Damien Gallop wrote:

We began looking at 84Kr this weekend. Keerthi had 84Kr19+ on FC6 this morning, which I was able to tweak up from ~300epA to about 600epA. Not bad! This evening it is down to 100pA at best. I think there is a correlation of multi-charge production and room temperature. (It's warm today.) Keerthi noticed tat an entire mass scan this afternoon was suppressed, where I had a solid scan earlier, the two taken the same way. Let's see what happens to FC6 overnight.Beam d

Beam definitely correlated with something overnight. I'm going to say that temperature somehow affects MCIS vacuum, which in turn affects the generation of the higher charge states. We will investigate this further. We did a couple of mass scans this morning. I have closed off the krypton gas bottle to get a background scan. Here is the preliminary one, started a few minutes after closing the hand valve. You can see the clump of 84Kr charge states between approximately masses 4 and 10. Another scan to come shortly, with everything the same except an hour's delay after closing the valve. Here it is, below. The height of the "clump" is less, and it begins more to the right of mass 4 or so than the earlier scan. Note that the small amount of 84Kr remaining after shutting off the source bottle is slightly offset on the plot. I will recalibrate the numbers shortly.