
+                    theta = PI - theta;
                 }
+            }
+
+            if (Double.isNaN(theta)) {
+                throw new Error();
+            }
+
             return theta;
         }
 

src/main/java/inr/numass/trapping/Trapping.java

@@ -26,7 +26,8 @@ public class Trapping {
         new SimulationManager()
                 .withParameters(0.6, 3.7, 4.84, 18000d, 4000)
 //                .withFieldMap(z, b)
-                .simulateAll((int) 1e4);
+//                .withDensity(5e20)
+                .simulateAll((int) 1e5);
         Instant finishTime = Instant.now();
         System.out.printf("%nFinished at %s%n", finishTime.toString());
         System.out.printf("Calculation took %s%n", Duration.between(startTime,finishTime).toString());

src/test/java/hep/dataforge/trapping/AppTest.java

@@ -1,38 +0,0 @@
-package hep.dataforge.trapping;
-
-import junit.framework.Test;
-import junit.framework.TestCase;
-import junit.framework.TestSuite;
-
-/**
- * Unit test for simple App.
- */
-public class AppTest 
-    extends TestCase
-{
-    /**
-     * Create the test case
-     *
-     * @param testName name of the test case
-     */
-    public AppTest( String testName )
-    {
-        super( testName );
-    }
-
-    /**
-     * @return the suite of tests being tested
-     */
-    public static Test suite()
-    {
-        return new TestSuite( AppTest.class );
-    }
-
-    /**
-     * Rigourous Test :-)
-     */
-    public void testApp()
-    {
-        assertTrue( true );
-    }
-}