Development of the low-frequency detectors for BICEP Array

23 Jul 2019, 17:45
1h 15m
Piazza Città di Lombardia (Milano)

Piazza Città di Lombardia


Piazza Città di Lombardia, 1, 20124 Milano MI
Poster Low Temperature Detector fabrication techniques and materials Poster session


Ms Cheng Zhang (Caltech)


The BICEP/Keck (BK) experiment aims to detect the imprint of primordial
gravitational waves in the Cosmic Microwave Background polarization,
which would be direct evidence of the inflation theory. While the
tensor-to-scalar ratio r has been constrained to be <0.06 at 95% c.l.,
further improvements on this upper limit are hindered by polarized
Galactic foreground emissions. The 30/40 GHz receiver of the BICEP Array
(BA), targeting to constrain the synchrotron foreground with
unprecedented accuracy within the BK sky patch, will be deployed at the
end of 2019. The receiver has a focal plane with 11 single-band detector
tiles and one dual-color tile with the newly designed broad-band planar
antenna. In this talk, I will show the full development path of the
30/40 GHz detectors from design to tests results. The low optical and
atmospheric loading at these frequencies requires our TES detectors to
have low saturation power in order to be photon-noise dominated. To
achieve that, we have explored new leg designs for low island-to-bath
thermal conductivity (G). To boost detector fabrication throughput, we
have moved from 4" to 6" wafers, which introduced new challenges in the
fabrication process, such as thickness uniformity across the tile. I
will discuss how we overcame these issues and will present the measured
detector parameters (G, Tc, Psat etc.) and optical performance
(responsivity, beam, spectra). I will present on-sky noise performance
estimates based on the lab measurements and will discuss the sensitivity
forecast for the constraints on synchrotron amplitude and spectral

Student (Ph.D., M.Sc. or B.Sc.) Y
Less than 5 years of experience since completion of Ph.D N

Primary authors

Presentation Materials