subroutine bpm_beampipe(x,y,np,rdum, button)

  use precision_def
  use bpm_mod
  use bpm_interface
  use nr
  use cesr_utils

  implicit none  

  integer np
  real(rp) a/45./, b/24.92/, x0/12.98/,y0/24.92/
  type (grid_struct), allocatable :: grid(:)
  type (bpm_geometry_struct) bpm
  real(rp)  x,y !this is were the bunch is
  real(rp), allocatable :: C(:,:)
  real(rp) theta, dt
  real(rp) r0 !/0.1/ !radius of wire
  real(rp) r
  real(rp) angle(4)
  real(rp) button(4)
!  real(rp) twopi/6.28318530718/
  real(rp), allocatable :: BB(:,:)
  real(rp) rdum

  logical firstime/.true./
  integer np_last

  integer i,j


! if(allocated(grid) .and. np /= np_last)then
!     deallocate(grid)
!     deallocate(C)
! endif
! if(.not. allocated(grid))then
  allocate(grid(1:np))
  allocate(C(np,np))
  allocate(BB(1:np,1))
  call setup_extrusion_grid(grid, bpm,np, r0)
!  np_last = np
! endif

  grid(1)%xs = x
  grid(1)%ys = y
  grid(1)%V = 1.

  do i=1,np
  write(16,'(i,2e12.4)')i, grid(i)%xs, grid(i)%ys
   do j=1,4
  if(grid(i)%point(j))write(17,'(2i,5e12.4)')j,i,grid(i)%xs, grid(i)%ys, grid(i)%ts, bpm%min_angle(j), bpm%max_angle(j)
   end do
  write(18,'(i,e12.4)')i,grid(i)%ts*180/3.141592
  end do

  do i=1,np
   if(i >=2)grid(i)%V=0.
   do j = 1,np
    if(i == j .and. i /= 1) then
      C(i,j) = log(r0/r0)
     elseif(i==j .and. i == 1)then
      C(i,j) = log(r0/r0)
     else
      r = sqrt((grid(i)%xs-grid(j)%xs)**2+(grid(i)%ys-grid(j)%ys)**2)
     if(r == 0.)then
      print *,i,j,r
      print '(4e12.4)', grid(i)%xs, grid(j)%xs, grid(i)%ys, grid(j)%ys
     else
      C(i,j) = log(r/r0)
     endif
    endif
   end do
  end do

! Suppose the charges are Q(i). Then V(i) = C(i,j)*Q(j).
! We know that if i /= 1 then V(i) = 0
! Let's say that V(1) = 1. Then C(i,j)^{-1}V(i) = Q(j)
! And V(x,y) = Q(i)*log(|r-r(i)|)
! Or even better, the charge on the button is the sum over the charges
! intercepted by the angle.

!  print *,' C '

  
!  call gjdet(C,grid(:)%V,grid(:)%Q,np)
  do i=1,np
   BB(i,1) = grid(i)%V
  end do
  call gaussj(C,BB)
  grid(1:np)%Q = BB(1:np,1)
  
!  do i=2,np
!   do j=1,4
!    if(point(j,i))write(12, '(3e12.4)') xs(i), ys(i), q(i) 
!   end do
!write(11, '(3e12.4)') xs(i), ys(i), q(i) 
!  end do

   button(1:4) = 0.
   do i=2,np
    do j=1,4
     if(grid(i)%point(j))button(j) = button(j) + grid(i)%Q
    end do
    write(19,'(i,2e12.4)')i, grid(i)%V, grid(i)%Q
   end do

!   print '(2i,10e12.4)',np,j, x,y,button(1:4), button(1:4)/q(1)
   write(13, '(2i,10e12.4)')np,j, x,y,button(1:4), button(1:4)/grid(1)%q
   
   do j=1,4
    call integrate_charge(bpm%min_angle(j), bpm%max_angle(j), grid(1:np)%q, grid(1:np)%ts, grid(1:np)%point(j),  button(j))
   end do

!   print '(/,2i,10e12.4)',np,j, x,y,button(1:4), button(1:4)/q(1)
   write(15, '(2i,7e12.4)')np,j, x,y,button(1:4), grid(1)%q


   button(1:4) = button(1:4)/grid(1)%q


   deallocate(grid)
   deallocate(C)

  return

 end