NDCX-II: a stadium for “the X-Games of contemporary science”
ATAP has long been involved in the quest for inertial fusion energy (IFE) as a future power source — primarily through heavy-ion induction accelerators, an approach pioneered here. This work has opened interesting new research directions.
The emergent science of high-energy-density physics with laboratory plasmas has come to play a large role in our program. Some key aspects of HEDP—dubbed “the X Games of contemporary science” by a National Research Council committee—are a natural match for the experimental facilities (notably an accelerator called Neutralized Drift Compression Experiment II), computer-modeling techniques, and other expertise of our program.
HEDP is closely related to IFE target physics. Additionally, NDCX-II could support basic R&D toward the development of advanced materials that will be needed for the future of fusion energy, where they must withstand 14.1-MeV neutrons that are more damaging than the lower-energy neutrons from fission reactors. Our work in fusion energy sciences has focused increasingly on this new facility, which also makes beamtime available to outside researchers interested in various aspects of HEDP.
NDCX-II: A Unique Capability for HEDP Research
With the support of the American Recovery and Reinvestment Act, we built an accelerator called the Neutralized Drift Compression Experiment II, and began using this machine (and, alongside it, NDCX-I) for HEDP experiments. Since mid-2014 we have been using renewed funding from the DOE Office of Fusion Energy to build out NDCX-II to its full potential.
When the present build-out phase is complete, NDCX-II will deliver intense, short pulses of ion beams, e.g., 1-ns, 50 nC/bunch, 1.25 MeV beams of lithium ions at 1 pulse every 30 seconds. With focusing and drift compression — beam manipulations that we studied extensively for fusion-energy purposes — this will enable uniform heating of 2-micron-thick targets to a temperature of one electron-volt.
While the achievable target temperature at NDCX-II is much lower than what can be achieved with intense laser pulses, the excited volume is relatively large and uniformly heated, which enables precision diagnostics of the transient warm-dense-matter state.
The high degree of tunability and control in ion species (e.g., He, Li, K, Cs), kinetic energy (0.1 to 1.2 MeV), spot size (from less than 1 to as high as 10 mm2, and pulse length (from less than 1 to over 600 nanoseconds) allows us to tune excitation conditions across three physical regimes: from isolated collision cascades, through the onset of order-disorder phase transitions, to warm-dense-matter states.
NDCX-II and Materials Science for Fusion Energy
Fusion energy, whether inertially or magnetically confined, has long been attractive for its environmental sustainability and the near unlimited supply of “fuel.” It can however be rough on equipment. Most of the energy comes out in the form of 14.1-MeV neutrons with a kinetic energy is much higher than those from fission reactors. Materials that can withstand them, and/or become less radioactivated, will be needed.
NDCX-II enables systematic pump-probe study of the dynamics of radiation-induced defects of fusion materials. Compared to other means of performing this basic research, NDCX-II is attractive because of its high repetition rate (two pulses per minute) and short ion pulses, as well as by the direct way in which ions interact with the material being tested.
Understanding the multi-scale time evolution of radiation damage, from picoseconds to seconds, is of fundamental importance for our understanding of radiation effects in natural processes. It can aid the development of advanced materials for use in any high radiation environments (including not only fusion materials but also fission reactor components or space electronics). Our goal is first-in-class in-situ data on short time scales to experimentally benchmark simulation tools that are widely used to predict the evolution of radiation damage in materials.
Pushing the capability to control very intense, space-charge-limited ion beams will also help lay the foundation for inertial-fusion-energy drivers and, generally, inform the development of ion beam technologies at the intensity limits. This will be useful for a wide range of applications in high energy physics, medicine, materials processing and national security.
To Learn More…
NDCX-II and its uses are the subjects of “A New Accelerator to Study Steps on the Path to Fusion”, a feature article by Berkeley Lab’s public information department.
For more information on the uses of NDCX-II, see this article, circa the beginning of the project.
Background Brief: The Why and How of Inertial Fusion Energy
The DOE supports two approaches to controlled fusion. One is called magnetic fusion energy and is based on a large, continually reacting plasma confined by “magnetic bottles” such as tokamaks. The other approach is inertial fusion energy, in which a small capsule of fusion fuel is heated and compressed, so that the fusion reaction take place before the fuel has a chance to overcome its own inertia and fly apart. A large program, supported by the DOE’s National Nuclear Security Agency, is studying the basic physics of the inertial approach, using powerful lasers to drive this reaction.
Heavy-Ion IFE Research at Berkeley Lab
LBNL’s Fusion Energy program is part of a smaller parallel effort, supported by the DOE’s Office of Science, to harness inertial fusion energy for electric power production by using powerful and energetic beams of heavy ions to “drive” the target. Regardless of the drive method, long-term goal is for the targets to yield much more energy than was put into them by the beams.
Our program has the long-range goal of developing suitable heavy-ion accelerators that will not only drive a fusion target, but do so with a cost, efficiency, and reliability that make business sense as the basis for a power plant.
Since our beginnings in 1982, we have been progressively scaling up induction accelerator systems that transport beams, give them more energy, and focus and compress the pulses so as to impart the most energy to the target as quickly as possible. This is the context in which NDCX-II came into being. We collaborate deeply with other institutions, most prominently Lawrence Livermore National Laboratory and Princeton Plasma Physics Laboratory, in this long-term effort.
We are part of the Fusion Science & Ion Beam Technology Program in ATAP Division.
For further information, here is a detailed inertial-fusion-energy tutorial.