Lab
Sept, 2018: Our GIRMOS Adaptive Optics test bench at NRC-HAA in Victoria (COOP students George Wang and Alex Lu), characterizes and mitigates the creep on a range of Deformable Mirror technologies, reducing the open loop error on the Adaptive Optics system for GIRMOS. A higher order 18x18 open loop AO system is currently being implemented for prototyping the GIRMOS-AO arms.
Mar18, 2013: Our test cryostat/dewar, cooled with a Cryomech PT415 pulse tube cooler and Chase 250mK closed cycle 3He evaporation cooler, is nearing operation. We will initially dark-test Polarbear-2 TES sinuous antenna detectors, but will move to optical testing in the coming year.
GIRMOS: Gemini infra-red multi-object spectrograph
GIRMOS - the Gemini Infrared Multi-Object Spectrograph - is designed to produce high angular-resolution and highly sensitive infrared images of the sky. It will image four objects simultaneously within a two arc-minute field of view-a capability known as multiplexing.
Through collaborations with NRC, UBC, and UVic, I lead the development of the Adaptive Optics system for GIRMOS, and its implementation together with the Gemini GeMS system which provides lower order correction. The overall spectrograph is led by Prof. Suresh Sivanandam of the Dunlap Institute, UofT
The GIRMOS spectrograph will target high-redshift (1 < z < 10) galaxies to help in the study of their formation and evolution, back to a time in the early universe when galaxies were first forming. It will also help in the investigation of galaxy mergers in dense environments. It will enable near-field cosmology through the study of metal-poor stars in the Milky Way Galaxy's central bulge. It will also help astronomers study star formation physics in the Milky Way.
GIRMOS will serve as a precursor to the IRMOS spectrograph, a high-priority instrument for the Thirty-Meter Telescope now under construction in Hawai'i. It will serve as an important follow-up instrument for the James Webb Space Telescope (JWST) when it is launched in 2021.
GIRMOS is designed for use on the 8-metre telescopes of the Gemini Observatory, the largest telescopes available to Canadian astronomers.
CCAT/XSPEC: Millimeter-wave Multi-object spectrograph (MOS)
The XSPEC spectrograph on CCAT aims to multiplex as many as 100 targets over the 1deg^2 field of view onto individual `on-chip' spectrographs. This will be accomplished through opto-mechanical positioners which each patrol a ~7' region. Our lab has designed a prototype to be implemented with a full optical train. In addition, CCAT has no chopping secondary, and beam switching speed of ~0.5sec is required. We are currently working on designing a chopper on the prototype MOS positioners to efficiently subtract sky background noise.
Our system uses 75mm clear aperture AEROTECH rotator stages, along with a voice coil chopper and custom stepper-motor drives on the injection optics. This system can meet positioning requirements under loads and tracking speeds over the curved 1 deg^2 field, with the small chopper accommodated in the beam path.
Fourier Transform Spectrograph (FTS) for bandwidth characterization of millimeter-wave bolometers.
An FTS can be used to measure the spectral response of the detectors. We have built a Michelson interferometer in our lab to initiate testing of new detectors for POLARBEAR-2 arrays, and to test microstrip filter designs for suitability in multi-chroic bolometer arrays.
A millimeter-wave Martin Puplett polarized spectrometer will also be fabricated and used to measure passbands on detector arrays that incorporate on-array band transmission-line filters. Two interchangeable interferometer arms will be implemented: a low-resolution arm that give ~3 GHz resolution for characterizing photometric bands and and high-resolution arm that gives 200 Mhz resolution for characterizing monolithic spectrometers.
Feedback from such measurements will be critical for optimization of the detector array designs. The passband position and width depends on the electrical design of the filters, superconducting material properties, and the accuracy of the photolithography e.g. with reduction of transmission line widths due to over etching. The use of a polarized Martin Puplett design will allow characterisation of the polarization plane as a function of frequency for the broadband antenna-coupled pixels that will be tested. Such a measurement can not be done with a simple polarized thermal sources, since such a source only gives an average number for the entire band and would therefore miss any substructure in the band that would be detrimental to an astrophysical measurement.
Nano-fabrication, lithography lab, U.C.Berkeley
(Colin Ross pictured during his recent visit to the lab). We are involved in the design and fabrication of multi-chroic pixels for millimeter wave surveys. We are involved in designing antenna-coupled TES detectors to work at short submm wavelengths (as short as 200um).
