Log entry time 23:57:34 on April 07, 2012

Entry number 371410

Attached is a plot of online target polarization for the last 10 days.  
Some caveats to this plot: it is NOT versus dose, so beam trips and the 
like will throw off the decays.  There are also changes in current which 
will affect this plot heavily.  There are certainly stretches in there, 
on the 3rd in particular, where there was no beam, where you can see the 
TE measurements.

I'm not convinced we're see the end of the life of this material yet.  
Toby and I are working on polarization versus charge accumulated plots, 
which will give a more conclusive answer.  I'm not certain we'll have 
them by Monday, though.

Some things in the plot are expected.  Each decay shows the first 
exponential to be very fast, while the second is quite slow.  It also 
looks like postive is doing better than negative, and the top is doing a 
bit better than bottom.

The results from the night of the 7th, if they were taken with the 
correct CC, would not lead me to believe that this material is done.  In 
fact, we probably could have kept that going for awhile.

The results from the 6th do show a faster decay, but this may be due to 
different beam current.  Can anyone comment on that?  It may also be due 
to TO error, but I don't want to jump to conclusions.

I guess we can swap material on Monday if it is advantageous, but I think 
the only indication to do this would be the poorer performance of the 
bottom cell.  We're always going to have a trade off here, as the anneals 
can't be done at exactly the same temperature on top as bottom.

If there is another time in the near future when it might be good to swap 
material, it might be worth considering pushing back the swap.  Of 
course, we shouldn't waste any time that isn't necessary taking a risk 
that this stuff will continue performing well.  On the other hand, we 
don't know that the material we are putting in will perform as well as 
this stuff...

Figure 1