The tutorial presents the Bo2022 database, a tool that collects - and will continue to collect in the future - Padua's academic population over the eight centuries of its history. The research project BO2022,from which this database was born, began in 2019 and ended in February 2021, and one of its aims was to map the academic population from the foundation of the University of Padua, in 1222,...
Fundamental processes related to negative ion formation by
volume production, surface production, and
double charge exchange production
of different ion species, such as hydrogen, helium, alkali metals, and halogens will be presented, together with their application.
The beam divergence is the figure of merit applied to quantify the width of the particle angular distribution as they travel along the beamlines of neutral beam injection (NBI) systems. In the case of the high power neutral beam planned for the ITER experiment, a divergence of less than 7 mrad is mandatory to assure the power level needed for plasma heating in ITER.
In the last decades, the...
As with all Neutral Beam injection into tokamaks, the ITER Heating Neutral Beam (HNB) beamline must ensure that the effect of the magnetic field is minimised in order for the pre-neutralised beam to avoid significant deflection which, when later neutralised, will enable it to pass through into the tokamak plasma without damaging the beamline. Due to the strength and range of the ITER magnetic...
A negative hydrogen (H$^-$) ion source with the plasma excited by 2 MHz radio frequency (RF) power serves as the beam source for the Japan Proton Accelerator Research Complex (J-PARC). We have been studying the H- ion beam intensity modulation at the frequency of plasma excitation RF power since we have found the beam carried the fluctuation at 2 MHz after the RFQ linac [1]. Higher frequency...
In NNBI ion sources neutral hydrogen atoms and positive ions impact on low work function grid surfaces, where they are converted to negative ions and subsequently extracted. Knowledge and control of the positive ions flux is hence crucial for optimizing the negative ion yield and also for benchmarking numerical models. To this end a Mach probe diagnostic can be used, which determines the...
The Los Alamos Neutron Science Center (LANSCE) H- ion source has provided stable output for decades of LANL mission needs, but its maximum beam output has remained the same at ~15 mA. A roadblock to improving beam output has been a lack of thorough understanding of the internal mechanisms of LANSCE H- ion source. The LANSCE H- Ion Source Laser Diagnostic Stand (HLDS) was recently built and...
The ELISE test facility with its half ITER-size ion source is an essential part of the European Roadmap towards the ITER NBI system. One aim of ELISE is to demonstrate the ITER target values for the extracted current density, the ratio of co-extracted electrons to extracted ions and the uniformity of the extracted beam during long pulses, i.e. 1000 s in hydrogen and 3600 s in deuterium and at...
MITICA, the full scale prototype of ITER Heating Neutral Beam (HNB), is under realization at the Neutral Beam Test Facility (Padova, Italy). MITICA Power Supply is a very complex system, composed of several non-standard equipment, beyond the present industrial standard for insulation voltage level (-1MVdc) and dimensions. Procured by European and Japanese Domestic Agencies, it consists of five...
Inductive coupling of radiofrequency power to plasma is a complicate process, since it depends from the density of plasma itself for two major reason: (1) ionization is a chain reaction process; (2) with no Faraday screen (as in many sources and until now NIO1), a capacitative coupling may mix with inductive coupling. Several empirical 2D model can be developed, depending on collisional...
A higher density of the negative ion in front of the plasma beam boundary is important to extract a higher beam current density in the negative hydrogen ion source. Negative ions are mainly produced on the surface of the plasma-facing grid electrode (PG) in cesium seeded negative ion source for fusion. The negative ions are produced from positive ions and atoms impinging to the PG surface by...
The main purpose of the Divertor Tokamak Test facility (DTT) is to study alternative solutions to mitigate the issue of power exhaust under integrated physics and technical conditions relevant for ITER and DEMO [1]. The proposed system features a Neutral Beam Injector (NBI) heating system, providing deuterium neutrals ($D^0$) with an energy of 510 $keV$ and an injected power of 10 $MW$ to the...
As a beam diagnostic tool with the highest resolution, the 1D-CFC (one-dimensional carbon fiber composite) calorimeter can obtain the key beam parameters such as beam divergence, beam uniformity. According to the design of accelerating system of ion source for CRAFT NNBI (Comprehensive Research Facility for Fusion Technology Negative Ion based Neural Beam Injection system), the CFC calorimeter...
The electrical insulation of the Negative Ion Beam Source at 1 MV is one of the challenging issues of MITICA, the prototype of the Heating Neutral Beam Injector for ITER. A collaborative effort between QST and Consorzio RFX is presently under way for assessing and optimizing this insulation [1]. According to extrapolation models based on recent reduced-scale experiments, the voltage holding...
SPIDER is the 100 keV full-size Negative Ion Source prototype of the ITER Neutral Beam Injectors and it is operating at Consorzio RFX in Padova, Italy. It represents the most powerful Negative Ion Source in the world. SPIDER works with RF plasma from which Deuterium and/or Hydrogen ions are produced and extracted.
At the end of 2021, a scheduled long-term shutdown started to perform major...
Negative ion beams are of interest to a wide range of applications. Many previous studies investigated properties of H- or D- with beam diameters on the centimeter scale or larger due to their relevant applications in fusion or accelerators. However, less work has been done with other ion species and beam sizes in the millimeter range or smaller. Such beam properties are particularly important...
The compact radiofrequency negative ion source NIO1 (Negative Ion Optimization phase 1) has many available CF40 ports for side views of beamlet matrix. Two kinds of deflecting magnetic systems are present, namely the fringe field of the source filter Bs (mostly directed in vertical direction, x, where z is beam extraction direction) and the electron deflection filter Bd (due to magnets...
The electron density close to the extraction grids and the co-extracted electrons represent a crucial issue when operating negative ion sources for fusion. An excessive electron density in the plasma expansion region can indeed inhibit the negative ion production and introduce potentially harmful electrons in the accelerator. When entering the accelerator, electrons risk overheating the...
The H- multiaperture ion sources requested by NBI for fusion researches need fair plasma uniformity on those apertures placed on in the so called Plasma Grid, both to facilitate perveance matching of all beamlet and to balance erosion of caesium layer in long pulses. The flow of particle drifts due to both the magnetic filter (Bf), needed in the extraction region to reduce electron density...
This work documents the initial 3D calculations to simulate the coupling between RF waves and plasma in the plasma sources of the SPIDER device. Axisymmetric 3D calculations in the plasma domain alone compare well against equivalent 2D cases, yielding the expected axi-symmetry with coincident fields and Joule power coupled to the plasma. A model of SPIDER driver, the cylindrical chamber where...
In order to extract intense ion beams with good beam optics from hydrogen negative ion sources, it is important to control the shape of the plasma meniscus (i.e. beam emission surface). In our previous study [1], it is shown that the plasma meniscus in the negative ion source depends on the H- -electron density ratio as well as the bulk plasma density. Recently, it is pointed out...
Consorzio RFX and INFN-LNL have designed, built and operated the compact radiofrequency negative ion source NIO1 (Negative Ion Optimization phase 1) with the aim of studying the production and acceleration of H- ions. In particular, NIO1 was designed to keep plasma generation and beam extraction continuously active for several hours. Since 2020 the production of negative ions at the plasma...
Negative Helium ion beams are required for tandem accelerators used at research centers and at implanter facilities. The common production method of such He⁻ beams involve the interaction of a positive Helium ion beam with a low pressure alkali metal vapour. This results in a small portion of He⁺ undergoing two charge exchanges to create the desired He⁻, on the order of a few [ref]. However,...
ITER reference design, inductively coupled single driver RF-source ROBIN is operational at
IPR, Gandhinagar. The first phase of the operation yielded H- ion current density of 22-25
mA/cm2 and with electron to-ion ratios >1. The Cesium (Cs) consumption was very high
compared to a similar source operated at IPP, Garching. The lessons learned from the
operational experience showed the...
The SPIDER test facility is the full-size ITER neutral beam injector (NBI) ion source, required to provide 355 $\mathrm{A/m^2}$ extracted negative ion current density in hydrogen (285 $\mathrm{A/m^2}$ in deuterium) with an electron-to-ion ratio lower than 0.5 (1 in deuterium). The negative ion source is integrated with a system of three grids, which allows the extraction and acceleration of...
In Korea, as part of the ITER non-procurement core technology development project, the development of a negative ion beam source is in progress.
The overall period can be divided into 3 phases corresponding to 3 prototype negative ion beam sources. In the first phase, a Cs-free ion source using 2 MHz RF up to 10 kW was developed. A 4 mm thick water-cooled Faraday shield was inserted inside an...
The China spallation neutron source project Phase-II (CSNS-II) aims to deliver proton beam of 500 kW on the target. To accomplish this goal, an RF-driven negative hydrogen ion source was developed to replace the penning ion source used in CSNS-I. The RF-driven ion source has been put into commissioning on CSNS accelerator since Sept. 8th of 2021. And it was shut down on July 26th of 2022,...
We have developed a semi-empirical model predicting the equilibrium caesium coverage (in monolayers) and the resulting work function of the ISIS Penning ion source cathode (in eV) in long pulse operation. We use the caesium balance model to predict the temporal structure of the extracted H$^-$ beam current pulses and compare the model predictions to experimental data with 60 mA, 2 ms beam...
Cesium additives are currently used in negative hydrogen(H-/D-) ion sources, which are key components in nuclear fusion plasma heating systems and high energy proton accelerators. Here, a thin cesium layer on a Molybdenum plasma electrode (or plasma grid), PE, lowers the surface work function, and results in high H-/D- production rates. However, in future systems, alternative ion source...
Caesium-covered molybdenum surfaces are considered for negative ion production [1] [2]. Surface chemical-physics can help to understand the surface process influencing and determining device performances.
Molecular Dynamics simulations based on ab initio calculations in the framework of DFT( Density Functional Theory) have been used to simulate the interactions occurring at the gas-surface...
A roto-vibrational specific corona model is discussed for the simulation of the Fulcher spectrum in low pressure Hydrogen discharges. The model takes into account the processes of electron-impact excitation, spontaneous emission and predissociation and allows to simulate the molecular Fulcher spectrum in the [600:640] nm range.
The model is applied to the analysis of emission spectra...
The CERN ALPHA experiment makes precision measurements of antihydrogen atoms held in a superconducting magnetic minimum trap. Recent studies of the antihydrogen spectrum have provided unique tests of fundamental physics, and to improve on these studies ALPHA is now proposing upgrades to directly compare hydrogen and antihydrogen within their existing atom trap. One route towards producing...
H- charge exchange (stripping) injection into the European Spallation Neutron Source (ESS) Storage Ring requires a 90 mA H- ion source that delivers 2.9 ms pulses at 14 Hz repetition rate (duty factor ~4%) that can be extended to 28 Hz (df 8%). This can be achieved with a magnetron surface plasma H- source (SPS) with active cathode and anode cooling. The Brookhaven National Laboratory (BNL)...
In fusion devices such as ITER, negative ion based neutral beam injection (NNBI) system is used for plasma heating. Cs-seeded RF driven negative ion source is typical for high-density negative ion production with surface production. However, Cs vapor seeding derived frequent maintenance and it makes long-term operation difficult. Therefore, it is necessary to develop the Cs-free negative ion...
MITICA, the full-size ITER heating neutral beam (HNB) injector prototype, is under construction in the ITER Neutral Beam Test Facility (NBTF) at Consorzio RFX. MITICA is based on an RF negative ion source, producing a 40A deuterium beam accelerated to 1 MeV; the beam is then gas neutralized with 60% efficiency, the residual ions are electrostatically removed, and it is finally dumped on a...
A prototype radio frequency (RF) negative hydrogen ion beam source is developed in Korea Institute of Fusion Energy (KFE). The target is to extract negative ion beam with 200 keV, 0.5 A for 100 ms. The RF power supply of 400 kHz delivers over 40 kW to the ICP without the Faraday shield. The plasma is generated and turned off within 120 us, and the RF power supply is stabilized within tens of...
When we speak about Additive Manufacturing (AM), we think of a rather new manufacturing approach that allows to create objects layer-by-layer and without limits of shape. AM covers a wide range of techniques, that differ from each other by the class of material used for the process, the appearance of the raw material (powder, wire, sheet, etc.) and the way it is added and joined to the...
DEMO-FNS facility (R = 3.2m, a = 1m, k = 2, B = 5T) will be a hybrid reactor designed to combine fusion and fission technologies. In a hybrid reactor the power is mainly produced by a fission blanket which is exposed to the neutron flux coming from confined plasma, or a fusion neutron source (FNS). Plasma parameters required for FNS steady-state operation are essentially lower as compared...
SPIDER is a full-scale prototype of ITER HNBI radio frequency (RF) negative ion-source equipped with a 100 keV particle accelerator system. It has 4 RF circuits, each composed of an RF generator operating at a frequency of 1 MHz, rated power of 200 kW on 50 Ω load whose RF load is composed of a transmission line feeding a capacitor-based impedance matching network connected to two driver coils...
SPIDER is the prototype source for ITER negative ion beams in operation at Padova PRIMA test facility since 2018. SPIDER mission is to produce an extracted negative ion beam of section 1.5x0.6 m2 and a current density of 355 A/m2 (H-) or 285 A/m2 (D-) while keeping the fraction of co-extracted electrons below 0.5 (H)/1 (D). During the experimental campaigns in SPIDER, the operating conditions...
Neutral Beam Injectors (NBIs) based on negative ions will be the workhorses of the ITER experiment, where they are expected to provide up to 33MW of power to heat the fusion plasma. The negative hydrogen ions are extracted from a RF plasma, in which a magnetic filter field cools down the electrons reaching the so-called expansion region allowing the formation of negative ions near the...
As one of effective means for plasma heating and current driving, neutral beam injector have been installed in most of nuclear fusion experimental devices in the world. High power neutral beam long pulses are required for continuous heating was required according to the development and research of magnetic controlled fusion energy. Large area high current ion source is the key equipment of...
The negative ion formation in the caesium sputter ion sources occurs on the surface of a cathode containing the ionized material. The cathode is covered by a thin layer of caesium (Cs), which lowers the work function of the surface enhancing the negative ion formation. Vogel [1] recently introduced a hypothesis that the negative ion current can be enhanced by exposing the cathode to a laser...
It is essential to generate the negative ion beams with good beam optics for the negative ion sources. Negative ion beam optics is determined by the shape of the plasma meniscus, which is an ion emitting surface. However, for the electronegative plasma including the surface produced H- ions in the negative ion sources, the key parameters to control the plasma meniscus and the dependence on...
Dynamic responses of negative ion meniscus to externally applied RF field with 2% arc discharge power were investigated experimentally. Three types of responses were identified. First is the beamlet width oscillation with the same frequency as the applied RF field. The second is the oscillation of the beamlet axis. The third is the response of the time-averaged beamlet width. These responses...
The BATMAN Upgrade (BUG) test facility at IPP is contributing to the development of RF-driven H$^–$ sources towards the ITER neutral beam injection and beyond. BUG is equipped with an 1/8 size of the ITER NBI ion source and thus is highly flexible for setup changes or diagnostic access. The extraction and acceleration system consists of three grids (plasma grid PG, extraction grid EG and...
The Neutral Ion Beam Injection will be used to further heat the plasma temperature to reach the ignition of the fusion reaction to producing energy in ITER project and some energy efficiency is required. Recently a very simple beam energy recovery based on space charge effect has been proposed as an alternative to the Electrostatic Ion Dump since had some advantages in removing the residual...
Hydrogen plasma with its multiple constituent species (H, H2 at ground and excited vibrational levels, H+, H2+, H3+, H-) offers a rich array of applications in diverse fields of science and technology such as in materials processing, production of ion beams for fusion plasma heating etc. In the present work, a combination of a solenoid and a set of five permanent ring magnets were used to...
The negative ion formation in the cesium sputter ion sources occurs on the surface of a cathode containing the ionized material. The cathode is covered by a thin layer of cesium (Cs), which lowers the work function of the surface enhancing the negative ion formation. Vogel [1] recently introduced a hypothesis that the negative ion current can be enhanced by exposing the cathode to a laser beam...
The ITER NBI requires H-/D-beamlets with a low divergence, in view of the beamline transmission. Ion extraction and beamlet formation are typically studied with gun-type codes such as IBSimu, which do not treat the plasma explicitly. The beamlet particles are tracked through the full grid system; the compensating charge density in the plasma region is given by an analytical function. As a...
