SEPIA345: A 345 GHz dual polarization heterodyne receiver channel for SEPIA at the APEX telescope

Context. We describe the new SEPIA345 heterodyne receiver channel installed at the Atacama Pathfinder EXperiment (APEX) telescope, including details of its configuration, characteristics, and test results on sky. SEPIA345 is designed and built to be a part of the Swedish ESO PI Instrument for the APEX telescope (SEPIA). This new receiver channel is suitable for very high-resolution spectroscopy and covers the frequency range 272- 376 GHz. It utilizes a dual polarization sideband separating (2SB) receiver architecture, employing superconductor-isolator-superconductor mixers (SIS), and provides an intermediate frequency (IF) band of 4- 12 GHz for each sideband and polarization, thus covering a total instantaneous IF bandwidth of 4 \uc3\uc2 - 8 = 32 GHz. Aims. This paper provides a description of the new receiver in terms of its hardware design, performance, and commissioning results. Methods. The methods of design, construction, and testing of the new receiver are presented. Results. The achieved receiver performance in terms of noise temperature, sideband rejection, stability, and other parameters are described. Conclusions. SEPIA345 is a commissioned APEX facility instrument with state-of-the-art wideband IF performance. It has been available on the APEX telescope for science observations since July 2021

A Swedish heterodyne facility instrument for the APEX telescope

In March 2008, the APEX facility instrument was installed on the telescope at the site of Lliano Chajnantor in northern Chile. The main objective of the paper is to introduce the new instrument to the radio astronomical community. It describes the hardware configuration and presents some initial results from the on-sky commissioning. The heterodyne instrument covers frequencies between 211 GHz and 1390 GHz divided into four bands. The first three bands are sideband-separating mixers operating in a single sideband mode and based on superconductor-insulator-superconductor (SIS) tunnel junctions. The fourth band is a hot-electron bolometer, waveguide balanced mixer. All bands are integrated in a closedcycle temperature-stabilized cryostat and are cooled to 4 K. We present results from noise temperature, sideband separation ratios, beam, and stability measurements performed on the telescope as a part of the receiver technical commissioning. Examples of broad extragalactic lines are also included

Analysis, Simulation and Design of Cryogenic Systems for ALMA Band 5 Prototype Cartridge

The ALMA frontend is designed for ten separate receivers channels covering 30-960 GHz range; the receiver accommodates these receiver channels as pluggable, fully electrically autonomous cartridges. These cartridges share the same cryogenic cooler. ALMA Band 5 cartridge is a dual-polarization heterodyne receiver employing 2SB SIS mixers with IF band 4-8 GHz and covers the frequency 163-211 GHz. The prototype for the ALMA Band 5 cartridge development is carried out by Group for Advanced Receiver Development (GARD) in Gothenburg, Sweden with the aim to provide six Band 5 cartridges for ALMA Project. The first prototype cartridge is currently being assembled. ALMA Band 5 cartridge is the lowest frequency channel in the ALMA receiver that employs all cold optics and thus has the biggest rim of the mirrors amongst other ALMA bands placed on the 4K cartridge plate. The size of the optics and its supporting brackets puts severe constrains on the design of the receiver. Another important issue of the Band 5 cartridge design, as well as other ALMA cartridges, is a very tight thermal budget. In this report, we present analysis and simulation results for the thermal and mechanical design of the ALMA Band 5 cartridge that has been carried out using different FEM software packages such as CFDesign and ANSYS. We compare simulation results obtained with these software and the analytical calculations. For the mechanical design, the major focus was put on the cartridge and the optics support structure deformation with cooling

Analysis, Simulation and Design of Cryogenic Systems for ALMA Band 5 Prototype Cartridge

The ALMA frontend is designed for ten separate receivers channels covering 30-960 GHz range; the receiver accommodates these receiver channels as pluggable, fully electrically autonomous cartridges. These cartridges share the same cryogenic cooler. ALMA Band 5 cartridge is a dual-polarization heterodyne receiver employing 2SB SIS mixers with IF band 4-8 GHz and covers the frequency 163-211 GHz. The prototype for the ALMA Band 5 cartridge development is carried out by Group for Advanced Receiver Development (GARD) in Gothenburg, Sweden with the aim to provide six Band 5 cartridges for ALMA Project. The first prototype cartridge is currently being assembled. ALMA Band 5 cartridge is the lowest frequency channel in the ALMA receiver that employs all cold optics and thus has the biggest rim of the mirrors amongst other ALMA bands placed on the 4K cartridge plate. The size of the optics and its supporting brackets puts severe constrains on the design of the receiver. Another important issue of the Band 5 cartridge design, as well as other ALMA cartridges, is a very tight thermal budget. In this report, we present analysis and simulation results for the thermal and mechanical design of the ALMA Band 5 cartridge that has been carried out using different FEM software packages such as CFDesign and ANSYS. We compare simulation results obtained with these software and the analytical calculations. For the mechanical design, the major focus was put on the cartridge and the optics support structure deformation with cooling

Dual Band MM-Wave Receiver for Onsala 20 m Antenna

We present the design and the first light results for the new dual band receiver (4 mm and 3 mm bands) for Onsala Observatory 20 m antenna. For single dish operation, the receiver uses innovative on-source/off-source optical switch. Within the same optical layout, the switch, in combination with additional optical components, provides 2 calibration loads and sideband measurements possibilities. The optics layout of the receiver uses offset elliptical cold mirrors for both channels whereas the on-off switch employs flat mirrors only. The 3 mm channel employs 2SB dual polarization receiver with OMT, 4-8 GHz IF, x 2pol x (USB+LSB). The cryostat has 4 optical widows made of HDPE with anti-reflection corrugations, two for the signal and two for each frequency band cold load. The cryostat employs a two stage cryocooler RDK 408D2 and uses anti-vibration suspension of the cold-head to minimize impact of the vibrations on the receiver stability. The LO system is based on Gunn oscillator with PLL and two mechanical tuners for broadband operation, providing independently tunable LO power for each polarization. At the conference, we will present details on the receiver optics, cryostat design and the result of the first on-sky observations

Dual Band MM-Wave Receiver for Onsala 20 m Antenna

We present the design and the first light results for the new dual band receiver (4 mm and 3 mm bands) for Onsala Observatory 20 m antenna. For single dish operation, the receiver uses innovative on-source/off-source optical switch. Within the same optical layout, the switch, in combination with additional optical components, provides 2 calibration loads and sideband measurements possibilities. The optics layout of the receiver uses offset elliptical cold mirrors for both channels whereas the on-off switch employs flat mirrors only. The 3 mm channel employs 2SB dual polarization receiver with OMT, 4-8 GHz IF, x 2pol x (USB+LSB). The cryostat has 4 optical widows made of HDPE with anti-reflection corrugations, two for the signal and two for each frequency band cold load. The cryostat employs a two stage cryocooler RDK 408D2 and uses anti-vibration suspension of the cold-head to minimize impact of the vibrations on the receiver stability. The LO system is based on Gunn oscillator with PLL and two mechanical tuners for broadband operation, providing independently tunable LO power for each polarization. At the conference, we will present details on the receiver optics, cryostat design and the result of the first on-sky observations

New optics for SEPIA- Heterodyne facility instrument for the APEX telescope

The design of SEPIA (Swedish ESO PI Instrument for APEX) was driven by the idea of using ALMA receiver cartridges on the APEX telescope. SEPIA was installed at the guest position of the Naismith cabin A, APEX telescope in early 2015. The SEPIA cryostat and optics was designed to accommodate up to 3 ALMA cartridges. In 2017, the APEX facility instrument SHeFI was decommissioned and SEPIA was accepted as its successor. Moving SEPIA from its PI into Facility Instrument position brought additional constrains due to the severe limitations of the available space. That had led to the necessity of complete redesigning of the SEPIA tertiary optics. During February-March 2019, the new tertiary optics was installed in the APEX Cabin A and SEPIA was placed at its final Facility Instrument position. Here, we present the details of the optical design, layout of the optical component placement, the beam alignment technique, the results of the alignment and SEPIA technical commissioning results at the APEX telescope

Beyond-Decade Ultrawideband Quad-Ridge Flared Horn With Dielectric Load From 1 to 20 GHz

In this article, we present a novel dielectrically loaded quad-ridge flared horn (QRFH) as a reflector feed with beyond-decade ultrawideband performance. The dielectric is machined in a low-loss, space-grade polyimide specified with low outgassing for a vacuum environment. The feed covers 1–20 GHz bandwidth with a measured band-average input reflection of −13.6 and 41.5 dB isolation between two orthogonal polarized ports. Predicted performance in a paraboloidal reflector with a 60\ub0 half-subtended angle is 62% aperture efficiency average over the band. The ridges of the horn are designed with analytic-spline-hybrid 3-D profiles with thickness flaring outwards toward the feed aperture, improving low-frequency polarization properties. The QRFH was manufactured in four quarters for accurate ridge-to-ridge alignment and a reduced number of interfaces for good thermal properties in cryogenic applications. A prototype feed has been installed and tested with promising results in one of the 6 m offset Gregorian reflectors of the Allen Telescope Array (ATA) located at the Hat Creek Observatory, Hat Creek, CA, USA

Fetal cardiac function at intrauterine transfusion assessed by automated analysis of color tissue Doppler recordings

Background: Fetal anemia is associated with a hyperdynamic circulation and cardiac remodeling. Rapid intrauterine transfusion (IUT) of blood with high hematocrit and viscosity into the umbilical vein used to treat this condition can temporarily further affect fetal heart function. The aim of this study was to evaluate the short-term changes in fetal myocardial function caused by IUT using automated analysis of cine-loops of the fetal heart obtained by color tissue Doppler imaging (cTDI). Methods: Fetal echocardiography was performed before and after IUT. cTDI recordings were obtained in a fourchamber view and regions of interest were placed at the atrioventricular plane in the left ventricular (LV), right ventricular (RV) and septal walls. Myocardial velocities were analyzed by an automated analysis software to obtain peak myocardial velocities during atrial contraction (Am), ventricular ejection (Sm), rapid ventricular filling (Em) and Em/Am ratio was calculated. Myocardial velocities were converted to z-scores using published reference ranges. Delta z-scores (after minus before IUT) were calculated. Correlations were assessed between variables and hemoglobin before IUT. Results: Thirty-two fetuses underwent 70 IUTs. Fourteen were first time transfusions. In the LV and septal walls, all myocardial velocities were significantly increased compared to normal values, whereas in the RV only Sm was increased before IUT (z-scores 0.26–0.52). In first time IUTs, there was a negative correlation between LV Em (rho = − 0.61, p = 0.036) and LV Em/Am (rho = − 0.82, p = 0.001) z-scores and hemoglobin before IUT. The peak myocardial velocities that were increased before IUT decreased, whereas LV Em/Am increased significantly after IUT. Conclusions: This study showed that peak myocardial velocities assessed by cTDI are increased in fetuses before IUT reflecting the physiology of hyperdynamic circulation. In these fetuses, the fetal heart is able to adapt and efficiently handle the volume load caused by IUT by altering its myocardial function

Automated analysis of fetal cardiac function using color tissue Doppler imaging in second half of normal pregnancy

Objectives - Color tissue Doppler imaging (cTDI) is a promising tool for the assessment of fetal cardiac function. However, the analysis of myocardial velocity traces is cumbersome and time‐consuming, limiting its application in clinical practice. The aim of this study was to evaluate fetal cardiac function during the second half of pregnancy and to develop reference ranges using an automated method to analyze cTDI recordings from a cardiac four‐chamber view. Methods - This was a cross‐sectional study including 201 normal singleton pregnancies between 18 and 42 weeks of gestation. During fetal echocardiography, a four‐chamber view of the heart was visualized and cTDI was performed. Regions of interest were positioned at the level of the atrioventricular plane in the left ventricular (LV), right ventricular (RV) and septal walls of the fetal heart, to obtain myocardial velocity traces that were analyzed offline using the automated algorithm. Peak myocardial velocities during atrial contraction (Am), ventricular ejection (Sm) and rapid ventricular filling, i.e. early diastole (Em), as well as the Em/Am ratio, mechanical cardiac time intervals and myocardial performance index (cMPI) were evaluated, and gestational age‐specific reference ranges were constructed. Results - At 18 weeks of gestation, the peak myocardial velocities, presented as fitted mean with 95% CI, were: LV Am, 3.39 (3.09–3.70) cm/s; LV Sm, 1.62 (1.46–1.79) cm/s; LV Em, 1.95 (1.75–2.15) cm/s; septal Am, 3.07 (2.80–3.36) cm/s; septal Sm, 1.93 (1.81–2.06) cm/s; septal Em, 2.57 (2.32–2.84) cm/s; RV Am, 4.89 (4.59–5.20) cm/s; RV Sm, 2.31 (2.16–2.46) cm/s; and RV Em, 2.94 (2.69–3.21) cm/s. At 42 weeks of gestation, the peak myocardial velocities had increased to: LV Am, 4.25 (3.87–4.65) cm/s; LV Sm, 3.53 (3.19–3.89) cm/s; LV Em, 4.55 (4.18–4.94) cm/s; septal Am, 4.49 (4.17–4.82) cm/s; septal Sm, 3.36 (3.17–3.55) cm/s; septal Em, 3.76 (3.51–4.03) cm/s; RV Am, 6.52 (6.09–6.96) cm/s; RV Sm, 4.95 (4.59–5.32) cm/s; and RV Em, 5.42 (4.99–5.88) cm/s. The mechanical cardiac time intervals generally remained more stable throughout the second half of pregnancy, although, with increased gestational age, there was an increase in duration of septal and RV atrial contraction, LV pre‐ejection and septal and RV ventricular ejection, while there was a decrease in duration of septal postejection. Regression equations used for the construction of gestational age‐specific reference ranges for peak myocardial velocities, Em/Am ratios, mechanical cardiac time intervals and cMPI are presented. Conclusion - Peak myocardial velocities increase with gestational age, while the mechanical time intervals remain more stable throughout the second half of pregnancy. Using an automated method to analyze cTDI‐derived myocardial velocity traces, it was possible to construct reference ranges, which could be used in distinguishing between normal and abnormal fetal cardiac function