////////////////////////////////////////////////
//  Response class for set:ITS                //
////////////////////////////////////////////////

#include <TMath.h>
#include <TF1.h>
#include <TString.h>
#include "AliITSresponse.h"

ClassImp(AliITSresponse)

//______________________________________________________________________
AliITSresponse::AliITSresponse(){
    // Default Constructor

    fdv = 0.000375;  // 300 microns and 80 volts.
    fN  = 0.0;
    fT  = 300.0;
}
//______________________________________________________________________
AliITSresponse::AliITSresponse(Double_t thickness){
    // Default Constructor

    fdv = thickness/80.0;   // 80 volts.
    fN  = 0.0;
    fT  = 300.0;
}
//______________________________________________________________________
Double_t AliITSresponse::MobilityElectronSiEmp(){
    // Computes the electron mobility in cm^2/volt-sec. Taken from SILVACO
    // International ATLAS II, 2D Device Simulation Framework, User Manual 
    // Chapter 5 Equation 5-6. An empirical function for low-field mobiliity 
    // in silicon at different tempeatures.
    // Inputs:
    //    none.
    // Output:
    //    none.
    // Return:
    //    The Mobility of electrons in Si at a give temprature and impurity
    //    concentration. [cm^2/Volt-sec]
    const Double_t m0  = 55.24; // cm^2/Volt-sec
    const Double_t m1  = 7.12E+08; // cm^2 (degree K)^2.3 / Volt-sec
    const Double_t N0  = 1.072E17; // #/cm^3
    const Double_t T0  = 300.; // degree K.
    const Double_t eT0 = -2.3; // Power of Temp.
    const Double_t eT1 = -3.8; // Power of Temp.
    const Double_t eN  = 0.73; // Power of Dopent Consentrations
    Double_t m;
    Double_t T = fT,N = fN;

    if(N<=0.0){ // Simple case.
	if(T==300.) return 1350.0; // From Table 5-1 at consentration 1.0E14.
	m = m1*TMath::Power(T,eT0);
	return m;
    } // if N<=0.0
    m = m1*TMath::Power(T,eT0) - m0;
    m /= 1.0 + TMath::Power(T/T0,eT1)*TMath::Power(N/N0,eN);
    m += m0;
    return m;
}
//______________________________________________________________________
Double_t AliITSresponse::MobilityHoleSiEmp(){
    // Computes the Hole mobility in cm^2/volt-sec. Taken from SILVACO
    // International ATLAS II, 2D Device Simulation Framework, User Manual 
    // Chapter 5 Equation 5-7 An empirical function for low-field mobiliity 
    // in silicon at different tempeatures.
    // Inputs:
    //    none.
    // Output:
    //    none.
    // Return:
    //    The Mobility of Hole in Si at a give temprature and impurity
    //    concentration. [cm^2/Volt-sec]
    const Double_t m0a = 49.74; // cm^2/Volt-sec
    const Double_t m0b = 49.70; // cm^2/Volt-sec
    const Double_t m1  = 1.35E+08; // cm^2 (degree K)^2.3 / Volt-sec
    const Double_t N0  = 1.606E17; // #/cm^3
    const Double_t T0  = 300.; // degree K.
    const Double_t eT0 = -2.2; // Power of Temp.
    const Double_t eT1 = -3.7; // Power of Temp.
    const Double_t eN  = 0.70; // Power of Dopent Consentrations
    Double_t m;
    Double_t T = fT,N = fN;

    if(N<=0.0){ // Simple case.
	if(T==300.) return 495.0; // From Table 5-1 at consentration 1.0E14.
	m = m1*TMath::Power(T,eT0) + m0a-m0b;
	return m;
    } // if N<=0.0
    m = m1*TMath::Power(T,eT0) - m0b;
    m /= 1.0 + TMath::Power(T/T0,eT1)*TMath::Power(N/N0,eN);
    m += m0a;
    return m;
}
//______________________________________________________________________
Double_t AliITSresponse::DiffusionCoefficientElectron(){
    // Computes the Diffusion coefficient for electrons in cm^2/sec. Taken 
    // from SILVACO International ATLAS II, 2D Device Simulation Framework, 
    // User Manual Chapter 5 Equation 5-53. Einstein relations for diffusion 
    // coefficient. Note: 1 cm^2/sec = 10 microns^2/nanosec.
    // Inputs:
    //    none.
    // Output:
    //    none.
    // Return:
    //    The Diffusion Coefficient of electrons in Si at a give temprature
    //    and impurity concentration. [cm^2/sec]
    // const Double_t kb = 1.3806503E-23; // Joules/degree K
    // const Double_t qe = 1.60217646E-19; // Coulumbs.
    const Double_t kbqe = 8.617342312E-5; // Volt/degree K
    Double_t m = MobilityElectronSiEmp();
    Double_t T = fT;

    return m*kbqe*T;  // [cm^2/sec]
}
//______________________________________________________________________
Double_t AliITSresponse::DiffusionCoefficientHole(){
    // Computes the Diffusion coefficient for Holes in cm^2/sec. Taken 
    // from SILVACO International ATLAS II, 2D Device Simulation Framework, 
    // User Manual Chapter 5 Equation 5-53. Einstein relations for diffusion 
    // coefficient. Note: 1 cm^2/sec = 10 microns^2/nanosec.
    // Inputs:
    //    none.
    // Output:
    //    none.
    // Return:
    //    The Defusion Coefficient of Hole in Si at a give temprature and 
    //    impurity concentration. [cm^2/sec]
    //    and impurity concentration. [cm^2/sec]
    // const Double_t kb = 1.3806503E-23; // Joules/degree K
    // const Double_t qe = 1.60217646E-19; // Coulumbs.
    const Double_t kbqe = 8.617342312E-5; // Volt/degree K
    Double_t m = MobilityHoleSiEmp();
    Double_t T = fT;

    return m*kbqe*T;  // [cm^2/sec]
}
//______________________________________________________________________
Double_t AliITSresponse::SpeedElectron(){
    // Computes the average speed for electrons in Si under the low-field 
    // approximation. [cm/sec].
    // Inputs:
    //    none.
    // Output:
    //    none.
    // Return:
    //    The speed the holes are traveling at due to the low field applied. 
    //    [cm/sec]
    Double_t m = MobilityElectronSiEmp();

    return m/fdv;  // [cm/sec]
}
//______________________________________________________________________
Double_t AliITSresponse::SpeedHole(){
    // Computes the average speed for Holes in Si under the low-field 
    // approximation.[cm/sec].
    // Inputs:
    //    none.
    // Output:
    //    none.
    // Return:
    //    The speed the holes are traveling at due to the low field applied. 
    //    [cm/sec]
    Double_t m = MobilityHoleSiEmp();

    return m/fdv;  // [cm/sec]
}
//______________________________________________________________________
Double_t AliITSresponse::SigmaDiffusion3D(Double_t l){
    // Returns the Gaussian sigma^2 == <x^2+y^2+z^2> [cm^2] due to the defusion 
    // of electrons or holes through a distance l [cm] caused by an applied
    // voltage v [volt] through a distance d [cm] in any material at a
    // temperature T [degree K]. The sigma diffusion when expressed in terms
    // of the distance over which the diffusion occures, l=time/speed, is 
    // independent of the mobility and therefore the properties of the
    // material. The charge distributions is given by 
    // n = exp(-r^2/4Dt)/(4piDt)^1.5. From this <r^2> = 6Dt where D=mkT/e
    // (m==mobility, k==Boltzman's constant, T==temparature, e==electric 
    // charge. and vel=m*v/d. consiquently sigma^2=6kTdl/ev.
    // Inputs:
    //    Double_t l   Distance the charge has to travel.
    // Output:
    //    none.
    // Return:
    //    The Sigma due to the diffution of electrons. [cm]
    const Double_t con = 5.17040258E-04; // == 6k/e [J/col or volts]

    return TMath::Sqrt(con*fT*fdv*l);  // [cm]
}
//______________________________________________________________________
Double_t AliITSresponse::SigmaDiffusion2D(Double_t l){
    // Returns the Gaussian sigma^2 == <x^2+z^2> [cm^2] due to the defusion 
    // of electrons or holes through a distance l [cm] caused by an applied
    // voltage v [volt] through a distance d [cm] in any material at a
    // temperature T [degree K]. The sigma diffusion when expressed in terms
    // of the distance over which the diffusion occures, l=time/speed, is 
    // independent of the mobility and therefore the properties of the
    // material. The charge distributions is given by 
    // n = exp(-r^2/4Dt)/(4piDt)^1.5. From this <x^2+z^2> = 4Dt where D=mkT/e
    // (m==mobility, k==Boltzman's constant, T==temparature, e==electric 
    // charge. and vel=m*v/d. consiquently sigma^2=4kTdl/ev.
    // Inputs:
    //    Double_t l   Distance the charge has to travel.
    // Output:
    //    none.
    // Return:
    //    The Sigma due to the diffution of electrons. [cm]
    const Double_t con = 3.446935053E-04; // == 4k/e [J/col or volts]

    return TMath::Sqrt(con*fT*fdv*l);  // [cm]
}
//______________________________________________________________________
Double_t AliITSresponse::SigmaDiffusion1D(Double_t l){
    // Returns the Gaussian sigma^2 == <x^2> [cm^2] due to the defusion 
    // of electrons or holes through a distance l [cm] caused by an applied
    // voltage v [volt] through a distance d [cm] in any material at a
    // temperature T [degree K]. The sigma diffusion when expressed in terms
    // of the distance over which the diffusion occures, l=time/speed, is 
    // independent of the mobility and therefore the properties of the
    // material. The charge distributions is given by 
    // n = exp(-r^2/4Dt)/(4piDt)^1.5. From this <r^2> = 2Dt where D=mkT/e
    // (m==mobility, k==Boltzman's constant, T==temparature, e==electric 
    // charge. and vel=m*v/d. consiquently sigma^2=2kTdl/ev.
    // Inputs:
    //    Double_t l   Distance the charge has to travel.
    // Output:
    //    none.
    // Return:
    //    The Sigma due to the diffution of electrons. [cm]
    const Double_t con = 1.723467527E-04; // == 2k/e [J/col or volts]

    return TMath::Sqrt(con*fT*fdv*l);  // [cm]
}