SOME ORDERS OF MAGNITUDE
Neutrinos from stars
Our sun emits around 2 10+38 neutrinos per second !...
and the earth receives more than 40 billions neutrinos
per second and cm2.
This huge raining is undetected by the five senses of the homo sapiens.
Number of neutrinos in the universe
about 330 neutrinos per cm3
about 0.000006 neutrinos per cm3
Explosions of supernovae
about 0.0002 neutrinos per cm3
Energies of the neutrinos
Remember: 1 eV (one electron-volt) = 1.6 10-19 Joules
The Big-Bang neutrinos
the most numerous, are also the less energetic:
(they have still a speed of 2000 km/s if their mass is 10 eV/c2).
Neutrinos from the sun
until about 20 MeV depending of their
Neutrinos from nuclear reactors
a mean energy of 4.0 MeV (between 1 MeV and 10 MeV).
Neutrinos from accelerators today
very various: a mean energy from 30 MeV (LSND) to
30 GeV (NOMAD).
Cross section for interactions with nucleons
at 1 GeV and increasing with energy.
Some surprising numbers
- Our body contains about 20 milligrams of Potassium 40, which is beta radioactive.
As a consequence, we emit about 340 millions neutrinos per day
without knowing that. Neutrinos interact very few, there are thus 340 millions
neutrinos per day, which run from our body at the speed of light until the end of
- An experiment like NOMAD detects about one neutrino every 10 seconds. This one deposits
a mean of 27 GeV in the detector. Thus, for all the duration of the experiment, neutrinos
will have deposited a little more than 0.03 Joules, that is 10 times
less than a sneeze.
- Still in NOMAD, the detector is "active" only during some milliseconds, at each
arriving of neutrinos burst from the particles accelerator. For all the duration
of the experiment (from 1994 to 1998),
the detector was thus "active" only for 15 hours.
- Always in NOMAD, the detector uses a magnet of 0.4 Tesla (2000 times the earth magnetic
field) created by a current of 5713 A. This gives from 1994 to 1998, an energetic
consumption greater than 200.000 billions Joules, that is about
10.000 times your electricity consumption in the same time period (4 years).
- Wherever you are on the earth, even deeply underground, you receive per second about
400.000 billions neutrinos from the sun,
but also 50 billions neutrinos (but this number is not well known!)
from the natural radioactivity of the earth, and
10 to 100 billions neutrinos from nuclear plants
all over the world. Fortunately for us, neutrinos interact very few and you can live
as if they are not there!...
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Last update: 26/06/1999 : http://wwwlapp.in2p3.fr/neutrinos/anchiffres.html