August 31

How Ignition and Target Gain > 1 Was Achieved In Inertial Fusion

Omar Hurricane, Chief Scientist for the Inertial Confinement Fusion Program (LLNL)

Location: 700 Clark Hall

For many decades the running joke in fusion research has been that “fusion” is twenty years away and always will be. Yet, this year we find ourselves in a position where we can talk about the milestones of burning plasmas, fusion ignition, and target energy gain greater than unity in the past tense—a situation that is remarkable! In this talk, we tell the story of the applied physics challenges that needed to be overcome to achieve these milestones and the strategy our team followed. To help understand the story, several key physics principles of inertial fusion will be presented, and I will try and dispel any confusion about what the terms burning, ignition, and gain mean in the context of inertial fusion research.

September 21

Perspectives on Beam-Driven Plasma-Based Acceleration

Chandrashekhar (Chan) Joshi, Distinguished Chancellor’s Professor of Electrical Engineering (UCLA)

Location: 401 Physical Science Building

Particle accelerators have been engines of discovery in our understanding of the Universe and have applications in many areas of modern life from medicine to security. The most powerful ones are 10’s of kilometers in length, determined by the strength of the accelerating electric field. It has been four decades since the concept of using a relativistic plasma wake for charged particle acceleration was first proposed. In relativistic plasma wakes the accelerating electric field can be orders of magnitude greater than in a conventional accelerator with the potential to reduce the size of the accelerating structure. The driver for producing such wakes can be in intense laser pulse or a high current charged-particle beam. During this time ingenious solutions for generating the ultra-high electric field over meter-scale distances, and generating and accelerating high quality electron and positron beams using such wakes have been realized. In this talk I will give a personal perspective on the progress of the field of plasma-based acceleration driven by ultrashort electron bunches and where it is headed.

October 5

SPARC and the High-field Path to Fusion Energy

Dennis Whyte, Director, Plasma Science and Fusion Center, Hitachi America Professor of Engineering (MIT), Co-Founder of Commonwealth Fusion Systems

Location: 700 Clark Hall

The advent of REBCO high-temperature superconductors at commercial scale has changed the development path for producing fusion energy with magnetic confinement. The design and test of a large-bore B>20 tesla peak field superconducting magnet at MIT PSFC, in collaboration with Commonwealth Fusion Systems, realizes a doubling of the allowed B field compared to previous state of the art.  This realizes extremely large gains in fusion performance fusion power density scales as B4 and access to ignition as ~B5 at fixed plasma physics. These gains in turn allow for operation away from limits, yet in much smaller and less expensive devices. CFS is presently constructing the high-B tokamak SPARC outside Boston with MIT as its major scientific collaborator, with the goal of demonstrating high fusion energy gain and fusion power density that propels fusion into the commercial energy sector. In addition to describing SPARC, parallel key fusion technology development programs will be described.

October 12

Thermonuclear fusion conditions in a sheared-flow-stabilized Z pinch

Uri Shumlak, Professor of Aeronautics & Astronautics (University of Washington), Co-Founder and Chief Scientist of Zap Energy

Location: 700 Clark Hall

Fusion energy concepts aim to heat and confine plasma while maintaining stability. Thermonuclear fusion approaches use a plasma that has relaxed to a local thermodynamic equilibrium, thereby reducing the drive for kinetic microinstabilities. Many confinement configurations use large magnetic field coils to stabilize the plasma. The Z pinch uses no magnetic field coils. The axial plasma current produces the confining magnetic field that balances the plasma pressure. Increasing the current adiabatically compresses the Z-pinch plasma leading to higher density and temperature. While the Z pinch has many attractive features, it generally suffers from macroinstabilities that destroy confinement. The sheared-flow-stabilized (SFS) Z pinch uses axial flows to provide stability, has demonstrated an ability to confine plasmas to fusion conditions without magnetic field coils, and promises a compact fusion device. Experimental results will be presented that demonstrate high performance plasmas and sustained fusion reactions from the FuZE (Fusion Z-pinch Experiment) SFS Z-pinch device. Neutron energy measurements indicate a thermonuclear fusion process that scales consistent with adiabatic compression. High-fidelity numerical simulations suggest a path to reactor-grade plasma conditions. Theoretical scaling studies will be presented of an SFS Z pinch as a high-gain fusion energy source and as a fusion space thruster, which generates high exhaust velocities and high thrust with low system mass. Thermonuclear fusion provides a large energy release per reactant mass and offers a carbon-free energy source for terrestrial power and a solution for rapid space propulsion.

October 19

Bigger is Better: NLO-Boosted Excimer Lasers for Inertial Fusion Energy

Connor Galloway, CEO of Xcimer Energy

Location: 700 Clark Hall

The National Ignition Facility achieved scientific breakeven in December 2022. While this was a major accomplishment, many challenges remain in making Inertial Fusion Energy (IFE) a reality. In particular, reliable commercial IFE will require a laser system that is much more efficient, lower cost, and higher energy, with superior spatio-temporal control of laser radiation. To accomplish this, Xcimer Energy is combining χ3 nonlinear optical (NLO) gas amplifiers with high-energy excimer amplifiers in a highly flexible architecture that can scale to tens of megajoules of laser energy on-target with an efficiency of 5% to 7% and cost of tens of dollars per joule, and the ability to deliver energy to-target from a very small solid angle (<10e-3 sr). This will provide a practical path to rapidly demonstrate and commercialize IFE by allowing the use of simpler fusion targets that can achieve high gain robustly, and allowing repetition rates for electrical power production of under 1 Hz which relaxes requirements throughout the plant. Furthermore, this laser architecture enables the well-studied HYLIFE reactor concept utilizing thick liquid FLiBe molten salt flows to protect the first structural wall, allowing a 30-year lifetime from existing low-activation steel and eliminating the need to develop and qualify new first-wall materials.

November 16

Thermonuclear Ignition via Lasers and Prospects for Inertial Fusion Energy

Riccardo Betti, Robert L. McCrory Professor of Mechanical Engineering and Director of the Fusion Science Center of Extreme States of Matter and Fast Ignition (University of Rochester), Chief Scientist (Laboratory for Laser Energetics)

Location: 700 Clark Hall

Recent progress in both direct- and indirect-drive ICF (inertial confinement fusion) has considerably improved the prospects for achieving energy gains with megajoule-class lasers. Recent implosions on the National Ignition Facility (NIF) using the indirect-drive approach have achieved over 3 MJ of fusion yield, a target gain of 1.5x and core conditions that can be interpreted as ignition of the DT fuel. The next step is to better understand the factors most critical to increase the energy gains to achieve fusion yields of interest to the stockpile stewardship program and to inertial fusion energy. When hydrodynamically scaled to NIF laser energies, recent direct-drive implosions on OMEGA are expected to produce over a megajoule of fusion yield and about 85% of the Lawson triple product required for ignition. Those implosions have benefited from a significant increase in implosion performance obtained through a statistical approach used in designing OMEGA targets and laser pulse shapes. An overview of the status of laser ICF and prospects for short-term advances in inertial fusion energy will be presented.