Paper 94-5
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GRAIN-SIZE EFFECTS IN CVD DIAMOND DETECTORS
NUCLEAR INSTRUMENTS & METHODS IN PHYSICS
RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS 93 (4): 516-520 SEP 1994 |
MANFREDOTTI C, FIZZOTTI F, VITTONE E, BISTOLFI S, BOERO M, POLESELLO P |
Experimental Physics
Department, University of Torino (Italy), Consorzio INFM UdR of Torino
(Italy) and National Institute for Nuclear Physics, Sezione di Torino (Italy) |
Keywords: CVD diamond, Alpha particle spectroscopy,
electrical properties |
ABSTRACT
CVD diamond nuclear detectors have been investigated with 241Am alpha
particles and with Sr-90 beta particles in various conditions of bias
polarization and irradiation geometry. It is proved that
the parameter indicated as collection distance in the literature is an
average value defined over a broad distribution which should be related to the
grain size distribution inside the detector and, likely,
also to fluctuations of the electrical field inside the grains. The
sampling techniques used to detect the pulses normally select the largest
values of the collection distances, as underscored by results
obtained from our measurements with beta particles by using these
techniques; results have been found to be in good agreement with literature
data. The collection length distribution has been found
to be compatible with a superposition of two log-normal distributions,
which are typical of grain dimension distributions in polycrystalline
materials. It can be argued that grain size is a limiting factor
for the collection distance and contributes with its fluctuations to the
broadening of the pulses height spectrum of a minimum ionizing particle (MIP)
in CVD diamond detectors. It can also be argued
that sampling techniques suffer from pulse counting losses, which should
be partly due to grain boundary effects.