The Submillimeter Array

Receiver Lab Talks: 2023

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

Date Speaker Title Summary
Feb 1Edward Tong
Test Data from the first wSMA Receiver The prototype wSMA cryostat has recently been shipped to Mauna Kea, Hawaii, and one round of optical alignment has been performed. The low and high band wSMA cartridges, together with their associated LO modules will be shipped in February, with the hope that they will see first light shortly thereafter. In this talk, I will present the perfromance data collected on this receiver pair in the Receiver Lab in Cambridge, during the integration tests, as well as the projected schedule for wSMA receiver deployment.
Feb 8Kieran Cleary
The CO Mapping Array Project (COMAP) The CO Mapping Array Project is using its Pathfinder instrument to perform line intensity mapping of galaxies at z~3. The Pathfinder is a 19-feed single-polarization spectrometer focal plane array fielded on a 10.4-m telescope at the Owens Valley Radio Observatory. In this talk, I will report on the Pathfinder instrument design, the current status of the Pathfinder Survey and future plans for the project involving a prototype dish for the next generation Very Large Array.
Feb 15Paul Grimes
Verifying Optical Alignment of the wSMA Receivers As part of the instrument verification process before the deployment of the first prototype wSMA receiver, we have carried out a series of alignment measurements, firstly using visible light, and then with millimeter-wave coherent beam scanning. I will discuss our set up for measuring and adjusting the optical alignment of the wSMA Receiver system, and the millimeter-wave beam scanning technique that we have used in the lab. I will present results from beam scanning experiments in Cambridge Receiver Lab, and discuss plans for how we will verify the millimeter-wave beam alignment when the wSMA receiver is installed in an SMA antenna.
Feb 22Miranda Eiben
Harvard University
Development of Large Thin Windows for Millimeter Receivers As aperture sizes grow, the vacuum windows of millimeter receivers must balance the competing needs of strength and transparency. We have developed a new strategy to generate highly transmissive and strong windows by laminating woven High Modules Polyethylene (HMPE) with Low Density Polyethylene (LDPE), resulting in windows approximately half a wavelength thick (0.7 to 2 mm). Such laminate windows have been tested extensively, and are currently deployed on both BICEP3 and the newest BICEP Array receiver at the South Pole.
March 1Elliot Richards
8 GHz Block Downconverter Design for the Next Generatiobn Event Horizon Telescope (ngEHT) The Next Generation Event Horizon Telescope (ngEHT) will doubke the current EHT bandwidth, digitizing 8 GHz, per polarization, per sideband. This talk will detail the design of a novel instrument capable of downconverting this wide bandwidth in a single block and conditioning the analog signal for optimal digitization. We will share results from our prototype testing and plans for manufacturing the final device.
March 8Edward Tong
wSMA High Band Local Oscillator The wSMA High Band Local Oscillator is specified to drive the dual polarized wSMA High Band receivers between 280 and 360 GHz. In this talk, I will present the architecture and implementation, as well as some measured data from the first module.
April 19Jake Connors
Re-defining G in transition edge sensor bolometer design: Applications to Far-Infrared Spectroscopy High resolution direct-detection spectrometers, operating from 30-300um with spectral resolution of up to R~10^5, require broadband, direct absorption detectors with noise equivatlent powers (NEP) of < 10^-19 W/rt-Hz to perform background limited observations. Transition edge sensor (TES) detectors are broadband, and they have a simple electrothermal response as well as well understood fabrication. In addition to operating them at increasingly low temperatures, these NEP's can be achieved through the reduction of the bolometers' thermal link to the bath, G. Instead of fabricating very narrow or long TES thermal links, we choose to utilize coherent phonon transport effects to systematically reduce G. Presented herein is a study of various TES thermal link designs approaching extreme dimensions, exploring fabrication feasibility, theoretical calculations of detector performances, and discussion of upcoming measurements of fabricated TES detectors.
April 26Bert Hawkins
Joey Lambert
NRAO's Central Development Lab and the ALMA Band 6 Receiver Upgrade Bert Hawkins will provide an overview of NRAO's Central Development Laboratory, covering the major projects and initiatives the lab is currently working on, including on-going work for ALMA and ngVLA in receivers, low noise amplifiers, optics/electromagnetics, DSP/correlator, and timing distribution. He will also cover some new areas for CDL such as LNA technology development, radar development using the Green Bank telescope, spectrum monitoring hardware to support NSF"s National Radio Dynamic Zone initiative. He will also briefly cover new programs at CDL to recruit and develop future engineers and researchers at CDL.
Joey Lambert will focus specifically on ALMA Band 6 receiver upgrade project, including updates on the development of a new Band 6 mixer and other key components.
May 3Matthew Petroff
Applications of 3D Printing for Millimeter-wave Instrumentation Additive manufacturing in the form of 3D printing has become increasingly widespread in recent years. As this technology can produce submillimeter-sized features, it has potential uses in instrumentation and optics for millimeter wave astronomy, such as in cosmic microwave background experiments. This talk will discuss the application of such technology to the development of a broadband millimeter-wave absorber printable via the extrusion of a carbon-loaded thermoplastic. It will then move on to discuss the use of sterolithography-based 3D printing, with a focus on the fabrication of copper-plated Q-band waveguide components.
June 7Ganesh Rajagopalan
Signal Chain Development for NASA Geodetic VLBI stations & Status Update on the Haystack 37 m Telescope In the first part of the talk, I will describe the development of a 2-14 GHz cryogenic receiver frontend and the signal chain for NASA operated Geodetic VLBI stations. This design is based on a 6:1 bandwidth QRFH -Quadrature-Ridged Flared Horn feed and wideband cryogenic Indium Phosphide Low Noise Amplifiers from Sandy Weinreb's group. In the second part of the talk, I will describe the recent activity to revive astronomy operations at the Haystack 37 m telescope with the goal of joining the next generation EHT array.
June 21Edward Tong
A new Quasi-Optical Diplexer Design for Millimeter/Submillimeter Dual Band Receiver Systems Dual band observation of celestial sources using a pair of dual-polarized receiver set has emerged as the next phase of development for millimeter and submillimeter radio-astronomical instrumentation. While there are existing diplexer designs based on frequency selective surfaces, these diplexers introduce losses to the system and do not work well at a large angle of incidence. In this talk, I will present a new low loss quasi-optical diplexer design based on high resistivity silicon disks. We have plans to introduce this diplexer into the wSMA cryostat to enable dual band dual polarization 230/345 GHz observations in the near future.
June 21Matthew Miller
Thin polyethylene vacuum windows with PTFE AR coatings: Fabrication and Optical Testing Receivers recently developed for the BICEP/Keck program have presented new challenges in the creation of suitable vacuum windows and anti-reflection (AR) coatings. As a result, windows with greatly decreased thickness have been developed and deployed, and a method that provides greater control over the thickness and refractive index of AR coatings is currently being explored. This talk will describe the fabrication processes of these optical elements (with an emphasis on the AR coatings) and several techniques used to test theire optical performance. To illustrate the potentail applications of these techniques, the fabrication and testing of an AR-coated thin window sample designed for the wSMA receiver will be described.
Aug 2Namson Ngyuen
Worcester Stat University
Building an Infrasonic Interferometer for Atmospheric Phase Correction A challenge in astronomical observations using interferometers like the SMA are the scattering and refracting effects of the atmosphere, which cause decorrelation and phase instability. While radiometers correct for water vapor-induced path length differences, residual errors imply an unaccounted atmospheric component. Our project aims to employ an array of barometers to measure density fluctuations in order to correct for variations in the "dry" component of the excess path length, increasing the accuracy and sensitivity of the astronomical interferometer.
Aug 10Ciara Espaillat
UMass Lowell
Cryogenic Thermal Conductivity Measurement of Stainless-Steel Waveguide for Submillimeter Wave Applications Stainless-steel waveguides are used to carry Local Oscillator power to the SIS detector, which receives the astronomucal signal. These waveguides can be a significant source of thermal load to the cryostat, especially from the 80 K shield stage to the 4 K cold plate. This experiment employs a differential setup, which allows us to cancel out any parasitic heat transfer and measure the thermal conductivity integral of the Stainless Steel waveguides. From the measured data, we can derive the thermal load caused by the waveguides and compare against the model values.
Aug 30Adrian Peguero
UMass Boston
Chilling Precision: Navigating the Calibration of Cryogenic Microwave Measurements It is well known that accurate and reliable microwave and RF measurements are extremely challenging in a cryogenic environment. As is the case with room temperature measuremenst, calibration is neccessary in order to remove any underlying systematic effors in the setup. Methods of calibration already exist for room temperature measurements, but these have to be adapted for cryogenic measurements. In this presentation, I intend to go over the multiline Transmission-Reflect-Line (TRL) cakibration I used, and how the calibration procedure was implemented and executed inside the cryostat, with the goal of characterizing the wideband wSMA isolators. I will briefly describe the devices and calibration standards that I worked with, as well as the procedures and results.
Sept 27Joseph Eimer
Johns Hopkins University
Early Results from the CLASS 40 GHz Survey of the Cosmic Microwave Background In this talk, I present an analysis of maps covering 75% of the sky made from the ground-based 40 GHz channel of the Cosmology Large Angular Scale Surveyor (CLASS) from August 2016 to May 2022. Using fast front-end polarization modulation from the Atacama Desert, we show this channel achieves higer sensitivity that in the analogous frequencies from satellites measurements in the range 10 < \ell < 100. In combination with other data, these new maps improve our understanding of the polarized synchrotron spectral energy distribution -- critical for isolating cosmological signals from galactic astrophysics. These results establish a new standard for recovery of the largest-scale CMB polarization from the ground and signal exciting possibilities when the higer sensitivity and higher frequency CLASS channels are included in the analysis.
Oct 4Lingzhen Zeng
Cryogenic Isolator for Sideband-separating Receivers The wideband cryogenic isolators developed in the Submillimeter Receiver Lab have been deployed in the SMA DSB receiver system for several years. These isolators play an important role in expanding the IF bandwidth of the array. Starting earlier this year, we were engaged in an ALMA study project aimed at developing isolators for use in a 2SB receiver system. In this talk, I will begin with an introduction to the fundamentals of edge-mode isolators. Following that, I will share with you an exciting update on the most recent developments from the ongoing study project. Finally I will discuss the challenges we are encountering and our future development plans.

Previous presentations available here: CfA managed Google Drive