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Paper: PeNCIL: A Wire Grid Polarimeter at 121.6 nm
Volume: 526, Solar Polarization Workshop 8
Page: 341
Authors: Landini, F.; Romoli, M.; Baccani, C.; Adam, G.; Dinescu, A.; Meneghin, A.; Scippa, A.; Pancrazzi, M.; Focardi, M.; Baglioni, R.; Landi Degl'Innocenti, E.
Abstract: The magnetic field in corona can be measured through the Hanle effect, which is the magnetic field induced modification of the linear polarization signals resulting from the scattering of anisotropic radiation. The H I Lyα 121.6 nm is the most intense emission line of the EUV coronal spectrum and is highly sensitive to the Hanle effect. Through the comparison between the measured and the expected polarization in this line it is possible to infer the magnetic field in corona. PeNCIL (Polarimetry with Nanowires for Coronal Imaging of Lyα) may constitute the ideal candidate to measure the linear polarization of the whole Lyα 121.6 nm corona. It is a transmitting polarimeter optimized for the Lyα 121.6 nm line, thought as part of an internally occulted coronagraph to be flown aboard a future small solar mission or a sounding rocket. It is a light device, completely free of mechanical moving parts, composed of a fixed MgF2 quarter wave retarder, a nano-wire grid polarizer (nano-WGP), and a MgF2 variable retarder modulated through a calibrated piezo-clamp (PCVR). The nano-WGP and the PCVR are the two main components of PeNCIL and represent a first-ever achievement in the history of technology development for VUV. This paper addresses the status of the project with particular emphasis on the design and manufacturing of the nano-WGP and PCVR.
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