A measurement of the fast neutron background in the Gran Sasso underground laboratory has been performed by the MOSCAB thermodynamic bubble chamber, a neutron detector which identifies fast neutrons ...passing through the metastable fluid by scattering ions. The result of this measurement confirms the results previously obtained using detectors based on totally different techniques, thus corroborating the previous results in terms of both integral intensity and spectral characteristics, at least in the energy region where the current measurement technique is sensitive.
The MOSCAB equipment, a geyser-concept bubble-chamber originally thought for the search of dark matter in the form of WIMPs, is employed for the detection of fast neutrons. Once the background-free ...operating conditions are determined such that the detector is sensitive only to neutrons, which occurs when the neutron energy threshold required for nucleation is higher than approximately 2.5 MeV, the detector response to fast neutrons is investigated using a
241
AmBe neutron source. Sets of detection efficiency functions are then produced via Monte Carlo simulations and post-processing, their validation being performed experimentally and discussed. Finally, the use of the detector to measure the fast neutron activity of very weak n-sources in low neutron background environments, as well as to monitor the cosmic ray variations through the neutron component of the Extensive Air Showers, is considered.
Two equations for the calculation of the critical energy required for homogeneous nucleation in a superheated liquid, and the related critical radius of the nucleated vapour bubble, are obtained, the ...former by the direct application of the first law of thermodynamics, the latter by considering that the bubble formation implies the overcoming of a barrier of the free enthalpy potential. Compared with the currently used relationships, the present equations, still allowing for reversible processes only, lead to thermodynamic energy thresholds of the bubble chambers employed in dark matter searches that are closer to the experimental values.
In the framework of the search for dark matter in the form of WIMPs using superheated liquids, a study is conducted to establish a computational procedure aimed at determining how the thermodynamic ...conditions kept inside a particle detector affect the acoustic signal produced by bubble nucleation. It is found that the acoustic energy injected into the liquid by the growing vapour bubble increases as the liquid pressure is decreased and the superheat degree is increased, the former effect being crucial for the generation of a well-intelligible signal. A good agreement is met between the results of the present study and some experimental data available in the literature for the amplitude of the acoustic signal. Additionally, the higher loudness of the alpha-decay events compared with those arising from neutron-induced nuclear recoils is described in terms of multiple nucleations.
The MOSCAB experiment (Materia OSCura A Bolle) uses the “geyser technique”, a variant of the superheated liquid technique of extreme simplicity. Operating principles of the new dark matter detector ...and technical solutions of the device are reported in detail. First results obtained in a series of test runs taken in laboratory demonstrate that we have successfully built and tested a geyser-concept bubble chamber that can be used in particle physics, especially in dark matter searches, and that we are ready to move underground for extensive data taking.
We present in this article an outline of some cyclotron-based irradiation techniques that can be used to directly radiolabel industrially manufactured nanoparticles, as well as two techniques for ...synthesis of labelled nanoparticles using cyclotron-generated radioactive precursor materials. These radiolabelled nanoparticles are suitable for a range of different in vitro and in vivo tracing studies of relevance to the field of nanotoxicology. A basic overview is given of the relevant physics of nuclear reactions regarding both ion-beam and neutron production of radioisotopes. The various issues that determine the practicality and usefulness of the different methods are discussed, including radioisotope yield, nuclear reaction kinetics, radiation and thermal damage, and radiolabel stability. Experimental details are presented regarding several techniques applied in our laboratories, including direct light-ion activation of dry nanoparticle samples, neutron activation of nanoparticles and suspensions using an ion-beam driven activator, spark-ignition generation of nanoparticle aerosols using activated electrode materials, and radiochemical synthesis of nanoparticles using cyclotron-produced isotopes. The application of these techniques is illustrated through short descriptions of some selected results thus far achieved. It is shown that these cyclotron-based methods offer a very useful range of options for nanoparticle radiolabelling despite some experimental difficulties associated with their application. For direct nanoparticle radiolabelling, if care is taken in choosing the experimental conditions applied, useful activity levels can be achieved in a wide range of nanoparticle types, without causing substantial thermal or radiation damage to the nanoparticle structure. Nanoparticle synthesis using radioactive precursors presents a different set of issues and offers a complementary and equally valid approach when laboratory generation of the nanoparticles is acceptable for the proposed studies, and where an appropriate radiolabel can be incorporated into the nanoparticles during synthesis.
•We develop a MCNPX model of the TAPIRO fast research reactor.•The model has been tested against the result of a late experimental champaign finding on overall agreement.•The source of uncertainties ...in the nuclear data and in the model assumptions has been discussed.•The model is sufficiently accurate to design irradiation experiment in support to R&D activities on LFR and ADS systems.
After Fukushima events, the Italian nuclear program has been redefined leaving space only to activities related to Generation IV nuclear systems. Accordingly with this renewed national scenario, TAPIRO fast reactor facility is gaining a relatively major strategic role. A program is in fact being proposed to host in TAPIRO benchmark experimental activities related to the development of Lead fast reactor and Accelerator Driven Systems. A first step of this program would consist on the validation of neutronic codes, cross section data and reactor models to be adopted for its analysis. Along this line in this work the results of a simulation study has been made relevant to the measurements performed in the SCK-CEN/ENEA experimental campaign carried out in the 1980–1986 period. The calculations have been made using the Monte Carlo MCNPX 2.7.0 Code. In this article the main results are presented and discussed, with particular emphasis on the uncertainties, relevant both to nuclear data and the model layout. The results of this simulation study indicate in particular that TAPIRO's MCNPX model is adequate for the optimization of set-ups of perspective neutron irradiation experiments, this allowing cuts in costs and development time.
In the framework of the EC funded INBARCA project (Innovative Nanosphere Brachytherapy with Adiabatic Resonance Crossing using Accelerators) a compact, accelerator driven neutron activator has been ...designed and constructed, with the aim of efficiently utilising ion-beam generated neutrons for the production of radioactive nanoparticles for brachytherapy. The design is based on a modified version of the Adiabatic Resonance Crossing concept, first proposed by C. Rubbia of CERN. The neutron activator has been tested in two experimental configurations, with and without a central lead block. The activation performance on different materials was quantified by γ-spectrometry. Monte Carlo simulations accompanied all experimental runs, and neutron unfolding techniques were used to derive the experimental neutron spectrum. This paper compares the simulated and the unfolded neutron spectra thus obtained, as well as the experimental and simulated activation results for pure Au, Ag, Mo, Ni, Ho and Re foils as well as for Re and Ho nanoparticles.
The TRIGA RC-1 1
MW reactor operating at ENEA Casaccia Center is currently being developed as a second neutron imaging facility that shall be devoted to computed tomography as well as neutron ...tomography. In order to reduce the gamma-ray content in the neutron beam, the reactor tangential piercing channel was selected. A set of Monte Carlo simulation was used to design the neutron collimator, to determine the preliminary choice of the materials to be employed in the collimator design.
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