Tracking Calorimeter Simulation for Tesla

last update: July 18th 2000

We've been developping Geant4 applications for simulation of a Tracking Calorimeter. A first application using only tubs have been exploited since january 99, the "lineaire" one. Since december 1999 we started from scratch a new application, "Mokka", to simulate a Tracking Calorimeter for the Tesla projet.

• A few words about the first Lineaire program
• Work in progress:
  • The Mokka project
  • Geometry Database
  • Output File data format
  • The automatic Fortran code generation by Mokka

We started it with the geometrical information from the NLC project with a very simple approach: using only tubes except for the masks, where we placed conical tubes.

This geometry evolved along 1999 and in the last lineaire release we are running with forty Tungsten and Silicon layers in the Ecal barrel,  as shown in this slide: thirty layers with 1.4 mm and ten layers with 4.3 mm as the Tungsten thickness.

The Hcal was made in the same way but one  would like to play with iron layers mixed with Tungsten ones. So for a set of layers we  have both, iron and Tungsten. The sensitive detector part or the Hcal is all the same as for the Ecal, Si layers placed inside two PCB plates.

But always we placed only tubes. And the cells where we collect hits are always projective in Theta and Phi. Also, all the geometrical data and simulation parameters are read from simple ASCII files at run time. These limitations let us to start a new software development, the Mokka project.

•  to simulate a more realistic Ecal and Hcal geometry;
•  to define an outside geometry database to avoid hard coded  geometry parameters in the C++ code;
•  and a new goal: to be backward compatible with BRAHMS.

 About the software design, Mokka is a C++ application able to access the geometry database on the fly via a MySQL C++ wrapper and, using the Geant4 framework, build the detector geometry and simulate events in this geometry. The goal of course is to have the Ecal and Hcal hits stored in an output file.

 The run control and conditions are setup via some run control commands, it can be done via an interactive command dialogue or via a macro file execution. As one of the Geant4 facilities, it's very easy to read Pythia event files to be tracked inside the detector.

 Mokka is now able to generate Geant3 Fortran code for BRAHMS, the so called "backward facility".
 

• Mokka pictures Ecal galerie
• Mokka pictures Hcal galerie (missing the Hcal endcaps!)
• Mokka pictures Ecal & Hcal galerie (missing the Hcal endcaps!)
• Mokka first event: pictures and data for a 10 GeV electron crossing the Ecal

• The Database Entity-Relationship Model for the Ecal and the Hcal
• The  geometry parameters sheets for the Ecal and the Hcal
• The Database MySQL Structure for the Ecal and the Hcal
• The actual  Ecal01 and Hcal01 database values:calorimeters
• The previous Ecal00 and Hcal00 database values

(warning: the Hcal endcaps are still missing)

  P   S   M   I   J   K   X   Y   Z   E   PID

• P = detector piece:
  • 1 = Ecal end cap -Z
  • 2 = Ecal barrel
  • 3 = Ecal end cap +Z
  • 4 = Hcal end cap -Z
  • 5 = Hcal barrel
  • 6 = Hcal end cap +Z
• S = stave number (1-8 for barrel, 1-4 for endcaps)
• M = module number in stave (1-5 for barrel, 1 for endcaps)
• I,J = the cell coordinates in the cells matrix
• K = Sensitive (Si or scintillator) layer number
• X,Y,Z = cell coordinates
• E = the total energy deposited in the cell.
• PID = primary particle id.

You can read this output file with a Fortran program as the following:

      program readhits
      implicit none

      integer P,S,M,I,J,K,PID
      real x,y,z,e
...
      open (unit=1,file='event000000.hits',status='old')
      read (1,*,end=2000) P,S,M,I,J,K,x,y,z,e,PID
...

 We can do a mapping from some of the Geant4 geometry objects to the Geant3 geometry subroutines, like this one: the Geant4 Solid and LogicalVolume object creations can be translated to a Geant3 GSVOLU call; the Geant4 placement object creation by the Geant3 GPOS one.

• Sample Fortran code generated by Mokka: g4g3.f and g4g3.inc files
• Geant3 Ecal and Hcal view with the code above (thanks to Vassili Djordjadze from DESY-IfH Zeuthen)