I've been on the SIMS instrument all day since yesterday. It's pretty monotonous, but not as bad as babysitting the STXM at the synchrotron. I've been analyzing for silicon, oxygen, carbon, nitrogen, sulfur, and phosphorus. In a chert, Si and O should be constant, but C, N, S, and P should fluctuate together depending on how much carbonaceous goo is around. However, I've been getting constant, large N signals, which was weird. So this afternoon I put in a sample I had previously analyzed two years ago in the old SIMS. I went to the same spots as two years ago, and N was still too large. Then I noticed that the signal coming off the sample for N was diffuse instead of a tiny beam, like all the other elements. So I tried putting in a tiny aperture around the beam to cut off any stray electrons other than the central ones, and suddenly the numbers began to match up. Almost exactly like before. So I have to put the other samples back in the SIMS tomorrow to see if an aperture affects the N signal from those samples as well. I may have to redo all the previous analyses (or most of them at least).