Current Research Projects
Our research centers on precision measurements in observational cosmology.
Cosmic microwave background (CMB) polarization measurements can give us extremely valuable information about our universe.
Measurements of these faint signals will play a major role in understanding the inflationary epoch and the distribution of
matter and the evolution of large scale structure. Measuring the CMB polarization has become one of the major goals of CMB
experiments. However, the polarized CMB signal is so small that its measurement requires not only very high instrumental
sensitivity, but also exquisite control of systematics. In collaboration with Greg Tucker's group at Brown University, Ben
Wandelt's group at the Institut d'Astrophysique (Paris) and Ted Bunn's group at University of Richmond, we are building a
suite of simulation software to simulate CMB interferometric observations and to assess various systematic errors in CMB
power spectra estimates by using maximum likelihood method and Gibbs sampling technique.
Kinetic Inductance Detectors (KIDs) use small superconducting resonant circuits to detect incident photons (P.K. Day, Nature (2003)).
Photons are absorbed, breaking Cooper pairs and causing a change in the kinetic inductance which results in a shift in the resonant
frequency of the circuit. KIDs offer significant advantages over competitor detectors in terms of multiplexing, fabrication, critical
temperature tolerance, and focal plane coverage. QUBIC is a planned CMB
polarization telescope designed to search for the primordial B-mode anisotropy, a smoking gun for inflation. It will be deployed
at the Concordia station in Antarctica in 2015.
We are developing general-purpose software to model systematic effects in interferometers to address three important issues facing
interferometers consisting of hundreds to thousands of antennas. First, we will develop calibration algorithms, which require measuring
the complex beam gain of each element as a function of frequency. Second, we will develop analysis techniques for large "data cubes"
for removing foreground sources and recovering cosmological power spectra. Third, we will extend our simulation techniques for modeling
and controlling systematic effects.
Beam Pattern Measurements
We fabricated a model antenna in an effort to assist the experimental efforts on low redshift, 21cm intensity mapping observations for
dark energy measurements as part of the Tianlai Project. Using LabVIEW automated instrument readout, we are testing the response of the
model antenna in various locations. We hope to compare the beam pattern measurement of our antenna to that shown in CST simulations.
Our research is motivated by precision control of heat flow in ultra-low temperature experiments. Specifically, the experiments in our
lab are run at temperature of approximately 100 millikelvin. In order to reach the extremely low temperatures, an adiabatic
demagnetization refrigerator (ADR) must be used. However, in the process of using the ADR, residual heat is generated which must be
drawn off to a cold bath. The device used to connect and disconnect the salt pill to the cold bath, in our case a helium bath, is
called a heat switch. We developed a mechanical heat switch that is powered by a stepper motor.
MBI: The Millimeter Wave Bolometric Interferometer
THM: A Transition-Edge Hot-Electron Microbolometer
Big Bang Blackbody Simulator
Stereolithographed Microwave Components
Giant Microwave Window
The first CMB polarization telescope optimized specifically for CMB polarization measurements at small angular scales
A telescope optimized specifically for CMB polarization at large angular scales
for precision measurements of the energy spectrum of neutrons
Miniature Adiabatic Demagnetization Refrigerator