NeGEMSIM v1.0

			Project Details Latest version 1.0 Nov-2012 News 29-Nov-2012 NeGEMSIM v1.0 available in svn at CERN
Triple GEM Detector: Exploded view	Photon Interaction Probability in Ar/CO2 (3 mm)	Aluminium Layer Test Volume

1. Description

NeGEMSIM is a simulation developed in Geant4 to estimate the sentivivity and other properties of several kinds of particle gas detectors using a neutron or photon gun with energies according to fluxes in the CMS endcap muon system (see CMS Muon TDR - Radiation Environment). NeGEMSIM is designed to generate root output files compatible with GARFIELD++.

NeGEMSIM is based in GEMSIM done by Remi ETE (Jul-2012), Its source code is available in the svn at CERN

1.1. about physics

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1.2. about detector geometry

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1.3. about primary action

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1.4. about analysis

2. Compile and Run

NeGEMSIM source code is available in the svn at CERN.

$ cd YOUR_NeGEMSIM_PATH/NeGEMSIM
$ svn co https://svn.cern.ch/reps/asevilla/NeGEMSIM

After download is important modify ./setup.sh and include YOUR_NeGEMSIM_PATH and YOUR_GEANT4_PATH.

echo "Setting new G4WORKDIR"
export G4WORKDIR=YOUR_NeGEMSIM_PATH/NeGEMSIM
echo "Setting new PATH"
export PATH=$G4WORKDIR/bin/Linux-g++/:$PATH
echo "Loading G4 source files"
source YOUR_GEANT4_PATH/geant4.9.5-install/share/Geant4-9.5.1/geant4make/geant4make.sh

source the NeGEMSIM setup file.

$ source setup.sh

Compile and run using visualization macro file included in ./mac.

$ make
$ NeGEMSIM ./mac/vis.mac

2.1. about execution details

NeGEMSIM has some predefined parameters, e.g. Geometry ( "DetectorTripleGEM"), Physics List ( "QGSP_BIC"), etc. however accepts 2 parameters when is executed, a steering file and a macro file provided by user.

An example of these files are included in folders ./steer and ./mac respectively. WARNING! user must add new commands in the right file and line, due to NeGEMSIM executes steering and macro files in different G4States (see Kernel 1)

Standard useful Commands

- to include in mac file

• Visualization.
  NeGEMSIM has been run using OpenInventor and OpenGL visualization (see G4 Beginners)

• Primary Action
  
  /gun/particle gamma
  With this command, the user chooses which kind of particle is launched, WARNING! The particule selected, its interaction processes and its possible secondaries must be included in the set physics list.
  
  /gun/energy 1e+2 MeV
  With this command, the user sets particles energy INFO! is recommended work in MeV because NeGEMSIM saves by default all energy output data in this unit.

• Run
  
  /run/beamOn 10000
  With this command, the user runs NeGEMSIM and set how many events (primary particles) per run will be launched.

Triple GEM Detector: Cutoff view

Additional Available Commands

- to include in steer file

• Analysis Factory
  
  /NeGEMSIM/analysis/setRootFileName NeGEMSIM_1e+2MeV.root
  This command is very important if the user wants run NeGEMSIM with different parameters in several machines to distribute efforts, e.g. using lxplus (see Running in lxplus) .

• Physics List
  
  /NeGEMSIM/physics/setPhysicsList QGSP_BIC
  Any predefined Geant4 physics list is available, moreover NeGEMSIM includes a modifiable local physics list (see about physics), It is important if the user wants filter processes or change models.

• Detector Geometry
  
  /NeGEMSIM/detector/setDetectorGeometry DetectorTripleGEM
  With this command, the user chooses between different geometries of particle gas detectors or test volumes, please, check the names and geometries available included in NeGEMSIM (see about detector geometry)

• Primary Action
  
  /NeGEMSIM/gun/setParticleMomentumTheta 0 deg
  With this command, the user sets the beam incident angle and automatically NeGEMSIM changes the gun position in order to always launch particles at point (0,0,0).

2.2. Running in lxplus

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3. Results

In this section are available results about the neutron or photon sensitivity and some ionization primaries properties (see about analysis) WARNING! Each estimation depends of the selected geometry and physics list, that may not be suitable or be under construction, for this reason is important review this twiki continuosly, later these results will be validated with test beam measurements (see next steps).

3.1. NeGEMSIM Physics List Cross Check

3.1.1. Photon cross section using "QGSP_BIC" Geant4 physics list

Using the included geometry "DetectorAluminiumLayer"

3.2. DetectorTripleGEM _1 Studies

DetectorTripleGEM_1 is a geometry

3.2.1. DetectorTripleGEM _1 sensitivity to photons using "QGSP_BIC" Geant4 physics list

Downloadable files

• NeGEMSIM Output: gamma / QGSP_BIC / DetectorTripleGEM_1.

Plot 1.

For energies below 1e-2 MeV, All photons were absorbed by photoelectric effect in the layer boxBase (see DetectorTripleGEM _1 details) accordingly electrons were generated, however, its energy wasn't enough to arrive at gasGap1.

Plot 2.

For energies between 1e-2 and 1e-1 MeV the interaction probability Photon-Aluminium by photoelectric effect decrease, some photons arrived at gasGap1, and a few interacted with the gas mixture (see Plot 2) generating pairs electron-ion.

For energies above 1e-1 MeV the interaction probability Photon-GEM gas mixture is lower than 1e-4 (see Plot 2.) therefore, not created electrons in gasGap1 directly by photon interaction, however, some electrons and positrons generated in the previuos layers (boxBase, drifCathodeFoil) arrived at gasGap1 and produced signal.

Changing the incidence angle

Due to the GE1/1 stations will fill several places in the CMS endcap muon system, will be exposed to radiation from any position, therefore, is important know the sensitivity variation with respect to the beam indicence angle.

In this section

3.2.2. DetectorTripleGEM _1 sensitivity to neutrons using "QGSP_BIC_HP" Geant4 physics list

Plot 3.

-- CamiloSevilla - 29-Nov-2012