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mantidproject / mantid

Main repository for Mantid code
https://www.mantidproject.org
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Event Filtering Broken For Moinitors with FastLogs #13035

Closed OwenArnold closed 9 years ago

OwenArnold commented 9 years ago

If you run an experiment using time slicing of events, you should also run the monitors in event mode so that you can time slice from those in the same way to perform normalization correctly.

For detectors, the L1/(L1 + L2) offset results in TatSample <= TatDetector. However for Monitor, neturons meet those before they hit the sample, thefore TatSample >= TatMonitors. The problem is that L2 as calculated here uses this which always returns an absolute value for L2. This is wrong. The ratio L1/(L1+L2) should be >= 1 for monitors.

If a detector really is a detector, the existing implementation is fine because we always expect neutrons to go source -> sample -> detector. This also works correctly with backscattering so |L2| is correct in these cases. If a detector is a monitor, then we should use the signed value of L2 because monitors can appear both in front and behind the sample.

Fixes need to be made to FilterEvents and RebinByTimeAtSample

OwenArnold commented 9 years ago

If this could be done early next week that would be ideal. This is what the user says:

Yes next week, especially if it could be towards the beginning/middle of it, will be fine.
I would like to try to have some data reduced in time for the UK ferroelectrics conference: I have a talk on the 21st.
Worst case scenario, I can still present the concept and leave the data for another time.