Search

An overview of the recent operations and the main results of cesium injection in the Source for the Production of Ions of Deuterium Extracted from Rf plasma (SPIDER) negative ion source are described in this contribution. In experiments without cesium injection, all SPIDER plants were tested to verify the basic expectations on the operational parameters (e.g., electron cooling effectiveness of magnetic filter field) and to determine its operational region. For beam properties, it was shown that the current density varies across the beam in the vertical direction. In preliminary cesium experiments, the expected increase of negative ion current and simultaneous decrease of co-extracted electrons were found, along with the influence of the control parameters (polarization of the plasma electrodes, magnetic filter field) on the SPIDER beam uniformity in the horizontal and vertical directions. It was shown that non-Gaussian tails can be identified in the angular distribution on the plane perpendicular to the beam propagation direction. Stray particles, nonhomogeneous beam and large divergence might result in unexpected heat and particle loads over ITER neutral beam injector (NBI) accelerator grids; it is the goal of SPIDER to assess and possibly to identify suitable methods for controlling these beam features. A major shutdown, planned for late 2021, to solve the issues identified during the operation and to carry out scheduled modifications, is outlined. Such improvements are expected to allow SPIDER to pursue the ITER requirements in terms of negative ion current, electron-to-ion ratio, and beam duration.

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 paper

ITER envisages the use of two heating neutral beam injectors plus an optional one as part of the auxiliary heating and current drive system, to reach the desired performances during its various phases of operation. The 16.5 MW expected neutral beam power per injector is several notches higher than worldwide existing facilities.In order to enable such development, a Neutral Beam Test Facility (NBTF) was established at Consorzio RFX, exploiting the synergy of two test beds, called SPIDER and MITICA. SPIDER is dedicated developing and char-acterizing large efficient negative ion sources at relevant parameters in ITER-like conditions: source and accel-erator located in the same vacuum where the beam propagates, immunity to electromagnetic interferences of multiple radio-frequency (RF) antennas, avoidance of RF-induced discharges on the outside of the source. Three years of experiments on SPIDER have addressed to the necessary design modifications to enable full perfor-mances. The source is presently under a long shut-down phase to incorporate learnings from the experimental campaign, in particular events/issues occurred during operation, which led to the identification of improvement opportunities/necessities (e.g. RF discharges, local burns, water leaks, other damages, configuration/design upgrades to maximize chances/margin to quest target parameters).Parallelly, developments on MITICA, the full-scale prototype of the ITER Neutral Beam Injector (NBI) featuring a 1 MV accelerator and ion neutralization, are underway including manufacturing of the beam source, accel-erator and the beam line components, while power supplies and auxiliary plants, already installed, are under final testing and commissioning.Integration, commissioning and tests of the 1 MV power supplies are essential for this first-of-kind system, unparalleled both in research and industry field. 1.2 MV dc insulating tests of high voltage components were successfully completed. The integrated test to confirm 1 MV output by combining invertor systems, DC gener-ators and transmission lines extracted errors/accidents in some components. To realize a concrete system for ITER, said events have been addressed and solutions for the repair and the improvement of the system were developed.Hence, NBTF is emerging as a necessary facility, due to the large gap with existing injectors, effectively dedicated to identify issues and find solutions to enable successful ITER NBI operations in a time bound fashion. The lessons learned during the implementation on NBTF and future perspectives are here discussed.

The accurate mass spectrometry (with resolution goal 1:20000) of exotic ions requests beams with low energy spread (goal is about 0.5 eVrms or lower) and low transverse emittance, so it is necessary to cool ions produced by a fission source. In a radiofrequency (rf) quadrupole cooler (RFQC), collisions decrease ion kinetic energy, while rf and DC voltages confine and reaccelerate ions towards the extraction, where the cold ion beam is formed. Operation is based on carefully chosen tunings of voltages and of gas pressure p g, which requires an adequate pumping system; efficient simulations of extraction systems, which critically depend on residual speed of ions, are also important. Progresses in the experimental setup are described. Indications from simple ray tracing and ‘ray+collision’ tracing are compared. Results are applied to a simple triode extraction system, and more flexible configurations are considered.

This contribution describes the recent experimental results obtained at the high voltage (HV) Padova test facility (HVPTF), the laboratory able to carry out HV tests in vacuum up to 800 kVdc/1mA with a holding time of several hours per experimental session and aimed at developing the voltage holding capability of the Megavolt ITer Injector & Concept Advance (MITICA) accelerator, the prototype for the International Thermonuclear Experimental Reactor (ITER) neutral beam injector (NBI). The experiments described in this article refer to a double polarity symmetric configuration, a sphere-to-sphere electrode with an inter-electrode vacuum gap of 30 mm. The results showed that the onset of microdischarges can be ascribed to a mutual exchange of charged particles between specific accumulation points on electrode supports and the vacuum vessel rather than to a direct interaction between the spherical electrodes. The outcome of these experiments is reported and analyzed with both analytical and numerical models.

The Divertor Tokamak Test facility (DTT) will be a new experimental facility located at Frascati, Rome, Italy, whose main goal will be to have a better understanding on hot plasma interactions with plasma-facing components (PFCs) and aid in the development of ITER and successively DEMO. The improved conceptual design of the beamline for the DTT neutral beam heating (NBH) system is here overviewed, with a particular focus on the technical solutions adopted to fulfill the requirements and maximize beamline performances. The proposed system features a beamline providing deuterium neutrals (D⁰) with an energy of 510 keV and an injected power of 10 MW. Various design options have been considered, and a comprehensive set of simulations has been carried out using several physics and engineering codes to drive the choice of the most suitable design options and optimize them, aiming at finding a good compromise among different design requirements.

This topical review gathers the last updates concerning caesium-free negative ion sources presented during the $$63{\mathrm {rd}}$$ Course of the International school of Quantum Electronics of the Ettore Majorana Foundation and European collaborative works related to these lectures. Hence, beyond the frame of this course this topical review addresses both theoretical and experimental work performed during these last few years and complexities represented by the conception of a negative ion source ranging from the creation of negative ions to their neutralization.

The Linear IFMIF Prototype Accelerator (LIPAc) is a high intensity D+ linear accelerator; demonstrator of the International Fusion Material Irradiation Facility (IFMIF). In summer 2019 the IFMIF/EVEDA Radio Frequency Quadrupole (RFQ) accelerated its nominal 125 mA deuteron (D+) beam current up to 5 MeV, with 90% transmission for pulses of 1 ms at 1 Hz. This success was possible thanks to an intense previous campaign of modelization and measurements in order to characterize the RFQ input beam, which is affected by the ECR ion source extraction and the low energy beam transport. The simulation models used with the measurement benchmarks are here presented.

Energy recovery of residual ions may be needed to increase the energy efficiency of Neutral Beam (NB) injectors for fusion plants as DEMO while a deflection-based system has been proposed until now to dump residual ions. As an alternative, a compact beam energy recovery system, based on space charge effects due to the residual ion deceleration into 2 Farady Cups (FC) with holes for D0 passage, can replace the Electrostatic Residual Ion Dump (ERID) designed for ITER to stop the residual D- and D+ before the NB injection in the tokamak plasma. All parameter tunings and preliminary simulations are here described, also providing the suppression of back streaming to the ion source. Ion energy spread and rectangular geometry are considered. Collection of ions at low energy (a few percent of the full neutral beam energy Eki) instead of Eki as in ERID gives advantages that will be mentioned.

"Sent livers" (SL) (interregional allocated organs) are considered extended donor criteria grafts. These grafts influence post-transplant outcome. In our donor allocation program, the number of allocated SLs is increasing. The aim of our study is to provide data supporting the possibility to enlarge the use of SLs through adequate donor-to-recipient matching.A retrospective analysis was carried out from our prospective-collected database during 2014.Fifty-seven liver transplantations (LTs) were included: 22 SLs and 35 grafts procured by us (nSLs). Only donor risk index among donor characteristics showed a trend toward significant values (SL 1.901 vs nSL 1.726, P = .07). Among LT variables, the number of patients who received interleukin-2 inhibitor induction (SL 7 vs nSL 20, P .05) and the presence of hepatocellular carcinoma (SL 50% vs nSL 34%, P .05) reached statistical significance. One case of primary nonfunction occurred in the nSL group. No major retrieval injuries were observed. Retransplantation was performed in 6 cases (2 SLs and 4 nSLs). One patient in the SL group died after retransplantation. Graft survival rates at 1, 3, 6, and 12 months were 100%, 100%, 90%, 86% and 91%, 86%, 86%, 86% (P = .79) in SL and nSL groups, respectively.SL performance did not differ from that of nSL. SLs were usually allocated to noncritical candidates, and nSLs were transplanted more frequently in decompensated recipients. Despite this peculiar donor-recipient match, grafts survival was similar in the 2 groups of patients.

The next fusion project DEMO, which will be the evolution of the experimental fusion reactor [International Tokamak Experimental Reactor (ITER)], would require a high efficient energy production. As in ITER, DEMO will use fast Neutral Beam (NB) injectors to increase the plasma temperature needed for the fusion reaction. A way to recover the electric energy production efficiency in DEMO could be the beam energy recovery in the NB production, which is produced by a D− beam, neutralized by a gas cell with 60% efficiency. A compact energy recovery device with an axisymmetric cylindrical ion collector that uses only decelerating electric fields combined with the beam space charge effect has been recently proposed. It can be used for a test on the beam of the NIO1 (Negative Ion Optimization 1) source, a compact ion source (scaled down from ITER size sources) that has been developed at INFN-LNL and Consorzio RFX (Padua). The detailed collector design to be used on one of the beamlets of the NIO1 source within typical space limitation is presented and discussed here. Furthermore, a preliminary trajectory simulation for a beam with a rectangular geometry similar to the beam used in ITER to verify the beam recovery for a nonaxial symmetric geometry is also shown.The next fusion project DEMO, which will be the evolution of the experimental fusion reactor [International Tokamak Experimental Reactor (ITER)], would require a high efficient energy production. As in ITER, DEMO will use fast Neutral Beam (NB) injectors to increase the plasma temperature needed for the fusion reaction. A way to recover the electric energy production efficiency in DEMO could be the beam energy recovery in the NB production, which is produced by a D− beam, neutralized by a gas cell with 60% efficiency. A compact energy recovery device with an axisymmetric cylindrical ion collector that uses only decelerating electric fields combined with the beam space charge effect has been recently proposed. It can be used for a test on the beam of the NIO1 (Negative Ion Optimization 1) source, a compact ion source (scaled down from ITER size sources) that has been developed at INFN-LNL and Consorzio RFX (Padua). The detailed collector design to be used on one of the beamlets of the NIO1 source within ty...

The NIO1 (Negative Ion Optimization phase 1) source can provide continuous beam operation, which is convenient for systematic parameter and equipment studies. Even in the pure volume production regime, the source yield was found to depend on conditioning procedures. Magnetic configuration tests continued adding magnets to the existing setup; the filter field component Bx has been progressively extended to span the −12 to 5 mT range, and as a trend, source performances improved with |Bx|. The progress of camera beam diagnostics and of the quality of the volume-produced H− beam is also shown. The status, off-line results, and reliability of a first NIO1 cesium oven are discussed; other upgrades in preparation (cavity ring down spectrometer, the end calorimeter, and conceptual tests of the energy recovery system) are also listed.The NIO1 (Negative Ion Optimization phase 1) source can provide continuous beam operation, which is convenient for systematic parameter and equipment studies. Even in the pure volume production regime, the source yield was found to depend on conditioning procedures. Magnetic configuration tests continued adding magnets to the existing setup; the filter field component Bx has been progressively extended to span the −12 to 5 mT range, and as a trend, source performances improved with |Bx|. The progress of camera beam diagnostics and of the quality of the volume-produced H− beam is also shown. The status, off-line results, and reliability of a first NIO1 cesium oven are discussed; other upgrades in preparation (cavity ring down spectrometer, the end calorimeter, and conceptual tests of the energy recovery system) are also listed.

A Radio Frequency Quadrupole Cooler (RFQC) prototype was adapted for insertion into a high uniformity magnetic field, with Bz up to 0.2 T, to improve radial confinement. While the RFQC purpose is to reduce (by gas collisions) the energy spread and emittance of a beam of radioactive nuclei, to finely select ion mass in nuclear physics, the prototype is tested in a setup including a stable ion source, a pepper pot emittance meter, and two Faraday cups; this makes a precise characterization of the RFQC feasible. The ion extraction was studied in detail by simulations, both to match it to the emittance meter granularity and to verify the effect of the typical nonuniformity of the longitudinal electric field Ez inside the RFQC; an average motion description (including friction force from gas collisions) was used, introducing the ballistic and diffusive regimes. With a preliminary optimization of the electrode shape, buffer gas pressure pg, and radio frequency voltage, the ion beam can be extracted with a significant cooling margin.

Beam tomography is a non-invasive diagnostic that allows us to reconstruct the beam emission profile by measuring the light emitted by the beam particles interacting with the background gas, along an elevated number of lines of sight, which is related to the beam density by assuming a uniform background gas. In the framework of the heating and current drive of future nuclear fusion reactors, negative ion beams of hydrogen and deuterium are required for neutral beam injectors (NBIs) due to their elevated neutralization efficiency at high energy (in the MeV range). Beside the beam energy, beam divergence and homogeneity are two critical aspects in the design of future NBIs. In this paper, the characterization of the negative ion beam of the negative ion source NIO1 (a small-sized radio-frequency driven negative ion source, with 130 mA of total extracted H - current and 60 kV of maximum acceleration) using the tomographic system composed of two visible cameras is presented. The Simultaneous Algebraic Reconstruction Technique (SART) is used as an inversion technique to reconstruct the 3 × 3 matrix of the extracted beamlets, and the beam divergence and homogeneity are studied. The results are compared with the measurements of the other diagnostics and correlated with the source physics. The suitability of visible cameras as a diagnostics system for the characterization of the NIO1 negative ion beam is a small-scale experimental demonstration of the possibility to reconstruct more complicated multi-beamlet profiles, resulting in a powerful diagnostic for large NBIs.

At Legnaro National Laboratories of INFN is under construction a Rare Isotope Facility called "Selective Production of Exotic Species" (SPES) based on a 35-70 MeV proton cyclotron, able to deliver two beams with a total current up to 0.75 mA, an ISOL fission target station and an existing ALPI superconducting accelerator as a post accelerator (up to 10 MeV/u for A/q=7). The paper will cover notably: the high-resolution mass separator, the CW RFQ (80 MHz, 727 keV/u, with internal bunching), the 1+ low energy transfer line and the injection line from Charge Breeder to ALPI under installation., Proceedings of the 14th Int. Conf. on Heavy Ion Accelerator Technology, HIAT2018, Lanzhou, China

The purposes of the SPES (Selective Production of Exotic Species) project at INFN laboratory in Legnaro (Italy) is to study nuclei close to the drip lines. Therefore, a High Resolution Mass Separator (HRMS) must provide full separation of the ions with a resolution 1/20000, to be sensible to the proton’neutron mass difference. SPES HRMS is consisting of: two 90° magnet dipoles, one electrostatic multipole in between them, six electrostatic quadrupoles, two electrostatic hexapoles and two electrostatic triplets before and after the slits on the object and image point. All these components will be installed on a high voltage platform with a maximum operating voltage of -240 kV. Before entering the HRMS, a 40 keV energy beam go through an RFQ Cooler, designed to have an output energy spread of 1 eV. Mass separation within target resolution is the most critical part: dipoles must provide a magnetic field homogeneity of 4 E-5 throughout beam occupancy (half magnet pole surface), at a field intensity of 0.56 T for the reference ion 132 Sn. Therefore, a very accurate dipole design is mandatory. This contribute will show the key points which lead to the final HRMS layout and dipole design., Proceedings of the 14th Int. Conf. on Heavy Ion Accelerator Technology, HIAT2018, Lanzhou, China

Although survival after liver transplantation (LT) has progressively improved over the last years, an increased prevalence of clinically relevant infections in LT patients is well documented. In particular, the spread of infections sustained by extensively drug-resistant bacteria (XDR) produced an increase in the incidence of wound infections. Implementation of treatments for these life-threatening events is mandatory. This study describes 2 LT patients in whom XDR wound infection was effectively treated using negative pressure wound treatment (NPWT) combined with targeted local and systemic antibiotic therapy. Over the last 3 years, 2 of 8 patients with XDR infection admitted to our unit developed wound infection caused by XDR Klebsiella pneumoniae (KP-XDR). Positive results of the abdominal fluid culture and of the wound swab for KP-XDR were followed by sepsis. In both cases wound debridement was required and deep fascial layer dehiscence was detected. Combination antibiotic therapy was administered for sepsis treatment and, after failure of conventional NPWT, a NPWT with local instillation (NPWTi; V.A.C.-Ulta/VeraFlo-Instillation Therapy-KCI USA, Inc., San Antonio, TX, USA) of colistin-rifampicin was applied. After NPWTi application a reduction in bacterial load and exudate was observed with reduction in inflammatory markers. A complete healing of wound was achieved and both patients are currently alive. Instillation and NPWT are widely discussed in the literature. Results of the present study indicate beneficial effects of NPWT combined with targeted local and systemic antibiotic therapy; in both cases a life-threatening complication was cured. We consider local instillation of selected antibiotics applied to NPWTi a valuable tool for deep wound infection sustained by XDR bacteria.

The extraction of negative ions request conditions such as electrons are magnetized, so that a collisionless model is clearly overoptimistic, and collisions must be included to model electron co-extraction (an undesired effect). Collision dependence from speed is fully treated in this paper, addressing also the difficult case of Coulomb collisions. The kinetic effects are important in the sheath and presheath region, giving integral equations for electron density, current and collision variation along extraction axis z. With a careful description of the closed orbit variables and of the recirculation effect, integral kernels are reduced to expression suitable for computation. Numerical results for the plasma conductivity and average emission angle in Coulomb collision dominated regime are given and compared with similar results of constant collision frequency models.The extraction of negative ions request conditions such as electrons are magnetized, so that a collisionless model is clearly overoptimistic, and collisions must be included to model electron co-extraction (an undesired effect). Collision dependence from speed is fully treated in this paper, addressing also the difficult case of Coulomb collisions. The kinetic effects are important in the sheath and presheath region, giving integral equations for electron density, current and collision variation along extraction axis z. With a careful description of the closed orbit variables and of the recirculation effect, integral kernels are reduced to expression suitable for computation. Numerical results for the plasma conductivity and average emission angle in Coulomb collision dominated regime are given and compared with similar results of constant collision frequency models.

In June 2018 the SPIDER device, which is the full-size prototype of the negative ion source and extractor for the ITER Heating Neutral Beam has entered the first operation phase at the Neutral Beam Test Facility (NBTF) in Padova, Italy. This paper describes the present status of the device, the experimental plans and the results obtained during the first experimental campaign of the radio-frequency driven plasma source.

The negative ion source NIO1, at Consorzio RFX in Padova (Italy), is aimed at investigating general issues on ion source physics, as well as innovative solutions for electrical efficiency, in view of their use as sources of neutral beam injectors (NBIs) in future fusion experiments, like MITICA, the ITER NBI prototype. Since no cesium has been used yet, in NIO1 the negative ion production relies on the volume process only. In order to maximize its efficiency, some solutions have been proposed. Inside the source chamber, in front of the plasma grid, an electrically insulated bias plate has been installed, which can be independently biased with respect to the plasma grid or, in turn, with respect to the source walls. The original magnetic filter field configuration (generated by current flowing through the plasma grid and external return coil), has been modified in order to increase its absolute value inside the source chamber, using a different configuration of the cusp field magnets. The aim of this contribution is to show the beneficial effect of these two design solutions in improving negative ion current and reducing the extracted electron current in NIO1.

Localized heating has been observed in unexpected positions on anodic surfaces in a multi-electrode device insulated by vacuum gaps. In double polarity experiments, a counter-intuitive behavior of current-voltage characteristic has also been observed. The phenomena could depend on a cascade effect of charged particles exchanged between electrodes and on a mutual correlation of particle trajectories between electrode surfaces occurring during the high voltage conditioning phase. Attractors regions ascribed to regenerative processes of charged particles between cathode and anode have been identi fi ed thanks to numerical simulations The position of the attractors depends only on electrode shape and the ratios of applied voltages. This fi nding suggests new perspectives in neutrons sources applications, where recurrent impacts of focused high energy hydrogen isotopes take place on solid hydride targets supported by metallic electrodes insulated by vacuum gaps.

Negative ion plasma sources (H− for example) typically emit also electrons, depending on magnetic fields and collisions. Theoretical models (mostly 1D in space) can clarify the transition from collisional regime to other regions. A full numerical analysis of the 3D geometry of the extraction is hindered by the computational load and by the rapidly growing electric field towards extraction, while theoretical analysis should include solution of equation in the phase space and adequately simplified models of collisions. The case of Coulomb collision is here added to the previously discussed terms for electron-gas collisions (constant mean free path or collision frequency), including the large divergence of its cross section in the low speed limit. Preliminary results for related transport integrals show that divergences are greatly suppressed by the averaging and integration process, and restricted to particular orbits, confirming gas collision results for low ionization plasma presheath.

Negative ion sources are the first stage of several types of accelerators, ranging from medical applications to materials testing and to heating systems for nuclear fusion devices. One of the most important aspects of the sources is the amount of extracted ion current, which depends on the extraction voltage and on the availability of ions inside the source plasma; this situation is described by the Child-Langmuir law. The extraction of ions from the source is facilitated by an initial ion velocity. In the case of negative ions, plasma electrons also play a role in the definition of the maximum extractable ion current, which can be significantly decreased for the possibly combined effects of large electron current and magnetic field configuration. The present contribution gives a comprehensive theory of the electrostatic extraction of particles from the meniscus, the plasma boundary which forms at the apertures of a negative ion source in the aforementioned conditions. A normalised treatment is adopted, which is suitable for application to different types of plasmas. Data from the flexible multi-aperture RF-based caesium-free negative ion source NIO1 are studied, which exhibit saturation in the extracted current depending on the plasma parameters both in hydrogen and in oxygen. This work has been carried out within the framework of the EUROfusion Consortium and has received funding from the Euratom research and training programme 2014-2018 under grant agreement No 633053. The views and opinions expressed herein do not necessarily reflect those of the European Commission.

After installation of Mo liners in the source NIO1 (Negative Ion Optimization phase 1), hydrogen plasmas in a continuous regime operation (much longer than one hour) are routinely maintained, with more than 1 kW rf power and 0.5 Pa pressure, allowing a systematic investigation of pure H− volume effect, which requests a much lower acceleration voltage Vs ≅ 12 kV than future Cs operations at Vs ≅ 60 kV. A new extraction grid EG was installed (replacing some eroded insulators) and preliminary beam images are compared to old EG ones, discussing effects of different deflection field strength and need of intermediate values. Large improvements in beam diagnostics and the effect of installation of a cryogenic pump are also reported.

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 called NIO1 (Negative Ion Optimization, phase 1) is operated at Consorzio RFX since 2014 [1], [2]. At this stage H- are mainly formed by volume processes, while the use of cesium vapour to enhance the surface production is forseen in a second stage. The plasma is sustained by a 2.5 kW RF generator, inductively coupled via a seven turn coil surrounding the plasma chamber. The production and survival of negative ions stronlgy 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, power electric and magnetic field strenght in the source a dedicated campaign with a movable Langmuir probe immersed in the plasma was carried out. This paper firstly reports on the installation of such probe on NIO1 and on the development of its control and acquisition system. The data aquired in different source conditions are then presented and discussed.

The ITER tokamak requires two injectors of neutral beams resulting from the neutralisation of accelerated negative hydrogen/deuterium ions. To optimise the source operation, a specific test facility ("PRIMA") was established in Padova, comprising the experiment SPIDER (full-size negative ion source with 40A beam, 100keV particle energy). The design of SPIDER accelerator was based on the most advanced numerical codes available for the investigation of the expected beam properties. Several diagnostic systems will characterise source and beam during the experiments. In view of the operation, this paper describes the preparation of the experiments by means of numerical simulations of the accelerator. The simulations provide also estimates of the current and power deposited onto the accelerator grids and will be the basis for further work aimed at computing the expected measurements by the various beam diagnostics.

In order to reduce the beam losses of the negative ion beam in the NIO1 experiment, the vacuum system was improved by installing an additional cryogenic pump. In the upgraded configuration, the negative ion beam can be operated in two regimes of high and low background pressures. The gas flow in the improved configuration was simulated, characterizing the existing pumping system and verifying the best configuration for the improved pumping scheme. The charge state of the negative ion beam moving through the background hydrogen gas is calculated, thus providing the stripping losses inside the accelerator and in the transport region. The expected values are compared with the experimental data obtained with a diagnostic beam dump, a one-dimensional carbon fiber calorimeter, and other beam-plasma diagnostics measuring the parameters of the secondary plasma. The collected electric current and the heat flux reconstructed from thermal measurements are compared with the expected beam particle flux. The measurements indicate as expected an increase of negative ion current at full acceleration and a decrease of the plasma electron contribution.

The ion source NIO1 (Negative Ion Optimization 1) was developed and installed as a reduced-size model of multi-aperture sources used in neutral beam injectors. NIO1 beam optics is optimized for a 130 mA H- current (subdivided in 9 beamlets) at a Vs=60 kV extraction voltage, with an electron-to-ion current ratio Rj up to 2. In an initial phase, NIO1 was operated with Vs=0 to verify the coupling of radiofrequency (rf) power Pf to plasma. The distinction between capacitively coupled plasma (E-mode, consistent with a low electron density plasma ne) and inductively coupled plasma (H-mode, requiring larger ne) was clearly related to several experimental signatures, especially for air or nitrogen plasmas, where E to H transition was observed with Pf about 0.5 kW (with hysteresis). In hydrogen, the same transition may require about 1 kW, so that air cooling of the rf window was improved. Beams of H- and O- were separately extracted (using pure gases as input); since no caesium is yet introduced into the source, the expected ion currents are typically lower than 10 mA; this requires a lower acceleration voltage Vs (to keep the same perveance). Operation at lower voltages and current (as appropriate in this phase) is possible, but use of weaker deflection magnets in the extraction grid (EG) or use of heavier gases (oxygen) is then advisable. Preliminary experiments indicate the need of increasing the ampere-turns in magnetic filter and the bias voltage to reduce Rj (still very large, about 150 for oxygen), in qualitative agreement with theoretical and numerical models. In a separate test stand, NIO1 caesium oven was tested, with deposition on a molybdenum substrate, and advanced Cs dispensers are in development.

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.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.

In the framework of the accompanying activities in support to the ITER NBI test facility, a relatively compact radiofrequency (RF) ion source, named NIO1 (Negative Ion Optimization, phase 1) was developed in Padua, Italy, in collaboration between Consorzio RFX and INFN. Negative hydrogen ions are formed in a cold, inductively coupled plasma with a 2MHz, 2.5 kW external antenna. A low electron energy is necessary to increase the survival probability of negative ions in the proximity of the extraction area. This goal is accomplished by means of a transversal magnetic field, confining the high energy electrons better than the colder electrons. In NIO1, this filter field can cover different topologies, exploiting different set of magnets and high current paths. In this contribution we study the property of the plasma in the vicinity of the extraction region for two different B field configurations. For this experiment the source was operated in pure volume conditions, in hydrogen and oxygen plasmas. The experimental data, measured by spectroscopic means, is interpreted also with the support of finite element analyses simulations of the magnetic field and a dedicated particle in cell (PIC) numerical model for the electron transport across it, including Coulomb and gas collisions.

The RF negative ion source NIO1, built at Consorzio RFX in Padua (Italy), is aimed to investigate general issues on ion source physics in view of the full-size ITER injector MITICA as well as DEMO relevant solutions, like energy recovery and alternative neutralization systems, crucial for neutral beam injectors in future fusion experiments. NIO1 has been designed to produce 9 H- beamlets (in a 3x3 pattern) of 15mA each and 60keV, using a three electrodes system downstream the plasma source. At the moment the source is at its early operational stage and only operation at low power and low beam energy is possible. In particular, NIO1 presents a too strong set of SmCo co-extraction electron suppression magnets (CESM) in the extraction grid (EG) that will be replaced by a weaker set of Ferrite magnets. A completely new set of magnets will be also designed and mounted on the new EG that will be installed next year, replacing the present one. In this paper, the finite element code OPERA 3D is used to investigate the effects of the three sets of magnets on beamlet optics. A comparison of numerical results with measurements will be provided where possible.

In most ray tracing simulation codes of the extraction region of a negative ion source, the particle initial velocity must be assigned by some simplified empirical models, in complete analogy with a positive ion source, which makes efficient two-dimensional (2D) and 3D three-dimensional simulations possible. Since electron emission from adequately magnetized plasma is due to collisions, not included in the pure ray-tracing codes, more complete physical models of the presheath plasma are discussed to get insight of electron velocity entering the sheath and the beam region. Full kinetic 1D2V (one space dimension, two velocity components) models are here presented. A reduced one-dimensional (1D) integrodifferential model of a simplified kinetic equation (in two velocity components) including magnetic field and effective collisions, recently analytically described, is extended to the case of constant collision frequency; in z, pz phase space, closed orbits enhance electron density, as calculated. Introducing the escape integral limit, the expected trends of electron emission velocity and angle are given.In most ray tracing simulation codes of the extraction region of a negative ion source, the particle initial velocity must be assigned by some simplified empirical models, in complete analogy with a positive ion source, which makes efficient two-dimensional (2D) and 3D three-dimensional simulations possible. Since electron emission from adequately magnetized plasma is due to collisions, not included in the pure ray-tracing codes, more complete physical models of the presheath plasma are discussed to get insight of electron velocity entering the sheath and the beam region. Full kinetic 1D2V (one space dimension, two velocity components) models are here presented. A reduced one-dimensional (1D) integrodifferential model of a simplified kinetic equation (in two velocity components) including magnetic field and effective collisions, recently analytically described, is extended to the case of constant collision frequency; in z, pz phase space, closed orbits enhance electron density, as calculated. Introducing ...

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., 7 pages 4 figures. Contributed paper for the NIBS 2016 conference. Accepted manuscript

Commercial viability of thermonuclear fusion power plants depends also on minimizing the recirculation power used to operate the reactor. The neutral beam injector (NBI) remains one of the most important method for plasma heating and control. For the future fusion power plant project DEMO, a NBI wall plug efficiency at least of 0.45 is required, while efficiency of present NBI project is about 0.25. The D(-) beam from a negative ion source is partially neutralized by a gas cell, which leaves more than 40% of energy in residual beams (D(-) and D(+)), so that an ion beam energy recovery system can significantly contribute to optimize efficiency. Recently, the test negative ion source NIO1 (60 keV, 9 beamlets with 15 mA H(-) each) has been designed and built at RFX (Padua) for negative ion production efficiency and the beam quality optimization. In this paper, a study proposal to use the NIO1 source also for a beam energy recovery test experiment is presented and a preliminary design of a negative ion beam collector with simulations of beam energy recovery is discussed.

The self-potential of a high current ion beam may be fairly balanced by a secondary plasma with plasma potential Vp; the retarding field energy analyzer (RFEA) measuring the secondary ion outflow is a promising diagnostic of these plasmas. A detailed analysis of a planar RFEA is here discussed, with a focus on the response (in stationary condition) of the detector to the secondary plasma characteristics, and on the determination of design rules for the parameters of a compact RFEA. First, energy distributions of the secondary ion plasma outflow are discussed, as a function of ion temperature Ti and electron temperature Te. Second, the modulation of grid potential (depending on grid pitch b and wire radius a) is calculated both for 2D and 3D models, reaching a good agreement with accompanying electrostatic simulations. Beam emittance (or temperature) growth and beam diffusion are then discussed, also when input ion energy matches the discrimination voltage Vd; corrections to the usual paraxial dynamics result are then introduced. As regards the response of the whole detector (also called transmission function) and the beam dynamics evolution, systematic 3D multiparticle simulations were performed in order to study the behavior of the detector as a function of Vd and of the secondary plasma parameters Vp, Ti and Te and to determine the design parameter effects on instrumental precision (found to be about 0.1 b |Ez| with Ez the axial field near grids).

SPIDER is one of the two projects of the ITER Neutral Beam Test Facility (NBTF) under construction in Padova, Italy, at Consorzio RFX premises; it is the full-size prototype of the radiofrequency (RF) ion source for ITER Neutral Beam Injector (NBI), with beam energy of 100keV, designed to operate with pulse length up to 3600 s, featuring ITER-like filter field configuration, caesium oven layout and a wide set of diagnostics. These features will allow reproducing the ion source operation like in ITER as cannot be done in any other existing test facility. SPIDER realization is well advanced and the first operation is expected at the beginning of 2018, with the mission to prove the possibility of achieving the ITER NBI ion source target requirements and of improving its performance in terms of reliability and availability. This paper mainly focuses on the preparation of the first SPIDER operations: integration and testing of SPIDER components, completion and implementation of diagnostics and control and workout of operation and research plan, based on a staged strategy.

Neutral Beam Injectors (NBI) based on negative ion conversion are fundamental to increase the plasma temperature in magnetic confinement fusion devices.. In the framework of the accompanying activities in support to the ITER NBI test facility a relatively compact radiofrequency (RF) ion source, named NIO1 (Negative Ion Optimization phase 1) is being developed and tested in Padua, Italy, in collaboration between Consorzio RFX and INFN. This contribution reports the recent status of the experiment, including the operation in air and oxygen and the first beam measurements. Future improvements to enhance the negative ion current and reduce the amount co-extracted electrons are also discussed.

Uncontrolled donors after circulatory determination of death (uDCDD) represent a yet unexplored pool of organs potentially available for transplantation. The aims of this study were to validate a protocol of cardiac death in the pig and to investigate lung function during the process.Cardiac death was induced in preanesthetized animals with an injection of 600 mg propofol; once systolic blood pressure was 50 mm Hg (Agonal Phase), a 20 mEq bolus of KCl was given and, after asystolia was documented, cardiopulmonary resuscitation (CPR) started, followed by 5 minutes no touch (end-CPR). Invasive blood pressure (BP) and heart rate (HR) were recorded; blood samples taken at baseline, 15 minutes after CPR, and after the no touch period (end-CPR). Computed tomography (CT) scans were taken at baseline and at end-CPR.Agonal phase was reached in 6 ± 1 minutes and lasted 3 ± 1 minutes; average HR was 49 ± 16 beats/min, and BP was 41 ± 12 mm Hg. CPR lasted 35 ± 3 minutes; average HR and BP were 113 ± 32 beats/min and 86 ± 63 mm Hg, respectively. PaO2/FiO2 decreased from 442 ± 31 mm Hg at baseline to 63 ± 36 at end-CPR (P .001). pH decreased from 7.378 ± 0.045 to 6.931 ± 0.042 (P .001), with a corresponding increase of lactate from 0.9 ± 0.2 to mmol/L to 12.8 ± 2.1 (P .001). As assessed using CT scan, total lung volume decreased (baseline vs end-CPR 1107 ± 106 mL vs 617 ± 95; P .001), whereas noninflated tissue (ie, atelectasis) significantly increased (46 ± 10 g vs 131 ± 89; P = .008).Lung function greatly deteriorated after cardiac death. The model we set may constitute a reproducible platform for future investigations on lung uDCDD.

High-space charge effects and problems related to beam transport are discussed in the context of an electron cyclotron-resonance ion sources extraction and pre-acceleration low emittance line (which works as the injector of a new superconducting Radio Frequency Quadruple (RFQ) under commissioning at Laboratori Nazionali di Legnaro (LNL)) at several values of the extracted beam current. In the extractor, both the cases of short-range magnetic fringe field (virtual source approximation) and large-range fringe field are simulated. Analytical expression of ion flow and plasma sheaths are easily incorporated in the charged fluid approach and in numerical modeling with three-dimensional simulation programs, which can treat several coupled field variables and lower space dimension (known as multiphysics codes). Advantages of flexibility and of representation of finer details are remarked. Effects of plasma potential and extraction hole thickness (0.5 mm) on the plasma meniscus can be resolved, even in the contex...

An investigation of the ions induced diocotron instability in an electron plasma confined in a Malmberg–Penning trap is presented. The detection of the instability is based on the spectral analysis of the induced charge signals on the walls of the confining electrodes, which allows tracking of the plasma displacement from the axis. The dependence of the instability on the electron energy is analysed by three different methods: (i) injecting electrons with different energies, (ii) heating the electrons with a single radio frequency burst, (iii) varying the ramp-up time of the confining voltage. An experimental technique to limit the ion resonance instability, based on the application of suitable potentials on a set of electrodes, is presented.

A systematic analysis of the charge state distribution (CSD) of each element (or isotope) X extracted from a highly charged ion source as a function of control variables or time needs properly automated tools for the large amount of data involved and the possibility of peak superposition, due to the mass separator properties. Some key features of identification of ion currents with the new program DAT2PEAK are discussed here. A preprocessor LECR2DAT reads files of experimental scans. To obtain a reliable identification of element X and charges i several filtering and calibration routines were necessary; principles of their robust algorithms are discussed. Moreover, the concept of constrained fit allows one to use information both from superposed peak and single ion peak and to select different fit laws of CSD for each element X. A robust rule to distribute the current of superposed peaks to related elements is also presented. For each measurement processed, DAT2PEAK produces a listing of peaks and CSDs and updates the history files for the convenience of following statistical analysis.

The ELTRAP device installed at the Department of Physics of the University of Milan is a Malmberg–Penning trap, with a magnetic field up to 0.2 T, equipped with charge coupled device optical diagnostics. It is intended to be a small scale facility for electron plasma and beam dynamics experiments, and in particular for the study of collective effects, equilibrium states, and the formation of coherent structures in these systems. The device features a relatively long solenoid, corrected by 4 shims and 16 dipole coils, in order to obtain a large uniform magnetic field region. The modular electrode design allows several variations of the experimental configuration. The first experiments which assess the operation of the facility are described. Plasma confinement times up to several minutes have been obtained and an electron temperature of 4–8 eV has been measured.

The charge state distribution (CSD) of an electron cyclotron resonance (ECR) ion source in a good vacuum regime is here expressed in two closed forms; solution parameters a and b are related to quantities, here tabulated for some elements, expressing the trends of ionization cross sections with the charge state i and the plasma electron temperature T h . Difference of this CSD from a maxwellian distribution and its relation to the double exponential distribution are noted. The momenta and the generating function of the charge distribution are computed, so that ionization and thermal balance can be computed and many element effects can be studied; optimal element mixing can be derived. Simple relation between the charge state and the efficiency of the ECR charge breeders are also obtained.