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Published July 1, 2012 | Published
Book Section - Chapter Open

Tracking faint fringes with the CHARA-Michigan Phasetracker (CHAMP)

Abstract

The CHARA-Michigan Phasetracker (CHAMP) successfully tracks fringes in 4-telescope and 6-telescope modes when observing high-visibility targets. We have found that our primary targets (Young Stellar Objects) have unexpectedly low visibility fringes (<20%) for most baselines at CHARA, generally below our tracking thresholds. We have undertaken an upgrade cycle in 2011-2012 to re-optimize CHAMP to allow group-delay tracking on the faintest fringes possible. We describe our multi-pronged strategy using special dicroics, new piezo scanners, and our first attempts to explore CHARA J-band made possible by using special metrology-blocking laser filters. CHAMP can now be used with all the combiners at CHARA.

Additional Information

© 2012 SPIE. This work has been supported by the University of Michigan, the National Science Foundation (NSF-ST-0352723, 0707927, 0807577, 1108963) and NASA (NRA-NNG04GC00G). Thanks also to UM machinist Scott Webster, UM undergrad Phil Muirhead, former UM postdoctoral fellow David Berger, and the whole CHARA array team that makes science with MIRC/CHAMP possible.

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