From 439a77b8308deb6219054f311d78a5d067c032b5 Mon Sep 17 00:00:00 2001
From: Filip Leonarski <filip.leonarski@psi.ch>
Date: Wed, 21 May 2025 13:35:45 +0200
Subject: [PATCH] Add diffraction conversion routines

---
 common/src/aaredaqlib/diffraction.py | 47 ++++++++++++++++++++++++++++
 1 file changed, 47 insertions(+)
 create mode 100644 common/src/aaredaqlib/diffraction.py

diff --git a/common/src/aaredaqlib/diffraction.py b/common/src/aaredaqlib/diffraction.py
new file mode 100644
index 00000000..e5e2c733
--- /dev/null
+++ b/common/src/aaredaqlib/diffraction.py
@@ -0,0 +1,47 @@
+import math
+
+
+def cal_res_A(detector_distance_mm: float,
+              wavelength_angstrom: float,
+              radius_mm: float) -> float:
+    """
+    Calculate maximum achievable resolution in Angstroms.
+
+    Args:
+        detector_distance_mm: Distance from crystal to detector in mm
+        wavelength_angstrom: X-ray wavelength in Angstroms
+        radius_mm: Detector radius in mm
+
+    Returns:
+        Resolution in Angstroms
+    """
+    # Calculate theta using arctangent of opposite/adjacent
+    theta = math.atan(radius_mm / detector_distance_mm) / 2.0
+
+    # Using Bragg's law: n𝜆 = 2d*sin(θ)
+    # Solving for d: d = 𝜆/(2*sin(θ))
+    resolution = wavelength_angstrom / (2 * math.sin(theta))
+    return resolution
+
+
+def calc_dtz_mm(desired_resolution_angstrom: float,
+                wavelength_angstrom: float,
+                radius_mm: float) -> float:
+    """
+    Calculate required detector distance for desired resolution.
+
+    Args:
+        desired_resolution_angstrom: Desired resolution in Angstroms
+        wavelength_angstrom: X-ray wavelength in Angstroms
+        radius_mm: Detector radius in mm
+
+    Returns:
+        Required detector distance in mm
+    """
+    # From Bragg's law: sin(θ) = 𝜆/(2d)
+    theta = math.asin(wavelength_angstrom / (2 * desired_resolution_angstrom))
+
+    # Using tangent: tan(2θ) = opposite/adjacent
+    # Therefore: distance = radius/tan(2θ)
+    distance = radius_mm / math.tan(2 * theta)
+    return distance