First polarised light with the NIKA camera

TL;DR

The paper demonstrates the successful use of the NIKA camera for measuring linear polarisation in the millimeter wavelength range, showcasing its performance in recent observational campaigns.

Contribution

It presents the first polarisation measurements with the NIKA camera, validating its capability for polarimetric observations at millimeter wavelengths.

Findings

Effective modulation of polarisation using a rotating Half Wave Plate.

Successful detection of polarisation signals at 150 and 260 GHz.

Validation of NIKA's performance in polarimetric observations.

Abstract

NIKA is a dual-band camera operating with 315 frequency multiplexed LEKIDs cooled at 100 mK. NIKA is designed to observe the sky in intensity and polarisation at 150 and 260 GHz from the IRAM 30-m telescope. It is a test-bench for the final NIKA2 camera. The incoming linear polarisation is modulated at four times the mechanical rotation frequency by a warm rotating multi-layer Half Wave Plate. Then, the signal is analysed by a wire grid and finally absorbed by the LEKIDs. The small time constant (< 1ms ) of the LEKID detectors combined with the modulation of the HWP enables the quasi-simultaneous measurement of the three Stokes parameters I, Q, U, representing linear polarisation. In this paper we present results of recent observational campaigns demonstrating the good performance of NIKA in detecting polarisation at mm wavelength.