Balloon-borne Large-Aperture Submillimeter Telescope

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BLAST Polarization

Submillimeter light carries information about the elusive Galactic magnetic field; the information is encoded in the light's polarization properties.

After several sucessful flights our team added polarization sensitivity to BLAST. The photo at right shows ourcryogenic half-wave plate rotator (recently developed at Northwestern University) installed in the BLAST receiver at U. Penn. Collaborators at Cardiff University built the half-wave plate itself as well as the photolithographic polarizing grids that will mount in front of the bolometer arrays. The grids have alternating bands of vertical and horizontal polarizers, providing common-mode noise rejection via near-simultaneous detection of orthogonal polarization components. The broadband half-wave plate had high modulation efficiency for all three frequency bands.

With these new components BLAST was transformed into BLASTPol, an new experiment designed to reveal the large-scale magnetic fields of star forming molecular clouds. BLASTPol had two sucessful science flights, launching in December 2010 and 2012 from McMurdo, Antarctica.

Send questions or comments to Mark Devlin