diff --git a/build.gradle b/build.gradle
index 605d6ad..a01dfec 100644
--- a/build.gradle
+++ b/build.gradle
@@ -47,9 +47,15 @@ model {
         scatter(NativeLibrarySpec)
     }
     toolChains {
+        visualCpp(VisualCpp) {
+            // Specify the installDir if Visual Studio cannot be located
+            // installDir "C:/Apps/Microsoft Visual Studio 10.0"
+             installDir "C:\\Program Files (x86)\\Microsoft Visual Studio 12.0"
+        }
         gcc(Gcc) {
             // Uncomment to use a GCC install that is not in the PATH
             // path "/usr/bin/gcc"
         }
+
     }
 }
diff --git a/src/main/java/inr/numass/trapping/SimulationManager.java b/src/main/java/inr/numass/trapping/SimulationManager.java
index 207121f..bc04b3b 100644
--- a/src/main/java/inr/numass/trapping/SimulationManager.java
+++ b/src/main/java/inr/numass/trapping/SimulationManager.java
@@ -131,13 +131,16 @@ public class SimulationManager {
     }
 
     private void printStatistics(Counter counter) {
+        output.println();
+        output.println("***RESULT***");
         output.printf("The total number of events is %d.%n%n", counter.count);
-
         output.printf("The spectrometer acceptance angle is %g.%n", simulator.thetaPinch * 180 / Math.PI);
         output.printf("The transport reflection angle is %g.%n", simulator.thetaTransport * 180 / Math.PI);
         output.printf("The starting energy is %g.%n", initialE);
-        output.printf("The lower energy boundary is %g.%n%n", simulator.eLow);
+        output.printf("The lower energy boundary is %g.%n", simulator.eLow);
+        output.printf("The source density is %g.%n", simulator.gasDensity);
 
+        output.println();
         output.printf("The total number of ACCEPTED events is %d.%n", counter.accepted);
         output.printf("The total number of PASS events is %d.%n", counter.pass);
         output.printf("The total number of REJECTED events is %d.%n", counter.rejected);
diff --git a/src/main/java/inr/numass/trapping/Simulator.java b/src/main/java/inr/numass/trapping/Simulator.java
index ad8d987..b90ead9 100644
--- a/src/main/java/inr/numass/trapping/Simulator.java
+++ b/src/main/java/inr/numass/trapping/Simulator.java
@@ -29,7 +29,7 @@ public class Simulator {
     double eLow = 14000d;//default value
     double thetaTransport = 24.107064 / 180 * Math.PI;// default value
     double thetaPinch = 19.481097 / 180 * Math.PI;// default value
-    double gasDensity = 5e18;// m^-3
+    double gasDensity = 5e20;// m^-3
     double bSource = 0.6;
     private UnivariateFunction magneticField;
 
@@ -147,7 +147,7 @@ public class Simulator {
         // if magnetic field not defined, consider it to be uniform and equal bSource
         if (magneticField == null) {
             double deltaZ = deltaL * cos(pos.theta); // direction already included in cos(theta)
-            double z0 = pos.z;
+//            double z0 = pos.z;
             pos.addZ(deltaZ);
             pos.l += deltaL;
 
@@ -375,12 +375,11 @@ public class Simulator {
         double addZ(double dZ) {
             this.z += dZ;
             while (abs(this.z) > SOURCE_LENGTH / 2d && !isFinished()) {
-                checkEndState();
-                if (!isFinished()) {
-                    flip();
-                }
                 // reflecting from back wall
                 if (z < 0) {
+                    if (theta >= PI - thetaTransport) {
+                        setEndState(EndState.REJECTED);
+                    }
                     if (isFinished()) {
                         z = -SOURCE_LENGTH / 2d;
                     } else {
@@ -388,6 +387,14 @@ public class Simulator {
                         z = -SOURCE_LENGTH - z;
                     }
                 } else {
+                    if (theta < thetaPinch) {
+                        if (colNum == 0) {
+                            //counting pass electrons
+                            setEndState(EndState.PASS);
+                        } else {
+                            setEndState(EndState.ACCEPTED);
+                        }
+                    }
                     if (isFinished()) {
                         z = SOURCE_LENGTH / 2d;
                     } else {
@@ -395,36 +402,42 @@ public class Simulator {
                         z = SOURCE_LENGTH - z;
                     }
                 }
+                if (!isFinished()) {
+                    flip();
+                }
             }
             return z;
         }
 
-        /**
-         * Check if this position is an end state and apply it if necessary. Does not check z position.
-         *
-         * @return
-         */
-        private void checkEndState() {
-            //accepted by spectrometer
-            if (theta < thetaPinch) {
-                if (colNum == 0) {
-                    //counting pass electrons
-                    setEndState(EndState.PASS);
-                } else {
-                    setEndState(EndState.ACCEPTED);
-                }
-            }
-
-            //through the rear magnetic pinch
-            if (theta >= PI - thetaTransport) {
-                setEndState(EndState.REJECTED);
-            }
-        }
+//        /**
+//         * Check if this position is an end state and apply it if necessary. Does not check z position.
+//         *
+//         * @return
+//         */
+//        private void checkEndState() {
+//            //accepted by spectrometer
+//            if (theta < thetaPinch) {
+//                if (colNum == 0) {
+//                    //counting pass electrons
+//                    setEndState(EndState.PASS);
+//                } else {
+//                    setEndState(EndState.ACCEPTED);
+//                }
+//            }
+//
+//            //through the rear magnetic pinch
+//            if (theta >= PI - thetaTransport) {
+//                setEndState(EndState.REJECTED);
+//            }
+//        }
 
         /**
          * Reverse electron direction
          */
         void flip() {
+            if(theta<0||theta>PI){
+                throw new Error();
+            }
             theta = PI - theta;
         }
 
diff --git a/src/main/java/inr/numass/trapping/Trapping.java b/src/main/java/inr/numass/trapping/Trapping.java
index dd357bf..235eefa 100644
--- a/src/main/java/inr/numass/trapping/Trapping.java
+++ b/src/main/java/inr/numass/trapping/Trapping.java
@@ -15,10 +15,10 @@ public class Trapping {
         Instant startTime = Instant.now();
         System.out.printf("Starting at %s%n%n", startTime.toString());
         new SimulationManager()
-                .withParameters(0.6, 3.7, 4.84, 14000d, 4000)
-                .withOutputFile("D:\\Work\\Numass\\trapping\\trap 14, pinch 100A.out")
+                .withParameters(0.6, 3.7, 4.84, 18000d, 4000)
+                .withOutputFile("D:\\Work\\Numass\\trapping\\test1.out")
 //                .withFieldMap(z, b)
-//                .withDensity(5e20)
+                .withDensity(1e19)
                 .simulateAll((int) 1e6);
         Instant finishTime = Instant.now();
         System.out.printf("%nFinished at %s%n", finishTime.toString());
diff --git a/src/scatter/c/scatter.c b/src/scatter/c/scatter.c
index edc65fd..20b740a 100644
--- a/src/scatter/c/scatter.c
+++ b/src/scatter/c/scatter.c
@@ -11,6 +11,7 @@
  */
 
 //#include "scatter.h"
+#define _USE_MATH_DEFINES // for C
 
 #include <math.h>
 #include <stdio.h>