The JCMT BISTRO Survey: A Spiral Magnetic Field in a Hub-filament Structure, Monoceros R2

We present and analyze observations of polarized dust emission at 850 μm toward the central 1 7 1 pc hub-filament structure of Monoceros R2 (Mon R2). The data are obtained with SCUBA-2/POL-2 on the James Clerk Maxwell Telescope (JCMT) as part of the B-fields in Star-forming Region Observations survey. The orientations of the magnetic field follow the spiral structure of Mon R2, which are well described by an axisymmetric magnetic field model. We estimate the turbulent component of the magnetic field using the angle difference between our observations and the best-fit model of the underlying large-scale mean magnetic field. This estimate is used to calculate the magnetic field strength using the Davis–Chandrasekhar–Fermi method, for which we also obtain the distribution of volume density and velocity dispersion using a column density map derived from Herschel data and the C18O (J = 3 - 2) data taken with HARP on the JCMT, respectively. We make maps of magnetic field strengths and mass-to-flux ratios, finding that magnetic field strengths vary from 0.02 to 3.64 mG with a mean value of 1.0 \ub1 0.06 mG, and the mean critical mass-to-flux ratio is 0.47 \ub1 0.02. Additionally, the mean Alfv\ue9n Mach number is 0.35 \ub1 0.01. This suggests that, in Mon R2, the magnetic fields provide resistance against large-scale gravitational collapse, and the magnetic pressure exceeds the turbulent pressure. We also investigate the properties of each filament in Mon R2. Most of the filaments are aligned along the magnetic field direction and are magnetically subcritical

The JCMT BISTRO Survey: Studying the Complex Magnetic Field of L43

We present observations of polarized dust emission at 850 μm from the L43 molecular cloud, which sits in the Ophiuchus cloud complex. The data were taken using SCUBA-2/POL-2 on the James Clerk Maxwell Telescope as a part of the BISTRO large program. L43 is a dense (NH 10 22 2 ~ –1023 cm−2) complex molecular cloud with a submillimeter-bright starless core and two protostellar sources. There appears to be an evolutionary gradient along the isolated filament that L43 is embedded within, with the most evolved source closest to the Sco OB2 association. One of the protostars drives a CO outflow that has created a cavity to the southeast. We see a magnetic field that appears to be aligned with the cavity walls of the outflow, suggesting interaction with the outflow. We also find a magnetic field strength of up to ∼160 ± 30 μG in the main starless core and up to ∼90 ± 40 μG in the more diffuse, extended region. These field strengths give magnetically super- and subcritical values, respectively, and both are found to be roughly trans-Alfvénic. We also present a new method of data reduction for these denser but fainter objects like starless cores

Filamentary Network and Magnetic Field Structures Revealed with BISTRO in the High-mass Star-forming Region NGC 2264: Global Properties and Local Magnetogravitational Configurations

We report 850 μm continuum polarization observations toward the filamentary high-mass star-forming region NGC 2264, taken as part of the B-fields In STar forming Regions Observations large program on the James Clerk Maxwell Telescope. These data reveal a well-structured nonuniform magnetic field in the NGC 2264C and 2264D regions with a prevailing orientation around 30° from north to east. Field strength estimates and a virial analysis of the major clumps indicate that NGC 2264C is globally dominated by gravity, while in 2264D, magnetic, gravitational, and kinetic energies are roughly balanced. We present an analysis scheme that utilizes the locally resolved magnetic field structures, together with the locally measured gravitational vector field and the extracted filamentary network. From this, we infer statistical trends showing that this network consists of two main groups of filaments oriented approximately perpendicular to one another. Additionally, gravity shows one dominating converging direction that is roughly perpendicular to one of the filament orientations, which is suggestive of mass accretion along this direction. Beyond these statistical trends, we identify two types of filaments. The type I filament is perpendicular to the magnetic field with local gravity transitioning from parallel to perpendicular to the magnetic field from the outside to the filament ridge. The type II filament is parallel to the magnetic field and local gravity. We interpret these two types of filaments as originating from the competition between radial collapsing, driven by filament self-gravity, and longitudinal collapsing, driven by the region's global gravity

The JCMT BISTRO Survey: Studying the Complex Magnetic Field of L43

We present observations of polarized dust emission at 850 μm from the L43 molecular cloud, which sits in the Ophiuchus cloud complex. The data were taken using SCUBA-2/POL-2 on the James Clerk Maxwell Telescope as a part of the BISTRO large program. L43 is a dense ( NH2∼1022 –1023 cm−2) complex molecular cloud with a submillimeter-bright starless core and two protostellar sources. There appears to be an evolutionary gradient along the isolated filament that L43 is embedded within, with the most evolved source closest to the Sco OB2 association. One of the protostars drives a CO outflow that has created a cavity to the southeast. We see a magnetic field that appears to be aligned with the cavity walls of the outflow, suggesting interaction with the outflow. We also find a magnetic field strength of up to ∼160 ± 30 μG in the main starless core and up to ∼90 ± 40 μG in the more diffuse, extended region. These field strengths give magnetically super- and subcritical values, respectively, and both are found to be roughly trans-Alfvénic. We also present a new method of data reduction for these denser but fainter objects like starless cores

The JCMT BISTRO Survey: A Spiral Magnetic Field in a Hub-filament Structure, Monoceros R2

We present and analyze observations of polarized dust emission at 850 μm toward the central 1 × 1 pc hub-filament structure of Monoceros R2 (Mon R2). The data are obtained with SCUBA-2/POL-2 on the James Clerk Maxwell Telescope (JCMT) as part of the B-fields in Star-forming Region Observations survey. The orientations of the magnetic field follow the spiral structure of Mon R2, which are well described by an axisymmetric magnetic field model. We estimate the turbulent component of the magnetic field using the angle difference between our observations and the best-fit model of the underlying large-scale mean magnetic field. This estimate is used to calculate the magnetic field strength using the Davis–Chandrasekhar–Fermi method, for which we also obtain the distribution of volume density and velocity dispersion using a column density map derived from Herschel data and the C18O (J = 3 − 2) data taken with HARP on the JCMT, respectively. We make maps of magnetic field strengths and mass-to-flux ratios, finding that magnetic field strengths vary from 0.02 to 3.64 mG with a mean value of 1.0 ± 0.06 mG, and the mean critical mass-to-flux ratio is 0.47 ± 0.02. Additionally, the mean Alfvén Mach number is 0.35 ± 0.01. This suggests that, in Mon R2, the magnetic fields provide resistance against large-scale gravitational collapse, and the magnetic pressure exceeds the turbulent pressure. We also investigate the properties of each filament in Mon R2. Most of the filaments are aligned along the magnetic field direction and are magnetically subcritical

Operating characteristics of radiation-hardened silicon pixel detectors for the CMS experiment

The Compact Muon Solenoid (CMS) experiment at the CERN Large Hadron Collider (LHC) will have forward silicon pixel detectors as its innermost tracking device. The pixel devices will be exposed to the harsh radiation environment of the LHC. Prototype silicon pixel detectors have been designed to meet the specification of the CMS experiment. No guard ring is required on the n/sup +/ side, and guard rings on the p/sup +/ side are always kept active before and after type inversion. The whole n/sup +/ side is grounded and connected to readout chips, which greatly simplifies detector assembling and improves the stability of bump-bonded readout chips on the n/sup +/ side. Operating characteristics such as the leakage current, the full depletion voltage, and the potential distributions over guard rings were tested using standard techniques. The tests are discussed in this paper. (9 refs)

Enhanced open circuit voltage by hydrophilic ionic liquids as buffer layer in conjugated polymer-nanoporous titania hybrid solar cells

We demonstrate the fabrication of a nanoporous titania (NP-TiO(2)) network structure by using a polystylene-block-poly(4-vinylpyridine) (PS-b-P4VP) diblock copolymer template and modifying the surface of NP-TiO(2) with ionic liquids (ILs), bmim-BF(4) and benmim-Cl. The effect of the molecular weight of PS-b-P4VP on the morphology of the NP-TiO(2) and IL-modified NP-TiO(2) are characterized by scanning electron microscopy and contact angle measurements. Subsequently, hybrid solar cells are fabricated using MEH-PPV and NP-TiO(2), and the effect of IL layers and IL concentrations on device performances are evaluated under AM 1.5 G illumination. The devices containing bmim-BF(4) and benmim-Cl show drastically enhanced open circuit voltages (V(oc)) of 1.05 V and 0.91 V, respectively, while the reference device without an IL layer exhibits a V(oc) of 0.60 V. Significantly improved V(oc) can be attributed to the change in interfacial energy levels by formation of ionic double layers at the TiO(2)/IL and at the IL/MEH-PPV interfaces. We also observed the trend that short circuit current decreased and V(oc) increased with increasing IL concentration, which is ascribed to interruption of charge transfer from MEH-PPV to TiO(2) and the change in interfacial energy level by shifting the vacuum level, respectively.close121

Phenylethylammonium-formamidinium-methylammonium quasi-2D/3D tin wide-bandgap perovskite solar cell with improved efficiency and stability

Wide bandgap (WBG) Sn perovskite solar cells (PSCs) efficiency enhancement is another sought after field and to resolve the issues related to fast crystallization, trap density and moisture induced oxidation of Sn2+ state in Sn perovskite, we endeavor the benefits of substituting hydrophobic phenylethlammonium (PEA+) cation into WBG PEAxFA0.75MA0.25-xSnI2Br through compositional engineering. We have realized that PEA+ substitution in WBG Sn perovskite led to form 2D/3D mixed perovskite and execute preferential orientation of 3D perovskite planes with controlled crystallinity. Our observation suggests that 2D perovskite phase here helps in merging the grain boundaries and reduce the rate of moisture penetration which ultimately controlled further oxidation of Sn2+. Also, the substitution of PEA+ in WBG Sn perovskite helps in modulating the band energies and aids to efficient electron injection from perovskite to transport layer. Compared to the 3D counterpart, 2D/3D perovskite exhibits slow lifetime decay (ravg = 1.25 ns), suppressed trap state density (1.7 x 1016 cm  3), improved band alignment with slower carrier recombination (r = 1217 mu s) and efficient charge extraction. As compared to FASnI2Br (PCE of 2.38%) and FA0.75MA0.25SnI2Br (PCE of 3.66%), our champion device PCE of 7.96% (Certified PCE of 7.84%) with Jsc of 16.89 mA center dot cm  2, Voc of 0.67 V and FF of 70.36% was achieved for PEA0.15FA0.75MA0.10SnI2Br, which is the highest PCE till date with compositional engineering strategy. The device kept under N2 atmosphere retained nearly original PCE after almost 1500 hrs and air stability of 300 hrs without encapsulation, indicating excellent stability.N