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   "cell_type": "markdown",
   "id": "digital-oriental",
   "metadata": {},
   "source": [
    "# Diffractometer Extra Solver Parameters\n",
    "\n",
    "Some of the diffractometer _modes_ use extra parameters.  The {ref}`E4CV\n",
    "<geometries-hkl_soleil-e4cv>` geometry, for example, has a `double_diffraction` mode which requires a reference {math}`hkl_2` vector.  The vector is set as a Python dictionary:\n",
    "\n",
    "action  | `E4CV` method\n",
    ":---    | :---\n",
    "read    | `e4cv.core.solver.extras`\n",
    "write   | `e4cv.core.solver.extras =` dictionary\n",
    "\n",
    "**Objective**\n",
    "\n",
    "Show how to use the `double_diffraction` mode in the `E4CV` geometry."
   ]
  },
  {
   "cell_type": "markdown",
   "id": "assigned-length",
   "metadata": {},
   "source": [
    "## `E4CV`, `hkl`, `double_diffraction`\n",
    "\n",
    "term | value\n",
    ":--- | :---\n",
    "geometry | `E4CV`\n",
    "engine | `hkl`\n",
    "mode | `double_diffraction`\n",
    "\n",
    "Using the standard `E4CV` geometry with simulated motors, we copy the [E4CV setup for the *LNO_LAO* sample](https://github.com/bluesky/hklpy/tree/main/docs/source/examples/notebooks/tst_e4cv_fourc.html#read-the-spec-scan-from-the-data-file).  Using a kwarg, we can automatically compute the UB matrix once we define the second reflection.  (This means we do not have to call `compute_UB()` on a separate line.)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 1,
   "id": "adapted-minnesota",
   "metadata": {
    "tags": []
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "diffractometer='e4cv'\n",
      "HklSolver(name='hkl_soleil', version='5.1.2', geometry='E4CV', engine_name='hkl', mode='bissector')\n",
      "Sample(name='LNO_LAO', lattice=Lattice(a=3.7817, b=3.7914, c=3.7989, alpha=90.2546, beta=90.0182, gamma=89.8997, system='triclinic'))\n",
      "Reflection(name='r_85d9', h=0.0, k=0.0, l=2.0)\n",
      "Reflection(name='r_bca7', h=1.0, k=1.0, l=3.0)\n",
      "Orienting reflections: ['r_85d9', 'r_bca7']\n",
      "U=[[-0.057509522654, -0.998327393204, 0.005922059067], [0.000158283449, 0.005922758763, 0.999982447783], [-0.998344945272, 0.057509450598, -0.000182596327]]\n",
      "UB=[[-0.095549901092, -1.654278634916, 0.002428444854], [0.000262981975, 0.009814839065, 1.65396180769], [-1.658712442301, 0.098200239641, -0.000389705577]]\n",
      "constraint: -180.0 <= omega <= 180.0\n",
      "constraint: -180.0 <= chi <= 180.0\n",
      "constraint: -50.0 <= phi <= 100.0\n",
      "constraint: -2.0 <= tth <= 180.0\n",
      "h=0, k=0, l=0\n",
      "wavelength=1.239424258\n",
      "omega=0, chi=0, phi=0, tth=0\n"
     ]
    }
   ],
   "source": [
    "import hklpy2\n",
    "\n",
    "e4cv = hklpy2.creator(name=\"e4cv\")\n",
    "e4cv.restore(\"e4cv-LNO_LAO.yml\")\n",
    "e4cv.wh(full=True)"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "manual-harmony",
   "metadata": {},
   "source": [
    "Set the `double_diffraction` mode."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 2,
   "id": "twelve-gathering",
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "e4cv.core.solver.mode='double_diffraction'\n",
      "e4cv.core.solver.extras={'h2': 1.0, 'k2': 1.0, 'l2': 1.0}\n"
     ]
    }
   ],
   "source": [
    "e4cv.core.solver.mode = \"double_diffraction\"\n",
    "print(f\"{e4cv.core.solver.mode=!r}\")\n",
    "print(f\"{e4cv.core.solver.extras=!r}\")"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "crucial-virus",
   "metadata": {},
   "source": [
    "Set $hkl_2=(2\\ 2\\ 0)$."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 3,
   "id": "insured-petite",
   "metadata": {},
   "outputs": [],
   "source": [
    "e4cv.core.solver.extras = {'h2': 2.0, 'k2': 2.0, 'l2': 0}"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "detected-collapse",
   "metadata": {},
   "source": [
    "## Calculate (002) with (220) as second diffracting plane"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 4,
   "id": "advance-there",
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "e4cv.core.solver.extras={'h2': 2.0, 'k2': 2.0, 'l2': 0.0}\n",
      "(002) : Hklpy2DiffractometerRealPos(omega=19.125950423193, chi=89.98528785702, phi=19.056580679972, tth=38.084061000204)\n"
     ]
    }
   ],
   "source": [
    "print(f\"{e4cv.core.solver.extras=!r}\")\n",
    "print(\"(002) :\", e4cv.forward(0, 0, 2))"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "adolescent-trust",
   "metadata": {},
   "source": [
    "## Calculate (002) with (222) as second diffracting plane"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 5,
   "id": "proprietary-spray",
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "e4cv.core.solver.extras={'h2': 2.0, 'k2': 2.0, 'l2': 2.0}\n",
      "(002) : Hklpy2DiffractometerRealPos(omega=19.125989270384, chi=89.985511037941, phi=18.904237535436, tth=38.084060988627)\n"
     ]
    }
   ],
   "source": [
    "e4cv.core.solver.extras = {'h2': 2.0, 'k2': 2.0, 'l2': 2}\n",
    "print(f\"{e4cv.core.solver.extras=}\")\n",
    "print(\"(002) :\", e4cv.forward(0, 0, 2))"
   ]
  }
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