Laboratori Nazionali Di Legnaro Research Articles

Realization and simulations of the new SPES Beam Cooler

One of the aim of the new project Selective Production of Exotic Species (SPES) is to produce and select new, neutron reach, isotopes [1,2,3,4]. The technique adopted to produce these species is the Isotope Selection On Line (ISOL) that postpones the separation of the isotopes after the beam production, using a High-Resolution Mass Spectrometer (HRMS).In order to allow a good separation of isotopes , the transverse emittance and the energy spread of the beam should have very low values, for this reason the Beam Cooler (BC) is located between the ISOL target, i.e. the beam source, and the HRMS.In the SPES project, where heavy isotopes are expected (mass number >100), the spectrometer resolution must be preferably higher than dm/m = 5 × 10-5 and thus the features of the beam at the entrance of the HRMS should be at least εn 95% < 8.3 × 10-3 π mm mrad and σE < 1.5 eV.BC devices are devoted to improve the beam features in terms of emittance and energy spread. A new BC has been designed and realized by the Laboratoire de Physique Corpuscolaire (LPC) at Caen, France, for the SPES facility at Laboratori Nazionali di Legnaro (LNL), near Padova, Italy.BCs cool down the beam thanks to a dissipative process in which the thermal energy passes from the beam ions to another medium whose constituent is typically much lighter, Helium gas in our case. This process takes place inside a confinement system that on the one hand to limit the spread of the cooling medium, and on the other to allow the beam to continue along the required trajectory, in the presented device it is a row of radio frequency quadrupoles in an almost closed chamber.Some specifications of the BC described in this document: the RFQ is 723 mm long, its internal radius is 5 mm; the RFQ is included in the gas chamber which is 730 mm×280 mm×220 mm. Before it there is the injection part composed by, following the beam trajectory, a grounded pipe (388 mm long) and three focusing electrodes. On the opposite side there is the extraction part with two focusing electrodes.This document presents the main features of the new BC together with the results of a preliminary study where the beam dynamic has been simulated. The analysis embeds also the investigation of the gas distribution inside and outside the BC.The beam dynamic simulations are based on the Simion code [5] while the estimation of the gas distribution is computed with MolFlow+ [6].Simulations show that accurately setting the BC leads to a large improvement of the emittance while the energy spread still needs to be improved. Limiting the gas pressure in the acceleration zone seems to allow the required final boost.

Conceptual design of the AGATA 2[formula omitted] array at LNL

The Advanced GAmma Tracking Array (AGATA) has been installed at Laboratori Nazionali di Legnaro (LNL), Italy. In this installation, AGATA will consist, at the beginning, of 13 AGATA triple clusters (ATCs) with an angular coverage of 1π, and progressively the number of ATCs will increase up to a 2π angular coverage. This setup will exploit both stable and radioactive ion beams delivered by the Tandem–PIAVE-ALPI accelerator complex and the SPES facility. The new implementation of AGATA at LNL will be used in two different configurations, firstly one coupled to the PRISMA large-acceptance magnetic spectrometer and lately a second one at Zero Degrees, along the beam line. These two configurations will allow us to cover a broad physics program, using different reaction mechanisms, such as Coulomb excitation, fusion-evaporation, transfer and fission at energies close to the Coulomb barrier. These setups have been designed to be coupled with a large variety of complementary detectors such as charged particle detectors, neutron detectors, heavy-ion detectors, high-energy γ-ray arrays, cryogenic and gasjet targets and the plunger device for lifetime measurements. We present in this paper the conceptual design, characteristics and performance figures of this implementation of AGATA at LNL.

Lifetime measurements using a plunger device and the EUCLIDES Si array at the GALILEO [formula omitted]-ray spectrometer

The GALILEO γ-ray spectrometer, installed at the Laboratori Nazionali di Legnaro (LNL), benefits from intense stable beams provided by the Tandem-ALPI-PIAVE accelerator complex and from radioactive beams to be delivered in the near future by the SPES facility. The spectrometer is complemented with a variety of ancillary devices to allow for nuclear structure and reaction studies. The 4π Si-ball array EUCLIDES coupled to the GALILEO γ-ray spectrometer represents one of the commonly used setup for experiments aiming at spectroscopic studies. High-efficiency detection of light-charged particles in a fusion–evaporation reaction guarantees good discrimination of different reaction channels and provides essential information for the kinematic reconstruction. In this paper we discuss a configuration of the EUCLIDES array developed for the lifetime measurements of nuclear excited states populated in a fusion–evaporation reaction. In such a configuration a part of the EUCLIDES detectors is disassembled allowing for the installation of a plunger device in the reaction chamber. The reduced configuration of EUCLIDES provides high detection efficiency necessary for reliable light charged-particle discrimination. We report on the commissioning experiment focused on the 58Ni(58Ni,3p)113I reaction. The lifetimes of 11/2− and 15/2− states were measured by applying the Recoil Distance Doppler Shift method to be equal to 206(20) ps and 7.9(12) ps correspondingly and were in good agreement with the values cited in the literature. Thus, the combination of the GALILEO and EUCLIDES arrays, and the plunger device has resulted in a powerful experimental setup to determine lifetimes of excited states in neutron-deficient nuclei in the picosecond range.

Coulomb excitation studies at LNL with the SPIDER-GALILEO set-up

Low-energy Coulomb excitation is one of the simplest and most known tools to study the nuclear shape; for this reason it is nowadays widely used at radioactive beam facilities. The Selective Production of Exotic Species (SPES) facility, for the acceleration of radioactive beams will soon provide the first exotic beams at the Laboratori Nazionali di Legnaro (LNL) in Italy. To this end a new particle detector (Silicon PIe DEtectoR) to be used for Coulomb excitation studies has been installed at LNL. SPIDER has been coupled to the GALILEO array of germanium detectors, and a number of experiments have been already successfully performed. This paves the way for future experiments with the radioactive beams provided by the SPES facility.

A new dedicated plunger device for the GALILEO [formula omitted]-ray detector array

A new device, the GALILEO plunger, has been developed for lifetime measurement studies using the GALILEO γ-ray detector array at the Laboratori Nazionali di Legnaro (LNL) in Legnaro, Italy. This plunger device holds two stretched metal foils in the beam path for the use of the recoil distance Doppler-shift technique in order to measure lifetimes of nuclear excited states in the range of 1 ps to 1 ns. The compact design allows one to combine different auxiliary detectors with the plunger device inside the target chamber and takes care of high γ-ray transparency. The design and control of the device are presented in this paper, together with lifetimes of excited states in 180Pt measured within the first in-beam commissioning run.

Innovative remotely-controlled bending device for thin silicon and germanium crystals

Steering of negatively charged particle beams below 1 GeV has demonstrated to be possible with thin bent silicon and germanium crystals. A newly designed mechanical holder was used for bending crystals, since it allows a remotely-controlled adjustment of crystal bending and compensation of unwanted torsion. Bent crystals were installed and tested at the MAMI Mainz MIcrotron to achieve steering of 0.855-GeV electrons at different bending radii. We report the description and characterization of the innovative bending device developed at INFN Laboratori Nazionali di Legnaro (LNL).

Use of the facility EXOTIC for fusion–evaporation studies

The EXOTIC facility was developed to produce light radioactive beams and it is installed at Laboratori Nazionali di Legnaro (LNL) of INFN. We have explored the capabilities of EXOTIC as a beam separator for studies of heavy ion fusion–evaporation reactions. For this purpose, the facility has been slightly modified to allow the detection and identification of the fusion–evaporation residues (ER). We have measured fusion reactions for the two systems 32S + 48Ca and 32S + 64Ni where the cross sections are known from previous experiments at LNL. The ion optical parameters of EXOTIC have been set to maximize the ER yield in the detector system for the various cases. A good and clean separation of the ER from beam-like particles was obtained in the experimental Energy–Time of Flight correlation plots. These encouraging results have been compared with the performance of the electrostatic deflector set-up PISOLO, routinely used at LNL for sub-barrier fusion experiments. The beam rejection factor of EXOTIC at 0°is comparable to the one of PISOLO at 2°–3°, while a gain of overall efficiency up to a factor 3 has been obtained with EXOTIC. We briefly discuss possible ways of improving these results.

The SPES High Power ISOL production target

SPES (Selective Production of Exotic Species) is a facility under construction at INFN-LNL (Istituto Nazionale di Fisica Nucleare - Laboratori Nazionali di Legnaro), aimed to produce intense neutron-rich radioactive ion beams (RIBs). These will be obtained using the ISOL (Isotope Separation On-Line) method, bombarding a uranium carbide target with a proton beam of 40MeV energy and currents up to 200 μA. The target configuration was designed to obtain a high number of fissions, up to 1013 per second, low power deposition and fast release of the produced isotopes. The exotic isotopes generated in the target are ionized, mass separated and re-accelerated by the ALPI superconducting LINAC at energies of 10AMeV and higher, for masses in the region of A = 130amu, with an expected rate on the secondary target up to 109 particles per second. In this work, recent results on the R&D activities regarding the SPES RIB production target-ion source system are reported.

X-band accelerator structures: On going R&D at the INFN

The next generation of accelerators, from the compact to the large infrastructure dedicated to high energy physics, is highly demanding in terms of accelerating gradients. To upgrade performances of X band linacs at 11.424GHz many resources are devoted to achieve high accelerating gradients and at the same time to obtain a high reliability. In the framework of a three-year funded project by the Vth Committee of the INFN to the Laboratori Nazionali di Frascati (LNF) and to the Laboratori Nazionali di Legnaro (LNL). Within a broad international collaboration the LNF has been involved in the design, manufacture and test of compact high power standing wave (SW) sections operating at high frequency while LNL is actively involved in the development of new materials and multilayers using PVD (Physical Vapor Deposition) methods. We will report about the status of the accelerating device and of the different ongoing R&D activities and characterization procedures such as tests of different materials and metallic coatings.

Cryogenic Control System Migration and Developments towards the UNICOS CERN Standard at INFN

The cryogenic control systems at Laboratori Nazionali di Legnaro (LNL) are undergoing an important and radical modernization, allowing all the plants controls and supervision systems to be renewed in a homogeneous way towards the CERN-UNICOS standard. Before the UNICOS migration project started there were as many as 7 different types of PLC and 7 different types of SCADA, each one requiring its own particular programming language. In these conditions, even a simple modification and/or integration on the program or on the supervision, required the intervention of a system integrator company, specialized in its specific control system. Furthermore it implied that the operators have to be trained to learn the different types of control systems. The CERN-UNICOS invented for LHC [1] has been chosen due to its reliability and planned to run and be maintained for decades on. The complete migration is part of an agreement between CERN and INFN.

Sub-barrier transfer reactions studied with the magnetic spectrometer PRISMA

Transfer reactions in the sub-barrier region have been studied at Laboratori Nazionali di Legnaro (LNL) by using the large solid angle magnetic spectrometer PRISMA. In particular, excitation functions of multinucleon transfer channels have been measured for the systems 96Zr+40Ca (closed shell nuclei), 116Sn+60Ni (super-fluid nuclei) from the Coulomb barrier to 25% below. Results of these measurements are presented in this contribution.An ancillary detection system has been designed and built in order to perform kinematic coincidence measurements in conjunction with PRISMA. It will allow to study the effects of secondary processes, such as evaporation and fission, which strongly affect the final yield of the reaction products. The status of this development is also reported.

Thermal properties of light nuclei from 12C + 12C fusion–evaporation reactions

The 12C + 12C reaction at 95 MeV has been studied through the complete charge identification of its products by means of the GARFIELD+RCo experimental set-up at INFN Laboratori Nazionali di Legnaro (LNL). In this paper, the first of a series of two, a comparison to a dedicated Hauser–Feshbach calculation allows selecting a set of dissipative events which corresponds, to a large extent, to the statistical evaporation of highly excited 24Mg. Information on the isotopic distribution of the evaporation residues in coincidence with their complete evaporation chain is also extracted. The set of data puts strong constraints on the behaviour of the level density (LD) of light nuclei above the threshold for particle emission. In particular, a fast increase of the LD parameter with excitation energy is supported by the data. Residual deviations from a statistical behaviour are seen in two specific channels, and tentatively associated with a contamination from direct reactions and/or α-clustering effects. These channels are studied in further details in the second paper of the series.

Ionization efficiency estimations for the SPES surface ion source

Ion sources play a crucial role in ISOL (Isotope Separation On Line) facilities determining, with the target production system, the ion beam types available for experiments. In the framework of the SPES (Selective Production of Exotic Species) INFN (Istituto Nazionale di Fisica Nucleare) project, a preliminary study of the alkali metal isotopes ionization process was performed, by means of a surface ion source prototype. In particular, taking into consideration the specific SPES in-target isotope production, Cs and Rb ion beams were produced, using a dedicated test bench at LNL (Laboratori Nazionali di Legnaro). In this work the ionization efficiency test results for the SPES Ta surface ion source prototype are presented and discussed.

PIXE analysis of some Nigerian anti-diabetic medicinal plants (II)

Diabetes mellitus, a metabolic disease characterized by high blood glucose levels (hyperglycemia) due to defects in insulin secretion, or action, or both, is a debilitating disease leading to other complications and death of many people in the world. Some of the medicinal plants implicated in the herbal recipes for the treatment of diabetes in Nigeria have been reported. Additional medicinal plants used for the treatment of diabetes in Nigeria are presented in this work. These medicinal plants are becoming increasingly important and relevant as herbal drugs due to their use as antioxidants, nutraceuticals, food additives and supplements in combating diabetes. Elemental compositions of these anti-diabetic medicinal plants were determined using PIXE technique. The 1.8MV collimated proton beam from the 2.5MV AN 2000 Van de Graaff accelerator at Istituto Nazionale di Fisica Nucleare (INFN), Laboratori Nazionali di Legnaro (LNL) Legnaro (Padova) Italy was employed for the work. The results show the detection of twenty-one elements which include Mg, P, Ca, K, Mn, Cu, Zn, S, Cr, Co, Ni and V that are implicated in the regulation of insulin and the control of the blood-sugar levels in the human body. The entire plant of Boerhavia diffusa, Securidaca longipedunculata stem, leaves of Peperomia pellucida, Macrosphyra longistyla, Olax subscorpioidea, Phyllanthus muerillanus, Jatropha gossypifolia, Cassia occidentalis, Phyllanthus amarus, and leaf and stem of Murraya koenigii, which have high concentrations of these elements could be recommended as vegetables, nutraceuticals, food additives, supplements and drugs in the control and management of diabetes, if toxicity profiles indicate that they are safe. However, significantly high contents of Al and Si in the entire plant of Bryophyllum pinnatum, and As, Cr, and Cu in Ocimum gratissimum leaf suggest that these plants should be avoided by diabetic patients to prevent complications.

Status of the LEgnaro NeutrOn Source facility (LENOS)

Abstract LENOS is a new facility under development at Laboratori Nazionali di Legnaro (LNL). It is based on a new technic for neutron beam shaping in accelerator based neutron sources. The main advantage of this method is to be able to shape the primary charged-particle beam to a defined energy distribution that, impinging on a neutron producing target, generates the desired neutron spectra at the sample position. Together with the proton energy distribution, other degrees of freedom are used to obtain the desired neutron energy spectra, e.g. the angular distribution of produced neutrons, the nuclear reactions used for the neutron spectra production, and the convolution of neutron spectra coming from different target materials. The main advantage of this new approach is the good control over the energy and spatial distribution of the produced neutron spectrum avoiding most of the problems due to neutron moderation, since it is easier to work with charged particles than with neutrons. The goal of the LENOS facility is to obtain a Maxwell-Boltzmann neutron energy spectrum with tunable temperature and a high neutron flux at sample position by using the 7Li(p,n) reaction. To maximize the neutron flux a very narrow primary proton beam has to be used, so the target has to remove a very high specific power. Currently available lithium targets are inadequate to sustain the high specific power that needs to be dissipated in the LENOS facility. A dedicated target based on micro-channel geometry and liquid metal cooling has been developed and tested. This contribution describes the status of the LENOS facility.

Experimental test of the background rejection, through imaging capability, of a highly segmented AGATA germanium detector

The development of highly segmented germanium detectors as well as the algorithms to identify the position of the interaction within the crystal opens the possibility to locate the γ -ray source using Compton imaging algorithms. While the Compton-suppression shield, coupled to the germanium detector in conventional arrays, works also as an active filter against the γ rays originated outside the target, the new generation of position sensitive γ -ray detector arrays has to fully rely on tracking capabilities for this purpose. In specific experimental conditions, as the ones foreseen at radioactive beam facilities, the ability to discriminate background radiation improves the sensitivity of the gamma spectrometer. In this work we present the results of a measurement performed at the Laboratori Nazionali di Legnaro (LNL) aiming the evaluation of the AGATA detector capabilities to discriminate the origin of the γ rays on an event-by-event basis. It will be shown that, exploiting the Compton scattering formula, it is possible to track back γ rays coming from different positions, assigning them to specific emitting locations. These imaging capabilities are quantified for a single crystal AGATA detector.

Spectroscopic studies with the PRISMA-CLARA set-up

The large solid angle magnetic spectrometer for heavy ions PRISMA, installed at Laboratori Nazionali di Legnaro (LNL), was operated up to the end of March 2008 in conjunction with the highly efficient CLARA set-up. It allowed to carry out nuclear structure and reaction mechanism studies in several mass regions of the nuclide chart. Results obtained in the vicinity of the island of inversion and for the heavy iron and chromium isotopes are presented in this contribution. The status of the new focal plane detectors specifically designed for light ions and slow moving heavy ions is also reported.

The SPES project: An ISOL facility for exotic beams

SPES (Selective Production of Exotic Species) is an INFN project to develop a Radioactive Ion Beam (RIB) facility as an intermediate step toward EURISOL. The SPES project is part of the INFN Road Map for the Nuclear Physics development in Italy and is supported by the whole Italian Nuclear Physics community and mainly by LNL and LNS the INFN National Laboratories of Nuclear Physics in Legnaro and Catania. The Laboratori Nazionali di Legnaro (LNL) was chosen as the site for the facility construction due to the presence of the PIAVE-ALPI accelerator complex, which will be used as re-accelerator for the RIBs. The SPES project is based on the ISOL method with an UCx Direct Target and makes use of a proton driver of at least 40 MeV energy and 200 microA current. Neutron-rich radioactive beams will be produced by Uranium fission at an expected fission rate in the target in the order of 1013 fissions per second. The key feature of SPES is to provide high intensity and high-quality beams of neutron rich nuclei to perform forefront research in nuclear structure, reaction dynamics and interdisciplinary fields like medical, biological and material sciences. The exotic isotopes will be re-accelerated by the ALPI superconducting linac at energies up to 10AMeV for masses in the region of A=130 amu with an expected rate on target of 109 pps.

The BSA modeling for the accelerator-based BNCT facility at INFN LNL for treating shallow skin melanoma

The SPES-BNCT ongoing project of the Istituto Nazionale di Fisica Nucleare (INFN) is aimed at the construction at the Laboratori Nazionali di Legnaro (LNL) of an accelerator-based (AB), high-flux thermal neutron beam facility devoted to boron neutron capture therapy (BNCT) experimental treatment of extended skin melanoma, in the framework of SPES (selective production of exotic species) project. The neutron source will be produced via the 9Be(p,xn) reactions by a 5 MeV, 30 mA proton beam into a thick beryllium target. The resulting neutron spectrum is slowed down using a beam shaping assembly (BSA), for which modeling is in an advanced neutronic design stage. An overview on the BSA current status, based on the Be neutron converter prototype designed and already constructed, is reported.

Be target development for the accelerator-based SPES-BNCT facility at INFN Legnaro

An accelerator-driven thermal neutron source for BNCT, planned to be installed at the INFN Laboratori Nazionali di Legnaro (LNL), is in progress in the framework of the SPES (selective production of exotic species) research program. The most critical element of such a facility is the construction of a reliable neutron converter based on the 9Be(p,xn) nuclear reaction, working at a high power level (150 kW) and 5 MeV beam energy, due to the SPES driver constraints. Two original, beryllium-based, target concepts have been designed for such a purpose. The present status of the neutron converter, as well as the test results performed so far on prototypes constructed, is reported here.