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CIERA Astronomers Travel to Mexico to Install TolTEC Camera

Last November, the Chicagoland area prepared for a cold winter as CIERA astronomers Dennis Lee, Giles Novak and Marc Berthoud traveled off to warmer climates. Along with staff of Northwestern’s Research Shop, the trio was preparing to pay the Large Millimeter Telescope (LMT) a visit.

LMT against skyIn the state of Puebla, Mexico, the LMT looms over the 15,000 foot summit of Volcan Sierra Negra. The LMT is a binational project between Mexico and the US. It is the largest telescope in existence for observations at wavelengths near 1 millimeter, with its 50 meter diameter primary mirror. TolTEC is a powerful new camera for LMT developed by a collaboration including CIERA and six other institutions across three countries. At its heart are approximately 7000 novel Microwave Kinetic Inductance Detectors (MKIDS) cooled to 0.1 degrees above absolute zero. In collaboration with the staff of Northwestern’s Research Shop, Lee, Novak, and Berthoud developed the rapid-spinning half-wave plate polarization modulator that will allow TolTEC to “see” the state of linear polarization of the millimeter light and thereby reveal the magnetic fields of stellar nurseries. Some theories hold that these fields affect the masses of newborn stars as well as whether they form as single stars of as parts of a multiple system.

Novak and Lee worked at the LMT side by side for ten long days under difficult conditions. This included the thin air at 15,000 feet, the cold working areas – deliberately kept at ambient temperature to allow for thermal stabilization of the giant telescope’s support structure, the long daily drives up and down the mountain through remote areas, and the ever-present concerns about COVID. “But the close collaboration with talented scientists, engineers, and technical staff from Mexico was a wonderful experience that we look forward to repeating over the next few months as we work to finish the commissioning of the camera and polarimeter,” shared Novak. “Our dinners in Ciudad Serdán were another highlight of the trip. In particular, the area is famous for its Mole Poblano.”



By Gema Tinoco and Giles Novak