[P-EM15] Study of coupling processes in solar-terrestrial system

[PEM15-P10] Development of a narrow-band magneto-optical filter for daytime and thermospheric observations with a Na lidar at Tromsoe (3)

*Takuya Kawahara¹, Satonori Nozawa², Norihito Saito³, Takuo T. Tsuda⁴, Testuya Kawabata², Satoshi wada³, Toru Takahashi⁵ (1.Faculty of Engineering, Shinshu University, 2. ISEE, Nagoya University, 3.Center for Advanced Photonics, RIKEN, 4.University of Electro-Communications, 5.Electronic Navigation Research Institute)

Keywords:Na lidar, magneto-optical filter

An ultra-narrowband magneto-optical filter, also called a Faraday dispersive filter, is being developed for the Na LIDAR receiver in Tromsø to enable thermonspheric observations and daytime observations in sunlit conditions. The filter consists of a heated Na cell between two crossed polarizers in a strong magnetic field, producing a transmission profile.

Currently, the following stages of development are underway:
1. A new Faraday filter is being built for the new lidar receiver. Its transmission profiles are being measured at RIKEN with a high resolution of a few MHz under different cell temperatures with magnetic fields of 170 mT. The measured transmission profiles are being compared with theoretical ones for validation.
2. A new sapphire cell is being developed for LIDAR daytime measurements. Commercially available glass-type Na cells corrode at high temperatures of over 150°C due to chemically active high-temperature Na atoms in the cell.
3. A thermal stability test of the transmission profiles has been conducted, assuming long-term observation. The filter transmission during observation is required for data analysis, so the transmission needs to be measured between observations.

Discussions on these topics are presented in the talk.