diff -N detectorenvelope.gdml
--- /dev/null	1 Jan 1970 00:00:00 -0000
+++ detectorenvelope.gdml	3 Apr 2013 20:51:32 -0000	1.1
@@ -0,0 +1,45 @@

+<?xml version="1.0" encoding="UTF-8" ?>
+<gdml xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="http://service-spi.web.cern.ch/service-spi/app/releases/GDML/schema/gdml.xsd">
+ <define>
+  <constant name="HALFPI" value="pi/2."/>
+  <constant name="PI" value="1.*pi"/>
+  <constant name="TWOPI" value="2.*pi"/>
+</define>
+
+    <materials>
+        <material Z="1.0" name="AIR">
+            <D value="1e-24"/>
+            <atom value="1.00794"/>
+        </material>
+    </materials>
+
+    <solids>
+        <box name="WorldBox" lunit="m" x="20" y="20" z="50"/>
+	<polycone aunit="degree" name="Detector" deltaphi="360.0" startphi="0.0">
+	  <zplane lunit="cm" z="-600." rmin="74.0" rmax="550.0"/>
+	  <zplane lunit="cm" z="-119.136" rmin="29.5" rmax="550."/>
+	  <zplane lunit="cm" z="-20.45" rmin="3.2" rmax="550."/>
+	  <zplane lunit="cm" z="20.45" rmin="3.2" rmax="550."/>
+	  <zplane lunit="cm" z="119.136" rmin="29.5" rmax="550."/>
+	  <zplane lunit="cm" z="600." rmin="74." rmax="550."/>
+	</polycone>
+    </solids>
+
+    <structure>
+        <volume name="DetectorVolume">
+            <materialref ref="AIR"/>
+            <solidref ref="Detector"/>
+        </volume>
+        <volume name="TOP">
+            <materialref ref="AIR"/>
+            <solidref ref="WorldBox"/>
+            <physvol name="pDetectorVolume">
+                <volumeref ref="DetectorVolume"/>
+                <position name="Detectorpos" x="0" y="0" z="0"/>
+            </physvol>
+        </volume>
+    </structure>
+    <setup version="1.0" name="Default">
+        <world ref="TOP"/>
+    </setup>
+</gdml>