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The NIO1 (Negative Ion Optimization 1) source is developing a systematic test programme of magnetic configurations, including permanent magnet filter up to 15 mT dipole strength, tunable current filter up to 3 mT strength (parallel or perpendicular to the previous), and ion deflection compensation system in the extraction gaps. Results for both perpendicular and parallel configurations are presented. The radiofrequency (rf) system takes full advantage of the programmable frequency amplifier capability, to start the plasma and later to optimize coupling with plasma. Operation experience with borosilicate rf window and improved power limit are reported, as well breakdown voltages Vbr are discussed, together with improvements obtained with the installation of a cryogenic pump. The interrelation between bias voltage, bias plate current and magnetic configuration is outlined; cesium evaporators are in advanced development. Major diagnostic systems (including cameras and emission spectrometers) have been integrated with the acquisition system along with the data measured by several power supplies (including the high voltage supplies, the rf generator and bias supplies, the pressure measurements and the beam currents): among the several diagnostic used, the role of simple current measurement and some optical observation are noted. [ABSTRACT FROM AUTHOR]

The use of caesium vapour is mandatory in plasma sources for negative ion beams to achieve a sufficient negative ion density. In the SPIDER ion source, three caesium ovens will provide a sufficiently high caesium flux to the walls of the ion source, but also a relatively even caesium distribution in the ion source. In order to ensure the caesium ovens are operating properly in terms of repeatability of the evaporated caesium flow, and to characterize the caesium flux emitted from its nozzles, a CAesium Test Stand (CATS) was equipped with a set of diagnostics. This paper reports the present configuration of the diagnostic set-up. Surface ionization probes are installed in front of the nozzle apertures. Movable surface ionization detectors are installed to reconstruct the angular distribution of the emission. A quartz microbalance is installed at a fixed position, to measure the cumulated caesium flux. Finally, the laser absorption spectroscopy measures the line-integrated caesium density. An example of these combined measurements is presented. [ABSTRACT FROM AUTHOR]

The NIO1 (Negative Ion Optimization, phase 1) experiment is a versatile test bench with goal of delivering a negative hydrogen beam current of 135mA accelerated to -60kV and divided into 9 beamlets. NIO1 is operated by Consorzio RFX and INFN in the framework of the activities aimed at the enhancement of negative ion sources for production of large ion beams for plasma heating in nuclear fusion devices and accelerator applications. For the NIO1 device an Acquisition, Data Retrieval, Interlock and Control (ADRIC) system was realised. The present paper gives a detailed description of the overall structure of ADRIC, which integrates together the various components; the single parts are also described, particularly highlighting the adoption of novel equipment. A special asset of this system is its flexibility when adding new components. [ABSTRACT FROM AUTHOR]

In view of the future experiments on the large ion sources used for the neutral beam injection system of ITER and DEMO reactor, a small scale negative ions source NIO1 (negative ion optimization, phase 1) is operated at Consorzio RFX since 2014. At this stage H- are mainly formed by volume processes, while the use of cesium vapor to enhance the surface production is foreseen in second stage. The plasma is sustained by a 2.5 kW RF generator, inductively coupled via a seven turn coil surrounding the plasma chamber using 2 MHz frequency. The production and survival of negative ions strongly depends on the plasma properties in the vicinity of the apertures from which particles are extracted and a beam is formed. In order to characterize these properties against the variable pressures, input power and magnetic field strength in the source a dedicated campaign with a movable Langmuir probe immersed in the plasma was carried out. In this paper the installation of such probe on NIO1 is described, and the data acquired in configuration of the magnetic field are then presented and discussed. [ABSTRACT FROM AUTHOR]

One of the main concerns when working with negative ion beams is collimation during propagation. The beam is composed of like charged particles; therefore they tend to repel each other causing the beam to widen after acceleration. In environments where the beam needs to travel long distances before reaching its target, the compensation of its space charge is necessary; the most straightforward way of achieving this is the creation of a plasma around the beam, created by ionization of the background gas by the beam itself. This effect, called space charge compensation, plays therefore a key role in the beam propagation and a deep understanding of this phenomenon is fundamental when operating negative ion sources. In order to perform measurements of the particles forming such beam-generated plasma, a retarding field energy analyzer (RFEA) can be adopted, which is an indirect non perturbing instrument, analysing the particles emitted radially from the beam plasma, and allowing to estimate the plasma parameters from the energy distribution function of ions and electrons. The paper presents the design and the layout of the system for voltage control and data acquisition of the RFEA, developed at Consorzio RFX and used for the experimental campaigns in NIO1 to study the phenomena that cause space charge compensation. [ABSTRACT FROM AUTHOR]

Enhancement of negative ion sources for production of large ion beams is a very active research field nowadays, driven from demand of plasma heating in nuclear fusion devices and accelerator applications. As a versatile test bench, the ion source NIO1 (Negative Ion Optimization 1) is being commissioned by Consorzio RFX and INFN. The nominal beam current of 135 mA at -60 kV is divided into 9 beamlets, with multiaperture extraction electrodes. The plasma is sustained by a 2 MHz radiofrequency power supply, with a standard matching box. A High Voltage Deck (HVD) placed inside the lead shielding surrounding NIO1 contains the radiofrequency generator, the gas control, electronics and power supplies for the ion source. An autonomous closed circuit water cooling system was installed for the whole system, with a branch towards the HVD, using carefully optimized helical tubing. Insulation transformer is installed in a nearby box. Tests of several magnetic configurations can be performed. Status of experiments, measured spectra and plasma luminosity are described. Upgrades of magnetic filter, beam calorimeter and extraction grid and related theoretical issues are reviewed. [ABSTRACT FROM AUTHOR]