Princeton Plasma Physics Laboratory

About: Princeton Plasma Physics Laboratory is a facility organization based out in Plainsboro Center, New Jersey, United States. It is known for research contribution in the topics: Tokamak & Plasma. The organization has 2427 authors who have published 4475 publications receiving 106926 citations. The organization is also known as: PPPL.

Recent progress towards an advanced spherical torus operating point in NSTX

Abstract: Progress in the development of integrated advanced ST plasma scenarios in NSTX (Ono et al 2000 Nucl. Fusion 40 557) is reported. Recent high-performance plasmas in NSTX following lithium coating of the plasma facing surfaces have achieved higher elongation and lower internal inductance than previously. Analysis of the thermal confinement in these lithiumized discharges shows a stronger plasma current and weaker toroidal field dependence than in previous ST confinement scaling studies; the ITER-98(y, 2) scaling expression describes these scenarios reasonably well. Analysis during periods free of MHD activity has shown that the reconstructed current profile can be understood as the sum of pressure driven, inductive and neutral beam driven currents, without requiring any anomalous fast-ion transport. Non-inductive fractions of 65–70%, and βP > 2, have been achieved at lower plasma current. Some of these low-inductance discharges have a significantly reduced no-wall βN limit, and often have βN at or near the with-wall limit. Coupled m/n = 1/1 + 2/1 kink/tearing modes can limit the sustained β values when rapidly growing ideal modes are avoided. A βN controller has been commissioned and utilized in sustaining high-performance plasmas. 'Snowflake' divertors compatible with high-performance plasmas have been developed. Scenarios with significantly larger aspect ratios have also been developed, in support of next-step ST devices. Overall, these NSTX plasmas have many characteristics required for next-step ST devices.

State-of-the-art neoclassical tearing mode control in DIII-D using real-time steerable electron cyclotron current drive launchers

Abstract: Real-time steerable electron cyclotron current drive (ECCD) has been demonstrated to reduce the power requirements and time needed to remove 3/2 and 2/1 neoclassical tearing modes (NTMs) in the DIII-D tokamak. In a world first demonstration of the techniques required in ITER, the island formation onset is detected automatically, gyrotrons are turned on and the real-time steerable ECCD launcher mirrors are moved promptly to drive current at the location of the islands. This shrinks and suppresses the modes well before saturation using real-time motional Stark effect constrained equilibria reconstruction with advanced feedback and search algorithms to target the deposition. In ITER, this method will reduce the ECCD energy requirement and so raise Q by keeping the EC system off when the NTM is not present. Further, in the experiments with accurate tracking of pre-emptive ECCD to resonant surfaces, both 3/2 and 2/1 modes are prevented from appearing with much lower ECCD peak power than required for removal of a saturated mode.

Measurements of the parallel and transverse Spitzer resistivities during collisional magnetic reconnection

Abstract: Plasma resistivity has been studied experimentally in a reconnecting current sheet. Resistivities during collisional reconnection, when the electron mean free path is much shorter than the current sheet thickness, in the presence and absence of the guide field are found to be in a good agreement with the parallel and transverse Spitzer values, respectively.

Reactor relevant current drive and heating by N-NBI on JT-60U

Abstract: The current drive capability of negative ion based neutral beam injection (N-NBI) in JT-60U has been extended to the reactor relevant regime. The driven current profile and current drive efficiency have been evaluated in a high electron temperature regime Te(0) ≈ 10 keV, and reasonable agreement with the theoretical prediction has been confirmed in this regime. The N-NB driven current reached 1 MA with an injection power of 3.75 MW at a beam energy of 360 keV. A current drive efficiency of 1.55 × 1019A m-2 W-1, approaching the ITER requirement, was achieved in the high βp H mode plasma with Te(0) ≈ 13 keV. This current drive performance permitted sustainment of a high beta (βN = 2.5) and high confinement (HHy2 = 1.4) plasma in the full current driven condition at a plasma current of 1.5 MA. The influence of instabilities on the N-NBI current drive was studied. When a burst-like instability driven by N-NBI occurred in the central region, reductions in loop voltage near the magnetic axis and in the neutron production rate due to loss of beam ions were observed although the lost driven current was at most ~7% of the total driven current. When a neoclassical tearing instability appeared in high beta plasmas, the loss of beam ions was enhanced with increasing instability activity.

Pressure Tensor Elements Breaking the Frozen-In Law During Reconnection in Earth's Magnetotail.

Abstract: Aided by fully kinetic simulations, spacecraft observations of magnetic reconnection in Earth's magnetotail are analyzed. The structure of the electron diffusion region is in quantitative agreement with the numerical model. Of special interest, the spacecraft data reveal how reconnection is mediated by off-diagonal stress in the electron pressure tensor breaking the frozen-in law of the electron fluid.