Neutral beams for the International Thermonuclear Experimental Reactor

Abstract

Receiving higher emphasis on the neutral beam ͑NB͒ off-axis current drive, the NB system is being highlighted for the steady state operation of the International Thermonuclear Experimental Reactor ͑ITER͒. To fulfill the physics requirement of heating and current drive, the NB system delivers ϳ50 MW of D 0 beams at 1 MeV into the ITER plasmas. The NB injector was designed so as to minimize the axial length, to avoid cost impact on the building. It was estimated by nuclear analyses that the insulation gas around the beam source would cause radiation induced conductivity, which would result in a power dissipation of Ͼ100 kW in the gas itself. As a result the present design utilizes vacuum insulation around the beam source. Since the vacuum pressure inside/outside the beam source ranges 10 Ϫ1 -10 Ϫ2 Pa, both gas ͑glow͒ and vacuum arc discharges are taken into account in the design.

Origin of Galactic Cosmic Rays from Supernova Remnants

“…Such a layer considerably reduce CR diffusion inside the clump so that only CRs with energy above 1 TeV are able to penetrate the clump. According to the results of MHD simulation [85] this indeed can happen in the downstream region where plasma flow speed shear produces magnetic field amplification around the clump surface. However such an effect is expected to be much weaker upstream, within the shock precursor region and downstream during the initial time period ∆t ≈ 0.1t (here t is the SNR age) when magnetic field is not yet amplified considerably [85].…”

“…It was suggested, that the interpretation of the γ-ray observed emission of RX J1713.7-3946 changes dramatically, if the SNR expands in a clumpy medium [83,85,86]. This is indeed expected if the SNR progenitor is a massive star in a molecular cloud.…”

“…This is indeed expected if the SNR progenitor is a massive star in a molecular cloud. The dense clumps remain unshocked inside SNR if their density considerably (by a factor of about 10 5 ) exceeds the density (N g ∼ 10 −2 cm −3 ) of surrounding warm medium [85]. CRs accelerated at the SN shock in the diluted medium penetrate the clumps and efficiently produce there γ-ray emission.…”

“…Therefore CR energy spectrum inside the clumps and corresponding spectrum of hadronic γ-ray emission are expected to be much harder compared with the case of uniform medium. If the clumps contain the dominant fraction of the mass in the SNR hadronic γ-ray emission can explain the hard Fermi spectrum [85,86].…”

Development of beam source and bushing for ITER NB system

“…A three dimensional nuclear analysis [4] has clarified that conventional insulation gas is not applicable to avoid radiation-induced conductivity (RIC) [5,6]. And hence, the present ITER NB design adopts vacuum insulation [7,8] for the beam source (ion source and accelerator), with a high voltage (HV) bushing as a vacuum boundary between the beam source vacuum and insulation gas in power supply.…”