Proc. of SPIE
Yuji Ikeda(GENESIA Corporation), Hiroshi Akitaya(Tohoku Univ.), Kentaro Matsuda(Tohiku Univ.), Koji S. Kawabata(NAOJ), Munezo Seki(Tohoku Univ.), Ryuko Hirata(Kyoto Univ.), and Akira Okazaki(Gunma Univ.)
We are developing a Cassegrain optical spectropolarimeter, LIPS.
LIPS employs an echelle-type spectrograph to get a high spectral resolution of R > 7,000. LIPS consists of three instrumental units, a polarimeter, a spectrometer, and a detector.
One serious problem was the appearance of 'spectral ripple' generated in the Pancharatnam type super-achromatic half-wave plate (PWP).
We found out through laboratory works and numerical simulations that the ripple is caused by the interference among layers in the half-wave plate.
In stead of PWP, we adopted a new type of super-achromatic half-wave plate composed of five polymethyl-methacrylate layers, which was manufactured by Astropribor Company in Ukraine.
This wave plate greatly reduces reflection at the boundaries among layers, which results in significant reduction of ripple.
Since the spring of 2001, we have carried out engineering observations with LIPS at IRS and UH88.
We conclude from these observations that LIPS have achieved the accuracy of δP < 0.1 %.