by habig » Mon Aug 06, 2018 5:45 pm
Hi folks,
This one's my detector, so I'll take a swing at answering some of the questions.
Regarding the different colors: the hits are colored by time. So, earliest hits blue, latest red (that's the colored histogram in the screenshots posted above). The detector has different triggers which read out different lengths of time. The really colorful ones read out 500 microseconds at a go, filling up all the time colors. The blue ones are short, 50 microseconds long, so are much less busy (shorter readout) and all in the blue side of that histogram.
Why? The long 500 microsecond windows are read out 10 times a second like clockwork, so we save a snapshot of what the detector is doing. The shorter ones are saved in response to a potentially interesting pattern: a big splat from a high energy cosmic, something which might be a magnetic monopole, or an atmospheric neutrino, for example. These happen at a rate of ~40-50Hz.
If the beam was on (it's down right now for Fermilab's summer shutdown), we'd get a few beam neutrinos a week: but would save 500 microseconds around each beam spill just in case, which happens about once a second.
Regarding the curved tracks: we don't have a magnetic field in this detector, so if left alone, a particle will go straight. However, the particles aren't left alone: they have to go plowing through our detector. So, sometimes they scatter off a nucleus in the detector and take a turn. The amount of scattering a particle experiences is inversely proportional to its energy: so as a particle comes plowing to a halt, near the end of its track it can appear to fishhook. Note that most of the cosmic ray muons are energetic enough to simply punch straight through.
Yes, this detector is shallow - it's only a few yards of rock away from the sky. It's also 15x15x65 meters big, so our cosmic ray rate is ~100 kHz, resulting in a 1.2 GB/s data stream, of which we save only about 1%. Hopefully, the important 1%!
If you click on the "featured image" link
http://nusoft.fnal.gov/nova/public/ you'll get the whole page, which comes with more explanations, and links to what the neutrinos actually look like.
I'll try to lurk here today and answer whatever other questions pop up!
Alec Habig
Hi folks,
This one's my detector, so I'll take a swing at answering some of the questions.
Regarding the different colors: the hits are colored by time. So, earliest hits blue, latest red (that's the colored histogram in the screenshots posted above). The detector has different triggers which read out different lengths of time. The really colorful ones read out 500 microseconds at a go, filling up all the time colors. The blue ones are short, 50 microseconds long, so are much less busy (shorter readout) and all in the blue side of that histogram.
Why? The long 500 microsecond windows are read out 10 times a second like clockwork, so we save a snapshot of what the detector is doing. The shorter ones are saved in response to a potentially interesting pattern: a big splat from a high energy cosmic, something which might be a magnetic monopole, or an atmospheric neutrino, for example. These happen at a rate of ~40-50Hz.
If the beam was on (it's down right now for Fermilab's summer shutdown), we'd get a few beam neutrinos a week: but would save 500 microseconds around each beam spill just in case, which happens about once a second.
Regarding the curved tracks: we don't have a magnetic field in this detector, so if left alone, a particle will go straight. However, the particles aren't left alone: they have to go plowing through our detector. So, sometimes they scatter off a nucleus in the detector and take a turn. The amount of scattering a particle experiences is inversely proportional to its energy: so as a particle comes plowing to a halt, near the end of its track it can appear to fishhook. Note that most of the cosmic ray muons are energetic enough to simply punch straight through.
Yes, this detector is shallow - it's only a few yards of rock away from the sky. It's also 15x15x65 meters big, so our cosmic ray rate is ~100 kHz, resulting in a 1.2 GB/s data stream, of which we save only about 1%. Hopefully, the important 1%!
If you click on the "featured image" link http://nusoft.fnal.gov/nova/public/ you'll get the whole page, which comes with more explanations, and links to what the neutrinos actually look like.
I'll try to lurk here today and answer whatever other questions pop up!
Alec Habig