Fix for random phase value bug in PyChop

docs/source/interfaces/direct/PyChop.rst

@@ -66,6 +66,8 @@ If the *Instrument scientist mode* option is selected, a similar option is
 enabled for MERLIN if the G chopper is used. In this case, the phase (time
 delay) of the thick disk chopper can be adjusted. The time delay is the time-of-
 flight at which the chopper slit first opens (sweeps across the beam profile).
+In the event that this mode is then deselected, the time delay entered previously
+will be utilised for subsequent calculations instead of the default value.
 
 The Matplotlib axes showing the calculated data have the standard toolbars.
 

docs/source/release/v6.11.0/Direct_Geometry/General/Bugfixes/37805.rst

@@ -0,0 +1 @@
+- Fix for random phase values on Merlin when using PyChop not in instrument scientist mode.

qt/python/mantidqtinterfaces/mantidqtinterfaces/PyChop/PyChopGui.py

@@ -214,17 +214,20 @@ def setFreq(self, freqtext=None, **kwargs):
         # Checks for independent phases
         phases = []
         for key, widget in self.widgets.items():
-            if key.endswith("Phase") and not widget["Label"].isHidden():
-                idx = int(key[7])
-                phase = widget["Edit"].text()
-                if isinstance(self.engine.chopper_system.defaultPhase[idx], str):
-                    phase = str(phase)
-                else:
-                    try:
-                        phase = float(phase) % (1e6 / self.engine.moderator.source_rep)
-                    except ValueError:
-                        raise ValueError(f'Incorrect phase value "{phase}" for {widget["Label"].text()}')
-                phases.append(phase)
+            if key.endswith("Phase"):
+                # Special case for MERLIN
+                # sets the default phase for Chopper0Phase if not in "Instrument Scientist Mode"
+                if not widget["Label"].isHidden() or "MERLIN" in str(self.engine.instname) and key[7] == 0:
+                    idx = int(key[7])
+                    phase = widget["Edit"].text()
+                    if isinstance(self.engine.chopper_system.defaultPhase[idx], str):
+                        phase = str(phase)
+                    else:
+                        try:
+                            phase = float(phase) % (1e6 / self.engine.moderator.source_rep)
+                        except ValueError:
+                            raise ValueError(f'Incorrect phase value "{phase}" for {widget["Label"].text()}')
+                    phases.append(phase)
         if phases:
             self.engine.setFrequency(freq_in, phase=phases)
         else:
@@ -642,9 +645,9 @@ def _gen_text_ei(self, ei, obj_in):
         txt += "# Ei = %8.2f meV\n" % (ei)
         txt += "# Flux = %8.2f n/cm2/s\n" % (flux)
         txt += "# Elastic resolution = %6.2f meV\n" % (res[0])
-        txt += "# Time width at sample = %6.2f us, of which:\n" % (1e6 * np.sqrt(tsqvan))
+        txt += "# Time width at sample = %6.2f us, of which:\n" % (1e6 * np.sqrt(tsqvan[0]))
         for ky, val in list(tsqdic.items()):
-            txt += "#     %20s : %6.2f us\n" % (ky, 1e6 * np.sqrt(val))
+            txt += "#     %20s : %6.2f us\n" % (ky, 1e6 * np.sqrt(val[0]))
         txt += "# %s distances:\n" % (obj.instname)
         txt += "#     x0 = %6.2f m (%s to Fermi)\n" % (x0, first_component)
         txt += "#     x1 = %6.2f m (Fermi to sample)\n" % (x1)

scripts/pychop/merlin.yaml

@@ -21,7 +21,7 @@ chopper_system:
       radius: 300               # Disk radius
       isDouble: False           # Is this a double disk system?
       isPhaseIndependent: True  # Is this disk to be phased independently?
-      defaultPhase: 12800       # What is the default phase for this disk (either a time in microseconds
+      defaultPhase: 12400       # What is the default phase for this disk (either a time in microseconds
                                 #   or a slot index [as a string] for the desired rep to go through)
       phaseOffset: 11300        # Offset introduced after disk chopper controller update
       phaseName: 'Disk chopper phase delay time'