Speaker
Dr
Francesco Tortorici
(CT)
Description
The ICARUS T600 detector, with about 500 tons of sensitive mass, is the largest Liquid Argon
Time Projection Chamber (LAr TPC) ever realized. In 2013 ICARUS concluded an about 4
years long experiment with the T600 detector at the LNGS underground laboratory, taking
data both with the CNGS neutrino beam and cosmic rays.
This very successful experiment demonstrated the high spatial and energy resolutions,
electron/photon separation and particle identification capabilities (via dE/dx vs range
measurements) of the LAr technology.
ICARUS Collaboration refurbished the T600 at CERN, in order to move it to FNAL in the
framework of the SBN experiment, to serve as far detector in studies on the short baseline
neutrino oscillations.
A fundamental part of ICARUS is the light collection system, made of 360 Hamamatsu R5912-
MOD, 8 in. diameter, PMT’s. This system is dedicated to three tasks: the generation of a light
based trigger signal, the identification of the time of occurrence (t 0 ) of each interaction with
high temporal precision and the initial identification of event topology for fast event
selection purposes.
To fulfil its goals a light collection system needs high detection coverage (to be sensitive to
energy deposition in LAr down in energy to 100 MeV), high detection granularity (for space
resolution purposes), fast time response (~ 1 ns) to allow accurate time tracking of each
event in the T600 drift window and to take advantage of the available 2 ns/19 ns bunched
beam structure of the Fermilab Booster facility.
We tested all the PMT’s before installation in the T600, to verify their compliance with the
required functioning specifications. PMT's tests were organized in different CERN areas:
tests at warm temperature were carried out in consecutive bunches of 16 samples in a dark
room and a dedicated laboratory, whereas cryogenic tests were accomplished using a
cryogenic facility which allowed the simultaneous measurement of 10 PMTs in LAr bath, as
the producer made only a mechanical check in liquid nitrogen.
Measurements included the gain as a function of the power supply, the peak-to- valley ratio,
the dark count rate, the linearity of the response as a function of the light intensity and
uniformity of the cathode surface. As expected the PMT's show in general an almost
constant relative variation of the gain, peak to valley ratio and dark counts from room
temperature down to 87K.
The achievement of ~1 ns timing resolution requires a PMT timing calibration system to
compensate individual channel delays and transit-time drifts. The general approach to the
trigger system is the centralization of the basic functionalities into the NI-PXI crate already
used during previous ICARUS run at LNGS, with the following requirements:
- at least one FPGA will be devoted to time critical processes, as clock generation, handling of beam gates and time-stamping of signals;
- one FPGA will be dedicated to manage the PMT signals;
- one Real Time controller will handle handshake with DAQ;
- one FPGA will be dedicated to manage the signals coming from other equipment of
the far detector.
Primary author
Dr
Francesco Tortorici
(CT)
