Receiver Lab Talks: 2025
Questions: Edward Tong
Time: Thursday 12:00 PM EST/EDT
Where: M-340/Zoom
| Date | Speaker | Title | Summary |
|---|---|---|---|
| Dec. 11 | Sally Lau ASIAA |
The FRB Hawai'i Outrigger Station System Performance and Operation Status | The FRB telescope array in Pahala, Hawai'i serves as an outrigger station for the CHIME and BURSST fast radio burst detection projects. Operating entirely off-grid, the site integrates PV power, satellite network, and continuous environmental and system monitoring to enable stable remote observations. I will highlight recent antenna testing, spectrum characterization, and system performance assessments, along with the current status of the array. These developments showcase the station's role in expanding baseline coverage and supporting future multi-site FRB localization efforts. |
| Dec. 4 | Yosuke Murayama NAOJ, Japan |
Development of 300 GHz Bnad SIS Mixers for the BHEX Project | We developed and evaluated an initial prototype of a 300-GHz band SIS mixer for the Black Hole Explorer (BHEX) mission at NAOJ. The SIS mixer device based on the 3-series Nb/Al-AlOx/Al/Nb junctions were fabricated, and their I-V characteristics and double-sideband (DSB) noise performance were measured. Mixer operation was confirmed for LO frequencies from 240 to 310 GHz at a mixer block temperature of 2.9 K, with clear pumped I-V behavior and hot/cold IF responses. In this talk, I will show the IF spectra and DSB noise temperature obtained at each LO frequency, along with fabrication-related issues identified through this initial evaluation. |
| Nov 13 | Hannah Rana CfA |
Keeping it Cool in Space | Space cryocoolers are essential for enabling high-sensitivity instruments in astrophysics and planetary science space missions. This talk will provide an overview of the current landscape of space-qualified cryocooler technologies, including Stirling, pulse tube, and Joule-Thomson systems, and their integration into multi-stage cooling chains reaching low to sub-Kelvin temperatures. I will also highlight recent advances that reduce vibration, improve efficiency, and support detectors such as infrared sensors and superconducting arrays. Case studies from ongoing and upcoming missions will be used to illustrate integration challenges and performance trade-offs. Finally, I will discuss emerging directions in cryocooler miniaturization, lifetime extension, and fault prediction for long-duration (deep) space missions. |
| Nov 6 | Yan-Jun Wang ASIAA/NTU |
Design study of an SIS junction array for a 125-210 GHz broadband receiver | Superconductor-insulator-superconductor (SIS) mixers are essential components in sub-mm heterodyne receivers, offering quantum-limited sensitivity. An SIS mixer covering the frequency band of 125-210 GHz band is being planned. In this talk, I will present the ongoing design work of the mixer layout, which will be based on an SIS junction array. I will show the numerical analysis of different array configurations, the optimization of impedance matching, and the tri-frequency modeling for the conversion gain calculation based on Tucker's theory. |
| Oct 30 | Jungwon Kim MIT/KASI |
Optical frequency comb integration in radio telescopes: advancing signal generation and phase calibration | Very long baseline interferometry (VLBI) enables high-angular-resolution observations in astronomy and geodesy by synthesizing a virtual telescope with baslines spanning hundreds to thoursands of kilometers. Achieving high instrument phase stability in VLBI relies on the generation of high-quality, atomic-referenced RF local oscillator (LO) and RF-comb signals for the effective downconversion of celestial RF signals and precise phase calibration, respectively. As observing frequencies move into higher ranges with wider bandwidth, conventional electronic methods face significant challenges in maintaining the quality of these signals. Here, we demonstrate that an optical frequency comb (OFC) can be used as a versatile tool to generate and distribute low-noise and atomic-reference RF-comb and RF-LO signals in the VLBI telescope. Hydrogen maser-stabilized optical pulses are transmitted over a time-stabilized fibre link from the observatory buiiding to the VLBI receiver system at the telescope, where photodetection converts them into the required RF signals. In VLBI test observation, we successfully detected VLBI fringes and extracted the RF-combs characteristics in a format suitable for VLBI instrumentation phase calibration. These results highlight the high potentail of OFC-based technology for enhancoing nex-generation broadband VLBI measurements, advancing astrophysical research and facilitating intercontinental clock comparison. |
| Oct 16 | Sunil Golwala Caltech |
New Music: The next generation Extended-Wavelength Multiband Submillimeter Inductance Camera | The Next-generation Extended Wavelength-MUltiband Sub/millimeter Inductance Camera (NEW-MUSIC) will be a first-of-its-kind, six-band, trans-millimeter-wave polarimeter covering 2.4 octaves of spectral bandwidth 80-420 GHz to open a new window on the trans-mm time-domain frontier, in particular new frontiers in energy, density, time, and magnetic field. NEW-MUSIC's broad spectral coverage will also enable the use of the Sunyaev-Zeldovich effects to study accretion, feedback, and dust content in the hot gaseous haloes of galaxies and galaxy clusters. Six-band spectral energy distributions, with polarization information, will yield new insights into stellar and planetary nurseries. NEW-MUSIC will employ hierarchical, phased arrays of polarization-sensitive superconducting slot-dipole antennas, coupled to photolithographic bandpass filters, to nearly optimally populate a 14' field-of-view with six spectral bands over 80-420 GHz (1:5.25 spectral dynamic range). Light will be routed to Al or Al/Ti microstripline-coupled, parallel-plate capacitor, lumped-element kinetic inductance detectors (MS-PPC-LEKIDs), an entirely new KID architecture that substantially enhances design flexibility while providing background-limited performance. Innovative, wide-bandwidth, etched silicon structures will be used to antireflection-treat the back-illuminated focal plane. NEW-MUSIC will cost-effectively reuse much of the MUSIC instrument, initially deploying a quarter-scale focal plane capable of the bulk of NEW-MUSIC science followed later by a full-FoV focal plane needed for NEW-MUSIC wide-area survey science. |
| Oct 9 | Edward Tong CfA |
How to use SIS receivers for solar observations? Linearity considerations for SIS mixers | The Submillimeter Array (SMA) is embarking on a program of solar observations which will increase our understanding of the solar chromosphere. The observations will be conducted with the existing SIS receivers of the SMA. While these superconducting receivers offer quantum-limited noise performance for most astronomical objects, the question to be addressed is how they can be harnassed to observe the sun, which has a brightness temperature in thousands of Kelvin. In this talk, I will start with a theoretical treatment of the linearity for SIS mixers, followed by a look at experimental data, to come up with a strategy to operate SIS mixers for solar observations. |
| May 8 | Kirit Karkare BU |
Exploring the High-Redshift Universe with Millimeter-Wave Line Intensity Mapping and On-chip Spectromemter | Answering outstanding questions in cosmology - such as understanding the nature of inflation, dark energy, and reionization - requires observations of ever-increasing volumes of the universe. In this talk I will discuss a new technique for measuring large volumes at high redshift: line intensity mapping (LIM) of far-IR emission lines. This technique is enabled by advances in millimeter-wave spectrometer technology. I will introduce SPT-SLIM, a pathfinder experiment at the South Pole Telescope that will demonstrate the use of superconducting on-chip spectrometers for LIM. SPT-SLIM targets CO-emitting galaxies from 0.5 < z < 2. I will then discuss the future of mm-wave LIM and the technical advances needed to develop this technique into a next-generation cosmological observable. |
| May 1 | Gabriella Montano CfA/NEU |
A Novel Comb Generator for Frequency Phase Transfer | The Black Hole Explorer (BHEX) mission, a space Very-Long-Baseline Interferometry (VLBI) mission concept, aims to observe black holes across long baselines and dual-band frequencies: 76-106 GHz and 228-320 GHz. For this dual-band receiver system, the coherence time of observation can be increased by removing the effects of atmospheric fluctuations. A frequency comb can be used for this purpose through the Frequency Phase Transfer (FPT) technique, by enabling precise phase delay tracking of the receiver pair. In this talk, I will present a novel comb generator design together with the testing process. We have injected this comb into the next-generation Event Horizon Telescope (ngEHT) and the wideband Submillimeter Array (wSMA) receivers, and successfully observed the expected comb output. These results indicate that the comb generator should work well in BHEX's dual-band receiver system. |
| Mar. 27 | Brodi Elmwood Harvard |
Measurement of the Complex Permittivity of Dielectrics with Quasioptical Fabry-Perot Resonators | Millimeter-wave instrumentalists increasingly require a precise understanding of the complex permittivity of the dielectrics employed in their instruments. Moreover, it is often key to understand the behavior of complex permittivity-in particular loss-across a wide range of frequencies and temperatures. Traditional methods of measuring the refractive index and dielectric loss of a material struggle under these requirements. In this light, there is renewed interest in the metrological application of open resonant cavities for the precise measurement of refractive index and loss. We describe the design, implementation, and characterization of a series of compact high-finesse quasioptical Fabry-Pérot resonant cavities spanning 75-330 GHz specifically commissioned for these measurements. |
| Mar. 13 | Yoshinori Uzawa NAOJ |
Current Status of SIS receiver technology at NAOJ | The development of superconductor-insulator-superconductor (SIS) receivers at the National Astronomical Observatory of Japan (NAOJ) will be presented. NAOJ has participated in the international project of ALMA. During the construction phase of ALMA, NAOJ has developed and manufactured Band 4 (125-163 GHz), Band 8 (385-500 GHz), and Band 10 (787-950 GHz) SIS receivers. After the construction, NAOJ has been developing SIS receiver technologies for Band 8 upgrade. A multibeam receiver development will also be presented. |
| Feb. 27 | Jim Moran CfA |
The Origins of Very Long Baseline Interferometry in Radio Astronomy | In this talk, I will describe the origin of the idea that the image of a radio source can be built up from the fringe visibility measurements of a two element interferometer, as first demonstrated by Michelson in the 1920s. The achievable resolutions at radio wavelengths were limited to about 0.05" in the early 1960s, but an amazing confluence of the technological developments of television recording technology, precise atomic clocks and fast digital computers made possible the formation of coherent interferometers with arbitrarily large element separations. Angular esolutions have been pushed down to 25 microarcseconds over more than 50 years of development. |
| Feb. 20 | Laura Fissel Queens Univ., Canada |
Very Long Baseline Interferometery from the Stratosphere: The Balloon-borne VLBI Experiment (BVEX) | The resolution of ground-based Very Long Baseline Interferometry (VLBI) is limited in baseline by the size of the Earth, and in observing frequency by the molecular absorption of the atmosphere. While space missions are extremely costly, balloon-borne VLBI would give access to frequencies beyond those of the Event Horizon Telescope (EHT) at a fraction of the cost. As a first proof of concept for balloon-borne VLBI, the Balloon-borne VLBI Experiment (BVEX) will launch as part of the Canadian Space Agency's (CSA) Stratos program from Timmins, Ontario, Canada in August 2025, operating above more than 99% of the Earth's atmosphere. This experiment consists of a K-band 22 GHz radio telescope and receiver, where the signals will be correlated with simultaneous observations made by the Very Large Baseline Array. In this talk we will give an overview of the telescope, receiver, and backend as well as technical challenges such as position tracking and timing reference stability that arise when attempting VLBI from the stratosphere. To wrap up, we will talk about how lessons learned from BVEX will help in designing a mm/sub-mm VLBI mission in the future, which could improve the uv-coverage of VLBI networks such as the EHT or next-generation EHT (ngEHT). |
| Feb. 13 | Liam Connor Harvard |
Large-N Small-D Arrays at ~1 GHz | Radio astronomy at GHz frequencies is uniquely coupled to Moore's Law. Modern interferometers are computational cameras, driving survey telescopes towards the large-N small-D paradigm. I will discuss two proposed radio telescopes. The first is the 2000-antenna deep synoptic array (DSA-2000), which will map 3 pi sr of sky between 0.7 and 2 GHz at unprecedented speed, with commensal HI, pulsar, FRB, and continuum surveys. The second is a concept for a "coherent all-sky monitor": a dense aperture array that will find the brightest FRBs from the local Universe. While these projects are at different stages and are of disparate scales, they have a number of key technologies in common. On the all-sky monitor, I welcome ideas, advice, and engagement! |
| Jan. 30 | Sara Issaoun CfA |
Frequency Phase Transfer for (sub)millimeter VLBI | Frequency Phase Transfer (FPT) is a key technique to increase coherence and sensitivity in radio interferometry via the use of non-dispersive phase solutions derived at lower frequencies to calibrate higher frequencies. While this technique, pioneered by the Korean VLBI Network, is readily used at frequencies under 130 GHz, it remains largely untested in the (sub)millimeter regime. Over the last two years, an effort has been made to outfit dual-band systems at (sub)millimeter observatories participating in the Event Horizon Telescope (EHT) and to test the feasibility and the performance of FPT up to the 1.3mm observing wavelength of the EHT. In this talk, I will present the status and results of simultaneous dual-frequency VLBI observations carried out and the applications of this technique to ongoing and future projects. |
| Jan. 16 | Edward Tong CfA |
Receiver Linearity Considerations: How to measure gain compression accurately | Astronomical receivers typically handle very weak input signals. With the development of ultra-wideband receivers and the neccessity to calibrate them using a relatively warm black body, there is a risk that the receiver may operate outside its linearity range. The most prevalent issue is gain compression, which occurs when a receiver component's gain is reduced by large input signals. In this presentation, I will detail a technique for accurately measuring low-level gain compression in both amplifiers and mixers, ensuring the linear operation of receivers |
Previous presentations available here:
CfA managed Google Drive
