Collaborations

ITER under construction in Cadarache, France

Mission completed: PPPL delivers its final shipment of steady state electrical network equipment to ITER

PPPL has completed delivery of $34-million of steady state electrical network (SSEN) components that will provide 120 megawatts of power — enough to light up a small city — for the lights, computers, heating, ventilation and air conditioning at the ITER international fusion facility under construction in Cadarache, France. The laboratory headed the five-year project on behalf of US ITER to provide 75 percent of the components for the SSEN. The European Union is providing the remaining 25 percent.

“I think it’s a great accomplishment to finish this,” said Hutch Neilson, head of ITER Fabrication. “The successful completion of the SSEN program is a very important accomplishment both for the US ITER project and for PPPL as a partner in the project.”

PPPL ordered the components, consisting of 16 groups of electrical items ranging in size up to four 87-ton transformers, from companies around the world. Shipments began in 2014 and final delivery came last October when six trucks brought 117 tons of emergency power supply equipment to an ITER storage facility.

The project was a complex enterprise. PPPL studied potential suppliers, solicited and accepted bids, and oversaw the production and testing of all components. The effort involved PPPL engineers and members of the procurement and quality assurance staff who worked to make sure that the components met ITER specifications.

A separate electrical system for the pulsed power electrical network (PPEN), procured by China, will power the ITER tokamak.

PPPL is also responsible for seven diagnostic systems and for integrating the instruments inside ITER port structures. Work in this area is currently focused on the design of equipment that will be installed prior to first plasma.

PPPL designs and delivers diagnostic for world’s most powerful laser facility

PPPL has built and delivered a high-resolution X-ray spectrometer for the largest and most powerful laser facility in the world. The diagnostic, installed on the National Ignition Facility (NIF) at Lawrence Livermore National Laboratory, will analyze and record data from high-energy density experiments created by firing NIF’s 192 lasers at tiny pellets of fuel. Such experiments are relevant to projects that include the U.S. Stockpile Stewardship Program, which maintains the U.S. nuclear deterrent without full-scale testing, and to inertial confinement fusion, an alternative to the magnetic confinement fusion that PPPL studies.

PPPL has developed and used spectrometers for decades to analyze the electromagnetic spectrum of plasma, the hot fourth state of matter in which electrons have separated from atomic nuclei, inside doughnut-shaped fusion devices known as tokamaks. The instruments, which are used in magnetic confinement fusion experiments around the world, heat the particles and contain them in magnetic fields, causing the nuclei to fuse and produce fusion energy. By contrast, NIF’s high-powered lasers cause fusion by heating the exterior of the fuel pellet. As the exterior vaporizes, pressure extends inward towards the pellet’s core, crushing hydrogen atoms together until they fuse and release their energy.

In a test of the spectrometer on NIF, the device accurately measured the electron temperature and density of a fuel capsule during the fusion process. “Measuring these conditions is key to achieving ignition of a self-sustaining fusion process on NIF,” said PPPL physicist Lan Gao, who helped design and build the device. “Everything worked out very nicely. The signal level we got was just like what we predicted.”

Other PPPL researchers who contributed to this project include Ken Hill, a principal research physicist; Phil Efthimion, head of the Plasma Science & Technology Department; and graduate student Brian Kraus.

Physicist Lan Gao performs final check before spectrometer is shipped to NIF

Interior of the superconducting EAST tokamak

Physicist Rajesh Maingi

PPPL heads project on EAST that could lead to optimization of long-pulse plasmas

PPPL is principal investigator for a multi-institutional project to study plasma-material interaction on the Experimental Advanced Superconducting Tokamak (EAST) in China. The three-year project, which began in 2016, is designed to test the ability of lithium to protect the EAST walls and prevent impurities from bouncing back into the core of the plasma and halting fusion reactions. Such results could lead to optimization of long-pulse plasma discharges.

The project has shown excellent progress in all of these areas by deploying lithium through three different devices. These include lithium powder injectors, lithium powder and granule injectors, and a second-generation flowing liquid limiter (FLiLi). The positive results included:

The lithium powder injector eliminated Edge Localized Modes (ELMs), periodic instabilities that could damage the divertor that exhausts waste heat and particles from the tokamak.
The lithium granule injector showed that a threshold exists for the minimum size of the granules that are large enough to trigger ELMs — an alternative procedure that causes the instabilities to be smaller, more frequent and less detrimental to plasma-facing components.
The FLiLi device sharply reduced the amount of deuterium at the edge of the plasma that recycled back into the core of the plasma and cooled it off during high-confinement experiments.

“We’re trying to make a cohesive program so the things that we’ve learned in this country can be tried over there,” said physicist Rajesh Maingi, who leads the PPPL effort. "Then we can bring back what we learn there to help us at both the National Spherical Torus Experiment Upgrade (NSTX-U) at PPPL and the DIII-D National Fusion Facility that General Atomics operates for the U.S. Department of Energy in San Diego."

Collaborating with PPPL on the overall project are the Los Alamos and Oak Ridge national laboratories, along with Johns Hopkins University, the Massachusetts Institute of Technology, the University of Illinois at Urbana-Champaign and the University of Tennessee.

Reaching new heights: Physicists improve the vertical stability of KSTAR

Maintaining the ultra-hot plasma that fuels fusion reactions in a steady state, or sustainable, manner, represents a key challenge facing the development of fusion energy. Superconducting magnetic coils, which avoid the tremendous power requirement of copper coils, can be used to accomplish this feat. However, engineering constraints limit how quickly superconducting coils can adjust when compared with copper coils, posing a problem for fast control of plasma instabilities.

At the Korea Superconducting Tokamak Advanced Research (KSTAR) device, one of the world’s largest superconducting tokamaks, a team of U.S. and Korean researchers led by physicist Dennis Mueller of PPPL has developed a method for improving the vertical stability of the elongated plasma. The achievement sets an example for how to address similar steady state issues in future superconducting devices such as ITER, the international tokamak under construction in France.

Key to the fix was modified electronics for sensors that detect the magnetic field of the plasma and the plasma’s motion and position. The modified sensors quickly send a control signal that can provide feedback on the vertical position. The feedback uses an in-vessel vertical control coil (IVC) to push back on the changes in the vertical position and prevent termination of the plasma. Providing the electronics were KSTAR researchers Jun Gyo Bak and Heungsu Kim; leading the effort were Mueller and KSTAR’s Sang-hee Hahn.

In addition to the sensor improvements, Nicholas Eidietis of General Atomics developed a control system that distinguishes between fast and slow changes in the sensor signals and directs different coils to respond to the plasma movement on different time scales. The end result of this international teamwork is a control system that responds effectively to movements of the plasma, enabling operation with taller plasmas that exceed the KSTAR design requirements.

Physicist Dennis Mueller with image of KSTAR on left screen behind him

PPPL engineers solve problem for the DIII-D tokamak in San Diego

Fusion power, which lights the sun and stars, requires millions of degrees of heat to fuse the particles inside the plasma that fuels fusion reactions. Here on Earth, scientists developing fusion as a safe, clean and abundant source of energy must produce temperatures hotter than the core of the sun inside tokamaks. Much of the power needed to reach these temperatures comes from high-energy beams that physicists pump into the plasma through devices known as neutral beam injectors.

PPPL engineers have designed and delivered six sets of innovative new components for injectors that heat the plasma in the DIII-D National Fusion Facility that General Atomics operates in San Diego for the U.S. Department of Energy.

The redesigned parts, called pole shields, protect magnets in the injectors from energetic particles in the beams and will replace units that melted and cracked during previous fusion experiments, resulting in water leaks. The magnets redirect charged atomic nuclei, or ions, in the beams to an ion dump inside the injectors, permitting only neutral atoms to enter into the plasma.

PPPL delivered four new sets of shields in 2017 after delivering two earlier sets in 2014. “They had a problem that needed fixing. In the end, we came up with a solution that solved the problem,” said PPPL engineer Irving Zatz, who oversaw the design, analysis and delivery of the shields. He teamed with engineers Andrei Khodak, who ran computer analyses to verify the designs, and Alex Nagy, who heads PPPL engineering collaborations on DIII-D.

Pole shields are not the only parts that PPPL has upgraded for the DIII-D neutral beam injectors. The laboratory delivered two new calorimeters that measure heat in the machines last fall, plus a new collimator that aligns the neutrals in parallel beams earlier this year.

Engineers Andrei Khodak and Irving Zatz