void Config(){
    // 7-DEC-2000 09:00
    // Switch on Transition Radiation simulation. 6/12/00 18:00
    // iZDC=1  7/12/00 09:00
    // ThetaRange is (0., 180.). It was (0.28,179.72) 7/12/00 09:00
    // Theta range given through pseudorapidity limits 22/6/2001

    // Set Random Number seed
    // gRandom->SetSeed(12345);

    // libraries required by geant321
    gSystem->Load("libgeant321");

    new     TGeant3("C++ Interface to Geant3");

    if (!gSystem->Getenv("CONFIG_FILE"))
    {
        TFile  *rootfile = new TFile("galice.root", "recreate");

        rootfile->SetCompressionLevel(2);
    }

    TGeant3 *geant3 = (TGeant3 *) gMC;

    //
    // Set External decayer
    AliDecayer *decayer = new AliDecayerPythia();

    decayer->SetForceDecay(kAll);
    decayer->Init();
    gMC->SetExternalDecayer(decayer);
    //
    //
    //=======================================================================
    // ******* GEANT STEERING parameters FOR ALICE SIMULATION *******
    geant3->SetTRIG(1);         //Number of events to be processed 
    geant3->SetSWIT(4, 10);
    geant3->SetDEBU(0, 0, 1);
    //geant3->SetSWIT(2,2);
    geant3->SetDCAY(1);
    geant3->SetPAIR(1);
    geant3->SetCOMP(1);
    geant3->SetPHOT(1);
    geant3->SetPFIS(0);
    geant3->SetDRAY(0);
    geant3->SetANNI(1);
    geant3->SetBREM(1);
    geant3->SetMUNU(1);
    geant3->SetCKOV(1);
    geant3->SetHADR(1); //Select pure GEANH (HADR 1) or GEANH/NUCRIN (HADR 3)
    geant3->SetLOSS(2);
    geant3->SetMULS(1);
    geant3->SetRAYL(1);
    geant3->SetAUTO(1); //Select automatic STMIN etc... calc. (AUTO 1) or manual (AUTO 0)
    geant3->SetABAN(0); //Restore 3.16 behaviour for abandoned tracks
    geant3->SetOPTI(2); //Select optimisation level for GEANT geometry searches (0,1,2)
    geant3->SetERAN(5.e-7);

    Float_t cut = 1.e-3;        // 1MeV cut by default
    Float_t tofmax = 1.e10;

    //             GAM ELEC NHAD CHAD MUON EBREM MUHAB EDEL MUDEL MUPA TOFMAX
    geant3->SetCUTS(cut, cut, cut, cut, cut, cut, cut, cut, cut, cut,
                    tofmax);
    //
    //=======================================================================
    // ************* STEERING parameters FOR ALICE SIMULATION **************
    // --- Specify event type to be tracked through the ALICE setup
    // --- All positions are in cm, angles in degrees, and P and E in GeV
    if (gSystem->Getenv("CONFIG_NPARTICLES")){
        int     nParticles = atoi(gSystem->Getenv("CONFIG_NPARTICLES"));
    } else{
        int     nParticles = 500;
    } // end if
    AliGenHIJINGpara *gener = new AliGenHIJINGpara(nParticles);

    gener->SetMomentumRange(0, 999);
    gener->SetPhiRange(0, 360);
    // Set pseudorapidity range from -8 to 8.
    Float_t thmin = EtaToTheta(8);   // theta min. <---> eta max
    Float_t thmax = EtaToTheta(-8);  // theta max. <---> eta min 
    gener->SetThetaRange(thmin,thmax);
    gener->SetOrigin(0, 0, 0);  //vertex position
    gener->SetSigma(0, 0, 0);   //Sigma in (X,Y,Z) (cm) on IP position
    gener->Init();
    // 
    // Activate this line if you want the vertex smearing to happen
    // track by track
    //
    //gener->SetVertexSmear(perTrack); 

    gAlice->SetField(-999, 2);  //Specify maximum magnetic field in Tesla (neg. ==> default field)

    Int_t   iABSO  = 1;
    Int_t   iDIPO  = 1;
    Int_t   iFMD   = 1;
    Int_t   iFRAME = 1;
    Int_t   iHALL  = 1;
    Int_t   iITS   = 1;
    Int_t   iMAG   = 1;
    Int_t   iMUON  = 1;
    Int_t   iPHOS  = 1;
    Int_t   iPIPE  = 1;
    Int_t   iPMD   = 1;
    Int_t   iRICH  = 1;
    Int_t   iSHIL  = 1;
    Int_t   iSTART = 1;
    Int_t   iTOF   = 1;
    Int_t   iTPC   = 1;
    Int_t   iTRD   = 1;
    Int_t   iZDC   = 1;
    Int_t   iEMCAL = 1;

    //=================== Alice BODY parameters =============================
    AliBODY *BODY = new AliBODY("BODY", "Alice envelop");

    if (iMAG){
        //=================== MAG parameters ============================
        // --- Start with Magnet since detector layouts may be depending ---
        // --- on the selected Magnet dimensions ---
        AliMAG *MAG = new AliMAG("MAG", "Magnet");
    }
    if (iABSO){
        //=================== ABSO parameters ============================
        AliABSO *ABSO = new AliABSOv0("ABSO", "Muon Absorber");
    }
    if (iDIPO){
        //=================== DIPO parameters ============================
        AliDIPO *DIPO = new AliDIPOv2("DIPO", "Dipole version 2");
    }
    if (iHALL){
        //=================== HALL parameters ============================
        AliHALL *HALL = new AliHALL("HALL", "Alice Hall");
    }
    if (iFRAME){
        //=================== FRAME parameters ============================
        AliFRAME *FRAME = new AliFRAMEv2("FRAME", "Space Frame");
    }
    if (iSHIL){
        //=================== SHIL parameters ============================
        AliSHIL *SHIL = new AliSHILvF("SHIL", "Shielding");
    }
    if (iPIPE){
        //=================== PIPE parameters ============================
        AliPIPE *PIPE = new AliPIPEv0("PIPE", "Beam Pipe");
    }
    if(iITS) {
	//=================== ITS parameters ============================
	//
	// As the innermost detector in ALICE, the Inner Tracking System 
	// "impacts" on almost all other detectors. This involves the fact
	// that the ITS geometry still has several options to be followed
	//in parallel in order to determine the best set-up which minimizes
	// the induced background. All the geometries available to date are
	// described in the following. Read carefully the comments and use
	// the default version (the only one uncommented) unless you are making
	// comparisons and you know what you are doing. In this case just
	// uncomment the ITS geometry you want to use and run Aliroot.
	// Detailed geometries:
	AliITSvPPRasymm *ITS  = new AliITSvPPRasymm("ITS","New ITS PPR detailed version with asymmetric services");
	ITS->SetMinorVersion(2); // don't touch this parameter if you're not an ITS developer
	ITS->SetReadDet(kFALSE); // don't touch this parameter if you're not an ITS developer
	ITS->SetThicknessDet1(200.); // detector thickness on layer 1 must be in the range [100,300]
	ITS->SetThicknessDet2(200.); // detector thickness on layer 2 must be in the range [100,300]
	ITS->SetThicknessChip1(200.); // chip thickness on layer 1 must be in the range [150,300]
	ITS->SetThicknessChip2(200.);// chip thickness on layer 2 must be in the range [150,300]
	ITS->SetRails(1);	     // 1 --> rails in ; 0 --> rails out
	ITS->SetCoolingFluid(1);   // 1 --> water ; 0 --> freon
	// Geant3 <-> EUCLID conversion
	// ============================
	// SetEUCLID is a flag to output (=1) or not to output (=0) both
	// geometry and media to two ASCII files (called by default
	// ITSgeometry.euc and ITSgeometry.tme) in a format understandable
	// to the CAD system EUCLID.  The default (=0) means that you dont
	// want to use this facility.
	ITS->SetEUCLID(0);  
    }
    if (iTPC){
        //============================ TPC parameters =========================
        // This allows the user to specify sectors for the SLOW (TPC geometry
	// 2) Simulator. SecAL (SecAU) <0 means that ALL lower (upper)
        // sectors are specified, any value other than that requires at least
	// one sector (lower or upper)to be specified!
        // Reminder: sectors  1-24 are lower sectors  ( 1-12->z>0,13-24->z<0)
        //           sectors 25-72 are the upper ones (25-48->z>0,49-72->z<0)
        // SecLows - number of lower sectors specified (up to 6)
        // SecUps - number of upper sectors specified (up to 12)
        // Sens - sensitive strips for the Slow Simulator !!!
        // This does NOT work if all S or L-sectors are specified, i.e.
        // if SecAL or SecAU < 0
        //---------------------------------------------------------------------
        //  gROOT->LoadMacro("SetTPCParam.C");
        //  AliTPCParam *param = SetTPCParam();
        AliTPC *TPC = new AliTPCv2("TPC", "Default");
        // All sectors included 
        TPC->SetSecAL(-1);
        TPC->SetSecAU(-1);
    }
    if (iTOF){
        //=================== TOF parameters ============================
        AliTOF *TOF = new AliTOFv2("TOF", "normal TOF");
    }
    if (iRICH){
        //=================== RICH parameters ===========================
        AliRICH *RICH = new AliRICHv3("RICH", "normal RICH");
    }
    if (iZDC){
        //=================== ZDC parameters ============================
        AliZDC *ZDC = new AliZDCv2("ZDC", "normal ZDC");
    }
    if (iTRD){
        //=================== TRD parameters ============================
        AliTRD *TRD = new AliTRDv1("TRD", "TRD slow simulator");
        // Select the gas mixture (0: 97% Xe + 3% isobutane, 1: 90% Xe +
	// 10% CO2)
        TRD->SetGasMix(1);
        // With hole in front of PHOS
        TRD->SetPHOShole();
        // With hole in front of RICH
        TRD->SetRICHhole();
        // Switch on TR
        AliTRDsim *TRDsim = TRD->CreateTR();
    }
    if (iFMD){
        //=================== FMD parameters ============================
        AliFMD *FMD = new AliFMDv1("FMD", "normal FMD");
        FMD->SetRingsSi1(256);
        FMD->SetRingsSi2(64);
        FMD->SetSectorsSi1(20);
        FMD->SetSectorsSi2(24);
    }
    if (iMUON){
        //=================== MUON parameters ===========================
        AliMUON *MUON = new AliMUONv1("MUON", "default");
    }
    if (iPHOS){
	//=================== PHOS parameters ===========================
        AliPHOS *PHOS = new AliPHOSv1("PHOS", "GPS2");
    }
    if (iPMD){
        //=================== PMD parameters ============================
        AliPMD *PMD = new AliPMDv1("PMD", "normal PMD");
        PMD->SetPAR(1., 1., 0.8, 0.02);
        PMD->SetIN(6., 18., -580., 27., 27.);
        PMD->SetGEO(0.0, 0.2, 4.);
        PMD->SetPadSize(0.8, 1.0, 1.0, 1.5);
    }
    if (iEMCAL){
        //=================== EMCAL parameters ============================
        AliEMCAL *EMCAL = new AliEMCALv1("EMCAL", "G56_2_55_19_104_14");
    }
    if (iSTART){
        //=================== START parameters ============================
        AliSTART *START = new AliSTARTv1("START", "START Detector");
    }
}
//----------------------------------------------------------------------
Float_t EtaToTheta(Float_t arg){
  return (180./TMath::Pi())*2.*atan(exp(-arg));
}