July 2023 Newsletter

From the Editor

Oriol T. Valls, the current Physics and Society Newsletter Editor, is a Condensed Matter theorist at the University of Minnesota.

We have three articles in this July issue: One is on further progress on controlled nuclear fusion, a process that could be very important socially if it pans out at the end. We will see. The second is basically a long extended comment on an article, also on controlled fusion, which we published in a recent issue. Finally, we have an article by one of the Forum’s invited speakers at the April meeting. In a forthcoming issue I hope to publish articles by this year’s winners of the Szilard and Burton Forum awards. They also spoke at the April meeting. Their bios appeared in the April issue of this newsletter.

We have also a letter to the Editor, commenting on a previously published article. Such comments are always welcome, whether they are complimentary or critical. And our new Book Reviews Editor, Quinn Campagna, continues to provide us with a couple of pertinent reviews for each issue.

Our Media Editor Tabitha plans to retire from her job after this issue. I am very grateful to her for the job she has done these past five years. We are advertising for a successor. This is a great opportunity for somebody up to date on everything related to social media, and who wants to get more involved in Forum activities. Please apply if interested.

Once more, the contents of this newsletter are very largely reader driven. Please consider sending your contribution. Manuscripts should be sent to me, preferably in .docx format, except Book Reviews which should be sent directly to book reviews editor Quinn Campagna (qcampagn@go.olemiss.edu). Content is not peer reviewed and opinions given are the author’s only, not necessarily mine, nor the Forum’s nor, a fortiori, the APS’s either. No pertinent subject needs to be avoided on the grounds that it might be controversial. Controversy is good.

On this controversy business, and my liking for it, I found out very recently that in fact there is an online peer reviewed journal called “The journal of controversial ideas”. You can look it up. The first article I clicked on was co-authored by one of my most distinguished colleagues at Minnesota, Misha Shifman, and among his co-authors there were a couple of Nobel prize winners. My only quibble about their article and others in the journal, is that its topic is not one that I think should be controversial. But you never know. So, I joined their Editorial Board.

Oriol T. Valls                                                                                                                                          
University of Minnesota                                                                                                                             
otvalls@umn.edu

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Forum News

FPS Newsletter Media Editor Wanted

The FPS newsletter is looking for a Media Editor to help increase the electronic and social media presence of the Forum and its quarterly newsletter. The Media Editor works with the Editor and the APS Media team. Responsibilities and duties are quite flexible, but might include developing outreach through the Engage community site and expanding the media presence of the newsletter. This is a great opportunity for a media savvy person who is interested in getting more involved with the Forum and with APS. Please contact the Newsletter Editor at otvalls@umn.edu or the current Media Editor tabithacolter@gmail.com if you think you might be interested in volunteering for this position.

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New (2022) APS Fellows Sponsored by the Forum

Four Forum-sponsored members were named APS Fellows in 2022, three of them received their diplomas at the 2023 April meeting.

Jean Bio Chabi Orou 

Institut de Mathématiques et de Sciences Physiques

Citation: For extraordinary contributions to and leadership of physics, education, and policy through public service in Benin and UNESCO, for inspiring and empowering primary and secondary teachers, and for raising physics capability as a foundation for sustainable development in Africa.

Ibiyinka Fuwape 

Michael and Cecilia Ibru University

Citation: For decades of leadership in the advancement of women in physics in Nigeria and Africa, along with major research contributions solving problems in climate change, agriculture, and finance at the interface of physics and society, thereby benefiting economic development in Africa.

Mary Y. P. Hockaday 

Los Alamos National Laboratory

Citation: For essential contributions to national security science and international scientific collaboration, leadership in fostering dialogue among diverse technical and policy communities, and promotion of equity and inclusion, especially for women in physics.

Richard Taylor 

University of Oregon

Citation: For creative and innovative use of physics in developing applications of fractals that impact society.

Letter to the Editor

Dear Editor,

This letter involves M.V. Ramana's article in the April FPS "Infeasible: Nuclear Energy as a solution to Climate Change". There is a one word answer to his (or her?) claims: "France". France, over the decades has built up a nuclear infrastructure capable of supplying 70-80% of its electricity without decades long construction delays on each reactor, without impoverishing its citizens, without trashing its environment, and without creating a proliferation risk. And by the way, France has one of the lower costs of electricity in Europe, as one can see from the chart from (Residential electricity prices worldwide 2022 | Statista)

<https://www.statista.com/statistics/263492/electricity-prices-in-selected-countries/.>). 

Wally Manheimer
Wallymanheimer@yahoo.com

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Articles

Star Power: Blazing the path to fusion ignition

Charlie Osolin, Osolin1@llnl.gov

It was the middle of the night on Dec. 5, 2022, and anticipation was building among the handful of researchers and technicians in the National Ignition Facility (NIF) control room. A set of pre-shot simulations had predicted a slightly better than 50-50 chance that the impending nuclear fusion experiment would reach or exceed “break-even” — producing as much or more energy than it used to drive the fusion reaction.

At 1:03 a.m., the computer-controlled countdown reached zero, shot director Joseph Griffo pronounced: “Shot!” and NIF’s 192 powerful lasers fired 2.05 megajoules (million joules) of ultraviolet energy into the ends of a pencil eraser-sized cylinder holding a tiny capsule of hydrogen fuel.

Radiation alarms sounded in unoccupied areas of the facility as the heavily-shielded target chamber was flooded with 1.12×1018 (1.12 quintillion) high-energy neutrons — the equivalent of 3.15 megajoules of fusion energy — produced by an explosive, self-sustaining thermonuclear reaction. Monitors began to display the unprecedented neutron yield captured by an array of diagnostic instruments, and the broad smiles and hearty high-fives around the control room told the story:

After 12 years of sustained effort and hundreds of experiments, NIF had achieved ignition — meeting a milestone that tantalized the inertial confinement fusion (ICF) community for more than 60 years and launching the era of controlled fusion ignition in the laboratory.

“This was only the second NIF shot to deliver more than two megajoules of ultraviolet energy to an ICF target,” said NIF Facility Manager Bruno Van Wonterghem. “This shot is just the beginning of a whole new level of ICF operations.”

Lawrence Livermore National Laboratory (LLNL) physicist Alex Zylstra, the shot’s principal experimentalist, was waiting at home for news of the result. “As the data started to come in,” he said, “we saw the first indications that we had produced more fusion energy than the laser input. One of the first things I did was call one of the diagnostic experts to double-check the data, and we kind of went from there.”

That expert was David Schlossberg, science lead for the NIF Nuclear Diagnostics group, who had asked Zylstra to call him if anything interesting happened.

“My phone rang at about 1:30 a.m. and it was Alex, quite excited,” Schlossberg said. “The first neutron data was rolling in, and it indicated higher performance than we’d ever seen before.

Researchers and technicians in the NIF Control Room react to U.S. Secretary of Energy Jennifer Granholm’s Dec. 13 announcement that NIF had achieved fusion ignition for the first time. Granholm likened ignition to the Wright Brothers’ first flight and called it “one of the most impressive scientific feats of the 21st century.” Credit: Jason Laurea 

“In the pitch black of my living room from 2 to 4 a.m. Monday morning,” he said, “I quickly confirmed the validity of these results and continued communicating with Alex. More data rolled in from other diagnostics, and we excitedly realized this was a momentous event.”

The preliminary data were quickly shared with Zylstra’s colleagues. Annie Kritcher, the experiment’s lead designer and team lead for integrated modeling, had gone to bed and was having “vivid dreams of all possible outcomes from the shot. This always happens before a shot,” she said, “from complete success to utter failure.

“Thankfully, Alex had sent me a message, so by the time I woke up, I saw that it wasn’t a failure. You see one diagnostic and you think, ‘Well, maybe that’s not real.’ And then you start to see more and more diagnostics rolling in pointing to the same thing, and it’s just a great feeling.”

Later that morning, members of the NIF management team could barely contain their excitement as they waited for the diagnostic data to be processed. They were overjoyed when the initial analysis confirmed that NIF had lived up to the promise of its middle name.

Over the next few days, the data were carefully analyzed by NIF’s nuclear diagnostics group, X-ray group and other target diagnostic experts and peer-reviewed by outside consultants. The validated results were announced to the rest of the NIF & Photon Science (NIF&PS) team on Dec. 9, and to the world through a U.S. Department of Energy (DOE) news conference on Dec. 13.

The historic achievement, which more than doubled NIF’s previous energy record, marked a significant advance in LLNL’s and NIF’s support for the National Nuclear Security Administration (NNSA)’s science-based Stockpile Stewardship Program to maintain the reliability and security of the nation’s nuclear deterrent without underground testing. It also demonstrated the fundamental science basis for inertial fusion energy (IFE) and emboldened further research into the development of IFE as a potential source of clean, safe and limitless energy.

INTERNATIONAL TEAMWORK

Reaching ignition was made possible by contributions from the Laboratory’s NIF&PS, Weapons and Complex Integration, Physical and Life Sciences and Computing teams; scientists, engineers, technicians and administrative and support personnel from throughout the Laboratory; and extensive collaborations with researchers in the world’s fusion, plasma physics and high energy density science communities in other national laboratories, universities and industry.

LLNL Director Kim Budil also credited “the many supporters and stakeholders in the National Nuclear Security Administration, the Department of Energy and in Congress, who’ve ensured we could reach this moment, even when the going was tough.

“The pursuit of fusion ignition in the laboratory is one of the most significant scientific challenges ever tackled by humanity,” Budil said. “Achieving it is a triumph of science, engineering, and most of all, people.”

Among the key factors enabling the breakthrough:

  • Creative experimental designs informed by steady increases in the scientific understanding of the complex physics of inertial confinement fusion.
  • Record levels of energy generated by NIF’s lasers.
  • Increasingly damage-resistant optics that enable the laser system to operate at energies and powers well beyond its design specifications.
  • Terabytes of data from NIF’s suite of more than 100 state-of-the-art nuclear, X-ray and optical diagnostics.
  • Enhanced experiment-based modeling and simulation that helped shape the new experimental designs.
  • Advancements in the metrology and fabrication of custom-made targets.

Ignition on NIF, the world’s largest and highest-energy laser system, means the nuclear fusion reactions sparked by the lasers produce as much or more energy than the laser energy delivered to the target — the definition of ignition used by the National Academy of Science in a 1997 review of NIF (see Achieving Fusion Ignition).

In NIF ICF experiments, a target capsule containing two forms of hydrogen, deuterium (D) and tritium (T), is suspended inside the cylindrical X-ray “oven,” called a hohlraum. On the capsule’s inside surface is a thin layer of cryogenically cooled DT. When the hohlraum is heated by NIF’s laser beams to temperatures of more than three million degrees Celsius, the resulting X rays heat and blow off, or ablate, the outer surface of the capsule, called the ablator. This causes a rocket-like implosion that compresses and heats the DT fuel.

In this “indirect-drive” process, the shape of the imploding fuel must remain as spherical as possible to maximize compression and form a stable central “hot spot.” Ignition occurs when the energy from a self-sustaining fusion reaction overcomes the cooling effects of X-ray losses, electron conduction and implosion expansion.

A technical panel of NIF scientists convened following the Dec. 13 DOE news conference to discuss details of the achievement and what ignition might mean for the future of fusion energy. Mark Herrmann (left), LLNL program director for Weapon Physics and Design, moderated. The panelists were (from left) Alex Zylstra, principal experimentalist; Annie Kritcher, lead designer; Jean-Michel Di Nicola, NIF laser systems chief engineer; Michael Stadermann, target fabrication program manager; Arthur Pak, team lead for stagnation science; and Tammy Ma, lead for the Laboratory’s Inertial Fusion Energy Institutional Initiative. Credit: DOE View the video.

CHASING HISTORY

Reaching ignition crowned six decades of research and development of the world’s highest-energy lasers at LLNL, all working toward the goal of creating in the laboratory the temperatures and pressures found only in the center of stars and giant planets and in exploding nuclear weapons.

And it fulfilled the vision of the Laboratory’s fusion pioneers, such as former LLNL Director John Nuckolls, who first proposed using lasers to create the power of the stars in a laboratory; John Emmett, the first leader of the Laboratory’s consolidated laser programs; and former NIF Chief Scientist John Lindl, who literally wrote the book on the physics of indirect-drive ICF in 1998.

Lindl, who joined the ICF program in 1972 and became the leader of the Laser Target Design Group in 1978, presented the original proposal for NIF to the National Academy of Science in 1989. He said the academy gave the project only a 50-50 chance of achieving ignition.

“I would say that, by far, the majority of the scientific community was very skeptical, if not downright dismissive, of the likelihood that we would succeed,” Lindl said. “But there have been enough people who believed we could do it and sustained the support for what we’ve been doing that got us to this point.

“Fortunately, we were on the positive side of the 50-50 proposition.”

SOLVING PROBLEMS

To get to ignition, NIF researchers confronted and overcame a wide variety of issues: implosion asymmetries and hydrodynamic instabilities, fuel contamination by material from the target capsule, radiative losses, laser backscatter and perturbations caused by the ultra-thin “tents” holding the capsule inside the hohlraum and the tiny tubes used to fill the capsule with fuel.

The researchers met in an auditorium almost every week to review the results and implications of the previous week’s experiments — doing their best to tease out the subtle nuances of one of history’s toughest scientific quests.

They adjusted the energy and timing of the laser pulses, experimented with new target designs and materials, found ways to couple more laser energy to the target to boost the hot-spot pressure and temperature and made NIF’s optics more resistant to laser damage.

Nino Landen, the ICF Experiments Program group leader, noted that the road to ignition also represents “the culmination of developing and refining state-of-the-art diagnostics and active probe techniques over several decades by hundreds of scientists, engineers and technicians” at NIF’s predecessor, the Nova Laser at LLNL, the Omega Laser Facility at the University of Rochester and NIF.

“These allowed us to measure and understand hohlraum and capsule conditions and sensitivities, and ultimately adjust the input laser and target parameters for optimizing implosion performance,” Landen said. “The experimental developments led notably over decades by Mike Campbell (former Laser Programs associate director) and Joe Kilkenny (former ICF Program leader and current chief systems engineer for Measurement Systems) to advance ICF have also proved useful for a broader set of high energy density science experiments.”

The researchers knew they were on the threshold of ignition when an Aug. 8, 2021, experiment produced 1.35 megajoules (MJ) of energy, about 70% of the 1.92 MJ of laser energy absorbed by the target. That experiment incorporated several design changes that boosted the energy reaching the fuel.

Among the many researchers who contributed to NIF’s groundbreaking ignition experiment were (from left) Omar Hurricane, Nino Landen, Michael Stadermann, John Lindl, Joe Kilkenny, Doug Larson, and Dave Schlossberg. Credit: Jason Laurea

The resulting fusion reactions propelled almost 500 quadrillion energetic alpha particles (helium nuclei) into the cold fuel surrounding the hot spot, igniting a self-sustaining “burn wave” of additional reactions that consumed about 2% of the fuel.

The Aug. 8 result, as well as NIF shots in 2020 and 2021 that produced a burning plasma for the first time, “showed an existence proof that ignition was possible,” said CF Chief Scientist Omar Hurricane. “We knew we were moving in the direction where things should start working better.

“The last 10 years have been tough; we were counted out so many times,” he added. “But it also has been steady progress to get to this point; 10 years is a relatively short time for such a hard scientific challenge.”

CROSSING THE THRESHOLD

The Dec. 5 ignition shot was the second in a modified experimental campaign, called “Hybrid-E High Energy” (HyeHE), that built on earlier hybrid designs but included design improvements for higher fusion energy output: about 8% more laser energy (2.05 MJ), a longer pulse, and a thicker (by 6 microns) target capsule (a micron is one-millionth of a meter).

The higher-energy shot was enabled in part by implementing several technologies to protect NIF’s optics from damage. They included the installation of 80 additional high-quality fused silica debris shields, for a total of 128 of NIF’s 192 beamlines, to protect the final optics from debris generated by less-durable disposable shields.

The HyeHE campaign’s goal was to overcome variations that had stymied several earlier efforts to replicate the 2021 results, such as implosion asymmetries and fuel contamination by capsule material, that were linked to microscopic defects in the capsules.

“The whole point behind this new design change — higher energy and a thicker ablator — was to have more margin against needing to have a very pristine capsule,” Kritcher explained. “The thicker capsule also lets us burn up more of the DT fusion fuel.”

BUILDING ON UNDERSTANDING

Illustration of a NIF target showing the inner and outer cone beams impacting the interior wall of the hohlraum.

The first shot in the new campaign, on Sept. 19, produced about 1.2 MJ of energy, falling just short of the 2021 result primarily because the implosion was driven oblate, leading to a pancake-shaped hot spot that wasted some of the additional laser energy.

To improve symmetry for the December shot, the researchers adjusted the balance of energy among the laser beams, both at the start and in the main part of the pulse. At the peak of the pulse, this was achieved by wavelength tuning — slightly changing the wavelength of one or more sets of beams to control the exchange of energy as the beams crossed in the laser entrance holes.

This rebalancing of the laser energy helped equalize the X-ray drive so energy was evenly distributed throughout the hohlraum, producing a more symmetric implosion that burned about 4% of the fuel and resulted in ignition .

Significantly, the ignition experiment used a target capsule with many more surface and subsurface defects and high-Z (high atomic number) “inclusions” than the 2021 experiment that moved NIF to the threshold of ignition.

The new design was shared with LLNL’s cognitive simulation team, and they concluded that “we had a greater than 50% probability of achieving the National Academy of Science’s definition of ignition,” said LLNL design physicist Kelli Humbird. “This was the first time we’ve attempted this kind of prediction, and our current data-driven model indicated there was a substantially higher chance of achieving ignition with this design when compared to the Aug. 8 design.”

Target Fabrication Program Manager Michael Stadermann said the fact that the capsule was flawed was very encouraging for the team. “This gives us confidence that we can make shells of equal quality or even better quality in the future — that we’ll be able to reproduce this experiment or even improve on it,” he said.

WHY PURSUE IGNITION?

Accessing the energies of fusion ignition will enable stockpile stewardship experiments at a new level of high energy density conditions. Ignition also will help weapons scientists test and refine the computer models they use to better understand and assess the performance of the stockpile’s aging nuclear weapons.

“Fusion ignition is a key process in our thermonuclear weapons,” said Mark Herrmann, LLNL’s program director for weapons physics and design. “The very extreme environments created when the fusion plasma ignites enables testing that ensures that we can maintain and modernize our nuclear deterrent.”

Added Budil: “Our leadership in science and technology helps to build strong relationships with our allies and partners and to demonstrate our capabilities to our adversaries.”

Ignition experiments also will help assess the survivability of nuclear weapon components and other weapon-relevant materials important to national security.

The Dec. 5 shot was the first experiment “where we put the ignition platform to work for stewardship,” said now-retired NIF Director Doug Larson. The experiment fired a blast of neutron radiation on depleted uranium samples and test objects, a step toward eventually conducting enriched uranium and plutonium survivability experiments.

“Nobody else can do that,” Larson said. “Nobody else has an intense pulsed source of 14 MeV (14 million electron-volt) neutrons to assess stockpile survivability questions. Right now it’s (about) survivability, but as we attain even higher yield, it’ll broaden to other (stewardship) applications.”

The cryo X-ray Neutron Blast Snout (XNBS) used in the first high energy density neutron survivability test on Dec. 5.

The data and insights from ignition experiments also will help evolve inertial fusion energy, or IFE, as a viable technology for future power plants.

Achieving ignition “demonstrates the basic scientific feasibility” of IFE, said Tammy Ma, lead for LLNL’s Institutional Initiative in Inertial Fusion Energy.

“Developing an economically attractive approach to fusion energy is a grand scientific and engineering challenge,” she said. “Without a doubt, it will be a monumental undertaking. However, the potential benefits are enormous: clean, carbon-free, abundant, reliable energy capable of meeting the world’s energy demands, and furthermore, providing for the energy sovereignty and energy security of the U.S.”

THE PATH FORWARD

Having blazed the path to ignition, ICF researchers and their collaborators are now making plans for sustained, and even higher, yields to enable new stockpile stewardship and basic science applications at NIF.

“To quote Winston Churchill,” said NIF Director Gordon Brunton. “‘Now is not the end. It is not even the beginning of the end. But it is, perhaps, the end of the beginning.’

“With more than 20 years invested in getting NIF to the starting block, we must prioritize restoring the workforce and facility to sustainably continue to maximize the recent outstanding results for the Stockpile Stewardship Program.

“Beyond the near-term sustainment of NIF,” he said, “our modest plans for further upgrades will extend our worldwide leadership in high energy density physics and keep NIF as a flagship scientific capability of the nation for decades to come.”

As a step toward this vision, experiments planned for later this year will use a new set of target capsules carefully manufactured to reduce the defects that limited the performance of earlier shots.

In addition, said Jean-Michel Di Nicola, chief engineer for NIF laser systems, operators intend to boost the laser’s power by another 8% this summer, providing more margin for ignition. “In the future, with a (facility) sustainment and upgrade investment,” he said, “the NIF laser could produce even higher energies and power and promise larger target gains.”

Researchers believe the laser upgrades and additional optics improvements could enable NIF to reach 2.2 MJ of energy and 480 trillion watts of peak power in the coming year and potentially as much as 2.6 to 3 MJ later this decade.

“Little changes can make a big difference” in the outcome of an experiment — both positive and negative, Herrmann noted. He said NIF’s goal moving forward is to control the “inherent variabilities” in fusion implosions and attempt to consistently produce results in the megajoule range.

“Ignition is a first step,” said Budil, “a truly monumental one that sets the stage for a transformational decade in high energy density science and fusion research, and I cannot wait to see where it takes us.”

Along with the LLNL participants, the researchers credited the experiment’s success to collaborators from Los Alamos and Sandia national laboratories, the Nevada National Security Site, General Atomics, Diamond Materials, the Laboratory for Laser Energetics at the University of Rochester, the academic community including the Massachusetts Institute of Technology, the University of California, Berkeley and Princeton University and international partners including the United Kingdom’s Atomic Weapons Establishment and the French Alternative Energies and Atomic Energy Commission.

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On Critical Research Needs for Inertial Fusion Energy

Daniel L. Jassby, Retired from Princeton Plasma Physics Lab., dljenterp@aol.com

Inspired by the August 8, 2021 “supershot” at the NIF (National Ignition Facility) that reached the threshold of thermonuclear ignition [1], practitioners in the field of ICF (Inertial Confinement Fusion) held several conferences and workshops to discuss future R&D activities. Their focus was on the research needs for IFE (Inertial Fusion Energy), a term that commonly refers to the application of ICF micro-explosions for power production. The most extensive set of analyses are contained in the USDOE-sponsored Report of the IFE Basic Research Needs Workshop. The recommendations of this report were summarized by Ma and Betti in the April 2023 Newsletter [2]. 

The Ma-Betti summary features lists of recommended “research opportunities” that only bureaucrats could love. No doubt experts on ICF will understand the tasks addressed in this compilation, but the typical devotee of this Forum will turn away befuddled. Those of us who are not experts on ICF or on the optimization of bureaucratic arrangements will recognize nevertheless that, while there are a hundred technological challenges that must be overcome for IFE, there are actually just two critical objectives that should be pursued immediately. The first objective is a determination of whether direct drive of fusion fuel capsules can achieve ignition, and the second is the development of a practical fusion driver.

INDIRECT VS DIRECT DRIVE

In the process of indirect drive,” a suitable energy source is first converted to X-rays, which are guided to implode the fusion fuel capsule. Indirect drive with X-ray implosion of the fusion fuel is the only technique that to date has proved capable of igniting thermonuclear burn, whether the energy source is a multi-terrajoule fission explosion [3] or megajoule laser beams [4]. In the process of direct drive,” the laser beams themselves are directed upon the spherical fusion fuel capsule.

For IFE indirect drive has two disadvantages: 1) conversion of the laser or ion beam energy to X-rays that are usefully employed for fuel implosion is only about 20% efficient, and 2) the targets are much more complicated and expensive as the fuel capsule must be enclosed in a disposable hohlraum that converts the laser or ion beams to X-rays.

But direct drive has 3 disadvantages that may prove decisive:

  1. Laser light is a vector field thats difficult to focus symmetrically around a spherical target, whereas hohlraum-generated X-rays produce a scalar field that can symmetrically compress a sphere.
  2. The much shorter wavelength of X-rays compared with the approximately 0.3-micron laser wavelength allows a more uniform irradiation of the fuel capsule.
  3. Instabilities at the capsule surface excited by irradiation are easier to control at the wavelengths of X-rays compared with the much longer laser wavelength and its narrow bandwidth [5].

These problems can in principle be mitigated with so-called “shock ignition,” which uses one laser pulse mainly for compressing the fuel capsule and a second ultra-short pulse to ignite the compressed fuel [6].

OBJECTIVE A. PROVE THAT DIRECT DRIVE CAN ACHIEVE IGNITION

The proponents of direct drive, who are a large majority of IFE enthusiasts as well as the fusion startups in the field [7], declare that indirect drive will never be practical for a power plant. If that is the case, then it behooves those proponents to demonstrate that direct drive can produce ignition and a propagating burn, as the NIF has already demonstrated with indirect drive [4]. The fact that the NIF experiments have shown that ignition of fusion fuel is feasible increases the plausibility of direct drive, but the latter is far from guaranteed. The success of direct drive may depend on the viability of the shock ignition technique [6], among other factors.

What is the state of the art? The NIF has produced no more than 35 kJ of fusion with direct drive at 1 MJ laser energy, for a fusion energy gain Q of 3.5% [8]. That’s not much larger than the Q = 2% achieved at the U. of Rochester’s OMEGA facility with only 40 kJ of laser energy. Nobody else has lately done anything worth mentioning in this regard.

Considering that 10 years ago the NIF had generated only tens of kilojoules of fusion in pulses with indirect drive, perhaps a concerted campaign on the NIF could approach and eventually achieve ignition with direct drive. But the NIF project seems uninterested in making such an attempt. There are several other large laser-fusion facilities in France, China and Russia, but to date they have not produced significant results of any type despite grandiose plans. Unlike the magnetic fusion scene, serious ICF/IFE development appears to be a peculiarly US enterprise.

Consequently, a new megajoule-level beam system must be implemented in the US, and that should include developing a driver that’s suitable for future IFE applications. 

OBJECTIVE B. DEVELOP A PRACTICAL FUSION DRIVER

The neodymium-glass laser system used in the NIF has an electrical efficiency of about 0.5% and can fire a full-energy pulse only once or twice each day. A practical implosion driver must have an overall electrical efficiency of at least 10% and be capable of firing several times per second. (The latter requirement would be relaxed by orders of magnitude for a research facility because of the time needed for experimental target setup.) Viable candidates include argon fluoride (0.19 μm) and krypton fluoride (0.25 μm) excimer gas lasers, diode-pumped solid-state lasers (DPSSL, 0.35 μm), heavy-ion beams, light-ion beams, and relativistic electron beams. 

Proposed ion-beam drivers can be produced with high electrical efficiency and pulse rate. It is doubtful that ion beams can be adequately focused on a minuscule fuel pellet, but they can be focused on the exterior of a much larger hohlraum, so that indirect drive is essential.

At least half a dozen private companies claim that they will put IFE-based power on the grid in the 2030’s using laser drivers [7]. There is zero chance that any of them will power the grid on any time scale, but perhaps their R&D will eventually result in at least one practical fusion driver, thus satisfying the second objective. The candidate drivers that are presently most advanced include the krypton fluoride excimer laser [9], which has operated at the multi-kilojoule level and at high repetition rate, and the commercially available DPSSL [10] with somewhat lower energy output. The ArF excimer laser [11] is more desirable principally because of its shorter wavelength, and its development benefits from extensive experience with KrF lasers.

OUTLOOK

It’s interesting that laser fusion with direct drive giving Q up to 0.03 has achieved essentially the same status as magnetic confinement fusion, as far as proximity to ignition is concerned. The highest thermonuclear Q realized with tokamaks in disruption-free operation has been 0.2 to 0.3, which is a factor of 20 below a “burning plasma” and a factor of 40 below an essentially ignited plasma [12]. Ignition of the core plasma in a laser-compressed fuel capsule occurs when overall Q is somewhat less than 1, or a factor of at most 30 above the present best result on the NIF with direct drive.

Both the promoters of laser direct drive and of tokamak fusion devices are confidently designing so-called fusion pilot plants for electricity production when neither technique has come anywhere close to demonstrating useful scientific feasibility, viz. the attainment of thermonuclear ignition. In each case a test of feasibility is 10 to 15 years away and the outcome is highly uncertain.

Given adequate funding, it will take nearly a decade to develop and deploy an efficient, high-pulse-rate megajoule-level driver and 5 more years to carry out a program attempting ignition with direct drive. If that cannot be demonstrated, then IFE development programs must necessarily proceed with already proven indirect drive and concentrate on the economic manufacture, means of rapid emplacement, and optimal illumination of hohlraum targets.

REFERENCES

[1]. Daniel Clery, “With explosive new result, laser-powered fusion effort nears ignition,” Science, Aug. 17, 2021 (online).

[2] Tammy Ma and Riccardo Betti, “Inertial Fusion Energy Basic Research Needs Summary,” APS Forum on Physics and Society, Vol. 52, No. 2 (April 2023), p. 12 (online).

[3] First demonstrated in the Ivy Mike shot of November 1952. See Wikipedia “Ivy Mike”.

[4] Daniel Clery, “Explosion marks laser fusion breakthrough,” Science, Vol. 378 (Dec. 2022), p. 1154.

[5] John Lindl, Development of the indirect-drive approach to ICF,” Physics of Plasmas 2 (1995), p. 3933.

[6] R. Betti and O. A. Hurricane, “Inertial Confinement Fusion with Lasers,” Nature Physics 12 (2016), p. 435.

[7] David Kramer, “NIF success gives laser fusion energy a shot in the arm,” Physics Today 76 (2023), p. 25. 

[8] E. M. Campbell, et al., “Direct-drive laser fusion: status, plans and future,” Phil. Trans. R. Soc. A, 379: 2021 Jan. 25.

[9] Stephen Obenschain, et al., High-energy krypton fluoride lasers,” Applied Optics, Vol. 54 (2015), F103.

[10] A. Bayramian, et al., Compact, efficient laser systems required for laser IFE,” Fusion Sci. & Tech. 60 (2011), p. 28.

[11] S. P. Obenschain, et al., “Direct drive with the argon fluoride laser,” Phil. Trans. R. Soc. A 378 (2020,) p. 31.

[12] Daniel Jassby, “The Quest for Fusion Energy,” Inference 7,no. 1 (2022), doi:10.37282/991819.22.30

 

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Science Policy Still Needs Scientists

Jacob M. Robertson, Science Policy Senior Manager, Federation of American Scientists, jrobertson@fas.org

The physics community has long discussed how to best use science for the benefit of humanity. Harnessing the nuclear chain reaction was a major entry point for physicists to influence politics and policy, as the incredible potential for destruction could not be ignored. A group of Manhattan Project scientists led by James Franck wrote, “We feel compelled to take a more active stand now because the success [in nuclear science] is fraught with infinitely greater dangers than were all the inventions of the past.”1 Among several other efforts in the United States, what is known today as the Federation of American Scientists (FAS) emerged in 1945 as a collective of atomic scientists who desired a voice in Washington on nuclear weapons issues. As society continues to face nuclear proliferation concerns alongside increasingly urgent issues such as climate change, FAS remains an impactful avenue for scientists to shape policy.

Since its founding, FAS and physicists at large achieved some successes, but also faced failures in their attempts to influence policy-making. An early example is the creation of the civilian-controlled Atomic Energy Commission (AEC) in 1946, which was initially celebrated.2 It soon became clear the AEC did not have the proper structure or direction to reduce the threat of nuclear warfare. FAS was almost disbanded after this setback because scientists realized the challenge of performing scientific research while still leaving time for effective political activism.3 A 1980s article in the New York Times explained the changes at the organization—the “grand old men” who built the atomic bombs were being replaced by a small team of full-time professional staff and lobbyists.4 But scientists could not retreat entirely to their labs; they had to collaborate with policy experts who could provide training and resources to make their advocacy more efficient.

Almost 40 years later, FAS employs more than 40 professionals who aim to ensure that science and technology help address the most pressing challenges of our time. The organization embraces the concept of policy entrepreneurship as a method to incorporate the voices of individual scientists into policy development and advocacy. In addition to the power of interest groups and other coalitions, it is becoming more apparent that individuals possessing relevant attributes and skills can also significantly influence policy.5 Physicists who care deeply about social issues and the potential uses of their work should consider assuming the role of a ‘policy entrepreneur’.

The concept of a policy entrepreneur was first popularized in John Kingdon’s 1984 book, Agendas, Alternatives, and Public Policies, as people in any role or occupation who invest their time, energy, and reputation to influence policy.6 Scholars have characterized the attributes, skills, and strategies of effective policy entrepreneurs. Ambition, credibility, and sociability are critical to gaining and using influence in any social environment.7 More specifically, an effective policy entrepreneur knows the strength and limitations of different policy interventions, such as legislation, executive orders, public comment, and federal committees, and thoughtfully proposes the intervention most appropriate for their goal.8 A policy entrepreneur has their own agenda, engages with relevant stakeholders, and enables others to achieve specific outcomes. Society would benefit from more physicists acting as policy entrepreneurs to promote agendas such as commercializing fusion energy generation, advancing carbon removal technologies, and preparing the electric grid for a clean energy future.

FAS finds motivated experts across several science and technology disciplines, helps develop their skills as policy entrepreneurs, and advises them on strategies and tactics for achieving policy goals. If you are curious about becoming a policy entrepreneur, one way to get started is by writing a policy memo with us. In academia, publications are the outcome at the end of a research process; however, in advocacy, writing a policy memo is often the first step. Policy memos are short, prescriptive documents with specific and actionable recommendations to address a well-defined problem. The structured process of writing such memos helps scientists learn to approach an issue as policy entrepreneurs. The final product is a tool to communicate directly with policymakers—a means to start the conversation with government officials that there is a problem and the writer knows how to fix it. Not every physicist needs to be a policy entrepreneur, but please contact us if you are compelled to take a more active stance.

REFERENCES

1 Franck, J., Hughes, D., Szilard, L., Hogness, T., Rabinowitch, E., Seaborg, G., & Nickson, C. J. (n.d.). The Franck Report. The Franck report: A report to the secretary of war, June 1945. https://sgp.fas.org/eprint/franck.html 

2 Federation of American Scientists. Linus Pauling and the International Peace Movement. (n.d.). https://scarc.library.oregonstate.edu/coll/pauling/peace/narrative/page6.html

3 Gottfried, K. (1999). Physicists in politics. Physics Today, 52(3), 42–48. https://doi.org/10.1063/1.882612 

4 Boffey, P. M. (1985, September 4). On scientists as lobbyists. The New York Times, pp. 7. Retrieved June 7, 2023, from https://www.nytimes.com/1985/09/04/us/on-scientists-as-lobbyists.html.

5 Vallett, J. D. (2020). The diffusion of Erin’s law: Examining the role of the policy entrepreneur. Policy Studies Journal, 49(2), 381–407. https://doi.org/10.1111/psj.12396 

6 Kingdon J. W. (1984): 122. Agendas alternatives and public policies. Little Brown.

7 Mintrom, M. (2019). So you want to be a policy entrepreneur? Policy Design and Practice, 2(4), 307–323. https://doi.org/10.1080/25741292.2019.1675989 

8 Kalil, T. (2017). Policy entrepreneurship at the White House. Innovations: Technology, Governance, Globalization, 11(3–4), 4–21. https://doi.org/10.1162/inov_a_00253 

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Reviews

The Leak: Politics, Activists, and Loss of Trust at Brookhaven National Laboratory

Robert P. Crease with Peter D. Bond, The MIT Press. 2022, 307 pages, ISBN 978-0-262-04718-0, $29.95

This is a book about the consequences of a small tritium leak that came from the High Flux Beam Reactor (HFBR) at Brookhaven National Lab (BNL) located on Long Island, N.Y. Tritium is a radioactive isotope of hydrogen that was produced in the HFBR when neutrons from the fission process were occasionally captured by the heavy water (D2O) used as a moderator. The leak of this tritiated water was within the boundaries of the Brookhaven National Lab at the time of its discovery. This book is a narrative of the events that transpired starting with the discovery of the leak on January 8, 1997 to the eventual closure of the reactor on November 15, 1999. Robert P. Crease is a professor of philosophy at Stoney Brook University which is located close to BNL. Stoney Brook is one of the two members of Brookhaven Science Associates which was chosen to operate the lab in 1998. Crease has written several books on the history of science including a book on the history of BNL from 1946 to 1972. Bonds is a retired physicist who worked at BNL for 43 years and served as its interim director for several months from the latter part of 1997 into 1998. 

This book chronicles in a very engaging manner the response from the public, the local U.S. senator and Congressman, the government agencies in charge of BNL, the press both local and national, activist groups, existing and newly formed, and the lab itself to the announcement of the leak. It starts with a description of the history of the lab from 1948, including the understanding that BNL is located above the groundwater basin that connects to many household water wells outside the lab, the initial efforts to establish good relations with the community – which deteriorated somewhat with time – and perhaps most importantly repeating a statement by Bernard Manowitz, a BNL lab environmental scientist, that Radioactive pollution does not have to be injurious to health to be socially undesirable – a statement that summarizes a central theme of this book. 

The book goes on to describe the initial discovery of the tritium leak, its magnitude, and efforts to carefully measure it. The tritiated water was coming from the spent fuel rod cooling pool of the HFBR. This pool was leaking at a very slow rate - too slow to have been noticed within the precision of the routine monitoring regimen. The pool was constructed of thick concrete and did not have a leakproof liner. The concern was that the tritiated water that had leaked into the ground water under the lab might eventually get outside of the boundaries of the lab and into the drinking water of the surrounding community.

Since the amount of tritium released was quite small, was contained within the boundaries of the lab and the ground water beneath the lab generally met the standards for safe drinking water, immediate remediation of the problem was initially considered unnecessary. At the time of the discovery of the leak the reactor had been shut down for maintenance and it was kept offline while new monitoring wells were dug to more precisely determine the magnitude and extent of the leak. Subsequently the spent fuel rods were removed from the leaking pool and plans were developed to add a liner to the pool and then restart the HFBR. The lack of the initial sense of urgency by BNL led to its further distrust by the community. 

The HFBR was a very valuable source of neutron beams used in many areas of science research. Much productive research depended on it and every competent scientific study showed that the tritium leak presented no tangible health risk to anyone inside or outside of the lab. Adding to the problem was the fact that in recent years the community around BNL had become very concerned about plans to operate a large nuclear power plant nearby and had been successful in preventing this almost completed facility from starting up. The laboratory and state and local health and safety organizations were unable to convince critical politicians and some influential activist groups that there really was no health risk from the leak and that the lab had effective plans to allow the HFBR to be safely restarted. Articles in local newspapers and some national papers often misinformed and exaggerated the risks posed by the leak. In fact, it eventually became apparent that some believed that the leak was such a large threat to the health of the surrounding community that the entire lab should be shutdown. Thus, the conflict between the perceptions of the surrounding community of the health hazard posed by the HFBR and the high scientific value of the HFBR became very difficult to resolve.

A particularly valuable part of this book is its detailed and engrossing description of how the internal lab management, the Associated Universities Inc. (AUI), which was the external organization responsible for running the lab when the leak was discovered, and the Department of Energy (DOE) attempted to cope with this very tricky problem. We learn about DOE’s safety review process and that during the course of events the DOE forced a change of management of the lab. We are told about the arcane machinations of the DOE as it ran a hurried up process to award a valuable contract to a new management group after it had fired AUI before its contract had expired.

The fact that one of the 2 N.Y. U.S. senators and a local congressman were not consistently supportive of the lab made the political climate harsh. Ernie Moniz, a theoretical nuclear physicist who in later years was Secretary of DOE, is quoted as saying “When you are a politician, and you are seeing Congress pushing back, and you are seeing Long Island pushing back, you know it’s going to be a hard slog. If you want to reopen it [the HFBR], maybe you’ll get there, but it’s a hard, hard slog. When it comes to being able to start a major facility, and your own Congressman is arguing against it, you haven’t done your job.” Ultimately Bill Richardson who became Secretary of DOE in April, 1998 and was influenced in part by a group formed by two prominent celebrities, decided to shut down the HFBR. This book well describes how the very tricky, perhaps even intractable, problem of the tritium leak was dealt with. I wish more had been included directly from the viewpoint of the people, community groups, highly visible celebrities, and politicians that ultimately opposed the restart of the HFBR, but that aside I certainly recommend this valuable book. 

Martin Epstein

California State University, Los Angeles 

epstein@calstatela.edu


Invisible Women: Exposing Data Bias in a World Designed for Men

Invisible Women: Exposing Data Bias in a World Designed for Men by Caroline Criado Perez, is a must read for anyone doing data science, artificial Intelligence, or policy work, and a should read for just about everyone else. Caroline Criado Perez, a journalist and feminist author, has undertaken multiple campaigns in the United Kingdom to make women more “visible,” including a campaign for women on government-issued banknotes, more statues of women of note, and awareness about pervasive harassment of women on social media. Her book, takes a look into all the ways our culture does not account for women in decision-making owing to a lack of data about women. She proposes that if we spent more time collecting and disaggregating data by sex, we would have better social and living outcomes for women across the planet. Criado Perez argues that women are invisible by default as culture dictates males as primary and women as other as a matter of course. Things are always designed for men, unless otherwise noted. 

Criado Perez starts out with some simple case study examples of what she means by a lack of data on women, or women being invisible in the data. The first example is about snow-clearing in northern Europe and how it was initially focused on roadways used by commuters in cities without considering all the women in these cities who did not commute. Many of these were women in care-taking roles who needed walking paths and local streets cleared. Since the commuters were mainly male, the policy makers had not considered anyone else. When pressed to consider women, the sidewalks and walkways were cleared first, and this brought down the large number of hospital visits by women and the elderly owing to slips and falls on the icy walkways, thus saving cities large amounts of money. She additionally looks at the inequity in toilets, where women often face long lines owing to the differing toileting needs of women versus men. The author posits that when women are actually considered, or data is collected about women and then used in decision making, solutions can be created to address the gap in services. She notes rare examples like the snow clearing where women were considered in the plan, while lamenting that despite the data, the toileting issue remains largely unsolved. Much of what Criado Perez presents is a wide-ranging case for considering and collecting data on women and using the data for decision making. She points out that inclusion of women and their data makes sense from an economic, social and cultural perspective and creates a better society for everyone overall. 

The rest of the book goes through sections including Daily Life, The Workplace, Design, Going to the Doctor, Public Life, When it Goes Wrong, where she lays out all the ways in which a lack of data fails women. Criado Perez is careful to not be alienating in these discussions, pointing out that is not purposeful that women are excluded, it is just part of a larger culture where women are not even considered. The point here is that we need to be more mindful of data and understand that much of the design for the daily workings of the world have not considered the needs of anyone other than men. 

While this book focuses primarily on women and the lack of data for women, one could easily interest any “other” – persons of color, the elderly, persons with differing abilities, persons who represent as other than male. This book is a lesson to all of us to be more mindful in the work that we do, and to take time to consider that there are other persons in the world who must be considered. I highly recommend this book to all those in STEM, it will help you consider new ways of thinking about data, and the role culture plays in deciding the importance for use of data.

Nancy Ruzycki

University of Florida

nruzycki@ufl.edu

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