EventMixer code in IC

For MC physics studies, we mix several input streams into a single output stream through the EventMixer python code. The same code also tells us the effective exposure (in years) of a certain number of MC events above some visible energy threshold.

This mixing is necessary because:

• we mix close to 100 background sources, where each source is a given (isotope, Geant4 volume) combination, so the process is cumbersome and relies on detailed activity and detection efficiency assumptions for each (isotope, Geant4 volume) combination
• we want analysers to use a consistent event mix assumption in each analysis cycle, so that results can be easily compared

Background info:

• The code currently lives here https://next.ific.uv.es:8888/nextsw/PyToNE/blob/master/PyToNE/EventMixer.py
• Explanation of what this simple code does at NEXT-doc-287, particularly slide 5: https://next.ific.uv.es/cgi-bin/DocDB/private/ShowDocument?docid=287
• Example configuration file for Nov 2018 background MC production can be found here: https://next.ific.uv.es:8888/nextsw/PyToNE/blob/master/jobOptions/EventMixer_NEW_DepletedXe.job

What we want to change, after discussions with @paolafer and Pau:

• Code currently mixes nexus output files in GATE format. After mixing, all subsequent processing steps starting from the CPU-consuming detsim one are made only for this mixed output stream
• There are scenarios where we want to change normalisation assumptions for the ~100 background sources relatively frequently, yet keeping control of what analysers are using. Reprocessing everything from the detsim stage can be a pain, and the detsim, diomira, irene steps are fairly stable
• The plan would therefore to allow the possibility to mix irene output files in hdf5 format, rather than nexus output files in GATE format. Apart from that, the code would look similar to existing one, specifying input streams, activities and detection efficiencies for each in a long configuration file. However, it would not make sense for this code to be stand-alone anymore, as it would use IC output. So, it should most likely live in IC. In this new scheme, all ~100 background sources would be separately processed all the way through irene, then mixed in correct proportions after irene and before penthesilea.

This issue is about receiving guidance from the experts on how to structure this piece of code in IC:

• Should this be a stand-alone IC city? Something else?
• Is irene the right stage where to mix input streams?
• Should the code be made general to allow for mixing at different stages of event processing, at least within IC part of processing? eg, after diomira, irene, penthesilea, esmeralda, and not just after irene. Unclear to me how much extra work this generalization is, perhaps using existing IC writers this is not so painful. But not obvious to me we really need this, perhaps allowing only post-irene mixing is all we need.

Thanks!

Start by reading PyToNE/EventMixer.py and the EventMixer_NEW_DepletedXe.job example, then inspect IC's existing writers and the irene, penthesilea, diomira, and esmeralda stages. The issue is complete when the project has agreed where this mixer belongs, which processing stage it targets, and whether mixing should support additional stages.