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Neutral beam injection is the main heating system on a variety of fusion devices, and will be the main heating system of ITER. Especially during high-power operation in long pulse devices, it is important that transmission losses and power deposition in the beamline are well quantified. This paper presents the analytical beamlet code (ABC)3D. ABC3D is based on analytical Gaussian beamlets, and includes shadowing effects. The code is able to calculate emission spectra in the beamline, duct transmission losses, and neutral beam power loads on 3D components. Examples of its application are shown that highlight key results in beam emission spectroscopy, beamline design, and geometry verification in experiments. Limitations to the computational approach are discussed on the basis of a comparison with more advanced calculations. [ABSTRACT FROM AUTHOR]

The appropriate tailoring of the q-profile is the key to accessing Advanced Tokamak (AT) scenarios, which are of great benefit to future all-metal fusion power plants. Such scenarios depend on low collisionality ν* which permits efficient external current drive and high amounts of intrinsic bootstrap current. At constant pressure, lowering of the electron density ne leads to a strong decrease in the collisionality with increasing electron temperature ν* ∼ T e − 3 . Simultaneously, the conditions for low ne also benefit impurity accumulation. This paper reports on how radiative collapses due to central W accumulation were overcome by improved understanding of the changes to recycling and pumping, substantially expanded ECRH capacities for both heating and current drive, and a new solid W divertor capable of withstanding the power loads at low ne. Furthermore, it reports on various improvements to the reliability of the q-profile reconstruction. A candidate steady state scenario for ITER/DEMO (q95 = 5.3, βN = 2.7, fbs > 40%) is presented. The ion temperature profiles are steeper than predicted by TGLF, but nonlinear electromagnetic gyro-kinetic analyses with GENE including fast particle effects matched the experimental heat fluxes. A fully non-inductive scenario at higher q95 = 7.1 for current drive model validation is also discussed. The results show that non-inductive operation is principally compatible with full-metal machines. [ABSTRACT FROM AUTHOR]

Internal diamagnetic flux measurements, with measurement loops and compensation magnetic probes inside the vacuum vessel, are now available on the ASDEX Upgrade tokamak. The measured diamagnetic flux is compared to that predicted by simulations and calculated from equilibrium reconstruction. The diamagnetic flux measured at 2 positions separated toroidally by 180° in the vacuum vessel is compared.

The coupling efficiency between two multimode fibers with an angular misalignment is calculated. For the practically interesting cases of parabolic and step-index profiles, closed-form expressions and simple approximations are derived. Furthermore a general loss formula for small tilt angles and arbitrary profile exponents is presented.