POLARBEAR-1

htt-dusk — POLARBEAR-1 observing the Cosmic Microwave Background from the Chajnantor Plateau at dusk. Photo credit: Simons Foundation

POLARBEAR-1 (PB1) was a Stage-2 cosmic microwave background (CMB) experiment located at the Chajnantor Observatory in the Atacama Desert of northeastern Chile and began observations in 2012. The project was led by Adrian Lee at UC Berkeley and was decommissioned in 2019.

pb1figure — A rapid-fire overview of the POLARBEAR-1 hardware. **Top right**: PB1 receiver cryostat, which is responsible for cooling the experiment and guiding the CMB light to the detectors. **Top left**: PB1 detector array which contains more than 600 pixels. **Bottom left**: Microscope photo of the PB1 detector pixel, which includes a dual-slot dipole antenna coupled to two transition-edge sensor (TES) bolometer detectors. **Bottom right**: Result of the PB1 first season dataset, which rejected the null hypothesis for B-modes with nearly 5-sigma significance! Figure credit: Zigmund Kermish, POLARBEAR Collaboration

The PB1 receiver contains more than 1,200 polarization-sensitive detectors that observe the sky via a three-meter-diameter telescope at 150 GHz. A PB1 detector pixel consists of a double-slot dipole antenna and two polarization-sensitive transition edge sensor (TES) bolometers. PB1 made the first ever statistically-significant, polarization-only, non-zero detection of the “B-mode” polarization pattern induced by distortion of the CMB by large-scale gravitational structure.

praweencharlie — Me standing in front of POLARBEAR-1 during my 2014 deployment to Chile. Photo credit: Praween Siritanasak

My contribution to PB1 was primarily telescope and site maintenance. During 2014 ~ 2016, I regularly babysat the experiment remotely using a custom web interface developed by Yuji Chinone, and I also visited Chile for 4 weeks in August of 2014 to perform a routine checkup and minor upgrades to site infrastructure.

For more information about PB1, visit its website!