PPPL and General Atomics Scientists
Make Breakthrough in Understanding
How to Control Intense Heat Bursts in
Fusion Experiments
By Raphael Rosen,Princeton Plasma Physics Laboratory
Make Breakthrough in Understanding
How to Control Intense Heat Bursts in
Fusion Experiments
By Raphael Rosen,
March 13, 2015 -- Researchers from General Atomics and the U.S.
Department of Energy’s Princeton Plasma Physics Laboratory (PPPL) have made a
major breakthrough in understanding how potentially damaging heat bursts inside
a fusion reactor can be controlled. Scientists performed the experiments on the
DIII-D National Fusion Facility, a tokamak operated by General Atomics in San Diego France
The studies build upon previous work pioneered on DIII-D showing that these
intense heat bursts – called “ELMs” for short – could be suppressed with tiny
magnetic fields. These tiny fields cause the edge of the plasma to smoothly
release heat, thereby avoiding the damaging heat bursts. But until now,
scientists did not understand how these fields worked. “Many mysteries
surrounded how the plasma distorts to suppress these heat bursts,” said Carlos
Paz-Soldan, a General Atomics scientist and lead author of the first of the two
papers that report the seminal findings back-to-back in the same issue of
Physical Review Letters this week.
Paz-Soldan and a multi-institutional team of researchers found that tiny
magnetic fields applied to the device can create two distinct kinds of
response, rather than just one response as previously thought. The new response
produces a ripple in the magnetic field near the plasma edge, allowing more heat
to leak out at just the right rate to avert the intense heat bursts.
Researchers applied the magnetic fields by running electrical current through
coils around the plasma. Pickup coils then detected the plasma response, much
as the microphone on a guitar picks up string vibrations.
The second result, led by PPPL scientist Raffi Nazikian, who heads the PPPL
research team at DIII-D, identified the changes in the plasma that lead to the
suppression of the large edge heat bursts or ELMs. The team found clear evidence
that the plasma was deforming in just the way needed to allow the heat to
slowly leak out. The measured magnetic distortions of the plasma edge indicated
that the magnetic field was gently tearing in a narrow layer, a key prediction
for how heat bursts can be prevented. “The configuration changes suddenly
when the plasma is tapped in a certain way,” Nazikian said, “and it is this
response that suppresses the ELMs.”
The work involved a multi-institutional team of researchers who for years
have been working toward an understanding of this process. These researchers
included people from General Atomics, PPPL, Oak Ridge National Laboratory, Columbia University ,
Australian National
University , the University of California-San
Diego
The new results suggest further possibilities for tuning the magnetic
fields to make ELM-control easier. These findings point the way to overcoming a
persistent barrier to sustained fusion reactions. “The identification of the
physical processes that lead to ELM suppression when applying a small 3D
magnetic field to the inherently 2D tokamak field provides new confidence that
such a technique can be optimized in eliminating ELMs in ITER and future fusion
devices,” said Mickey Wade, the DIII-D program director.
The results further highlight the value of the long-term
multi-institutional collaboration between General Atomics, PPPL and other
institutions in DIII-D research. This collaboration, said Wade, “was
instrumental in developing the best experiment possible, realizing the
significance of the results, and carrying out the analysis that led to
publication of these important findings.”
No comments:
Post a Comment