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\title{ICARUS}
\author{A. Rappoldi$^1$, on behalf of the ICARUS Collaboration}
\address{$^1$ INFN Sezione di Pavia, Pavia, IT}
\ead{andrea.rappoldi@pv.infn.it}


\begin{abstract}

After its successful operation at the INFN underground laboratories
of Gran Sasso (LNGS) from 2010 to 2013, ICARUS has been moved to
Fermilab Laboratory at Chicago (FNAL),
where it represents an important element of the
Short Baseline Neutrino Project (SBN).

Indeed, the ICARUS T600 detector, which has undergone various technical upgrades
operations at CERN to improve its performance and make it more suitable
to operate at shallow depth, will constitute one of three LAr detectors
exposed to the FNAL Booster Neutrino Beam (BNB).

The purpose of this project is to provide adequate answers to the
"sterile neutrino puzzle", due to the observation, claimed by various
other experiments, of anomalies in the results obtained in the
measurement of the parameters that regulate the mechansm of neutrino
flavor oscillations.

\end{abstract}

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\section{The ICARUS project}
\label{ICARUS}

The technology of the Liquid Argon Time Projection chamber (LAr TPC),
was first proposed by scientist Carlo Rubbia in 1977. It was conceived as a tool for
detecting neutrinos in a way that would result in completely uniform imaging with high
accuracy of massive volumes (several thousand tons).

ICARUS T600, the first large-scale detector exploiting this detection technique,
is the biggest LAr TPC ever realized, with a cryostat containing 760 tons of liquid argon.
Its construction was the culmination of many years of ICARUS collaboration R\&D studies,
with larger and larger laboratory and industrial prototypes, mostly developed thanks
to the Italian National Institute for Nuclear Physics (INFN), with the support of CERN.

Nowadays, it represents the state of the art of this technique, and it marks a major
milestone in the practical realization of large-scale liquid-argon detectors.

The ICARUS T600 detector was previously installed in the underground Italian INFN Gran
Sasso National Laboratory (LNGS) and was the first large-mass LAr TPC operating as a continuously
sensitive general-purpose observatory.
The detector was exposed to the CERN Neutrinos to Gran Sasso (CNGS) beam,
a neutrino beam produced at CERN and
traveling undisturbed straight through Earth for 730 km. 

This very successful run lasted 3 years (2010-2013),
during which were collected
$8.6 \cdot 10^{19}$ protons on target with a
detector live time exceeding 93\%, recording 2650 CNGS neutrinos,
(in agreement with expectations) and cosmic rays (with a total exposure of 0.73 kilotons per year).
ICARUS T600 demonstrated the effectiveness of the so-called {\it single-phase} TPC technique
for neutrino physics, providing a series of results, both from the technical and from the
physical point of views.

Beside the excellent detector performance, both as tracking device and as homogeneous calorimeter,
ICARUS demonstrated a remarkable capability in electron-photon separation and particle
identification, exploiting the measurement of dE/dx versus range, including also the
reconstruction of the invariant mass of photon pairs (coming from $\pi^0$ decay) to reject to unprecedented level
the Neutral Current (NC) background to $\nu_e$ Charge Current (CC) events (see Fig.~\ref{Fig1}).

\begin{figure}[ht]
\centering
% \includegraphics[width=0.8\textwidth,natwidth=1540,natheight=340]{icarus-nue.png}
\includegraphics[width=0.8\textwidth]{icarus-nue.png}
\end{figure}

\begin{figure}[ht]
\centering
\includegraphics[width=0.6\textwidth]{ICARUS-nue-mip.png}
\caption{\label{Fig1} {\it Top:} A typical $\nu_e$ CC events recorded during the ICARUS operation
at LNGS. The neutrino, coming from the right, interacts with the Ar nucleus and produce a
proton (short heavy ionizing track) and an electron (light gray track) which starts an electromagnetic
shower, which develops to the left. {\it Bottom:} The accurate analysis of {\it dE/dx} allows
to easily distinguish the parts of the track in which there is the overlap of more particles,
locating with precision the beginning of the shower.}
\end{figure}

The tiny intrinsic $\nu_e$ component in the CNGS $\nu_{\mu}$
beam allowed ICARUS to perform a sensitive search for anomalous LSND-like $\nu_\mu \rightarrow \nu_e$ oscillations.
Globally, seven electron-like events have been observed, consistent with the $8.5 \pm 1.1$ events
expected from intrinsic beam $\nu_e$ component and standard oscillations, providing the limit on
the oscillation probability $P(\nu_\muμ \rightarrow \nu_e) \le 3.86 \cdot 10^{−3}$ at 90\% CL and
$P(\nu_\mu \rightarrow \nu_e) \le 7.76 \cdot 10^{−3}$ at 99\% CL, as shown in
Fig.~\ref{Fig2}.

\begin{figure}[ht]
\centering
\includegraphics[width=0.5\textwidth]{ICARUS-sterile-e1529944099665.png}
\caption{\label{Fig2} Exclusion plot for the $\nu_\mu \rightarrow \nu_e$ oscillations.
The yellow star marks the best fit point of MiniBooNE.
The ICARUS limits on the oscillation probability are shown with the red lines. Most of
LSND allowed regios is excluded, except for a small area around $\sin^2 2 \theta \sim 0.005$,
$\Delta m^2 < 1 eV^2$.  
}
\end{figure}

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\section{ICARUS at FNAL}
\label{FNAL}
After its successful operation at LNGS, the ICARUS T600 detector was planned
to be included in the Short Baseline Neutrino project (SBN) at Fermilab\cite{SBN},
in Chicago, aiming to give some definitive answer to the so-called
{\it Sterile Neutrino Puzzle}.
In this context, it will operate as the {\it far detector}, put along the
Booster Neutrino Beam (BNB) line, 600 meters from the target (see Fig.~\ref{Fig3}).

\begin{figure}[h]
\centering
\includegraphics[width=0.8\textwidth]{SBN.png}
\caption{\label{Fig3} The Short Baseline Neutrino Project (SBN) at
Fermilab (Chicago) will use three LAr TPC detectors, exposed to the
Booster Neutrino Beam, at different distances fron the target.
The ICARUS T600 detector, put at 600 m, will operate as the {\it far detector},
voted to detect any anomaly in the beam flux and spectrum, with respect to
the initial beam composition detected by the {\it near detector}
(SBND).
These anomalies, due to neutrino flavour oscillations, would consist of
either $\nu_e$ appearence or $\nu_\mu$ disappearance.
}
\end{figure}

For this purpose, the ICARUS T600 detector underwent intensive
overhauling at CERN, before shipping to FNAL,
in order to make it better suited to surface operation (instead of in
an underground environment).

This important technical improvements took place in the CERN
Neutrino Platform framework (WA104) from 2015 to 2017.
In addition to significant mechanical improvements, especially concerning
a new cold vessel, with a purely passive thermal insulation,
some important innovations have been applied to the scintillation
light detection system\cite{PMT} and to the readout
electronics\cite{Electronics}.

% The role of ICARUS will be to detect any anomaly in the neutrino beam flux and
% composition that can occour during its propagation (from the near to the
% far detector), caused by neutrino flavour oscillation.
% This task requires to have an excellent capability to detect and identify
% neutrino interaction within the LAr sensitive volume, rejecting any other
% spurious event with a high level of confidence.

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\section{ICARUS data amount}
\label{Computingreport_2015.pdf}

% The new ICARUS T600 detector (that has been modified and improved to operate
% at FNAL) contains about 54,000 sensitive wires (that give an electric signal
% proportional to the charge released into the LAr volume by ionizing particles)
% and 180 large PMTs, producing a prompt signal coming from the scintillation light.
% Both these analogic signal types are then converted in digital form, by mean of
% fast ADC modules.
%
% During normal run conditions, the trigger rate is about 0.5 Hz, and
% a full event, consisting of the digitized charge signals of all wires
% and all PMTs, has a size of about 80 MB (compressed).
% Therefore, the expected acquisition rate is about 40 MB/s, corrisponding
 %to 1 PB/yr.

The data produced by ICARUS detector (which is a LAr Time Projection Chamber)
basically consist of a large number of waveforms generated by sampling the electric
signals induced on the sensing wires by the drift of the charge deposited along
the trajectory of the charged particles within the Lar sensitive volume.
 
The waveforms recorded on about 54000 wires and 360 PMTs are digitized
(at sample rate of 2.5 MHz and 500 MHz respectively) and compressed,
resulting in a total size of about 80 MB/event.

Considering the forseen acquisition rate of about 0.5 Hz (in normal
run conditions), the expected data flow is about 40 MB/s, which
involves a data production of about 1 PB/yr.

The raw data are then processed by automated filters that allow to recognize
and select the various event types (cosmic, beam, background, etc.) and rewrite
them in a more flexible format, suitable for the following analysis,
which is also supported by means of graphics interactive programs.

% The experiment is expected to start commissioning phase at the end of 2018,
% with first data coming as soon as the Liquid Argon filling procedure is completed.
% Trigger logic tuning will last not less than a couple of months during which
% one PB of data is expected. 

Furthermore, the ICARUS Collaboration is actively working on
producing Montecarlo events needed
to design and test the trigger conditions to be implemented on the detector.
This is done by using the same analysis and simulation tools
developed at Fermilab for the SBN detectors (the {\it LArSoft framework}), in
order to have a common software platform, and to facilitate algorithm testing
and performance checking by all the components of the collaboration.

During the 2018 many activities related to the detector installation
were still ongoing, and the start of data acquisition activities
is scheduled for the 2019.

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\section{Role and contribution of CNAF}
\label{CNAF}

All the data (raw and reduced) will be stored on the Fermilab using local facility;
however, the ICARUS collaboration agreed to have a mirror site in Italy
(located at CNAF INFN Tier1) where to retain a full replica of the preselected
raw data, both to have redundancy and provide a more direct data access
to european part of the collaboration.

The CNAF Tier-1 computing resources assigned to ICARUS for 2018 consist of:
4000 HSPEC of CPU, 500 TB of disk storage and 1500 TB of tape archive.

A small fraction of the available storage has been used to
make a copy of all the raw data acquired at LNGS,
which are still subject to analysis.

During 2018 the ICARUS T600 detector was still in preparation, so
only a limited fraction
of such resorces has been used, mainly to perform data transfer tests
(from FNAL to CNAF) and to check the installation of LArSoft framework
in the Tier-1 environment. For this last purpose, a dedicate virtual
machine with custom environment was also used.


%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\section*{References}

\begin{thebibliography}{1}

\bibitem{SBN}
  R. Acciarri et al.,
  {\it A Proposal for a Three Detector Short-Baseline Neutrino
       Oscillation Program in the Fermilab Booster Neutrino Beam},
  arXiv:1503.01520 [physics.ins-det]

\bibitem{PMT}
  M. Babicz et al.,
  {\it Test and characterization of 400 Hamamatsu R5912-MOD
       photomultiplier tubes for the ICARUS T600 detector}.
  JINST 13 (2018) P10030

\bibitem{Electronics}
  L. Bagby et al.,
  {\it New read-out electronics for ICARUS-T600 liquid
       argon TPC. Description, simulation and tests of the new
       front-end and ADC system}.
   JINST 13 (2018) P12007

\end{thebibliography}


\end{document}