Nav: Home

Graduate students install diagnostic on NSTX-U

December 21, 2015

A system of antennas similar to those that astrophysicists use to study radio emissions from stars and galaxies will help shed light on fusion experiments at the U.S. Department of Energy's Princeton Plasma Physics Laboratory (PPPL). Called Synthetic Aperture Microwave Imaging (SAMI), the system aims to provide highly precise time and spatial resolution measurements of the density of current at the edge of fusion plasmas in the National Spherical Torus Experiment-Upgrade (NSTX-U) -- the Laboratory's newly upgraded flagship facility that is set to embark on compelling new research programs.

High-resolution measurements of the edge current density are key to understanding instabilities called Edge Localized Modes (ELMs) that can foil experiments in the H-mode regime that marks high-level performance of fusion plasmas. Large ELMs can eject significant amounts of energy that can damage the vacuum vessels of tokamaks that house fusion reactions and generate impurities that can significantly degrade the reactions.

The two graduate students, David Thomas of the University of York and Jakob Brunner of Durham University brought the SAMI system, which consists of an array of eight antennas, to PPPL from Britain in November. It was originally installed on the Mega Amp Spherical Tokamak (MAST) at the United Kingdom's Culham Centre for Fusion Energy; MAST is an NSTX-U-like system that is currently shut down for a major upgrade. Now modified to meet NSTX-U requirements, the SAMI plasma diagnostic will start acquiring significant amounts of data during the 2016 NSTX-U research campaign.

Passive and active functions

The antennas have both passive and active functions. They passively map the conversion of what are called "electron Bernstein waves" inside the plasma to microwave radiation near the edge of the plasma. The image of this microwave emission is characterized by two bright regions and the steepness of the line between these two regions depends on the local plasma current density.

The diagnostic measures microwave emission in a wide range of frequencies that correspond to different locations in the edge of the plasma. SAMI can therefore be used to map the profile of current density with much higher resolution than is possible with other plasma diagnostics on NSTX-U.

SAMI also uses two antennas in the array to actively probe turbulence in the plasma by launching radar-like waves that bounce off the turbulence that takes the form of filaments called "blobs." On MAST, the system imaged the velocity and size of these blobs to produce the first two-dimensional map of the velocity of the turbulence itself -- a critical factor that allows heat to leak from fusion experiments.

Thomas and Brunner, who were at the Lab in November, worked with engineer Bob Ellis, physicist Gary Taylor and technicians to install the system and gave talks on it to NSTX-U staffers. They will return early next year to complete the installation and hook up the turbulence-probing mechanisms.
-end-
The work was supported by the DOE Office of Science.

PPPL, on Princeton University's Forrestal Campus in Plainsboro, N.J., is devoted to creating new knowledge about the physics of plasmas -- ultra-hot, charged gases -- and to developing practical solutions for the creation of fusion energy. Results of PPPL research have ranged from a portable nuclear materials detector for anti-terrorist use to universally employed computer codes for analyzing and predicting the outcome of fusion experiments. The Laboratory is managed by the University for the U.S. Department of Energy's Office of Science, which is the largest single supporter of basic research in the physical sciences in the United States, and is working to address some of the most pressing challenges of our time. For more information, please visit science.energy.gov.

DOE/Princeton Plasma Physics Laboratory

Related Plasma Articles:

Table top plasma gets wind of solar turbulence
Scientists from India and Portugal recreate solar turbulence on a table top using a high intensity ultrashort laser pulse to excite a hot, dense plasma and followed the evolution of the giant magnetic field generated by the plasma dynamics.
Getting the biggest bang out of plasma jets
Capillary discharge plasma jets are created by a large current that passes through a low-density gas in what is called a capillary chamber.
Neptune: Neutralizer-free plasma propulsion
Plasma propulsion concepts are gridded-ion thrusters that accelerate and emit more positively charged particles than negatively charged ones.
UCLA researchers discover a new cause of high plasma triglycerides
People with hypertriglyceridemia often are told to change their diet and lose weight.
Where does laser energy go after being fired into plasma?
An outstanding conundrum on what happens to the laser energy after beams are fired into plasma has been solved in newly-published research at the University of Strathclyde.
New feedback system could allow greater control over fusion plasma
A physicist has created a new system that will let scientists control the energy and rotation of plasma in real time in a doughnut-shaped machine known as a tokamak.
PPPL scientist uncovers physics behind plasma-etching process
PPPL physicist Igor Kaganovich and collaborators have uncovered some of the physics that make possible the etching of silicon computer chips, which power cell phones, computers, and a huge range of electronic devices.
Calculating 1 billion plasma particles in a supercomputer
At the National Institutes of Natural Sciences National Institute for Fusion Science (NIFS) a research group using the NIFS 'Plasma Simulator' supercomputer succeeded for the first time in the world in calculating the movements of one billion plasma particles and the electrical field constructed by those particles.
Anti-tumor effect of novel plasma medicine caused by lactate
Nagoya University researchers developed a new physical plasma-activated salt solution for use as chemotherapy.
Clarifying the plasma oscillation by high-energy particles
The National Institute for Fusion Science has developed a new code that can simulate the movement of plasma and, simultaneously, the movement of particles circulating at high speeds.

Related Plasma Reading:

Best Science Podcasts 2019

We have hand picked the best science podcasts for 2019. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Anthropomorphic
Do animals grieve? Do they have language or consciousness? For a long time, scientists resisted the urge to look for human qualities in animals. This hour, TED speakers explore how that is changing. Guests include biological anthropologist Barbara King, dolphin researcher Denise Herzing, primatologist Frans de Waal, and ecologist Carl Safina.
Now Playing: Science for the People

#SB2 2019 Science Birthday Minisode: Mary Golda Ross
Our second annual Science Birthday is here, and this year we celebrate the wonderful Mary Golda Ross, born 9 August 1908. She died in 2008 at age 99, but left a lasting mark on the science of rocketry and space exploration as an early woman in engineering, and one of the first Native Americans in engineering. Join Rachelle and Bethany for this very special birthday minisode celebrating Mary and her achievements. Thanks to our Patreons who make this show possible! Read more about Mary G. Ross: Interview with Mary Ross on Lash Publications International, by Laurel Sheppard Meet Mary Golda...