Search results for: P.J. Iunes

Items from 1 to 20 out of 42 results

article

A comparison between neutron-fluence measurements using metal-activation monitors and standard glasses calibrated via thin uranium-fission monitors and via ηq method

E.A.C. Curvo, R. Jonckheere, S. Guedes, P.J. Iunes, more

Radiation Measurements > 2013 > 53-54 > Complete > 38-44

The two fundamental approaches to fission-track dating involve either an explicit determination of the thermal neutron fluence (φ-method) or a calibration against age standards (ζ-method). The neutron fluence measurements are carried out with metal-activation monitors or with uranium-fission monitors, co-irradiated with the samples. Uranium-fission monitors consist of either a thin “mono-atomic”)...

article

Anisotropy of track revelation in epidote: Results of a step etching experiment with 86Kr ion tracks

E.A.C. Curvo, S. Guedes, I. Alencar, W.M. Nakasuga, more

Radiation Measurements > 2011 > 46 > 8 > 722-725

Epidote etching anisotropy has been studied through step etching of ⁸⁶ Kr (300 MeV) ion tracks. A slice of epidote natural monocrystal was taken from the (010) plane and then divided into five pieces. Each piece was then irradiated with ions whose incidence angles (zenith angles) were of 15°, 30°, 45°, 60° and 75° with respect to y-axis. The azimuthal angle of incidence of the ions was the...

article

Fission track and U–Pb in situ dating applied to detrital zircon from the Vale do Rio do Peixe Formation, Bauru Group, Brazil

A.N.C. Dias, C.A.S. Tello, F. Chemale, M.C.T.F. de Godoy, more

Journal of South American Earth Sciences > 2011 > 31 > 2-3 > 298-305

Combined methods of fission track (FTM) and U–Pb in situ zircon dating were applied to sedimentary samples from the Vale do Rio do Peixe Formation, Bauru Basin, Brazil. Detrital zircons of nine samples were determined by the FTM, and the obtained ages varied from 239 Ma–825 Ma, which can be grouped into four main populations as the 230–300 Ma, 460–490 Ma, 500–650 Ma and 696–825 Ma groups. The U–Pb...

article

CR-39 alpha particle spectrometry for the separation of the radon decay product 214Po from the thoron decay product 212Po

N.F. Santos, P.J. Iunes, S.R. Paulo, S. Guedes, more

Radiation Measurements > 2010 > 45 > 7 > 823-826

In this work, it is presented an experimental assembly based on electric capture of radionuclides in order to discriminate the alpha activity of ²¹⁴ Po (radon decay product) from ²¹² Po (thoron decay product) one. The alpha activity was registered with CR-39 analyzing etch pit diameters and optical density. This discrimination may allow for the estimation of the relative contribution...

article

Fission track chemical etching kinetic model

P.A.F.P. Moreira, S. Guedes, P.J. Iunes, J.C. Hadler

Radiation Measurements > 2010 > 45 > 2 > 157-162

In fission track thermochronology (FTT) latent fission tracks can be observed under the optical microscope only after chemical etching. The understanding of the etching process in the origin of this track is important for fission track annealing models. This may allow the determination of parameters related to etching kinetics independently of the models fit to the annealing data. In this work, a...

article

Experimental study of a methodology for Fission-track Dating without neutron irradiation

J.C. Hadler, P.J. Iunes, C.A. Tello, F. Chemale, more

Radiation Measurements > 2009 > 44 > 9-10 > 955-957

To carry out the dating by the Fission Track Method (FTM) the international community that works with this method employs methodologies in which the mineral to be dated must be irradiated with neutrons. Such irradiation, performed in a nuclear reactor, demand a relatively long waiting time so that the activity of the sample attain a proper level for handling. The present work aims to establish a methodology...

article

Glass fission track analysis by AFM and SEM: Inferring latent track structure through etched tracks

J.C. Hadler, I. Alencar, P.J. Iunes, S. Guedes

Radiation Measurements > 2009 > 44 > 9-10 > 746-749

The main goal of this work is the study of latent fission track structure (or the associated defects density) analyzing the geometry evolution of etched tracks. In this way, measurements of diameter and cone angle for ²³⁵ U fission tracks reaching soda-lime glass surface with normal incidence were made. These glasses were etched since very short etching time up to times around standard etching...

article

Comparison between thorium and uranium fission track diameters in glass

P.A.F.P. Moreira, P.J. Iunes, S. Guedes, J.C. Hadler

Radiation Measurements > 2008 > 43 > Supplement 1 > S329-S333

Comparisons between diameters of uranium and thorium neutron induced fission tracks in glass made possible to test indirectly the hypothesis that observation efficiency of spontaneous ²³⁸ U and induced ²³⁵ U fission tracks may be considered the same. The sources of fission fragments were uranium and thorium thin films irradiated with neutrons with and without Cd-cover. After irradiation,...

article

Group analysis method for fission track thermochronology

J.C. Hadler, P.J. Iunes, C.A. Tello, S. Guedes

Radiation Measurements > 2008 > 43 > Supplement 1 > S163-S168

A methodology to obtain ages and thermal histories of sets of apatite samples from localities with geologically compatible characteristics is described. A methodology exploring the fact that samples with similar geological characteristics should present the same thermal history is proposed. This approach can contribute for the obtainment of more conclusive results by analysing fewer samples than it...

article

Indoor radon and radon progeny survey at Campinas—Brazil using CR-39: Final results

J.C. Hadler, R.S. Neman, P.J. Iunes, O.L.S. Pereira, more

Radiation Measurements > 2008 > 43 > Supplement 1 > S440-S444

In a survey performed at Campinas-SP, Brazil, the CR-39 detector was used as an alpha-spectrometer taking into account the size and the gray level of round tracks measured under an automatic optical microscopy system. The exposures were carried out in the same room of 70 dwellings during two successive periods of six months: the first one from November 1996 to May 1997 (summer exposure) and the second...

article

On energy absorption effects in uranium and thorium thin films

J.C. Hadler, P.J. Iunes, G. Bigazzi, S.R. Paulo

Radiation Measurements > 2008 > 43 > Supplement 1 > S334-S336

The use of U and Th thin films, attached to detectors of fission tracks, allows determining the neutron fluence in nuclear reactors. In principle, the parameters involved in neutron fluence determinations through U and Th thin films that might be influenced by effects related with fission fragments and α particle energy absorption are: (i) the detection efficiency of nuclear emulsions for α particles,...

article

Projected-length distributions of fission-fragment tracks from U and Th thin film sources in muscovite

S. Guedes, R. Jonckheere, P.J. Iunes, J.C. Hadler

Nuclear Inst. and Methods in Physics Research, B > 2008 > 266 > 5 > 786-790

Thin films of natural uranium and thorium deposited on muscovite were used as sources of neutron-induced fission fragments. Fragment energy loss in thin-source geometry is negligible. In this way, the observed fragment range results from the interaction of the fragment with the detector material. This characteristic enables the investigation of asymmetric fission and etching, through measurements...

article

Comparison of population and external detector method dating in epidote

E.A.C. Curvo, P.J. Iunes, S. Guedes, R. Palissari, more

Radiation Measurements > 2007 > 42 > 8 > 1307-1314

Epidote fission-track dating (FTD) was performed through both population and external detector method (EDM) in five samples from the Mantiqueira Mountain range, southwestern Brazil. The ages obtained via population conducted to a weighted mean age of (114±19)Ma. In order to perform EDM dating, it was necessary to measure the efficiency factor (g) between muscovite mica and epidote. Three measurements...

article

Kinetic model for the annealing of fission tracks in minerals and its application to apatite

S. Guedes, J.C. Hadler N, K.M.G. Oliveira, P.A.F.P. Moreira, more

Radiation Measurements > 2006 > 41 > 4 > 392-398

Fission tracks are formed in apatite and other minerals after the passage of fission fragments, which deliver locally intense amounts of energy to the crystal lattice. It is well known that the observable mean track lengths are reduced due to thermal treatment. If the annealing kinetics are known, it is sometimes possible to infer the thermal history a given sample experienced. Given the present lack...

article

On indoor radon daughters’ plate-out on material surfaces

R. Neman, J.C. Hadler N, P.J. Iunes, S.R. Paulo

Radiation Measurements > 2005 > 39 > 6 > 653-655

In this work, the plate-out of radon daughters on surfaces of different sizes has been studied. Several pieces of CR-39, cut circularly with different diameters, were exposed for approximately 3 months in an indoor environment containing a high concentration of uranium in Pocos de Caldas, Brazil. During the exposition the CR-39 sheets remained fixed in a wire far from any object. After the exposition,...

article

The use of apatite fission track thermochronology to constrain fault movements and sedimentary basin evolution in northeastern Brazil

M.A. da Nóbrega, J.M. Sá, F.H.R. Bezerra, J.C. Hadler Neto, more

Radiation Measurements > 2005 > 39 > 6 > 627-633

An apatite fission track study of crystalline rocks underlying sedimentary basins in northeastern Brazil indicate that crustal blocks that occur on opposite sides of a geological fault experienced different thermal histories. Samples collected on the West block yielded corrected fission-track ages from 140 to 375Ma, whereas samples collected on the East block yielded ages between 90 and 125Ma. The...

article

Fission-track dating of South American natural glasses: an overview

G. Bigazzi, J.C. Hadler Neto, P.J. Iunes, A.M. Osório Araya

Radiation Measurements > 2005 > 39 > 6 > 585-594

Although many glass-bearing horizons can be found in South American volcanic complexes or sedimentary series, only a relatively few tephra and obsidian-bearing volcanic fields have been studied using the fission-track (FT) dating method. Among them, the volcanics located in the Sierra de Guamaní (east of Quito, Ecuador) were studied by several authors. Based upon their ages, obsidians group into three...

article

Radon surveys in Brazil using CR-39

S.R. Paulo, R. Neman, J.C. Hadler Neto, P.J. Iunes, more

Radiation Measurements > 2005 > 39 > 6 > 657-660

In this work results of two radon daughters survey in Brazil are presented and discussed. Some methodological problems concerning the first survey are pointed out which were corrected for the second survey in order to make a realistic long-term measurement of radon decay products in the air. The technique employed in both surveys was the alpha-spectroscopy using CR-39. The reliability of this technique...

article

On epidote fission track dating

E.A.C. Curvo, J.C. Hadler Neto, P.J. Iunes, S. Guedes, more

Radiation Measurements > 2005 > 39 > 6 > 641-645

The use of epidote in fission track dating was abandoned since the beginning of the 1980s due to difficulties like absence of a standard etching procedure, obtainment of different closure temperatures and the percentage of the datable samples. The results become much more reproducible when restricting fission track analysis to a peculiar kind of track. We are also studying confined track length, what...

article

Thermotectonic and fault dynamic analysis of Precambrian basement and tectonic constraints with the Parana basin

L.F.B. Ribeiro, P.C. Hackspacher, M.C.S. Ribeiro, J.C. Hadler Neto, more

Radiation Measurements > 2005 > 39 > 6 > 669-673

The Precambrian crystalline basement of southeast Brazil is affected by many Phanerozoic reactivations of shear zones that developed during the end of the Neoproterozoic in the Brasiliano orogeny. These reactivations with specific tectonic events, a multidisciplinary study was done, involving geology, paleostress, and structural analysis of faults, associated with apatite fission track methods along...

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Keywords

CR-39 (6)
FISSION-TRACK DATING (6)
APATITE (5)
FISSION TRACK DATING (5)
NEUTRON DOSIMETRY (5)
RADON (5)
ANNEALING (4)
FISSION TRACK (4)
FISSION TRACKS (4)
RADON DAUGHTERS (4)
DURANGO APATITE (3)
GLASS (3)
MODEL (3)
THERMOCHRONOLOGY (3)
BRAZIL (2)
DIFFUSION (2)
EPIDOTE (2)
FISSION-TRACK ANALYSIS (2)
MUSCOVITE (2)
PLATE-OUT (2)
SOUTHEAST BRAZIL (2)
SURVEY (2)
TH THIN FILM (2)
THERMAL HISTORIES (2)
THORIUM (2)
THORIUM THIN FILMS (2)
U THIN FILM (2)
URANIUM (2)
URANIUM THIN FILMS (2)
2 3 8 U (1)
212PO (1)
214PO (1)
232TH (1)
235U (1)
238U SPONTANEOUS FISSION (1)
ACTIVATED CHARCOAL (1)
AFM (1)
AGE CORRECTION (1)
ALPHA PARTICLES (1)
ALPHA SPECTROSCOPY (1)
ALUMINUM DOSIMETER (1)
ANISOTROPY (1)
APATITE THERMAL HISTORY (1)
BAURU GROUP (1)
BORBOREMA PROVINCE—BRAZIL (1)
BREJUÍ EPIDOTE (1)
CHEMICAL ETCHING (1)
COMPUTATIONAL SIMULATION (1)
D-OPTIMAL (1)
DECAY CONSTANT (1)
DETECTION EFFICIENCY (1)
DETECTION METHODOLOGIES (1)
ETCHING (1)
EXPERIMENTAL DESIGN (1)
FISSION FRAGMENTS (1)
FISSION TRACK METHOD (1)
FISSION-TRACK (1)
FISSION-TRACK METHOD (1)
GEOLOGICAL FAULT (1)
ICP/MS (1)
INDOOR RADON (1)
INDOOR RADON MONITORING (1)
INDUCED FISSION (1)
ION TRACKS (1)
LATIN AMERICAN COUNTRIES (1)
MACUSANITE (1)
MEAN DIAMETER (1)
MEASUREMENT ASSEMBLY (1)
METAL-ACTIVATION MONITORS (1)
MOLDAVITE (1)
NEUTRON FLUENCE (1)
NRPB–SSI DOSIMETER (1)
OBSERVATION EFFICIENCY (1)
OBSIDIAN PROVENANCE STUDIES (1)
PARANA BASIN (1)
PARTICLE TRACK DETECTOR (1)
PLATE-OUT EFFECT (1)
PLATEAU CORRECTION (1)
POTENTIAL BARRIER (1)
RADON DAUGHTERS SURVEY (1)
RADON PROGENY (1)
REACTIVATIONS (1)
SEDIMENTARY BASIN (1)
SEM (1)
SIZE CORRECTION (1)
SOFTWARE (1)
SOLID-STATE NUCLEAR TRACK DETECTORS (1)
SPONTANEOUS FISSION (1)
STEP ETCHING (1)
SUPERFICIAL TRACK DENSITY AND CHEMICAL ETCHING (1)
SURFACE DENSITY (1)
TECTONICS (1)
TEPHROCHRONOLOGY (1)
TH/U RATIO (1)
THERMAL NEUTRON FLUENCE (1)
THERMOCHRONOLOGY IN BRAZIL (1)
THIN FILM (1)
THIN FILMS (1)
THORIUM THIN FILM (1)
THORON (1)
more

INFONA - science communication portal

Search results for: P.J. Iunes

A comparison between neutron-fluence measurements using metal-activation monitors and standard glasses calibrated via thin uranium-fission monitors and via ηq method

Anisotropy of track revelation in epidote: Results of a step etching experiment with 86Kr ion tracks

Fission track and U–Pb in situ dating applied to detrital zircon from the Vale do Rio do Peixe Formation, Bauru Group, Brazil

CR-39 alpha particle spectrometry for the separation of the radon decay product 214Po from the thoron decay product 212Po

Fission track chemical etching kinetic model

Experimental study of a methodology for Fission-track Dating without neutron irradiation

Glass fission track analysis by AFM and SEM: Inferring latent track structure through etched tracks

Comparison between thorium and uranium fission track diameters in glass

Group analysis method for fission track thermochronology

Indoor radon and radon progeny survey at Campinas—Brazil using CR-39: Final results

On energy absorption effects in uranium and thorium thin films

Projected-length distributions of fission-fragment tracks from U and Th thin film sources in muscovite

Comparison of population and external detector method dating in epidote

Kinetic model for the annealing of fission tracks in minerals and its application to apatite

On indoor radon daughters’ plate-out on material surfaces

The use of apatite fission track thermochronology to constrain fault movements and sedimentary basin evolution in northeastern Brazil

Fission-track dating of South American natural glasses: an overview

Radon surveys in Brazil using CR-39

On epidote fission track dating

Thermotectonic and fault dynamic analysis of Precambrian basement and tectonic constraints with the Parana basin

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