Blog Posts

Writing about Fusion

Hi! I’m Paige, and I’m an undergraduate at Princeton interested in physics and science communications. This January, I got to work as an intern here at Princeton Satellite Systems. These past few weeks, I’ve been writing about the fusion-related projects PSS is working on, such as their Princeton Field-Reversed Configuration (PFRC) fusion reactor concept and plans for a space propulsion engine.

My first task was to write a four-page report on the PFRC, including its design, market demand, and development timeline. I knew very little about fusion coming into this internship, so first I had to learn all I could about the process that powers the sun and has the potential to supply the earth with clean, practically limitless energy.

Various types of fusion reactors are under development by companies and coalitions all over the world; they differ in the reactors they use and their methods of confining and heating plasma. ITER, for instance, is an example of a tokamak under construction in France; it uses superconducting magnets to confine plasma so that the reaction of tritium and deuterium can occur. 

The PFRC, currently in the second stage of experiments at the Princeton Plasma Physics Laboratory, uses radio frequency waves to create a rotating magnetic field that spins and heats the plasma inside, which is contained by closed magnetic field lines in a field-reversed configuration resulting from the opposition of a background solenoidal magnetic field to the field created by the rotating plasma current. The fusion reaction within the PFRC is that of helium-3 and deuterium, which offers multiple advantages over reactions involving tritium. Compared with other fusion reactors, the PFRC is incredibly compact.  It will be about the size of a minivan, 1/1000th the size of ITER; this compactness makes it ideal for portable or remote applications.

After learning about the design and market applications of the PFRC, I created a four page brochure about PFRC, writing for a general audience. I included the basics of the reactor design and its advantages over other reactors, as well as market estimates and the research and development timeline. I went on to write four page brochures about PSS’s Direct Fusion Drive engine, which will use PFRC technology for space propulsion purposes, and GAMOW, the program under which PSS is collaborating on developing various power electronics for fusion reactors.

These past few weeks have been quite informative to me, and I realized how much I loved writing about science and technology! I learned all about fusion, and I especially loved learning the details of the PFRC reactor design. To summarize the design, research, and development of the PFRC and other technologies within four page flyers, I had to learn how to write about technology and research comprehensively and engagingly for a general audience, which improved my science communication skills.

FIA Proposes Funding Fusion for Space Propulsion

The Space subcommittee of the Fusion Industry Association, of which we are a member, has prepared a new white paper recommending government funding for a fusion propulsion development program, styled similarly to ARPA-E and DARPA.

The goal is to provide funding not just for “paper studies,” but enough funding to build real hardware and start to test fusion propulsion concepts. We want the US to remain competitive in the upcoming Deep Space Race – building a human presence on the Moon, and then Mars, and beyond.

The PFRC is directly applicable, configured as Direct Fusion Drive – a variable thrust, variable specific impulse rocket in the 1 to 10 MW range. With sufficient funding, we could build a PFRC-3 to test a fully superconducting configuration’s ability to achieve fusion-relevant plasma temperatures, and a separate propulsion testbed to develop the thrust augmentation system. This is the actual mechanism to transfer the energy from the fusion products to a rocket propellant – a fusion reactor is not a rocket until you have accelerated a propellant! For more on the Direct Fusion Drive, see our related videos:


As a follow-up to the TriAgency workshop on Compact Fusion which took place on April 28, PFS was invited to join several Fusion Industry Association members on an AIAA ASCENDx summit on June 15, “Accelerating Pathways to Space”:

Our panel on “New Opportunities in Fusion for Space Power and Propulsion” was moderated by Julie Reiss of Aerospace Corp and included us, Helicity Space, NearStar Fusion, and Tokamak Energy. You can register to rewatch our panel discussion anytime!

A key takeaway from the TriAgency workshop was that investment in compact fusion is strategic for both space and defense applications. NASA’s Ron Litchford was quoted as saying:

Compact fusion stands as a well deserving candidate for an aggressive whole-of-government R&D initiative.

Ron Litchford, Principal Technologist of NASA’s Game Changing Development Program, April 2021

We appreciated the opportunity to participate in the panel and will continue to advocate for more investment in compact fusion!

Thomson scattering

Thomson scattering is the industry standard diagnostic for measuring electron temperature, typically requiring, large, expensive, custom lasers. We are fortunate that ARPA-E has funded a team from Oakridge National Laboratory to build a portable Thomson system from commercial parts, and they are now installing and calibrating the diagnostic on the PFRC-2!

These measurements will give us critical insight on the plasma temperatures we are achieving with RMFo as a function of input power!

The ARPA-E Energy Summit May 24-27

Princeton Fusion Systems will have two booths at the virtual ARPA-E Energy Innovation Summit on May 24-27. One will be for our ARPA-E OPEN 2018 grant and the other for our recent awarded GAMOW power electronics grant. We’ll be at our booths, along with our team members from the National Renewable Energy Laboratory, PPPL, United SiC and Princeton University, from 1:15 to 2:30 on Monday, 3:45 to 5:00 on Tuesday and 2:30 to 4:00 on Wednesday. Please come by to talk!

We’ll also be doing a Tech Demo: Next-Generation PFRC on Monday, May 24, 2021 2:05 p.m. – 2:15 p.m.​​​​​​​ You’ll find out about our innovative compact nuclear fusion reactor work.

The Summit will have all sorts of cutting edge technology from ARPA-E companies. There will be many interesting speakers including Secretary Jennifer Granholm and Secretary Pete Buttigieg. The Summit will also include breakout sections where you can meet other attendees.

The ARPA-E Summit is the energy event of the year. Don’t miss out!

Princeton Fusion Systems Awarded $1.1 Million from ARPA-E for Transformational Energy Technology

Princeton Fusion Systems announced today that it was awarded $1.1 million in funding from the U.S. Department of Energy’s Advanced Research Projects Agency-Energy (ARPA-E). The funding will be used to develop advanced power electronics for the heating and control of fusion plasmas.

Princeton Fusion Systems received this competitive award from ARPA-E’s Galvanizing Advances in Market-aligned fusion for an Overabundance of Watts (GAMOW) program, working to close multiple fusion-specific technological gaps that will be needed to connect a net-energy-gain “fusion core,” once it is ready, to a deployable, commercially attractive fusion system. Princeton Fusion Systems joins 13 other teams in the $29M GAMOW program.

The team consists of Princeton Fusion Systems, Princeton University, the National Renewable Energy Laboratory and United Silicon Carbide. Over the 30 month duration of the contract, the team will develop efficient, high-power electrical drivers for plasma heating, compression, and control. Wide-bandgap (WBG) semiconductor devices and innovative amplifiers may speed up the development of fusion systems and reduce their eventual cost of electricity. Princeton Fusion Systems will develop prototype, high efficiency switching amplifiers using WBG SiC devices and amplifier boards that employ advanced cooling and digital control. The project will design, test, and qualify individual circuit boards as the building blocks for various short-pulse, long-pulse, and continuous-wave electrical-driver power supplies for fusion-energy systems.

Portable Diagnostic: from ORNL to PPPL

Our team is mentioned in this press release from ORNL about the “traveling” high-temperature plasma diagnostic they are building:

The ORNL diagnostic team
The ORNL diagnostic team

ARPA-E is supporting the development of several such portable diagnostics in tandem with their other fusion efforts, including our OPEN project. The ORNL team hopes that their “suitcase Thomson scattering” diagnostic will be on its way to us this summer!

When installed, it will measure the electron temperature and density profiles in the PFRC-2 experiment as a function of radius, as often as once per millisecond. The profiles measured will allow us to probe the internal structure of the plasma, but beyond that will also allow us to better interpret the results of our other diagnostics!

Princeton Propeller Talk

Princeton Propeller is a series of talks supported by the Princeton Area Alumni Association (PA3) to showcase technical innovation. Our team was recently invited to give a talk on the new frontier of commercial fusion development! Dr. Swanson and Ms. Thomas took the podium on February 11, 2020, at the Quadrangle Club on Princeton’s campus.

Download our slides at this link:
“Frontiers in Commercializing Fusion Development” Slides

We are now joined by over a dozen private companies in the UK and the US pursuing commercial fusion development. Recent programs in the Department of Energy and their ARPA-E advanced projects division have supported teams in magneto-inertial confinement (ALPHA), compact tokamaks, pinches, and our PFRC (OPEN), and public-private partnerships between labs and the private companies (INFUSE). It’s a great time to be in fusion research!