48 research outputs found
Dosimetric characterization of a synthetic single crystal diamond detector in a clinical 62 MeV ocular therapy proton beam
A synthetic single crystal diamond based Schottky photodiode was tested at INFN-LNS on the proton beam line (62 MeV) dedicated to the radiation treatment of ocular disease. The diamond detector response was studied in terms of pre-irradiation dose, linearity with dose and dose rate, and angular dependence. Depth dose curves were measured for the 62 MeV pristine proton beam and for three unmodulated range-shifted proton beams; furthermore, the spread-out Bragg peak was measured for a modulated therapeutic proton beam. Beam parameters, recommended by the ICRU report 78, were evaluated to analyze depth-dose curves from diamond detector. Measured dose distributions were compared with the corresponding dose distributions acquired with reference plane-parallel ionization chambers. Field size dependence of the output factor (dose per monitor unit) in a therapeutic modulated proton beam was measured with the diamond detector over the range of ocular proton therapy collimator diameters (5-30 mm). Output factors measured with the diamond detector were compared to the ones by a Markus ionization chamber, a Scanditronix Hi-p Si stereotactic diode and a radiochromic EBT2 film. Signal stability within 0.5% was demonstrated for the diamond detector with no need of any pre-irradiation dose. Dose and dose rate dependence of the diamond response was measured: deviations from linearity resulted to be within ±0.5% over the investigated ranges of 0.5-40.0 Gy and 0.3-30.0 Gy/min respectively. Output factors from diamond detector measured with the smallest collimator (5 mm in diameter) showed a maximum deviation of about 3% with respect to the high resolution radiochromic EBT2 film. Depth-dose curves measured by diamond for unmodulated and modulated beams were in good agreement with those from the reference plane-parallel Markus chamber, with relative differences lower than ±1% in peak-to-plateau ratios, well within experimental uncertainties. A 2.5% variation in diamond detector response was observed in angular dependence measurements carried-out by varying the proton beam incidence angle in the polar direction. The dosimetric characterization of the tested synthetic single crystal diamond detector clearly indicates its suitability for relative dosimetry in ocular therapy proton beams, with no need of any correction factors accounting for dose rate and linear energy transfer dependence
Applying the Disruption Index Procedure to Evaluate the Urban Seismic Risk in the Mt. Etna Area (Italy)
The Disruption Index is used here for the assessment of urban disruption in the Mt. Etna area after a natural disaster. The ïŹrst element of the procedure is the deïŹnition of the seismic input, which is based on information about the historical seismicity and seismogenic faults. The second element is the computation of the seismic impact on the building stock and infrastructure in the
region considered. Information on urban-scale vulnerability was collected and a geographic information system was used to organize the data relating to buildings and network systems (e.g., typologies, schools, strategic structures, lifelines). The central idea underlying the deïŹnition of the Disruption Index is the identiïŹcation and evaluation of the impacts on a target community, considering the physical elements that contribute most to the severe disruption. The results of this study are therefore very useful for earthquake preparedness planning and for the development of strategies to minimize the risks from earthquakes. This study is a product of the European âUrban Disaster Prevention Strategies using Macroseismic Fields and Fault Sourcesâ project (UPStrat-MAFA European project 2013)
Urban seismic risk assessment using the Disruption Index: the case of the volcanic region of Mt. Etna (Italy)
This paper presents the ongoing activities for the assessment of the urban seismic risk at Mt. Etna volcano using the âDisruption Indexâ approach. We use updated information on the historic main seismicity, seismogenic faults and intensity attenuation that in a recent research project produced probabilistic seismic hazard maps and scenarios expressed in terms of macroseismic intensity. To apply the Disruption Index at Etna, we consider a probabilistic approach for seismic hazard evaluation based jointly on macroseismic fields and fault parameters. For information on the urban scale vulnerability, we use a GIS to organise data relating to buildings and network systems (e.g. typologies, schools, strategic structures, lifelines) related to the municipalities more exposed to seismic risk. The convolution of ground motion and vulnerability/ impact is based on a Monte Carlo simulation. We present here some preliminary results on the identification of nodes that are responsible for major disruption in urban systems
Urban seismic risk assessment using the Disruption Index: the case of the volcanic region of Mt. Etna (Italy)
This paper presents the ongoing activities for the assessment of the urban seismic risk at Mt. Etna volcano using the âDisruption Indexâ approach. We use updated information on the historic main seismicity, seismogenic faults and intensity attenuation that in a recent research project produced probabilistic seismic hazard maps and scenarios expressed in terms of macroseismic intensity. To apply the Disruption Index at Etna, we consider a probabilistic approach for seismic hazard evaluation based jointly on macroseismic fields and fault parameters. For information on the urban scale vulnerability, we use a GIS to organise data relating to buildings and network systems (e.g. typologies, schools, strategic structures, lifelines) related to the municipalities more exposed to seismic risk. The convolution of ground motion and vulnerability/ impact is based on a Monte Carlo simulation. We present here some preliminary results on the identification of nodes that are responsible for major disruption in urban systems.Co-financed by the EU - Civil Protection Financial Instrument, in the framework the European project âUrban disaster Prevention Strategies using MAcroseismic Fields and FAult Sources (Acronym: UPStrat-MAFA, Grant Agreement N. 23031/2011/613486/SUB/A5). http://ec.europa.eu/echo/funding/cp_projects2011_en.htmPublishedLisbon - Portugal4.1. Metodologie sismologiche per l'ingegneria sismicaope
DIAMOND DETECTORS FOR CHARACTERIZATION OF LASER-GENERATED PLASMA
Abstract -CVD mono-crystalline diamond films were employed as detectors of the Introduction -Laser-generated plasma is characterized by high temperature and density
Lambda Hyperons in 2 A*GeV Ni + Cu Collisions
A sample of Lambda's produced in 2 A*GeV Ni + Cu collisions has been obtained
with the EOS Time Projection Chamber at the Bevalac. Low background in the
invariant mass distribution allows for the unambiguous demonstration of Lambda
directed flow. The transverse mass spectrum at mid-rapidity has the
characteristic shoulder-arm shape of particles undergoing radial transverse
expansion. A linear dependence of Lambda multiplicity on impact parameter is
observed, from which a total Lambda + Sigma^0 production cross section of $112
+/- 24 mb is deduced. Detailed comparisons with the ARC and RVUU models are
made.Comment: Revised version accepted for publication in Phys. Lett.
Rn contamination mechanisms on acrylic surfaces
In this work, the Rn contamination mechanisms on acrylic surfaces
have been investigated. Rn can represent a significant background
source for low-background experiments, and acrylic is a suitable material for
detector design thanks to its purity and transparency. Four acrylic samples
have been exposed to a Rn rich environment for different time periods,
being contaminated by Rn and its progenies. Subsequently, the time
evolution of radiocontaminants activity on the samples has been evaluated with
and measurements, highlighting the role of different decay
modes in the contamination process. A detailed analysis of the alpha spectra
allowed to quantify the implantation depth of the contaminants. Moreover, a
study of both and measurements pointed out the Rn
diffusion inside the samples
TOMO-ETNA experiment at Etna volcano: Activities on land
In the present paper we describe the on-land field operations integrated in
the TOMO-ETNA experiment carried out in June-November 2014 at Mt.
Etna volcano and surrounding areas. This terrestrial campaign consists
in the deployment of 90 short-period portable three-component seismic
stations, 17 broadband seismometers and the coordination with 133 permanent
seismic station belonging to Italyâs Istituto Nazionale di Geofisica
e Vulcanologia (INGV). This temporary seismic network recorded active
and passive seismic sources. Active seismic sources were generated
by an array of air-guns mounted in the Spanish oceanographic vessel
âSarmiento de Gamboaâ with a power capacity of up to 5200 cubic
inches. In total more than 26,000 shots were fired and more than 450 local
and regional earthquakes were recorded. We describe the whole technical
procedure followed to guarantee the success of this complex seismic experiment.
We started with the description of the location of the potential
safety places to deploy the portable network and the products derived from
this search (a large document including full characterization of the sites,
owners and indication of how to arrive to them). A full technical description
of the seismometers and seismic sources is presented. We show
how the portable seismic network was deployed, maintained and recovered
in different stages. The large international collaboration of this experiment
is reflected in the participation of more than 75 researchers,
technicians and students from different institutions and countries in the
on-land activities. The main objectives of the experiment were achieved
with great success.PublishedS04272SR. VULCANI - Servizi e ricerca per la SocietĂ JCR Journalope
Lâindagine macrosismica: metodologia, parametri del terremoto, questioni aperte
Subito dopo lâevento del 6 aprile 2009, come di consueto Ăš stata realizzata una lunga e complessa indagine macrosismica, promossa dal gruppo operativo QUEST, che ha avuto inizialmente lâobiettivo di delimitare lâarea di danneggiamento, a supporto delle attivitĂ di pronto intervento della Protezione Civile, e successivamente quello di classificare nel modo piĂč accurato e capillare possibile, gli effetti prodotti dallâevento, particolarmente nelle aree danneggiate.
A questo scopo Ăš stata prodotta una stima utilizzando la scala MCS (Sieberg, 1930); in un secondo momento Ăš stata rifinita lâindagine per una cinquantina di localitĂ dellâarea maggiormente danneggiata (Is MCS>VII), raccogliendo ed elaborando i dati in termini di scala macrosismica EMS98 (GrĂŒnthal, 1998).
Per la complessitĂ e la dimensione dei problemi affrontati, questo terremoto ha costituito un banco di prova di grande importanza per la macrosismologia italiana.
In questo testo viene descritto il lavoro realizzato, discutendo in particolare alcuni aspetti che hanno messo alla prova le metodologie di indagine tradizionali (sistematiche irregolaritĂ degli insediamenti monitorati, forti divergenze degli scenari di danno rispetto a quelli previsti dalle scale, difficile comparabilitĂ con scenari storici, ecc.) e presentandone i risultati, in relazione ai parametri epicentrali che ne risultano e il loro contributo piĂč diretto alla comprensione complessiva della sismicitĂ dellâarea
A study of the radiation tolerance of cvd diamond to 70 mev protons, fast neutrons and 200 mev pions
We measured the radiation tolerance of commercially available diamonds grown by the Chemical Vapor Deposition process by measuring the charge created by a 120 GeV hadron beam in a 50 ÎŒm pitch strip detector fabricated on each diamond sample before and after irradiation. We irradiated one group of samples with 70 MeV protons, a second group of samples with fast reactor neutrons (defined as energy greater than 0.1 MeV), and a third group of samples with 200 MeV pions, in steps, to (8.8±0.9) Ă 10 protons/cm, (1.43±0.14) Ă 10 neutrons/cm, and (6.5±1.4) Ă 1014 pions/cm, respectively. By observing the charge induced due to the separation of electronâhole pairs created by the passage of the hadron beam through each sample, on an event-by-event basis, as a function of irradiation fluence, we conclude all datasets can be described by a first-order damage equation and independently calculate the damage constant for 70 MeV protons, fast reactor neutrons, and 200 MeV pions. We find the damage constant for diamond irradiated with 70 MeV protons to be 1.62±0.07(stat)±0.16(syst)Ă 10â18 cm/(pÎŒm), the damage constant for diamond irradiated with fast reactor neutrons to be 2.65±0.13(stat)±0.18(syst)Ă 10â18 cm/(nÎŒm), and the damage constant for diamond irradiated with 200 MeV pions to be 2.0±0.2(stat)±0.5(syst)Ă 10â18 cm/(ÏÎŒm). The damage constants from this measurement were analyzed together with our previously published 24 GeV proton irradiation and 800 MeV proton irradiation damage constant data to derive the first comprehensive set of relative damage constants for Chemical Vapor Deposition diamond. We find 70 MeV protons are 2.60 ± 0.29 times more damaging than 24 GeV protons, fast reactor neutrons are 4.3 ± 0.4 times more damaging than 24 GeV protons, and 200 MeV pions are 3.2 ± 0.8 more damaging than 24 GeV protons. We also observe the measured data can be described by a universal damage curve for all proton, neutron, and pion irradiations we performed of Chemical Vapor Deposition diamond. Finally, we confirm the spatial uniformity of the collected charge increases with fluence for polycrystalline Chemical Vapor Deposition diamond, and this effect can also be described by a universal curve