The Submillimeter Array



Receiver Lab Talks: 2022


Questions: Edward Tong
Time: Wednesday 1:00 PM EST/EDT
Where: Zoom

Date Speaker Title Summary
Jan 19John Garrett
SMA
SIS Biasing Electronics for the wSMA In this talk, I will present my recent work on the SIS bias sub-system for the wSMA. The SIS bias requires careful component selection, tuning and filtering in order to acquire a high fidelity I-V curve. I now have a working prototype that is ready for production and I will present the final design.
Jan 26Alan Rogers
Haystack Observatory
EDGES-3: A spectrometer with automated calibration built into the antenna for observations of the 21-cm line The EDGES-3 system is a spectrometer with all the electronics built into the dipole antenna. A prototype was tested in Oregon in 2019 and a second EDGES-3 system of the same design was completed in 2021 for deployment at the MRO or a new site in the Northern hemisphere. The absolute calibration of EDGES-3 is completely automated using computer controlled low loss mechanical switches along with built in hot, ambient, open and shorted cables. Tests show that the highest accuracy reques taking VNA S11 data for a sufficient time to allow for the VNA electronics to warm up, which changes with the VNA operating mode and output power level to ensure minimal drift between measurements. Tests of the repeatability of the new system and the difference between the new system and the prototype are less than 10 mK rms to a 5-term fit using a noise source as an artificial antenna simulator. A search for a suitable site in the Northern hemipshere is underway with the goal of strengthening the case that the absorption feature reported in Nature 2018 from EDGES-2 at the MRO in the Southern hemisphere is global and not instrumental or the result of RFI.
Feb 2Miranda Eiben
Harvard University
Thin Laminate Polyethylene Windows for Large Millimeter Receivers As cryogenic receiver aperture sizes grow, vacuum windows for millimeter receivers must either get thicker or stronger. We have developed a lamination technique to generate thin windows using High Modulus Polyethylene (HMPE), decreasing the required thickness for a window to less than a wavelength at 95 and 150 GHz. This talk will discuss the manufacturing and characterization of the laminate vacuum windows, with both measurements and predictions of mechanical and optical properties.
Feb 16Dan Marrone
University of Arizona
Progress on millimeterwave intensity mapping Line intensity mapping (LIM) is a tool to study the growth of structure in the universe by observing the power spectrum of line emission over large cosmic volumes. The first generation of millimeter/submillimeter LIM experiments are just reaching the telescope. I will talk about technical issues and progress on two of these. First, the Tomographic Ionized-carbon Mapping Experiment (TIME) has just completed an engineering run on the 12 m telescope on Kitt Peak, and I will describe the instrument and show some first light images. Second, the Terahertz Intensity Mapper (TIM) is a NASA balloon mission that will launch from Antarctica in 2024, and I will show the current status of the mission and its key technologies.
Feb 23Edward Tong
SMA
Vacuum Window and Infrared Filter for wSMA Cryostat In this talk, I will describe the development and performance of both the vacuum window and the infrared filter for the new wSMA cryostat. The clear apertures of the vacuum window and the infrared filter have diameters of 107 and 95 mm respectively, and both elements are designed to offer very low insertion loss between 200 and 370 GHz. I will also give an update on the testing of the wSMA receivers.
March 2Douglas Henke
Herzberg Astronomy & Astrophysics Researcg Centre, NRC
Focal Plane Array Concept for 2SB Receivers Focal plane arrays (FPAs) are important for single-dish facilities to increase the field-of-view and overall mapping speed. It is advantageous to develop a focal plane layout that can accommodate dual-polarization and sideband separating (2SB) receivers to maintain compatibility with existing facilities. I will present a conceptual design that uses a "unit cell" approach for the front-end 2SB block using waveguide. Each pixel uses a turnstile OMT for linear polarization, magic-tees for isolated power division and higher mode termination, and hole couplers for LO injection. A 5-layer quasi-platelet layout is used such that the "unit cell" may be replicated to facilitate arrayed designs.
March 16Paul Grimes
CfA
Measuring millimeter-wave optical material properties The CMB-S4 Small Aperture Telescopes will be cryogenic refracting telescopes covering the 20 to 300 GHz bands with a common optical design across several bands. To optimize, construct and verify the performanace of the instruments, we need to make measurements, throughout the millimeter-wave band, of the refractive index, absorption loss, scattering and birefringence of a variety of optical materials at both room and cryogenic temperatures. I will review a number of techniques for making these measurements and identify which seem most promising for the different steps in the CMB-S4 project.
March 23Victor Belitsky
Chalmers University, Sweden
Receiver Developments for OSO, APEX and ALMA In this talk, I will give an introduction and a d escription of the GARD (instrumentation group of the Onsala Space Observatory (OSO). I will provide a short summary of the telescopes we work with, including the 20 m OSO, 12 m APEX telescope as well as the current and past works we do for ALMA. Thereafter, I will talk about our plans and work on new receivers for the OSO, APEX and ALMA. Note: some of the results are preliminary or not yet published and I ask for considerations from the audience.
April 6John Garrett & Edward Tong
CfA
wSMA High Band SIS Mixer Testing and Estimation of IF noise in SIS Receivers In the first part of this talk, we will report the experimental results of two different SIS devices operating at LO frequencies between 280 and 350 GHz. The first device is the 3-junction mixer designed for the wSMA high-band receiver and the other is a 1-junction device optimized for the 2SB prototype. In the second part of the talk, we will look at the method of estimating the IF noise temperature of SIS receivers using the SIS junction as a shot noise source.
April 20Derek Kubo
SMA/ASIAA
IF Subsystem for wSMA In this talk, I will present the architecture of the IF subsystem which will handle the IF output of the new wSMA receivers. There will be two separate frequency channels: 0-4" GHz and 4-16 GHz which are transmitted over fiber using wavelength multiplexing. Preliminary test data will be provided.
May 4Ranjani Srinivasan
CfA
SAO VLBI Digital Back End Development I will present the current status of the development for the Block Down Converter (BDC) and the Digital Back-End (DBE) for the next generation Event Horizon Telescope. The BDC uses MMIC technology, and a prototype has passed design review and is currently under development. The ADC used is the single core 4 bit Adsantec 7123A. The VCU128 evaluation FPGA kit is being used to develop the firmware. I will present some essential metrics for the above ADC, sampling at 16.384 Gsps. A brief overview of the firmware requirements and the current status will be provided. Finally, the motivation to design an in house integrated ADC/FPGA board will be presented.
June 29John Garrett
CfA
A 345-GHz 2SB Prototype with Wide IF Bandwidth In this talk, we will present the recent experimental results from the 345-GHz 2SB prototype. A distinguishing feature of this prototype is that we have the IF hybrid outside the cryostat, allowing us to use a wide-bandwidth off-the-shelf hybrid. Using a 1-junction SIS device, we measure a single-side-band noise temperature of 94+/-7 K and an image rejection ratio of > 13 dB for 85% of the bandwidth (LO: 325-350 GHz; IF 4-13 GHz). The results from the 2SB prototype with 3-junction wSMA High-Band device will also be presented, which has a wider IF bandwidth.
July 27Seijiro Yoshihara
UMass Lowell
A Brief Introduction to 3-D Printing and its Application to Radio-astronomical Development In this talk, I will give a brief introduction to 3-D printing technology: its history, the different types of machines and materials in common use. Since 3-D printers can be used to produce objects with complex geometries, they are very useful for prototype development. I will give some examples of objects used in the wSMA instrumentation development, which we have produced in the Receiver Lab with a simple 3-D printer.
Aug 3Lorenzo Russotto
Harvard University
A search for the optimal illumination of an optically controlled silicon chip attenuator In this talk, I will present our project of improving the performance of the 220-330 GHz silicon chip attenuator, employed in the Local Oscillator of the wSMA receiver under development. After a brief review of the principles behind the operation of the optically-controlled attenuator, I will describe the experiments performed to determine the optimal illumination of the silicon attenuator chip by varying the positions of the pair of lenses which focus the laser beam onto the chip. Measurements were made using diode lasers emitting at 840, 980 and 1060 nm wavelengths. Finally, I will suggest some directions for further exploration and possible improvements to the design of the attenuator.
Aug 17 Grant Meiners
Harvard University
Measuring Material Properties with a Quasi-Optical Resonator Cavity To better inform the design of CMB telescope optics, accurate values of indices of refraction and loss tangents must be known for a variety of potential optical materials. As CMB receivers operate at cryogenic temperatures, these material properties must be measured under norminal and cryogenic conditions. I will present our resonator cavity set up as a means for making accurate measurements under both of these conditions. I will also discuss the measurement process, some promising preliminary testing, and future work to improve the cavity's capabilities.
Sept 28 Edward Tong
CfA
The sSMA High Band Receiver -- A first look at its Performance Recently, the wSMA project crossed a milestone: the wSMA cryostat, equipped with both the Low Band (LO 210-270 GHz) and the High Band (LO 280-360 GHz) cartridges, is now in operation in the Receiver lab. In this talk, I will describe the details of the High Band receiver and its initial performance. Noise temperature of around 2.5-3 hf/k have been measured, and the usable IF bandwidth extends from just below 4 to close to 20 GHz.
Oct 5 Zhilei Xu
MIT
Building and Calibrating CLASS and SO The cosmic microwave background (CMB) is a powerful probe to study the early universe. In this talk, I will discuss the instrumentation and optical characterization of two CMB experiments: the Cosmology Large Angular Scale Surveyor (CLASS) and the Simons Observatory (SO).



Previous presentations available here: CfA managed Google Drive