korc_experimental_pdf.f90 Source File


Contents


Source Code

MODULE korc_experimental_pdf
  USE korc_types
  USE korc_constants
  USE korc_HDF5
  USE korc_hpc
  USE special_functions
  use korc_coords
  use korc_rnd_numbers
  use korc_random
  use korc_fields

  IMPLICIT NONE

  TYPE, PRIVATE :: PARAMS
     REAL(rp) :: E ! Parallel electric field normalized using the critical electric field
     REAL(rp) :: Zeff ! Effective atomic number of impurities

     REAL(rp) :: max_pitch_angle ! Maximum pitch angle of sampled PDF in degrees
     REAL(rp) :: min_pitch_angle ! Minimum pitch angle of sampled PDF in degrees
     REAL(rp) :: min_energy ! Minimum energy of sampled PDF in MeV
     REAL(rp) :: max_energy ! Maximum energy of sampled PDF in MeV
     REAL(rp) :: min_p ! Minimum momentum of sampled PDF
     REAL(rp) :: max_p ! Maximum momentum of sampled PDF
     REAL(rp) :: k ! Shape factor of Gamma distribution
     REAL(rp) :: t ! Scale factor of Gamma distribution
     REAL(rp) :: fGo ! Normalization factor of Gamma distribution

     REAL(rp) :: Bo
     REAL(rp) :: lambda

     REAL(rp) :: A_fact ! Multiplication factor for A in distributon.
  END TYPE PARAMS

  TYPE, PRIVATE :: HOLLMANN_PARAMS
     CHARACTER(MAX_STRING_LENGTH) :: filename
     REAL(rp) :: E
     REAL(rp) :: Eo
     REAL(rp) :: sigma_E
     REAL(rp) :: Zeff
     REAL(rp) :: sigma_Z
     REAL(rp) :: max_pitch_angle
     REAL(rp) :: min_pitch_angle
     REAL(rp) :: min_sampling_energy ! Minimum energy of sampled PDF in MeV
     REAL(rp) :: max_sampling_energy ! Maximum energy of sampled PDF in MeV
     REAL(rp) :: min_sampling_g ! Minimum energy of sampled PDF in MeV
     REAL(rp) :: max_sampling_g ! Maximum energy of sampled PDF in MeV

     REAL(rp) :: min_energy ! Minimum energy of sampled PDF in MeV
     REAL(rp) :: max_energy ! Maximum energy of sampled PDF in MeV
     REAL(rp) :: min_g ! Minimum energy of sampled PDF in MeV
     REAL(rp) :: max_g ! Maximum energy of sampled PDF in MeV
     REAL(rp) :: min_pitch ! Minimum energy of sampled PDF in MeV
     REAL(rp) :: max_pitch ! Maximum energy of sampled PDF in MeV

     INTEGER :: N

     REAL(rp), DIMENSION(:), ALLOCATABLE :: E_axis
     REAL(rp), DIMENSION(:), ALLOCATABLE :: g
     REAL(rp), DIMENSION(:), ALLOCATABLE :: fRE_E
     REAL(rp), DIMENSION(:), ALLOCATABLE :: fRE_pitch

     CHARACTER(MAX_STRING_LENGTH) :: current_direction
     REAL(rp) :: Bo
     REAL(rp) :: lambda

     REAL(rp) :: A_fact ! Multiplication factor for A in distributon.
  END TYPE HOLLMANN_PARAMS

  TYPE(PARAMS), PRIVATE :: pdf_params
  TYPE(HOLLMANN_PARAMS), PRIVATE :: h_params
  REAL(rp), PRIVATE, PARAMETER :: xo = (C_ME*C_C**2/C_E)/1.0E6
  REAL(rp), PRIVATE, PARAMETER :: Tol = 1.0E-5_rp
  REAL(rp), PRIVATE, PARAMETER :: minmax_buffer_size = 10.0_rp

  PUBLIC :: get_experimentalG_distribution,&
       get_Hollmann_distribution,&
       get_Hollmann_distribution_3D,&
       get_Hollmann_distribution_3D_psi,&
       initialize_Hollmann_params,&
       sample_Hollmann_distribution
  PRIVATE :: initialize_params,&
       save_params,&
       sample_distribution,&
       deg2rad,&
       rad2deg,&
       fRE,&
       fRExPR,&
       random_norm,&
       fGamma,&
       PR,&
       P_integral,&
       IntK,&
       IntBesselK,&
       IntGamma,&
       fRE_H,&
       fRE_pitch

CONTAINS

  SUBROUTINE get_experimentalG_distribution(params,g,eta,go,etao)
    TYPE(KORC_PARAMS), INTENT(IN) :: params
    REAL(rp), DIMENSION(:), ALLOCATABLE, INTENT(INOUT) :: g
    REAL(rp), DIMENSION(:), ALLOCATABLE, INTENT(INOUT) :: eta
    REAL(rp), INTENT(OUT) :: go
    REAL(rp), INTENT(OUT) :: etao

    call initialize_params(params)

    call save_params(params)

    call sample_distribution(params,g,eta,go,etao)
  END SUBROUTINE get_experimentalG_distribution


  SUBROUTINE initialize_params(params)
    TYPE(KORC_PARAMS), INTENT(IN) :: params
    REAL(rp) :: max_pitch_angle
    REAL(rp) :: min_pitch_angle
    REAL(rp) :: max_energy
    REAL(rp) :: min_energy
    REAL(rp) :: Zeff
    REAL(rp) :: E
    REAL(rp) :: k
    REAL(rp) :: t
    REAL(rp) :: Bo
    REAL(rp) :: lambda
    REAL(rp) :: A_fact

    NAMELIST /ExperimentalPDF/ max_pitch_angle,min_pitch_angle,max_energy,min_energy,Zeff,E,k,t,Bo,lambda, &
         A_fact

    open(unit=default_unit_open,file=TRIM(params%path_to_inputs),status='OLD',form='formatted')
    read(default_unit_open,nml=ExperimentalPDF)
    close(default_unit_open)

    pdf_params%max_pitch_angle = max_pitch_angle
    pdf_params%min_pitch_angle = min_pitch_angle
    pdf_params%min_energy = min_energy*C_E ! In Joules
    pdf_params%max_energy = max_energy*C_E ! In Joules
    pdf_params%Zeff = Zeff
    pdf_params%E = E
    pdf_params%k = k
    pdf_params%t = t
    pdf_params%Bo = Bo
    pdf_params%lambda = lambda

    pdf_params%max_p = SQRT((pdf_params%max_energy/(C_ME*C_C**2))**2 - 1.0_rp) ! In units of mc
    pdf_params%min_p = SQRT((pdf_params%min_energy/(C_ME*C_C**2))**2 - 1.0_rp) ! In units of mc

    pdf_params%fGo = &
         IntGamma(SQRT(pdf_params%min_p**2.0_rp + 1.0_rp),SQRT(pdf_params%max_p**2.0_rp + 1.0_rp),pdf_params%k,pdf_params%t/xo)

    pdf_params%A_fact = A_fact
  END SUBROUTINE initialize_params


  FUNCTION deg2rad(x)
    REAL(rp), INTENT(IN) :: x
    REAL(rp) :: deg2rad

    deg2rad = C_PI*x/180.0_rp
  END FUNCTION deg2rad


  FUNCTION rad2deg(x)
    REAL(rp), INTENT(IN) :: x
    REAL(rp) :: rad2deg

    rad2deg = 180.0_rp*x/C_PI
  END FUNCTION rad2deg


  FUNCTION fGamma(x,k,t)
    REAL(rp), INTENT(IN) :: x ! Independent variable
    REAL(rp), INTENT(IN) :: k ! Shape factor
    REAL(rp), INTENT(IN) :: t ! Scale factor
    REAL(rp) :: fGamma

    fGamma = x**(k - 1.0_rp)*EXP(-x/t)/(GAMMA(k)*t**k)
  END FUNCTION fGamma


  FUNCTION fRE(eta,p)
    REAL(rp), INTENT(IN) 	:: eta ! pitch angle in degrees
    REAL(rp), INTENT(IN) 	:: p ! momentum in units of mc
    REAL(rp) 				:: fRE
    REAL(rp) 				:: fE
    REAL(rp) 				:: feta
    REAL(rp) 				:: A
    REAL(rp) 				:: Eo

    Eo = SQRT(p**2.0_rp + 1.0_rp)

    A = (2.0_rp*pdf_params%E/(pdf_params%Zeff + 1.0_rp))*(p**2/SQRT(p**2.0_rp + 1.0_rp))
    A = A*pdf_params%A_fact
    feta = 0.5_rp*A*EXP(A*COS(deg2rad(eta)))/SINH(A)

    fE = fGamma(Eo,pdf_params%k,pdf_params%t/xo)/pdf_params%fGo

    fRE = fE*feta
  END FUNCTION fRE


  FUNCTION fRExPR(eta,p)
    REAL(rp), INTENT(IN) :: eta ! pitch angle in degrees
    REAL(rp), INTENT(IN) :: p ! momentum in units of mc
    REAL(rp) :: fRExPR
    REAL(rp) :: A
    REAL(rp) :: Eo

    fRExPR = fRE(eta,p)*PR(eta,p,pdf_params%Bo,pdf_params%lambda)
  END FUNCTION fRExPR


  FUNCTION random_norm(mean,sigma)
    REAL(rp), INTENT(IN) :: mean
    REAL(rp), INTENT(IN) :: sigma
    REAL(rp) :: random_norm
    REAL(rp) :: rand1, rand2

    call RANDOM_NUMBER(rand1)
    call RANDOM_NUMBER(rand2)

    random_norm = mean+sigma*SQRT(-2.0_rp*LOG(rand1))*COS(2.0_rp*C_PI*rand2)
  END FUNCTION random_norm


  FUNCTION IntK(v,x)
    REAL(rp) :: IntK
    REAL(rp), INTENT(IN) :: v
    REAL(rp), INTENT(IN) :: x

    IntK = (C_PI/SQRT(2.0_rp))*(1.0_rp - 0.25_rp*(4.0_rp*v**2 - 1.0_rp))*ERFC(SQRT(x))&
         + 0.25_rp*(4.0_rp*v**2 - 1.0_rp)*SQRT(0.5_rp*C_PI/x)*EXP(-x)
  END FUNCTION IntK


  FUNCTION besselk(v,x)
    REAL(rp) :: besselk
    REAL(rp), INTENT(IN) :: x
    REAL(rp), INTENT(IN) :: v
    REAL(4) :: ri,rk,rip,rkp

    call bessik(REAL(x,4),REAL(v,4),ri,rk,rip,rkp)
    besselk = REAL(rk,rp)
  END FUNCTION besselk


  !> @brief Extended trapezoidal rule for integrating the Gamma PDF. See Sec. 4.2 of Numerical Recipies in Fortran 77.
  FUNCTION IntGamma(a,b,k,t)
    REAL(rp), INTENT(IN) :: a
    REAL(rp), INTENT(IN) :: b
    REAL(rp), INTENT(IN) :: k ! shape factor
    REAL(rp), INTENT(IN) :: t ! scale factor
    REAL(rp) :: IntGamma
    REAL(rp) :: Iold
    REAL(rp) :: Inew
    REAL(rp) :: rerr
    REAL(rp) :: sum_f
    REAL(rp) :: h,z
    INTEGER :: ii,jj,npoints
    LOGICAL :: flag

    h = b - a
    sum_f = 0.5*(fGamma(a,k,t) + fGamma(b,k,t))

    Iold = 0.0_rp
    Inew = sum_f*h

    ii = 1_idef
    flag = .TRUE.
    do while (flag)
       Iold = Inew

       ii = ii + 1_idef
       npoints = 2_idef**(ii-2_idef)
       h = 0.5_rp*(b-a)/REAL(npoints,rp)
       sum_f = 0.0_rp
       do jj=1_idef,npoints
          z = a + h + 2.0_rp*(REAL(jj,rp) - 1.0_rp)*h
          sum_f = sum_f + fGamma(z,k,t)
       end do

       Inew = 0.5_rp*Iold + sum_f*h
       rerr = ABS((Inew - Iold)/Iold)
       flag = .NOT.(rerr.LT.Tol)
    end do
    IntGamma = Inew
  END FUNCTION IntGamma

  !> @brief Extended trapezoidal rule for integrating the modified Bessel function of second kind. See Sec. 4.2 of Numerical Recipies in Fortran 77.
  FUNCTION IntBesselK(a,b)
    REAL(rp), INTENT(IN) :: a
    REAL(rp), INTENT(IN) :: b
    REAL(rp) :: IntBesselK
    REAL(rp) :: Iold
    REAL(rp) :: Inew
    REAL(rp) :: rerr
    REAL(rp) :: sum_f
    REAL(rp) :: v,h,z
    INTEGER :: ii,jj,npoints
    LOGICAL :: flag

    v = 5.0_rp/3.0_rp
    h = b - a
    sum_f = 0.5*(besselk(v,a) + besselk(v,b))

    Iold = 0.0_rp
    Inew = sum_f*h

    ii = 1_idef
    flag = .TRUE.
    do while (flag)
       Iold = Inew

       ii = ii + 1_idef
       npoints = 2_idef**(ii-2_idef)
       h = 0.5_rp*(b-a)/REAL(npoints,rp)
       sum_f = 0.0_rp
       do jj=1_idef,npoints
          z = a + h + 2.0_rp*(REAL(jj,rp) - 1.0_rp)*h
          sum_f = sum_f + besselk(v,z)
       end do

       Inew = 0.5_rp*Iold + sum_f*h
       rerr = ABS((Inew - Iold)/Iold)
       flag = .NOT.(rerr.LT.Tol)
    end do
    IntBesselK = Inew
  END FUNCTION IntBesselK


  SUBROUTINE P_integral(z,P)
    REAL(rp), INTENT(OUT) :: P
    REAL(rp), INTENT(IN) :: z
    REAL(rp) :: a

    P = 0.0_rp

    IF (z .LT. 0.5_rp) THEN
       a = (2.16_rp/2.0_rp**(2.0_rp/3.0_rp))*z**(1.0_rp/3.0_rp)
       P = IntBesselK(z,a) + IntK(5.0_rp/3.0_rp,a)
    ELSE IF ((z .GE. 0.5_rp).AND.(z .LT. 2.5_rp)) THEN
       a = 0.72_rp*(z + 1.0_rp)
       P = IntBesselK(z,a) + IntK(5.0_rp/3.0_rp,a)
    ELSE
       P = IntK(5.0_rp/3.0_rp,z)
    END IF
  END SUBROUTINE P_integral


  FUNCTION PR(eta,p,Bo,l)
    REAL(rp), INTENT(IN) :: eta ! in radians
    REAL(rp), INTENT(IN) :: p ! dimensionless (in units of mc)
    REAL(rp), INTENT(IN) :: Bo
    REAL(rp), INTENT(IN) :: l
    REAL(rp) :: PR
    REAL(rp) :: g
    REAL(rp) :: v
    REAL(rp) :: k
    REAL(rp) :: lc
    REAL(rp) :: z
    REAL(rp) :: Pi

    g = SQRT(p**2 + 1.0_rp)
    v = C_C*SQRT(1.0_rp - 1.0_rp/g**2)

    k = C_E*Bo*SIN(deg2rad(eta))/(g*C_ME*v)

    lc = (4.0_rp*C_PI/3.0_rp)/(k*g**3) ! Critical wavelength

    z = lc/l

    call P_integral(z,Pi)

    PR = (C_C*C_E**2)*Pi/(SQRT(3.0_rp)*C_E0*g**2*l**3)
  END FUNCTION PR


  SUBROUTINE sample_distribution(params,g,eta,go,etao)
    TYPE(KORC_PARAMS), INTENT(IN) 				:: params
    REAL(rp), DIMENSION(:), ALLOCATABLE, INTENT(INOUT) 	:: g
    REAL(rp), DIMENSION(:), ALLOCATABLE, INTENT(INOUT) 	:: eta
    REAL(rp), INTENT(OUT) 					:: go
    REAL(rp), INTENT(OUT) 					:: etao
    REAL(rp) 					:: go_root
    REAL(rp) 					:: etao_root
    REAL(rp), DIMENSION(:), ALLOCATABLE 		:: p
    REAL(rp) 					:: p_buffer
    REAL(rp) 					:: p_test
    REAL(rp) 					:: eta_buffer
    REAL(rp) 					:: eta_test
    REAL(rp) 					:: ratio
    REAL(rp) 					:: rand_unif
    REAL(rp), DIMENSION(:), ALLOCATABLE 		:: p_samples
    REAL(rp), DIMENSION(:), ALLOCATABLE 		:: eta_samples
    REAL(rp), DIMENSION(:), ALLOCATABLE 		:: p_tmp
    REAL(rp), DIMENSION(:), ALLOCATABLE 		:: eta_tmp
    REAL(rp) 					:: minmax
    REAL(rp) 					:: min_p
    REAL(rp) 					:: max_p
    REAL(rp) 					:: min_pitch_angle
    REAL(rp) 					:: max_pitch_angle
    REAL(rp) 					:: deta
    REAL(rp) 					:: dp
    LOGICAL 					:: lp
    LOGICAL 					:: leta
    INTEGER 					:: num_accepted
    INTEGER 					:: ii
    INTEGER 					:: jj
    INTEGER 					:: ppp
    INTEGER 					:: nsamples
    INTEGER 					:: mpierr

    ppp = SIZE(g)
    nsamples = ppp*params%mpi_params%nmpi
    ALLOCATE(p(ppp))

    deta = (pdf_params%max_pitch_angle - &
         pdf_params%min_pitch_angle)/100.0_rp
    dp = (pdf_params%max_p - pdf_params%min_p)/100.0_rp

    do jj=1_idef,INT(minmax_buffer_size,idef)
       minmax = pdf_params%min_p - REAL(jj,rp)*dp
       if (minmax.GT.0.0_rp) then
          min_p = minmax
       end if
    end do

    max_p = pdf_params%max_p + minmax_buffer_size*dp

    if (pdf_params%min_pitch_angle.GE.korc_zero) then
       do jj=1_idef,INT(minmax_buffer_size,idef)
          minmax = pdf_params%min_pitch_angle -  REAL(jj,rp)*deta
          if (minmax.GT.0.0_rp) then
             min_pitch_angle = minmax
          end if
       end do
    else
       min_pitch_angle = 0.0_rp
    end if

    do jj=1_idef,INT(minmax_buffer_size,idef)
       minmax = pdf_params%max_pitch_angle + REAL(jj,rp)*deta
       if (minmax.LE.90.0_rp) then
          max_pitch_angle = minmax
       else
          max_pitch_angle = pdf_params%max_pitch_angle
          EXIT
       end if
    end do

    if (params%mpi_params%rank.EQ.0_idef) then
       ALLOCATE(p_samples(nsamples))
       ! Number of samples to distribute among all MPI processes
       ALLOCATE(eta_samples(nsamples))
       ! Number of samples to distribute among all MPI processes
       ALLOCATE(p_tmp(nsamples))
       ! Number of samples to distribute among all MPI processes
       ALLOCATE(eta_tmp(nsamples))
       ! Number of samples to distribute among all MPI processes


       !* * * Transient * * *!
       call RANDOM_SEED()

       call RANDOM_NUMBER(rand_unif)
       eta_buffer = pdf_params%min_pitch_angle + &
            (pdf_params%max_pitch_angle - pdf_params%min_pitch_angle)*rand_unif

       call RANDOM_NUMBER(rand_unif)
       p_buffer = pdf_params%min_p + (pdf_params%max_p - &
            pdf_params%min_p)*rand_unif

       ii=2_idef
       do while (ii .LE. 1000_idef)
          eta_test = eta_buffer + random_norm(0.0_rp,deta)
          do while ((ABS(eta_test) .GT. pdf_params%max_pitch_angle).OR. &
               (ABS(eta_test) .LT. pdf_params%min_pitch_angle))
             eta_test = eta_buffer + random_norm(0.0_rp,deta)
          end do

          p_test = p_buffer + random_norm(0.0_rp,dp)
          do while ((p_test.LT.pdf_params%min_p).OR.(p_test.GT. &
               pdf_params%max_p))
             p_test = p_buffer + random_norm(0.0_rp,dp)
          end do

          ratio = fRE(eta_test,p_test)/fRE(eta_buffer,p_buffer)

          if (ratio .GE. 1.0_rp) then
             p_buffer = p_test
             eta_buffer = eta_test
             ii = ii + 1_idef
          else
             call RANDOM_NUMBER(rand_unif)
             if (rand_unif .LT. ratio) then
                p_buffer = p_test
                eta_buffer = eta_test
                ii = ii + 1_idef
             end if
          end if
       end do
       !* * * Transient * * *!

       eta_tmp(1) = eta_buffer
       p_tmp(1) = p_buffer

       num_accepted = 0_idef
       do while(num_accepted.LT.nsamples)
          ii=2_idef
          do while (ii .LE. nsamples)
             eta_test = eta_tmp(ii-1) + random_norm(0.0_rp,deta)
             do while ((ABS(eta_test) .GT. max_pitch_angle).OR. &
                  (ABS(eta_test) .LT. min_pitch_angle))
                eta_test = eta_tmp(ii-1) + random_norm(0.0_rp,deta)
             end do

             p_test = p_tmp(ii-1) + random_norm(0.0_rp,dp)
             do while ((p_test.LT.min_p).OR.(p_test.GT.max_p))
                p_test = p_tmp(ii-1) + random_norm(0.0_rp,dp)
             end do

             ratio = fRE(eta_test,p_test)/fRE(eta_tmp(ii-1),p_tmp(ii-1))

             if (ratio .GE. 1.0_rp) then
                p_tmp(ii) = p_test
                eta_tmp(ii) = eta_test
                ii = ii + 1_idef
             else
                call RANDOM_NUMBER(rand_unif)
                if (rand_unif .LT. ratio) then
                   p_tmp(ii) = p_test
                   eta_tmp(ii) = eta_test
                   ii = ii + 1_idef
                end if
             end if
          end do

          eta_tmp = ABS(eta_tmp)

          ii = 1_idef
          do while ( (ii.LT.nsamples).AND.(num_accepted.LT.nsamples) )
             lp = (p_tmp(ii).LE.pdf_params%max_p).AND.(p_tmp(ii).GE. &
                  pdf_params%min_p)
             leta = (eta_tmp(ii).LE.pdf_params%max_pitch_angle).AND. &
                  (eta_tmp(ii).GE.pdf_params%min_pitch_angle)
             if (lp.AND.leta) then
                num_accepted = num_accepted + 1_idef
                p_samples(num_accepted) = p_tmp(ii)
                eta_samples(num_accepted) = eta_tmp(ii)
             end if
             ii = ii + 1_idef
          end do
       end do

       go = SUM(SQRT(1.0_rp + p_samples**2))/nsamples
       etao = SUM(eta_samples)/nsamples
    end if

    CALL MPI_SCATTER(p_samples,ppp,MPI_REAL8,p,ppp,MPI_REAL8,0,MPI_COMM_WORLD,mpierr)

    CALL MPI_SCATTER(eta_samples,ppp,MPI_REAL8,eta,ppp,MPI_REAL8,0,MPI_COMM_WORLD,mpierr)

    CALL MPI_BCAST(go,1,MPI_REAL8,0,MPI_COMM_WORLD,mpierr)

    CALL MPI_BCAST(etao,1,MPI_REAL8,0,MPI_COMM_WORLD,mpierr)

    call MPI_BARRIER(MPI_COMM_WORLD,mpierr)

    g = SQRT(1.0_rp + p**2)

    DEALLOCATE(p)
    if (params%mpi_params%rank.EQ.0_idef) then
       DEALLOCATE(p_samples)
       DEALLOCATE(eta_samples)
       DEALLOCATE(p_tmp)
       DEALLOCATE(eta_tmp)
    end if

  END SUBROUTINE sample_distribution


  SUBROUTINE get_Hollmann_distribution(params,spp)
    TYPE(KORC_PARAMS), INTENT(IN) :: params
    TYPE(SPECIES),  INTENT(INOUT) :: spp
!    REAL(rp), DIMENSION(:), ALLOCATABLE, INTENT(INOUT) :: g
!    REAL(rp), DIMENSION(:), ALLOCATABLE, INTENT(INOUT) :: eta
!    REAL(rp), INTENT(OUT) :: go
!    REAL(rp), INTENT(OUT) :: etao

    call initialize_Hollmann_params(params)

    call save_Hollmann_params(params)

    call sample_Hollmann_distribution(params,spp)


  END SUBROUTINE get_Hollmann_distribution

  SUBROUTINE get_Hollmann_distribution_3D(params,spp,F)
    TYPE(FIELDS), INTENT(IN)                                   :: F
    TYPE(KORC_PARAMS), INTENT(IN) :: params
    TYPE(SPECIES),  INTENT(INOUT) :: spp

    call initialize_Hollmann_params(params)

    call save_Hollmann_params(params)

    call normalize_Hollmann_params(params)

    call sample_Hollmann_distribution_3D(params,spp,F)

  END SUBROUTINE get_Hollmann_distribution_3D
  
  SUBROUTINE get_Hollmann_distribution_3D_psi(params,spp,F)
    TYPE(FIELDS), INTENT(IN)                                   :: F
    TYPE(KORC_PARAMS), INTENT(INOUT) :: params
    TYPE(SPECIES),  INTENT(INOUT) :: spp

    call initialize_Hollmann_params(params)

    call save_Hollmann_params(params)

    call normalize_Hollmann_params(params)

    call sample_Hollmann_distribution_3D_psi(params,spp,F)

  END SUBROUTINE get_Hollmann_distribution_3D_psi

  SUBROUTINE initialize_Hollmann_params(params)
    TYPE(KORC_PARAMS), INTENT(IN) :: params
    CHARACTER(MAX_STRING_LENGTH) :: filename
    CHARACTER(MAX_STRING_LENGTH) :: current_direction
    REAL(rp) :: E,sigma_E,Eo
    REAL(rp) :: Zeff,sigma_Z
    REAL(rp) :: max_pitch_angle
    REAL(rp) :: min_pitch_angle
    REAL(rp) :: max_energy
    REAL(rp) :: min_energy
    REAL(rp) :: Bo
    REAL(rp) :: lambda
    REAL(rp) :: A_fact

    NAMELIST /HollmannPDF/ E,Zeff,max_pitch_angle,min_pitch_angle,max_energy, &
         min_energy,filename,Bo,lambda,current_direction,A_fact,sigma_E, &
         sigma_Z,Eo


    open(unit=default_unit_open,file=TRIM(params%path_to_inputs), &
         status='OLD',form='formatted')
    read(default_unit_open,nml=HollmannPDF)
    close(default_unit_open)

    h_params%filename = TRIM(filename)

    h_params%E = E
    h_params%Eo = Eo
    h_params%sigma_E = sigma_E
    h_params%Zeff = Zeff
    h_params%sigma_Z = sigma_Z
    h_params%max_pitch_angle = max_pitch_angle
    h_params%min_pitch_angle = min_pitch_angle

    h_params%min_sampling_energy = min_energy*C_E ! In Joules
    h_params%min_sampling_g = 1.0_rp + h_params%min_sampling_energy/ &
         (C_ME*C_C**2)
    h_params%max_sampling_energy = max_energy*C_E ! In Joules.
    h_params%max_sampling_g = 1.0_rp + h_params%max_sampling_energy/ &
         (C_ME*C_C**2)

    call load_data_from_hdf5()
    ! loads h_params%E_axis 1D energy range, h_params%fRE_E
    ! energy distribution as a function of h_params%E_axis,
    ! and h_params%fRE_pitch pitch angle distribution as a
    ! function of h_params%E_axis

    ALLOCATE(h_params%g(h_params%N))

    h_params%g = 1.0_rp + h_params%E_axis/(C_ME*C_C**2)
    ! 1D range of gamma based on energy range from Hollmann input file
    h_params%max_g = MAXVAL(h_params%g)
    h_params%min_g = MINVAL(h_params%g)

    h_params%current_direction = TRIM(current_direction)

    h_params%Bo = Bo
    h_params%lambda = lambda

    h_params%A_fact = A_fact
  END SUBROUTINE initialize_Hollmann_params

  subroutine normalize_Hollmann_params(params)
    TYPE(KORC_PARAMS), INTENT(IN) :: params

    h_params%sigma_E = h_params%sigma_E/params%cpp%length
    h_params%sigma_Z = h_params%sigma_Z/params%cpp%length
    
  end subroutine normalize_Hollmann_params

  SUBROUTINE load_data_from_hdf5()
    CHARACTER(MAX_STRING_LENGTH) :: filename
    CHARACTER(MAX_STRING_LENGTH) :: gname
    CHARACTER(MAX_STRING_LENGTH) :: subgname
    CHARACTER(MAX_STRING_LENGTH) :: dset
    INTEGER(HID_T) :: h5file_id
    INTEGER(HID_T) :: group_id
    INTEGER(HID_T) :: subgroup_id
    REAL(rp) :: rdatum
    INTEGER :: h5error

    filename = TRIM(h_params%filename)
    call h5fopen_f(filename, H5F_ACC_RDONLY_F, h5file_id, h5error)
    if (h5error .EQ. -1) then
       write(6,'("KORC ERROR: Something went wrong in: load_data_from_hdf5 (korc_experimental) --> h5fopen_f")')
    end if

    dset = "/N"
    call load_from_hdf5(h5file_id,dset,rdatum)
    h_params%N = INT(rdatum)

    ALLOCATE(h_params%E_axis(h_params%N))
    ALLOCATE(h_params%fRE_E(h_params%N))
    ALLOCATE(h_params%fRE_pitch(h_params%N))

    dset = "/E"
    call load_array_from_hdf5(h5file_id,dset,h_params%E_axis)
    h_params%E_axis = h_params%E_axis*C_E

    dset = "/fRE_E"
    call load_array_from_hdf5(h5file_id,dset,h_params%fRE_E)

    dset = "/fRE_pitch"
    call load_array_from_hdf5(h5file_id,dset,h_params%fRE_pitch)

    call h5fclose_f(h5file_id, h5error)
    if (h5error .EQ. -1) then
       write(6,'("KORC ERROR: Something went wrong in: load_data_from_hdf5 (korc_experimental) --> h5fclose_f")')
    end if
  END SUBROUTINE load_data_from_hdf5


  FUNCTION fRE_H(eta,g)
    REAL(rp), INTENT(IN) 	:: eta ! pitch angle in degrees
    REAL(rp), INTENT(IN) 	:: g ! Relativistic gamma factor
    REAL(rp) 				:: fRE_H
    REAL(rp) 				:: D
    REAL(rp) 				:: g0
    REAL(rp) 				:: g1
    REAL(rp) 				:: f0
    REAL(rp) 				:: f1
    REAL(rp) 				:: m
    REAL(rp) 				:: feta
    REAL(rp) 				:: A
    INTEGER 				:: index

    index = MINLOC(ABS(h_params%g - g),1)
    ! index of gamma supplied to function in Hollmann input gamma range
    D = h_params%g(index) - g

    ! linear interpolation of Hollmann input gamma range to gamma supplied
    ! to function
    if (D.GT.0) then
       f0 = h_params%fRE_E(index-1)
       g0 = h_params%g(index-1)

       f1 = h_params%fRE_E(index)
       g1 = h_params%g(index)
    else
       f0 = h_params%fRE_E(index)
       g0 = h_params%g(index)

       f1 = h_params%fRE_E(index+1)
       g1 = h_params%g(index+1)
    end if

    m = (f1-f0)/(g1-g0)

    fRE_H = f0 + m*(g - g0)
    ! end of linear interpolation, fRE_H is evaluation of input Hollmann energy
    ! distribution PDF at gamma supplied to function

    A = (2.0_rp*h_params%E/(h_params%Zeff + 1.0_rp))*(g**2 - 1.0_rp)/g
    A = A*h_params%A_fact

    feta = A*EXP(-A*(1.0_rp - COS(deg2rad(eta))))/(1.0_rp - EXP(-2.0_rp*A))     ! MRC
    !	feta = 0.5_rp*A*EXP(A*COS(deg2rad(eta)))/SINH(A)                            ! MRC

    fRE_H = fRE_H*feta
  END FUNCTION fRE_H

  FUNCTION fRE_H_3D(F,eta,g,R,Z,R0,Z0)
    TYPE(FIELDS), INTENT(IN)    :: F
    REAL(rp), INTENT(IN) 	:: eta ! pitch angle in degrees
    REAL(rp), INTENT(IN) 	:: g ! Relativistic gamma factor
    REAL(rp), INTENT(IN)  :: R,Z,R0,Z0
    REAL(rp) 				:: fRE_H_3D
    REAL(rp) 				:: D
    REAL(rp) 				:: g0
    REAL(rp) 				:: g1
    REAL(rp) 				:: f0
    REAL(rp) 				:: f1
    REAL(rp) 				:: m
    REAL(rp) 				:: feta
    REAL(rp) 				:: A
    REAL(rp) 				:: rm,E_G,Z_G
    INTEGER 				:: index

    index = MINLOC(ABS(h_params%g - g),1)
    ! index of gamma supplied to function in Hollmann input gamma range
    D = h_params%g(index) - g

    ! linear interpolation of Hollmann input gamma range to gamma supplied
    ! to function
    if (D.GT.0) then
       f0 = h_params%fRE_E(index-1)
       g0 = h_params%g(index-1)

       f1 = h_params%fRE_E(index)
       g1 = h_params%g(index)
    else
       f0 = h_params%fRE_E(index)
       g0 = h_params%g(index)

       f1 = h_params%fRE_E(index+1)
       g1 = h_params%g(index+1)
    end if

    m = (f1-f0)/(g1-g0)

    fRE_H_3D = f0 + m*(g - g0)
    ! end of linear interpolation, fRE_H is evaluation of input Hollman energy
    ! distribution PDF at gamma supplied to function

    rm=sqrt((R-R0)**2+(Z-Z0)**2)

    E_G=F%Ro*h_params%Eo/R

!    E_G=h_params%E*exp(-(rm/h_params%sigma_E)**2/2)
    Z_G=h_params%Zeff*exp(-(rm/h_params%sigma_Z)**2/2)

!    write(6,'("rm: ",E17.10)') rm
    
    A = (2.0_rp*E_G/(Z_G + 1.0_rp))*(g**2 - 1.0_rp)/g
    A = A*h_params%A_fact

    feta = A*EXP(-A*(1.0_rp - COS(deg2rad(eta))))/(1.0_rp - EXP(-2.0_rp*A))     ! MRC
    !	feta = 0.5_rp*A*EXP(A*COS(deg2rad(eta)))/SINH(A)                            ! MRC

    fRE_H_3D = fRE_H_3D*feta
  END FUNCTION fRE_H_3D

  FUNCTION fRE_HxPR(eta,g)
    REAL(rp), INTENT(IN) :: eta ! pitch angle in degrees
    REAL(rp), INTENT(IN) :: g ! gamma factor
    REAL(rp) :: fRE_HxPR

    fRE_HxPR = fRE_H(eta,g)*PR(eta,SQRT(g**2 - 1.0_rp),h_params%Bo,h_params%lambda)
  END FUNCTION fRE_HxPR


  FUNCTION fRE_pitch(g)
    REAL(rp), INTENT(IN) :: g ! Relativistic gamma factor
    REAL(rp) :: fRE_pitch
    REAL(rp) :: D
    REAL(rp) :: g0,g1,f0,f1,m
    INTEGER :: index

    index = MINLOC(ABS(h_params%g - g),1)
    D = h_params%g(index) - g

    if (D.GT.0) then
       f0 = h_params%fRE_pitch(index-1)
       g0 = h_params%g(index-1)

       f1 = h_params%fRE_pitch(index)
       g1 = h_params%g(index)
    else
       f0 = h_params%fRE_pitch(index)
       g0 = h_params%g(index)

       f1 = h_params%fRE_pitch(index+1)
       g1 = h_params%g(index+1)
    end if

    m = (f1-f0)/(g1-g0)

    fRE_pitch = f0 + m*(g - g0)
    fRE_pitch = 180.0_rp - fRE_pitch
  END FUNCTION fRE_pitch


  SUBROUTINE sample_Hollmann_distribution(params,spp)
    TYPE(KORC_PARAMS), INTENT(IN) 			:: params
    TYPE(SPECIES), INTENT(INOUT) 		:: spp
!    REAL(rp), DIMENSION(:), ALLOCATABLE, INTENT(INOUT) 	:: g
!    REAL(rp), DIMENSION(:), ALLOCATABLE, INTENT(INOUT) 	:: eta
!    REAL(rp), INTENT(OUT) 				:: go
!    REAL(rp), INTENT(OUT) 				:: etao
    REAL(rp), DIMENSION(:), ALLOCATABLE 			:: p
    REAL(rp) 						:: g_buffer
    REAL(rp) 						:: g_test
    REAL(rp) 						:: eta_buffer
    REAL(rp) 						:: eta_test
    REAL(rp) 						:: ratio
    REAL(rp) 						:: rand_unif
    REAL(rp), DIMENSION(:), ALLOCATABLE 			:: g_samples
    REAL(rp), DIMENSION(:), ALLOCATABLE 			:: eta_samples
    REAL(rp), DIMENSION(:), ALLOCATABLE 			:: g_tmp
    REAL(rp), DIMENSION(:), ALLOCATABLE 			:: eta_tmp
    REAL(rp) 						:: minmax
    REAL(rp) 						:: min_g
    REAL(rp) 						:: max_g
    REAL(rp) 						:: min_pitch_angle
    REAL(rp) 						:: max_pitch_angle
    REAL(rp) 						:: dg
    REAL(rp) 						:: deta
    LOGICAL 						:: lp
    INTEGER 						:: index_i
    INTEGER 						:: index_f
    INTEGER 						:: num_accepted
    INTEGER 						:: ii
    INTEGER 						:: jj
    INTEGER 						:: ppp
    INTEGER 						:: nsamples
    INTEGER 						:: mpierr
    INTEGER,DIMENSION(33) :: seed=(/1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1/)
    
    nsamples = spp%ppp*params%mpi_params%nmpi

    index_i = MINLOC(ABS(h_params%g - h_params%min_sampling_g),1)
    !index of minimum gamma range desired
    index_f = MINLOC(ABS(h_params%g - h_params%max_sampling_g),1)
    !index of maximum gamma range desired
    
    deta = (h_params%max_pitch_angle - h_params%min_pitch_angle)/100.0_rp
    dg = (h_params%max_sampling_g - h_params%min_sampling_g)/100.0_rp

    ! buffer at minimum gamma boundary  
    do jj=1_idef,INT(minmax_buffer_size,idef)
       minmax = h_params%min_sampling_g - REAL(jj,rp)*dg
       if (minmax.GT.h_params%min_g) then
          min_g = minmax
       end if
       ! buffer at maximum gamma boundary  
       minmax = h_params%max_sampling_g + REAL(jj,rp)*dg
       if (minmax.LT.h_params%max_g) then
          max_g = minmax
       end if
    end do

    ! buffer at minimum pitch angle boundary  
    if (h_params%min_pitch_angle.GE.korc_zero) then
       do jj=1_idef,INT(minmax_buffer_size,idef)
          minmax = h_params%min_pitch_angle -  REAL(jj,rp)*deta
          if (minmax.GT.0.0_rp) then
             min_pitch_angle = minmax
          end if
       end do
    else
       min_pitch_angle = 0.0_rp
    end if

    ! buffer at maximum pitch angle boundary  
    do jj=1_idef,INT(minmax_buffer_size,idef)
       minmax = h_params%max_pitch_angle + REAL(jj,rp)*deta
       if (minmax.LE.90.0_rp) then
          max_pitch_angle = minmax
       else
          max_pitch_angle = h_params%max_pitch_angle
          EXIT
       end if
    end do


    if (params%mpi_params%rank.EQ.0_idef) then
       !! MCMC and MH algorithm perfomred on single MPI process 
       !! to sample distribution function fRE_H
       ALLOCATE(g_samples(nsamples))
       ! Number of samples to distribute among all MPI processes
       ALLOCATE(eta_samples(nsamples))
       ! Number of samples to distribute among all MPI processes
       ALLOCATE(g_tmp(nsamples))
       ! Number of samples to distribute among all MPI processes
       ALLOCATE(eta_tmp(nsamples))
       ! Number of samples to distribute among all MPI processes


       !Transient!

       if (.not.params%SameRandSeed) then
          call init_random_seed()
       else
          call random_seed(put=seed)
       end if

       call RANDOM_NUMBER(rand_unif)
!       rand_unif=get_random_U()
       eta_buffer = h_params%min_pitch_angle + (h_params%max_pitch_angle &
            - h_params%min_pitch_angle)*rand_unif

       call RANDOM_NUMBER(rand_unif)
!       rand_unif=get_random_U()
       g_buffer = h_params%min_sampling_g + (h_params%max_sampling_g - &
            h_params%min_sampling_g)*rand_unif

       ii=2_idef
       do while (ii .LE. 1000_idef)
          eta_test = eta_buffer + random_norm(0.0_rp,spp%dth)
!          eta_test = eta_buffer + get_random_N()*spp%dth
          do while ((ABS(eta_test) .GT. h_params%max_pitch_angle).OR. &
               (ABS(eta_test) .LT. h_params%min_pitch_angle))
             eta_test = eta_buffer + random_norm(0.0_rp,spp%dth)
!             eta_test = eta_buffer + get_random_N()*spp%dth
          end do

          g_test = g_buffer + random_norm(0.0_rp,spp%dgam)
!          g_test = g_buffer + get_random_N()*spp%dgam
          do while ((g_test.LT.h_params%min_sampling_g).OR. &
               (g_test.GT.h_params%max_sampling_g))
             g_test = g_buffer + random_norm(0.0_rp,spp%dgam)
!             g_test = g_buffer + get_random_N()*spp%dgam
          end do

          ratio = fRE_H(eta_test,g_test)*sin(deg2rad(eta_test))/ &
               (fRE_H(eta_buffer,g_buffer)* &
                  sin(deg2rad(eta_buffer)))
          !ratio = fRE_H(eta_test,g_test)/fRE_H(eta_buffer,g_buffer)
          !ratio = fRE_HxPR(eta_test,g_test)/fRE_HxPR(eta_buffer,g_buffer)

          if (ratio .GE. 1.0_rp) then
             g_buffer = g_test
             eta_buffer = eta_test
             ii = ii + 1_idef
          else
             call RANDOM_NUMBER(rand_unif)
!             rand_unif=get_random_U()
             if (rand_unif .LT. ratio) then
                g_buffer = g_test
                eta_buffer = eta_test
                ii = ii + 1_idef
             end if
          end if
       end do

       !Transient!

       eta_tmp(1) = eta_buffer
       g_tmp(1) = g_buffer

       num_accepted = 0_idef
       do while(num_accepted.LT.nsamples)
          ii=2_idef
          do while (ii .LE. nsamples)

             if (modulo(ii,nsamples/10).eq.0) then
                write(6,'("Sample: ",I10)') ii
             end if
             
!             write(6,'("iisample",I16)') ii
             eta_test = eta_tmp(ii-1) + random_norm(0.0_rp,spp%dth)
             !eta_test = eta_tmp(ii-1) + get_random_N()*spp%dth
!             write(6,'("max_pitch_angle: ",E17.10)') max_pitch_angle
!             write(6,'("min_pitch_angle: ",E17.10)') min_pitch_angle
             do while ((ABS(eta_test) .GT. max_pitch_angle).OR. &
                  (ABS(eta_test) .LT. min_pitch_angle))
                eta_test = eta_tmp(ii-1) + random_norm(0.0_rp,spp%dth)
!                eta_test = eta_tmp(ii-1) + get_random_N()*spp%dth
!                write(6,'("eta_test: ",E17.10)') eta_test
             end do

             g_test = g_tmp(ii-1) + random_norm(0.0_rp,spp%dgam)
             !g_test = g_tmp(ii-1) + get_random_N()*spp%dgam

!             write(6,'("max_g: ",E17.10)') max_g
!             write(6,'("min_g: ",E17.10)') min_g
             do while ((g_test.LT.min_g).OR.(g_test.GT.max_g))
                g_test = g_tmp(ii-1) + random_norm(0.0_rp,spp%dgam)
!                g_test = g_tmp(ii-1) + get_random_N()*spp%dgam
!                write(6,'("g_test: ",E17.10)') g_test
             end do

             ratio = fRE_H(eta_test,g_test)*sin(deg2rad(eta_test))/ &
                  (fRE_H(eta_tmp(ii-1),g_tmp(ii-1))* &
                  sin(deg2rad(eta_tmp(ii-1))))
!             ratio = fRE_H(eta_test,g_test)/fRE_H(eta_tmp(ii-1),g_tmp(ii-1))
             !ratio = fRE_HxPR(eta_test,g_test)/fRE_HxPR(eta_tmp(ii-1),g_tmp(ii-1))
!             write(6,'("ratio: ",E17.10)') ratio

             if (ratio .GE. 1.0_rp) then
                g_tmp(ii) = g_test
                eta_tmp(ii) = eta_test
                ii = ii + 1_idef
             else
                call RANDOM_NUMBER(rand_unif)
!                rand_unif=get_random_U()
                if (rand_unif .LT. ratio) then
                   g_tmp(ii) = g_test
                   eta_tmp(ii) = eta_test
                   ii = ii + 1_idef
                end if
             end if
          end do

          eta_tmp = ABS(eta_tmp)

          ii = 1_idef
          do while ( (ii.LT.nsamples).AND.(num_accepted.LT.nsamples) )
!             write(6,'("iiaccept",I16)') ii
             lp = (g_tmp(ii).LE.h_params%max_sampling_g).AND. &
                  (g_tmp(ii).GE.h_params%min_sampling_g).AND. &
                  (eta_tmp(ii).LE.h_params%max_pitch_angle).AND. &
                  (eta_tmp(ii).GE.h_params%min_pitch_angle)             
             if (lp) then
                num_accepted = num_accepted + 1_idef
                g_samples(num_accepted) = g_tmp(ii)
                eta_samples(num_accepted) = eta_tmp(ii)
             end if
             ii = ii + 1_idef
          end do
       end do


      !		if (TRIM(h_params%current_direction) .EQ. 'ANTICLOCKWISE') then
      !			eta_samples = 180.0_rp - eta_samples
      !		end if

!       go = SUM(g_samples)/nsamples
!       etao = SUM(eta_samples)/nsamples
    end if !MCMC computed on single MPI process

    CALL MPI_SCATTER(g_samples,spp%ppp,MPI_REAL8,spp%vars%g,spp%ppp,MPI_REAL8, &
         0,MPI_COMM_WORLD,mpierr)

    CALL MPI_SCATTER(eta_samples,spp%ppp,MPI_REAL8,spp%vars%eta,spp%ppp,MPI_REAL8, &
         0,MPI_COMM_WORLD,mpierr)

!    CALL MPI_BCAST(go,1,MPI_REAL8,0,MPI_COMM_WORLD,mpierr)

!    CALL MPI_BCAST(etao,1,MPI_REAL8,0,MPI_COMM_WORLD,mpierr)

    call MPI_BARRIER(MPI_COMM_WORLD,mpierr)

    if (params%mpi_params%rank.EQ.0_idef) then
       DEALLOCATE(g_samples)
       DEALLOCATE(eta_samples)
       DEALLOCATE(g_tmp)
       DEALLOCATE(eta_tmp)
    end if

 !   write(6,'("sampled eta: ",E17.10)') eta
    
  END SUBROUTINE sample_Hollmann_distribution

FUNCTION PSI_ROT_exp(R,R0,sigR,Z,Z0,sigZ,theta)
  REAL(rp), INTENT(IN) 	:: R
  !! R-coordinate of MH sampled location
  REAL(rp), INTENT(IN) 	:: R0
  !! R-coordinate of center of 2D Gaussian
  REAL(rp), INTENT(IN) 	:: sigR
  !! Variance of first dimension of 2D Gaussian
  REAL(rp), INTENT(IN) 	:: Z
  !! Z-coordinate of MH sampled location
  REAL(rp), INTENT(IN) 	:: Z0
  !! Z-coordinate of center of 2D Gaussian
  REAL(rp), INTENT(IN) 	:: sigZ
  !! Variance of second dimension of 2D Gaussian
  REAL(rp), INTENT(IN) 	:: theta
  !! Angle of counter-clockwise rotation (in radians), of 2D Gaussian
  !! distribution relative to R,Z
  REAL(rp) 		:: PSI_ROT_exp
  !! Argument of exponential comprising 2D Gaussian distribution 

  PSI_ROT_exp=(R-R0)**2*((cos(theta))**2/(2*sigR**2)+ &
       (sin(theta))**2/(2*sigZ**2))+ &
       2*(R-R0)*(Z-Z0)*cos(theta)*sin(theta)*(1/(2*sigR**2)-1/(2*sigZ**2))+ &
       (Z-Z0)**2*((sin(theta))**2/(2*sigR**2)+(cos(theta))**2/(2*sigZ**2))
  
END FUNCTION PSI_ROT_exp


FUNCTION indicator_exp(psi,psi_max)
  REAL(rp), INTENT(IN)  :: psi
  REAL(rp), INTENT(IN)  :: psi_max
  REAL(rp)              :: indicator_exp

  IF (psi.LT.psi_max) THEN
     indicator_exp=1
  ELSE
     indicator_exp=0
  END IF
  
END FUNCTION indicator_exp
  
subroutine sample_Hollmann_distribution_3D(params,spp,F)
  !! @note Subroutine that generates a 2D Gaussian distribution in an 
  !! elliptic torus as the initial spatial condition of a given particle 
  !! species in the simulation. @endnote
  TYPE(KORC_PARAMS), INTENT(IN) 	:: params
  !! Core KORC simulation parameters.
  TYPE(SPECIES), INTENT(INOUT) 		:: spp
  !! An instance of the derived type SPECIES containing all the parameters
  !! and simulation variables of the different species in the simulation.
  TYPE(FIELDS), INTENT(IN)                                   :: F
  !! An instance of the KORC derived type FIELDS.
  REAL(rp), DIMENSION(:), ALLOCATABLE 	:: R_samples,X_samples,Y_samples
  !! Major radial location of all samples
  REAL(rp), DIMENSION(:), ALLOCATABLE 	:: PHI_samples
  !! Azimuithal angle of all samples
  REAL(rp), DIMENSION(:), ALLOCATABLE 	:: Z_samples
  !! Vertical location of all samples

  REAL(rp), DIMENSION(:), ALLOCATABLE 	:: G_samples
  !! Gamma of all samples
  REAL(rp), DIMENSION(:), ALLOCATABLE 	:: eta_samples
  !! Pitch angle of all samples

  REAL(rp) 				:: psi_max_buff
  !! Value of buffer above desired maximum argument of 2D Gaussian spatial
  !! profile
  REAL(rp) 				:: minmax
  !! Temporary variable used for setting buffers

  !! Minimum domain for momentum sampling including buffer
  REAL(rp) 				:: max_pitch_angle
  !! Maximum domain for pitch angle sampling including buffer
  REAL(rp) 				:: min_pitch_angle
  !! Minimum domain for pitch angle sampling including buffer
  REAL(rp) 				:: min_g,max_g
  REAL(rp) 				:: theta_rad
  !! Angle of rotation of 2D Gaussian spatial distribution in radians
  REAL(rp) 				:: R_buffer
  !! Previous sample of R location
  REAL(rp) 				:: Z_buffer
  !! Previous sample of Z location
 
  REAL(rp) 				:: eta_buffer
  !! Previous sample of pitch
  REAL(rp) 				:: G_buffer
  REAL(rp) 				:: R_test
  !! Present sample of R location
  REAL(rp) 				:: Z_test
  !! Present sample of Z location

  REAL(rp) 				:: eta_test
  !! Present sample of pitch angle
  REAL(rp) 				:: G_test
  REAL(rp) 				:: psi0
  !! Previous value of 2D Gaussian argument based on R_buffer, Z_buffer
  REAL(rp) 				:: psi1
  !! Present value of 2D Gaussian argument based on R_test, Z_test
  REAL(rp) 				:: f0
  !! Evaluation of Avalanche distribution with previous sample
  REAL(rp) 				:: f1
  !! Evaluation of Avalanche distribution with present sample
  REAL(rp) 				:: rand_unif
  !! Uniform random variable [0,1]
  REAL(rp) 				:: ratio
  !! MH selection criteria
  INTEGER				:: nsamples
  !! Total number of samples to be distributed over all mpi processes
  INTEGER 				:: ii
  !! Sample iterator.
  INTEGER 				:: mpierr
  !! mpi error indicator
  REAL(rp) 						:: dg,deta
  LOGICAL :: accepted
  INTEGER,DIMENSION(33) :: seed=(/1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1/)
  
  
  nsamples = spp%ppp*params%mpi_params%nmpi

  psi_max_buff = spp%psi_max*2._rp

  theta_rad=C_PI*spp%theta_gauss/180.0_rp


  deta = (h_params%max_pitch_angle - h_params%min_pitch_angle)/100.0_rp
  dg = (h_params%max_sampling_g - h_params%min_sampling_g)/100.0_rp
  
  ! buffer at minimum gamma boundary  
  do ii=1_idef,INT(minmax_buffer_size,idef)
     minmax = h_params%min_sampling_g - REAL(ii,rp)*dg
     if (minmax.GT.h_params%min_g) then
        min_g = minmax
     end if
     ! buffer at maximum gamma boundary  
     minmax = h_params%max_sampling_g + REAL(ii,rp)*dg
     if (minmax.LT.h_params%max_g) then
        max_g = minmax
     end if
  end do

  ! buffer at minimum pitch angle boundary  
  if (h_params%min_pitch_angle.GE.korc_zero) then
     do ii=1_idef,INT(minmax_buffer_size,idef)
        minmax = h_params%min_pitch_angle -  REAL(ii,rp)*deta
        if (minmax.GT.0.0_rp) then
           min_pitch_angle = minmax
        end if
     end do
  else
     min_pitch_angle = h_params%min_pitch_angle 
  end if

  ! buffer at maximum pitch angle boundary  
  do ii=1_idef,INT(minmax_buffer_size,idef)
     minmax = h_params%max_pitch_angle + REAL(ii,rp)*deta
     if (minmax.LE.180.0_rp) then
        max_pitch_angle = minmax
     end if
  end do

  
  if (params%mpi_params%rank.EQ.0_idef) then
     ALLOCATE(R_samples(nsamples))
     ALLOCATE(X_samples(nsamples))
     ALLOCATE(Y_samples(nsamples))
     ! Number of samples to distribute among all MPI processes
     ALLOCATE(PHI_samples(nsamples))
     ! Number of samples to distribute among all MPI processes
     ALLOCATE(Z_samples(nsamples))
     ! Number of samples to distribute among all MPI processes
     ALLOCATE(eta_samples(nsamples))
     ! Number of samples to distribute among all MPI processes
     ALLOCATE(G_samples(nsamples))
     ! Number of samples to distribute among all MPI processes
     
     ! Transient !

     R_buffer = spp%Ro
     Z_buffer = spp%Zo


     if (.not.params%SameRandSeed) then
        call init_random_seed()
     else
        call random_seed(put=seed)
     end if
     
!     call RANDOM_NUMBER(rand_unif)
!     eta_buffer = min_pitch_angle + (max_pitch_angle &
!          - min_pitch_angle)*rand_unif
!     eta_buffer = min_pitch_angle + (max_pitch_angle &
!          - min_pitch_angle)*get_random_mkl_U()
     eta_buffer = min_pitch_angle + (max_pitch_angle &
          - min_pitch_angle)*get_random_U()
     
!     call RANDOM_NUMBER(rand_unif)
!     G_buffer = min_g + (max_g - min_g)*rand_unif
!     G_buffer = min_g + (max_g - min_g)*get_random_mkl_U()
     G_buffer = min_g + (max_g - min_g)*get_random_U()
     
!     write(6,*) 'R_buffer',R_buffer
!     write(6,*) 'Z_buffer',Z_buffer
!     write(6,*) 'eta_buffer',eta_buffer
!     write(6,*) 'G_buffer',G_buffer
     
     !     write(6,'("length norm: ",E17.10)') params%cpp%length
     
     accepted=.false.
     ii=1_idef
     do while (ii .LE. 1000_idef)

!        write(6,'("burn:",I15)') ii
        
        !R_test = R_buffer + random_norm(0.0_rp,spp%dR)
        !R_test = R_buffer + get_random_mkl_N(0.0_rp,spp%dR)
        R_test = R_buffer + get_random_N()*spp%dR
        
        !Z_test = Z_buffer + random_norm(0.0_rp,spp%dZ)
        !Z_test = Z_buffer + get_random_mkl_N(0.0_rp,spp%dZ)
        Z_test = Z_buffer + get_random_N()*spp%dZ
        
        !eta_test = eta_buffer + random_norm(0.0_rp,spp%dth)
        !eta_test = eta_buffer + get_random_mkl_N(0.0_rp,spp%dth)
        eta_test = eta_buffer + get_random_N()*spp%dth
        
        !G_test = G_buffer + random_norm(0.0_rp,spp%dgam)
        !G_test = G_buffer + get_random_mkl_N(0.0_rp,spp%dgam)
        G_test = G_buffer + get_random_N()*spp%dgam


        ! Test that pitch angle and momentum are within chosen boundary
        do while ((ABS(eta_test) .GT. max_pitch_angle).OR. &
             (ABS(eta_test) .LT. min_pitch_angle))
           !eta_test = eta_buffer + random_norm(0.0_rp,spp%dth)
           !eta_test = eta_buffer + get_random_mkl_N(0.0_rp,spp%dth)
           eta_test = eta_buffer + get_random_N()*spp%dth
        end do

        do while ((G_test.LT.min_g).OR.(G_test.GT.max_g))
           !G_test = G_buffer + random_norm(0.0_rp,spp%dgam)
           !G_test = G_buffer + get_random_mkl_N(0.0_rp,spp%dgam)
           G_test = G_buffer + get_random_N()*spp%dgam
        end do
        
        ! initialize 2D gaussian argument and distribution function, or
        ! copy from previous sample
        if (ii==1) then
           psi0=PSI_ROT_exp(R_buffer,spp%Ro,spp%sigmaR,Z_buffer,spp%Zo, &
                spp%sigmaZ,theta_rad)
           
           f0=fRE_H_3D(F,eta_buffer,G_buffer,R_buffer,Z_buffer,spp%Ro,spp%Zo)
!           f0=fRE_H(eta_buffer,G_buffer)
        end if

        if (accepted) then
           psi0=psi1
           f0=f1
        end if
        
        psi1=PSI_ROT_exp(R_test,spp%Ro,spp%sigmaR,Z_test,spp%Zo, &
             spp%sigmaZ,theta_rad)       
        
                
        f1=fRE_H_3D(F,eta_test,G_test,R_test,Z_test,spp%Ro,spp%Zo)    
!        f1=fRE_H(eta_test,G_test)
        
!        write(6,'("psi0: ",E17.10)') psi0
!        write(6,'("psi1: ",E17.10)') psi1

!        write(6,'("f0: ",E17.10)') f0
!        write(6,'("f1: ",E17.10)') f1

        
        ! Calculate acceptance ratio for MH algorithm. fRE function
        ! incorporates p^2 factor of spherical coordinate Jacobian
        ! for velocity phase space, factors of sin(pitch angle) for velocity
        ! phase space and cylindrical coordinate Jacobian R for spatial
        ! phase space incorporated here.
        ratio = indicator_exp(psi1,spp%psi_max)* &
             R_test*f1*sin(deg2rad(eta_test))/ &
             (R_buffer*f0*sin(deg2rad(eta_buffer)))
!        ratio = indicator_exp(psi1,spp%psi_max)* &
!             R_test*EXP(-psi1)*f1*sin(deg2rad(eta_test))/ &
!             (R_buffer*EXP(-psi0)*f0*sin(deg2rad(eta_buffer)))

!        ratio = f1*sin(deg2rad(eta_test))/(f0*sin(deg2rad(eta_buffer)))

        accepted=.false.
        if (ratio .GE. 1.0_rp) then
           accepted=.true.
           R_buffer = R_test
           Z_buffer = Z_test
           eta_buffer = eta_test
           G_buffer = G_test
           ii = ii + 1_idef
        else
!           call RANDOM_NUMBER(rand_unif)
!           if (rand_unif .LT. ratio) then
           !if (get_random_mkl_U() .LT. ratio) then
           if (get_random_U() .LT. ratio) then
              accepted=.true.
              R_buffer = R_test
              Z_buffer = Z_test
              eta_buffer = eta_test
              G_buffer = G_test
              ii = ii + 1_idef
           end if
        end if
     end do
     ! Transient !

     ii=1_idef
     do while (ii .LE. nsamples)

!        write(6,'("sample:",I15)') ii
        
       if (modulo(ii,nsamples/10).eq.0) then
           write(6,'("Sample: ",I10)') ii
        end if
        
        !R_test = R_buffer + random_norm(0.0_rp,spp%dR)
        !R_test = R_buffer + get_random_mkl_N(0.0_rp,spp%dR)
        R_test = R_buffer + get_random_N()*spp%dR
        
        !Z_test = Z_buffer + random_norm(0.0_rp,spp%dZ)
        !Z_test = Z_buffer + get_random_mkl_N(0.0_rp,spp%dZ)
        Z_test = Z_buffer + get_random_N()*spp%dZ
        
        !eta_test = eta_buffer + random_norm(0.0_rp,spp%dth)
        !eta_test = eta_buffer + get_random_mkl_N(0.0_rp,spp%dth)
        eta_test = eta_buffer + get_random_N()*spp%dth
        
        !G_test = G_buffer + random_norm(0.0_rp,spp%dgam)
        !G_test = G_buffer + get_random_mkl_N(0.0_rp,spp%dgam)
        G_test = G_buffer + get_random_N()*spp%dgam


        ! Test that pitch angle and momentum are within chosen boundary
        do while ((ABS(eta_test) .GT. max_pitch_angle).OR. &
             (ABS(eta_test) .LT. min_pitch_angle))
           !eta_test = eta_buffer + random_norm(0.0_rp,spp%dth)
           !eta_test = eta_buffer + get_random_mkl_N(0.0_rp,spp%dth)
           eta_test = eta_buffer + get_random_N()*spp%dth
        end do

        do while ((G_test.LT.min_g).OR.(G_test.GT.max_g))
           !G_test = G_buffer + random_norm(0.0_rp,spp%dgam)
           !G_test = G_buffer + get_random_mkl_N(0.0_rp,spp%dgam)
           G_test = G_buffer + get_random_N()*spp%dgam
        end do

        if (accepted) then
           psi0=psi1
           f0=f1
        end if
        
        psi1=PSI_ROT_exp(R_test,spp%Ro,spp%sigmaR,Z_test,spp%Zo, &
             spp%sigmaZ,theta_rad)

!        write(6,'("R: ",E17.10)') R_test
!        write(6,'("R0: ",E17.10)') spp%Ro
!        write(6,'("sigma_R: ",E17.10)') spp%sigmaR
!        write(6,'("dR: ",E17.10)') spp%dR
!        write(6,'("N_dR: ",E17.10)') random_norm(0.0_rp,spp%dR)
!        write(6,'("Z: ",E17.10)') Z_test
!        write(6,'("Z0: ",E17.10)') spp%Zo
!        write(6,'("sigma_Z: ",E17.10)') spp%sigmaZ
!        write(6,'("dZ: ",E17.10)') spp%dZ
!        write(6,'("N_dR: ",Z17.10)') random_norm(0.0_rp,spp%dZ)
        
        f1=fRE_H_3D(F,eta_test,G_test,R_test,Z_test,spp%Ro,spp%Zo)            
!        f1=fRE_H(eta_test,G_test)
        
        ratio = indicator_exp(psi1,psi_max_buff)* &
             R_test*f1*sin(deg2rad(eta_test))/ &
             (R_buffer*f0*sin(deg2rad(eta_buffer)))
!        ratio = indicator_exp(psi1,psi_max_buff)* &
!             R_test*EXP(-psi1)*f1*sin(deg2rad(eta_test))/ &
!             (R_buffer*EXP(-psi0)*f0*sin(deg2rad(eta_buffer)))

!        ratio = f1*sin(deg2rad(eta_test))/(f0*sin(deg2rad(eta_buffer)))
        
        accepted=.false.
        if (ratio .GE. 1.0_rp) then
           accepted=.true.
           R_buffer = R_test
           Z_buffer = Z_test
           eta_buffer = eta_test
           G_buffer = G_test
        else
           !call RANDOM_NUMBER(rand_unif)
           !if (rand_unif .LT. ratio) then
           !if (get_random_mkl_U() .LT. ratio) then
           if (get_random_U() .LT. ratio) then
              accepted=.true.
              R_buffer = R_test
              Z_buffer = Z_test
              eta_buffer = eta_test
              G_buffer = G_test
           end if
        end if

!        write(6,'("R: ",E17.10)') R_buffer
!        write(6,'("Z: ",E17.10)') Z_buffer
        
        ! Only accept sample if it is within desired boundary, but
        ! add to MC above if within buffer. This helps make the boundary
        ! more defined.
        IF ((INT(indicator_exp(psi1,spp%psi_max)).EQ.1).AND. &
             (G_buffer.LE.h_params%max_sampling_g).AND. &
             (G_buffer.GE.h_params%min_sampling_g).AND. &
             (eta_buffer.LE.h_params%max_pitch_angle).AND. &
             (eta_buffer.GE.h_params%min_pitch_angle).AND. &
             ACCEPTED) THEN
           R_samples(ii) = R_buffer
           Z_samples(ii) = Z_buffer
           eta_samples(ii) = eta_buffer
           G_samples(ii) = G_buffer

!           write(6,*) 'RS',R_buffer
           
           ! Sample phi location uniformly
           !call RANDOM_NUMBER(rand_unif)
           !PHI_samples(ii) = 2.0_rp*C_PI*rand_unif
           !PHI_samples(ii) = 2.0_rp*C_PI*get_random_mkl_U()
           PHI_samples(ii) = 2.0_rp*C_PI*get_random_U()
           ii = ii + 1_idef 
        END IF
        
     end do

!  if (minval(R_samples(:)).lt.1._rp/params%cpp%length) stop 'error with sample'
!  write(6,'("R_sample: ",E17.10)') R_samples(:)*params%cpp%length

     X_samples=R_samples*cos(PHI_samples)
     Y_samples=R_samples*sin(PHI_samples)

!     write(6,*) 'R_samples',R_samples
!     write(6,*) 'PHI_samples',PHI_samples
!     write(6,*) 'Z_samples',Z_samples
!     write(6,*) 'G_samples',G_samples
!     write(6,*) 'eta_samples',eta_samples
     
  end if


  
  call MPI_BARRIER(MPI_COMM_WORLD,mpierr)


  CALL MPI_SCATTER(X_samples,spp%ppp,MPI_REAL8, &
       spp%vars%X(:,1),spp%ppp,MPI_REAL8,0,MPI_COMM_WORLD,mpierr)
  CALL MPI_SCATTER(Y_samples,spp%ppp,MPI_REAL8, &
       spp%vars%X(:,2),spp%ppp,MPI_REAL8,0,MPI_COMM_WORLD,mpierr)
  CALL MPI_SCATTER(Z_samples,spp%ppp,MPI_REAL8, &
       spp%vars%X(:,3),spp%ppp,MPI_REAL8,0,MPI_COMM_WORLD,mpierr)
  CALL MPI_SCATTER(eta_samples,spp%ppp,MPI_REAL8, &
       spp%vars%eta,spp%ppp,MPI_REAL8,0,MPI_COMM_WORLD,mpierr)
  CALL MPI_SCATTER(G_samples,spp%ppp,MPI_REAL8, &
       spp%vars%g,spp%ppp,MPI_REAL8,0,MPI_COMM_WORLD,mpierr)

  
  call MPI_BARRIER(MPI_COMM_WORLD,mpierr)

!  write(6,*) params%mpi_params%rank,'varX',spp%vars%X(:,1)
!  write(6,*) params%mpi_params%rank,'varY',spp%vars%X(:,2)
  
!  write(6,'("X_X: ",E17.10)') spp%vars%X(:,1)*params%cpp%length
  
  ! gamma is kept for each particle, not the momentum

  if (params%orbit_model(1:2).eq.'GC') call cart_to_cyl(spp%vars%X,spp%vars%Y)

!  write(6,*) params%mpi_params%rank,'varX',spp%vars%X(:,1)
!  write(6,*) params%mpi_params%rank,'varR',spp%vars%Y(:,1)
  

!  write(6,'("Y_R: ",E17.10)') spp%vars%Y(:,1)*params%cpp%length
!  write(6,'("Y_PHI: ",E17.10)') spp%vars%Y(:,1)*params%cpp%length
!  write(6,'("Y_Z: ",E17.10)') spp%vars%Y(:,3)*params%cpp%length
  
!  if (minval(spp%vars%Y(:,1)).lt.1._rp/params%cpp%length) stop 'error with avalanche'
  
  if (params%mpi_params%rank.EQ.0_idef) then
     DEALLOCATE(R_samples)
     DEALLOCATE(X_samples)
     DEALLOCATE(Y_samples)
     DEALLOCATE(Z_samples)
     DEALLOCATE(PHI_samples)
     DEALLOCATE(eta_samples)
     DEALLOCATE(G_samples)
  end if
  
  
end subroutine sample_Hollmann_distribution_3D

subroutine sample_Hollmann_distribution_3D_psi(params,spp,F)
  !! @note Subroutine that generates a 2D Gaussian distribution in an 
  !! elliptic torus as the initial spatial condition of a given particle 
  !! species in the simulation. @endnote
  TYPE(KORC_PARAMS), INTENT(INOUT) 	:: params
  !! Core KORC simulation parameters.
  TYPE(SPECIES), INTENT(INOUT) 		:: spp
  !! An instance of the derived type SPECIES containing all the parameters
  !! and simulation variables of the different species in the simulation.
  TYPE(FIELDS), INTENT(IN)                                   :: F
  !! An instance of the KORC derived type FIELDS.
  REAL(rp), DIMENSION(:), ALLOCATABLE 	:: R_samples,X_samples,Y_samples
  !! Major radial location of all samples
  REAL(rp), DIMENSION(:), ALLOCATABLE 	:: PHI_samples
  !! Azimuithal angle of all samples
  REAL(rp), DIMENSION(:), ALLOCATABLE 	:: Z_samples
  !! Vertical location of all samples

  REAL(rp), DIMENSION(:), ALLOCATABLE 	:: G_samples
  !! Gamma of all samples
  REAL(rp), DIMENSION(:), ALLOCATABLE 	:: eta_samples
  !! Pitch angle of all samples

  REAL(rp) 				:: psi_max_buff
  !! Value of buffer above desired maximum argument of 2D Gaussian spatial
  !! profile
  REAL(rp) 				:: minmax
  !! Temporary variable used for setting buffers

  !! Minimum domain for momentum sampling including buffer
  REAL(rp) 				:: max_pitch_angle
  !! Maximum domain for pitch angle sampling including buffer
  REAL(rp) 				:: min_pitch_angle
  !! Minimum domain for pitch angle sampling including buffer
  REAL(rp) 				:: min_g,max_g
  REAL(rp) 				:: min_R,max_R
  REAL(rp) 				:: min_Z,max_Z
  REAL(rp) 				:: theta_rad
  !! Angle of rotation of 2D Gaussian spatial distribution in radians
  REAL(rp) 				:: R_buffer
  !! Previous sample of R location
  REAL(rp) 				:: Z_buffer
  !! Previous sample of Z location
 
  REAL(rp) 				:: eta_buffer
  !! Previous sample of pitch
  REAL(rp) 				:: G_buffer
  REAL(rp) 				:: R_test
  !! Present sample of R location
  REAL(rp) 				:: Z_test
  !! Present sample of Z location

  REAL(rp) 				:: eta_test
  !! Present sample of pitch angle
  REAL(rp) 				:: G_test
  REAL(rp) 				:: psi0
  !! Previous value of 2D Gaussian argument based on R_buffer, Z_buffer
  REAL(rp) 				:: psi1
  !! Present value of 2D Gaussian argument based on R_test, Z_test
  REAL(rp)  :: PSIp_lim,PSIP0,PSIN,PSIN0,PSIN1,sigma
  REAL(rp) 				:: f0
  !! Evaluation of Avalanche distribution with previous sample
  REAL(rp) 				:: f1
  !! Evaluation of Avalanche distribution with present sample
  REAL(rp) 				:: rand_unif
  !! Uniform random variable [0,1]
  REAL(rp) 				:: ratio
  !! MH selection criteria
  INTEGER				:: nsamples
  !! Total number of samples to be distributed over all mpi processes
  INTEGER 				:: ii
  !! Sample iterator.
  INTEGER 				:: mpierr
  !! mpi error indicator
  REAL(rp) 						:: dg,deta
  LOGICAL :: accepted
  INTEGER,DIMENSION(33) :: seed=(/1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1/)
  
  
  nsamples = spp%ppp*params%mpi_params%nmpi

  psi_max_buff = spp%psi_max*1.25_rp

  theta_rad=C_PI*spp%theta_gauss/180.0_rp

  params%GC_coords=.TRUE.
  PSIp_lim=F%PSIp_lim
  PSIp0=F%PSIP_min

  min_R=minval(F%X%R)
  max_R=maxval(F%X%R)
  min_Z=minval(F%X%Z)
  max_Z=maxval(F%X%Z)

  sigma=spp%sigmaR*params%cpp%length
  
  !write(6,*) min_R,max_R
  !write(6,*) min_Z,max_Z
  
  deta = (h_params%max_pitch_angle - h_params%min_pitch_angle)/100.0_rp
  dg = (h_params%max_sampling_g - h_params%min_sampling_g)/100.0_rp
  
  ! buffer at minimum gamma boundary  
  do ii=1_idef,INT(minmax_buffer_size,idef)
     minmax = h_params%min_sampling_g - REAL(ii,rp)*dg
     if (minmax.GT.h_params%min_g) then
        min_g = minmax
     end if
     ! buffer at maximum gamma boundary  
     minmax = h_params%max_sampling_g + REAL(ii,rp)*dg
     if (minmax.LT.h_params%max_g) then
        max_g = minmax
     end if
  end do

  ! buffer at minimum pitch angle boundary  
  if (h_params%min_pitch_angle.GE.korc_zero) then
     do ii=1_idef,INT(minmax_buffer_size,idef)
        minmax = h_params%min_pitch_angle -  REAL(ii,rp)*deta
        if (minmax.GT.0.0_rp) then
           min_pitch_angle = minmax
        end if
     end do
  else
     min_pitch_angle = h_params%min_pitch_angle 
  end if

  ! buffer at maximum pitch angle boundary  
  do ii=1_idef,INT(minmax_buffer_size,idef)
     minmax = h_params%max_pitch_angle + REAL(ii,rp)*deta
     if (minmax.LE.180.0_rp) then
        max_pitch_angle = minmax
     end if
  end do

  
  if (params%mpi_params%rank.EQ.0_idef) then
     ALLOCATE(R_samples(nsamples))
     ALLOCATE(X_samples(nsamples))
     ALLOCATE(Y_samples(nsamples))
     ! Number of samples to distribute among all MPI processes
     ALLOCATE(PHI_samples(nsamples))
     ! Number of samples to distribute among all MPI processes
     ALLOCATE(Z_samples(nsamples))
     ! Number of samples to distribute among all MPI processes
     ALLOCATE(eta_samples(nsamples))
     ! Number of samples to distribute among all MPI processes
     ALLOCATE(G_samples(nsamples))
     ! Number of samples to distribute among all MPI processes
     
     ! Transient !

     R_buffer = spp%Ro
     Z_buffer = spp%Zo


     if (.not.params%SameRandSeed) then
        call init_random_seed()
     else
        call random_seed(put=seed)
     end if
     
!     call RANDOM_NUMBER(rand_unif)
!     eta_buffer = min_pitch_angle + (max_pitch_angle &
!          - min_pitch_angle)*rand_unif
!     eta_buffer = min_pitch_angle + (max_pitch_angle &
!          - min_pitch_angle)*get_random_mkl_U()
     eta_buffer = min_pitch_angle + (max_pitch_angle &
          - min_pitch_angle)*get_random_U()
     
!     call RANDOM_NUMBER(rand_unif)
!     G_buffer = min_g + (max_g - min_g)*rand_unif
!     G_buffer = min_g + (max_g - min_g)*get_random_mkl_U()
     G_buffer = min_g + (max_g - min_g)*get_random_U()
     
!     write(6,*) 'R_buffer',R_buffer
!     write(6,*) 'Z_buffer',Z_buffer
!     write(6,*) 'eta_buffer',eta_buffer
!     write(6,*) 'G_buffer',G_buffer
     
     !     write(6,'("length norm: ",E17.10)') params%cpp%length
     
     accepted=.false.
     ii=1_idef
     do while (ii .LE. 1000_idef)

        if (modulo(ii,100).eq.0) then
           write(6,'("Burn: ",I10)') ii
        end if
        
        !R_test = R_buffer + random_norm(0.0_rp,spp%dR)
        !R_test = R_buffer + get_random_mkl_N(0.0_rp,spp%dR)
        R_test = R_buffer + get_random_N()*spp%dR
        
        !Z_test = Z_buffer + random_norm(0.0_rp,spp%dZ)
        !Z_test = Z_buffer + get_random_mkl_N(0.0_rp,spp%dZ)
        Z_test = Z_buffer + get_random_N()*spp%dZ
        
        !eta_test = eta_buffer + random_norm(0.0_rp,spp%dth)
        !eta_test = eta_buffer + get_random_mkl_N(0.0_rp,spp%dth)
        eta_test = eta_buffer + get_random_N()*spp%dth
        
        !G_test = G_buffer + random_norm(0.0_rp,spp%dgam)
        !G_test = G_buffer + get_random_mkl_N(0.0_rp,spp%dgam)
        G_test = G_buffer + get_random_N()*spp%dgam


        ! Test that pitch angle and momentum are within chosen boundary
        do while ((ABS(eta_test) .GT. max_pitch_angle).OR. &
             (ABS(eta_test) .LT. min_pitch_angle))
           !eta_test = eta_buffer + random_norm(0.0_rp,spp%dth)
           !eta_test = eta_buffer + get_random_mkl_N(0.0_rp,spp%dth)
           eta_test = eta_buffer + get_random_N()*spp%dth
        end do

        do while ((R_test.GT.max_R).OR.(R_test .LT. min_R))
           !eta_test = eta_buffer + random_norm(0.0_rp,spp%dth)
           !eta_test = eta_buffer + get_random_mkl_N(0.0_rp,spp%dth)
           R_test = R_buffer + get_random_N()*spp%dR
        end do

        do while ((Z_test.GT.max_Z).OR.(Z_test .LT. min_Z))
           !eta_test = eta_buffer + random_norm(0.0_rp,spp%dth)
           !eta_test = eta_buffer + get_random_mkl_N(0.0_rp,spp%dth)
           Z_test = Z_buffer + get_random_N()*spp%dZ
        end do
        
        do while ((G_test.LT.min_g).OR.(G_test.GT.max_g))
           !G_test = G_buffer + random_norm(0.0_rp,spp%dgam)
           !G_test = G_buffer + get_random_mkl_N(0.0_rp,spp%dgam)
           G_test = G_buffer + get_random_N()*spp%dgam
        end do
        
        ! initialize 2D gaussian argument and distribution function, or
        ! copy from previous sample
        if (ii==1) then
!           psi0=PSI_ROT_exp(R_buffer,spp%Ro,spp%sigmaR,Z_buffer,spp%Zo, &
!                spp%sigmaZ,theta_rad)

           spp%vars%Y(1,1)=R_buffer
           spp%vars%Y(1,2)=0
           spp%vars%Y(1,3)=Z_buffer

           !write(6,*) 'R',R_buffer
           !write(6,*) 'Z',Z_buffer
           
           call get_fields(params,spp%vars,F)
           psi0=spp%vars%PSI_P(1)
           PSIN0=(psi0-PSIP0)/(PSIp_lim-PSIP0)
           
           f0=fRE_H_3D(F,eta_buffer,G_buffer,R_buffer,Z_buffer,spp%Ro,spp%Zo)
!           f0=fRE_H(eta_buffer,G_buffer)
        end if

        if (accepted) then
           !psi0=psi1
           PSIN0=PSIN1
           f0=f1
        end if
        
!        psi1=PSI_ROT_exp(R_test,spp%Ro,spp%sigmaR,Z_test,spp%Zo, &
        !             spp%sigmaZ,theta_rad)
        spp%vars%Y(1,1)=R_test
        spp%vars%Y(1,2)=0._rp
        spp%vars%Y(1,3)=Z_test

        call get_fields(params,spp%vars,F)
        psi1=spp%vars%PSI_P(1)
        PSIN1=(psi1-PSIP0)/(PSIp_lim-PSIP0)

!        write(6,*) 'R',R_test
!        write(6,*) 'Z',Z_test
!        write(6,*) 'PSI',psi1
!        write(6,*) 'PSIN',PSIN
                
        f1=fRE_H_3D(F,eta_test,G_test,R_test,Z_test,spp%Ro,spp%Zo)    
!        f1=fRE_H(eta_test,G_test)
        
!        write(6,'("psi0: ",E17.10)') psi0
!        write(6,'("psi1: ",E17.10)') psi1

!        write(6,'("f0: ",E17.10)') f0
!        write(6,'("f1: ",E17.10)') f1

        
        ! Calculate acceptance ratio for MH algorithm. fRE function
        ! incorporates p^2 factor of spherical coordinate Jacobian
        ! for velocity phase space, factors of sin(pitch angle) for velocity
        ! phase space and cylindrical coordinate Jacobian R for spatial
        ! phase space incorporated here.
!        ratio = indicator_exp(PSIN,spp%psi_max)* &
!             R_test*f1*sin(deg2rad(eta_test))/ &
!             (R_buffer*f0*sin(deg2rad(eta_buffer)))
        ratio = indicator_exp(PSIN1,spp%psi_max)* &
             R_test*EXP(-PSIN1/sigma)*f1*sin(deg2rad(eta_test))/ &
             (R_buffer*EXP(-PSIN0/sigma)*f0*sin(deg2rad(eta_buffer)))

!        ratio = f1*sin(deg2rad(eta_test))/(f0*sin(deg2rad(eta_buffer)))

        accepted=.false.
        if (ratio .GE. 1.0_rp) then
           accepted=.true.
           R_buffer = R_test
           Z_buffer = Z_test
           eta_buffer = eta_test
           G_buffer = G_test
           ii = ii + 1_idef
        else
!           call RANDOM_NUMBER(rand_unif)
!           if (rand_unif .LT. ratio) then
           !if (get_random_mkl_U() .LT. ratio) then
           if (get_random_U() .LT. ratio) then
              accepted=.true.
              R_buffer = R_test
              Z_buffer = Z_test
              eta_buffer = eta_test
              G_buffer = G_test
              ii = ii + 1_idef
           end if
        end if
     end do
     ! Transient !

     ii=1_idef
     do while (ii .LE. nsamples)

!        write(6,'("sample:",I15)') ii
        
       if (modulo(ii,nsamples/10).eq.0) then
           write(6,'("Sample: ",I10)') ii
        end if
        
        !R_test = R_buffer + random_norm(0.0_rp,spp%dR)
        !R_test = R_buffer + get_random_mkl_N(0.0_rp,spp%dR)
        R_test = R_buffer + get_random_N()*spp%dR
        
        !Z_test = Z_buffer + random_norm(0.0_rp,spp%dZ)
        !Z_test = Z_buffer + get_random_mkl_N(0.0_rp,spp%dZ)
        Z_test = Z_buffer + get_random_N()*spp%dZ
        
        !eta_test = eta_buffer + random_norm(0.0_rp,spp%dth)
        !eta_test = eta_buffer + get_random_mkl_N(0.0_rp,spp%dth)
        eta_test = eta_buffer + get_random_N()*spp%dth
        
        !G_test = G_buffer + random_norm(0.0_rp,spp%dgam)
        !G_test = G_buffer + get_random_mkl_N(0.0_rp,spp%dgam)
        G_test = G_buffer + get_random_N()*spp%dgam


        ! Test that pitch angle and momentum are within chosen boundary
        do while ((ABS(eta_test) .GT. max_pitch_angle).OR. &
             (ABS(eta_test) .LT. min_pitch_angle))
           !eta_test = eta_buffer + random_norm(0.0_rp,spp%dth)
           !eta_test = eta_buffer + get_random_mkl_N(0.0_rp,spp%dth)
           eta_test = eta_buffer + get_random_N()*spp%dth
        end do

        do while ((G_test.LT.min_g).OR.(G_test.GT.max_g))
           !G_test = G_buffer + random_norm(0.0_rp,spp%dgam)
           !G_test = G_buffer + get_random_mkl_N(0.0_rp,spp%dgam)
           G_test = G_buffer + get_random_N()*spp%dgam
        end do

        do while ((R_test.GT.max_R).OR.(R_test .LT. min_R))
           !eta_test = eta_buffer + random_norm(0.0_rp,spp%dth)
           !eta_test = eta_buffer + get_random_mkl_N(0.0_rp,spp%dth)
           R_test = R_buffer + get_random_N()*spp%dR
        end do

        do while ((Z_test.GT.max_Z).OR.(Z_test .LT. min_Z))
           !eta_test = eta_buffer + random_norm(0.0_rp,spp%dth)
           !eta_test = eta_buffer + get_random_mkl_N(0.0_rp,spp%dth)
           Z_test = Z_buffer + get_random_N()*spp%dZ
        end do
        
        if (accepted) then
           PSIN0=PSIN1
           f0=f1
        end if
        
!        psi1=PSI_ROT_exp(R_test,spp%Ro,spp%sigmaR,Z_test,spp%Zo, &
!             spp%sigmaZ,theta_rad)
        spp%vars%Y(1,1)=R_test
        spp%vars%Y(1,2)=0
        spp%vars%Y(1,3)=Z_test

        call get_fields(params,spp%vars,F)
        psi1=spp%vars%PSI_P(1)
        PSIN1=(psi1-PSIP0)/(PSIp_lim-PSIP0)

!        write(6,'("R: ",E17.10)') R_test
!        write(6,'("R0: ",E17.10)') spp%Ro
!        write(6,'("sigma_R: ",E17.10)') spp%sigmaR
!        write(6,'("dR: ",E17.10)') spp%dR
!        write(6,'("N_dR: ",E17.10)') random_norm(0.0_rp,spp%dR)
!        write(6,'("Z: ",E17.10)') Z_test
!        write(6,'("Z0: ",E17.10)') spp%Zo
!        write(6,'("sigma_Z: ",E17.10)') spp%sigmaZ
!        write(6,'("dZ: ",E17.10)') spp%dZ
!        write(6,'("N_dR: ",Z17.10)') random_norm(0.0_rp,spp%dZ)
        
        f1=fRE_H_3D(F,eta_test,G_test,R_test,Z_test,spp%Ro,spp%Zo)            
!        f1=fRE_H(eta_test,G_test)
        
!        ratio = indicator_exp(PSIN,psi_max_buff)* &
!             R_test*f1*sin(deg2rad(eta_test))/ &
!             (R_buffer*f0*sin(deg2rad(eta_buffer)))
        ratio = indicator_exp(PSIN1,psi_max_buff)* &
             R_test*EXP(-PSIN1/sigma)*f1*sin(deg2rad(eta_test))/ &
             (R_buffer*EXP(-PSIN0/sigma)*f0*sin(deg2rad(eta_buffer)))

!        ratio = f1*sin(deg2rad(eta_test))/(f0*sin(deg2rad(eta_buffer)))
        
        accepted=.false.
        if (ratio .GE. 1.0_rp) then
           accepted=.true.
           R_buffer = R_test
           Z_buffer = Z_test
           eta_buffer = eta_test
           G_buffer = G_test
        else
           !call RANDOM_NUMBER(rand_unif)
           !if (rand_unif .LT. ratio) then
           !if (get_random_mkl_U() .LT. ratio) then
           if (get_random_U() .LT. ratio) then
              accepted=.true.
              R_buffer = R_test
              Z_buffer = Z_test
              eta_buffer = eta_test
              G_buffer = G_test
           end if
        end if

!        write(6,'("R: ",E17.10)') R_buffer
!        write(6,'("Z: ",E17.10)') Z_buffer
        
        ! Only accept sample if it is within desired boundary, but
        ! add to MC above if within buffer. This helps make the boundary
        ! more defined.
        IF ((INT(indicator_exp(PSIN1,spp%psi_max)).EQ.1).AND. &
             (G_buffer.LE.h_params%max_sampling_g).AND. &
             (G_buffer.GE.h_params%min_sampling_g).AND. &
             (eta_buffer.LE.h_params%max_pitch_angle).AND. &
             (eta_buffer.GE.h_params%min_pitch_angle).AND. &
             ACCEPTED) THEN
           R_samples(ii) = R_buffer
           Z_samples(ii) = Z_buffer
           eta_samples(ii) = eta_buffer
           G_samples(ii) = G_buffer

!           write(6,*) 'RS',R_buffer
           
           ! Sample phi location uniformly
           !call RANDOM_NUMBER(rand_unif)
           !PHI_samples(ii) = 2.0_rp*C_PI*rand_unif
           !PHI_samples(ii) = 2.0_rp*C_PI*get_random_mkl_U()
           PHI_samples(ii) = 2.0_rp*C_PI*get_random_U()
           ii = ii + 1_idef 
        END IF
        
     end do

!  if (minval(R_samples(:)).lt.1._rp/params%cpp%length) stop 'error with sample'
!  write(6,'("R_sample: ",E17.10)') R_samples(:)*params%cpp%length

     X_samples=R_samples*cos(PHI_samples)
     Y_samples=R_samples*sin(PHI_samples)

!     write(6,*) 'R_samples',R_samples
!     write(6,*) 'PHI_samples',PHI_samples
!     write(6,*) 'Z_samples',Z_samples
!     write(6,*) 'G_samples',G_samples
!     write(6,*) 'eta_samples',eta_samples
     
  end if

  params%GC_coords=.FALSE.
  
  call MPI_BARRIER(MPI_COMM_WORLD,mpierr)


  CALL MPI_SCATTER(X_samples,spp%ppp,MPI_REAL8, &
       spp%vars%X(:,1),spp%ppp,MPI_REAL8,0,MPI_COMM_WORLD,mpierr)
  CALL MPI_SCATTER(Y_samples,spp%ppp,MPI_REAL8, &
       spp%vars%X(:,2),spp%ppp,MPI_REAL8,0,MPI_COMM_WORLD,mpierr)
  CALL MPI_SCATTER(Z_samples,spp%ppp,MPI_REAL8, &
       spp%vars%X(:,3),spp%ppp,MPI_REAL8,0,MPI_COMM_WORLD,mpierr)
  CALL MPI_SCATTER(eta_samples,spp%ppp,MPI_REAL8, &
       spp%vars%eta,spp%ppp,MPI_REAL8,0,MPI_COMM_WORLD,mpierr)
  CALL MPI_SCATTER(G_samples,spp%ppp,MPI_REAL8, &
       spp%vars%g,spp%ppp,MPI_REAL8,0,MPI_COMM_WORLD,mpierr)

  
  call MPI_BARRIER(MPI_COMM_WORLD,mpierr)

!  write(6,*) params%mpi_params%rank,'varX',spp%vars%X(:,1)
!  write(6,*) params%mpi_params%rank,'varY',spp%vars%X(:,2)
  
!  write(6,'("X_X: ",E17.10)') spp%vars%X(:,1)*params%cpp%length
  
  ! gamma is kept for each particle, not the momentum

  if (params%orbit_model(1:2).eq.'GC') call cart_to_cyl(spp%vars%X,spp%vars%Y)

!  write(6,*) params%mpi_params%rank,'varX',spp%vars%X(:,1)
!  write(6,*) params%mpi_params%rank,'varR',spp%vars%Y(:,1)
  

!  write(6,'("Y_R: ",E17.10)') spp%vars%Y(:,1)*params%cpp%length
!  write(6,'("Y_PHI: ",E17.10)') spp%vars%Y(:,1)*params%cpp%length
!  write(6,'("Y_Z: ",E17.10)') spp%vars%Y(:,3)*params%cpp%length
  
!  if (minval(spp%vars%Y(:,1)).lt.1._rp/params%cpp%length) stop 'error with avalanche'
  
  if (params%mpi_params%rank.EQ.0_idef) then
     DEALLOCATE(R_samples)
     DEALLOCATE(X_samples)
     DEALLOCATE(Y_samples)
     DEALLOCATE(Z_samples)
     DEALLOCATE(PHI_samples)
     DEALLOCATE(eta_samples)
     DEALLOCATE(G_samples)
  end if
  
end subroutine sample_Hollmann_distribution_3D_psi

  SUBROUTINE save_params(params)
    TYPE(KORC_PARAMS), INTENT(IN) :: params
    CHARACTER(MAX_STRING_LENGTH) :: filename
    CHARACTER(MAX_STRING_LENGTH) :: gname
    CHARACTER(MAX_STRING_LENGTH), DIMENSION(:), ALLOCATABLE :: attr_array
    CHARACTER(MAX_STRING_LENGTH) :: dset
    CHARACTER(MAX_STRING_LENGTH) :: attr
    INTEGER(HID_T) :: h5file_id
    INTEGER(HID_T) :: group_id
    INTEGER :: h5error
    REAL(rp) :: units

    if (params%mpi_params%rank .EQ. 0) then
       filename = TRIM(params%path_to_outputs) // "experimental_distribution_parameters.h5"
       call h5fcreate_f(TRIM(filename), H5F_ACC_TRUNC_F, h5file_id, h5error)

       gname = "pdf_params"
       call h5gcreate_f(h5file_id, TRIM(gname), group_id, h5error)

       dset = TRIM(gname) // "/max_pitch_angle"
       attr = "Maximum pitch angle in PDF (degrees)"
       call save_to_hdf5(h5file_id,dset,pdf_params%max_pitch_angle,attr)

       dset = TRIM(gname) // "/min_pitch_angle"
       attr = "Minimum pitch angle in PDF (degrees)"
       call save_to_hdf5(h5file_id,dset,pdf_params%min_pitch_angle,attr)

       dset = TRIM(gname) // "/min_energy"
       attr = "Minimum energy in PDF (eV)"
       units = 1.0_rp/C_E
       call save_to_hdf5(h5file_id,dset,units*pdf_params%min_energy,attr)

       dset = TRIM(gname) // "/max_energy"
       attr = "Maximum energy in PDF (eV)"
       units = 1.0_rp/C_E
       call save_to_hdf5(h5file_id,dset,units*pdf_params%max_energy,attr)

       dset = TRIM(gname) // "/max_p"
       attr = "Maximum momentum in PDF (me*c)"
       call save_to_hdf5(h5file_id,dset,pdf_params%max_p,attr)

       dset = TRIM(gname) // "/min_p"
       attr = "Maximum momentum in PDF (me*c)"
       call save_to_hdf5(h5file_id,dset,pdf_params%min_p,attr)

       dset = TRIM(gname) // "/Zeff"
       attr = "Effective atomic number of ions."
       call save_to_hdf5(h5file_id,dset,pdf_params%Zeff,attr)

       dset = TRIM(gname) // "/E"
       attr = "Parallel electric field in (Ec)"
       call save_to_hdf5(h5file_id,dset,pdf_params%E,attr)

       dset = TRIM(gname) // "/k"
       attr = "Shape factor"
       call save_to_hdf5(h5file_id,dset,pdf_params%k,attr)

       dset = TRIM(gname) // "/t"
       attr = "Scale factor"
       call save_to_hdf5(h5file_id,dset,pdf_params%t,attr)

       dset = TRIM(gname) // "/fGo"
       attr = "Normalization of Gamma function"
       call save_to_hdf5(h5file_id,dset,pdf_params%fGo,attr)

       dset = TRIM(gname) // "/lambda"
       attr = "Wavelength used when PDF is weighted with the distribution of synchrotron radiation."
       call save_to_hdf5(h5file_id,dset,pdf_params%lambda,attr)

       dset = TRIM(gname) // "/Bo"
       attr = "Magnetic field used when PDF is weighted with the distribution of synchrotron radiation."
       call save_to_hdf5(h5file_id,dset,pdf_params%Bo,attr)

       call h5gclose_f(group_id, h5error)

       call h5fclose_f(h5file_id, h5error)
    end if
  END SUBROUTINE save_params


  SUBROUTINE save_Hollmann_params(params)
    TYPE(KORC_PARAMS), INTENT(IN) :: params
    CHARACTER(MAX_STRING_LENGTH) :: filename
    CHARACTER(MAX_STRING_LENGTH) :: gname
    CHARACTER(MAX_STRING_LENGTH), DIMENSION(:), ALLOCATABLE :: attr_array
    CHARACTER(MAX_STRING_LENGTH) :: dset
    CHARACTER(MAX_STRING_LENGTH) :: attr
    INTEGER(HID_T) :: h5file_id
    INTEGER(HID_T) :: group_id
    INTEGER :: h5error
    REAL(rp) :: units

    if (params%mpi_params%rank .EQ. 0) then
       filename = TRIM(params%path_to_outputs) // "experimental_distribution_parameters.h5"
       call h5fcreate_f(TRIM(filename), H5F_ACC_TRUNC_F, h5file_id, h5error)

       gname = "pdf_params"
       call h5gcreate_f(h5file_id, TRIM(gname), group_id, h5error)

       dset = TRIM(gname) // "/max_pitch_angle"
       attr = "Maximum pitch angle in PDF (degrees)"
       call save_to_hdf5(h5file_id,dset,h_params%max_pitch_angle,attr)

       dset = TRIM(gname) // "/min_pitch_angle"
       attr = "Minimum pitch angle in PDF (degrees)"
       call save_to_hdf5(h5file_id,dset,h_params%min_pitch_angle,attr)

       dset = TRIM(gname) // "/min_energy"
       attr = "Minimum energy in PDF (eV)"
       units = 1.0_rp/C_E
       call save_to_hdf5(h5file_id,dset,units*h_params%min_energy,attr)

       dset = TRIM(gname) // "/max_energy"
       attr = "Maximum energy in PDF (eV)"
       units = 1.0_rp/C_E
       call save_to_hdf5(h5file_id,dset,units*h_params%max_energy,attr)

       dset = TRIM(gname) // "/max_g"
       attr = "Maximum momentum in PDF (me*c)"
       call save_to_hdf5(h5file_id,dset,h_params%max_g,attr)

       dset = TRIM(gname) // "/min_g"
       attr = "Maximum momentum in PDF (me*c)"
       call save_to_hdf5(h5file_id,dset,h_params%min_g,attr)

       dset = TRIM(gname) // "/max_sampling_g"
       attr = "Maximum momentum in PDF (me*c)"
       call save_to_hdf5(h5file_id,dset,h_params%max_sampling_g,attr)

       dset = TRIM(gname) // "/min_sampling_g"
       attr = "Maximum momentum in PDF (me*c)"
       call save_to_hdf5(h5file_id,dset,h_params%min_sampling_g,attr)
       
       dset = TRIM(gname) // "/Zeff"
       attr = "Effective atomic number of ions."
       call save_to_hdf5(h5file_id,dset,h_params%Zeff,attr)

       dset = TRIM(gname) // "/sigmaZeff"
       attr = "Effective atomic number of ions."
       call save_to_hdf5(h5file_id,dset,h_params%sigma_Z,attr)
       
       dset = TRIM(gname) // "/E"
       attr = "Parallel electric field in (Ec)"
       call save_to_hdf5(h5file_id,dset,h_params%E,attr)

       dset = TRIM(gname) // "/sigmaE"
       attr = "Parallel electric field in (Ec)"
       call save_to_hdf5(h5file_id,dset,h_params%sigma_E,attr)
       
       dset = TRIM(gname) // "/lambda"
       attr = "Wavelength used when PDF is weighted with the distribution of synchrotron radiation."
       call save_to_hdf5(h5file_id,dset,h_params%lambda,attr)

       dset = TRIM(gname) // "/Bo"
       attr = "Magnetic field used when PDF is weighted with the distribution of synchrotron radiation."
       call save_to_hdf5(h5file_id,dset,h_params%Bo,attr)

       call h5gclose_f(group_id, h5error)

       call h5fclose_f(h5file_id, h5error)
    end if
  END SUBROUTINE save_Hollmann_params


END MODULE korc_experimental_pdf