1,721,005 research outputs found
An electromagnetic-wave approach for non-contact displacement measurement in a geological nuclear waste disposal
No full textThe aim of this work is to show a preliminary investigation of possible non-contact techniques for displacement measurement in a geological nuclear waste disposal. A nuclear waste repository can be considered as a harsh environment. This suggests the possibility to study alternative methods for measurement, for example methods not using cables or buses for detecting relevant data. A possible approach is substituting cables with wireless sensors. But if cables cannot be used and the use of wireless techniques is required, new sensors must assure reliable transmission without affecting the engineered barriers performance and the reliable use of energy supply for the measuring equipment over long periods. This work shows the results of a study on the possibility of using a Ground Penetrating Radar-like approach for the contactless displacement measurement of a container immersed and suspended in a material (bentonite) with a high degree of water retentio
Noncontact displacement measurement of nuclear waste canisters in a geological disposal by using an electromagnetic-wave approach
No full textThe aim of this work is to show a preliminary investigation of possible noncontact techniques for displacement measurement of radioactive waste in a geological disposal. Since a nuclear waste repository can be considered as a harsh environment, the possibility to study alternative methods for measurement, for example, not using cables or buses for detecting relevant data, should be considered as a priority. A straightforward approach could be the substitution of cables with wireless sensors. But if cables cannot be used and the use of wireless techniques is required, new sensors must assure a reliable transmission without affecting the engineered barriers performance and the reliable use of energy supply for the measuring equipment over long periods. This work shows the results of a study of feasibility on using an electromagnetic (EM) approach for the contactless displacement measurement of a canister immersed and suspended in bentonite, a material with a high degree of water retention
Experimental Setup for Non-Contact Displacement Measurement of Nuclear Waste via Electromagnetic Waves
No full textSpent nuclear fuel and high-level waste from fuel reprocessing are the most hazardous and long-lived radioactive wastes produced by the nuclear fuel cycle, and they must be contained and isolated for thousands of years at an acceptable safety level for human health and the environment. Recently, the authors have proposed a preliminary numerical investigation of possible non-contact techniques for displacement measurement in a geological nuclear waste disposal. In fact, cables used for the detection of measurement signals might be effectively substituted with wireless sensors, thus avoiding all the side effects produced in such a harsh environment (e.g. degradation due to temperature, humidity and radiation conditions). Previous works showed the feasibility of using an electromagnetic approach for the contactless displacement measurement of a canister immersed and suspended in bentonite, a material with a high degree of water retention. The results demonstrated that such an approach is possible provided that some strong requirements are imposed on the sensor design. Sure enough, new sensors must assure reliable transmission through the isolated areas of a repository without affecting the engineered barriers performance and reliable use of energy supply for the measuring equipment in the long term. This work proposes a possible experimental setup where the numerical models developed in previous works can be tested, so to arrive to a prototype sensor to be used in a demonstrator repository
RF system design for the TOP-IMPLART accelerator
No full textIn the ENEA-Frascati research center a linear accelerator for proton therapy is under development in the framework of TOP-IMPLART Project carried out by ENEA in collaboration with ISS and IRE-IFO. The machine is based on a 7 MeV injector operating at a frequency of 425 MHz followed by a sequence of 2997.92 MHz accelerating modules. Five 10 MW klystrons will be used to power all high frequency structures up to a beam energy of 150 MeV. The maximum repetition frequency is 100 Hz and the pulse duration is 4 μs. The RF amplitude and phase stability requirements of the accelerating field are within ±2% and ±2 degrees respectively. For therapeutic use the beam energy will be varied between 85 and 150 MeV by switching off the last modules and varying the electric field amplitude in the last module switched on. Fast control of the RF power supplied to the individual structures allows an energy variation on a pulse by pulse basis; furthermore the system must be able to control the RF phase between accelerating structures. This work describes the RF power distribution scheme and the RF phase and amplitude monitoring system implemented into an embedded control system. Copyright © 2015 CC-BY-3.0 and by the respective authors
Double free-electron laser oscillator for photon-photon collisions
No full textIn view of a quantum electrodynamics test, a "double" free-electron laser (FEL) oscillator is proposed as a possible device for head-on photon-photon collisions in vacuum. The oscillator is conceived in order to produce two laser beams in the same cavity by two counterpropagating electron beams. The latter are in turn exploited to produce gamma photons by backward Compton scattering of the intracavity FEL radiation itself. In view of an effective device design, specific ranges of values for the various parameters, that characterize the system, are individualized for operation at the maximum of the γ-γ scattering cross section. An estimate of the collision rate in definite device configurations is provided. © 2013 Optical Society of America
Experimental results on scdtl structures for protons
No full textThe medium-energy section of the proton linear accelerator for radiotherapy under realization in the framework of the TOP-IMPLART Project consists in a high frequency 7-35 MeV SCDTL (Side Coupled Drift Tube Linac) structure. The structure, made of 4 modules supplied by one klystron, has been completely designed. The first module up to 11.6 MeV has been built and is under commissioning at ENEA-Frascati and the second and third modules are under realization. The paper describes the system and presents the main results of the experimental activity on this part of the accelerator. Copyright © 2014 CC-BY-3.0 and by the respective authors
The TOP-IMPLART high-energy protron beam delivery line: a comparison of SRIM, FLUKA, and Fermi-Eyges theory predicions
Full text linkNell'ambito del progetto TOP-IMPLART, è stata progettata ed è in fase di “commissioning” una linea di rilascio del fascio per l'acceleratore lineare di protoni TOP-IMPLART dedicata a irraggiamenti a scansione di bersagli estesi a energie di 63 e 71 MeV. Per pianificare adeguatamente tali irraggiamenti, è necessario conoscere la dimensione laterale e la dispersione angolare del fascio che arriva sul piano del bersaglio. In una fase preliminare questa valutazione può essere eseguita utilizzando simulazioni e modelli teorici. In questo Rapporto Tecnico, esaminiamo il progetto attuale della linea di trasporto del fascio TOP-IMPLART utilizzando due codici Monte Carlo, SRIM e FLUKA, nonché un approccio numerico basato sulla teoria di Fermi-Eyges. I risultati mostrano che SRIM sottostima la dimensione laterale e la dispersione angolare del fascio sul piano del bersaglio rispetto a FLUKA. Un test sperimentale conferma che SRIM sottostima la dimensione del fascio, mentre FLUKA è in buon accordo con l'esperimento. Le previsioni della teoria di Fermi-Eyges sono più vicine ai risultati forniti da FLUKA.In the framework of the TOP-IMPLART project, a beam delivery line has been designed and is under commissioning for the TOP-IMPLART proton linear accelerator to enable irradiation scans of extended targets at energies of 63 and 71 MeV. To suitably plan these irradiations, it is necessary to know the lateral size and angular spread of the beam arriving at the target plane. In a preliminary stage, this evaluation can be performed using simulations and theoretical models. In this Technical Report, we examine the current design of the TOP-IMPLART beam delivery line using two Monte Carlo codes, SRIM and FLUKA, as well as a numerical approach based on the Fermi-Eyges theory. The results show that SRIM underestimates the beam’s lateral size and angular spread of the beam at the target plane compared to FLUKA. An experimental test confirms that SRIM underestimates the spot size, while FLUKA is in good agreement with the experiment. The predictions of the Fermi-Eyges theory are closer to the results provided by FLUKA
Superradiant cascade in a seeded free-electron laser
No full textWe report measurements demonstrating the concept of the free-electron laser (FEL) superradiant cascade. Radiation (λrad=200 nm) at the second harmonic of a short, intense seed laser pulse (λseed= 400 nm) was generated by the cascaded FEL scheme at the transition between the modulator and radiator undulator sections. The superradiance of the ultrashort pulse is confirmed by detailed measurements of the resulting spectral structure, the intensity level of the produced harmonics, and the trend of the energy growth along the undulator. These results are compared to numerical particle simulations using the FEL code GENESIS 1.3 and show a satisfactory agreement. © 2013 American Physical Society
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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