What’s New

New computer simulations at the Princeton Plasma Physics Laboratory (PPPL) indicate that an innovate start-up technique for tokamaks, called coaxial helicity injection (CHI), may support a strong electric current without a traditional solenoid magnet.

In tokamaks, a complex web of magnetic fields control the superhot plasma. In addition to large D-shaped magnets surrounding the vacuum vessel, a central electromagnet known as a solenoid participates in creating the twisting vortex that prevents the plasma from touching the tokamak's walls.

Compact spherical tokamaks, like the NSTX-U recently dedicated at PPPL, as well as future tokamaks may not have room for solenoids. During CHI, magnetic field lines, or loops, are inserted into the tokamak's vessel through openings in the vessel floor. The field lines then expand to fill the vessel space, like a balloon inflating with air, until the loops undergo a process known as magnetic reconnection and snap closed. The newly formed closed field lines then induce current in the plasma.

"Can we create and sustain a big enough magnetic bubble in a tokamak to support a strong electric current without a solenoid?" asks Physicist Fatima Ebrahimi, who performed the computer simulations. "The findings indicate that 'yes, we can do it.'"

Read the full article on the PPPL website.

--Image: Physicist Fatima Ebrahimi

In line with a First Plasma in 2017, the 41-tonne vacuum vessel of the MAST Upgrade project was returned to its concrete-shielded home in late May, where it can now be refitted with its components and systems before commissioning.

The upgraded MAST tokamak will help to add to the knowledge base for ITER by experimenting with key plasma physics issues.

Watch a short video of the milestone on the website of the Culham Centre for Fusion Energy (UK).

Ronald C. Davidson, a pioneering plasma physicist for 50 years who directed the US Department of Energy's Princeton Plasma Physics Laboratory (PPPL) during a crucial period of its history and was a founding director of the Plasma Fusion Center at the Massachusetts Institute of Technology (MIT), passed away on 19 May at his home in Cranbury, New Jersey. He was 74.

"Ron was an anchor for the Laboratory both through his science and through his wisdom," said Stewart Prager, director of PPPL. "His prodigious contributions not just to PPPL's science but also to plasma physics writ large are clear and widely known. Within the Laboratory, he was a mentor and a guide to people young and old. His impact within the Laboratory was enormous."

The physicist won numerous honours in his lifetime, including the prestigious James Clerk Maxwell Prize in Plasma Physics in 2008, the highest national honour in plasma physics. He was a fellow of both the American Physical Society and the American Association for the Advancement of Science. Davidson was known as a prolific researcher, writer and academic.

Read the full-length obituary on the PPPL website.