Adds function timFactorFromVoltage() and TIM calibration table

xgm.py

@@ -565,3 +565,67 @@ def calibrateTIM(data, rollingWindow=200, mcp=1, plot=False, use_apd=True, intst
         plt.tight_layout()
 
     return F
+
+''' TIM calibration table
+    Dict with key= photon energy and value= array of polynomial coefficients for each MCP (1,2,3).
+    The polynomials correspond to a fit of the logarithm of the calibration factor as a function
+    of MCP voltage. If P is a polynomial and V the MCP voltage, the calibration factor (in microjoule
+    per APD signal) is given by -exp(P(V)).
+    This table was generated from the calibration of March 2019, proposal 900074, semester 201930, 
+    runs 69 - 111 (Ni edge):  https://in.xfel.eu/elog/SCS+Beamline/2323
+    runs 113 - 153 (Co edge): https://in.xfel.eu/elog/SCS+Beamline/2334
+    runs 163 - 208 (Fe edge): https://in.xfel.eu/elog/SCS+Beamline/2349
+'''
+tim_calibration_table = {
+    705.5: np.array([
+        [-6.85344690e-12,  5.00931986e-08, -1.27206912e-04, 1.15596821e-01, -3.15215367e+01],
+        [ 1.25613942e-11, -5.41566381e-08,  8.28161004e-05, -7.27230153e-02,  3.10984925e+01],
+        [ 1.14094964e-12,  7.72658935e-09, -4.27504907e-05, 4.07253378e-02, -7.00773062e+00]]),
+    779: np.array([
+        [ 4.57610777e-12, -2.33282497e-08,  4.65978738e-05, -6.43305156e-02,  3.73958623e+01],
+        [ 2.96325102e-11, -1.61393276e-07,  3.32600044e-04, -3.28468195e-01,  1.28328844e+02],
+        [ 1.14521506e-11, -5.81980336e-08,  1.12518434e-04, -1.19072484e-01,  5.37601559e+01]]),
+    851: np.array([
+        [ 3.15774215e-11, -1.71452934e-07,  3.50316512e-04, -3.40098861e-01,  1.31064501e+02],
+        [5.36341958e-11, -2.92533156e-07,  6.00574534e-04, -5.71083140e-01,  2.10547161e+02],
+        [ 3.69445588e-11, -1.97731342e-07,  3.98203522e-04, -3.78338599e-01,  1.41894119e+02]])
+}
+
+def timFactorFromVoltage(voltage, photonEnergy=None, mcp=1):
+    ''' Returns an energy calibration factor for TIM integrated peak signal (APD)
+        according to calibration from March 2019, proposal 900074, semester 201930, 
+        runs 69 - 111 (Ni edge):  https://in.xfel.eu/elog/SCS+Beamline/2323
+        runs 113 - 153 (Co edge): https://in.xfel.eu/elog/SCS+Beamline/2334
+        runs 163 - 208 (Fe edge): https://in.xfel.eu/elog/SCS+Beamline/2349
+        Uses the tim_calibration_table declared above.
+        
+        Inputs:
+            voltage: MCP voltage in volts.
+            photonEnergy: FEL photon energy in eV. Calibration factor is linearly
+                interpolated between the known values from the calibration table. 
+                If None, takes the median photon energy from the calibration table.
+            mcp: MCP channel (1, 2, or 3).
+            
+        Output:
+            f: calibration factor in microjoule per APD signal
+    '''
+    energies = np.sort([key for key in tim_calibration_table])
+    if photonEnergy is None:
+        photonEnergy = np.median(energies)
+    if photonEnergy not in photon_energies:
+        if photonEnergy > energies.max():
+            photonEnergy = energies.max()
+        elif photonEnergy < energies.min():
+            photonEnergy = energies.min()
+        else:
+            idx = np.searchsorted(photon_energies, energy) - 1
+            polyA = np.poly1d(tim_calibration_table[energies[idx]][mcp-1])
+            polyB = np.poly1d(tim_calibration_table[energies[idx+1]][mcp-1])
+            fA = -np.exp(polyA(voltage))
+            fB = -np.exp(polyB(voltage))
+            f = fA + (fB-fA)/(energies[idx+1]-energies[idx])*(photonEnergy - energies[idx])
+            return f
+    poly = np.poly1d(tim_calibration_table[photonEnergy][mcp-1])
+    f = -np.exp(poly(voltage))
+    return f
+    
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