Module trackswim_mod

module trackswim_mod

        ! Uses
    use precision_mod
    use physicalconstants_mod

        ! Types
    private type tdata_type
    private type tstep_type

        ! Subroutines and functions
    private function VectorMultiply (a, b) result (c)
    private function V3mag (a) result (c)
    private function V3magsq (a)
    private subroutine V3unit (V3, Vunit, Vmag)
    private function Prime (B3, V3, P3, Q, K, tdata) result (success)
    private subroutine StepV (tdata, S, tstep, V3)
    private subroutine StepP (tdata, tstep, P3)
    public function TrackGetCR (V3, P3, Q, C, R) result (success)
    public function TrackToSK (V3, P3, Q, S, K) result (success)
    public function TrackToS (V3, P3, Q, S) result (success)
    public function TrackToZKS (V3, P3, Q, ENDZ, K, S) result (success)
    public function TrackToZS (V3, P3, Q, ENDZ, S) result (success)
    public function TrackToZ (V3, P3, Q, ENDZ) result (success)
    public function TrackToZK (V3, P3, Q, ENDZ, K) result (success)

end module trackswim_mod
 ===============================================================
 Author: K.Olchanski
 Date: 13 May 2001
 CVS:  $Id: trackswim_mod.f90,v 1.22 2005/07/02 23:51:20 olchansk Exp $
 --------------------------------------------------------
 Description: Calculate particle trajectories in magnetic field
=========================================================

Description of Types

private type tdata_type
    real (kind=R8) :: P3Mag
             momentum
    real (kind=R8) :: PpMag
             parallel momentum
    real (kind=R8) :: PtMag
             transverse momentum
    real (kind=R8) :: sint
             angle between P3 and B
    real (kind=R8) :: cost
             sin and cos
    real (kind=R8), dimension (3) :: Runit
             Radial unit vector
    real (kind=R8), dimension (3) :: PtUnit
             Transverse unit vector
    real (kind=R8), dimension (3) :: PpUnit
             Parallel unit vector
    real (kind=R8), dimension (3) :: C
             Center of the helix
    real (kind=R8) :: R
             Radius of the helix
    real (kind=R8) :: dRdS
             Energy loss, dR/dS
    real (kind=R8) :: dPdS
             Energy loss, dP/dS
    real (kind=R8) :: PhiCorr
             Energy loss correction
    integer :: Q
             Charge
end type tdata_type
 Invariant track parameters

private type tstep_type
    real (kind=R8) :: S
             arc length
    real (kind=R8) :: R
             radius at new point
    real (kind=R8) :: Phi
             rotation angle
    real (kind=R8) :: sinphi
             sin and cos
    real (kind=R8) :: cosphi
             sin and cos
    real (kind=R8), dimension (3) :: Runit
             rotated unit
    real (kind=R8), dimension (3) :: PtUnit
             vectors
end type tstep_type
 Step-dependant track parameters

Description of Subroutines and Functions

private function VectorMultiply (a, b) result (c)
    real (kind=R8), INTENT(in), dimension (3) :: a
    real (kind=R8), INTENT(in), dimension (3) :: b
    real (kind=R8), dimension (3) :: c
end function VectorMultiply

private function V3mag (a) result (c)
    real (kind=R8), INTENT(in), dimension (3) :: a
    real (kind=R8) :: c
end function V3mag

private function V3magsq (a)
    real (kind=R8), INTENT(in), dimension (3) :: a
    real (kind=R8) :: V3magsq
end function V3magsq

private subroutine V3unit (V3, Vunit, Vmag)
    real (kind=R8), INTENT(in), dimension (3) :: V3
             input vector
    real (kind=R8), INTENT(out), dimension (3) :: Vunit
             return unit vector
    real (kind=R8), INTENT(out) :: Vmag
             return magnitude
end subroutine V3unit
 Purpose: Calculate magnitude and unit vector

private function Prime (B3, V3, P3, Q, K, tdata) result (success)
    real (kind=R8), INTENT(in), dimension (3) :: B3
             Arguments:

 magnetic field  (T)
    real (kind=R8), INTENT(in), dimension (3) :: V3
             starting point  (cm)
    real (kind=R8), INTENT(in), dimension (3) :: P3
             momentum vector (MeV)
    integer (kind=I4), INTENT(in) :: Q
             charge
    real (kind=R8), INTENT(in) :: K
             energy loss, dP/dS (MeV/cm)
    type (tdata_type), INTENT(out) :: tdata
             output helix data
    logical :: success
    ! Calls: V3unit
end function Prime
 Description: Calculate invariant helix data

private subroutine StepV (tdata, S, tstep, V3)
    type (tdata_type), INTENT(in) :: tdata
             invariant helix data
    real (kind=R8), INTENT(in) :: S
             arc length
    type (tstep_type), INTENT(out) :: tstep
             step data
    real (kind=R8), INTENT(inout), dimension (3) :: V3
             new position
end subroutine StepV
 Description: Given arc length S, calculate position on the helix

private subroutine StepP (tdata, tstep, P3)
    type (tdata_type), INTENT(in) :: tdata
             invariant helix data
    type (tstep_type), INTENT(in) :: tstep
             step data
    real (kind=R8), INTENT(out), dimension (3) :: P3
             new momentum
end subroutine StepP
 Description: Calculate the end-point momentum

public function TrackGetCR (V3, P3, Q, C, R) result (success)
    real (kind=R8), INTENT(in), dimension (3) :: V3
            
 Purpose: Return the center and radius of the helix

 position (cm)
    real (kind=R8), INTENT(in), dimension (3) :: P3
             momentum (MeV)
    integer (kind=I4), INTENT(in) :: Q
             charge
    real (kind=R8), INTENT(out), dimension (3) :: C
             return center of the helix
    real (kind=R8), INTENT(out) :: R
             return radius
    logical :: success
end function TrackGetCR

public function TrackToSK (V3, P3, Q, S, K) result (success)
    real (kind=R8), INTENT(inout), dimension (3) :: V3
             position (cm)
    real (kind=R8), INTENT(inout), dimension (3) :: P3
             momentum (MeV)
    integer (kind=I4), INTENT(in) :: Q
             charge
    real (kind=R8), INTENT(in) :: S
             arc length
    real (kind=R8), INTENT(in) :: K
             energy loss dP/dS (MeV/cm)
    logical :: success
             return value
    ! Calls: StepP, StepV
end function TrackToSK
 Description: move along the helix by given arc length S

 Return value: .TRUE. success, .FALSE. failure

public function TrackToS (V3, P3, Q, S) result (success)
    real (kind=R8), INTENT(inout), dimension (3) :: V3
             position (cm)
    real (kind=R8), INTENT(inout), dimension (3) :: P3
             momentum (MeV)
    integer (kind=I4), INTENT(in) :: Q
             charge
    real (kind=R8), INTENT(in) :: S
             arc length
    logical :: success
             return value
end function TrackToS
===================================================
 Description: see TrackToSK()
====================================================

public function TrackToZKS (V3, P3, Q, ENDZ, K, S) result (success)
    real (kind=R8), INTENT(inout), dimension (3) :: V3
             position (cm)
    real (kind=R8), INTENT(inout), dimension (3) :: P3
             momentum (MeV)
    integer (kind=I4), INTENT(in) :: Q
             charge
    real (kind=R8), INTENT(in) :: ENDZ
             z plane
    real (kind=R8), INTENT(in) :: K
             energy loss, dR/dS
    real (kind=R8), INTENT(out) :: S
             return arc length
    logical :: success
             return value
    ! Calls: kerror
end function TrackToZKS
==========================================================
 Description: Find point of intersection with given Z plane

 Return value: .TRUE. success, .FALSE. failure
============================================================

public function TrackToZS (V3, P3, Q, ENDZ, S) result (success)
    real (kind=R8), INTENT(inout), dimension (3) :: V3
             position (cm)
    real (kind=R8), INTENT(inout), dimension (3) :: P3
             momentum (MeV)
    integer (kind=I4), INTENT(in) :: Q
             charge
    real (kind=R8), INTENT(in) :: ENDZ
             z plane
    real (kind=R8), INTENT(out) :: S
             return arc length
    logical :: success
             return value
end function TrackToZS
 Description: See TrackToZKS()
 For calcs without energy loss 

public function TrackToZ (V3, P3, Q, ENDZ) result (success)
    real (kind=R8), INTENT(inout), dimension (3) :: V3
             position (cm)
    real (kind=R8), INTENT(inout), dimension (3) :: P3
             momentum (MeV)
    integer (kind=I4), INTENT(in) :: Q
             charge
    real (kind=R8), INTENT(in) :: ENDZ
             z plane
    logical :: success
             return value
end function TrackToZ
 For no energy loss
 Description: See TrackToSKZ()
 

public function TrackToZK (V3, P3, Q, ENDZ, K) result (success)
    real (kind=R8), INTENT(inout), dimension (3) :: V3
             position (cm)
    real (kind=R8), INTENT(inout), dimension (3) :: P3
             momentum (MeV)
    integer (kind=I4), INTENT(in) :: Q
             charge
    real (kind=R8), INTENT(in) :: ENDZ
             z plane
    real (kind=R8), INTENT(in) :: K
             energy loss, dP/dS (MeV/cm)
    logical :: success
             return value
end function TrackToZK
 
 Description: See TrackToZKS()
 No energy loss