1 gaskelld 1.1 	subroutine rotate_haxis(rotang,xp0,yp0)
 2              
 3              C+______________________________________________________________________________
 4              !
 5              ! ROTATE_HAXIS- Calculate new trajectory coordinates in reference frame rotated
 6              !   about horizontal axis by angle ROTANG relative to central ray.
 7              !
 8              ! *** Right-handed TRANSPORT coordinates are assumed! ***
 9              !
10              !   ROTANG is an angle about the  negative Y-axis.
11              !   For the SOS BM01 entrance, it is a negative number.
12              !
13              !   Input trajectory is: X = XS + ALPHA*(Z-ZS)
14              !                        Y = YS + BETA *(Z-ZS)
15              !                        Z = ZS is current point.
16              !
17              !   Output traject is:  XP = XP0 + ALPHA_P*ZP
18              !                       YP = YP0 + BETA_P *ZP
19              !                       ZP = 0 gives intersection of track with rotated plane.
20              !
21              ! ROTANG (R*4):	Rotation angle in degrees.
22 gaskelld 1.1 !
23              ! D. Potterveld, 15-Mar-1993.
24              C-______________________________________________________________________________
25              
26              	implicit none
27              
28                      include '../spectrometers.inc'
29              
30              	real*8 rotang,xp0,yp0,xi
31              	real*8 alpha,beta,alpha_p,beta_p,sin_th,cos_th,tan_th
32              	real*8 rotang_rad, raddeg
33              
34              	save
35              
36              C ============================= Executable Code ================================
37              
38              C Sep. 2008 DJG: No equivaleent to sind etc. in gfortran. Convert to radians first.
39              
40              
41              	parameter (raddeg=0.017453292) 
42              
43 gaskelld 1.1 	rotang_rad = rotang*raddeg
44              
45              c1	tan_th = tand(rotang)
46              c	sin_th = sind(rotang)
47              c	cos_th = cosd(rotang)
48              
49              1	tan_th = tan(rotang_rad)
50              	sin_th = sin(rotang_rad)
51              	cos_th = cos(rotang_rad)
52              
53              	alpha  = dxdzs
54              	beta   = dydzs
55              
56              	alpha_p= (alpha + tan_th)/(1. - alpha*tan_th)
57              	beta_p = beta/(cos_th - alpha*sin_th)
58              
59                      xi = xp0
60              	xp0    = xi*(cos_th + alpha_p*sin_th)
61              	yp0    = yp0 + xi*beta_p*sin_th
62              
63              	return
64 gaskelld 1.1 	end