A. Etchegoyen

A water tank Cherenkov detector for very high-energy astroparticles

Abstract Extensive airshower detection is an important issue in current astrophysics endeavours. Surface arrays detectors are a common practice since they are easy to handle and have a 100% duty cycle. In this work we present an experimental study of the parameters relevant to the design of a water Cherenkov detector for high-energy airshowers. This detector is conceived as part of the surface array of the Pierre Auger Project, which is expected to be sensitive to ultra high-energy cosmic rays. In this paper we focus our attention in the geometry of the tank and its inner liner material, discussing pulse shapes and charge collections.

The AMS program at the TANDAR accelerator

Abstract The accelerator mass spectrometry (AMS) program that is under development using the 20UD electrostatic accelerator TANDAR at Buenos Aires is presented. Tests and measurements in order to evaluate and to improve the accelerator performance are described. Preliminary measurements have been done by tuning 14C beams using as detection system a ΔE-ER telescope. For the detection of heavier isotopes some new developments are being currently implemented in a quadrupole-dipole-dipole (QDD) magnetic spectrometer. Furthermore, work is in progress to construct a time-of-flight system using two micro-channel plates prior to the entrance to the QDD spectrometer.

DEVELOPMENTS OF AMS AT THE TANDAR ACCELERATOR

Abstract Man-made long-lived radioisotopes have been produced as a result of different nuclear technologies. The study of accidental spillages and the determination of radioisotope concentrations in nuclear waste prior to final storage in a repository are subjects of great interest in connection with this activity. The accelerator mass spectrometry (AMS) technique is a powerful tool to measure long-lived isotopes at abundance ratios as low as 10−12–10−15 in small samples. Applications to the Argentine nuclear program like those mentioned above, as well as applications to archaeology, hydrology and biomedical research, are considered in an AMS program using the TANDAR 20 UD electrostatic accelerator at Buenos Aires. In this work we present the status of the program and a description of the facility.

Improved beam-energy calibration technique for heavy-ion accelerators

Abstract A simple technique for beam energy calibration of heavy-ion accelerators is presented. A thin hydrogenous target was bombarded with 12C and 19F and the energies of the protons knocked out, elastically were measured at several angles using two detectors placed at equal angles on opposite sides of the beam. The use of these two detectors cancels the largest errors due to uncertainties in the angle and position at which the beam hits the target. An application of this energy calibration method to an electrostatic accelerator is described and the calibration constant of the analyzing magnet was obtained with an estimated error of 0.4%.

Near-barrier transfer in16O +144, 154Sm

The production of nitrogen and carbon fragments in the reactions induced by16O on144Sm and154Sm targets was studied at two bombarding energies (65 MeV and 72 MeV) around the interaction barrier. The measured angular distributions exhibit the characteristic behaviour of direct transfer reactions, and theQ-value spectra are typically centered at the values predicted by kinematic selectivity. The comparison between fusion and charged-particle transfer cross sections shows that whereas fusion is the most important process at the highest bombarding energy, transfer reactions become comparable or even dominant (as in the144Sm case) at near-barrier energies. The different transfer probabilities observed for the two systems are analyzed in terms of nuclear deformation.

Scattering, fusion and transfer reactions in 16O + ASm at energies close to the Coulomb barrier

Abstract Recently measured scattering cross sections for the 16 O + 144 Sm system allow to extract a bare potential which is used in a global analysis of scattering, fusion and transfer experimental data for 16 O on different samarium isotopes at energies close to the Coulomb barrier. The analysis is done within the framework of an extension of a method based on the intrinsic-coordinate-dependent phase shifts and the equivalent-spheres formalisms which has been previously reported. Consistent fits are obtained for an important amount of data covering a wide range of target deformations, bombarding energies and scattering angles for different reaction channels. As a significant exception, the fusion excitation function for 144 Sm is overestimated.