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The path to fusion in the United States requires partnership between public and private sector. While the private sector provides the vigor to take some of the major steps necessary, there is a depth of expertise and capability in the public sector that is vital to resolving feasible approaches. As an open national user facility, DIII-D provides a crucial testbed to develop the required new technologies and approaches in relevant conditions. It has unparalleled potential to meet this challenge, thanks to its extreme flexibility and world leading diagnostics. This provides a basis to rapidly develop solutions that project to future reactors with confidence. The program has thus been redeveloped to enable public and private sector engagement and testing of new concepts. A new technology program has been launched to resolve plasma interacting technologies. With modest heating upgrades, the facility can confront the crucial "Integrated Tokamak Exhaust and Performance" gap, to resolve core, exhaust and technology solutions together. The device is also being redeveloped as a training facility, with dedicated student run time, a mentorship program, and open access to all opportunity roles, part of wider efforts to diversify and open pathways through inclusion, access, and equity. This exciting agenda is enabling scientists and technology researchers to pioneer the solutions needed for a Fusion Pilot Plant (FPP) and ITER this decade. As a national user facility, DIII D has singular potential to provide the tools, teams, and insight necessary, to do its part in moving the United States rapidly toward the commercialization of fusion energy. [ABSTRACT FROM AUTHOR]

Joseph Biederman,1,2 Thomas J Spencer,1,2 Carter Petty,1 Laran L Hyder,1 Katherine B O’Connor,1 Craig BH Surman,1,2 Stephen V Faraone31Clinical and Research Program in Pediatric Psychopharmacology and Adult ADHD, Massachusetts General Hospital, Pediatric Psychopharmacology Unit, Yawkey Center for Outpatient Care, Boston, MA, 2Department of Psychiatry, Harvard Medical School, Cambridge, MA, 3Departments of Psychiatry and of Neuroscience and Physiology, SUNY Upstate Medical University, Syracuse, NYBackground: While symptoms of deficient emotional self-regulation (DESR) have been long associated with attention-deficit/hyperactivity disorder (ADHD), there has been limited investigation of this aspect of the clinical picture of the disorder. The main aim of this study was to examine the predictive utility of DESR in moderating the course of ADHD children into adolescence.Methods: Subjects comprised 177 children with and 204 children without ADHD followed for an average of 4 years (aged 6–18 years at baseline, 54% male). Subjects were assessed with structured diagnostic interviews and measures of psychosocial functioning. DESR was defined by the presence (n = 79) or absence (n = 98) of Child Behavior Checklist (CBCL)-DESR profile (score ≥ 180 < 210 total of Attention, Aggression, and Anxious/Depressed subscales) at the baseline assessment.Results: Of subjects with DESR at baseline, 57% had DESR at follow-up. Persistent ADHD was significantly associated with DESR at follow-up (χ2(1) = 15.37, P < 0.001). At follow-up, ADHD + DESR subjects had significantly more comorbidities (z = 2.55, P = 0.01), a higher prevalence of oppositional defiant disorder (z = 3.01, P = 0.003), and more impaired CBCL social problems t-score (t(227) = 2.41, P = 0.02) versus ADHD subjects.Conclusion: This work suggests that a positive CBCL-DESR profile predicts subsequent psychopathology and functional impairments in children with ADHD suggesting that it has the potential to help identify children with ADHD at high risk for compromised outcomes.Keywords: attention-deficit/hyperactivity disorder, emotion, regulation, longitudinal, youth

This work provides a first experimental measurement of broadened ECH deposition on the DIIID tokamak. As seen in theory[1] and simulation[2], refraction by edge density fluctuations shifts the path of RF waves, altering ECH and ECCD deposition. This paper reports on an initial experimental confirmation of broadened ECH deposition on DIII-D tokamak. Te measurements from a 48 channel 2nd Harmonic ECE Radiometer digitized at 500 kHz are used with a set of broadened trial ECH deposition functions to calculate time-dependent, modulation-induced heat fluxes. The fitting of convective and diffusive transport to these fluxes allows different ECH deposition profiles to be compared. The best-fit ECH deposition produces reasonable transport coefficients which compare favorably with simulation. This method is applied to a set of L- and H- mode DIII-D discharges. Accounting for diffusive, convective, and coupled transport, the ECH deposition profile is found to be 2 to 3 times wider than predicted by TORAY-GA ray tracing.

Microwave heat pulse propagation experiments have demonstrated a correlation between millimeter-scale turbulence and deposition profile broadening of electron cyclotron (EC) waves on the DIII-D tokamak. In a set of discharges in DIII-D, a variation in edge density fluctuations on the mm-scale is associated with 40%–150% broader deposition profiles, expressed in terms of normalized minor radius, as compared with equilibrium ray tracing. The 1D power profile is determined from transport analysis of the electron temperature response to EC power modulation using perturbative analysis with a square wave power modulation at 20–70 Hz, producing a series of Fourier harmonics that are fit collectively to resolve transport. Fitting an integrated heat flux expressed in the Fourier basis of the modulation to diffusive, convective, and coupled transport terms in a linear model can resolve the broadened EC deposition width from the power perturbation to resolve a broadening in each case. The best fit degree of beam broadening observed scales approximately linearly with the Doppler backscattering measured fluctuation level in the steep gradient region. Quantifying the effect of edge fluctuation broadening on EC current drive power needs of future devices will require 3D full-wave codes that can be validated on the current generation of machines. These DIII-D experiments provide a quantitative measure of fluctuation effects and a dataset to benchmark full-wave simulations that can model and eventually predict nonlinear effects neglected by 1D equilibrium beam and ray tracing. [ABSTRACT FROM AUTHOR]

The L-H transition power threshold (PLH) is found to have a significant dependence on q95, at ne ∼ 3.2 × 1019 m−3 on DIII-D. Comprehensive 2D turbulence and flow measurements in the plasma edge reveal the co-existence of two frequency bands of broadband modes across the L-H transition with higher flow shear at higher q95, which can help explain the linear decrease in PLH as q95 is increased from 3.5 to 4.9. Density fluctuation measurements by beam emission spectroscopy at higher q95 show that the lower frequency band (<20 kHz) of the broadband modes propagates in the ion diamagnetic direction in the lab frame (identified as an ion mode), whereas the higher frequency band (>20 kHz) propagates in the electron diamagnetic direction (identified as an electron mode). The turbulence amplitude at the plasma edge is higher at higher q95, implying a higher drive for a Reynolds stress driven zonal flow. At lower density, ne ∼ 1.5 × 1019 m−3, there is little dependence of PLH on q95. Linear CGYRO kinetic simulation has shown a switch from one mode to two modes at higher q95 at ne ∼ 3.2 × 1019 m−3 compared to lower q95. The ion temperature profile has been shown to strongly impact the dual mode characteristics with the increasing growth rate of the ion mode at a higher edge Ti gradient. The observations suggest that it may be possible to reduce the required input power to trigger the L-H transition for ITER if both the ion and electron modes are similarly driven in the plasma edge. [ABSTRACT FROM AUTHOR]

Plasmas with a negative triangularity shape have been created on the DIII-D tokamak that, despite maintaining standard L-mode edge radial profiles, reach volume averaged pressure levels typical of H-mode scenarios. Within the auxiliary power available for these experiments, plasmas exhibit near-zero power degradation while sustaining βN = 2.7 and H98,y2 = 1.2 for several energy confinement times. Detailed comparison with matched discharges at positive triangularity indicates that Trapped Electron Modes are weakened at negative triangularity, consistent with increased confinement and reduced intensity of fluctuations in electron density, electron temperature, and ion density. These results indicate that a negative triangularity plasma operating without an edge pedestal might provide an attractive scenario for operations in future reactors. [ABSTRACT FROM AUTHOR]

In DIII-D hybrid discharges, the intense Alfvén eigenmode (AE) activity driven by Neutral Beam Injection that is typically observed can be suppressed and replaced by fishbone modes when Electron Cyclotron Current Drive (ECCD) is centrally applied. Simulations have been carried out with the kinetic-magnetohydrodynamic hybrid code M3D-K based on DIII-D discharges #161401 without ECCD and #161403 with ECCD, respectively. In both cases, unstable modes are found—the mode frequency and the mode structure indicate that the instability excited in #161403 is of fishbone type, while that in #161401 is identified as the beta-induced Alfvén eigenmode-like mode. Moreover, we find that the calculated mode frequencies of these two shots are consistent with experimental observations. A systematic scan has been performed to study the instability region of n = 1 , 2 , 3 modes in (q 0 , β h o t) parameter space, where n is the toroidal mode number, q 0 is the safety factor value at the magnetic axis, and β h o t is the energetic particle beta. It is found that the transition between AEs and fishbone modes can occur when q 0 is changed. In addition, the modes of n = 1 , 2 , 3 are stable or weakly unstable in the region of P h o t / P total ≤ 0.5 and 1.2 < q 0 < 1.3 , where P h o t is the central energetic particle pressure and P total is the central total pressure. These results provide useful guidance for future experiments for minimizing energetic particle-driven instabilities and associated transport. [ABSTRACT FROM AUTHOR]

Describes the design and performance of a multikilowatt Pockels cell for use in high average power laser systems. Power levels of the switching performance and low-wave-front distortion; Problem of electric field uniformity; Overview of thermally compensated transverse field geometry using a prototype switch assembly.

An engineering upgrade to the neutral beam system at the DIII-D tokamak [J. L. Luxon, Nucl. Fusion 42, 614 (2002)] enables time-dependent programming of the beam voltage and current. Initial application of this capability involves pre-programmed beam voltage and current injected into plasmas that are known to be susceptible to instabilities that are driven by energetic ( E ≥ 40 keV) beam ions. These instabilities, here all Alfvén eigenmodes (AEs), increase the transport of the beam ions beyond a classical expectation based on particle drifts and collisions. Injecting neutral beam power, P beam ≥ 2 MW, at reduced voltage with increased current reduces the drive for Alfvénic instabilities and results in improved ion confinement. In lower-confinement plasmas, this technique is applied to eliminate the presence of AEs across the mid-radius of the plasmas. Simulations of those plasmas indicate that the mode drive is decreased and the radial extent of the remaining modes is reduced compared to a higher beam voltage case. In higher-confinement plasmas, this technique reduces AE activity in the far edge and results in an interesting scenario of beam current drive improving as the beam voltage reduces from 80 kV to 65 kV. [ABSTRACT FROM AUTHOR]