JINST Instrumentation Theses Archive

Ph.D. degree thesis
accepted by Universit� Paris 7 - Denis Diderot - France, in 2005

Maria Elena Monzani

Supervisor: Herv� de Kerret

Characterization and calibration of the Borexino detector for solar and supernova neutrinos

 Keywords:

• Scintillators, scintillation and light emission processes (solid, gas and liquid scintillators)
• Electronic detector readout concepts (gas, liquid)
• Pattern recognition, cluster finding, calibration and fitting methods
• Software architectures (event data models, frameworks and databases)

 Abstract:
The main goal of the Borexino experiment (Gran Sasso Laboratories, Italy) is the real time exploration of the sub-MeV region of the solar neutrino spectrum, namely the measurement of the monochromatic Beryllium line at 860 keV. Beyond this pioneering measurement, the detector can be used to study anti-neutrinos from the Earth interior and from nuclear power reactors, as well as neutrinos and anti-neutrinos from Supernova explosions.

In this thesis, Borexino has been characterized and calibrated over a wide energy range, for the detection of neutrinos from the different sources. The quality of the Borexino liquid scintillator has been studied by means of the detector prototype (CTF): several purification methods have been tested on the scintillator, with the aim to demonstrate the possibility to reach the extremely low radioactivity levels required for physics.

The Borexino read-out system has been completed and fully tested: the behaviour of the read-out chain was studied in realistic conditions, showing very good performances. A finalization work was performed on the different sub-systems, including the photomultipliers and their calibration system, the electronics and the Data Acquisition Software.

The energy and position reconstruction capabilities of the detector have been evaluated, demonstrating that the system is ready and operational for data taking. An additional electronics chain has been installed, finalized and tested, with the specific aim to explore the high energy range up to the 10 MeV region and beyond (mainly for Supernova neutrino detection).