9 July 2018 Prototype design and evaluation of the nine-layer achromatic half-wave plate for the LiteBIRD low frequency telescope
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Abstract
LiteBIRD is a satellite project to measure the polarization of the CMB with an unprecedented accuracy. LiteBIRD observes all sky for three years at the sun-earth second Lagrange point. The goal of LiteBIRD is to observe the B-mode polarization at large angular scales and to measure the tensor-to-scaler ratio r with an accuracy less than 0.001, exploring the energy scale of the inflation. In order to mitigate the system 1/f noise and systematics, we plan to use continuous rotating half-wave plates (HWPs) as a polarization modulator at each aperture of two telescopes. One of the telescopes, called a low frequency telescope (LFT), covers the frequency range from 34 to 270 GHz, requiring the HWP to have a high modulation efficiency in the wide bandwidth. We employ a Pancharatnam-type achromatic HWP (AHWP) to achieve the broadband coverage. The AHWP consists of nine layer stacked HWPs with the optic axes mutually rotated by the angles optimized for the LFT bandwidth. In this paper, we report our development status of the nine layer AHWP and measurement results on the modulation efficiency and the phase as a function of frequency.
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Kunimoto Komatsu, Kunimoto Komatsu, Tomotake Matsumura, Tomotake Matsumura, Masashi Hazumi, Masashi Hazumi, Hiroaki Imada, Hiroaki Imada, Hirokazu Ishino, Hirokazu Ishino, Nobuhiko Katayama, Nobuhiko Katayama, Yuki Sakurai, Yuki Sakurai, Hajime Sugai, Hajime Sugai, Ryota Takaku, Ryota Takaku, "Prototype design and evaluation of the nine-layer achromatic half-wave plate for the LiteBIRD low frequency telescope ", Proc. SPIE 10708, Millimeter, Submillimeter, and Far-Infrared Detectors and Instrumentation for Astronomy IX, 1070847 (9 July 2018); doi: 10.1117/12.2312431; https://doi.org/10.1117/12.2312431
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