Subscribe free to our newsletters via your
. 24/7 Space News .

Subscribe free to our newsletters via your

Scientists simulate starting up tokamaks without using solenoid
by Staff Writers
Princeton NJ (SPX) Jan 07, 2016

This is PPPL scientist Francesca Poli. Image courtesy Elle Starkman/PPPL Office of Communications. For a larger version of this image please go here.

Scientists at the U.S. Department of Energy's Princeton Plasma Physics Laboratory (PPPL) have produced self-consistent computer simulations that capture the evolution of an electric current inside fusion plasma without using a central electromagnet, or solenoid. The simulations of the process, known as non-inductive current ramp-up, were performed using TRANSP, the gold-standard code developed at PPPL. The results were published in October 2015 in Nuclear Fusion. The research was supported by the DOE Office of Science.

In traditional donut-shaped tokamaks, a large solenoid runs down the center of the reactor. By varying the electrical current in the solenoid scientists induce a current in the plasma. This current starts up the plasma and creates a second magnetic field that completes the forces that hold the hot, charged gas together.

But spherical tokamaks, a compact variety of fusion reactor that produces high plasma pressure with relatively low magnetic fields, have little room for solenoids. Spherical tokamaks look like cored apples and have a smaller central hole for the solenoid than conventional tokamaks do. Physicists, therefore, have been trying to find alternative methods for producing the current that starts the plasma and completes the magnetic field in spherical tokamaks.

One such method is known as coaxial helicity injection (CHI). During CHI, researchers switch on an electric coil that runs beneath the tokamak. Above this coil is a gap that opens into the tokamak's vacuum vessel and circles the tokamak's floor. The switched-on electrical current produces a magnetic field that connects metal plates on either side of the gap.

Researchers next puff gas through the gap and discharge a spark across the two plates. This process causes magnetic reconnection - the process by which the magnetic fields snap apart and reconnect. This reconnection creates a magnetic bubble that fills the tokamak and produces the vital electric current that starts up the plasma and completes the magnetic field.

This current must be nurtured and fed. According to lead author Francesca Poli, the new computer simulations show that the current can best be sustained by injecting high-harmonic radio-frequency waves (HHFWs) and neutral beams into the plasma.

HHFW's are radio-frequency waves that can heat both electrons and ions. The neutral beams, which consist of streams of hydrogen atoms, become charged when they enter the plasma and interact with the ions. The combination of the HHFWs and neutral beams increases the current from 300 kiloamps to 1 mega amp.

But neither HHFWs nor neutral beams can be used at the start of the process, when the plasma is relatively cool and not very dense. Poli found that HHFWs would be more effective if the plasma were first heated by electron cyclotron waves, which transfer energy to the electrons that circle the magnetic field lines.

"With no electron cyclotron waves you would have to pump in four megawatts of HHFW power to create 400 kiloamps of current," she said. "With these waves you can get the same amount of current by pumping in only one megawatt of power.

"All of this is important because it's hard to control the plasma at the start-up," she added. "So the faster you can control the plasma, the better."


Related Links
Princeton Plasma Physics Laboratory
Powering The World in the 21st Century at

Comment on this article via your Facebook, Yahoo, AOL, Hotmail login.

Share this article via these popular social media networks DiggDigg RedditReddit GoogleGoogle

Previous Report
German physicists see landmark in nuclear fusion quest
Berlin (AFP) Dec 10, 2015
Scientists in Germany said Thursday they had reached a milestone in a quest to derive energy from nuclear fusion, billed as a potentially limitless, safe and cheap source. Nuclear fusion entails fusing atoms together to generate energy - a process similar to that in the Sun - as opposed to nuclear fission, where atoms are split, which entails worries over safety and long-term waste. Af ... read more

South Korea to launch lunar exploration in 2016, land by 2020

Death rumors of Russian lunar program 'greatly exaggerated' - Deputy PM

Russia Postpones Plans on Extensive Moon Exploration Until 2025

Rare full moon on Christmas Day

Boulders on a Martian Landslide

NASA suspends March launch of InSight mission to Mars

University researchers test prototype spacesuits at Kennedy

Marshall: Advancing the technology for NASA's Journey to Mars

Gadgets get smarter, friendlier at CES show

Congress to NASA: Hurry up on that 'habitation augmentation module'

NASA Reaches New Heights

Astronauts Tour Future White Room, Crew Access Tower

China launches HD earth observation satellite

Chinese rover analyzes moon rocks: First new 'ground truth' in 40 years

Agreement with Chinese Space Tech Lab Will Advance Exploration Goals

China launches new communication satellite

NASA Delivers New Video Experience On ISS

British astronaut dials wrong number on Xmas call from space

Space Station Receives New Space Tool to Help Locate Ammonia Leaks

Two whacks is all it takes for spacewalk repair

Russian Proton-M Carrier Rocket With Express-AMU1 Satellite Launched

45th Space Wing launches ORBCOMM; historically lands first stage booster

SpaceX rocket landing opens 'new door' to space travel

NASA orders second Boeing Crew Mission to ISS

Nearby star hosts closest alien planet in the 'habitable zone'

ALMA reveals planetary construction sites

Monster planet is 'dancing with the stars'

Exoplanets Water Mystery Solved

Chameleons deliver powerful tongue-lashing

Transition metal catalyst prompts 'conjunctive' cross-coupling reaction

Coulomb blockade in organic conductors found, a world first

Adjustable adhesion power

Memory Foam Mattress Review
Newsletters :: SpaceDaily :: SpaceWar :: TerraDaily :: Energy Daily
XML Feeds :: Space News :: Earth News :: War News :: Solar Energy News

The content herein, unless otherwise known to be public domain, are Copyright 1995-2016 - Space Media Network. All websites are published in Australia and are solely subject to Australian law and governed by Fair Use principals for news reporting and research purposes. AFP, UPI and IANS news wire stories are copyright Agence France-Presse, United Press International and Indo-Asia News Service. ESA news reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. Advertising does not imply endorsement, agreement or approval of any opinions, statements or information provided by Space Media Network on any Web page published or hosted by Space Media Network. Privacy Statement All images and articles appearing on Space Media Network have been edited or digitally altered in some way. Any requests to remove copyright material will be acted upon in a timely and appropriate manner. Any attempt to extort money from Space Media Network will be ignored and reported to Australian Law Enforcement Agencies as a potential case of financial fraud involving the use of a telephonic carriage device or postal service.