Merge pull request #293 from jgray-19/fix_sbend_face

Adjust MAD-NG bend face to match PTC

Author: ldeniau

src/madl_dynmap.mad

@@ -1773,33 +1773,35 @@ function bend_face (h, m, lw) -- [NEWFACE]                                   --
 
   m.atdebug(h, m, lw, 'bend_face:0')
 
-  local edir, beam in m
-  local   k0h = 0.5*h * knl[1]/(eld or el)*edir
+  local edir, sdir, tdir, beam in m
+  ! h is weighted by tdir, el is weighted by sdir, so to get tdir back, we need to multiply by sdir
+  local   k0h = 0.5*h * knl[1]/(eld or el) * sdir
   local   chg = beam.charge
   local _beta = 1/beam.beta
 
   for i=1,m.npar do
     local x, px, y, py, t, pt, beam in m[i]
     local _beta = beam and 1/beam.beta or _beta
     local chg   = beam and beam.charge or chg
+    local k0hq  = k0h*chg -- k0hq must be weighted by bdir
 
-    if lw == 1 then -- to insure reversal symmetry ; horizontal wedge (only dir)
-      px = px + chg*k0h*x^2
+    if tdir == 1 then -- to insure reversal symmetry ; horizontal wedge (only tdir)
+      px = px + k0hq*x^2
     end
 
     local dpp      =  1 + 2*pt*_beta + pt^2
     local _pt2     =  1/(dpp - px^2)
-    local xi       =  2*k0h*lw*sqrt(dpp)*_pt2
-    local dxi_px   =  2*px*xi           *_pt2
-    local dxi_ddel = -2   *xi*(1+pt)    *_pt2
+    local xi       =  2*k0hq*sqrt(dpp)*_pt2
+    local dxi_px   =  2*px*xi         *_pt2
+    local dxi_ddel = -2   *xi*(1+pt)  *_pt2
 
     x  = x / (1-dxi_px*y^2)
     px = px - xi*y^2
     py = py - 2*xi*x*y
-    t  = t  - dxi_ddel*x*y^2
+    t  = t  + dxi_ddel*x*y^2
 
-    if lw == -1 then -- to insure reversal symmetry; horizontal wedge (only dir)
-      px = px - chg*k0h*x^2
+    if tdir == -1 then -- to insure reversal symmetry; horizontal wedge (only tdir)
+      px = px + k0hq*x^2
     end
 
     m[i].x  = x