Initial experiments with a versatile multi-aperture negative-ion source and related improvements

A relatively compact ion source, named NIO1 (Negative-Ion Optimization 1), with 9 beam apertures for H− extraction is under commissioning, in collaboration between Consorzio RFX and INFN, to provide a test bench for source optimizations, for innovations, and for simulation code validations in support of Neutral Beam Injectors (NBI) optimization. NIO1 installation includes a 60 kV high-voltage deck, power supplies for a 130mA ion nominal current, an X-ray shield, and beam diagnostics. Plasma is heated with a tunable 2MHz radiofrequency (rf) generator. Physical aspects of source operation and rf-plasma coupling are discussed. NIO1 tuning procedures and plasma experiments both with air and with hydrogen as filling gas are described, up to a 1.7 kW rf power. Transitions to inductively coupled plasma are reported in the case of air (for a rf power of about 0.5 kW and a gas pressure below 2Pa), discussing their robust signature in optical emission, and briefly summarized for hydrogen, where more than 1 kW rf power is needed

First experiments with the negative ion source NIO1

Neutral Beam Injectors (NBIs), which need to be strongly optimized in the perspective of DEMO reactor, request a thorough understanding of the negative ion source used and of the multi-beamlet optics. A relatively compact radio frequency (rf) ion source, named NIO1 (Negative Ion Optimization 1), with 9 beam apertures for a total H- current of 130 mA, 60 kV acceleration voltage, was installed at Consorzio RFX, including a high voltage deck and an X-ray shield, to provide a test bench for source optimizations for activities in support to the ITER NBI test facility. NIO1 status and plasma experiments both with air and with hydrogen as filling gas are described. Transition from a weak plasma to an inductively coupled plasma is clearly evident for the former gas and may be triggered by rising the rf power (over 0.5 kW) at low pressure (equal or below 2 Pa). Transition in hydrogen plasma requires more rf power (over 1.5 kW)

Appunti di Liberty milanese

Rapido excursus di inquadramento sull'arte liberty in Italia e a Milano, con alcune realizzazioni architettoniche e scultoree-decorative dei maggiori artisti del tempo e un focus su Giuseppe Sommaruga a Palazzo Castiglioni

Simone Cantoni : architetto 1818-2018

Mostra documentaria sull'architetto neoclassico Simone Cantoni (1739-1818), nel bicentenario della sua morte avvenuta a Gorgonzola, nel cantiere della loale chiesa parrocchiale, dove \ue8 sepolto

Il monumento e il suo pubblico tra Ottocento e Novecento: fra valori estetici ed esperienze concettuali

Presentazione di casi esemplari di monumenti pubblici milanesi fra Otto e Novecento, evidenziando il ruolo rivestito dalla componente del pubblico nella commissione-realizzazione-ricezione delle opere, cos\uec analizzando l'atteggiamento di volta in volta assunto dal pubblico (passivo, attivo, coinvolto o meno) nei confronti del monumento

1848-2018 : 170esimo della posa della prima pietra. Ospedale Serbelloni di Gorgonzola. Architetto Giacomo Moraglia (1791 - 1860)

In occasione della ricorrenza dei 170 anni dalla posa della prima pietra dell'Ospedale Serbelloni di Giacomo Moraglia a Gorgonzola, mostra documentaria sulle vicende dell'architetto e dell'edificio attraverso gli anni, dal 1848 a oggi, evidenziando il ruolo di primo piano rivestito da questo progetto nel panorama dell'architettura ospedaliera in Lombardia in et\ue0 moderna e il ruolo chiave del cantiere nel contesto sociale e culturale del borgo di Gorgonzola, dove i Serbelloni hanno fatto edificare anche la chiesa parrocchiale e possedevano una residenza di villeggiatura

Modeling and design of a BES diagnostic for the negative ion source NIO1

Consorzio RFX and INFN-LNL are building a flexible small ion source (NIO1) capable of producing about 130 mA of H- ions accelerated at 60 KeV. Aim of the experiment is to test and develop the instrumentation for SPIDER and MITICA, the prototypes respectively of the negative ion sources and of the whole neutral beam injectors which will operate in the ITER experiment. As SPIDER and MITICA, NIO1 will be monitored with Beam Emission Spectroscopy (BES), a non-invasive diagnostic based on the analysis of the spectrum of the $H_\alpha$ emission produced by the interaction of the energetic ions with the background gas. Aim of BES is to monitor direction, divergence and uniformity of the ion beam. The precision of these measurements depends on a number of factors related to the physics of production and acceleration of the negative ions, to the geometry of the beam and to the collection optics. These elements were considered in a set of codes developed to identify the configuration of the diagnostic which minimizes the measurement errors. The model was already used to design the BES diagnostic for SPIDER and MITICA. The paper presents the model and describes its application to design the BES diagnostic in NIO1.Comment: 3 pages, 3 figures. Contributed paper for the ICIS 2013 conference. Accepted manuscrip

First Beam Characterization by Means of Emission Spectroscopy in the NIO1 Experiment

The NIO1 experiment hosts a flexible RF H- ion source, developed by INFN-LNL and Consorzio RFX to improve the present concepts for the production and acceleration of negative ions. The source is also used to benchmark the instrumentation dedicated to the ITER neutral beam test facility. Many diagnostics are installed in NIO1 to characterize the source and the extracted negative ion beam. Among them, Beam Emission Spectroscopy (BES) has been used in NIO1 to measure the divergence and the uniformity of the beam, together with the fraction of beam ions which was neutralized inside the acceleration system. The diagnostic method is based on the analysis of the Doppler shifted $H_\alpha$ photons emitted by the fast beam particles and collected along a line of sight. The article presents the experimental setup and the analysis algorithms of the BES diagnostic, together with a discussion of the first measurements and of their correlation with the operational parameters.Comment: 3 pages, 2 figures. Contributed paper for the ICIS 2017 conference. Accepted manuscript of a published pape

Electron Density and Temperature in NIO1 RF Source Operated in Oxygen and Argon

The NIO1 experiment, built and operated at Consorzio RFX, hosts an RF negative ion source, from which it is possible to produce a beam of maximum 130 mA in H- ions, accelerated up to 60 kV. For the preliminary tests of the extraction system the source has been operated in oxygen, whose high electronegativity allows to reach useful levels of extracted beam current. The efficiency of negative ions extraction is strongly influenced by the electron density and temperature close to the Plasma Grid, i.e. the grid of the acceleration system which faces the source. To support the tests, these parameters have been measured by means of the Optical Emission Spectroscopy diagnostic. This technique has involved the use of an oxygen-argon mixture to produce the plasma in the source. The intensities of specific Ar I and Ar II lines have been measured along lines of sight close to the Plasma Grid, and have been interpreted with the ADAS package to get the desired information. This work will describe the diagnostic hardware, the analysis method and the measured values of electron density and temperature, as function of the main source parameters (RF power, pressure, bias voltage and magnetic filter field). The main results show that not only electron density but also electron temperature increase with RF power; both decrease with increasing magnetic filter field. Variations of source pressure and plasma grid bias voltage appear to affect only electron temperature and electron density, respectively.Comment: 7 pages 4 figures. Contributed paper for the NIBS 2016 conference. Accepted manuscrip