July 1, 2005
Although I was away from the lab for almost 3 weeks and I've been worrying about other things, I couldn't help but keep in touch with MINOS by watching from afar the number of protons hitting the NUMI target to make neutrinos (look for "NuMI" on Fermilab's "Channel 13" and you can keep updating...). In March I talked about the huge jump that was made when people figured out how to get ten trillion protons on target without losing too many of them along the way, and the last month has seen a steady increase in how many protons we can take on the target. Just last week we started routinely taking more than 20 trillion protons on target every few seconds!
You can see this jump in the plot at the left that Brett Viren keeps up to date: it shows that all of a sudden we went over 20 units, which means 20 trillion protons hit our target every 2 seconds or so! You can also see on this plot that we've taken in total more than 1.5 x 10^19 protons on target. For a sense of scale, one gram of protons would be 6 x 10^23 protons, so we've taken about 25 micrograms of protons...all accelerated up to high in energy that each one is 120 times more energetic than its "rest mass" alone.
The problem with neutrino experiments is that since neutrinos interact so rarely, you can basically NEVER make too many of them at a time. So this means that the experiment wants as many protons as possible. But every time you lose protons before they get to the target they have to go somewhere, and these protons are so high in energy that they make lots of new particles (i.e. and radiation!) wherever they go. So we have strict limits on how many protons we can lose in order to be very very very far below any radiation limit.
It's like walking around with a glass of milk--the more full the glass is, the more you're likely to spill some, and you really don't want any of that milk hitting the floor because cleaning it up takes a long time. So you're better off not filling up the glass quite so high, until you learn how to walk very very steadily. In the past month, you can see that the people 
sending us those protons (some of whom, pictured at the left, are not even "on MINOS") have put more and more milk in the glass because they can walk much more steadily now than they could a month ago!
As you can see from the last photo here, the two-year-olds at the 
Fermilab Children's Center aren't making nearly as much progress on not spilling milk. This sign was up for several months, and I hear the highest number of days they went was 3 without spilling.
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