subroutine alpham(dwtp,iend,np)	
c--------------------------------------------------------------------------
      save
c
      include 'param_sz.h'
      include 'constcom.h'
      include 'pcordcom.h'
      include 'syscom.h'
      include 'ucom.h'
c
      common/aswap/acor(7,imaa)	
      data itest/0/		
c--------------------------------------------------------------------------
cbm !!! warning is for theta = 40.71 degres
cbm      data thetar,sr,cr,tr/.71052354,.65223071,.75802051,0.8604394/!LIU 
c--------------------------------------------------------------------------
c*
c	el(1,ne)=l distance travelled by the r.p. for a complete cycle
c	el(2,ne)=aper (vmax) for dropping
c	el(3,ne)=iout 
c	el(4,ne)=wr energy of r.p.
c	el(5,ne)=thetd incident and exiting angles in degrees
c	el(6,ne)=wmax
c	el(7,ne)=deltab
c	el(8,ne)=l1
c	el(9,ne)=l2
c	el(10,ne)=xles
c	el(11,ne)=xhes
c
c	-------------------------------
      ne=rne
	if(itest.eq.0) then
		gr=el(4,ne)/erest
		bg=sqrt(gr*(2.+gr))
		rhour=brhof*bg/el(7,ne)
	endif		
        thetar=el(5,ne)*radian
        sr=sin(thetar)
        cr=cos(thetar)
        tr=tan(thetar)
C	---------------------------
	if(gamma.le.1.5) go to 100	!added oct 20 89
c	---------------------------
	dphi=dcon*dwtp
	xp=bgx/bgz
	yp=bgy/bgz
	if(acor(7,np).eq.1.) go to 70  !particle  in
	bz=bgz/gamma
	dz=bz*dphi
	x=x+xp*dz
	y=y+yp*dz
	z=z+dz
	if(acor(7,np).eq.-1.) then
		zaway=zloc(ne)-z	!particle out
		zn=el(9,ne)-zaway
		u=-zn*cr-x*sr
		v=zn*sr-x*cr
		if(zaway.le.0.) then
			iend=1
			acor(7,np)=0.0
		endif
		return
	else
		zaway=zloc(ne-1)+el(8,ne)+x*tr-z
		zn=-zaway
		u=zn*cr-x*sr
		v=zn*sr+x*cr
	endif
	if(u.lt.0.) go to 65
	bx=bgx/gamma
	by=bgy/gamma
	acor(1,np)=u
	acor(2,np)=v
	acor(3,np)=y
	acor(4,np)=bz*cr-bx*sr
	acor(5,np)=bz*sr+bx*cr
	acor(6,np)=by
	acor(7,np)=1.
65	continue
        return
70	continue
c	-----------------------
	u=acor(1,np)
	v=acor(2,np)
	w=acor(3,np)
	bu=acor(4,np)
	bv=acor(5,np)
	bw=acor(6,np)
c	------------------------------
	if(abs(u).lt.0.1.and.(abs(v).ge.el(2,ne).or.abs(w).ge.el(6,ne)))
     .   go to 100
c	------------------------------
	theta1=atan(xp)
c	theta1=atan2(bx,bz)
	con=1.+xp**2+yp**2
c	thetai=thetar+theta1	!injection angle for an electron
c	-------------------------
c	buvsq=bu**2+bv**2
c	buv=sqrt(buvsq)
c	rhou=bgd*buv	!for an electron
c
c	ac=deltab/(gamma*brhof)
	acd=dphi*el(7,ne)/(gamma*brhof)
c	phi0=0.5*(0.5*pi-thetai)
c	umax=2.*cos(phi0)*sqrt(buv/ac)
c	------------------------------------
c	h1=v*cr
c	hf=-h1-1.28*umax*theta1
c	hf=-h1-1.28*umax*xp
c	
	dbu=acd*u*bv
	dbv=acd*(w*bw-u*bu)
	dbw=-acd*w*bv
c
	bu=bu+dbu
	bv=bv+dbv
	bw=bw+dbw
	buvsq=bu**2+bv**2
	buv=sqrt(buvsq)
c
	du=bu*dphi
	dv=bv*dphi
	dw=bw*dphi
	u=u+du
	v=v+dv
	w=w+dw
c	print 110,x,z,u,v,bv
c110	format(1x,5(e12.5,1x))
c	1.3=.85(r of d.t)/sr   !!!!!!!!
	if(u.lt.1.3) go to 72
	vsign=v/acor(2,np)
	if(vsign.lt.0.0.and.(u.le.el(10,ne) .or. u.ge.el(11,ne))) 
     .    go to 100
  72	continue
	rccc=(bu*dbv-bv*dbu)/dphi
	rhoa=abs(buvsq*buv/rccc)
	thetaa=atan2(bv,bu)
c	--------------------------
	ur=u+x*sin(thetaa-theta1)  !u of c.r.
c	if(ur.le.0.0) goto 66
	rhor=rhour/ur
	rh=rhor+x
	ds=sqrt(du**2+dv**2)
	be=ds*cos(theta1)
c	be=ds  !modified for test
	ang=be/rh
	dz=rhor*ang
c
	ant=ang+theta1
	sant=sin(ant)
	cant=cos(ant)
c	ct1=cos(theta1)
	arg=sant-(rh/rhoa)*sin(ang)
	if(abs(arg).ge.1.) go to 100
	theta2=asin(arg)
	ct2=cos(theta2)
	h2=-rhor+rh*cos(ang)+rhoa*(ct2-cant)
c	---------
	zn=z+dz
	z = zn
	x=h2
c	y=y+yp*rhoa*(ant-theta2)*ct1
c	yp=yp*ct1/ct2
	y=w
	by=bw
	yp=by/(buv*ct2)
	xp=tan(theta2)
	bgz=bgz*sqrt(con/(1.+xp**2+yp**2))
	bgx=xp*bgz
	bgy=yp*bgz
	gamma=sqrt(1.+bgx**2+bgy**2+bgz**2)
c
	if(u.gt.0.) go to 90
	acor(7,np)=-1.
	return
  90 	continue
	acor(1,np)=u
	acor(2,np)=v
	acor(3,np)=w
	acor(4,np)=bu
	acor(5,np)=bv
	acor(6,np)=bw
	return
 100	continue
c	WRITE(NDIAG,101) IEND,(ACOR(KK,NP),KK=1,7)
c	write(ndiag,101) np,u,v,w,bu,bv,bw,acor(7,np)
c	write(ndiag,101) ne,x,y,z,bx,by,bz,gamma
c101	format(1x,i5,7(e9.2,1x))
	x=2.*el(2,ne)
	return
	end
c++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++*