Jonathan Greenfield

Development of Superconducting Devices using Magnesium DiBoride for Terahertz Astronomy:

  Superconducting devices are used in astronomy as they can measure high frequency signals with low noise and high resolution. Different superconducting materials have critical temperatures below which they have zero resistance. Materials with lower critical temperatures are limited in their range of frequencies as higher frequency signals can destroy the superconductivity more easily. Previous detectors for NASA missions have used superconductors like Niobium or Niobium Titanium Nitride with critical temperatures around 10 degrees above absolute zero. This critical temperature limits the range of frequencies to less than approximately 1 terahertz. In addition, there are new designs for devices that use a property of the superconductor called kinetic inductance to achieve lower noise. Magnesium DiBoride (MgB2) is a superconductor that has shown lots of promise with its relatively high critical temperature (Tc ~ 39 K), high kinetic inductance, and its ability to tune the normal resistance of the material by adjusting the fabrication parameters. In order to characterize the material properties of this superconductor and demonstrate devices for the next generation THz astronomy NASA missions. The goal is to make superconducting transmission lines (STL) with controllable delay for use in on-chip Fourier Transform Spectrometers (FTS) at mm and sub-mm wavelengths. The proposed work will develop technology to achieve hyperspectral imaging into the THz spectrum with spectral resolution R<=104. The work combines a novel technology in current-controlled superconducting delay lines with a novel material, Magnesium DiBoride. The delay lines utilize the non-linear kinetic inductance in a STL, and the MgB2 thin films offer the promise of this effect at frequencies up to and beyond 1 THz.

CubeSounder: A Novel 3D Weather Imager

CubeSounder is a program enabling low-SWaP-C (Size, Weight, Power and Cost) remote-sensing technology for weather atmospheric-sounding and cubesat applications. It matures a novel 50-183 GHz waveguide filter-bank technology into a prototype sensor system, then demonstrates the prototype in a relevant environment by measuring 3D atmospheric water vapor and temperature profiles from the ground. Data from microwave radiometers on large U.S. weather satellites is the single highest impact driver of global weather forecasting. CubeSounder brings microwave sounding capabilities to the cubesat platform for the first time, enabling wider deployment to provide the real time data needed for major weather forecasting improvements. It also improves the global revisit time from days to hours as needed to improve the lead time and accuracy of weather forecasting. Satellite microwave sounding instruments observe the 60 GHz oxygen emission line and 183 GHz water vapor emission line to remotely sense 3D temperature and humidity profiles