Simulation, design and tests of a diagnostic calorimeter for the spider experiment

One of the most critical issues for fusion reactors, to be studied in ITER (the prototype that has to prove the feasibility of production of electric energy by fusion), is the generation of sufficient energy to the sustainment of fusion reactions as well as to the injection on the electric transmission network. As ohmic heating, produced by the current flowing in the plasma, is not sufficient for the operation in fusion conditions, it is necessary to use additional heating systems. One of these methods, to be evaluated during ITER operations, is the additional heating of the plasma by means of neutral particle beams injected into the core plasma. At Consorzio RFX, in the research area of the C.N.R. of Padua, the design of the project PRIMA-MITICA-SPIDER (PMS) is ongoing and construction of the building has already started. The PMS project includes two experiments: MITICA is the full-size prototype of ITER injector and SPIDER, whose operations will start before MITICA, is realized with the aim of optimising the production of the negative ions composing the beam. To this scope a detailed knowledge of the parameters of the plasma inside the source and of the beam features is fundamental, obtained with diagnostic systems foreseen on SPIDER; one of them is the diagnostic calorimeter STRIKE, developed in the present PhD work. During the thesis the requirements of the calorimeter have been defined and the design has been concluded. Verifications of some design solutions have been performed by designing and realizing dedicated prototypes. CFC, a unidirectional carbon fibre composite with a carbon matrix, is the main component of the calorimeter. Several samples of 1D CFC have been purchased from different suppliers, to characterise their thermal properties by a power laser and by high-energy particle beam tests. A prototype of the whole system has been realized, including the thermal camera, and was used in the BATMAN ion source at IPP-Garching (Germany) with the aim of evaluating the diagnostic capabilities in conditions similar to those expected in SPIDER. Non linear transient finite element thermal analyses and electrostatic simulations have been developed for the design phase as well as the test phase. Moreover, the planning of the activities for the calorimeter together with the preparation and writing of the whole documentation have been supervised. The small and flexible NIO1 source, under development as a collaboration between Consorzio RFX and INFN-LNL, will soon be ready to study the negative ion source behaviour. Preliminary studies for the use of CFC prototypes to characterise the NIO1 beam, carried out during the PhD, are also presented. The conclusion of this work is that STRIKE should prove a very valuable diagnostic of the SPIDER beam characteristics and should allow to assess the compliance of the SPIDER beam with the ITER requirement

Design optimization of RF lines in vacuum environment for the MITICA experiment

This contribution regards the Radio Frequency (RF) transmission line of the Megavolt ITER Injector and Concept Advancement (MITICA) experiment. The original design considered copper coaxial lines of 1″ 5/8, but thermal simulations under operating conditions showed maximum temperatures of the lines at regime not compatible with the prescription of the component manufacturer. Hence, an optimization of the design was necessary. Enhancing thermal radiation and increasing the conductor size were considered for design optimization: thermal analyses were carried out to calculate the temperature of MITICA RF lines during operation, as a function of the emissivity value and of other geometrical parameters. Five coating products to increase the conductor surface emissivity were tested, measuring the outgassing behavior of the selected products and the obtained emissivity values

Simulation, design and tests of a diagnostic calorimeter for the spider experiment

One of the most critical issues for fusion reactors, to be studied in ITER (the prototype that has to prove the feasibility of production of electric energy by fusion), is the generation of sufficient energy to the sustainment of fusion reactions as well as to the injection on the electric transmission network. As ohmic heating, produced by the current flowing in the plasma, is not sufficient for the operation in fusion conditions, it is necessary to use additional heating systems. One of these methods, to be evaluated during ITER operations, is the additional heating of the plasma by means of neutral particle beams injected into the core plasma. At Consorzio RFX, in the research area of the C.N.R. of Padua, the design of the project PRIMA-MITICA-SPIDER (PMS) is ongoing and construction of the building has already started. The PMS project includes two experiments: MITICA is the full-size prototype of ITER injector and SPIDER, whose operations will start before MITICA, is realized with the aim of optimising the production of the negative ions composing the beam. To this scope a detailed knowledge of the parameters of the plasma inside the source and of the beam features is fundamental, obtained with diagnostic systems foreseen on SPIDER; one of them is the diagnostic calorimeter STRIKE, developed in the present PhD work. During the thesis the requirements of the calorimeter have been defined and the design has been concluded. Verifications of some design solutions have been performed by designing and realizing dedicated prototypes. CFC, a unidirectional carbon fibre composite with a carbon matrix, is the main component of the calorimeter. Several samples of 1D CFC have been purchased from different suppliers, to characterise their thermal properties by a power laser and by high-energy particle beam tests. A prototype of the whole system has been realized, including the thermal camera, and was used in the BATMAN ion source at IPP-Garching (Germany) with the aim of evaluating the diagnostic capabilities in conditions similar to those expected in SPIDER. Non linear transient finite element thermal analyses and electrostatic simulations have been developed for the design phase as well as the test phase. Moreover, the planning of the activities for the calorimeter together with the preparation and writing of the whole documentation have been supervised. The small and flexible NIO1 source, under development as a collaboration between Consorzio RFX and INFN-LNL, will soon be ready to study the negative ion source behaviour. Preliminary studies for the use of CFC prototypes to characterise the NIO1 beam, carried out during the PhD, are also presented. The conclusion of this work is that STRIKE should prove a very valuable diagnostic of the SPIDER beam characteristics and should allow to assess the compliance of the SPIDER beam with the ITER requirementsUno degli aspetti più critici dei reattori a fusione, che verrà studiato in ITER (prototipo che dovrà provare la fattibilità di questa tecnica di produzione dell’energia elettrica), è la generazione di energia sufficiente sia all’autosostentamento della reazione di fusione sia all’immissione nella rete elettrica di trasmissione. Non essendo sufficiente per il funzionamento in condizioni di fusione il riscaldamento ohmico, prodotto dalla corrente che fluisce nel plasma, è necessario utilizzare delle tecniche di riscaldamento addizionali. Una delle vie che saranno valutate in ITER è l’ulteriore riscaldamento del plasma ottenuto tramite l’iniezione di un fascio di particelle neutre nel plasma centrale. Al Consorzio RFX, nell’area di ricerca del C.N.R. di Padova, si sta procedendo con l’ultimazione della progettazione e l’avvio dei lavori di costruzione del progetto PRIMA-MITICA-SPIDER, che comprende due esperimenti: MITICA è il prototipo in scala reale dell’iniettore di ITER mentre SPIDER, che sarà in esercizio prima di MITICA, è realizzato con l’obiettivo di ottimizzare il funzionamento della sorgente di ioni negativi che costituiscono il fascio. Allo scopo, è fondamentale una conoscenza accurata dei parametri del plasma internamente alla sorgente e del fascio, ottenuta tramite i vari sistemi diagnostici previsti in SPIDER, tra i quali il calorimetro diagnostico STRIKE, argomento del presente lavoro di dottorato. Durante la tesi si sono definiti i requisiti del calorimetro e se ne è concluso il progetto. Si sono verificate, progettando e realizzando appositi prototipi, alcune soluzioni costruttive. Si sono acquistati da produttori diversi alcuni prototipi di CFC 1D, elemento principale che costituisce il calorimetro, un materiale in fibra di carbonio unidirezionale su matrice di carbonio, per caratterizzarne le proprietà termiche mediante riscaldamento con laser di potenza e nell’esperimento GLADIS presso l’IPP di Garching (Germania), con fascio di particelle di alta intensità. Si è anche realizzato un prototipo del sistema completo, inclusa la telecamera termica, che è stato utilizzato nell’esperimento BATMAN presso l’IPP di Garching (Germania), con lo scopo di valutarne il funzionamento in condizioni simili a quelle di SPIDER. Sia la fase di progettazione che quella di test sono state accompagnate da simulazioni numeriche agli elementi finiti, di tipo elettrostatico e termico transitorio non lineare. Inoltre, si è seguita anche la parte di pianificazione e documentazione relativa al progetto del calorimetro. Nella collaborazione tra Consorzio RFX and INFN-LNL, si sta sviluppando un’ulteriore sorgente di ioni negativi: NIO1, che a breve entrerà in operazione. La particolarità di questa sorgente è di essere piccola e flessibile. In questa tesi saranno inoltre presentati i risultati preliminari sulla valutazione dell’utilizzo di campioni di CFC per la caratterizzazione anche del fascio di NIO1. Il lavoro di tesi si conclude pronunciandosi positivamente sulla validità dell’utilizzo di STRIKE per studiare approfonditamente le caratteristiche del fascio di SPIDER e valutarne la corrispondenza ai requisiti richiesti da ITE

Design and realisation of a remotely controlled positioning system in an atmospheric plasma torch for film deposition and plasma characterization

none10noneL.Lotto; P.Sonato; M.De Muri; R.Malutta; G.Serianni; L.Franchin; V.Cervaro; F.Dughiero; E.Sieni; M.BulloLotto, Luca; Sonato, Piergiorgio; DE MURI, Michela; R., Malutta; Serianni, Gianluigi; L., Franchin; V., Cervaro; Dughiero, Fabrizio; Sieni, Elisabetta; Bullo, Marc

First negative ion beam measurement by the Short-Time Retractable Instrumented Kalorimeter Experiment (STRIKE)

The Source for Production of Ion of Deuterium Extracted from Rf plasma (SPIDER) test facility is under construction in Padova to optimise the operation of the beam source of ITER neutral beam injectors. The SPIDER beam will be characterised by the instrumented calorimeter STRIKE, whose main components are one-directional carbon-fibre-carbon-composite tiles. A small-scale version of the entire system has been employed in the BAvarian Test MAchine for Negative ions (BATMAN) testbed by arranging two prototype tiles in the vertical direction. The paper presents a description of the mini-STRIKE system and of the data analysis procedures, as well as some results concerning the BATMAN beam under varying operating conditions

Characterization of the SPIDER Cs oven prototype in the CAesium Test Stand for the ITER HNB negative ion sources

The ITER Heating Neutral Beam (HNB) injector is required to deliver 16.7 MW of power to the plasma from aneutralized beam of H 12/D 12negative ions, produced by an RF source and accelerated up to 1 MeV. To enhancethe H 12/D 12production, Cs will be routinely evaporated in the source by means of specific ovens embedded inthe source, to reduce its work function. Controlling and monitoring the evaporation rate of Cs inside the sourcewill be fundamental to achieve the desired performance for the ITER HNB.The prototype RF negative ion source SPIDER has been developed and built in the Neutral Beam Test Facilityat Consorzio RFX. In SPIDER, liquid Cs based ovens will be used to inject Cs vapors inside the source. TheCAesium Test Stand (CATS) has been specifically designed and set up for testing, commissioning, and char-acterizing Cs ovens in vacuum, but also to study the Cs evaporation and deposition onto surfaces. A SPIDER Csoven prototype has been manufactured and tested in CATS in order to characterize its thermal behavior, bymeans of thermocouples and thermal camera, and its Csflux, by means of Surface Ionization Detectors and LaserAbsorption Spectroscopy