It has been an exhilirating (if exhausting) week for the MINERvA experiment.
I described in my first post how we had constructed a portion of our detector in a building on the surface here at Fermilab, and were now beginning the process of disassembling it to move it deep underground to sit in the path of the high intensity neutrino beam being created here at the laboratory. That painstaking process has already borne its first fruit.
Dozens of people have been working long hours every day over the last week to get to this point. Starting early each morning, a skilled mechanical crew carefully transports by truck each 2,000 lb. slice of the detector from its old location to the neutrino hall access point. The module is then hoisted with an industrial crane and slowly lowered down the 300 ft’ access shaft (quite a thrill to look down from above the next time you are at Fermilab – just be sure your glasses don’t slide off your nose!). Another crew receives the steel frame at the bottom and carefully maneuvers it through the tunnel to hang it alongside those that came before. The detector is slowly built up like slices of bread make up a loaf.
Me showing off the required underground fashion accessory (hard hat) and capturing a moment of our detector in construction. The cherry picker is used to hoist the crew above the detector to install the electronics (the blue cylinders sticking out of the top).
Looking back the other way, a new module is being carefully brought in to hang with the others.
For every four new slices, the next crew, made up of collaborating students and post-docs like myself, comes in and works the ‘second shift’ from about 2:00-10:00PM. We mount all the electronic instrumentation and carefully route hundreds of cables and optical fibers down to the racks below where a computer system awaits to read the signals from 1,000’s of electronics channels.
Okay, great, but how do we know when we see something coming from the neutrino beam? Conveniently, the neutrinos are produced in quick bursts instead of continuously. Trillions of neutrinos pass though the detector over a very short period of about 10 microseconds (10 millionths of a second), and this happens every 2 seconds. Therefore we expect to see a large increase in activity in our detector during this brief 10 millionths of a second relative to the rest of each 2 second period. Wednesday night a few hardy physicists stayed late into the night determined to record the data we were looking for – to see neutrinos with our detector for the first time.
I was at home that evening because my parents are in town to visit and arrived Wednesday afternoon. I was sitting at home talking with my mother when the email came in around 10:30PM that the data had been taken. I, consumed with excitement, apologized to my mother, and logged in to work (she has known me for a very long time, and so wasn’t exactly surprised 🙂 ).
A few hours later, about 1:00AM when I finally sorted out the details and made this plot:
Activity in our detector over a brief time period showing the huge spike in activity corresponding to the arrival of the neutrino beam.
I let out a little yell!! – and even my mother, looking over my shoulder at the time and encouraging me to “get my rest”, realized that such a striking spike must mean something. The narrow spike is the activity in the MINERvA detector during that brief 10 millionths of a second – the clear signature of hundreds of particles, invisible to our eyes and created by neutrinos, flying through the slices of our loaf of bread.
I immediately sent the plot out to the collaboration – about a hundred dedicated scientists and engineers working for the past several years to build this device. There is a lot of challenging work ahead to decode the wealth of information contained in the signals from our new experiment. But we have incontrovertible proof that the darn thing works, and that has a lot of us really excited.
