The hybrid scenario is a candidate for stationary high-fusion gain tokamak operation in ITER and DEMO. To obtain such performance, the energy confinement and the normalized pressure βN must be ...maximized, which requires operating near or above ideal MHD no-wall limits. New experimental findings show how these limits can affect hybrid operation. Even if hybrids are mainly limited by tearing modes, proximity to the no-wall limit leads to 3D field amplification that affects plasma profiles, e.g. rotation braking is observed in ASDEX Upgrade throughout the plasma and peaks in the core. As a result, even the small ASDEX Upgrade error fields are amplified and their effects become visible. To quantify such effects, ASDEX Upgrade measured the response to 3D fields applied by 8×2 non-axisymmetric coils as βN approaches the no-wall limit. The full n = 1 response profile and poloidal structure were measured by a suite of diagnostics and compared with linear MHD simulations, revealing a characteristic feature of hybrids: the n = 1 response is due to a global, marginally-stable n = 1 kink characterized by a large m = 1, n = 1 core harmonic due to qmin being just above 1. A helical core distortion of a few cm forms and affects various core quantities, including plasma rotation, electron and ion temperature, and intrinsic W density. In similar experiments, DIII-D also measured the effect of this helical core on the internal current profile, providing information useful to understanding of the physics of magnetic flux pumping, i.e. anomalous current redistribution by MHD modes that keeps qmin>1. Thanks to flux pumping, a broad current profile is maintained in DIII-D even with large on-axis current drive, enabling fully non-inductive operation at high βN up to 3.5-4.
The plasma response from an external n = 2 magnetic perturbation field in ASDEX Upgrade has been measured using mainly electron cyclotron emission (ECE) diagnostics and a rigid rotating field. To ...interpret ECE and ECE-imaging (ECE-I) measurements accurately, forward modeling of the radiation transport has been combined with ray tracing. The measured data is compared to synthetic ECE data generated from a 3D ideal magnetohydrodynamics (MHD) equilibrium calculated by VMEC. The measured amplitudes of the helical displacement around the outboard midplane are in reasonable agreement with the one from the synthetic VMEC diagnostics. Both exceed the predictions from the vacuum field calculations and indicate the presence of a kink response at the edge, which amplifies the perturbation. VMEC and MARS-F have been used to calculate the properties of this kink mode. The poloidal mode structure of the magnetic perturbation of this kink mode at the edge peaks at poloidal mode numbers larger than the resonant components |m|>|nq|, whereas the poloidal mode structure of its displacement is almost resonant |m|≈|nq|. This is expected from ideal MHD in the proximity of rational surfaces. The displacement measured by ECE-I confirms this resonant response.
Using the MARS-F linear MHD code (Liu et al 2000 Phys. Plasmas 57, 3681), a numerical survey of the plasma response to applied resonant magnetic perturbations in ASDEX Upgrade edge localised mode ...(ELM) control experiments is conducted, to clarify the role of triangularity and the peeling response in the suppression mechanism. The peeling response is found to decrease with increasing triangularity, due to an increase in the coil-plasma gap reducing the effective vacuum field. Therefore the prior hypothesis that the requirement of high triangularity for suppression access is due to the requirement of a sufficiently large peeling response (Nazikian et al 2016 (In XXVI IAEA Int. Conf. on Fusion Energy, Kyoto, Japan) 1-8) is suspected to be incorrect. A secondary hypothesis is proposed, that in high triangularity the drive of the resonant response by the peeling response may be boosted by enhanced poloidal harmonic coupling, which could explain the requirement of high triangularity for suppression access. It is shown that in fact the poloidal harmonic coupling between the resonant and off-resonant components decreases with triangularity, and therefore this hypothesis is also rejected. Finally an alternative hypothesis is discussed, that high triangularity is required to access suppression because the associated enhanced pedestal stability allows the edge deformation to be large enough to control the density, without the reduction in stability due to boundary deformation destabilising ELMs. A rigorous test of this hypothesis requires models to be developed to compute the stability of experimental 3D equilibria.
It has been previously demonstrated in Li et al (2016 Nucl. Fusion 56 126007) that the optimum upper/lower coil phase shift ΔΦopt for alignment of RMP coils for ELM mitigation depends sensitively on ...q95, and other equilibrium plasma parameters. Therefore, ΔΦopt is expected to vary widely during the current ramp of ITER plasmas, with negative implications for ELM mitigation during this period. A previously derived and numerically benchmarked parametrisation of the coil phase for optimal ELM mitigation on ASDEX Upgrade (Ryan et al 2017 Plasma Phys. Control. Fusion 59 024005) is validated against experimental measurements of ΔΦopt, made by observing the changes to the ELM frequency as the coil phase is scanned. It is shown that the parametrisation may predict the optimal coil phase to within 32° of the experimental measurement for n = 2 applied perturbations. It is explained that this agreement is sufficient to ensure that the ELM mitigation is not compromised by poor coil alignment. It is also found that the phase which maximises ELM mitigation is shifted from the phase which maximizes density pump-out, in contrast to theoretical expectations that ELM mitigation and density pump out have the same ΔΦul dependence. A time lag between the ELM frequency response and density response to the RMP is suggested as the cause. The method for numerically deriving the parametrisation is repeated for the ITER coil set, using the baseline scenario as a reference equilibrium, and the parametrisation coefficients given for future use in a feedback coil alignment system. The relative merits of square or sinusoidal toroidal current waveforms for ELM mitigation are briefly discussed.
ABSTRACT
We present spectroscopic measurements for 71 galaxies associated with 62 of the brightest high-redshift submillimetre sources from the Southern fields of the Herschel Astrophysical Terahertz ...Large Area Survey (H-ATLAS), while targeting 85 sources which resolved into 142. We have obtained robust redshift measurements for all sources using the 12-m Array and an efficient tuning of ALMA to optimize its use as a redshift hunter, with 73 per cent of the sources having a robust redshift identification. Nine of these redshift identifications also rely on observations from the Atacama Compact Array. The spectroscopic redshifts span a range 1.41 < z < 4.53 with a mean value of 2.75, and the CO emission line full-width at half-maxima range between $\rm 110\, km\, s^{-1} \lt FWHM \lt 1290\, km\, s^{-1}$ with a mean value of ∼500 km s−1, in line with other high-z samples. The derived CO(1-0) luminosity is significantly elevated relative to line-width to CO(1-0) luminosity scaling relation, which is suggestive of lensing magnification across our sources. In fact, the distribution of magnification factors inferred from the CO equivalent widths is consistent with expectations from galaxy–galaxy lensing models, though there is a hint of an excess at large magnifications that may be attributable to the additional lensing optical depth from galaxy groups or clusters.
Abstract
We present Institut de Radioastronomie Millimétrique Plateau de Bure Interferometer observations of the 12CO (3-2) emission from two far-infrared luminous QSOs at z ∼ 2.5 selected from the ...Herschel-Astrophysical Tetrahertz Large Area Survey. These far-infrared bright QSOs were selected to have supermassive black holes (SMBHs) with masses similar to those thought to reside in submillimetre galaxies (SMGs) at z ∼ 2.5, making them ideal candidates as systems in the potential transition from an ultraluminous infrared galaxy phase to a submillimetre faint, unobscured, QSO. We detect 12CO (3-2) emission from both QSOs and we compare their baryonic, dynamical and SMBH masses to those of SMGs at the same epoch. We find that these far-infrared bright QSOs have similar dynamical but lower gas masses than SMGs. We combine our results with literature values and find that at a fixed L
FIR, far-infrared bright QSOs have ∼50 ± 30 per cent less warm/dense gas than SMGs. Taken together with previous results, which show that QSOs lack the extended, cool reservoir of gas seen in SMGs, this suggests that far-infrared bright QSOs are at a different evolutionary stage. This is consistent with the hypothesis that far-infrared bright QSOs represent a short (∼1 Myr) but ubiquitous phase in the transformation of dust-obscured, gas-rich, starburst-dominated SMGs into unobscured, gas-poor, QSOs.
This paper reports measurements of final-state proton multiplicity, muon and proton kinematics, and their correlations in charged-current pionless neutrino interactions, measured by the T2K ND280 ...near detector in its plastic scintillator (C8H8) target. The data were taken between years 2010 and 2013, corresponding to approximately 6×1020 protons on target. Thanks to their exploration of the proton kinematics and of imbalances between the proton and muon kinematics, the results offer a novel probe of the nuclear-medium effects most pertinent to the (sub-)GeV neutrino-nucleus interactions that are used in accelerator-based long-baseline neutrino oscillation measurements. These results are compared to many neutrino-nucleus interaction models which all fail to describe at least part of the observed phase space. In case of events without a proton above a detection threshold in the final state, a fully consistent implementation of the local Fermi gas model with multinucleon interactions gives the best description of the data. In the case of at least one proton in the final state, the spectral function model agrees well with the data, most notably when measuring the kinematic imbalance between the muon and the proton in the plane transverse to the incoming neutrino. Within the models considered, only the existence of multinucleon interactions are able to describe the extracted cross section within regions of high transverse kinematic imbalance. The effect of final-state interactions is also discussed.
ABSTRACT Exploiting the sensitivity and spatial resolution of the Atacama Large Millimeter/submillimeter Array, we have studied the morphology and the physical scale of the interstellar medium-both ...gas and dust-in SGP 38326, an unlensed pair of interacting starbursts at z = 4.425. SGP 38326 is the most luminous star bursting system known at z > 4, with a total IR luminosity of LIR ∼ 2.5 × 1013 L and a star formation rate of ∼ 4500 M yr−1. SGP 38326 also contains a molecular gas reservoir among the most massive yet found in the early universe, and it is the likely progenitor of a massive, red-and-dead elliptical galaxy at z ∼ 3. Probing scales of ∼0 1 or ∼800 pc we find that the smooth distribution of the continuum emission from cool dust grains contrasts with the more irregular morphology of the gas, as traced by the C ii fine structure emission. The gas is also extended over larger physical scales than the dust. The velocity information provided by the resolved C ii emission reveals that the dynamics of the two interacting components of SGP 38326 are each compatible with disk-like, ordered rotation, but also reveals an ISM which is turbulent and unstable. Our observations support a scenario where at least a subset of the most distant extreme starbursts are highly dissipative mergers of gas-rich galaxies.
We report the redshift of HATLAS J132427.0+284452 (hereafter HATLAS J132427), a gravitationally lensed starburst galaxy, the first determined 'blind' by the Herschel Space Observatory. This is ...achieved via the detection of C ii consistent with z = 1.68 in a far-infrared spectrum taken with the SPIRE Fourier Transform Spectrometer (FTS). We demonstrate that the C ii redshift is secure via detections of CO J = 2 → 1 and 3 → 2 using the Combined Array for Research in Millimeter-wave Astronomy and the Institut de Radioastronomie Millimétrique's Plateau de Bure Interferometer. The intrinsic properties appear typical of high-redshift starbursts despite the high lensing-amplified fluxes, proving the ability of the FTS to probe this population with the aid of lensing. The blind detection of C ii demonstrates the potential of the SPICA Far-infrared Instrument imaging spectrometer, proposed for the much more sensitive Space Infrared Telescope for Cosmology and Astrophysics mission, to determine redshifts of multiple dusty galaxies simultaneously without the benefit of lensing.
Background: A totally transoral outpatient procedure for the treatment of GERD would be appealing.
Methods: A multicenter trial was initiated that included 64 patients with GERD treated with an ...endoscopic suturing device. Inclusion criteria were 3 or more heartburn episodes per week while not taking medication, dependency on antisecretory medicine, and documented acid reflux by pH monitoring. Exclusion criteria were dysphagia, grade 3 or 4 esophagitis, obesity, and hiatus hernia greater than 2 cm in length. Patients underwent manometry, endoscopy, 24-hour pH monitoring, and symptom severity scoring before and after the procedure. Patients were randomized to a linear or circumferential plication configuration. Adverse procedural events were recorded.
Results: Mean 6-month symptom score changes demonstrated procedural efficacy. Heartburn severity and frequency as well as regurgitation all improved (
p > 0.0001 for each). Twenty-four−hour pH monitoring showed improvement in number of episodes below pH of 4 at 3 and 6 months (
p < 0.0007 and 0.0002) and percentage of total time the pH was less than 4 at 6 months (
p < 0.011). Plication configuration did not affect symptoms or pH monitoring results. One patient had a self-contained suture perforation that was successfully treated with antibiotics.
Conclusion: Endoscopic gastroplasty is safe. It is associated with reduced symptoms and medication use at 6 month follow-up in patients with uncomplicated GERD. (Gastrointest Endosc 2001;53:416-22.)
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