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| EBEX (experiment) | |
|---|---|
| Name | EBEX |
| Acronym | EBEX |
| Type | Balloon-borne telescope |
| Operator | University of Minnesota, California Institute of Technology, Columbia University, University of British Columbia |
| Mission duration | 2012 flight campaign |
| Launch site | McMurdo Station |
EBEX (experiment) was a balloon-borne polarimeter designed to measure the polarization of the cosmic microwave background and search for signatures of primordial gravitational waves. The project was a collaboration among institutions such as the University of Minnesota, California Institute of Technology, Columbia University, and the University of British Columbia, and it executed long-duration stratospheric flights from McMurdo Station over Antarctica. EBEX combined technologies developed for experiments like BOOMERanG, BICEP and Planck to advance measurements relevant to inflationary cosmology and cosmic microwave background polarization.
EBEX was conceived as a follow-on to experiments including MAXIMA, Archeops, and WMAP to probe the polarization of the cosmic microwave background with high sensitivity. The team assembled researchers from universities and laboratories such as Jet Propulsion Laboratory, NASA, and the Kavli Institute for Cosmological Physics to design a balloon-borne platform capable of long-duration flights over the Antarctic polar vortex. The payload integrated detectors, cryogenics, optics, and attitude control systems with heritage from projects like Spider (balloon-borne experiment) and POLARBEAR.
EBEX targeted the measurement of the B-mode polarization pattern expected from tensor perturbations produced during cosmic inflation and aimed to constrain the tensor-to-scalar ratio r, a parameter central to models by researchers such as Alan Guth and Andrei Linde. Secondary objectives included characterization of polarized foreground emission from Galactic dust and magnetic fields, relating to studies by teams working on Planck (spacecraft) and IRAS. The mission sought to improve understanding of reionization history constraints used in analyses by groups at Princeton University and Harvard University.
The EBEX telescope used a Gregorian optical design feeding a focal plane of transition-edge sensor bolometers developed with fabrication facilities at institutions like NASA Goddard Space Flight Center and Argonne National Laboratory. The focal plane operated at sub-kelvin temperatures provided by closed-cycle cryogenics similar to systems used by Herschel Space Observatory and cryostats developed at University of Chicago. Polarimetry was achieved with a continuously rotating achromatic half-wave plate and wire-grid polarizers inspired by implementations in MAXIPOL and POLARBEAR. Readout of the detectors employed superconducting quantum interference device (SQUID) multiplexing techniques pioneered at National Institute of Standards and Technology and used by collaborations such as South Pole Telescope teams.
EBEX conducted engineering flights and a long-duration science campaign launched from McMurdo Station in Antarctica during the austral summer, relying on logistical support from United States Antarctic Program and coordination with British Antarctic Survey assets in the region. Flight operations integrated telemetry, attitude control, and pointing reconstruction systems with components adapted from COSMOSOMAS and flight-proven platforms like BOOMERanG. The team coordinated with airspace authorities and research stations including Scott Base for recovery and data retrieval.
Raw timestreams from the detector arrays underwent deglitching, demodulation, and mapmaking using software frameworks and algorithms developed in collaboration with groups at California Institute of Technology, University of Toronto, and McGill University. Analysis pipelines incorporated component separation methods comparable to those applied by the Planck Collaboration and foreground modeling approaches informed by studies at Max Planck Institute for Astrophysics and Harvard-Smithsonian Center for Astrophysics. Statistical inference for cosmological parameters used Markov chain Monte Carlo samplers and tools similar to those developed at Stanford University and University of Cambridge.
EBEX produced instrument characterization papers, foreground analyses, and upper limits on B-mode polarization that contributed to the community's understanding alongside measurements from BICEP2/Keck Array and POLARBEAR. Team publications appeared in journals frequented by collaborations including Physical Review D, The Astrophysical Journal, and Astronomy & Astrophysics, and were presented at conferences like the American Astronomical Society meetings and workshops hosted by SLAC National Accelerator Laboratory. The experiment reported advances in balloon-borne polarimetry techniques and detector performance benchmarks used by subsequent projects.
EBEX influenced the design of successor experiments and informed instrument choices for projects such as CMB-S4, LiteBIRD, and ground-based arrays including Simons Observatory. Technology developments from EBEX—TES arrays, SQUID multiplexing, rotating half-wave plates—were adopted by groups at University of California, Berkeley, Imperial College London, and national laboratories including Brookhaven National Laboratory. The collaboration fostered training for students and postdocs who joined teams at institutions like Princeton University, University of Chicago, and Oxford University, further contributing to the global effort to characterize primordial signals in the cosmic microwave background.
Category:Cosmic microwave background experiments Category:Balloon-borne telescopes Category:Astrophysics experiments