1. magnetic confinement - ENEA - Fusione

4. MISCELLANEOUS 113
4.1 Development of CVD Diamond
Detectors for Nuclear Radiation
Diamond detectors are of particular interest as neutron detectors in fusion
environments since they present higher radiation resistance than silicon detectors. In
collaboration with the Faculty of Engineering of Tor Vergata University in Rome,
diamond films produced with the chemical vapour deposition (CVD) method are
being developed and their characteristics analysed for nuclear detection.
During 2001, several new samples of CVD diamond were grown and tested with
nuclear particles (alpha particles and electrons) to investigate important parameters
such as grain dimensions, film purity and lattice properties [4.1].
[4.1] M. Marinelli et al.,
Phys. Rev. B, 64,
195205–1 (2001)
[4.2.] R. Bernabei et al.,
Eur. Phys. J. Direct, C11,
1 (2001)
[4.3] G. Barbiellini et al.,
CP587, GAMMA 2001:
G a m m a - R a y
Astrophysics, pag 774
(2001)
The film quality was studied as a function of the growing parameters (methane
concentration, substrate temperature, chamber volume, film thickness) to establish
whether or not it was possible to optimise the quality of diamond films. Alpha
particles of different energy were used to study the film properties. Hence, by
considering the penetration depth at each energy, it was possible to define the grain
size and the collection length. The present quality of CVD films grown at Tor Vergata
University in collaboration with ENEA represents the state-of-the-art for these
materials in terms of charge collection efficiency (70%). The work pointed out that,
to improve detection efficiency, it is necessary to improve film purity.
4.2 Light Response of a Pure
Liquid Xenon Scintillator
The search for dark matter is one of the most stimulating fields in fundamental
physics. To establish in which form the so-called “missing mass of universe” does
exist represents a result of paramount importance to understanding the structure of
the universe. Several experiments are being carried out world-wide to detect
particles that are candidates as “dark matter”. One of these experiments, actually
named Dark Matter (DAMA), is being conducted by the Italian Institute for Nuclear
Physics (INFN) at the “Gran Sasso” underground laboratory and is devoted to
searching for the so-called Weak Interacting Massive Particle (WIMP). The DAMA
experiment makes use of different detectors (liquid xenon and NaI) and is based
upon the search of the recoil spectra produced by WIMPs when interacting with the
detectors. It is very important to calibrate the detectors in the energy range where
the recoil spectra are expected. In particular, the so-called quenching of the
scintillator has to be known to properly measure the recoil spectrum. Kinematics
calculations show that the quenching factor can be well reproduced if high-energy
neutrons are used.
Based on this theoretical finding, the liquid xenon detector was calibrated at the
Frascati Neutron Generator (FNG) with the use of 2.5-MeV neutrons. Results of the
calibration and details of the method are reported in [4.2]. The main output of the
calibration campaign was the ratio of the measured amount of light from the xenon
recoil nucleus to the amount of light from an electron of the same kinetic energy
(quenching). Results substantially in agreement with the previous determination
were obtained.
4.3 Partecipation in the AGILE Project:
Collimator and Coded Mask of the
SuperAGILE Detector
AGILE (Astrorivelatore Gamma ad Immagini Leggero) [4.3] is the first mission of the
Small Missions Programme of the Italian Space Agency (ASI). Its main goal is to
monitor the gamma-ray sky in the energy range 30-50 GeV, with a large field of view
(~3 sr), good sensitivity, good angular resolution and good timing. The satellite is