Centimeter-Wave Reflection in the Nitrates and Nitrites of Sodium and Potassium: Experiment and Theory

Temperature-dependent centimeter-wave reflection is studied in powdered samples of potassium nitrate (KNO3), potassium nitrite (KNO2), sodium nitrate (NaNO3), and sodium nitrite (NaNO2). Temperature-dependent reflection measurements at centimeter-wave frequencies were performed on an HP8510B Network analyzer based reflectometer. These measurements are compared to calculations utilizing a Debye relaxation model. Reflection losses seen in KNO2 and NaNO2 are expected to be due to the presence of permanent dipoles that are excited to ‘‘hopping’’ modes as the temperature is raised. Although NaNO3 shows little reflection losses, KNO3 shows significant losses as the temperature is raised toward the order/disorder transition temperature of 128 °C. This is believed to be due to the development of ‘‘induced’’ dipole moments as the lattice becomes increasingly disordered

Receiver development for BICEP Array, a next-generation CMB polarimeter at the South Pole

A detection of curl-type (B-mode) polarization of the primary CMB would be direct evidence for the inflationary paradigm of the origin of the Universe. The Bicep/Keck Array (BK) program targets the degree angular scales, where the power from primordial B-mode polarization is expected to peak, with ever-increasing sensitivity and has published the most stringent constraints on inflation to date. Bicep Array (BA) is the Stage-3 instrument of the BK program and will comprise four Bicep3-class receivers observing at 30/40, 95, 150 and 220/270 GHz with a combined 32,000+ detectors; such wide frequency coverage is necessary for control of the Galactic foregrounds, which also produce degree-scale B-mode signal. The 30/40 GHz receiver is designed to constrain the synchrotron foreground and has begun observing at the South Pole in early 2020. By the end of a 3-year observing campaign, the full Bicep Array instrument is projected to reach σr between 0.002 and 0.004, depending on foreground complexity and degree of removal of B-modes due to gravitational lensing (delensing). This paper presents an overview of the design, measured on-sky performance and calibration of the first BA receiver. We also give a preview of the added complexity in the time-domain multiplexed readout of the 7,776-detector 150 GHz receiver

Polarization calibration of the BICEP3 CMB polarimeter at the South Pole

The BICEP3 CMB Polarimeter is a small-aperture refracting telescope located at the South Pole and is specifically designed to search for the possible signature of inflationary gravitational waves in the Cosmic Microwave Background (CMB). The experiment measures polarization on the sky by differencing the signal of co-located, orthogonally polarized antennas coupled to Transition Edge Sensor (TES) detectors. We present precise measurements of the absolute polarization response angles and polarization efficiencies for nearly all of BICEP3's ~800 functioning polarization-sensitive detector pairs from calibration data taken in January 2018. Using a Rotating Polarized Source (RPS), we mapped polarization response for each detector over a full 360 degrees of source rotation and at multiple telescope boresight rotations from which per-pair polarization properties were estimated. In future work, these results will be used to constrain signals predicted by exotic physical models such as Cosmic Birefringence

Analysis of Temperature-to-Polarization Leakage in BICEP3 and Keck CMB Data from 2016 to 2018

The Bicep/Keck Array experiment is a series of small-aperture refracting telescopes observing degree-scale Cosmic Microwave Background polarization from the South Pole in search of a primordial B-mode signature. As a pair differencing experiment, an important systematic that must be controlled is the differential beam response between the co-located, orthogonally polarized detectors. We use high-fidelity, in-situ measurements of the beam response to estimate the temperature-to-polarization (T → P) leakage in our latest data including observations from 2016 through 2018. This includes three years of Bicep3 observing at 95 GHz, and multifrequency data from Keck Array. Here we present band-averaged far-field beam maps, differential beam mismatch, and residual beam power (after filtering out the leading difference modes via deprojection) for these receivers. We show preliminary results of "beam map simulations," which use these beam maps to observe a simulated temperature (no Q/U) sky to estimate T → P leakage in our real data

Observing low elevation sky and the CMB Cold Spot with BICEP3 at the South Pole

BICEP3 is a 520 mm aperture on-axis refracting telescope at the South Pole, which observes the polarization of the cosmic microwave background (CMB) at 95 GHz to search for the B-mode signal from inflationary gravitational waves. In addition to this main target, we have developed a low-elevation observation strategy to extend coverage of the Southern sky at the South Pole, where BICEP3 can quickly achieve degree-scale E-mode measurements over a large area. An interesting E-mode measurement is probing a potential polarization anomaly around the CMB Cold Spot. During the austral summer seasons of 2018-19 and 2019-20, BICEP3 observed the sky with a flat mirror to redirect the beams to various low elevation ranges. The preliminary data analysis shows degree-scale E-modes measured with high signal-to-noise ratio

Analysis of Temperature-to-Polarization Leakage in BICEP3 and Keck CMB Data from 2016 to 2018

The Bicep/Keck Array experiment is a series of small-aperture refracting telescopes observing degree-scale Cosmic Microwave Background polarization from the South Pole in search of a primordial B-mode signature. As a pair differencing experiment, an important systematic that must be controlled is the differential beam response between the co-located, orthogonally polarized detectors. We use high-fidelity, in-situ measurements of the beam response to estimate the temperature-to-polarization (T → P) leakage in our latest data including observations from 2016 through 2018. This includes three years of Bicep3 observing at 95 GHz, and multifrequency data from Keck Array. Here we present band-averaged far-field beam maps, differential beam mismatch, and residual beam power (after filtering out the leading difference modes via deprojection) for these receivers. We show preliminary results of "beam map simulations," which use these beam maps to observe a simulated temperature (no Q/U) sky to estimate T → P leakage in our real data

Observing low elevation sky and the CMB Cold Spot with BICEP3 at the South Pole

BICEP3 is a 520 mm aperture on-axis refracting telescope at the South Pole, which observes the polarization of the cosmic microwave background (CMB) at 95 GHz to search for the B-mode signal from inflationary gravitational waves. In addition to this main target, we have developed a low-elevation observation strategy to extend coverage of the Southern sky at the South Pole, where BICEP3 can quickly achieve degree-scale E-mode measurements over a large area. An interesting E-mode measurement is probing a potential polarization anomaly around the CMB Cold Spot. During the austral summer seasons of 2018-19 and 2019-20, BICEP3 observed the sky with a flat mirror to redirect the beams to various low elevation ranges. The preliminary data analysis shows degree-scale E-modes measured with high signal-to-noise ratio

MAGNETIC AND ELECTRONIC PROPERTIES OF RARE-EARTH-RICH METALLIC GLASSES

Results of magnetic measurements are presented on the new metallic glass systems (R(,80)G(,20))(,100-x)Fe(,x) and (R(,80)Ga(,20))(,90)B(,10), where R is a rare-earth (i.e., La, Pr, Nd, Sm, Gd, Tb and Er) and G is Ga or Au for 0 (LESSTHEQ) x (LESSTHEQ) 30. High-field magnetization (to 80 kOe) and A.C. and D.C. susceptibility measurements were made from 1.4 K to 300 K. High-field magnetization data are analyzed by an Arrott plot technique and some Gd-based glasses show results consistent with the presence of the recently predicted infinite susceptibility phase of Aharony and Pytte. The magnetic hardness properties of most of these glasses (not containing S-state ions) are discussed in terms of the \u27microdomain\u27 model of Callen et al. In many glasses the magnetization reversal seems consistent with a coherent rotation mechanism as is suggested from the thermal variation of the coercivity. The glasses (R(,80)Ga(,20))(,70)Fe(,30) where R is Er and Tb are more complex and show behavior consistent with the presence of domain walls. Magnetic saturation was not obtained (at 80 kOe) on any glass containing an anisotropic rare-earth while glasses based on S-state rare-earths were fairly easily saturated. Giant intrinsic magnetic hardness is observed in the glasses (R(,80)G(,20))(,100-x)Fe(,x) where R is Nd or Pr and G is Ga or Au for 15 (LESSTHEQ) x (LESSTHEQ) 30. An unusual thermal variation of the coercive field is observed showing peaks at intermediate temperatures ((DBLTURN) 90 K). A phase separation into different amorphous stoichiometries is shown to exist by Fe(\u2757) Mossbauer effect and other measurements. These results are consistent with a recent theory by Paul predicting that magnetic hardness can result from the presence of site-to-site variations in magnetic properties. Electrical resistivity measurements were made on the above glasses as well as the series (Pr(,80)Ga(,20))(,80)T(,20), where T = Cr, Mn, Co, Ni, Cu and Ga. These show negative temperature coefficients of resistivity at higher temperatures in most cases as well as structure in the resistivity below magnetic ordering temperatures. These results are shown to be consistent with some recent theories (for instance the extended Ziman theory) predicting negative slopes of the resistivity as well as to some theories predicting a magnetic contribution to the resistivity from coherent exchange scattering