[en] Here, the Cosmology Large Angular Scale Surveyor (CLASS) is mapping the polarization of the cosmic microwave background (CMB) at large angular scales (2 < ℓ ≲ 200) in search of a primordial gravitational wave B-mode signal down to a tensor-to-scalar ratio of r ≈ 0.01. The same data set will provide a near sample-variance-limited measurement of the optical depth to reionization. Between 2016 June and 2018 March, CLASS completed the largest ground-based Q-band CMB survey to date, covering over 31,000 square-degrees (75% of the sky), with an instantaneous array noise-equivalent temperature sensitivity of $32\mathrm{\mu <!--\; ??\; -->}{\mathrm{K}}_{\mathrm{c}\mathrm{m}\mathrm{b}}\sqrt{\mathrm{s}}$. Thus, we demonstrate that the detector optical loading (1.6 pW) and noise-equivalent power (19 $\mathrm{a}\mathrm{W}\sqrt{\mathrm{s}}$) match the expected noise model dominated by photon bunching noise. We derive a 13.1 ± 0.3 K pW^–1 calibration to antenna temperature based on Moon observations, which translates to an optical efficiency of 0.48 ± 0.02 and a 27 K system noise temperature. Finally, we report a Tau A flux density of 308 ± 11 Jy at 38.4 ± 0.2 GHz, consistent with the Wilkinson Microwave Anisotropy Probe Tau A time-dependent spectral flux density model.

[en] The crystal structures of metallic V(bcc) and its hydrides VH_x(0≤x≤2) are calculated. The optimized crystal structures and total energies of them are obtained. The phase transitions of V-H system with enhancement of hydrogen content in the cell are discussed. The calculated and experimental results are in agreement very well

[en] Based on XRD analysis of La-Ni-Al alloys, their cell parameters and volumes were worked out, space group was determined to be P6/mmm by using powder indexing program in Cerius 2.0 code. Absorbing and disrobing hydrogen properties of La-Ni-Al alloys were investigated, their absorbing capacities, basic thermodynamics ΔH⁰ and ΔS⁰ were tested, the relationship between properties and structure was obtained

[en] An initial calculation have been performed to study the crystal structures of V(bcc) and its hydrides VH_x(0≤x≤2). The optimized crystal structures and total energies are obtained. The stability of hydrides and phase transitions of V-H system and discussed with enhancement of hydrogen concentration in the cell. The calculation results are in remarkably close agreement with experiments

[en] Behaviors of hydrogen absorption-desorption and other application-oriented properties of the Ti_1.08V_1.21Cr_0.28Fe_0.40Zr_0.03 alloy were investigated. The results showed that the alloy was activated easily and had a large hydrogen absorbing content. The plateau pressure at ambient temperature was about 101325 Pa with hydrogen content about 0.8 H/M-1.6 H/M. The thermodynamic parameters of the reaction of hydrogen absorption for the hydride with H/M = 1.25 were found to be ΔH = -27.4 kJ/moleH₂ and ΔS = -200 j/(K·moleH₂). The hydrogen absorption and desorption reaction were fast. The hydrogen desorption ratio of the alloy hydride at 600 degree C was above 95 percent. The impurity helium had little effect on the hydrogen absorbing volume, but reduced the reaction rate obviously. While the air had obvious effects both on the absorbing volume and the reaction rate. The alloy resisted pulverization and the relative volume change of the hydride with H/M = 1.1 was only about 11 percent. And the alloy and its hydride did not self-ignite in air. Phase composition of the Ti_1.08V_1.21Cr_0.28Fe_0.40Zr_0.03 alloy and its hydride were analysed by XRD and Sem. The result showed that a multi-phase formed after hydriding

[en] The initial absorbing rate at different temperature, the P-C-T curves and the relation between equilibrium pressure and temperature of deuterium absorption and desorption of ZrV₂ are measured. And then the thermodynamic parameters of the two processes are determined according to Van't Hoff equation. Also, the deuterium absorption capacity and the equilibrium pressure of the absorption and desorption at room temperature of ZrV₂ are given

[en] ZrV₂ is prepared by arc melting and heat treatment. The phases of the alloy prepared only by arc melting and the one by both arc melting and heat treatment are analyzed according to ASTM files and the XRD spectrogram of ZrV₂ C15 type Laves-phase simulated by Cerius 2.0. It is proved that the sample prepared only by arc melting includes many phases, and the one by both processes is single ZrV₂ phase. No solid solutions phase is seen in the latter

[en] A simpler and refined version of effective-medium theory is adopted to calculate the fundamental energy properties of single helium atom in some metals. In this version, the relaxation effects of lattice have been taken into account. The calculated results of some typical energy values agree well with available experimental and other theoretical values

[en] The Cosmology Large Angular Scale Surveyor (CLASS) is a telescope array that observes the cosmic microwave background (CMB) over 75% of the sky from the Atacama Desert, Chile, at frequency bands centered near 40, 90, 150, and 220 GHz. CLASS measures the large angular scale (1° ≲ θ $⩽<!--\; ???\; -->$ 90°) CMB polarization to constrain the tensor-to-scalar ratio at the r ∼ 0.01 level and the optical depth to last scattering to the sample variance limit. This paper presents the optical characterization of the 40 GHz telescope during its first observation era, from 2016 September to 2018 February. High signal-to-noise observations of the Moon establish the pointing and beam calibration. The telescope boresight pointing variation is <0.°023 (<1.6% of the beam’s full width at half maximum (FWHM)). We estimate beam parameters per detector and in aggregate, as in the CMB survey maps. The aggregate beam has an FWHM of 1.°579 ± 0.°001 and a solid angle of 838 ± 6 μsr, consistent with physical optics simulations. The corresponding beam window function has a sub-percent error per multipole at ℓ < 200. An extended 90° beam map reveals no significant far sidelobes. The observed Moon polarization shows that the instrument polarization angles are consistent with the optical model and that the temperature-to-polarization leakage fraction is <10⁻⁴ (95% C.L.). We find that the Moon-based results are consistent with measurements of M42, RCW 38, and Tau A from CLASS’s CMB survey data. In particular, Tau A measurements establish degree-level precision for instrument polarization angles.

[en] The Simons Observatory is a ground-based cosmic microwave background experiment that consists of three 0.4 m small-aperture telescopes and one 6 m Large Aperture Telescope, located at an elevation of 5300 m on Cerro Toco in Chile. The Simons Observatory Large Aperture Telescope Receiver (LATR) is the cryogenic camera that will be coupled to the Large Aperture Telescope. The resulting instrument will produce arcminute-resolution millimeter-wave maps of half the sky with unprecedented precision. The LATR is the largest cryogenic millimeter-wave camera built to date, with a diameter of 2.4 m and a length of 2.6 m. The coldest stage of the camera is cooled to 100 mK, the operating temperature of the bolometric detectors with bands centered around 27, 39, 93, 145, 225, and 280 GHz. Ultimately, the LATR will accommodate 13 40 cm diameter optics tubes, each with three detector wafers and a total of 62,000 detectors. The LATR design must simultaneously maintain the optical alignment of the system, control stray light, provide cryogenic isolation, limit thermal gradients, and minimize the time to cool the system from room temperature to 100 mK. The interplay between these competing factors poses unique challenges. We discuss the trade studies involved with the design, the final optimization, the construction, and ultimate performance of the system.