A novel rotating HTS flux pump incorporating a ferromagnetic circuit

High-temperature superconductor (HTS) flux pumps enable large currents to be injected into a superconducting coil without requiring normal-conducting current leads. We present results from an experimental axial-type HTS rotating flux pump that employs a ferromagnetic circuit to focus incident flux upon a coated-conductor stator wire. We show that this device can inject currents of > 50 A into an HTS coil at 77 K and is capable of operating at flux gaps greater than 18 mm. Accommodating a cryostat wall within this flux gap will enable future flux pump designs, in which all moving parts are located outside the cryostat. © 2016 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.

A novel rotating HTS flux pump incorporating a ferromagnetic circuit

High-temperature superconductor (HTS) flux pumps enable large currents to be injected into a superconducting coil without requiring normal-conducting current leads. We present results from an experimental axial-type HTS rotating flux pump that employs a ferromagnetic circuit to focus incident flux upon a coated-conductor stator wire. We show that this device can inject currents of > 50 A into an HTS coil at 77 K and is capable of operating at flux gaps greater than 18 mm. Accommodating a cryostat wall within this flux gap will enable future flux pump designs, in which all moving parts are located outside the cryostat. © 2016 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.

A hot mini-Neptune in the radius valley orbiting solar analogue HD 110113

We report the discovery of HD 110113 b (TOI-755.01), a transiting mini-Neptune exoplanet on a 2.5-day orbit around the solar-analogue HD 110113 (Teff= 5730K). Using TESS photometry and HARPS radial velocities gathered by the NCORES program, we find HD 110113 b has a radius of 2.05 ± 0.12 R⊕ and a mass of 4.55 ± 0.62 M⊕. The resulting density of $2.90^{+0.75}_{-0.59}$ g cm−3 is significantly lower than would be expected from a pure-rock world; therefore, HD 110113 b must be a mini-Neptune with a significant volatile atmosphere. The high incident flux places it within the so-called radius valley; however, HD 110113 b was able to hold on to a substantial (0.1-1 per cent) H-He atmosphere over its ∼4Gyr lifetime. Through a novel simultaneous Gaussian process fit to multiple activity indicators, we were also able to fit for the strong stellar rotation signal with period 20.8 ± 1.2 d from the RVs and confirm an additional non-transiting planet, HD 110113 c, which has a mass of 10.5 ± 1.2 M⊕ and a period of $6.744^{+0.008}_{-0.009}$ d.

Carbonate-silicate cycle predictions of Earth-like planetary climates and testing the habitable zone concept

In the conventional habitable zone (HZ) concept, a CO2-H2O greenhouse maintains surface liquid water. Through the water-mediated carbonate-silicate weathering cycle, atmospheric CO2 partial pressure (pCO2) responds to changes in surface temperature, stabilizing the climate over geologic timescales. We show that this weathering feedback ought to produce a log-linear relationship between pCO2 and incident flux on Earth-like planets in the HZ. However, this trend has scatter because geophysical and physicochemical parameters can vary, such as land area for weathering and CO2 outgassing fluxes. Using a coupled climate and carbonate-silicate weathering model, we quantify the likely scatter in pCO2 with orbital distance throughout the HZ. From this dispersion, we predict a two-dimensional relationship between incident flux and pCO2 in the HZ and show that it could be detected from at least 83 (2σ) Earth-like exoplanet observations. If fewer Earth-like exoplanets are observed, testing the HZ hypothesis from this relationship could be difficult.

Parametric study of hydrogenic inventory in the ITER divertor based on machine learning

A parametric study is performed with the 2D FESTIM code for the ITER monoblock geometry. The influence of the monoblock surface temperature, the incident ion energy and particle flux on the monoblock hydrogen inventory is investigated. The simulated data is analysed with a Gaussian regression process and an inventory map as a function of ion energy and incident flux is given. Using this inventory map, the hydrogen inventory in the divertor is easily derived for any type of scenario. Here, the case of a detached ITER scenario with inputs from the SOLPS code is presented. For this scenario, the hydrogen inventory per monoblock is highly dependent of surface temperature and ranges from $$10^{18}$$ 10 18 to $$6 \times 10^{19}$$ 6 × 10 19 H after a $$10^{7}$$ 10 7 s exposure. The inventory evolves as a power law of time and is lower at strike points where the surface temperature is high. Hydrogen inventory in the whole divertor after a $$10^{7}$$ 10 7 s exposure is estimated at approximately 8 g.

Influence of a thermal boundary layer on the thermal evolution of Uranus and Neptune

<p>It has been a long-standing challenge to reconcile the perceived similarities of Uranus and Neptune with their highly different intrinsic heat fluxes. Previous evolution calculations using the conventional assumption of an adiabatic interior yield too high present-day luminosities or - equivalently - too long cooling times for Uranus  (e.g. [1,2]). For Neptune, however, we found that similar assumptions yield too short cooling times [3].<br />One proposed mechanism for reproducing the observed brightness is a conducting interface between the hydrogen- and helium-rich outer part and the ice-rich inner part that would inhibit efficient energy transport across it [4]. In this work, we use our recently developed tool for modelling giant planets based on the Henyey-method for stellar <br />evolutions [5] to investigate such a conducting interface in the planet's interior, examining the influence of parameters such as assumed layer thickness and thermal conductivity on the cooling behaviour. <br />We find that even a thin conductive interface of a few kilometers has significant influence on the planetary cooling. Initially, the presence of such a boundary layer speeds up cooling, while after about 0.1-0.5 Gyr the cooling is slowed down drastically compared to the adiabatic case, similar to what was found for Saturn previously [6]. Our preferred solutions for Uranus suggest equilibrium evolution with the solar incident flux, while for Neptune, we find that plateaus in T<sub>eff</sub>(t) near its observed value require fine-tuned combinations of layer thickness and thermal conducitivity. </p> <p>[1] Fortney, Ikoma, Nettelmann, Guillot, and Marley (2011). ApJ 729, 32<br />[2] Nettelmann, Helled, Fortney, and Redmer (2013). Planet. Space Sci. 77, 143<br />[3] Scheibe, Nettelmann, Redmer (2019). A&A 632, A70<br />[4] Nettelmann, Wang, Fortney, Hamel, Yellamilli, Bethkenhagen, and Redmer (2016). Icarus 275, 107<br />[5] Henyey, Forbes, and Gould (1964). ApJ 139, 306<br />[6] Leconte and Chabrier (2013): Nat Geosci. 6, 023007</p>

Off-Axis Characterisation of the CERN T10 Beam for low Momentum Proton Measurements with a High Pressure Gas Time Projection Chamber

We present studies of proton fluxes in the T10 beamline at CERN. A prototype high pressure gas time projection chamber (TPC) was exposed to the beam of protons and other particles, using the 0.8 GeV/c momentum setting in T10, in order to make cross section measurements of low energy protons in argon. To explore the energy region comparable to hadrons produced by GeV-scale neutrino interactions at oscillation experiments, i.e., near 0.1 GeV of kinetic energy, methods of moderating the T10 beam were employed: the dual technique of moderating the beam with acrylic blocks and measuring scattered protons off the beam axis was used to decrease the kinetic energy of incident protons, as well as change the proton/minimum ionising particle (MIP) composition of the incident flux. Measurements of the beam properties were made using time of flight systems upstream and downstream of the TPC. The kinetic energy of protons reaching the TPC was successfully changed from ∼0.3 GeV without moderator blocks to less than 0.1 GeV with four moderator blocks (40 cm path length). The flux of both protons and MIPs off the beam axis was increased. The ratio of protons to MIPs vary as a function of the off-axis angle allowing for possible optimisation of the detector to select the type of required particles. Simulation informed by the time of flight measurements show that with four moderator blocks placed in the beamline, (5.6 ± 0.1) protons with energies below 0.1 GeV per spill traversed the active TPC region. Measurements of the beam composition and energy are presented.

A New Diffuse Optics Emitter for High Visual Diffuse Transmission Density Measurement

In visual diffuse transmission density measurement, it is hard to measure optical density (OD) up to 6.0 because the signal to noise is more than 10E-06. Thus, there are only two methods to find the measurement. One is using a highly sensitive detector with low background noise, and the other is improving the incident light flux with a wide spectrum, including visual scope. A new diffuse optics emitter was designed to realize OD measurements up to 6.0. It uses 235 optical fibers on a hemisphere to collect and feed in the incident flux, then emits this flux by a diffuse opal. Thus, an incident light with a high diffuse coefficient and high incident flux was realized for high OD measurement. This emitter has been used in the new national reference of National Institute of Metrology, China (NIM) for diffuse transmission optical density. According to the measurement result in this reference, the OD can be measured up to 6.6.

Validation of a temperate fourth planet in the K2-133 multiplanet system

We present follow-up observations of the K2-133 multiplanet system. Previously, we announced that K2-133 contained three super-Earths orbiting an M1.5V host star – with tentative evidence of a fourth outer-planet orbiting at the edge of the temperate zone. Here, we report on the validation of the presence of the fourth planet, determining a radius of $1.73_{-0.13}^{+0.14}$ R⊕. The four planets span the radius gap of the exoplanet population, meaning further follow-up would be worthwhile to obtain masses and test theories of the origin of the gap. In particular, the trend of increasing planetary radius with decreasing incident flux in the K2-133 system supports the claim that the gap is caused by photo-evaporation of exoplanet atmospheres. Finally, we note that K2-133 e orbits on the edge of the star's temperate zone, and that our radius measurement allows for the possibility that this is a rocky world. Additional mass measurements are required to confirm or refute this scenario.