yield station calculation

[bkatiemills]

The yield station tool is nearly ready - the only thing left to figure out is exactly how we're calculating the yield, for both decay and gamma spectrum cases.

• In both cases, I guess the yield you're looking for is the amplitude of the decay curve at the point when implantation stops, divided by BR and efficiency. If that's not the case, let me know.
• For the decay case, we need some way to know what bin corresponds to that point when implantation ends. Are these decay spectra guaranteed to run exactly from the start of implantation to the end of decay observation? If so, we can infer everything we need to know from the cycle definition in the ODB, per @AdamGarnsworthy's comments; otherwise, we need to do something more fancy to figure out where to extrapolate the fit amplitude to.
• In the gamma spectrum case, I suppose the area under a peak should be the same as the area under a decay curve from the start of implantation till the end of decay observation; given the lifetimes, the only free parameter to solve for is the same amplitude mentioned above.

All of which is pretty straightforward - unless it's just wrong. @AdamGarnsworthy please confirm or correct this, and we should be able to get it implemented before eob Friday.