Achievement of Target Gain Larger than Unity in an Inertial Fusion Experiment

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.

Safety and feasibility of same-day discharge after endoscopic submucosal dissection: a Western multicenter prospective cohort study

BACKGROUND AND AIMS

Recent Western studies support the safety and efficacy of endoscopic submucosal dissection (ESD) for lesions throughout the GI tract. Although admission for observation after ESD is standard in Asia, a more selective approach may optimize resource utilization. We aimed to evaluate the safety and feasibility of same-day discharge (SDD) after ESD and factors associated with admission.

METHODS

This was a post hoc analysis of a multicenter, prospective cohort of patients undergoing ESD (2016-2021). The primary end points were safety of SDD and factors associated with post-ESD admission.

RESULTS

Of 831 patients (median age, 67 years; 57% male) undergoing 831 ESDs (240 performed in the esophagus, 126 in the stomach, and 465 in the colorectum; median lesion size, 44 mm), 588 (71%) were SDD versus 243 (29%) admissions. Delayed bleeding and perforation occurred in 12 (2%) and 4 (.7%) of SDD patients, respectively; only 1 (.2%) required surgery. Of the 243 admissions, 223 (92%) were discharged after ≤24 hours of observation. Interestingly, larger lesion size (>44 mm) was not associated with higher admission rate (odds ratio [OR], .5; 95% confidence interval [CI], .3-.8; P = .001). Lesions in the upper GI tract versus colon (OR, 1.7; 95% CI, 1.1-2.6; P = .01), invasive cancer (OR, 1.9; 95% CI, 1.2-3.1; P = .01), and adverse events (OR, 2.7; 95% CI, 1.5-4.8; P = .001) were independent factors for admission. Admissions were more likely performed by endoscopists with ESD volume <50 cases (OR, 2.1; 95% CI, 1.3-3.3; P = .001) with procedure time >75 minutes (OR, 13.5; 95% CI, 8.5-21.3; P < .0001).

CONCLUSIONS

SDD after ESD can be safe and feasible. Patients with invasive cancer, lesions in the upper GI tract, longer procedure times, or procedures performed by low-volume ESD endoscopists are more likely to be admitted postprocedure. Risk stratification of patients for SDD after ESD should help optimize resource utilization and enhance ESD uptake in the West. (Clinical trial registration number: NCT02989818.).

Lawson Criterion for Ignition Exceeded in an Inertial Fusion Experiment

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. 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 (here target gain is 0.72, 1.37 MJ of fusion for 1.92 MJ of laser energy), this Letter reports the first controlled fusion experiment, using laser indirect drive, on the National Ignition Facility to produce capsule gain (here 5.8) and reach ignition by nine different formulations of the Lawson criterion.

Efficacy of Endoscopic Submucosal Dissection for Superficial Gastric Neoplasia in a Large Cohort in North America

BACKGROUND & AIMS

Endoscopic submucosal dissection (ESD) is a widely accepted treatment option for superficial gastric neoplasia in Asia, but there are few data on outcomes of gastric ESD from North America. We aimed to evaluate the safety and efficacy of gastric ESD in North America.

METHODS

We analyzed data from 347 patients who underwent gastric ESD at 25 centers, from 2010 through 2019. We collected data on patient demographics, lesion characteristics, procedure details and related adverse events, treatment outcomes, local recurrence, and vital status at the last follow up. For the 277 patients with available follow-up data, the median interval between initial ESD and last clinical or endoscopic evaluation was 364 days. The primary endpoint was the rate of en bloc and R0 resection. Secondary outcomes included curative resection, rates of adverse events and recurrence, and gastric cancer-related death.

RESULTS

Ninety patients (26%) had low-grade adenomas or dysplasia, 82 patients (24%) had high-grade dysplasia, 139 patients (40%) had early gastric cancer, and 36 patients (10%) had neuroendocrine tumors. Proportions of en bloc and R0 resection for all lesions were 92%/82%, for early gastric cancers were 94%/75%, for adenomas and low-grade dysplasia were 93%/ 92%, for high-grade dysplasia were 89%/ 87%, and for neuroendocrine tumors were 92%/75%. Intraprocedural perforation occurred in 6.6% of patients; 82% of these were treated successfully with endoscopic therapy. Delayed bleeding occurred in 2.6% of patients. No delayed perforation or procedure-related deaths were observed. There were local recurrences in 3.9% of cases; all occurred after non-curative ESD resection. Metachronous lesions were identified in 14 patients (6.9%). One of 277 patients with clinical follow up died of metachronous gastric cancer that occurred 2.5 years after the initial ESD.

CONCLUSIONS

ESD is a highly effective treatment for superficial gastric neoplasia and should be considered as a viable option for patients in North America. The risk of local recurrence is low and occurs exclusively after non-curative resection. Careful endoscopic surveillance is necessary to identify and treat metachronous lesions.

Direct drive with the argon fluoride laser as a path to high fusion gain with sub-megajoule laser energy

Argon fluoride (ArF) is currently the shortest wavelength laser that can credibly scale to the energy and power required for high gain inertial fusion. ArF's deep ultraviolet light and capability to provide much wider bandwidth than other contemporary inertial confinement fusion (ICF) laser drivers would drastically improve the laser target coupling efficiency and enable substantially higher pressures to drive an implosion. Our radiation hydrodynamics simulations indicate gains greater than 100 are feasible with a sub-megajoule ArF driver. Our laser kinetics simulations indicate that the electron beam-pumped ArF laser can have intrinsic efficiencies of more than 16%, versus about 12% for the next most efficient krypton fluoride excimer laser. We expect at least 10% 'wall plug' efficiency for delivering ArF light to target should be achievable using solid-state pulsed power and efficient electron beam transport to the laser gas that was demonstrated with the U.S. Naval Research Laboratory's Electra facility. These advantages could enable the development of modest size and lower cost fusion power plant modules. This would drastically change the present view on inertial fusion energy as being too expensive and the power plant size too large. This article is part of a discussion meeting issue 'Prospects for high gain inertial fusion energy (part 1)'.

Multimode Hydrodynamic Instability Growth of Preimposed Isolated Defects in Ablatively Driven Foils

The Nike KrF laser facility was used to study the evolution of isolated defects with characteristic sizes of <1 to 10s of μm in laser-accelerated plastic foils. The experimental platform permitted, for the first time, the systematic study of localized perturbation growth, which is inherently multimode, through ablative Richtmyer-Meshkov and Rayleigh-Taylor stages and into the strongly nonlinear regime. Initial target defects were relatively large amplitude, but spatially localized, and emulated tent, fill-tube, and other nonuniformities that are present in inertial confinement fusion capsules. Face-on x-ray radiography indicated initial growth of the perturbation in both depth and width, followed by its apparent closure due to oblique spike growth. Hollow jetlike profiles of laterally expanding, rising, Rayleigh-Taylor bubbles were observed on the rear surface of the target from each isolated defect. Radiation hydrodynamic simulations provided insight into the mechanism of the closure and other features of the bubble and spike evolution specific to isolated defects.

Hybrid target design for imprint mitigation in direct-drive inertial confinement fusion

A target design for mitigating the Rayleigh-Taylor instability is proposed for use in high energy density and direct-drive inertial confinement fusion experiments. In this scheme, a thin gold membrane is offset from the main target by several-hundred microns. A strong picket on the drive beams is incident upon this membrane to produce x rays which generate the initial shock through the target. The main drive follows shortly thereafter, passing through the ablated shell and directly driving the main target. The efficacy of this scheme is demonstrated through experiments performed at the OMEGA EP facility, showing a reduction of the Rayleigh-Taylor instability growth which scales exponentially with frequency, suppressing development by at least a factor of 5 for all wavelengths below 100 μm. This results in a delay in the time of target perforation by ∼40%.

Publisher's Note: Demonstration of Fuel Hot-Spot Pressure in Excess of 50 Gbar for Direct-Drive, Layered Deuterium-Tritium Implosions on OMEGA [Phys. Rev. Lett. 117, 025001 (2016)]

This corrects the article DOI: 10.1103/PhysRevLett.117.025001.

Demonstration of Fuel Hot-Spot Pressure in Excess of 50 Gbar for Direct-Drive, Layered Deuterium-Tritium Implosions on OMEGA

A record fuel hot-spot pressure P_{hs}=56±7  Gbar was inferred from x-ray and nuclear diagnostics for direct-drive inertial confinement fusion cryogenic, layered deuterium-tritium implosions on the 60-beam, 30-kJ, 351-nm OMEGA Laser System. When hydrodynamically scaled to the energy of the National Ignition Facility, these implosions achieved a Lawson parameter ∼60% of the value required for ignition [A. Bose et al., Phys. Rev. E 93, 011201(R) (2016)], similar to indirect-drive implosions [R. Betti et al., Phys. Rev. Lett. 114, 255003 (2015)], and nearly half of the direct-drive ignition-threshold pressure. Relative to symmetric, one-dimensional simulations, the inferred hot-spot pressure is approximately 40% lower. Three-dimensional simulations suggest that low-mode distortion of the hot spot seeded by laser-drive nonuniformity and target-positioning error reduces target performance.

Measurements of electron density and temperature profiles in plasma produced by Nike KrF laser for laser plasma instability research

A grid image refractometer (GIR) has been implemented at the Nike krypton fluoride laser facility of the Naval Research Laboratory. This instrument simultaneously measures propagation angles and transmissions of UV probe rays (λ = 263 nm, Δt = 10 ps) refracted through plasma. We report results of the first Nike-GIR measurement on a CH plasma produced by the Nike laser pulse (∼1 ns FWHM) with the intensity of 1.1 × 10(15) W/cm(2). The measured angles and transmissions were processed to construct spatial profiles of electron density (ne) and temperature (Te) in the underdense coronal region of the plasma. Using an inversion algorithm developed for the strongly refracted rays, the deployed GIR system probed electron densities up to 4 × 10(21) cm(-3) with the density scale length of 120 μm along the plasma symmetry axis. The resulting n(e) and T(e) profiles are verified to be self-consistent with the measured quantities of the refracted probe light.

Integrated molecular pathology accurately determines the malignant potential of pancreatic cysts

BACKGROUND AND STUDY AIMS

Current diagnostic testing is inadequate to determine the malignant potential of pancreatic cysts, resulting in overcautious patient management. Integrated molecular pathology (IMP) testing combines molecular analysis with first-line test results (cytology, imaging, and fluid chemistry) to assess the malignant potential of pancreatic cysts. This multicenter study aimed to determine the diagnostic accuracy of IMP for pancreatic adenocarcinoma, and the utility of IMP testing under current guideline recommendations for managing pancreatic cysts.

PATIENTS AND METHODS

Patients who had undergone previous IMP testing as prescribed by their physician and for whom clinical outcomes were available from retrospective record review were included (n = 492). Performance was determined by correlation between clinical outcome and previous IMP diagnosis ("benign"/"statistically indolent" vs. "statistically higher risk [SHR]"/ "aggressive") or an International Consensus Guideline (Sendai 2012) criteria model for "surveillance" vs. "surgery." The Cox proportional hazards model determined hazard ratios for malignancy.

RESULTS

Benign and statistically indolent IMP diagnoses had a 97 % probability of benign follow-up for up to 7 years and 8 months from initial IMP testing. SHR and aggressive diagnoses had relative hazard ratios for malignancy of 30.8 and 76.3, respectively (both P < 0.0001). Sendai surveillance criteria had a 97 % probability of benign follow-up for up to 7 years and 8 months, but for surgical criteria the hazard ratio was only 9.0 (P < 0.0001). In patients who met Sendai surgical criteria, benign and statistically indolent IMP diagnoses had a > 93 % probability of benign follow-up, with relative hazard ratios for SHR and aggressive IMP diagnoses of 16.1 and 50.2, respectively (both P < 0.0001).

CONCLUSION

IMP more accurately determined the malignant potential of pancreatic cysts than a Sendai 2012 guideline management criteria model. IMP may improve patient management by justifying more relaxed observation in patients meeting Sendai surveillance criteria. IMP can more accurately differentiate between the need for surveillance or surgery in patients meeting Sendai surgical criteria.

Implementation of focal zooming on the Nike KrF laser

In direct drive inertial confinement laser fusion, a pellet containing D-T fuel is imploded by ablation arising from absorption of laser energy at its outer surface. For optimal coupling, the focal spot of the laser would continuously decrease to match the reduction in the pellet's diameter, thereby minimizing wasted energy. A krypton-fluoride laser (λ = 248 nm) that incorporates beam smoothing by induced spatial incoherence has the ability to produce a high quality focal profile whose diameter varies with time, a property known as focal zooming. A two-stage focal zoom has been demonstrated on the Nike laser at the Naval Research Laboratory. In the experiment, a 4.4 ns laser pulse was created in which the on-target focal spot diameter was 1.3 mm (full width at half maximum) for the first 2.4 ns and 0.28 mm for the final 2 ns. These two diameters appear in time-integrated focal plane equivalent images taken at several locations in the amplification chain. Eight of the zoomed output beams were overlapped on a 60 μm thick planar polystyrene target. Time resolved images of self-emission from the rear of the target show the separate shocks launched by the two corresponding laser focal diameters.

Observation of strong oscillations of areal mass in an unsupported shock wave

An experimental study of hydrodynamic perturbation evolution in a strong unsupported shock wave, which is immediately followed by an expansion wave, is reported. A planar solid plastic target rippled on the front side is irradiated with a 350-450 ps long laser pulse. The perturbation evolution in the target is observed using face-on monochromatic x-ray radiography during and for up to 4 ns after the laser pulse. The theoretically predicted large oscillations of the areal mass in the target are observed for the first time. Multiple phase reversals of the areal mass modulation are detected.

Basic hydrodynamics of Richtmyer-Meshkov-type growth and oscillations in the inertial confinement fusion-relevant conditions

In inertial confinement fusion (ICF), the possibility of ignition or high energy gain is largely determined by our ability to control the Rayleigh-Taylor (RT) instability growth in the target. The exponentially amplified RT perturbation eigenmodes are formed from all sources of the target and radiation non-uniformity in a process called seeding. This process involves a variety of physical mechanisms that are somewhat similar to the classical Richtmyer-Meshkov (RM) instability (in particular, most of them are active in the absence of acceleration), but differ from it in many ways. In the last decade, radiographic diagnostic techniques have been developed that made direct observations of the RM-type effects in the ICF-relevant conditions possible. New experiments stimulated the advancement of the theory of the RM-type processes. The progress in the experimental and theoretical studies of such phenomena as ablative RM instability, re-shock of the RM-unstable interface, feedout and perturbation development associated with impulsive loading is reviewed.

Stability of a shock-decelerated ablation front

Experimental study of a shock-decelerated ablation front is reported. A planar solid plastic target is accelerated by a laser across a vacuum gap and collides with a lower-density plastic foam layer. While the target is accelerated, a fast Rayleigh-Taylor (RT) growth of the seeded single-mode perturbation at the ablation front is observed. After the collision, the velocity of the ablation front is seen to remain constant. The reshock quenches the RT growth but does not trigger any Richtmyer-Meshkov growth at the ablation front, which is shown to be consistent with both theory and simulations.

Experimental evidence of impact ignition: 100-fold increase of neutron yield by impactor collision

We performed integrated experiments on impact ignition, in which a portion of a deuterated polystyrene (CD) shell was accelerated to about 600 km/s and was collided with precompressed CD fuel. The kinetic energy of the impactor was efficiently converted into thermal energy generating a temperature of about 1.6 keV. We achieved a two-order-of-magnitude increase in the neutron yield by optimizing the timing of the impact collision, demonstrating the high potential of impact ignition for fusion energy production.

[Treatment of pediatric femur fractures by immediate reduction and spica cast application--clinical and economical feasibility in the Israeli medical system]

BACKGROUND

Pediatric femur fractures are common injuries necessitating immediate application of spica cast or surgical stabilization. Currently, neither conservative nor operative fixation shows superior results; nevertheless, operative intervention has become more common lately. The current study retrospectively investigates short term results of immediate spica cast application, as well as the economic consequences of this treatment.

METHODS

All cases of pediatric (6 months - 6 years) femur fractures treated in a single medium-sized hospital during 3 years were reviewed. Characteristics of fracture treatment and economical aspects were analyzed.

RESULTS

Twenty four patients (17 boys and 7 girls, mean age 2.5 years, range 9 months to 5.5 years), were treated during the study period by immediate closed reduction and spica cast application. Eleven patients were also treated for medical reasons. All cases achieved acceptable alignment and shortening after cast removal. Two patients were re-admitted to the hospital Emergency Room but no changes in treatment were needed, one patient needed re-reduction. Mean hospital stay was 2.75 days. Calculated cost of such treatment is estimated to be almost equal to the compensation given by insurance companies (based on hospital stay in Israel).

CONCLUSIONS

Immediate application of spica cast for pediatric femur fractures, achieves its goals of appropriate fracture-alignment and acceptable complication rates. The authors believe that the compensation should be procedure-based and not hospital-stay based, in a way that will encourage higher efficacy of medical treatment and shortened hospital stay.

Kingella kingae infections in children

Kingella kingae is a beta-hemolytic gram-negative bacillus. It was first described in the 1960's by EO King and has been reported as a cause of osteo-articular pediatric infections since the early 1980's. We performed a retrospective review of all pediatric cases of invasive K. kingae infection between 1997 and 2002, in order to define the incidence, clinical presentation and outcome of invasive K. kingae infections in a pediatric population. During the study period, a total of 24 pediatric patients with K. kingae infection were identified. There were 15 blood culture isolates of K. kingae, out of a total of 1151 (1.3%) positive blood cultures, and 9 synovial fluid culture isolates out of a total of 76 (11.8%) positive synovial fluids. Fifteen patients had osteo-articular infections and 9 had primary bacteremia without osteo-articular infection. Outcome was favorable in all cases and only in 2 patients with knee joint infection was surgical intervention performed, by means of formal knee arthrotomy. All patients recovered uneventfully, in 7 cases without any intervention and in the others with intravenous or oral antibiotic. In conclusion, invasive K. kingae infection is not uncommon in Israel. It usually has a mild course and thus is not always detected and treated. As K. kingae grows best in blood culture broth, blood and joint fluid should always be inoculated into blood culture bottles in suspected cases. This bacterium is highly sensitive to betalactame antibiotics and infection resolves quickly with antibiotic treatment. Surgical intervention for osteo-articular infection is seldom indicated.

Direct observation of mass oscillations due to ablative Richtmyer-Meshkov instability in plastic targets

We report the first direct experimental observation of the ablative Richtmyer-Meshkov instability. It manifests itself in oscillations of areal mass that occur during the shock transit time, which are caused by the "rocket effect" or dynamic overpressure characteristic of interaction between the laser absorption zone and the ablation front. With the 4-ns-long Nike KrF laser pulse and our novel diagnostic technique (monochromatic x-ray imaging coupled to a streak camera) we were able to register a peak and a valley of the areal-mass variation before the observed onset of the Rayleigh-Taylor growth.

Direct observation of feedout-related mass oscillations in plastic targets

"Feedout" means the transfer of mass perturbations from the rear to the front surface of a driven target. When a planar shock wave breaks out at a rippled rear surface of the target, a lateral pressure gradient drives sonic waves in a rippled rarefaction wave propagating back to the front surface. This process redistributes mass in the volume of the target, forming the feedout-generated seed for ablative Rayleigh-Taylor (RT) instability. We report the first direct experimental observation of areal-mass oscillation associated with feedout, followed by the onset of exponential RT growth.