Muon Analysis doesn't load deadtime correction if dataset already loaded

I loaded a series of runs to test the performance of deadtime correction of MuSR data (musr00062260 -…270.nxs), first with no deadtime correction, and then tried to reload them with deadtime correction from file. I hoped that Mantid would load the runs with the deadtime correction from the data files.

The files were loaded successfully with no deadtime correction “None” but Mantid gave the error “No dead time correction applied: Data file doesn’t appear to contain dead time values” when I selected “From Data File” from the drop down menu on Muon Analysis Home. The files contain the deadtime information but Mantid is not reading it in.

Load a data file in the Muon Analysis interface without deadtime correction. Then select From Data File from the drop down menu and the error message appears.

Only tested on Windows version 3.9.0.

The problem seems to be more pervasive than first appeared. I started Mantid again to load in all the datasets with dead time correction applied to start with and for all the files it gives errors: “No dead time correction applied: Unable to load dead times from the specified file: Cannot open group mantid_workspace_1 of class NXentry (trying to open path /mantid_workspace_1)”. It is obvious from the plotted data that no dead time correction has been applied. Analysing the data also gave the same fits as uncorrected data.

I spoke to James Lord to see if I was doing something unusual to get the problem and he tried some HiFi data. This gave some runs displayed with the dead time correction as set, but others were not corrected.

Just had a helpful conversation with Anthony Lim: We tried to do the dead time correction from file on MUSR00062260 in Mantid 3.8.x on his Windows machine and it worked fine. This seems to have broken in the update to Mantid 3.9.0.

I have created an issue for this Reading DeadTime data · Issue #18950 · mantidproject/mantid · GitHub

Should be in the nightly build now