41 research outputs found
Radiation measurements as tool for environmental and geophysics studies on volcano-tectonic areas
In the last years there has been an increasing concern about naturalradioactivity measurements both from the point of view of the environmental survey, especially for the human health protection, and of the geophysical-events investigation in volcanic areas and tectonic fault zones. We report on our activity in both these fields, in particular on the measurements of indoor radon concentration in a long-term passive monitoring in dwellings of the eastern region of Sicily. Because this region is characterized by high seismicity, besides the indoor radioactivity survey, in-soil radon measurements in the region (both volcanic and tectonic area) can provide a better insight and a valuable database for the study related to radon anomalies. A synthesis is reported of the results that we obtained, in the last years, in the volcanic and tectonic area of oriental Sicily both from indoor monitoring and from geophysical-events investigation
Time Scales in Spectator Fragmentation
Proton-proton correlations and correlations of p-alpha, d-alpha, and t-alpha
from spectator decays following Au + Au collisions at 1000 AMeV have been
measured with an highly efficient detector hodoscope. The constructed
correlation functions indicate a moderate expansion and low breakup densities
similar to assumptions made in statistical multifragmentation models. In
agreement with a volume breakup rather short time scales were deduced employing
directional cuts in proton-proton correlations.
PACS numbers: 25.70.Pq, 21.65.+f, 25.70.MnComment: 8 pages, with 5 included figures; To appear in the proceedings of the
CRIS 2000 conference; Also available from
http://www-kp3.gsi.de/www/kp3/aladin_publications.htm
Thermal and Chemical Freeze-out in Spectator Fragmentation
Isotope temperatures from double ratios of hydrogen, helium, lithium,
beryllium, and carbon isotopic yields, and excited-state temperatures from
yield ratios of particle-unstable resonances in 4He, 5Li, and 8Be, were
determined for spectator fragmentation, following collisions of 197Au with
targets ranging from C to Au at incident energies of 600 and 1000 MeV per
nucleon. A deviation of the isotopic from the excited-state temperatures is
observed which coincides with the transition from residue formation to
multi-fragment production, suggesting a chemical freeze-out prior to thermal
freeze-out in bulk disintegrations.Comment: 14 pages, 10 figures, submitted to Phys. Rev. C, small changes as
suggested by the editors and referee
Breakup Density in Spectator Fragmentation
Proton-proton correlations and correlations of protons, deuterons and tritons
with alpha particles from spectator decays following 197Au + 197Au collisions
at 1000 MeV per nucleon have been measured with two highly efficient detector
hodoscopes. The constructed correlation functions, interpreted within the
approximation of a simultaneous volume decay, indicate a moderate expansion and
low breakup densities, similar to assumptions made in statistical
multifragmentation models.
PACS numbers: 25.70.Pq, 21.65.+f, 25.70.Mn, 25.75.GzComment: 11 pages, LaTeX with 3 included figures; Also available from
http://www-kp3.gsi.de/www/kp3/aladin_publications.htm
Temperatures of Exploding Nuclei
Breakup temperatures in central collisions of 197Au + 197Au at bombarding
energies E/A = 50 to 200 MeV were determined with two methods. Isotope
temperatures, deduced from double ratios of hydrogen, helium, and lithium
isotopic yields, increase monotonically with bombarding energy from 5 MeV to 12
MeV, in qualitative agreement with a scenario of chemical freeze-out after
adiabatic expansion. Excited-state temperatures, derived from yield ratios of
states in 4He, 5Li, 6Li, and 8Be, are about 5 MeV, independent of the
projectile energy, and seem to reflect the internal temperature of fragments at
their final separation from the system.
PACS numbers: 25.70.Mn, 25.70.Pq, 25.75.-qComment: 10 pages, RevTeX with 4 included figures; Also available from
http://www-kp3.gsi.de/www/kp3/aladin_publications.htm
Breakup Temperature of Target Spectators in Au + Au Collisions at E/A = 1000 MeV
Breakup temperatures were deduced from double ratios of isotope yields for
target spectators produced in the reaction Au + Au at 1000 MeV per nucleon.
Pairs of He and Li isotopes and pairs of He and H
isotopes (p, d and d, t) yield consistent temperatures after feeding
corrections, based on the quantum statistical model, are applied. The
temperatures rise with decreasing impact parameter from 4 MeV for peripheral to
about 10 MeV for the most central collisions.
The good agreement with the breakup temperatures measured previously for
projectile spectators at an incident energy of 600 MeV per nucleon confirms the
observed universality of the spectator decay at relativistic bombarding
energies. The measured temperatures also agree with the breakup temperatures
predicted by the statistical multifragmentation model. For these calculations a
relation between the initial excitation energy and mass was derived which gives
good simultaneous agreement for the fragment charge correlations.
The energy spectra of light charged particles, measured at =
150, exhibit Maxwellian shapes with inverse slope parameters much
higher than the breakup temperatures. The statistical multifragmentation model,
because Coulomb repulsion and sequential decay processes are included, yields
light-particle spectra with inverse slope parameters higher than the breakup
temperatures but considerably below the measured values. The systematic
behavior of the differences suggests that they are caused by
light-charged-particle emission prior to the final breakup stage.
PACS numbers: 25.70.Mn, 25.70.Pq, 25.75.-qComment: 29 pages, TeX with 11 included figures; Revised version accepted for
publication in Z. Phys. A Two additional figure
Mass and Isospin Effects in Multifragmentation
A systematic study of isospin effects in the breakup of projectile spectators
at relativistic energies has been performed with the ALADiN spectrometer at the
GSI laboratory (Darmstadt). Four different projectiles 197Au, 124La, 124Sn and
107Sn, all with an incident energy of 600 AMeV, have been used, thus allowing a
study of various combinations of masses and N/Z ratios in the entrance channel.
The measurement of the momentum vector and of the charge of all projectile
fragments with Z>1 entering the acceptance of the ALADiN magnet has been
performed with the high efficiency and resolution achieved with the TP-MUSIC IV
detector. The Rise and Fall behavior of the mean multiplicity of IMFs as a
function of Zbound and its dependence on the isotopic composition has been
determined for the studied systems. Other observables investigated so far
include mean N/Z values of the emitted light fragments and neutron
multiplicities. Qualitative agreement has been obtained between the observed
gross properties and the predictions of the Statistical Multifragmentation
Model.Comment: 10 pages,7 figure, 18th Nuclear Physics Division Conference of the
EPS, Prague, submitted to Nucl. Phys.
Gross Properties and Isotopic Phenomena in Spectator Fragmentation
A systematic study of isotopic effects in the break-up of projectile
spectators at relativistic energies has been performed with the ALADiN
spectrometer at the GSI laboratory. Searching for signals of criticality in the
fragment production we have applied the model independent universal
fluctuations theory already proposed to track criticality signals in
multifragmentation to our data. The fluctuation of the largest fragment charge
and of the asymmetry of the two and three largest fragments and their bimodal
distribution have also been analysed.Comment: 6 pages, 4 figures, IX International Conference on Nucleus-Nucleus
Collisions, Rio de Janeiro, Brazil, August 28 - September 1, 200
Radon exhalation rate in south-east Sicily building materials
One of the main contributions to indoor radon levels is given by the exhalation from building materials. For this reason we performed measurements of radon exhalation rate in materials commonly used in buildings of the eastern Sicily. The measurements were carried out by using solid state nuclear track detectors in diffusion chambers. We report the results obtained for samples of materials used both for building and for decorating dwellings. The obtained values have shown that building materials commonly used in the eastern Sicily have surface exhalation rates ranging between 1.9 and 43.1 mBq m−2h−1 showing higher values for volcanic materials