Handling multiple He3 cells?

[SimonHeybrock]

@astellhorn mentioned that He3 cells may be switched out during an experiment. However, in the basics workflow defined in #3 we have assumed that we have a single set of parameters such as He3Pressure and He3FillingTime.

If my understanding is correct then we need to generalize this, adding e.g., a cell identifier to compute, e.g., a cell-dependent He3Opacity. This would however imply that we need to perform independent fits, i.e., we also get a cell-dependent He3Transmission. For the full run we would then have to concatenate multiple such time-dependent decay functions (or handle the entire data reduction independently when switching to a new cell).

[astellhorn]

THe measurement with unpolarized cell ("switched off cell" as you said) probably needs to be performed only sometimes to make sure the precharacterization of the Opacity is good, but does not need to be done in every user experiment. How is something like that inserted into the workflow, where you do a pre-characterization only sometimes to check, but not every time? Apart from these checkup-measurements, the opacity should be constant in time, and values like pressure and filling time can be inserted to the metadata by the 3He team, whereas the wavelength dependence will also be precharacterized but depend on which wavelength-band and -binning the user chooses for.

[astellhorn]

I try to also catch this in an over view slide with the other DB background measurements

[SimonHeybrock]

How is something like that inserted into the workflow, where you do a pre-characterization only sometimes to check, but not every time?

This is an excellent question. I would assume that the pre-characterization results would be written to a file, which will then be available on SciCat. We will somehow have to know how to find the correct characterization runs for the cells that are used in a user's experiment. You should get in touch with @nitrosx (Massimiliano Novelli) to discuss this.

[SimonHeybrock]

• We should use filling time, cell pressure, and cell length (recorded in NeXus) file to identify if the same cell is used for a run (ideally also cell ID).
• Given a collection of runs and based on above params (read from each run) we can categorize the runs into runs for different cells.
• For each cell, we can then, e.g., load all direct-beam runs (or run sections) and perform a fit to obtain the time-decay of the transmission.
• Finally, we can correct the sample data. Merging of runs for different cells can be performed after or before the correction. If before the correction, we also merge the transmission time decays obtain from the separate fits.