Plasma flows in scrape-off layer of Aditya tokamak

Abstract

The magnetized Mach probe is used to make measurement of plasma flows in the scrape-off layer of the Aditya tokamak [R. Jha et al., Plasma Phys. Controlled Fusion 51, 095010 (2009)]. This probe is further used to measure dependencies of Mach number on local plasma densities and radial distances of the probe in the scrape-off layer. The measured Mach number has contributions from E Â B drift, Pfrisch-Schl€ uter, and transport driven flows. We have determined that the toroidal flow is towards the ion side of the limiter and the poloidal flow direction is towards the contact of the last closed flux surface with the limiter. V C 2012 American Institute of Physics.

Flow structure and shear generation in the 3D SOL of a circular tokamak plasma in Aditya

“…The probe measurements however remain highly local and limited in their capacity to provide information about the global spatial variations because of limited number of probes on the device. The toroidal Mach number, for example, was observed to increase with radial distance in the SOL and decrease with increasing density [17]. An interpretation of this was provided in terms of flows that are global in nature since they originate because of the following two factors: (i) particle drift effects that are identified to develop at longer scale lengths, corresponding to that of a mean electric field (e.g, E × B and Pfirsch-Schluter flows that develop due to vertical charge separation at the minor radius) and (ii) the pressure difference driven flows that develop due to the plasma source, in the form of diffusion across the LCFS, over the SOL length, largely comparable to maximum connection length, L c .…”

“…Behavior of plasma transport, flows, drifts and their associated fluctuations are studied routinely in the edge and SOL region of tokamak Aditya by analyzing the data from Mach probes and Langmuir probes [17,18,22].…”

Scrape Off Layer Flow Characteristics in the Spherical Tokamak QUEST

“…Hence, SOL flow has been measured in many tokamaks [3,4]. Several mechanisms are cited to drive these flows like toroidal rotation, ionization imbalances, Pfirsch-Schlüter (PS) flow, cross-field drift and ballooning transport.…”

3-D simulations of plasma transport in the ring limiter scrape-off layer of tokamak Aditya

“…In the above setup interaction of the plasma with the ring limiter results in a poloidally narrow strike region, localized on the outboard side of the circular limiter. The typical measurements of plasma position using magnetic probes indicate the position of strike region on the limiter perimeter at the outboard mid-plane with a slight up or down shift, depending on the vertical plasma stability during the discharge [6]. It is interesting to note that the 3-dimensional SOL forming in this setup has two distinct regions or volumes, first with very short connection length, not exceeding 2π(R + r 0 ), where R is the major radius and r 0 is the inner radius of the ring limiter, and second with considerably longer connection lengths.…”

“…fluctuations have been identified in various experiments on the device over last two decades, for example, the circular plasma shape resulting from the above set up is expected to have sharp gradients of E × B poloidal flow giving rise to a velocity shear layer [6]. Apart from plasma.…”