A Transmissive X-ray Polarimeter Design For Hard X-ray Focusing Telescopes

The X-ray Timing and Polarization (XTP) is a mission concept for a future space borne X-ray observatory and is currently selected for early phase study. We present a new design of X-ray polarimeter based on the time projection gas chamber. The polarimeter, placed above the focal plane, has an additional rear window that allows hard X-rays to penetrate (a transmission of nearly 80% at 6 keV) through it and reach the detector on the focal plane. Such a design is to compensate the low detection efficiency of gas detectors, at a low cost of sensitivity, and can maximize the science return of multilayer hard X-ray telescopes without the risk of moving focal plane instruments. The sensitivity in terms of minimum detectable polarization, based on current instrument configuration, is expected to be 3% for a 1mCrab source given an observing time of 10^5 s. We present preliminary test results, including photoelectron tracks and modulation curves, using a test chamber and polarized X-ray sources in the lab

Enhanced electrical and thermal conductivities of 3D-SiC(rGO, G x ) PDCs based on polycarbosilane-vinyltriethoxysilane-graphene oxide (PCS-VTES-GO) precursor containing graphene fillers

Abstract(#br)Lightweight 3D-SiC(rGO, G x ) PDCs were fabricated from polycarbosilane-vinyltriethoxysilane-graphene oxide (PCS-VTES-GO) precursor added by different amounts of graphene fillers via direct cold molding and pyrolysis at 1400 °C in an easy manner. Results reveal that SiC(rGO, G x ) PDCs consist of β-SiC nanocrystals homogeneously embedded within amorphous SiO x C y /C free , and graphene is well compatible with SiO x C y /C free for void-free bonded interface, efficiently delaying decomposition of SiO x C y phase into β-SiC. The nanocomposite structure provides an ingenious strategy for constructing complexes with good integrity, high ceramic yield, excellent thermal stability, high electrical and thermal conductivities. This improvement is primarily attributed to the presence of graphene with considerably increasing electric-charge carriers and wider phonon-channel. Such 3D-SiC(rGO, G 20% ) PDCs possess satisfying hardness (12.02 GPa), high electrical conductivity (23.82 S cm −1 ) and thermal conductivity (7.47 W m −1 K −1 ), which make them attractive candidates for microelectromechanical systems (MEMS) devices, energy storage/conversion systems and high precision components, etc

Insight-HXMT observations of Swift J0243.6+6124 during its 2017-2018 outburst

The recently discovered neutron star transient Swift J0243.6+6124 has been monitored by {\it the Hard X-ray Modulation Telescope} ({\it Insight-\rm HXMT). Based on the obtained data, we investigate the broadband spectrum of the source throughout the outburst. We estimate the broadband flux of the source and search for possible cyclotron line in the broadband spectrum. No evidence of line-like features is, however, found up to $\rm 150~keV$. In the absence of any cyclotron line in its energy spectrum, we estimate the magnetic field of the source based on the observed spin evolution of the neutron star by applying two accretion torque models. In both cases, we get consistent results with $B\rm \sim 10^{13}~G$, $D\rm \sim 6~kpc$ and peak luminosity of $\rm >10^{39}~erg~s^{-1}$ which makes the source the first Galactic ultraluminous X-ray source hosting a neutron star.Comment: publishe

Overview to the Hard X-ray Modulation Telescope (Insight-HXMT) Satellite

As China's first X-ray astronomical satellite, the Hard X-ray Modulation Telescope (HXMT), which was dubbed as Insight-HXMT after the launch on June 15, 2017, is a wide-band (1-250 keV) slat-collimator-based X-ray astronomy satellite with the capability of all-sky monitoring in 0.2-3 MeV. It was designed to perform pointing, scanning and gamma-ray burst (GRB) observations and, based on the Direct Demodulation Method (DDM), the image of the scanned sky region can be reconstructed. Here we give an overview of the mission and its progresses, including payload, core sciences, ground calibration/facility, ground segment, data archive, software, in-orbit performance, calibration, background model, observations and some preliminary results.Comment: 29 pages, 40 figures, 6 tables, to appear in Sci. China-Phys. Mech. Astron. arXiv admin note: text overlap with arXiv:1910.0443

Performance of Vacuum Pumps in Dental Evacuation Systems

A study was conducted to compare and assess the performance of various vacuum pumps in small and large dental clinic operations. A four-chair dental clinic operation was set up at the laboratory to simulate a small dental clinic environment. The performance of two dry and two wet pumps was assessed in the laboratory via extensive performance data acquisition tests. Data were also iv collected in two small dental clinics of practicing dentists in Brookings, SD. Large dental system performance tests were conducted at the Ellsworth Air Force Base and Minot Air Force Base dental clinics. At each clinic, data were collected with both the existent turbine pump and a RAMVAC pump. In addition to the performance test conducted, data were also collected at the university setup to document pressure losses and pressure loss coefficients for all pertinent dental treatment room hoses and fittings. In addition, pressure losses for some PVC elbows used in dental plumbing systems were measured at the laboratory. Finally, friction head losses in straight PVC piping were calculated and documented in graphical and tabular form. These calculated values were compared with measured experimental data

Effects of TCP and creep cavity on creep life in the rafting regime for Ru-containing Nickel-based single crystal superalloys

Ru is crucial in improving creep properties in Nickel-based single-crystal superalloys. The effect of Ru content on the creep behavior of nickel-based single-crystal superalloy was studied. Ru exhibits unprecedented mechanical properties, increasing the creep life at 1120 °C but decreasing it at 1180 °C. This is due to the competition in the stress concentration formed between the topologically close-packed phases and the creep cavity. They are both related to the dissociation of the γ′ phase. The effect of oxidation caused by the addition of Ru is lower than these two factors. This work helps to recognize the comprehensive effect of Ru and can provide guidance for alloy design in the future