subroutine define_materials()
      integer imate
      character*20 namate
      real A(9)
      real Z(9)
      real W(9)
      real dens,radl,absl
      integer nlmat

      call gmate

c fiber core material
      imate = 100
      namate = 'polystyrene'
      A(1) = 1.01
      Z(1) = 1
      A(2) = 12.01
      Z(2) = 6
      W(1) = 1
      W(2) = 1
      nlmat = -2
      dens = 0.95
      radl = 42.4
      absl = 82.
      call gsmixt(imate,namate,a,z,dens,nlmat,wmat)

c inner cladding material
      imate = 101
      namate = 'acrylic'
      A(1) = 1.01
      Z(1) = 1
      A(2) = 12.01
      Z(2) = 6
      A(3) = 16.
      Z(3) = 8
      W(1) = 8
      W(2) = 5
      W(3) = 2
      nlmat = -3
      dens = 1.18
      radl = 40.5
      absl = 100.
      call gsmixt(imate,namate,a,z,dens,nlmat,wmat)

c outer cladding material
      imate = 102
      namate = 'fluor-acrylic'
      A(1) = 1.01
      Z(1) = 1
      A(2) = 12.01
      Z(2) = 6
      A(3) = 16.
      Z(3) = 8
      W(1) = 8
      W(2) = 5
      W(3) = 2
      nlmat = -3
      dens = 1.18
      radl = 40.5
      absl = 100.
      call gsmixt(imate,namate,a,z,dens,nlmat,wmat)

      end