Relatore RFX: C. Poggi
Relatore accademico: G. Serianni
Capogruppo RFX: M. Zuin
Tipologia: Sperimentale, Teorica, Numerica, Compilativa
Abstract:
SPIDER is the prototype of ITER heating neutral beams. It aims at producinig up to 50A of negative hydrogen ions, divided in 1280 beamlets, and accelerate them up to 100keV. During its first years of operation, the optics of SPIDER beamlets was investigated using several diagnostics, such as optical cameras and thermography measuring in the position space (namely x and y coordinates), beam emission spectroscopy measuring one component of the particle velocities (vx or vy) and Allison emittance scanner, providing a simultaneous measurement of a position and a velocity component (x and vx). This last diagnostic consists of a slit selecting the beam particles, a pair of metallic plates symmetric and parallel to the slit and then a second slit, aligned with the first one. An electric field is generated between the plates, so that only the particles with a well-defined transverse entrance velocity at the first slit can reach the second one and be collected at the Faraday cup. By moving the detector in front of the beam (in the direction perpendicular to the slit width) and by sweeping the voltage between the plates it is possible to determine the 2D transverse phase-space of the particle beam. This diagnostic provided a valuable insight into the phase-space structure of SPIDER beamlets, being able to identify the tails of the beamlets phase-space distribution.
During SPIDER last campaigns only a few beamlets were operated, allowing an easier investigation of the single beamlet optics. However, in view of future SPIDER multi-beamlet operation, the emittance scanner needs to be redesigned. For this reason, an upgraded version of the scanner is under development, with the goal of performing a direct measurement of x, vx, y and vy coordinates. Two additional metallic plates should be added to measure in the other transverse velocity direction, and a new Faraday cup, adequate to the expected currents. The aim of this thesis is to verify the feasibility of this approach using numerical simulations of a scanner with a double set of parallel plates, to dimension the various components of the detector, and to design and test the new current detector in a dedicated ion source.
Competenze necessarie per svolgere con successo la tesi:
Assegnata a Fabrizio Lovisetti
Proponente/Relatore RFX: I. Mario
Relatore accademico: G. Serianni
Capogruppo RFX: M. Zuin
Responsabile di Programma RFX: V. Toigo
Tipologia: Sperimentale, Teorica, Numerica, Compilativa
Abstract:
Neutral Beam Injectors for fusion applications require the production and acceleration of negative ions. Negative ion sources are based on the inductive coupling of electromagnetic waves to a hydrogen plasma (ICP discharge). To optimise the design of such sources, and particularly of the RF driver (the region where the plasma is generated), the MINION experiment is under design at Consorzio RFX and will start operations in 2023. The main diagnostic systems to measure the plasma features are emission spectroscopy and Langmuir probes.
The proposed activity consists in:
The student will improve his/her knowledge of the physics of ICP plasmas and on the diagnostics of cold plasmas. The activity might include simple simulations of the plasma features.
Competenze necessarie per svolgere con successo la tesi:
Tesi assegnata a:William Henri Vienne
Relatore RFX: C. Cavallini
Relatore accademico: P. Sonato
Capogruppo RFX: A. Rizzolo
Responsabile di Programma RFX: V. Toigo
Abstract:
Water is the most common fluid used to remove the heat produced in a research fusion reactor.
The Neutral Beam Test Facility (NBTF) at Consorzio RFX (Padua, Italy) host two test beds: MITICA, the 1 MeV full-scale prototype of the ITER NBI source, and SPIDER, the low energy 100 keV ITER full-size Ion Source.
SPIDER and MITICA experiments are actively cooled by Ultrapure Water (UPW) to electrically insulate in-vessel components that are polarized to high voltage levels. Water circulating in pipes reacts with inner channel surfaces made of copper, copper alloys and stainless steel, causing a water resistivity degradation. Maintaining high quality water is the most important factor in preventing degradation. . Depending on the material and the water composition, several chemical reactions can occur to form soluble or insoluble compounds. General corrosion of copper and copper alloys in ultrapure water will be experimentally investigated, using metal release test. During the thesis, you will learn how to manage ultrapure water, discover the CuCrZr alloy, test different material exposed to the same environmental condition and take part of the ITER project by working at the NBTF facility!
Competenze necessarie per svolgere con successo la tesi:
Assegnata a Sara Zampieri
RFX Supervisor: L. Zanotto
Academic supervisor: P. Bettini
Tipologia: Sperimentale, Teorica, Numerica, Compilativa
Abstract:
The thesis deals with the measurement of the dc current component in the inverters of the MITICA Acceleration Grid Power Supply. After a literature survey on the subject of dc current generation and control on three phase inverter systems supplying power transformers, the student shall analyze the precision of the present current transducers andassessthe use of new transducers or methods to estimate the dc current component supplied by the inverters in different load conditions and transients. The thesiscan be completed by experimental measurements on a dummy load aimed at testing the new transducers or methods and reviewing the operation of the existing dc current controller, with focus on possible strategies for improvement.
Tesi assegnata a: Andrea Magnabosco
Proponente/Relatore RFX: R. Delogu
Relatore accademico: M. Margoni
Capogruppo RFX: G. Taliercio
Responsabile di Programma RFX: V. Toigo
Tipologia: Sperimentale, Teorica, Numerica, Compilativa
Abstract:
STRIKE (Short-Time Retractable Instrumented Kalorimeter Experiment) is an instrumented calorimeter; it has been designed with the main purpose of characterizing the negative ion beam produced in SPIDER (Source for Production of Ion of Deuterium Extracted from Radio Frequency plasma) in terms of beam uniformity and divergence, during short pulse operations. STRIKE is made of 16 1D Carbon Fiber Carbon composite (CFC) tiles, intercepting the whole beam and observed on the rear side by infrared (IR) cameras.
The whole beam consists of 1280 beamlets, 80 for each tile, and the profile of a beamlet can be well approximated by a 2D Gaussian curve. Furthermore, due to the beamlet configuration and the heat transfer condition, some of the beamlets could overlap.The aim of this thesis is to determine, by means of Newton’s method, the parameters (amplitude, Half Width at Half Maximum, position of the Gaussian 2D profile) of all beamlets, in order to have a real-time tool to be used during operation. Moreover, the method will be tested also for overlapping beamlets.
Competenze necessarie per svolgere con successo la tesi: basic programming, English language
Tesi assegnata a: Eleonora Degan
Proponente/Relatore RFX: Mattia Dan
Relatore Accademico: Paolo Bettini
Capogruppo: Alberto Maistrello
Responsabile di Programma: Vanni Toigo
Tipologia: Sperimentale, Teorica, Numerica, Compilativa
Abstract:
SPIDER is the test-bed for the negative ion beam source of the ITER Heating Neutral Beam Injectors (NBI). The beam source is polarized up to – 96 kV for the beam acceleration, achieved through an electrostatic grid acceleration system. Similarly, the Ion Source and Extraction Power Supply (ISEPS) is polarized at the acceleration voltage, with an insulating transformer powering the system to ensure proper dc insulation between the primary and secondary circuits. A peculiarity of the high voltage system is the frequent occurrence of arc breakdowns between the acceleration grids due to the short gap required by the beam optics. These breakdowns happen due to the short gap required by the beam optics, leading to high-frequency voltage stresses on the interconnected power supply system. One component that can be subjected to high voltage stresses is ISEPS insulation transformer, in particular in its secondary circuit.
The purpose of this thesis is to analyze the breakdown transient conditions on the SPIDER insulation transformer: the student shall get a good comprehension of the fast transients subsequent to a breakdown, use circuital models to estimate the voltage stresses and conduct tests on the system at reduced medium voltage levels.
Tesi assegnata a: Daniele Fasolo
RFX Supervisor: R. Delogu
Academic Supervisor: N. Marconato
Capogruppo RFX: Taliercio
Responsabile di Programma RFX: V. Toigo
Tipologia: Sperimentale, Teorica, Numerica, Compilativa
Abstract:
STRIKE (Short-Time Retractable Instrumented Kalorimeter Experiment) is an instrumented calorimeter; it has been designed with the main purpose of characterizing the negative ion beam produced in SPIDER (Source for Production of Ion of Deuterium Extracted from Radio Frequency plasma) in terms of beam uniformity and divergence, during short pulse operations. STRIKE is made of 16 1D Carbon Fiber Carbon composite (CFC) tiles, intercepting the whole beam and observed on the rear side by infrared (IR) cameras.The whole beam consists of 1280 beamlets, 80 for each tile, and the profile of a beamlet can be well approximated by a 2D Gaussian curve. Furthermore, due to the beamlet configuration and the heat transfer condition, some of the beamlets could overlap.The aim of this thesis is to determine, by means of machine learning techniques, the parameters (amplitude, Half Width at Half Maximum, position of the Gaussian 2D profile) of all beamlets, in order to have a real-time tool to be used during operation. Moreover, where possible, deconvolution will have to be applied to the overlapping beamlets.
Competenze necessarie per svolgere con successo la tesi: basic programming, English language
Tesi assegnata a: Kenji Urazaki Junior
RFX Supervisor: N. Vianello
Academic supervisor: M. Zuin
Head of the RFX research group: M. Zuin
Leader of the RFX research program: L. Marrelli
Tipologia: Sperimentale, Teorica, Numerica, Compilativa
Abstract:
The thesis will investigate the process of electron acceleration in magnetically confined plasmas and its relation with electrostatic and magnetic turbulence. In particular will perform an experimental investigation on data collected in a Reversed Field Pinch plasmas, data obtained by insertable probes combining Langmuir probes, magnetic pick-up coils and Electron energy analyzer (EEA). The analysis will be performed at different temporal scales to verify eventually if turbulence energy cascade has any influence on the signal collected by the EEA being this proportional to electron energy. Analysis will include advanced statistical tools, including wavelet transform, waiting times and Probability distribution functions. The collected information will be compared to similar statistical analysis performed on the outcome of numerical simulations, based on Vlasov code obtained in condition closed to the explored experimental regime.
Tesi assegnata a: Monia Calcagno