Jacob earned his bachelor’s degree in engineering physics from Wright State University in 2013. After graduation, he attend Cornell University and joined the Laboratory of Plasma Studies, where he spent most of his time developing various plasma diagnostics. Now that he has defended his Thesis, “Development of a Thomson Scattering Diagnostic on a Pulsed Power Machine and its use in Studying Laboratory Plasma Jets Focusing on the Effect of Current Polarity”, he is continuing as a postdoc in the lab before starting as a postdoc at UCSD in 2020.
July 28 – August 10, 2019
UC San Diego campus, La Jolla, CA
This 2-week summer school will promote scholastic development through technical lectures given by field experts as well as professional development sessions aimed at early-career researchers in HEDS fields of study.
The summer school is jointly organized by the by the Center for Frontiers in High Energy Density Science and the new NNSA Center for Excellence: Center for Matter Under Extreme Conditions.
Working with Dr. Stephanie Hansen at Sandia National Labs computing dielectric functions and stopping numbers for materials and plasmas that have high temperatures but that are dense enough that quantum mechanics must be considered in the interactions between electrons. Stopping numbers are useful quantities because they can tell us how particles lose energy as they travel through these plasmas. Dielectric functions are important because you can calculate the so-called dynamic structure factor of these warm, dense materials from them. The structure factor can be measured by Thomson scattering, which is one of the experimental probes used at LPS. This provides a nice link between the theory I am doing and the experiments performed at Cornell.
Jason Hamilton is interning at Lawrence Livermore National Lab this summer. He is working a project entitled, “Demonstrating heat transport with Perseus and comparing the higher-moment formulation to the results of various codes used at LLNL.”
Plasma is one of the four fundamental states of matter, but it does not exist freely on the Earth’s surface. It must be artificially generated by heating or subjecting a neutral gas to a strong electromagnetic field. Located in the basement of Grumman Hall are two large pulse-power generators that create plasma by delivering extremely high currents to ordinary matter for short periods. These generators are part of the Lab of Plasma Studies at Cornell University.
The lab has studied different aspect of plasma since its inception in 1967, including electron beams, microwave generation, ion beams, and Z-pinches (in which an electric current produces a magnetic field that compresses the plasma). High-energy dense plasma research is commonly associated with nuclear weapons, as well as space and astrophysics, controlled fusion, accelerator physics, and beam storage. The mission of the lab is to understand the fundamental physics underlying plasma. The ultimate research goal is to discover a means to generate a new form of energy: a controlled fusion system that produces nuclear reactions similar to those happening at the center of the sun, but safe to harness for energy production on earth.
The work carried out in the Lab of Plasma Studies is supported by the Unites States Department of Energy and the National Nuclear Security Administration’s Stewardship Sciences Academic Programs. An important endeavor of the lab is to train new generations of plasma research scientists. Undergraduate and graduate students, postdoctoral associates, visiting scientists, and visiting professors are active contributors. The lab’s stewardship efforts have been successful, with many scientists in pulse-power programs around the country, hailing from Cornell.
“In the College of Engineering things have been getting very small, think nanoscale. Our lab is the opposite of that. We have very large machines that enable students to handle large-scale equipment that produce large powers. It is a different scale of operation, and it provides a category of projects that are mostly not provided within the academic programs at Cornell,” says David Hammer, Electrical and Computer Engineering, and a faculty member in the lab. “It’s a big operation,” says Bruce Kusse, Applied and Engineering Physics, another faculty member in the lab. “Cornell has invested a great deal into the lab over the last 50 years, and it’s paid off. The national labs that study plasma, like the Sandia National Laboratories in Albuquerque, New Mexico, often come to us when they need something studied quickly and efficiently.”
Cornell’s Laboratory of Plasma Studies (LPS) has much to celebrate as it marks its 50th anniversary with a two-day symposium, Oct. 6-7, and begins another five years of unlocking the secrets of plasma with a $15 million grant from the National Nuclear Security Administration.
Since its inception in 1967, the lab has used powerful bursts of energy to create and study plasma – a state of matter in which atoms are ionized and their electrons become free. Operating in the High Voltage Laboratory on Ithaca’s Mitchell Street before moving into the basement of Upson Hall and then Grumman Hall, LPS was one of the world’s first high-energy-density plasma labs based at a university and has kept Cornell at the forefront of plasma science through the years.
Many of the physicists and engineers who made discoveries there will return to campus for the symposium, which will feature 40 alumni speaking in Clark Hall about how their time at LPS influenced their careers in academia, government and industry.
“We’ve populated the pulse-powered programs of the country more than anyone else,” said David Hammer, LPS co-director and professor of electrical and computer engineering. He was a graduate student when the lab was founded and says most experiments throughout the lab’s history have been centered around technologies that store energy in capacitors and deliver it quickly through powerful pulses of current.
“These machines have been used to extract a number of directed energy sources from plasma. It started out with electron beams when the lab was founded, then it became microwave generation, and then ion beams. Now, Z-pinches make up a large percentage of our work,” said Hammer.
Bruce Kusse, LPS co-director and professor of applied and engineering physics, joined the lab as a research associate shortly after it was founded and still remembers its first machine, scrapped together by researchers for electron beam extraction.
“It was made partially with plywood, epoxy and plastic,” said Kusse, noting that being on the forefront of plasma science means LPS has always had to customize its equipment.
Today, the lab boasts its own machine shop; researchers produce parts they need for two world-class, pulsed-power machines and state-of-the-art diagnostic tools. Both machines produce energy pulses lasting 100 to 200 nanoseconds, one at a half-million amperes and the other at 1 million amperes. The machines produce Z-pinches, in which electric currents produce a magnetic field that compresses the plasma, giving it new properties that scientists are still working to fully comprehend.
A major contribution of LPS to science has been diagnostic tools it’s developed to characterize high-energy-density plasma, which is highly unstable. “There’s myriad instabilities that are studied with these diagnostics, helping us to understand the physics behind these instabilities and how you can mitigate them,” said Kusse.
Scientists hope that a better understanding of the fundamental physics underlying plasma, X-ray busts and inertial fusion conditions will eventually lead to the holy grail of energy research: a controlled fusion system that produces nuclear reactions similar to those happening at the center of the sun, but safely harnesses the reactions for energy production.
It’s one of the concepts that has driven LPS research since its beginning, one researchers will continue to explore thanks to a $15 million, five-year grant taking effect Oct. 1. The funding enables LPS’s Multi-University Center of Excellence for Pulsed-Power-Driven High-Energy-Density Science to advance its research program in collaboration with scientists from the University of California, San Diego, Imperial College (London), the Lebedev Physical Institute (Moscow), the University of Michigan, Princeton University and the Weizmann Institute of Science (Israel).
This collaborative approach to experimental, theoretical and computational high-energy-density plasma research has been at the heart of LPS for 50 years.
“Having theorists and experimentalists working together to achieve the end point of a project, it’s worked out very well for the lab,” said Hammer.
Syl Kacapyr is public relations and content manager for the College of Engineering.
In the basement of Grumman Hall, an x-ray pulse produced by a hot, dense plasma – an ionized gas – lasting only fractions of a microsecond both begins and ends an experiment. Hidden within that fraction of time lies a piece of a puzzle—data that graduate students and staff scientists at the Laboratory of Plasma Studies (LPS) will use to better understand the mysterious physics behind inertial confinement fusion. While the high energy density research done by LPS does have other applications, fusion brings most of the students into this research field.
Founded in 1967 the first ten years of the lab were focused on relativistic electron beam experiments, including high power microwave generation. Intense ion beam experiments were added in the late 1970s. In the late 1980s, LPS began working on pinch plasmas, gradually experimenting with exploding wires, multiple wire arrays and other forms of z-pinch experiments. Many of these experiments continue today, with applications including intense x-ray sources and inertial fusion.
“All of the work at LPS is now with one form or another of 500,000 to 1-million ampere current-driven plasmas called z-pinches,” said David Hammer, Professor of Electrical and Computer Engineering.
Undergraduate, M.Eng and Ph.D. students all run experiments using the lab’s two pulse-power machines, both instrumented with diagnostics, including x-ray, extreme ultraviolet and visible light diagnostics. Lasers are used to take images and make measurements.
COBRA, the 1-million ampere pulsed-power machine, is two stories tall and so heavy it had to be constructed on solid bedrock. It is completely custom, so if something goes wrong, group members must sit down with their technicians and machinists to find a way to fix it sometimes by making a special-purpose tool or building a replacement piece of hardware, sometimes in a matter of minutes.
Current is pushed through the machine at enormous rates, but for an incredibly short time. “We’re working on z-pinch experiments where a large z-directed current is driven to the extent that things don’t explode anymore—they start to explode and then they implode from the magnetic forces,” said Bruce Kusse, Professor of Applied and Engineering Physics. “That squeezing down produces the high energy density plasmas similar to inertial fusion plasmas and plasmas that make a lot of x-rays.”
These z-pinch plasmas are wildly unstable and only squeeze or pinch in small areas and for very short times. The group is continually working on ways to find more stable, longer pinches.
“These are all short pulse experiments,” said Hammer. “Inertial confinement fusion requires a pulse only billionths of a second long, so you can see results only on instrumentation.”
A long experiment may be two-tenths of a microsecond, and the x-ray pulse produced by a pinch lasts only 20- or 30-millionths of a microsecond. Experiments themselves seem to take no time at all and information is available almost instantaneously. But it can require a significant amount of time to figure out what it all means.
“We can make these plasmas but they exist for such a short amount of time, that it’s really hard to get in there and figure out exactly what is going on. And so that’s what we’re working on,” said Sophia Rocco, a second-year Ph.D. student with LPS.
“While intense x-rays for nuclear weapon effect simulation kept plasma programs going for decades, at the back of everyone’s mind, including a large fraction of the students we’ve educated here at Cornell, is fusion,” said Hammer. “Many people want to contribute to the achievement of that great engineering challenge. That is what motivates many of the students. Others come just because it is intellectually interesting.”
Intellectually interesting, indeed. The lab is currently looking further into the physics behind how high energy density plasmas are formed and why they are so unstable. Over the past 50 years, they have uncovered many questions still in need of answers. They have also amassed a trove of diagnostics to help discover the answers, enough to keep them very busy for some time. The lab is now working on utilizing these diagnostics to understand the z-pinch plasmas they’re producing so they can compare the results with theoretical models and use them to validate their computer simulations.
“By looking at the fundamental physics of high energy density plasmas, we hope we can contribute to the practicalities that will eventually lead to inertial confinement fusion,” said Hammer.
There are many other things that plasmas could be useful for as well, ranging from plasma medicine and sanitization, all the way up to accelerating relativistic particles and understanding the mysteries of the universe.
“The fact is most of the universe is not in the form of solid matter. Instead it is in the form of plasma or some form that we cannot see,” said Hammer. “We understand a good deal of what we’re looking at in our experiments, but there is so much more to uncover. So many things have yet to be explored in the universe of plasmas. We have a field that’s going to be around for a long time.”
When she was looking at graduate schools, physics major Sophia Rocco thought she would be in a materials science program bridging her interests in electricity and magnetism and novel materials for solar cells. Chancing upon the School of Electrical and Computer Engineering at Cornell, she discovered the Laboratory of Plasma Studies (LPS). As she learned more about the lab and the idea of fusion reactors as an infinitely renewable clean energy source, Rocco realized that she wasn’t necessarily interested in solar power, but the crossover of electricity and magnetism and the potential for renewable energy.
“When I say to most people that I do plasma physics, they say ‘Oh, so you work with blood?’” says Rocco, a second-year Ph.D. student in the Laboratory of Plasma Studies at Cornell. “And then I get to explain that the name ‘plasma’ is actually misleading.”
A plasma is basically a highly ionized gas. Overall, it is not charged but because the atoms are ionized, the electrons are free from the bonds of the nucleus. If you put it in an external electric or magnetic field, you’ll get different behavior from the protons and neutrons than you will from the electrons, which is not at all the way a gas behaves.
Using a magnetic field, you can confine a plasma, an idea being investigated with the goal of a controlled fusion reaction. Research is underway to answer questions like: Do certain kinds of magnetic fields affect certain kinds of plasmas? What instabilities do you get? And can you actually confine a plasma in this way?
When she first came to LPS, Rocco knew very little about plasma physics. It’s clear she’s come a long way and yet admits that she’s still learning about the field. “This is a very supportive lab environment,” said Rocco. “Everyone is always incredibly willing to answer my questions, and let me jump in and try to help and explain their experiments to me. We have a great team of technicians that help us run the machines, but if there’s anything we want to learn, anything we want to help with, it’s greatly encouraged. You’re really encouraged to understand what is going on and develop of your own diagnostics. That’s what really impresses me about the lab—it’s very hands on.”
Rocco uses COBRA, the 1 million ampere pulse-power machine at LPS to produce plasmas out of puffs of gas. “Gas puffs are generally thought to be used as x-ray sources, but I’m not really looking at them in that way,” said Rocco. “I’m looking at what goes on before they produce the x-rays, at the basic science of what’s really going on.”
COBRA’s gas puff valve has three concentric nozzles with a jet in the center. The two rings surrounding the jet can be filled with whatever gas and density profile she wants, usually using neon, argon or krypton. The current goes through the gas puff and creates a magnetic field that compresses down the ionized gas, making a sleeve around it and bringing it into a pinch at the center. This is called a z-pinch because the current is going in the z-direction.
“The current goes up, then around and pinches it at the center,” says Rocco. “Generally there is inward radial motion, but within that things are eddying around, with the cooler, outer material mixing with the hotter material closer to the center, creating instabilities. If you’re trying to create fusion, you want to have stable plasma conditions. We’re trying to mitigate instability and figure out where it is happening so we can make the plasma more stable.”
There is a good understanding already of the instabilities in gas puffs and in plasma in general but Rocco is interested in seeing where exactly things are going, how the instability is seeded, where it comes from and how the instability grows as the implosion proceeds. She looks at the distribution of flow velocities within the z-pinch to find answers to even more specific questions like: Where are the ions going? Where are the electrons going? How fast are they moving? Are they only coming in radially or are they also rotating as they move? Is there any turbulence? If the dynamics of the implosion can be better understood, there is potential for it to be controlled, and possibly used.
“What do I like most about what I do?” said Rocco. “I know I wouldn’t be happy doing something that was easier. I would be bored. I work very hard, but I do it because I love it and the challenge of it. If I can contribute just a tiny drop in the bucket towards making renewable fusion energy happen in the future, that would be great. If by doing that, I can somehow make the world a little bit of a better place and contribute to a general understanding of how the world works, why things work the way they do, that’s another part of the drive. And especially with plasma there’s still so much to be found out.”