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.

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.

We have developed a conceptual design of a next-generation pulsed-power accelerator that is optimized for advanced high-energy-density-physics experiments. The prime power source of the machine consists of 210 impedance-matched Marx generators (IMGs). Each IMG drives a 150-ns-long coaxial-transmission-line impedance transformer. The coaxial lines provide a minimum of 300 ns of transit-time isolation between each pair of IMGs. The lines in turn drive six radial-transmission-line impedance transformers, which transport the power generated by the IMGs to a six-level vacuum-insulator stack. The stack is connected to six conical outer magnetically insulated vacuum transmission lines (MITLs); these are joined in parallel at a 12-cm radius by a triple-post-hole vacuum convolute. The convolute sums the electrical currents at the outputs of the six outer MITLs, and delivers the combined current to a single short inner MITL. The inner MITL transmits the combined current to the accelerator's physics load. Since the accelerator would be the largest and most-powerful pulsed-power machine developed to date, we refer to it as Jupiter. The conceptual design of Jupiter is 72 m in diameter, stores 140 MJ of electrical energy, and generates 960 TW of peak electrical power at the output of the IMG system. The design delivers 2700 TW, 67 MA, and 9.2 MJ in a 110-ns pulse to a 0D magnetized-liner inertial-fusion (MagLIF) target. The principal goal of the design is to achieve high-yield thermonuclear fusion; i.e., a fusion yield that exceeds the energy initially stored by the accelerator's capacitors.

Laser probe diagnostics: shadowgraphy, interferometry, and polarimetry were used for a comprehensive characterization of ionization wave dynamics inside a glass target induced by a laser-driven, relativistic electron beam. Experiments were done using the 50-TW Leopard laser at the University of Nevada, Reno. We show that for a laser flux of ∼2 × 10(18) W/cm2 a hemispherical ionization wave propagates at c/3 for 10 ps and has a smooth electron-density distribution. The maximum free-electron density inside the glass target is ∼2 × 10(19) cm-3, which corresponds to an ionization level of ∼0.1%. Magnetic fields and electric fields do not exceed ∼15 kG and ∼1 MV/cm, respectively. The electron temperature has a hot, ringlike structure with a maximum of ∼0.7 eV. The topology of the interference phase shift shows the signature of the "fountain effect", a narrow electron beam that fans out from the propagation axis and heads back to the target surface. Two-dimensional particle-in-cell (PIC) computer simulations demonstrate radial spreading of fast electrons by self-consistent electrostatic fields driven by laser. The very low ionization observed after the laser heating pulse suggests a fast recombination on the sub-ps time scale.

The multi-frames shadowgraphy, interferometry and polarimetry diagnostics with sub-ps time resolution were used for an investigation of ionization wave dynamics inside a glass target induced by laser-driven relativistic electron beam. Experiments were done using the 50 TW Leopard laser at the UNR. For a laser flux of ∼2×1018W/cm2 a hemispherical ionization wave propagates at c/3. The maximum of the electron density inside the glass target is ∼2×1019cm−3. Magnetic and electric fields are less than ∼15 kG and ∼1 MV/cm, respectively. The electron temperature has a maximum of ∼0.5 eV. 2D interference phase shift shows the “fountain effect” of electron beam. The very low ionization inside glass target ∼0.1% suggests a fast recombination at the sub-ps time scale. 2D PIC-simulations demonstrate radial spreading of fast electrons by self-consistent electrostatic fields.

Ultrafast interferometry with sub-ps resolution has been applied for the direct measurement of an electron density induced by a laser-driven relativistic electron beam inside a solid dielectric. The topology of the interference phase shift shows the signature of the “fountain effect,” a narrow electron beam that fans out from the propagation axis and heads back to the target surface. Two-dimensional particle-in-cell (PIC) computer simulations demonstrate radial spreading of fast electrons by self-consistent electrostatic fields. The very low ionization, ∼0.1%, observed after the heating pulse suggests a fast recombination at the sub-ps time scale.

X-pinches are a source for studying radiative properties of plasmas of very small sizes, high densities and temperatures applicable to high-energy density plasmas such as dense Z-pinches. Recently, spatially resolved and spatially integrated X-ray spectral data have been accumulated during Mo and Cu X-pinch experiments on the Zebra generator. During these experiments configurations, other then the 2-wire X-pinches, such as 4-wire X-pinches and asymmetric X-pinches have been spectroscopically studied and computationally analyzed. We present here modeling of the K-shell and L-shell radiation from Cu X-pinches with two and four wires and the comparison with experimental spectra. L-shell radiation from symmetric and asymmetric Mo X-pinches with two wires and X-pinches with four wires have also been analyzed and compared. Dependence of the plasma spatial structure, temperature, and density on wire materials and load configurations are discussed.

Experimental results of studies of the 1MA X-pinch X-ray source in a wide spectral region are overviewed. Implosion dynamics and radiative properties of various X-pinches were studied by spatially and time-resolved X-ray and optical diagnostics. In particular, dynamics of spatial and temporal developments of the structure of X-ray emitting regions (1–5keV), temporal characteristics of X-ray pulses, X-ray radiation outputs and electron beam characteristics from symmetric and asymmetric Mo, Cu, and combined asymmetric Mo/W X-pinches with two or four wires were studied. The mechanisms of X-ray multiburst generation are discussed. The future applications of the high-current X-pinch as a 5–10kJ sub-keV–10keV radiation driver are considered.

Results from the first solid foil implosion on the 18-MA Z accelerator are reported. The foil implosion is compared to a 300-wire-array implosion with the same material and the same diameter, height, and total mass. Though both the foil and the array produced comparable x-ray yields, the array’s radiation burst was twice as powerful and half as long as the foil’s. These data along with x-ray backlighting images and inductance measurements suggest that the foil implosion was more unstable than the wire-array implosion.

Summary form only given, as follows. In order to estimate the radiated power that can be expected from the next-generation z-pinch driver such as ZR at 28 MA, current-scaling experiments have been conducted on the 18-MA driver Z. We report on the current scaling of single 40-mm diameter tungsten 240-wire arrays with a fixed 110-ns implosion time. The wire diameter is decreased in proportion to the load current. The load current is reduced by reducing the charge voltage on the Marx banks. On one shot firing only 3 of the 4 levels of the Z machine further reduced the load current. The radiated energy scales as the current squared as expected but the radiated power scales as the current to the 3.5 power due to increased pinch instability at lower current. As the current is reduced the rise-time of the x-ray pulse increases and at the lowest current value of 10.4 MA a shoulder appears on the leading edge of the x-ray pulse. We will report on experiments in February 2002 which will attempt to image the pinch along the axis to determine the nature of the reduced stability at lower currents.

We present a technique for experimentally measuring two-dimensional radiation temperatures in dynamic Hohlraums on Z. In principle the technique can be applied to any radiation source. Total radiated power from the source is measured by normalizing the area under an x-ray diode signal to energy yield measured by a bolometer. The radiated power as a function of time, which is just the normalized x-ray diode signal, can then be used to normalize gated microchannel plate x-ray pinhole camera images. The procedure is most accurate when the gated x-ray pinhole camera has the same filter as the x-ray diode and when the filter is transmissive near the peak of the Planckian radiation temperature being measured. We present results for two-dimensional radiation temperatures as a function of time for dynamic Hohlraum experiments on Z. In these experiments a z pinch consisting of nested tungsten wire arrays driven by the 20 MA, 100 ns Z accelerator implodes onto cylindrical foam located on axis. X-ray diodes and bolometers located along the axis measure the power radiated along the pinch axis. Pinhole-imaged time-resolved microchannel plate framing cameras located on axis measure the spatial distribution of this radiation. Results from the analysis of many shots taken on Z show that a symmetrical strongly radiating shock wave is launched in the foam. The shock wave stagnates to less than 1 mm diameter with radiation temperatures exceeding 300 eV. Applications for this source include driving inertial confinement fusion capsules within the dynamic Hohlraum and weapons physics experiments that use the dynamic Hohlraum as a radiation source.