Add sanity checks and correct R2.

Radia_Ex06.ipynb

@@ -422,10 +422,19 @@
   },
   {
    "cell_type": "markdown",
-   "metadata": {},
+   "metadata": {
+    "tags": []
+   },
+   "source": [
+    "## _Create the quadrupole and solve for the fields_"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {
+    "tags": []
+   },
    "source": [
-    "## _Create the quadrupole and solve for the fields_\n",
-    "\n",
     "First set the various parameters that specify the properties—geometry,\n",
     "materials, and current—of our quadrupole. Then also decide how finely\n",
     "to segment the iron."
@@ -547,7 +556,9 @@
   },
   {
    "cell_type": "markdown",
-   "metadata": {},
+   "metadata": {
+    "tags": []
+   },
    "source": [
     "## _Plots of the magnetic field and field integrals_\n",
     "\n",
@@ -674,13 +685,12 @@
     "    This function constructs one half of a vertical sector of a multipole magnet.\n",
     "    It then applies appropriate symmetries to construct and orient the full magnet.\n",
     "    '''\n",
-    "    # sanity checks on user input\n",
-    "    # :: even number of magnetic poles?\n",
+    "    # sanity check: even number of magnetic poles?\n",
     "    assert n_poles % 2 == 0, \"Argument n_poles must equal an even integer.\"\n",
-    "    # :: pole tips do not intersect? ==> automatic!! <==\n",
-    "    # :: lower pole tip includes all of pole face?\n",
-    "    # :: coil_1 does not cross sector diagonal\n",
-    "    # :: coil_2 does not cross sector diagonal\n",
+    "    # sanity check: positive coil height?\n",
+    "    assert tip_coil_sep < height, \"Tip-coil separation exceeds height of pole tip.\"\n",
+    "    # sanity check: chamfers do not cut into all of pole tip?\n",
+    "    assert chamfer < thick / 2, \"Chamfer too large.\"\n",
     "\n",
     "    # define a few useful vectors\n",
     "    ctr = [0, 0, 0]\n",
@@ -695,12 +705,19 @@
     "    z0 = gap / 2\n",
     "    ym = width / 2\n",
     "    a_max =  asinh(hyp * ym / z0)\n",
+    "    zm = z0 * cosh(a_max)\n",
+    "    # sanity check: pole tip includes all of pole face?\n",
+    "    assert zm <= z0 + height, \\\n",
+    "          \"Pole tip height too short to accommodate entire curved pole face.\"\n",
     "    da = a_max / n_curve\n",
     "    na = n_curve + 3  # go two points beyond so we don't have to extend the array\n",
     "    qq = [ [(z0 / hyp) * sinh(ia * da), z0 * cosh(ia * da)] for ia in range(na) ]\n",
     "    # and\n",
     "    # modify last two points so as to outline lower portion of the (half) pole tip\n",
     "    ht_lower = poletip_frac * height\n",
+    "    # sanity check: lower fraction of pole tip includes all of pole face?\n",
+    "    assert zm <= z0 + ht_lower, \\\n",
+    "          \"Lower fraction of pole tip cannot accommodate entire pole face.\"\n",
     "    qq[n_curve + 1] = [ym, z0 + ht_lower]\n",
     "    qq[n_curve + 2] = [ 0, z0 + ht_lower]\n",
     "\n",
@@ -749,8 +766,16 @@
     "    # and set color for iron\n",
     "    rad.ObjDrwAtr(g, ironcolor)\n",
     "\n",
+    "    # sanity check: coil_1 does not cross sector diagonal\n",
+    "    # assert y_coil < y1\n",
+    "    # sanity check: coil_2 does not cross sector diagonal\n",
+    "    # assert y_coil < y2\n",
+    "\n",
     "    # create coil1\n",
     "    ht_coil = height - tip_coil_sep\n",
+    "    # sanity check: coil does not extend below outer edge of curved pole tip\n",
+    "    assert zm < z0 + height - ht_coil, \\\n",
+    "           \"Inner coil will obscure part of the curved pole tip.\"\n",
     "    wd_to_diagonal = (gap / 2 + tip_coil_sep) * tan_np\n",
     "    r_max = wd_to_diagonal - clearance - width / 2 + r_min\n",
     "    coil1 = rad.ObjRaceTrk([0, 0, z0 + height - ht_coil / 2], [r_min, r_max],\n",
@@ -760,8 +785,7 @@
     "    # create coil2\n",
     "    ht_coil = (height - tip_coil_sep) / 2\n",
     "    wd_to_diagonal = (gap / 2 + height - ht_coil) * tan_np\n",
-    "    # r2 = wd_to_diagonal - clearance - width / 2 + r_min\n",
-    "    r2 = r_max + 0.8 * ht_coil\n",
+    "    r2 = wd_to_diagonal - clearance - width / 2 + r_min\n",
     "    coil2 = rad.ObjRaceTrk([0, 0, z0 + height - ht_coil / 2], [r_max, r2],\n",
     "                           [thick, width - 2 * r_min],\n",
     "                           ht_coil, 3, curr_density)\n",