Abstract
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 D
0
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 Ek
i
) instead of Ek
i
as in ERID gives advantages that will be mentioned.
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 (<inline-formula> <tex-math notation="LaTeX">D^{0} </tex-math></inline-formula>) 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.
Abstract
In NIO1, a compact H
-
ion source installed at RFX operated in continuous mode, gas conditioning was needed to improve results in Cs-free regimes (up to a current density about 25 or 30 A/m
...2
). Installation of a cesium oven gave an additional increase of current, progressively limited also by a rapid overcesiation: we observed an average density about 50 A/m
2
(with a peak of 67 A/m
2
). Obtained beam optics is briefly compared with simulations and previous results in the Cs-free regime in similar conditions (as source voltage, often set below or equal 11 kV). In both regimes, central beamlet apparent density is larger, possibly because of a narrow bias plate mask, now enlarged. Further improvements for Cs-based regime include a moderate oven reservoir temperature, careful tuning and a substantial increase of beam voltage, and power handling capability.
The design of a new high-transparency device based on a Micro Channel Plate (MCP) detector was recently proposed for monitoring the flux and beam spatial profile of neutron beams. The proposed device ...consists of a very thin aluminum (Al) foil (with a
6
Li deposit) placed in the neutron beam and an MCP detector equipped with a phosphor-screen readout linked to a charge-coupled device (CCD) camera outside the neutron beam. A critical feature of this device is that it uses an electrostatic mirror to minimize the perturbation of the neutron beam (i.e., absorption and scattering). It can be used at existing neutron time-of-flight (n_TOF) facilities (in particular at the n_TOF facility at CERN) for monitoring the flux and spatial profile of neutron beams in the thermal and epithermal region. The experimental tests conducted for this study using a radioactive source to determine the behavior of the electrostatic mirror behavior will be presented and discussed in this paper.
The ion source NIO1 (Negative Ion Optimization 1) is a versatile multiaperture H− source capable of continuous regime operation, with the plasma generated by a 2 MHz/2.5 kW radiofrequency (rf) power ...supply and extraction of nine beamlets. It aims to partly reproduce the conditions of much larger ion sources, built or in construction for the neutral beam injectors of fusion devices, in a compact and modular ion source, where effects of individual source components can be rapidly verified and compared to simulation code results. Several modifications of the magnetic configuration (both inside the ion source and the embedded magnets inside the accelerator grids) were investigated. Saturation of beneficial effect of filter field at large strength (>0.01 T) leads us to use softer magnetic filters, and the advantages of a crossed deflection field are noted. The rf system takes full advantage of the generator bandwidth (0/ + 20 kHz used). The result database and the integration of major diagnostic systems with the control system are also summarized, with some details on voltage holding and beam uniformity.
Neutron capture cross section measurements of isotopes close to s-process branching-points are of fundamental importance for the understanding of this nucleosynthesis mechanism through which about ...50% of the elements heavier than iron are produced. We present in this contribution the results corresponding to the high resolution measurement, for first time ever, of the 80Se(n, γ) cross section, in which 98 resonances never measured before have been reported. As a consequence, ten times more precise values for the MACS have been obtained compared to previous accepted value adopted in the astrophysical KADoNiS data base.
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