On December 5, 2022, an indirect drive fusion implosion on the National Ignition Facility (NIF) achieved a target gain G_{target} of 1.5. This is the first laboratory demonstration of exceeding "scientific breakeven" (or G_{target}>1) where 2.05 MJ of 351 nm laser light produced 3.1 MJ of total fusion yield, a result which significantly exceeds the Lawson criterion for fusion ignition as reported in a previous NIF implosion [H. Abu-Shawareb et al. (Indirect Drive ICF Collaboration), Phys. Rev. Lett. 129, 075001 (2022)PRLTAO0031-900710.1103/PhysRevLett.129.075001]. This achievement is the culmination of more than five decades of research and gives proof that laboratory fusion, based on fundamental physics principles, is possible. This Letter reports on the target, laser, design, and experimental advancements that led to this result.

Fermilab initiated the accelerator magnet system upgrade project PIP-II for future neutrino experiments. Old ORBUMP pulsed dipoles should be replaced with new, stronger magnets occupying the same space as old ones. Four of these magnets connected in series form dogleg type of proton beam orbit. The magnet field and 19 kA current pulse length are close to 1 ms. Old magnet cores were based on a ferrite material. A magnet gap field above 0.4 T for new magnets completely saturates ferrite material. So, for the magnet core, 0.127 mm thick laminations of low carbon steel with inorganic coating were placed in a vacuum box. Transient magnet parameters were investigated, including the skin effect in the iron core and the single-turn copper coil. The copper coil shimming improved the integrated field homogeneity. Simulated by OPERA3D, power losses were used for the thermal analysis by ANSYS code. The magnet performance is strongly coupled with the power source. The pulsed power source design included the dynamic magnet inductance and resistance. The paper presented the ORBUMP magnet system design.

The Spallation Neutron Source (SNS) at ORNL currently is being upgraded from 1.0 GeV to 1.3 GeV. Several water-cooled magnets should be upgraded to transport 30% of higher beam energy. New chicane, injection/extraction septum, and Lambertson magnets were designed. Designing the magnets was a challenging task because the new magnets required good combined integrated field quality and needed to occupy the old magnets space but with about 20% greater integrated magnetic field. Additional strong requirements applied to the magnets fringe field do not disturb the circulating beam. The special field profiles had to be provided in foil areas between magnets. The analysis described here was based on OPERA3D simulations. A special technique was used for analyzing the integrated field harmonics. Initially, the particle track was simulated, and integrated field components were calculated along this track for the reference radius, which were used for the harmonics analysis. In addition, 3D field maps were provided for beam optics simulations. The final beamline analysis confirmed good beam transmission and low losses.

Executive Summary – The proposed work is focused on developing advanced designs for inertial fusion energy (IFE) applications. The innovative approach is based on three key elements: (1) new broadband and deep UV laser technologies to mitigate deleterious effects of laser-plasma interaction; (2) high-gain (G > 100) laser direct-drive (LDD) designs with enhanced laser coupling and mitigated imprint at moderate laser energies (EL ~ 1 MJ); and (3) simplicity and low-cost of targets [relative to nominal deuterium−tritium (DT) layered inertial confinement fusion (ICF) targets] using foam shells filled with liquid DT; to the best of knowledge, these designs offer the only target solutions where the cost is consistent with the IFE mass production requirements.

For more than half a century, researchers around the world have been engaged in attempts to achieve fusion ignition as a proof of principle of various fusion concepts. As recently reported, a burning plasma state, where the alpha-heating in the plasma is the primary source of heating, was achieved in laboratory experiments. Following the Lawson criterion, an ignited plasma is one where the fusion heating power is high enough to overcome all the physical processes that cool the fusion plasma, creating a positive thermodynamic feedback loop with rapidly increasing temperature. In inertially confined fusion, ignition is a state where the fusion plasma can begin ``burn propagation'' into surrounding cold fuel, enabling the possibility of high energy gain. While ``scientific breakeven'' (i.e. unity target gain) has not yet been achieved, this talk reports the first controlled fusion experiment on the National Ignition Facility to produce capsule gain greater than unity (here 5.8) and reach ignition by many different formulations of the Lawson criterion. In the talk, we will discuss some key basic physics inertial confinement fusion (ICF) principles behind the burning plasma and ignition results as well as discuss future challenges.

This paper describes the hardware and operations of the Neutrinos at the Main Injector (NuMI) beam at Fermilab. It elaborates on the design considerations for the beam as a whole and for individual elements. The most important design details of individual components are described. Beam monitoring systems and procedures, including the tuning and alignment of the beam and NuMI long-term performance, are also discussed.

An upgrade of the Advanced Photon Source is being planned at Argonne National Laboratory (ANL). The main goal of the upgrade is to improve the storage ring performance based on more advanced optics. One of the key magnet system elements is bending dipole magnets having a field strength change along the electron beam path. A prototype of one such longitudinal gradient dipole magnet has been designed, built, and measured in a collaborative effort of ANL and Fermilab. This paper discusses various magnetic design options, the selected magnet design, and the fabrication technology. The prototype magnet has been measured by rotational coils, a stretched wire, and a Hall probe. Measurement results are discussed and compared with simulations.

The magnets of the circular accelerators that comprise the Fermilab complex have contributed to, responded to, and solved a string of accelerator physics issues. Most importantly, the magnets are supposed to generate high quality magnetic fields needed for stable long-term dynamics of the particles circulating in the rings. The quality of the transverse magnetic field B is given by the multipole coefficients in the expansion: 3.1 $$ {B}_x+i\cdot {B}_y={B}_0{\displaystyle \sum_{n=0}\left({b}_n+i{a}_n\right){\left[\frac{x+ iy}{R_0}\right]}^n}, $$ where R 0 is the reference radius (1 in. in the Fermilab accelerators), the pole number is 2(n + 1) and b n (a n ) are the normal (skew) multipole coefficients, and b 0 is unity. For example, the multipoles allowed by dipole symmetry, b 2, b 4, b 6, … are designed to be small and would be 0 for a pure cos θ coil winding. The precise coil placement, and hence good magnetic field uniformity at the relative level of the multipole coefficients of few 10−4, had the biggest effect on the accelerator performance.

Mu2e, a charged lepton flavor violation (CLFV) experiment is planned to start at Fermilab late in this decade. The proposed experiment will search for neutrinoless muon to electron conversions with unprecedented sensitivity, better than 6 x 10(-17) at 90% CL. To achieve this sensitivity the incoming proton beam must be highly suppressed during the window for detecting the muon decays. The current proposal for beam extinction is based on a collimator design with two dipoles running at 300 kHz and 5.1 MHz and synchronized to the proton bunch spacing. The appropriate choice of ferrite material for the magnet yoke is a critical step in the overall design of the dipoles and their reliable operation at such high frequencies over the life of the experiment. This choice, based on a series of the thermal and magnetic measurements of the ferrite samples, is discussed in the paper. Additionally, the first results from the testing at 300 kHz of a prototype AC dipole are presented.

During the first 20 years of operation, the Fermilab Tevatron developed strong coupling between the two transverse degrees of freedom. The required strength of the circuit of skew quadrupole magnets used to correct for coupling, though capable, had increased by an order of magnitude since 1983. Changes made to the Tevatron for colliding beams operation had altered the skew quadrupole corrector distribution and strong coupling became evident, often encumbering routine operation during the colliding beam physics run. It was discovered that the superconducting coils of the main dipole magnets had become vertically displaced relative to their yokes since their construction. The ensuing systematic skew quadrupole field introduced by this displacement accounts for the required corrector settings and observed beam behavior. The magnets were adjusted in situ over the course of several long maintenance periods and the Tevatron performance improved as a result.

A charged lepton flavor violation experiment, Mu2e, is planned at Fermilab, searching for muon to electron conversions with an unprecedented sensitivity, better than 6 × 10 -17 at 90% CL. To achieve such sensitivity the incoming beam must be highly suppressed during the window for detecting the conversion a muon into an electron. One proposal for beam extinction is based on a collimator with two dipoles running in a resonant circuit at ~300 kHz synchronized to the bunch spacing. An appropriate choice of the ferrite material for the magnet yoke is critical to ensuring the reliable operation of such a high frequency dipole over the life of the experiment. In this paper, we present the results of the thermal and magnetic measurements of the selected ferrite material, including the field non-linearity effects and power losses. Some dimensional optimization of the ferrite bricks is also discussed.

Shock ignition, a new concept for igniting thermonuclear fuel, offers the possibility for a near-term ({approx}3-4 years) test of high gain inertial confinement fusion on the National Ignition Facility at less than 1MJ drive energy and without the need for new laser hardware. In shock ignition, compressed fusion fuel is separately ignited by a strong spherically converging shock and, because capsule implosion velocities are significantly lower than those required for conventional hotpot ignition, fusion energy gains of {approx}60 may be achievable on NIF at laser drive energies around {approx}0.5MJ. Because of the simple all-DT target design, its in-flight robustness, the potential need for only 1D SSD beam smoothing, minimal early time LPI preheat, and use of present (indirect drive) laser hardware, this target may be easier to field on NIF than a conventional (polar) direct drive hotspot ignition target. Like fast ignition, shock ignition has the potential for high fusion yields at low drive energy, but requires only a single laser with less demanding timing and spatial focusing requirements. Of course, conventional symmetry and stability constraints still apply. In this paper we present initial target performance simulations, delineate the critical issues and describe the immediate-term R&D program that must be performed in order to test the potential of a high gain shock ignition target on NIF in the near term.

We are carrying out a multidisciplinary multi-institutional program to develop the scientific and technical basis for inertial fusion energy (IFE) based on laser drivers and direct-drive targets. The key components are developed as an integrated system, linking the science, technology, and final application of a 1000-MWe pure-fusion power plant. The science and technologies developed here are flexible enough to be applied to other size systems. The scientific justification for this work is a family of target designs (simulations) that show that direct drive has the potential to provide the high gains needed for a pure-fusion power plant. Two competing lasers are under development: the diode-pumped solid-state laser (DPPSL) and the electron-beam-pumped krypton fluoride (KrF) gas laser. This paper will present the current state of the art in the target designs and lasers, as well as the other IFE technologies required for energy, including final optics (grazing incidence and dielectrics), chambers, and target fabrication, injection, and tracking technologies. All of these are applicable to both laser systems and to other laser IFE-based concepts. However, in some of the higher performance target designs, the DPPSL will require more energy to reach the same yield as with the KrF laser.

The International Linear Collider reference design requires over 13000 magnets, of approximately 135 styles, which must operate with very high reliability. The Fermilab Main Injector represents a modern machine with many conventional magnet styles, each of significant quantity, that has now accumulated many hundreds of magnet-years of operation. We review here the performance of the magnets built for this machine, assess their reliability and categorize the failure modes, and discuss implications for reliability of similar magnet styles expected to be used at the ILC.

Multi-element corrector magnets are being produced at Fermilab that enable correction of orbits and tunes through the entire cycle of the Booster, not just at injection. The corrector package includes six different corrector elements - normal and skew orientations of dipole, quadrupole, and sextupole - each independently powered. The magnets have been tested during typical AC ramping cycles at 15Hz using a fixed coil system to measure the dynamic field strength and field quality. The fixed coil is comprised of an array of inductive pick-up coils around the perimeter of a cylinder which are sampled simultaneously at 100 kHz with 24-bit ADC's. The performance of the measurement system and a summary of the field results are presented and discussed.

The narrow dip observed at 1.9 GeV/c2 by the Fermilab experiment E687 in diffractive photoproduction of 3π+3π− is examined. The E687 data are refitted, a mechanism is proposed to explain why this resonance appears as a dip, and possible interpretations are dis-