Comparing diamagnetic flux measurements and modelling on ASDEX Upgrade

The diamagnetic flux is the small difference in toroidal flux with plasma and without plasma. This measurement contains valuable information about the fast-ion confinement since energetic particles can significantly contribute to the plasma pressure and modify the diamagnetic flux. The diamagnetic flux diagnostic at ASDEX Upgrade [1] can therefore be used to investigate fast-ion transport in advanced scenario and resonant magnetic perturbation (RMPs) discharges

Note: Internal diamagnetic flux measurements on ASDEX Upgrade

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 Conundrum of Order: The Concept of Governance from an Interdisciplinary Perspective

The term governance has made an impressive career in a number of disciplines concerned with regulation, order and law. This chapter draws on insights from legal studies, sociology, political science, anthropology, history and geography to paint a multifaceted picture of existing, competing and complementing approaches to the concept of governance. For reasons of space, the chapter can but point to the different variations on a theme, as governance occupies an ambivalent place in past and present discourses on political (or, legal or economic) order and society. It is argued that beyond pointing to crucial phases of methodological and theoretical transformation within different disciplines such as the often perceived transition ‘from government to governance’, governance is itself a deeply interdisciplinary concept

Modern Slavery, Unfree Labour and the Labour Market: The Social Dynamics of Legal Characterization

Treating the United Kingdom’s Modern Slavery Act as its focus, this article examines what the legal characterization of labour unfreedom reveals about the underlying conception of the labour market that informs contemporary approaches to labour law in the United Kingdom. It discusses how unfree labour is conceptualized within two key literatures – Marxist-inspired political economy and liberal approaches to modern slavery – and their underlying assumptions of the labour market and how it operates. As an alternative to these depictions of the labour market, it proposes a legal institutionalist or constitutive account. It develops an approach to legal characterization and jurisdiction that is attentive to modes of governing and the role of political and legal differentiation both in producing labour exploitation and unfree labour and in developing strategies for its elimination. It argues that the problem with the modern slavery approach to unfree labour is that it tends to displace labour law as the principal remedy to the problem of labour abuse and exploitation, while simultaneously reinforcing the idea that flexible labour markets of the type that prevails in the United Kingdom are realms of labour freedom

The CMS Phase-1 pixel detector upgrade

The CMS detector at the CERN LHC features a silicon pixel detector as its innermost subdetector. The original CMS pixel detector has been replaced with an upgraded pixel system (CMS Phase-1 pixel detector) in the extended year-end technical stop of the LHC in 2016/2017. The upgraded CMS pixel detector is designed to cope with the higher instantaneous luminosities that have been achieved by the LHC after the upgrades to the accelerator during the first long shutdown in 2013–2014. Compared to the original pixel detector, the upgraded detector has a better tracking performance and lower mass with four barrel layers and three endcap disks on each side to provide hit coverage up to an absolute value of pseudorapidity of 2.5. This paper describes the design and construction of the CMS Phase-1 pixel detector as well as its performance from commissioning to early operation in collision data-taking.Peer reviewe

Progress from ASDEX Upgrade experiments in preparing the physics basis of ITER operation and DEMO scenario development

An overview of recent results obtained at the tokamak ASDEX Upgrade (AUG) is given. A work flow for predictive profile modelling of AUG discharges was established which is able to reproduce experimental H-mode plasma profiles based on engineering parameters only. In the plasma center, theoretical predictions on plasma current redistribution by a dynamo effect were confirmed experimentally. For core transport, the stabilizing effect of fast ion distributions on turbulent transport is shown to be important to explain the core isotope effect and improves the description of hollow low-Z impurity profiles. The L-H power threshold of hydrogen plasmas is not affected by small helium admixtures and it increases continuously from the deuterium to the hydrogen level when the hydrogen concentration is raised from 0 to 100%. One focus of recent campaigns was the search for a fusion relevant integrated plasma scenario without large edge localised modes (ELMs). Results from six different ELM-free confinement regimes are compared with respect to reactor relevance: ELM suppression by magnetic perturbation coils could be attributed to toroidally asymmetric turbulent fluctuations in the vicinity of the separatrix. Stable improved confinement mode plasma phases with a detached inner divertor were obtained using a feedback control of the plasma β. The enhanced D α H-mode regime was extended to higher heating power by feedback controlled radiative cooling with argon. The quasi-coherent exhaust regime was developed into an integrated scenario at high heating power and energy confinement, with a detached divertor and without large ELMs. Small ELMs close to the separatrix lead to peeling-ballooning stability and quasi continuous power exhaust. Helium beam density fluctuation measurements confirm that transport close to the separatrix is important to achieve the different ELM-free regimes. Based on separatrix plasma parameters and interchange-drift-Alfvén turbulence, an analytic model was derived that reproduces the experimentally found important operational boundaries of the density limit and between L- and H-mode confinement. Feedback control for the X-point radiator (XPR) position was established as an important element for divertor detachment control. Stable and detached ELM-free phases with H-mode confinement quality were obtained when the XPR was moved 10 cm above the X-point. Investigations of the plasma in the future flexible snow-flake divertor of AUG by means of first SOLPS-ITER simulations with drifts activated predict beneficial detachment properties and the activation of an additional strike point by the drifts

Langmuir probe electronics upgrade on the tokamak a configuration variable

A detailed description of the Langmuir probe electronics upgrade for TCV (Tokamak a Configuration Variable) is presented. The number of amplifiers and corresponding electronics has been increased from 48 to 120 in order to simultaneously connect all of the 114 Langmuir probes currently mounted in the TCV divertor and main-wall tiles. Another set of 108 amplifiers is ready to be installed in order to connect 80 new probes, built in the frame of the TCV divertor upgrade. Technical details of the amplifier circuitry are discussed as well as improvements over the first generation of amplifiers developed at SPC (formerly CRPP) in 1993/1994 and over the second generation developed in 2012/2013. While the new amplifiers have been operated successfully for over a year, it was found that their silicon power transistors can be damaged during some off-normal plasma events. Possible solutions are discussed. (C) 2019 Author(s)