Cavatappi artificial muscles from drawing, twisting, and coiling polymer tubes.

Compliant, biomimetic actuation technologies that are both efficient and powerful are necessary for robotic systems that may one day interact, augment, and potentially integrate with humans. To this end, we introduce a fluid-driven muscle-like actuator fabricated from inexpensive polymer tubes. The actuation results from a specific processing of the tubes.

Absolute calibration of the Lyman-α measurement apparatus at DIII-D.

The LLAMA (Lyman-Alpha Measurement Apparatus) diagnostic was recently installed on the DIII-D tokamak [Rosenthal et al., Rev. Sci.

Integration of full divertor detachment with improved core confinement for tokamak fusion plasmas.

Divertor detachment offers a promising solution to the challenge of plasma-wall interactions for steady-state operation of fusion reactors. Here, we demonstrate the excellent compatibility of actively controlled full divertor detachment with a high-performance (β ~ 3, H ~ 1.5) core plasma, using high-β (poloidal beta, β > 2) scenario characterized by a sustained core internal transport barrier (ITB) and a modest edge transport barrier (ETB) in DIII-D tokamak.

Evidence of Toroidally Localized Turbulence with Applied 3D Fields in the DIII-D Tokamak.

New evidence indicates that there is significant 3D variation in density fluctuations near the boundary of weakly 3D tokamak plasmas when resonant magnetic perturbations are applied to suppress transient edge instabilities. The increase in fluctuations is concomitant with an increase in the measured density gradient, suggesting that this toroidally localized gradient increase could be a mechanism for turbulence destabilization in localized flux tubes. Two-fluid magnetohydrodynamic simulations find that, although changes to the magnetic field topology are small, there is a significant 3D variation of the density gradient within the flux surfaces that is extended along field lines.

Self-regulated oscillation of transport and topology of magnetic islands in toroidal plasmas.

The coupling between the transport and magnetic topology is an important issue because the structure of magnetic islands, embedded in a toroidal equilibrium field, depends on the nature of the transport at the edge of the islands. Measurements of modulated heat pulse propagation in the DIII-D tokamak have revealed the existence of self-regulated oscillations in the radial energy transport into magnetic islands that are indicative of bifurcations in the island structure and transport near the q = 2 surface. Large amplitude heat pulses are seen in one state followed by small amplitude pulses later in the discharge resulting in a repeating cycle of island states.

Pedestal bifurcation and resonant field penetration at the threshold of edge-localized mode suppression in the DIII-D Tokamak.

Rapid bifurcations in the plasma response to slowly varying n=2 magnetic fields are observed as the plasma transitions into and out of edge-localized mode (ELM) suppression. The rapid transition to ELM suppression is characterized by an increase in the toroidal rotation and a reduction in the electron pressure gradient at the top of the pedestal that reduces the perpendicular electron flow there to near zero. These events occur simultaneously with an increase in the inner-wall magnetic response.

Observation of a multimode plasma response and its relationship to density pumpout and edge-localized mode suppression.

Density pumpout and edge-localized mode (ELM) suppression by applied n=2 magnetic fields in low-collisionality DIII-D plasmas are shown to be correlated with the magnitude of the plasma response driven on the high-field side (HFS) of the magnetic axis but not the low-field side (LFS) midplane. These distinct responses are a direct measurement of a multimodal magnetic plasma response, with each structure preferentially excited by a different n=2 applied spectrum and preferentially detected on the LFS or HFS. Ideal and resistive magneto-hydrodynamic (MHD) calculations find that the LFS measurement is primarily sensitive to the excitation of stable kink modes, while the HFS measurement is primarily sensitive to resonant currents (whether fully shielding or partially penetrated).

2D soft x-ray system on DIII-D for imaging the magnetic topology in the pedestal region.

A new tangential two-dimensional soft x-ray imaging system (SXRIS) is being designed to examine the edge island structure in the lower X-point region of DIII-D. Plasma shielding and/or amplification of the calculated vacuum islands may play a role in the suppression of edge-localized modes via resonant magnetic perturbations (RMPs). The SXRIS is intended to improve the understanding of three-dimensional (3D) phenomena associated with RMPs.

Simulation of a tangential soft x-ray imaging system.

Tangentially viewing soft x-ray (SXR) cameras are capable of detecting nonaxisymmetric plasma structures in magnetically confined plasmas. They are particularly useful for studying stationary perturbations or phenomenon that occur on a timescale faster than the plasma rotation period. Tangential SXR camera diagnostics are planned for the DIII-D and NSTX tokamaks to elucidate the static edge magnetic structure during the application of 3D perturbations.

Wide-field turbulence imaging with beam emission spectroscopy.

Imaging of the size, shape, time-averaged, and time-resolved dynamics of long-wavelength density turbulence structures is accomplished with an expanded, high-sensitivity, wide-field beam emission spectroscopy (BES) diagnostic on DIII-D. A 64-channel BES system is configured with an 8×8 grid of discrete channels that image an approximately 7×9 cm region at the outboard midplane. The grid covers multiple correlation lengths and each channel shape matches the measured radial-poloidal correlation length asymmetry of turbulent eddies.

Localized turbulence suppression and increased flow shear near the q=2 surface during internal-transport-barrier formation.

Broadband turbulent fluctuations in the plasma density are transiently suppressed when low-order rational q surfaces first appear in negative central magnetic shear plasmas on the DIII-D tokamak, which can lead to the formation of internal transport barriers. Increased localized flow shear is simultaneously observed. It transiently exceeds the measured turbulence decorrelation rate, providing a mechanism to trigger the formation of the transport barrier.

A correlation electron cyclotron emission diagnostic and the importance of multifield fluctuation measurements for testing nonlinear gyrokinetic turbulence simulations.

A correlation electron cyclotron emission (CECE) diagnostic has been used to measure local, turbulent fluctuations of the electron temperature in the core of DIII-D plasmas. This paper describes the hardware and testing of the CECE diagnostic and highlights the importance of measurements of multifield fluctuation profiles for the testing and validation of nonlinear gyrokinetic codes. The process of testing and validating such codes is critical for extrapolation to next-step fusion devices.

Singular value decomposition filtering for enhanced signal extraction from two-dimensional beam emission spectroscopy measurements.

The signal-to-noise ratio (SNR) of extracted turbulence features from beam emission spectroscopy (BES) data is significantly enhanced via application of singular value decomposition (SVD) methods. BES measures two-dimensional localized density fluctuations in DIII-D. The SNR of core turbulence characteristics is typically limited by noise arising from electronic noise, photon noise, and fluctuations in the observed neutral beam.

Ultrafast ion temperature and toroidal velocity fluctuation spectroscopy diagnostic design.

High sensitivity measurements of localized, long-wavelength ion temperature, and toroidal velocity fluctuations (T(i)/T(i),v(parallel)/v(parallel)) are required to address critical issues pertaining to turbulent transport. This diagnostic design exploits emission from charge exchange recombination between neutral beam atoms and the intrinsic carbon impurity. The n=8-7 transition of C VI at lambda(0)=529.

Antibody array profiling reveals serum TSP-1 as a marker to distinguish benign from malignant prostatic disease.

Background: Blood protein markers that provide more accurate or earlier diagnosis of prostate cancer should have a positive impact on prostate cancer treatment and management.

Methods: Serum samples from control subjects and patients with benign or malignant prostatic disease were analyzed on antibody arrays targeting multiple candidate prostate cancer markers and detected with two-color, rolling-circle amplification (TC-RCA). The measurements of certain antibodies were validated using immunoblots, immunoprecipitation/mass spectrometry, and sandwich immunoassays.

Detection of zero-mean-frequency zonal flows in the core of a high-temperature tokamak plasma.

A low-frequency, spectrally broad (Deltaf approximately 10 kHz) poloidal flow structure that peaks near zero frequency is observed in time-resolved measurements of the turbulence velocity field in the core region (r/a approximately 0.6-0.9) of DIII-D tokamak plasmas.