Neutron sources based on medical Linac

The paper proposes the study of a novel photo-neutron source based on a medical high-energy electron Linac. Previous studies by the authors already demonstrated the possibility to obtain with this technique a thermal neutron flux of the order of 107 cm−2 s−1. This paper shows possible Linac’s setup and a new photo-converter design to reach a thermal neutron flux around 6 × 107 cm−2 s−1, keeping a reasonable high quality of the beam with respect to fast neutron and gamma contaminations

Design of an epithermal column for BNCT based on D–D fusion neutron facility

Abstract Boron Neutron Capture Therapy (BNCT) is currently performed on patients at nuclear reactors. At the same time the international BNCT community is engaged in the development of alternative facilities for in-hospital treatments. This paper investigates the potential of a novel high-output D–D neutron generator, developed at Lawrence Berkeley National Laboratory (CA, USA), for BNCT. The simulation code MCNP-4C is used to realize an accurate study of the epithermal column in view of the treatment of deep tumours. Different materials and Beam Shaping Assemblies (BSA) are investigated and an optimized configuration is proposed. The neutron beam quality is defined by the standard free beam parameters, calculated averaging over the collimator aperture. The results are discussed and compared with the performances of other facilities

Unsourced Multiple Access with Common Alarm Messages: Network Slicing for Massive and Critical IoT

We investigate the coexistence of massive and critical Internet of Things (IoT) services in the context of the unsourced multiple access (UMA) framework introduced by Polyanskiy (2017), where all users employ a common codebook and the receiver returns an unordered list of decoded codewords. This setup is suitably modified to introduce heterogeneous traffic. Specifically, to model the massive IoT service, a standard message originates independently from each IoT device as in the standard UMA setup. To model the critical IoT service, we assume the generation of alarm messages that are common for all devices. This setup requires a significant redefinition of the error events, i.e., misdetections and false positives. We further assume that the number of active users in each transmission attempt is random and unknown. We derive a random-coding achievability bound on the misdetection and false positive probabilities of both standard and alarm messages on the Gaussian multiple access channel. Using our bound, we demonstrate that orthogonal network slicing enables massive and critical IoT to coexist under the requirement of high energy efficiency. On the contrary, we show that nonorthogonal network slicing is energy inefficient due to the residual interference from the alarm signal when decoding the standard messages.Comment: IEEE Transactions on Communication

Performances of 4H-SiC Schottky diodes as neutron detectors

Abstract Large area 4H-SiC Schottky diodes equipped with a 6LiF converter were tested as neutron detectors in the epithermal column realized for Boron Neutron Capture Therapy (BNCT) applications at the fast reactor TAPIRO (ENEA Casaccia Roma). The neutron spectra were assessed using the Monte Carlo code MCNP-4C. The performances of SiC detectors were evaluated with neutron fluences in the range of 109–1013 cm−2 which is typical for BNCT. Spectra of alpha and tritium particles generated by 6Li(n,α)3H reaction were collected at various neutron fluences and spectra obtained by interposing polyethylene moderators of different thickness. Only weak damaging effects primarily due to the alpha particles were observed; at neutron fluence of 1013 cm−2 the count rate decreased b

First results with the {ANET} Compact Thermal Neutron Collimator

This paper presents the first determination of the spatial resolution of the ANET Compact Neutron Collimator, obtained with a measuring campaign at the LENA Mark-II TRIGA reactor in Pavia. This novel collimator consists of a sequence of collimating and absorbing channels organised in a chessboard-like geometry. It has a scalable structure both in length and in the field of view. It is characterized by an elevated collimation power within a limited length. Its scalability and compactness are added values with respect to traditional collimating system. The prototype tested in this article is composed of 4 concatenated stages, each 100mm long, with a channel width of 2.5mm, delivering a nominal L/D factor of 160. This measuring campaign illustrates the use of the ANET collimator and its potential application in neutron imaging for facilities with small or medium size neutron sources.Comment: 9 pages, 8 figures, prepared for submission to JINS

Design of a novel compact neutron collimator

In this work the concept of a novel slow neutron collimator and the way to operate it are presented. The idea is based on the possibility to decouple the device field-of-view from its collimation power. A multi-channel geometry is proposed consisting of a chess-board structure where highly neutron-absorbing channels are alternated to air channels. A borated polymer was purposely developed to produce the attenuating components in the form of square-sectioned long rods. A scalable structure consisting of multiple collimation sectors can be arranged. The geometrical parameter LD, corresponding to the ratio between the length of a channel and its width, defines the collimation power. Several sectors can be arranged one after the other to reach relevant collimation powers. Each sector, 100 mm long, is composed by several channels with D = 2.5 mm corresponding to an L/D coefficient of 40. The target field of view is 50x50 mm2. This novel collimator, developed inside the INFN-ANET collaboration, due to its intrinsic compactness, will be of great importance to enhance the neutron imaging capability of small to medium-size neutron sources.Comment: 8 pages, 5 figures, accepted for publication to JINS

"Thermoluminescence dating laboratory improvements tested on an archaeological rescue site in Trino, Vercelli province, Italy"

Thermoluminescence (TL) is a reliable radiation-based technique for the dating and authentication of ceramic objects, allowing the evaluation of the time elapsed since their last exposure to high temperatures (e.g. firing in kiln or later fire events). The TL laboratory developed in the last decade at the Physics Department of the University of Torino, currently operating within the INFN (National Institute of Nuclear Physics) CHNet network, is presented. The 10-years-long experience in the field resulted in the enhancement of the procedures, with the development of customised α and β irradiation systems and the optimisation of sampling approach and chemical pre-treatment. In collaboration with TecnArt S.r.l., the improved procedures were employed for dating two structures from a rescue archaeological site in the Vercelli province (Italy)

Development of gamma insensitive silicon carbide diagnostics to qualify intense thermal and epithermal neutron fields

The e_LiBANS project aims at creating accelerator based compact neutron facilities for diverse interdisciplinary applications. After the successful setting up and characterization of a thermal neutron source based on a medical electron LINAC, a similar assembly for epithermal neutrons has been developed. The project is based on an Elekta 18 MV LINAC coupled with a photoconverter-moderator system which deploys the ({\gamma},n) photonuclear reaction to convert a bremsstrahlung photon beam into a neutron field. This communication describes the development of novel diagnostics to qualify the thermal and epithermal neutron fields that have been produced. In particular, a proof of concept for the use of silicon carbide photodiodes as a thermal neutron rate detector is presented.Comment: 10 pages, 10 figures, accepted for publication to JINST on the 17th April 202

INTENSE THERMAL NEUTRON FIELDS FROM A MEDICAL-TYPE LINAC: THE E_LIBANS PROJECT

The e_LiBANS project aims at producing intense thermal neutron fields for diverse interdisciplinary irradiation purposes. It makes use of a reconditioned medical electron LINAC, recently installed at the Physics Department and INFN in Torino, coupled to a dedicated photo-converter, developed within this collaboration, that uses (\u3b3,n) reaction within high Z targets. Produced neutrons are then moderated to thermal energies and concentrated in an irradiation volume. To measure and to characterize in real time the intense field inside the cavity new thermal neutron detectors were designed with high radiation resistance, low noise and very high neutron-to-photon discrimination capability. This article offers an overview of the e_LiBANS project and describes the results of the benchmark experiment