ICARUS (Imaging Cosmic And Rare Underground Signals) is a
physics
Physics is the natural science that studies matter, its fundamental constituents, its motion and behavior through space and time, and the related entities of energy and force. "Physical science is that department of knowledge which r ...
experiment aimed at studying
neutrino
A neutrino ( ; denoted by the Greek letter ) is a fermion (an elementary particle with spin of ) that interacts only via the weak interaction and gravity. The neutrino is so named because it is electrically neutral and because its rest mass ...
s. It was located at the
Laboratori Nazionali del Gran Sasso (LNGS) where it started operations in 2010. After completion of its operations there, it was refurbished at
CERN for re-use at
Fermilab
Fermi National Accelerator Laboratory (Fermilab), located just outside Batavia, Illinois, near Chicago, is a United States Department of Energy national laboratory specializing in high-energy particle physics. Since 2007, Fermilab has been opera ...
, in the same neutrino beam as the
MiniBooNE
MiniBooNE is a Cherenkov detector experiment at Fermilab designed to observe neutrino oscillations (BooNE is an acronym for the Booster Neutrino Experiment). A neutrino beam consisting primarily of muon neutrinos is directed at a detector fi ...
,
MicroBooNE
MicroBooNE is a liquid argon time projection chamber (LArTPC) at Fermilab in Batavia, Illinois. It is located in the Booster Neutrino Beam (BNB) beamline where neutrinos are produced by colliding protons from Fermilab's booster-accelerator on a b ...
and
Short Baseline Near Detector (SBND) experiments. The ICARUS detector was then taken apart for transport and reassembled at Fermilab, where data collection is expected to begin in fall 2021.
The ICARUS program was initiated by
Carlo Rubbia
Carlo Rubbia (born 31 March 1934) is an Italian particle physicist and inventor who shared the Nobel Prize in Physics in 1984 with Simon van der Meer for work leading to the discovery of the W and Z particles at CERN.
Early life and educa ...
in 1977, who proposed a new type of
neutrino detector
A neutrino detector is a physics apparatus which is designed to study neutrinos. Because neutrinos only weakly interact with other particles of matter, neutrino detectors must be very large to detect a significant number of neutrinos. Neutrino d ...
.
These are called Liquid Argon Time Projection Chambers (LAr-TPC), which should combine the advantages of
bubble chamber
A bubble chamber is a vessel filled with a superheated transparent liquid (most often liquid hydrogen) used to detect electrically charged particles moving through it. It was invented in 1952 by Donald A. Glaser, for which he was awarded the 1 ...
s and electronic detectors, evolving previous detectors. They detect neutrinos through the reaction:
:
(a neutrino combining with an atom of argon-40 to yield an atom of
potassium
Potassium is the chemical element with the symbol K (from Neo-Latin ''kalium'') and atomic number19. Potassium is a silvery-white metal that is soft enough to be cut with a knife with little force. Potassium metal reacts rapidly with atmosph ...
-40 and an electron.)
In the course of the ICARUS program, such detectors of considerable capacity were proposed. After first runs at
Pavia
Pavia (, , , ; la, Ticinum; Medieval Latin: ) is a town and comune of south-western Lombardy in northern Italy, south of Milan on the lower Ticino river near its confluence with the Po. It has a population of c. 73,086. The city was the cap ...
in 2001, the ICARUS T600 detector at
Gran Sasso
Gran Sasso d'Italia (; ) is a massif in the Apennine Mountains of Italy. Its highest peak, Corno Grande (2,912 metres), is the highest mountain in the Apennines, and the second-highest mountain in Italy outside the Alps. The mountain lies wi ...
, filled with 760 tons of liquid
argon
Argon is a chemical element with the symbol Ar and atomic number 18. It is in group 18 of the periodic table and is a noble gas. Argon is the third-most abundant gas in Earth's atmosphere, at 0.934% (9340 ppmv). It is more than twice as ...
, started operation in 2010. In order to study
neutrino oscillations and various fundamental topics of
modern physics, neutrinos of astronomic or solar sources, and
CERN Neutrinos to Gran Sasso
The CERN Neutrinos to Gran Sasso (CNGS) project was a physics project of the European Organization for Nuclear Research (CERN). The aim of the project was to analyse the hypothesis of neutrino oscillation by directing a beam of neutrinos from CE ...
(CNGS)
beam produced 730 km away by the
Super Proton Synchrotron from
CERN, have been detected.
The CNGS neutrinos are also studied by the
OPERA experiment
The Oscillation Project with Emulsion-tRacking Apparatus (OPERA) was an instrument used in a scientific experiment for detecting tau neutrinos from muon neutrino oscillations. The experiment is a collaboration between CERN in Geneva, Switzerla ...
, therefore those experiments are also called
CNGS1 (OPERA) and CNGS2 (ICARUS).
The CNGS measurements also became important when the OPERA group announced in September and November 2011 that they had measured
superluminal neutrinos (see ''
faster-than-light neutrino anomaly
In 2011, the OPERA experiment mistakenly observed neutrinos appearing to travel faster than light. Even before the source of the error was discovered, the result was considered anomalous because speeds higher than that of light in vacuum are g ...
''). Shortly afterwards, the ICARUS collaboration published a paper in which they argued that the energy distribution of the neutrinos is not compatible with superluminal particles. This conclusion was based on a theory of Cohen and
Sheldon Glashow
Sheldon Lee Glashow (, ; born December 5, 1932) is a Nobel Prize-winning American theoretical physicist. He is the Metcalf Professor of Mathematics and Physics at Boston University and Eugene Higgins Professor of Physics, Emeritus, at Harvard U ...
.
In March 2012, they published a direct neutrino velocity measurement based on seven neutrinos events. The result was in agreement with the speed of light and thus special relativity, and contradicts the OPERA result.
In August 2012, another neutrino velocity measurement based on 25 neutrino events was published with increased accuracy and statistics, again in agreement with the speed of light. (See ''
measurements of neutrino speed
Measurements of neutrino speed have been conducted as tests of special relativity and for the determination of the mass of neutrinos. Astronomical searches investigate whether light and neutrinos emitted simultaneously from a distant source are ar ...
''.)
The ICARUS detector moved to Fermilab in July 2017 for a new neutrino experiment. In February 2020, scientists at Fermilab began cooling down ICARUS and filling it with 760 tons of liquid
argon
Argon is a chemical element with the symbol Ar and atomic number 18. It is in group 18 of the periodic table and is a noble gas. Argon is the third-most abundant gas in Earth's atmosphere, at 0.934% (9340 ppmv). It is more than twice as ...
. Scientists hope to take the first measurements with the refurbished ICARUS later in 2020.
In May 2021, Fermilab announced that ICARUS would begin data collection in the fall of 2021.
References
External links
ICARUS webpage
{{Neutrino detectors
Neutrino experiments
CERN experiments