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...
In negative hydrogen ion sources, the kinetic energy of the atoms is directly related to the negative ion yield at the caesiated converter, with a larger contribution from hot atoms. The H0 energy distribution is related to the formation process: either the kinetic energy release resulting from dissociation of the hydrogen molecules or molecular ions, or the proton neutralization during...
The cesium (Cs)-free negative-ion neutral-beam injection (NNBI) system is technical issue on the development of magnetic fusion reactors. The progress toward realizing a high-performance Cs-free negative-ion source based on volume production in a magnetized sheet plasma device (TPDsheet-U) is reported [1,2]. The volume production of negative hydrogen ions in the produced magnetized sheet...
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...
Abstract: In particle-in-cell (PIC)simulation, different particle injection method is used to maintain the plasma source term. Common particle injection methods include a) constant flux injection in which a fixed number of ion-electron pairs are injected each time step and b) pair re-injection in which the number of ion-electron pairs injected is according to the number of positive ions...
A fast electrostatic chopper is installed in the low-energy beam transport (LEBT) of China Spallation Neutron Source (CSNS) accelerator. It is used to chop the beam into pulses before RFQ accelerator. The chopped beam pulses synchronize with the period of Rapid Cycling synchrotron (RCS). But the electric field induced by this chopper will destroy the space charge compensation (SCC) in LEBT,...
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 (Source for the Production of Ions of Deuterium Extracted from a Radio frequency plasma), hosted at the Neutral Beam Test Facility (NBTF) in Padova, Italy, is the full scale prototype for the ITER Heating Neutral Beam (HNB) source.
A collisional radiative model for caesium-hydrogen plasmas was recently developed. When used in conjunction with measurements from Optical Emission...
NIO1 (Negative Ion Optimization phase 1) is a compact multi-aperture radiofrequency H$^-$ ion source whose design was optimized for sustainable prolonged beam on target (BOT) operation; installation economy implied a drastic scaling as respect to fusion device D$^-$ sources. The latter in a consistent view for energy production request a beam on tokamak (BOT) span of 20 years, that is 6 10$^8$...
The work function of a surface can be determined by measuring the nA-photocurrents arising from the irradiation by light of different wavelengths. When the chosen photon energies are close to the work function, this energy threshold can be calculated using the Fowler method. As a novelty using fiber coupled LEDs as a light source of sufficient power, the work function inside a negative ion...
The caesiated surface negative ion (H) source is the first element of CERN’s LINAC4 a linear injector designed to accelerate negative hydrogen ions to 160MeV. The IS03 ion source, used during Run 3, is operated at 35 mA beam intensity, H⁻ ions are generated via plasma volume and caesiated molybdenum (Cs-Mo) plasma electrode surface mechanisms. The 3D PIC-Monte Carlo ONIX (Orsay Negative Ion...
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...
The large size and complexity of ITER negative ion source prototype play a key role in determining the homogeneity of the multi-beamlet negative ion beam current and divergence.
Visible tomography, which has already proved capable of characterizing the isolated beamlet properties with high temporal and spatial resolutions, can be exploited to study the beam dependence on source parameters...
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...
Cusp-shaped magnetic fields are widely used to confine plasmas in various applications. This kind of field topology is obtained by placing a set of permanent magnets with alternate orientation and regular step on the plasma chamber surfaces.
Within this magnetic field configuration, plasma loss is localised in correspondence of the permanent magnets, where the field lines are perpendicular to...
