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Watch humans and robots inside the JET mockup at the Culham Centre for Fusion Energy (CCFE) in the UK.

Video via Tom Scott/CCFE

Researchers at the US Department of Energy's (DOE) Princeton Plasma Physics Laboratory (PPPL) have challenged the understanding of a key element in fusion plasmas. At issue has been an accurate prediction of the size of the "bootstrap current"—a self-generating electric current—and an understanding of what carries the current at the edge of plasmas in doughnut-shaped facilities called tokamaks. This bootstrap-generated current combines with the current in the core of the plasma to produce a magnetic field to hold the hot gas together during experiments, and can produce stability at the edge of the plasma.

The recent work, published in the April issue of the journal Physics of Plasmas, focuses on the region at the edge in which the temperature and density drop off sharply. In this steep gradient region—or pedestal—the bootstrap current is large, enhancing the confining magnetic field but also triggering instability in some conditions.

The bootstrap current appears in a plasma when the pressure is raised. [...] Physics understanding and accurate prediction of the size of the current at the edge of the plasma is essential for predicting its effect on instabilities that can diminish the performance of fusion reactors.

--Illustration: Simulation shows trapped electrons at left and passing electron at right that are carried in the bootstrap current of a tokamak. Credit: Kwan Liu-Ma, University of California, Davis.

Read the full article on the PPPL .

Another shipment of in-kind components from India has arrived at the PRIMA neutral beam test facility in Padua, Italy. At PRIMA, ITER's most powerful heating system—neutral beam injection—will be tested in advance of operation. 

The SPIDER test bed is a 1:1-scale ion source that will be used to develop the technology for the production of negative ions. India already delivered the beam dump in late 2014; this time, 13 trucks carried the components of the 100 kV power supply.

Read more about the lastest shipment here.

In its May 2016 issue, Nature Physics has produced an Insight on Nuclear Fusion that features an interview with ITER Director-General Bernard Bigot, a commentary by Steven Cowley (current Chief Executive Officer of the UK Atomic Energy Agency and Head of the EURATOM/CCFE Fusion Association), and a review of the fascinating physics that lies at the heart of nuclear fusion.

A full list of content is available at this . (Content may be accessed through a subscription to Nature Physics or rental/purchase.)