Receiver Lab Talks: 2024
Questions: Edward Tong
Time: Thursday 12:00 PM EST/EDT
Where: M-340/Zoom
| Date | Speaker | Title | Summary |
|---|---|---|---|
| Dec. 12 | Abigail Unger CfA |
Enabling Solar Observations with the Submillimeter Array |
The Submillimeter Array (SMA) is undergoing a number of upgrades to enable solar
observation in the millimeter (mm) and submillimeter (submm) wavelength range.
Recent measurements with the Atacama Large Millimeter/ submillimeter Array (ALMA),
have highlighted the importance of mm/sub-mm for understanding the structure,
dynamics, and energy balance of the sun, but demand for ALMA solar observations
now exceeds availability. Existing features of the SMA, such as its wide field of
view (FoV), dual band observations, and polarization measurement capabilities make
it well-suited for solar observations with only modest upgrades.
The SMA is currently operating with a standard "solar avoidance zone" (SAZ) to protect against potential damage. Solar hardening retrofits will remove this restriction, ensuring the antennas can safely be operated pointed toward the sun for extended periods of time. These include the addition of aluminum shields to cover open airgaps along the quadropod legs, replacement of cables and covers with highly insulated alternatives, and addition of sensors for thermal monitoring. An initial set of prototype shields were manufactured and tested on a single antenna in summer 2024, and refined implementation efforts are in progress with plans to be ready for observation for the upcoming solar maximum. |
| Dec. 5 | Volker Tolls CfA |
Optical Modulation Reboot |
The optical modulation spectrometer (OMS) is a newer type of ultra-wideband (>10 GHz to ~60 GHz) backend
for heterodyne receiver systems. Very broadband spectrometers are required for receiver systems operating
at far-infrared wavelength (> 300 um). Large bandwidths are essential to observe broad emission or
absorption lines like from extra-galactic objects at high redshifts, to perform spectral line surveys,
and to observe planetary atmospheres, etc. Many of these lines are pressure or velocity broadened with
either large half-widths or line wings extending over many GHz.
Although the concept of the OMS has been developed and demonstrated in the early 2000s, -this presentation will summarize some of the early results-, recent developments of high-spectral-resolution optical spectrometers made it possible to now build such an instrument using off-the-shelf commercial components. In addition, the new OMS concept replaces the Fabry-Perot etalons used in the proof of the old concept with a high-spectral-resolution VIPA (Virtually imaged Phased Array) spectrometer. Now, the next step is to build a demonstration OMS and show that it meets all the requirements of a heterodyne backend for ground based and for space-based observatories and that the use of VIPAs is superior to the use of Fabry-Perot etalons. The backend requirements include a small form factor, low weight, and low power consumption, while its spectral resolution, bandpass, and radiometric stability, as measured using the Allan variance, must be suitable for on-the-fly and position switching observations. |
| Nov. 21 | Robert Wilson CfA |
The Discovery of Interstellar CO | Bell Labs was an early developer of millimeter wave components. In the 60's there was a big push to develop a millimeter wave long distance communications system to do what, in the end, fiber optics has done. As part of this system, Charles Burrus at Crawford Hill developed millimeter wave receivers by making Schottky Barrier diodes using modern photo-lithography. Arno Penzias and I recognized that these had a potential use in Radio Astronomy and with Ken Kellermann proposed to build a receiver with them for use on the then new 36 foot antenna. Although this attempt was premature and was not successful, in 1970 Arno, Keith Jefferts and I with much help from Sandy Weinreb put together a spectral line receiver with the hope of detecting rotational transitions of simple molecules in interstellar space. Since, at the time, only a few people like Phil Solomon had any idea that molecular clouds existed, we prepared to detect a weak signal. Our backup strategy, suggested by Pat Thaddeus, was to look for CN which had been known to exist since the late '30s. As we all know now the signal from Carbon Monoxide and even its less abundant isotopes was remarkably strong and measurements of it have since transformed our ideas of star formation. |
| Oct. 31 | Miranda Eiben CfA |
Wicked Windows and Abominable Anti-Reflection Coats for Hellish High Frequencies | Future millimeter wavelength experiments aim to both increase aperture diameters and broaden bandwidths to increase the sensitivity of the receivers. These changes produce a challenging anti-reflection (AR) design problem for refracting and transmissive optics. The higher frequency plastic optics require consistently thin polymer coats across a wide area, while wider bandwidths require multilayer designs. Additionally, because of large apertures, the cryostat vacuum window has become a major contributor to instrumental optical load, as it must be ambient temperature, transmissive to microwaves and strong enough to hold vacuum. Plastics such as polyethylene are a natural choice for a microwave vacuum window, due to their high transmissivity, availability and machinability. However, bulk plastic windows must be very thick, and therefore very emissive, to hold vacuum over a large aperture. I will present the multilayer AR coats for the thin window of the high frequency BICEP Array receiver (200-300 GHz) utilizing an expanded polytetrafluoroethylene (ePTFE) membrane , layered and compressively heat-bonded to itself. This process allows for a range of densities (from 0.3g/cc to 1g/cc)and thicknesses ($>$0.05mm) over a wide radius (33cm), opening the parameter space of potential AR coats in interesting directions. The layered ePTFE membrane has been combined with other polymer layers to produce band average reflections below 0.6\% on a thin high modulus polyethylene laminate window. I will also discuss updates on producing thin laminate polyethylene windows for high frequencies. |
| Oct. 17 | Laura Sinclair NIST |
A Brief Introduction to Optical Frequency Combs, Optical Clocks, and Frequency-Comb-Based Time Transfer |
The advent of the optical frequency comb 20 years ago, gave the precision metrology community an
unmatched time and frequency ruler. This accelerated the development of optical atomic clocks
with state-of-the-art clocks now reaching fractional uncertainties of 10-18 or lower.
This arose as combs can be used to coherently connect optical frequencies spanning hundreds of THz.
Detection of the comb pulses on low phase-noise detectors also generates microwaves that are
phase coherent with the comb's optical frequencies providing a coherent link between the optical
and microwave in a single step. The pulsed nature of optical frequency combs can be used to
generate labeled time markers, useful both for generation of a local timescale and for optical
time transfer.
In this talk, I will provide an overview of optical frequency combs, optical atomic clocks and the basics of optical two-way time transfer using frequency combs. This will include discussion on the advances towards development of robust, compact, and transportable combs and clocks. Following this, I will present recent results from the Optical Time Transfer Project at NIST including quantum-limited time transfer at the femtosecond-level over 300 km of air with a 300 fW detection threshold and the operation of a 3-node all optical iodine clock network. Finally, I will conclude with a discussion of possible future applications of optical timing networks for fundamental physics tests and distributed coherent sensing amongst other applications. |
| Oct. 10 | Jacob Kooi JPL |
SOI based 275-373 GHz (ALMA B7) SIS Junction Development for ngEHT | The Microdevices laboratory (MDL) at the Jet Propulsion Laboratory (JPL), with a long history of innovative SIS mixer technology development and fabrication, was contracted in 2021 to deliver quantum limited ALMA band 7 (275 - 373 GHz) SIS mixing devices for the ngEHT. Added goals were device uniformity and high yield for 2SB mixing operation. The intermediate frequency (IF) specification was 16 GHz with a goal of 20 GHz. Further details of the talk is available here. |
| Oct 3 | Edward Tong CfA |
Can an SIS receiver use a comb for its hair? -- a look at RF comb generators | Radio frequency (RF) combs have emerged as a new class of tools for precision phase and group delay calibration in frequency conversion devices and systems. In radio astronomical receivers, RF combs are invaluable for tracking instrumental phase changes, which in turn helps pinpoint atmospheric phase fluctuations. This capability is crucial for implementing the Frequency Phase Transfer technique, aimed at extending the coherent detection time of high-frequency receivers in Very Long Baseline Interferometry (VLBI) observations. In this talk, we will explore various types of RF comb generators that can produce frequency combs in the millimeter wave range. We will also discuss which of these generators is suitable for integration with Superconductor-Insulator-Superconductor (SIS) receivers. |
| Sept 26 | Sara Salem Hesari NRC Herzberg |
Advancements in Single Pixel Radio Receiver Technology at NRC Herzberg | The Radio Instrumentation Team at the National Research Council of Canada's Herzberg Astronomy and Astrophysics Research Centre (HAA) is developing advanced radio systems spanning cm- to sub-mm-wave bands. Their work is centered on technological advancements in receiver systems for current and future radio observatories including ALMA, ngVLA, SKA, Meerkat, CCAT prime and others. This talk will highlight two key R&D projects. Firstly, the development of a dual-linear polarization, single-feed Q-band cryogenic radio astronomy receiver designed for the ngVLA Band 5. Secondly, the design and development of wideband feed and waveguide components that span an octave or more, aimed at broadening the frequency coverage of modern radio receivers. This overview will emphasize the progress and strategic initiatives currently underway at HAA. |
| Sept 19 | Hannah Tomio MIT |
An overview of space-based optical communications, ranging and time transfer |
Optical (or laser) communications offer various advantages over the radio frequency (RF)
communication systems traditionally used for spacecraft. This is particularly true for
small satellites, whose capabilities can be constrained by their limited size, weight,
and power (SWaP). Due to the high directionality of the laser carrier, very high data
rates can be achieved with smaller, lighter, and less power-intensive terminals.
Laser communications also benefit from a less crowded spectrum (in the visible and
near-infrared) with little-to-no regulation; no licensing or frequency allocations are
necessary as with RF systems. The narrow beamwidth of a laser is also more difficult to
intercept, enhancing the security of a laser communications channel as compared to an RF
channel. These advantages have been widely recognized and driven the development of a
variety of laser communication terminals in industry and at research institutes.
This talk will provide an overview of laser communication systems and key technologies, with a particular focus on their relevance for the Black Hole Explorer (BHEX) mission. In addition, we will discuss ongoing developments in leveraging optical communication links for ranging and time-transfer. |
| Sept 12 | Anna Polish CfA/Harvard |
Upgrades to the rotating polarized source for calibrating BICEP3 | The BICEP3 telescope is a 95GHz CMB polarimeter located at the South Pole searching for evidence of inflationary gravitational waves. The polarized CMB signal can also be used to constrain a beyond-the-standard-model parity violation in electromagnetism known as cosmic birefringence. While inflation measurements only require relative calibration of the instrument polarization properties, cosmic birefringence constraints demand absolute polarization angle calibration for each detector. To perform this calibration, we use a rotating, polarized, broadband source whose polarization is carefully referenced to gravity, then observe it in the far field of BICEP3 to transfer the calibration. In this talk I will discuss the challenges involved in building an extremely precise (~0.03deg) absolute polarization calibrator, and improvements we've made for the upcoming Austral summer season. | >
| Sept 5 | John Kovac CfA/Harvard |
Broadband waveguide circular polarizers: revisiting design work from DASI | A novel design for a multi-element broadband waveguide circular polarizer, capable of achieving exceptional circular polarization purity over a 26-36 GHz operating band, was developed for the Degree Angular-Scale Interferometer (DASI) experiment, a LONG time ago when the presenter was a lot younger. DASI was a 13-element compact interferometer which used these polarizers in observations from the South Pole between 2001-2004 to achieve the first detection of polarization of the cosmic microwave background. While the DASI polarizer design (also used by the CBI experiment) employed dielectric elements, scalable all-metal designs were also developed, with claims made that "ultimate polarization precision achievable using this design over a 50% waveguide bandwidth is likely to be limited not by the polarizer, but by limitations of existing broadband OMTs." Possible interest in broadband circular polarizers by the BHEX project motivates quizzing the presenter to see how much of this he can remember. |
| Aug 29 | Stefan Knirck Harvard Physics |
Axion Dark Matter Searches from Radio to Infrared | Axions are excellent candidates for dark matter (DM) and would also explain why the neutron's electric dipole moment is vanishingly small. Under an external magnetic field axions in our own galaxy can convert to photons which can be enhanced in a resonator cavity. We first present our world-leading ADMX (Axion Dark Matter eXperiment) which has excluded QCD axion DM for about an octave in mass range around 4eV (1GHz) and is poised to search up to 16eV (4GHz). Yet, about 6 orders of magnitude of higher masses, up to eV (infrared), remain unprobed. At these masses resonant cavities become infeasible. Hence, we discuss our R&D on novel resonator technology for this range, including MADMAX (Magnetized Disk and Mirror eXperiment) and BREAD (Broadband Experiment for Axion Detection). We highlight our recent, first physics results. I will also discuss the program for my new group at Harvard University, pushing the boundaries of these new technologies into the "THz gap", while leveraging cutting-edge quantum sensing developments and forging international, cross-disciplinary collaborations to achieve a large-scale experimental program for axion discovery. |
| Feb 28 | Keara Carter CfA |
On the Progress of the ngEHT 86/115 GHz Receiver | The unveiling of the first image of a black hole, achieved through the collaborative efforts of the Event Horizon Telescope (EHT) in 2019, is a pivotal moment in astronomy. The next generation Event Horizon Telescope (ngEHT) is now poised to deepen our understanding of black holes through a leap in observational capabilities. The Receiver Lab is headquarters for the development of the 86/115 GHz receiver, designed to leverage the Frequency Phase Transfer Technique (FPT) to further increase the overall sensitivity of the ngEHT. This presentation will outline the receiver subsystem, detail the progress made, and explore the exciting work that lies ahead. |
| Jan 31 | Matt Morgan NRAO |
Integrated Receiver Development | The Integrated Receiver Development program at the NRAO aims to develop compact, mass-producible, and field-replaceable front-end hardware for the next generation of radio telescope facilities. Design principles include early digitaization, as near to the telescope focal plane as possible, and relatively seamless integration of analog, digital and photonic technologies into lightweight, low-overhead, front-end modules. The architecture is optimized to exploit the complementarity of integrated construction techniques and digital signal processing, achieving a level of precision and stability that is unmatched by other radio astronomical receivers. This talk will provide an introduction to the development philosophy, an overview of the team's technical capabilities, and presentation of some of the past, current and ongoing developments, including a suite of warm electronics modules being desinged for the Next Generation Very large Array (ngVLA). |
| Jan 24 | Matthew Petroff CfA |
The Precursor Small Aperture Telescope (PreSAT) CMB Polarimeter | The Precursor Small Aperture Telescope (PreSAT) is envisioned as an early step to the next generation CMB-S4 cosmic microwave background experiment, which will test prototype CMB-S4 components and technologies within an existing BICEP Array receiver, with the aim of enabling full-stack laboratory testing and early risk retirement, along with direct correlation of laboratory component-level performance measurements with deployed system performance. The instrument will utilize new 95/155 GHz dichroic dual-linear-polarization prototype detectors developed for CMB-S4, cooled to 100 mK via a adiabatic demagnetization refrigerator, along with a prototype readout chain and prototype optics manufactured with wide-band anto-reflection coatings. The experience gained by integrating, deploying, and calibrating PreSAT will also help inform planning for CMB-S4 small aperture telescope commissioning, calibration, and operations well in advacne of fabrication of CMB-S4 production hardware. The design and goals of the PreSAT project will be discussed, along with current and near-future laboratory testing plans. |
Previous presentations available here:
CfA managed Google Drive
