NEUTRINO DETECTION EXPERIMENTS
Three families of detectors:
There are essentially three types of detectors,
according to the energy or origin of the neutrino we want to detect:
Detectors for solar neutrinos:
Solar neutrinos have an energy between 0 and 20 MeV, depending of the type of
solar nuclear reaction they come.
Underground, undersea or under the ice, the detectors made for them
detect either the Cerenkov light emitted
when a neutrino interact with the water (like Kamiokande or Super-Kamiokande)
either the transformation of atoms under neutrino interaction,
the remaining atom being radioactive:
Chlorine 37 coming from Argon in the
Homestake experiment, or Germanium 71 coming from Gallium like in
Here are some examples of
detection principles for solar neutrinos.
exemple: [GALLEX] [HOMESTAKE]
Detectors near nuclear plants:
The anti-neutrinos coming out of nuclear reactors
are emitted in great quantity and have a mean energy of 4 MeV.
The neutrino detector uses the inverse beta decay reaction (
(anti-neutrino + proton --> neutron + anti-electron) to detect anti-neutrinos.
It detects the photons emitted when the neutron is absorbed by matter and
when the anti-electron coming from the neutrino interaction annihilates with an
electron of matter.
This detection type was used by
Reines et Cowan experiment for the first
detection of neutrino in 1956, by BUGEY, by CHOOZ, etc...
Here is shown the
detection principle of the anti-neutrinos coming out of nuclear reactors.
Detectors with neutrino beam:
Nowadays, neutrinos generated by accelerators have an energy of some
10 MeV to some 100 GeV. The detectors in this case identify the particles
coming out of the high energy neutrino interaction with a proton, a neutron
or an electron of the detector matter. The neutrino beams are produced using
a proton beam coming from an accelerator and sent against a Beryllium target,
then filtered through a great amount of dense matter (lead, concrete, iron, earth...).
This detection type was used by the
Brookhaven experiment which discovered the
nu_mu neutrino in 1962,
by CHARM II experiment in 1974,
by NOMAD or CHORUS experiments in 1995, etc...
Experiments present themselves (not exhasutive list):
Two important sites for past and present neutrinos studies
(Sudbury Neutrino Observatory)
- once again SNO
(heavy water Cerenkov detector)
(proton decay search)
- Gran Sasso or
Gran Sasso (INFN)
- Gran Sasso experiments
| BOREXINO ,
or Gallex (MPI),
(Cl37 neutrinos solaires)
(Irvine-Michigan-Brookhaven, desintegration du proton)
(Soviet American Gallium Experiment, montagnes Baksan)
(Old iron mine, Minnesota, USA)
(huge water Cerenkov detector, Japan)
or SuperKamiokande 2
or SuperKamiokande 3
(UK Dark Matter Collaboration, Boulby mine)
Detectors near particles accelerators
Nuclear plant detectors
Detectors in ice
- AMANDA (Antarctic Muon and Neutrino Detector)
- RAND (Radio Array Neutrino Detector)
Solar models and experiments analysis
Site: In Italy, in Abruzzo region, near the tunnel under Grand Sasso mountain,
between Teramo and Roma.
Detector: A container with 12.2 tons of watered Gallium 71, wich, after an interaction
with a solar neutrino, becomes Germanium 71, a radioactive isotope
with a half-life of 11.43 days. The whole set of Gallium 71 and the
eventual Germanium 71 atoms are filtered through a chemical
system allowing to isolate with great efficiency and great purity the Germanium 71 atoms, which
are then detected and counted through their radioactivity, giving thus the number of
neutrino interactions. The solar neutrino flux is deduced.
Results: data taken from May 1991 until September 1993 give a mean of 79+-11 SNU
while theory predicts 132 SNU
(1 SNU = 1 neutrino interaction per second for 10+36 target atoms).
This is a neutrino deficit of 40%.
Why? No definitive good answer yet.
Site: Homestake golden mine, in South Dakota, USA.
Detector: built in 1967 at Brookhaven laboratory,
it contains about 615 tons of tetrachloroethylene.
Under neutrino interaction, the Chlorine 37 becomes Argon 37, which is radioactive with a
half-life of 35 days. As in Gallex experiment, Argon 37 is isolated and its radioactivity
is measured. The number of Argon 37 atoms detected gives the number of neutrino interactions
in the chlorine vat, thus the solar neutrino flux.
Results: data taken from 1969 until 1993 (24 years!!) gives a mean of 2.5+-0.2 SNU
while theory predicts 8 SNU
(1 SNU = 1 neutrino interaction per second for 10E+36 target atoms).
This is a neutrino deficit of 69%. Depending on the solar neutrinos experiments,
the detected solar neutrinos are not in the same
Nothing forbids Homestake experiment
and Gallex experiment to have compatible results.
Site: in the Ardennes region (northern France), 1km from Chooz nuclear plant,
around 100 meters under the earth surface, in a old tunnel.
Detector: The anti-neutrinos coming out of the nuclear reactor, 1km away from the detector,
interact with 300 liters of liquid scintillator doped with gadolinium, in a transparent
acrylic target vessel. It generates an anti-electron and a neutron,
each of them giving photons which are collected by photomultipliers placed around the vessel.
This target is surrounded by a bigger vessel with photomultipliers allowing to eliminate
the background due to cosmic rays or natural radioactivity of the earth.
Results for 1998: no neutrino oscillation
for higher than 0.18 or
higher than 0.9 10-3 eV2.
Site: CERN Meyrin (Swiss), West Area.
Detector: Mainly, a set of 144 drift chambers which is also the main target, a Transition
Radiation Detector to identify electrons and an electromagnetic calorimeter, the whole
installed inside the ancient magnet of the UA1 experiment. The principle is to search
inside a beam of
thanks to protons delivered by CERN accelerator SPS. The interaction of a
generates a tau, particle which is identified
through its decay products.
Results for 1996: data are taken since 1994.
Here is a possible nue interaction in 1995.
Results for 1998:
no neutrino oscillation
for higher than 4.2 10-3 or
higher than 1 eV2.
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Last update: 26/06/1999 : http://wwwlapp.in2p3.fr/neutrinos/anexp.html